Journal Of Materials Chemistry Research Articles

Uniform Zinc Plating Enabled By Polyimide Nanofiber Network for Long-Life Aqueous Zinc Metal Batteries

The rapid development of portable electronics and emerging electric vehicles has created a pressing need for electrical energy storage systems. Among these systems, zinc metal batteries (ZMBs) have shown great potential due to their high theoretical capacity density, low reduction potential, and low-cost anodes. However, the large-scale application of rechargeable ZMBs has been limited by the well-known issues of dendrite growth and adverse side reactions in zinc metal electrodes[1].Various strategies have been proposed to overcome the challenges associated with zinc dendrite growth, including substrate structure optimization, surface modification of zinc metal, and design of novel electrolytes. Among these approaches, constructing a protective layer on the zinc anode surface is a promising strategy due to its simplicity and cost-effectiveness. A dense polyamide coating layer, prepared by the doctor blading method, has been developed to regulate the aqueous Zn deposition behavior by elevating the nucleation barrier and restricting the 2D diffusion of Zn2+ ions [2]. Additionally, an Al2O3 coating layer has been developed using atomic layer deposition to improve the rechargeability of Zn anodes for zinc-ion batteries (ZIBs)[3]. However, these dense layers face a significant challenge to ionic conductivity due to the high energy barrier that hinders the diffusion of Zn2+ ions, leading to poor battery performance, especially under high current densities.Herein, we report utilizing an electrospun polyimide network (noted as PI-Zn hereafter) to resolve this dilemma. The polyimide (PI) chain has numerous carbonyl oxygen atoms that function as electron donors, supported by theoretical calculations (Fig.1). These atoms can establish stable bonds with Zn ions, thereby reducing the activation energy for de-solvation and enhancing the kinetics of Zn ion deposition. Unlike traditional coating methods, our electrospinning polymers form a fiber-like network structure that provides ion channels, thereby enhancing ion transportation. From the Nyquist plots of symmetrical batteries (Fig. 2), the PI-Zn electrode exhibits smaller charge transfer resistance and lower activation energy compared to the bare Zn electrode. The Transmission X-Ray Microscope results (Fig.3) reveal that the deposition on the bare Zn is heterogeneous and dendritic. In contrast, the PI-Zn electrode presented a smooth surface and dendrite-free morphology. The result demonstrates that the charge transfer ability, de-solvation, and deposition kinetics have been improved by PI-Zn, which further increases the plating uniformity.The stability of the Zn anode was evaluated by long-term galvanostatic cycling of a symmetrical Zn cell (Fig. 4). The cell with bare Zn failed after cycling for 100 h at a current density of 1 mA cm-2 resulting from the short circuit. In comparison, the cell with PI-Zn exhibits a stable polarization voltage and an ultralong cycling life of over 1200 hours, indicating the extremely reversible plating/stripping enabled by the PI network. Further interrogation of the PI-Zn was carried out by stringent deep-discharge tests in symmetrical Zn cells under extremely high current density and capacity of 20 mA cm-2 and 10 mA h cm-2. The result shows that the cell with PI-Zn can cycle for more than 200 hours, two times longer than that with bare Zn, proving the advantages of the unique fiber-like network structure, which provides fast and homogeneous Zn ion transportation. Moreover, the fiber network effectively suppresses the hydrogen evolution reaction, verified by the corrosion test, despite the existence of numerous ion channels.Full prototype cells were assembled to prove the practical applications of our strategy. Two promising cathodes for aqueous ZIBs, MnVOH and MnO2, in two different electrolyte systems (Zn(OTf)2 and ZnSO4) were coupled with bare Zn or PI-Zn. For both systems, the capacity retention and Coulombic efficiency are both significantly improved with the help of PI network. The results are consistent with the lifespan difference of symmetrical Zn cells, as expected due to the same plating and stripping processes on Zn. These findings demonstrate that the strategy presented here stands to both dramatically extend battery cycle life and boost battery performance, a promising approach to solve the anode issues in advanced Zn batteries. Cao, Z., et al., Advanced Energy Materials, 2020. 10(30): p. 2001599. Zhao, Z., et al., Energy & Environmental Science, 2019. 12(6): p. 1938-1949. He, H., et al., Journal of materials chemistry A, 2020. 8(16): p. 7836-7846. Figure 1

Silver-M-Phathalocyanine (M= Co,Fe,Cu) Electrocatalysts for Oxygen Reduction Reaction in H2/O2 Anion Exchange Membrane Fuel Cells

In the transition from fossil fuels to clean energy sources, H2 plays a key role due to its high energy density, and direct conversion to electricity in fuel cells (FCs). FCs are devices that allow the clean conversion of chemical energy into electrical energy. In H2/O2 fuel cell the hydrogen oxidation reaction (HOR) occurs at the anodic electrode, while at the cathodic side oxygen is reduced into water (ORR). The electrodes are separated by a conductive membrane, that could exchange protons (Proton Exchange Membrane, PEM) or anions (Anion Exchange Membrane, AEM) to maintain the electro-neutrality of the system. AEMFCs are an attractive alternative to PEMFCs, thanks to the alkaline noncorrosive enviroment that allows the use of cheaper structural materials such as non-noble metal electrocatalysts. This work is centred on the study of silver (Ag) nanostructured electrocatalysts in ORR for the realization of a platinum-free AEMFCs. Ag nanoparticles promote, in alkaline media, a 4e- pathway of the ORR, optimizing the conversion of oxygen into water at the expense of hydrogen peroxide.1 However, the activity of Ag is limited by the strong hydroxide anion (OH-) binding energy, which reduces the free active sites destined to oxygen adsorption.1 To overcome this, Ag electrocatalysts were modified with metal-phthalocyanines (M-Pc M=Co, Fe, Cu) and supported on Ketjen-black carbon and on Ceria/Ketjen black (CeO2/C) supports. The synergistic effect between M-Pc and Ag NPs optimizes the OH- binding energy enhancing the ORR performances.2,3 The employment of ceria, thanks to its high oxophylicity, improves the transfer of OH- to the metal surface.4,5 The dispersion and size of nanoparticles (5-15 nm) was controlled through the Turkevich synthesis method, in order to maximize the interaction between Ag and Me-Pc. Physical characterization has been realized by High Resolution Trasmission Electron Microscopy (HR-TEM), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) while electrochemical behaviour has been explored in half cells and in complete AEMFCs. References Erikson, H., Sarapuu, A., & Tammeveski, K. (2019). Oxygen reduction reaction on silver catalysts in alkaline media: a minireview. ChemElectroChem, 6(1), 73-86.. Miller, H. A., Bevilacqua, M., Filippi, J., Lavacchi, A., Marchionni, A., Marelli, M., ... & Vizza, F. (2013). Nanostructured Fe–Ag electrocatalysts for the oxygen reduction reaction in alkaline media. Journal of Materials Chemistry A, 1(42), 13337-13347. Miller, H. A., Bellini, M., Oberhauser, W., Deng, X., Chen, H., He, Q., ... & Vizza, F. (2016). Heat treated carbon supported iron (ii) phthalocyanine oxygen reduction catalysts: elucidation of the structure–activity relationship using X-ray absorption spectroscopy. Physical Chemistry Chemical Physics, 18(48), 33142-33151. Miller, H. A., Bellini, M., Dekel, D. R., & Vizza, F. (2022). Recent developments in Pd-CeO2 nano-composite electrocatalysts for anodic reactions in anion exchange membrane fuel cells. Electrochemistry Communications, 135, 107219. Bellini, M., Pagliaro, M. V., Marchionni, A., Filippi, J., Miller, H. A., Bevilacqua, M., ... & Vizza, F. (2021). Hydrogen and chemicals from alcohols through electrochemical reforming by Pd-CeO2/C electrocatalyst. Inorganica Chimica Acta, 518, 120245. Figure 1

Understanding the Drying Process and Mud Cracking of Li-Ion Battery Electrodes through Synchrotron X-Ray Computed Tomography

The drying process of slurry cast Li-ion battery electrodes is a subject with significant impacts on the performance of the battery but where detailed understanding is lacking(1). Mud cracking, opening of cracks in the surface due to stress from the slurry shrinking as it dries, is the most dramatic phenomenon during the process. Cracks may be detrimental to electrode performance due to delamination, which makes sections of the electrode unusable, or generally poor electrode cohesion. However, cracks could provide channels for ion transport to deeper levels of the electrode, similar to templated electrodes (2) but without the extra manufacturing steps. Cracking is prominent in thick (3-5) or water processed electrodes (3), which are desirable for greater energy density and replacement of the toxic solvent N-methyl pyrrolidone (NMP), respectively. Thus, understanding mud cracking during drying can lead to more energy dense (thicker), greener (without toxic NMP), and better performing electrodes (fast charging).Li-ion electrodes are industrially produced by casting a slurry on a metal foil current collector by a slot die or doctor blade method in a roll-to-roll machine. In the case of the positive electrode this slurry typically contains active metal oxide (e.g. LiNiMnCoO2, LiNi0.6Mn0.2Co0.2O2) particles, polyvinylidene fluoride (PVDF) binder, and carbon black. Drying is composed of three stages illustrated in Fig. 1 a-d, with the binder, carbon black settling and migrating at random (1),(6, 7). Crack formation is thought to occur during the third stage when capillary forces cause stress in the drying slurry opening cracks as solvent menisci form between particles. However, the process of crack nucleation and their 3-dimensional growth has never been directly observed in-situ(1),(4). X-ray computed tomography (Fig. 1 f-j) is able to show the morphology of cracks in an electrode and can be used to characterize properties like delamination, crack volume, crack network connectedness or crack network tortuosity, which can be linked to electrode performance. However, to understand how these crack networks form requires observation of the time evolution of the cracks and the movement of active material particles near the cracks, which requires fast measurements. Here, we present synchrotron x-ray computed tomography of drying electrode which enable the fast measurements required and allows us to more fully explain mud cracking in drying electrodes, and the drying process in general.References Y. S. Zhang, N. E. Courtier, Z. Zhang, K. Liu, J. J. Bailey, A. M. Boyce, G. Richardson, P. R. Shearing, E. Kendrick and D. J. L. Brett, Advanced Energy Materials, 2102233 (2021). C. Huang, M. Dontigny, K. Zaghib and P. S. Grant, Journal of Materials Chemistry A, 7, 21421 (2019). Z. Du, K. M. Rollag, J. Li, S. J. An, M. Wood, Y. Sheng, P. P. Mukherjee, C. Daniel and D. L. Wood, Journal of Power Sources, 354, 200 (2017). B. Lu, C. Ning, D. Shi, Y. Zhao and J. Zhang, Chinese Physics B, 29, 026201 (2020). R. Sahore, D. L. Wood, A. Kukay, K. M. Grady, J. Li and I. Belharouak, ACS Sustainable Chemistry & Engineering, 8, 3162 (2020). S. Jaiser, L. Funk, M. Baunach, P. Scharfer and W. Schabel, Journal of Colloid and Interface Science, 494, 22 (2017). Y. S. Zhang, A. N. Pallipurath Radhakrishnan, J. B. Robinson, R. E. Owen, T. G. Tranter, E. Kendrick, P. R. Shearing and D. J. Brett, ACS Applied Materials & Interfaces, 13, 36605 (2021). Figure 1

Multimodal Characterization of Nucleation and Progression of Interfacial Degradation in All Solid-State Batteries

We face an immediate need for more energy-dense batteries that are stable over long-term cycling, to address the increased electrification of the transportation sector. All-solid state batteries (ASSBs) that combine a solid-state electrolyte with a Li metal anode offer the potential to achieve this objective by replacing intercalation anodes such as graphite with Li metal. However, interfacial degradation at the Li | solid electrolyte interface currently compromises the safety and cycling stability of ASSBs [1]. This interfacial degradation is usually a combination of instabilities of mechanical, chemical or electrochemical origin. This in turn compromises the structural and morphological stability of ASSBs over cycling, causing them to fail in fewer cycles than required for implementation as next-generation batteries in automobiles [2]. Thus, in order to improve their cycling stability, the understanding of the origin and nature of these interfacial instabilities needs to be multimodal, to understand the interplay between the different degradation mechanisms. Argyrodite (Li6PS5Cl) is a particularly attractive solid-state electrolyte (SSE) due to a high ionic conductivity (comparable to liquid electrolytes), as well as potential for batch processing [3]. However, its brittle nature and chemical composition makes it susceptible to cracking and deleterious side reactions, which hamper its stability. This work will focus on elucidating the effect of (1) current density and (2) processing conditions on the cycling stability of Li | LPSCl | Li ASSBs.We use 4-D XRD-CT (X-ray diffraction computed tomography) combined with phase contrast micro-computed tomography (μCT) to conduct the multimodal investigation of interfacial degradation, under pseudo operando conditions. The methodology is to obtain a 3-D XRDCT scan around the interface in a particular cycled condition, followed by a higher-resolution 3D μCT scan on the same region. This sequence is repeated after every stripping/plating cycle, starting from the pristine cell up to cell failure. These experiments are conducted at a synchrotron source, to enable the acquisition at high spatial resolution (~5 μm) over large volumes (~mm3), in a reasonable amount of time. A standard swagelok-style cell is used for repeatability of results and optimal geometry for conducting tomography. XRD-CT can furnish quantitative phase maps of all phases (argyrodite and reaction by-products), as well as the elastic strain in the sample. The μCT on the other hand gives information on the evolution of morphology around the interface with cycling (cracks/voids). Thus, by correlating the two datasets together over cycling, we are able to connect mechanical instabilities to the chemical/electrochemical instabilities.Here, we focus on varying two specific processing parameters for argyrodite: the sintering temperature and pressure, and studying their effect on nucleation and propagation of interfacial instabilities over repeated cycling. Through cycling, we track the evolution of cracks/voids, chemical by-products such as LiCl, Li3P and Li2S using XRD-CT and μCT. Finally, we track the filling of metallic Li into certain cracks in dendritic form, which leads to shorting and failure of the cell. We find that both of these parameters heavily influence the behavior of the interface, with cells failing between 4-20 cycles, and a marked difference in how the degradation initiates and propagates. Finally, for the processing condition that shows the best cycling behavior, we do a C-rate study, by increasing the current density for plating/stripping with each cycle up to failure. This discusses the utility of a parameter such as critical current density for a cell, where the local current densities are very heterogeneous and different from the global current reading while cycling.We envisage these results being used as inputs into modeling studies to optimize strategies for interfacial stabilization in ASSBs going forward.[1] Paul, P. P. et al. Interfaces in all solid state Li-metal batteries: a review on instabilities, stabilization strategies, and scalability. Energy Storage Materials 2022, 45, 969-1001.[2] Hao, S. et al. Tracking lithium penetration in solid electrolytes in 3D by in-situ synchrotron X-ray computed tomography. Nano Energy 2021, 82, 105744.[3] Chen, Y-T. et al., Investigating dry room compatibility of sulfide solid-state electrolytes for scalable manufacturing, Journal of Materials Chemistry A 2022, 10, 7155-7164.

Strontium Vanadate Deposited by ALD: Toward a New Synthesis Approach

Transparent conductive oxides (TCOs) have a wide range of potential applications in fields such as photovoltaics, touch screens, and smart windows. The challenging task when developing conventional TCOs like tin-doped indium oxide (ITO) by the traditional method is to make them more conducting by increasing the concentration of charge carriers without compromising the optical transparency [1]. Another novel approach involves increasing the plasma energy to widen the transparency window by increasing the charge carriers' effective mass. This approach has led to growing interest in perovskite transition metal oxides such as CaVO3 and SrVO3 due to their strong electronic correlation, which results in plasma energy shifting to higher energies than classical TCOs [2,3]. However, obtaining a crystallized film in the perovskite SrVO3 phase for optimal electrical conduction and optical transparency is challenging, particularly at low growth temperatures and when deposited on amorphous substrates like glasses [2, 4].As a result, atomic layer deposition (ALD) has emerged as a promising technique for depositing conformal layers on large surfaces with high aspect ratios and low thermal budgets. In this study, we investigated the deposition of strontium vanadium oxide films by ALD using vanadium tri-isopropoxide (VTIP) as the vanadium precursor, strontium bis(isopropylcyclopentadienyl) (Sr(iPr3Cp)2) from Air Liquide company as the strontium precursor, and water as a reagent, respectively. We deposited SrVO3 films on (100) Silicon and glass substrates at 240°C and annealed them under forming gas (95% Ar, 5% H2) at 500°C for one hour. We paid particular attention to the deposition of an anatase TiO2 buffer layer to promote the crystallization of SVO.The unannealed films were found to be completely amorphous whatever the substrate, and regardless of the presence or not of the TiO2 crystallized buffer. The EDX, STEM-HAADF and SIMS analyses revealed that the buffer is a key element to avoid the Si diffusion in SVO layer, before, and even more upon annealing. The annealed samples with a buffer layer deposited on both substrates were crystallized into various SrxVyOz phases according to the Sr amount, controlled by the Sr cycles ratio (RSR) (figure). The XRD data allowed the identification of the Sr3VO8 and Sr2VO4 phases, where the last one favors the higher Sr amount. The influence of the substrate is significant and discussed. Furthermore, we characterized the films' optical properties using spectroscopic ellipsometry in the UV-visible range. We analyzed the refractive index and extinction coefficient behavior according to the Sr amount and evaluated the effect of annealing. We estimated the band gap energy using Tauc-Lorentz and Tauc plot models and discussed it in relation to the Sr amount and the obtained phases.Our study provides not only valuable insights into the deposition and characterization of SrVO3 thin films for potential TCO applications, but also on Sr3VO8 and Sr2VO4 phases, which may be of interest for their transparent oxide optical properties. New ALD growth strategies to improve the SrVO3 phases will be presented as a perspective of this study and as an example of using different V precursor or reactive atmospheres during ALD process.[1] S.C. Dixon, D.O. Scanlon, C.J. Carmalt, I.P. Parkin, "n-Type doped transparent conducting binary oxides: an overview", Journal of Materials Chemistry C, 4, 29 (2016), pp. 6946-6961[2] Zhang, Lei, et al. "Correlated metals as transparent conductors." Nature materials 15.2 (2016): 204-210.[3] Boileau, Alexis, et al. "Highly Transparent and Conductive Indium‐Free Vanadates Crystallized at Reduced Temperature on Glass Using a 2D Transparent Nanosheet Seed Layer." Advanced Functional Materials 32.5 (2022): 2108047.[4] A. Boileau, A. Cheikh, A. Fouchet, A. David, C. Labbé, P. Marie, F. Gourbilleau, U. Lüders, "Tuning of the optical properties of the transparent conducting oxide SrVO3 by electronic correlations", Advanced Optical Materials, 7, 7 (2019), pp. 1801516 Figure 1

Synthesis of Ir Nanoparticles As Promoters for the Stabilization of Fenc-Catalysts Under Ssc Conditions

Fuel cells are promising devices for implementation in automotive propulsion. While the standard operation seems feasible, during start-up and shutdown high potentials occur on the cathodic site induced by the reverse current mode. In consequence, the carbon oxidation reaction (COR) occurs and limits the lifetime of PEMFCs. One approach suppressing carbon corrosion is the introduction of small amounts of an oxygen evolution reaction (OER) catalyst, as e.g. iridium. In our recent work we showed that in relative manner the durability was improved, however, the initial performance was less compared to the non-modified FeNC catalyst.[1 ] These NP had been prepared by a polyol approach.[2 ] However, capping agents (CA) could eventually still be present in these systems, blocking the particles in their performance.Herein, we present our results using an alternative surfactant free synthesis of Ir nanoparticles, adapted from literature,[3 ] that are then used for the modification of an FeNC catalysts. The performance of the newly prepared FeNC+Ir vs the FeNC+Ir+CA reference was evaluated employing accelerated stress tests mimicking the start-up and shut down conditions in RDE and PEMFC. It is shown that with this new approach the amount of NP on the surface can be better controlled. Beside the electrochemical testing structural characterization by X-ray-diffraction, thermogravimetric analysis and transmission-electron-microscopy was performed.It will be shown that by surfactant free synthesis Ir nanoparticles with high purity can be obtained. Due to the higher purity, an improvement of the OER activity can be achieved with the same Ir loading. In the RDE, an improvement in stability was observed by loading an FeNC catalyst with Ir nanoparticles. However, under fuel cell conditions, no improvement in stability was observed by loading Ir nanoparticles onto a FeNC catalyst.List of references[1] Prössl, C., Kübler, M., Paul, S., Ni, L., Kinkelin, S. J., Heppe, N., Eberhardt, K., Geppert, C., Jaegermann, W., Stark, R. W., Bron, M. & Kramm, U. I. (2022). Impact of Ir modification on the durability of FeNC catalysts under start-up and shutdown cycle conditions. Journal of Materials Chemistry A, 10(11), 6038-6053.[2] Prössl, C., Kübler, M., Nowroozi, M. A., Paul, S., Clemens, O., & Kramm, U. I. (2021). Investigation of the thermal removal steps of capping agents in the synthesis of bimetallic iridium-based catalysts for the ethanol oxidation reaction. Physical Chemistry Chemical Physics, 23(1), 563-573.[3] Bizzotto, F., Quinson, J., Schröder, J., Zana, A., & Arenz, M. (2021). Surfactant-free colloidal strategies for highly dispersed and active supported IrO2 catalysts: Synthesis and performance evaluation for the oxygen evolution reaction. Journal of catalysis, 401, 54-62.

Minimizing Coke Formation at La0.3Ca0.7Fe0.7Cr0.3O3-δ Perovskite Anodes in a Syngas Fed-SOFC

As the world moves to decarbonize the fossil fuel sector, transition technologies are needed that bridge the gap between natural gas power plants and more sustainable low-carbon energy sources. These newer technologies often still rely on fossil fuels but have improved energy conversion efficiencies and lower net carbon dioxide (CO2) outputs over conventional fossil fuel based electric power generation systems. In this work, we are exploring one such technology, namely the use of a syngas-fed solid oxide fuel cell (SOFC) to generate heat, electricity, steam, and captured CO2. Core to this technology is the mixed ion electron conductor deployed at the anode and cathode that catalyzes all of the relevant reactions, namely electrochemical oxidation of hydrogen (H2) and carbon monoxide (CO) at the anode, producing steam and CO2, and reduction of oxygen at the cathode.Carbon formation (coking) is normally a significant problem affecting SOFCs operating on carbon-based fuels, as it leads to a rapid decline in electrochemical performance by blocking catalytically active sites and pores with various carbon species, e.g., amorphous, graphitic, or nanotubular carbon.1 The formation of carbon species from syngas is known to occur through various mechanisms, with the Boudouard reaction (∆H= -172 kJ/mol) and the reduction of CO (∆H= -131 kJ/mol) being the most prominent.2 As such, temperature is a key parameter to optimize as it determines the propensity for carbon formation at equilibrium. In addition, the kinetics of carbon formation can be significantly reduced by introducing oxygen to the fuel gas stream in the form of O2, CO2, or H2O.3 The catalyst materials investigated here are mixed conducting perovskite oxides (La0.3Ca0.7Fe0.7Cr0.3O3- δ, LCFCr) that have been optimized and modified recently by our group, both in the as-prepared undoped form and after B-site doping with variable quantities of transition metals (M), e.g., Ni,4 forming nanoparticle (NP)-decorated ABO3-Mx surfaces. Our catalyst is highly active for H2 and CO oxidation, CO2 reduction, and O2 reduction, where it was demonstrated that the un-doped parent material can deliver a stable power density of 0.2 W/cm2 for several hundred hours with negligible performance degradation in 3% humidified H2.5 In more recent work, excellent resilience to carbon deposition for exsolved Fe-Ni@LCFCr up to 70:30 CO:CO2 was demonstrated.4 Herein, we show that minimal coke forms during exposure of these materials to dry syngas at 600oC, even under open circuit conditions.The catalysts were prepared using combustion synthesis and were characterized by XRD, SEM EDX, and TPO-MS in order to confirm morphology, crystal structure, and composition as a function of temperature and gas environment.4 Symmetrical electrolyte-supported SOFCs were constructed using our catalyst as both the anode and cathode. Catalyst layers of 1 cm2 were screen printed to a thickness of 25 µm on both sides of commercially available 130 µm thick samaria-doped ceria (SDC)-buffered scandia-stabilized zirconia (ScSZ) electrolyte, followed by sintering at 1100°C for 2 h,4 with porous metal current collectors used. The cells were mounted and tested in a Fiaxel SOFC test station with gas flow controlled by mass flow controllers.Preliminary electrochemistry experiments were conducted in 5:95 H2:N2, or 1:1 H2:CO (syngas) balanced by CO2 in a 1:2 ratio of fuel to oxidant into the anode chamber, and air into the cathode chamber at 600 oC, with performance evaluation carried out using CV, EIS and chronopotentiometry. The power density was found to be ca. 2x higher in dry H2 vs. in syngas, as expected, considering that H2 is a more active fuel vs. CO. Additionally, EIS exhibited ca. 2x higher resistance in the low frequency arc in syngas, which can be attributed to sluggish CO oxidation kinetics.4 Chronopotentiometry was performed for 20 h at 10 mA cm-2, showing a degradation rate of only 0.08 mV h-1, suspected to be primarily due to current collector delamination. Coking studies were also conducted on button cells at 600 oC in 1:1 H2:CO for 25 h at open circuit, comparing to a NiO standard that was painted on the electrolyte just next to the LCFCr-Ni working electrode. Imaging by SEM showed negligible carbon formation on the perovskite surface, supported by EDX analysis, compared to the extensive degree of coking observed at the standard. Further quantification was conducted by TPO-MS, also confirming minimal carbon formation. References Bengaard et al., Journal of Catalysis, 2002, 209, 365–384.Farshchi Tabrizi et al., Energy Conversion and Management, 2015, 103, 1065–1077.Sasaki et al., Journal of The Electrochemical Society, 2003, 150.Ansari et al., Journal of Materials Chemistry A, 2022, 10, 2280–2294.Addo et al., ECS Transactions, 2015, 66, 219–228.

Investigation of Pd Based Metal-Carbon As Bifunctional Electrocatalyst for OER and ORR

Developing oxygen reduction/ evolution reaction (ORR/OER) bifunctional electrocatalysts has great significance for promoting the sustainable energy conversion. Herein, Pd (5wt% only) based bimetallic catalyst adhered well on heteroatom doped conducting carbon substrate is designed and constructed. Rich defects, multiple active centers and strong synergistic effect with rapid ion/electron transport ability allow the electrocatalyst to exhibit superior performance (Li et al., 2019). Owing to its more active metal-Pd sites due to high surface area conducting carbon matrix an ultralow overpotential of 240 mV at 10 mA/cm2 for OER was obtained. It outperforms state of art RuO2 and Pt/C electrocatalyst. High half-wave potential (E1/2) of 0.821 V for ORR is comparable to commercial Pt/C (E1/2 =0.819 V) electrocatalysts was attained. The catalyst exhibits a prolonged stability in alkaline medium at 20 mA cm-2 for 24 h for OER and a small 20 mV shift in linear sweep voltammetry scan after accelerated durability test for 5000 cycles at 50mV/s for ORR. In-situ Raman analysis exhibits surface oxidation of electrocatalyst on OER in highly alkaline (1M KOH) conditions.Reference:Li, S., Hao, X., Abudula, A., & Guan, G. (2019). Nanostructured Co-based bifunctional electrocatalysts for energy conversion and storage: current status and perspectives. Journal of Materials Chemistry A, 7(32), 18674–18707. https://doi.org/10.1039/C9TA04949E

Interface Induced Fast Ion Conduction in Complex Hydride/Oxide Nanocomposites: Interplay between Hydride and Oxide Properties

Solid-state electrolytes are crucial for next generation batteries with high energy density, long lasting and improved safety. The compatibility of most solid electrolytes with metallic anodes such as Li and Na metals, and cathodes such as sulfur, makes them suitable for high-capacity batteries (e.g., Li-S). They also address the safety concerns of current batteries by eliminating the flammable organic solvents in liquid electrolytes and by preventing/limiting dendrite formation. The lithium and sodium containing complex metal hydrides (e.g., LiBH4, NaBH4, LiCB11H12) have recently gained attention as solid-state electrolyte. They show high ionic conductivities but only at elevated temperatures (typically above 110 °C). Extending the high ionic conductivities to ambient temperatures is pivotal to the application of this fascinating class of solid electrolytes [1]. In this contribution, we will use LiBH4 and NaBH4 as examples to show that the ionic conductivities of complex hydrides can be greatly enhanced through interface effects resulting from the formation of nanocomposites with metal oxides. This strategy can lead to several orders of magnitude increase in the room temperature ionic conductivity [2]. Using DSC, DRIFT, solid-state NMR, and XRS (Xray Raman scattering), I will discuss how nanocomposite formation and presence of interfaces modifies either the phase stability, the defect concentration and/or leads to the formation of tertiary phase, and thereby increase profoundly the ion mobility of the complex hydrides. Systematic studies with different oxide nanoscaffolds and surface modified metal oxides, reveal that these effects can be optimized by tuning/engineering the nanostructure and interfaces in the nanocomposites. [3-4]. We will show that the effects also depend on a complex interplay between the stability of the metal hydride and surface properties of the metal oxide. Finally, the performance of some of the nanocomposite electrolytes in all-solid-state batteries, will be highlighted [5] References [1] L.M de Kort, P. Ngene et al. J. Journal of Alloys and Compounds 901 (2022) 163474[2] D. Blanchard et al., Advanced Functional Material. 25 (2015), 182.[3] P. Ngene et al. Physical Chemistry Chemical Physics 21 (40), 22456-22466[4] L.M de Kort, P. Ngene et al. Journal of Materials Chemistry A 8.39 (2020): 20687-20697[5] D. Blanchard et al, J. Electrochem. Soc. (2016).

Selection of Electrolyte Additives for Enhanced Mg-Air Battery Performance Supported By Data-Driven Approach

A Mg-air battery is a primary aqueous battery with high theoretical voltage and specific energy density. They have attracted much attention due to their high theoretical energy density, long shelf life, and safety. They consist of magnesium anode coupled to an air electrode. However, the performance of aqueous Mg-air batteries is relatively poor due to: a large overvoltage caused by formation of insoluble discharge products (MgO and Mg(OH)2); and fast self-corrosion of Mg anodes in aqueous electrolytes. Two main strategies have been developed to address these shortcomings – alloy development [1, 2] and electrolyte modification [3, 4]. Electrolyte additives are an effective way to control interfacial processes. They are inexpensive and straightforward methods for controlling self-corrosion of Mg. As was previously shown electrolyte additives can also improve the discharge performance of aqueous primary Mg-air batteries by changing the surface of Mg anode.Here, we investigated the mechanism of action of several Mg2+ complexing agents as electrolyte additives for aqueous Mg-air batteries [5, 6]. Electrochemical impedance spectroscopy (EIS) measurements during discharge and real-time hydrogen evolution measurements were used to elucidate the mechanisms of action. We found that Mg2+ complexing agents at optimal concentration greatly slowed the formation of insoluble discharge products and decreased the voltage drop in Mg-air batteries. Additionally, anodic hydrogen evolution experiments quantified the effect of Mg2+ complexing agents on self-corrosion of the Mg anode during discharge. These results suggest that Mg2+ complexing agents increase the battery utilization efficiency by inhibiting self-corrosion and decreasing the non-uniform dissolution of the Mg anode. This work showcases the promise of computer-assisted methods for rapidly and efficiently screen large numbers of organic compounds as potential electrolyte additives. Two data-driven quantitative structure-property relationship (QSPR) machine learning models were trained and used for in silico searches for promising battery performance-boosting candidates [7].[1] M. Deng, D. Höche, S.V. Lamaka, D. Snihirova, M.L. Zheludkevich, Mg-Ca binary alloys as anodes for primary Mg-air batteries, J. Power Sources, 396 (2018) 109-118.[2] M. Deng, L. Wang, D. Höche, S.V. Lamaka, P. Jiang, D. Snihirova, N. Scharnagl, M.L. Zheludkevich, Ca/In micro alloying as a novel strategy to simultaneously enhance power and energy density of primary Mg-air batteries from anode aspect, Journal of Power Sources, 472 (2020) 228528.[3] D. Höche, S.V. Lamaka, B. Vaghefinazari, T. Braun, R.P. Petrauskas, M. Fichtner, M.L. Zheludkevich, Performance boost for primary magnesium cells using iron complexing agents as electrolyte additives, Scientific Reports, 8 (2018) 7578.[4] B. Vaghefinazari, D. Höche, S.V. Lamaka, D. Snihirova, M.L. Zheludkevich, Tailoring the Mg-air primary battery performance using strong complexing agents as electrolyte additives, J. Power Sources, 453 (2020) 227880.[5] D. Snihirova, L. Wang, S.V. Lamaka, C. Wang, M. Deng, B. Vaghefinazari, D. Höche, M.L. Zheludkevich, Synergistic Mixture of Electrolyte Additives: A Route to a High-Efficiency Mg-Air Battery, Journal of Physical Chemistry Letters, (2020) 8790-8798.[6] L. Wang, D. Snihirova, M. Deng, B. Vaghefinazari, D. Höche, S.V. Lamaka, M.L. Zheludkevich, Enhancement of discharge performance for aqueous Mg-air batteries in 2,6-dihydroxybenzoate-containing electrolyte, Chem. Eng. J., (2021) 132369.[7] T. Würger, L. Wang, D. Snihirova, M. Deng, S.V. Lamaka, D.A. Winkler, D. Höche, M.L. Zheludkevich, R.H. Meißner, C. Feiler, Data-driven selection of electrolyte additives for aqueous magnesium batteries, Journal of Materials Chemistry A, 10 (2022) 21672-21682.

High-Capacity Nickel-Based Layered Oxides Containing Niobium Ions for Lithium-Ion Batteries

Lithium-ion batteries have been widely used in recent years, from portable electronic devices to electric vehicles. Although LiNiO2, is expected to be ideal electrode materials for electric vehicle applications due to its high reversible capacity, Ni ions migrate from octahedral sites of transition metal layers to tetrahedral sites of adjacent Li layers during charging. This process is partly reversible process but Ni ions are left the tetrahedral sites of the Li layer after the continuous cycle test, which prevents the re-insertion of Li ions, resulting in capacity degradation. [1]To suppress the capacity degradation LiNiO2, the effect on the phase transition behavior by Nb substitution for Ni ions in LiNiO2 is examined.The samples with different Nb contents LixNi1–xNbxO2, are synthesized and tested as electrode materials. The Nb-substituted sample shows highly improved cycle characteristics compared with non-substituted LiNiO2. SEM observation of the samples reveals that the primary particles become smaller, suggesting that the Nb-substituted influences the crystallization process for LiNiO2. By comparing the results of electrochemical and structural characterizations for the samples with or without Nb substitution, the origin of the improvement of electrode reversibility is discussed in details.Reference [1] N. Ikeda et al., and N. Yabuuchi, Journal of Materials Chemistry A, 9, 15963 (2021).

Computational Investigation of the Potential SOFC Air Electrode YSr2Cu2FeO8-Δ

YBaCuO-type oxides of the YSr2Cu2MO8-δ (M = Co, Fe) systems were previously studied as air electrodes for SOFCs1 and more recently have attracted great attention due to the electrocatalitic properties reported on YSr2Cu2FeO8-δ 2 and La1.5Ba1.5Cu3O7± δ.3 The compound YSr2Cu2FeO7.56 is a p-type semiconductor, mixed valence Fe3+/Fe4+ and Cu2+/Cu3+ oxide, which exhibits an interesting electrochemical behavior associated to catalytic activity in the oxygen reduction reaction (ORR), being a potential air-electrode for solid oxide fuel cells (SOFCs) 2. In this contribution we present a computational study of the YSr2Cu2FeO8-δ (0< δ <1) system. We have firstly evaluated the performance of the generalized gradient approximation (GGA), the strongly constrained and appropriately normed (SCAN), and their Hubbard U corrections, GGA+U and SCAN+U, to reproduce the crystal and electronic crystal structures of YSr2Cu2FeO8-δ with δ = 0, 0.5 and 1. . The results validate the SCAN functional for the reliable investigation of these compounds. Further, the position of the oxygen electronic 2p band center is discussed as descriptor for the catalytic activity of these oxides. J. E. H. Sansom, E. Kendrick, H. A. Rudge-Pickard, M. S. Islam, A. J. Wright and P. R. Slater, Journal of Materials Chemistry, 2005, 15, 2321-2327.S. A. Lopez-Paz, R. Marin-Gamero, X. Martinez de Irujo-Labalde, J. Sanchez-Marcos, D. Perez-Coll, M. A. A. y. Franco and S. Garcia-Martin, Journal of Materials Chemistry A, 2021, 9, 8554-8560.A. N. Keyun Li, K. Świerczek, A. Stępień, Y. Naumovich, J.Dąbrowa, M. Zajusz, K. Zheng, B. Dabrowski, Journal of Power Sources, 2022, 532, 231371.

Sustainable and Cost-Effective Bio-Waste-Derived Hard Carbon Synthesis for Sodium-Ion Batteries

The commercialization of sodium-ion batteries (SIBs) is around the corner to support on electrification of various applications, especially focused on light electromobility and stationary applications. The anode of choice in SIBs is hard carbon (HC) following the success story of graphite anode in lithium-ion batteries. [1-4] One of the greatest advantages of HC is that the bio-waste precursor can be used, enhancing sustainability and provides cheap material price from its abundance. However, bio-waste HC often undergoes a strong acidic/basic pre-/post-treatment for removing impurities and increasing carbon yield but decreases initial Coulombic efficiency (ICE) and total sodium uptake in turn. [5,6] We attempted to find a more sustainable solvent to replace the traditional method for such HCs. In this work, the morphology, microstructure, and electrochemical performance characteristics of hazelnut shells-derived HCs were investigated when processed in different pre-treatment agents (i.e., no pre-treatment, acid treatment, and water washing). [7] The results reveal that hazelnut shell derived-HCs produced via facile and sustainable water washing outperform those obtained via other processing methods in terms of ICE, capacity uptake and retention. Moreover, the applicability of the hazelnut shell-derived HC is demonstrated in a sodium-ion full-cell. Finally, the cost-ecological effectiveness of sustainably processed HC compared to acid processed one was investigated and confirmed by life cycle assessment (LCA) and cost analysis.[1] CATL, “CATL Unveils Its Latest Breakthrough Technology by Releasing Its First Generation of Sodium-ion Batteries,” 2021.[2] L. Cailloce, https://newscnrsfr/articles/a-battery-revolution-in-motion 2015.[3] S. Kuze, J. Kageura, S. Matsimoto, T. Nakayama, M. Makidera, M. Saka, T. Yamaguchi, T. Yamamoto, K. Nakane, R&D Report 2013, 1–13.[4] A. Rudola, A. J. R. Rennie, R. Heap, S. S. Meysami, A. Lowbridge, F. Mazzali, R. Sayers, C. J. Wright, J. Barker, Journal of Materials Chemistry A 2021, 9, 8279–8302.[5] S. Ghosh, R. Santhosh, S. Jeniffer, V. Raghavan, G. Jacob, K. Nanaji, P. Kollu, S. K. Jeong, A. N. Grace, Sci. Rep. 2019, 9, 16315.[6] K. L. Hong, L. Qie, R. Zeng, Z. Q. Yi, W. Zhang, D. Wang, W. Yin, C. Wu, Q. J. Fan, W. X. Zhang, Y. H. Huang, Journal of Materials Chemistry A 2014, 2, 12733–12738.[7] H. Moon, A. Innocenti, H. Liu, H. Zhang, M. Weil, M. Zarrabeitia, S. Passerini, ChemSusChem 2022 DOI: 10.1002/cssc.202201713

Pt-Doped Lanthanum Ferrites as Versatile Electrode Material for Solid Oxide Cells

La0.6Sr0.4Fe0.8Co0.2O3-δ (LSCF) alone or mixed with doped ceria represents the reference air electrode material for IT-SOFC/SOEC, thanks to its intrinsic MIEC nature and unrivaled catalytic activity towards oxygen exchange reactions. Nevertheless, a steep growth in cobalt demand for automotive (EVs) and storage applications is expected in the next decades, and ethical issues related to cobalt mining in politically unstable countries endanger cobalt supply chain [1]. Noble metal doping to a low extent ( ≤ 5% mol) has drawn attention as a valid strategy to provide the parent oxide structure with high catalytic activity [2][3]. Such amounts of platinum-group-metals (PGM) could be profitably harvested from secondary sources, such as spent automotive three-way catalysts (TWCs) [4], rendering their supply less dependent from localized low-grade ores. In particular, due to the tendency of PGM to be easily reduced to the metallic state, PGM-doped perovskites have found application mainly as fuel electrode materials. Noble metal exsolution endows the parent perovskite with finely dispersed nanoparticles firmly anchored to the oxide substrate, that display high catalytic activity and stability [5].Here, platinum-doping on strontium-substituted lanthanum ferrites is explored as an innovative strategy to enhance the parent perovskite catalytic activity both in reducing and oxidizing environment. The ultimate goal is the design of a multi-functional electrode for Reversible Solid Oxide Cells (r-SOCs). La0.6Sr0.4Fe1-xPtxO3-δ, X = 0.005, 0.01, 0.05 (LSFPtX) stoichiometries were successfully synthesized and characterized by means of X-ray Powder Diffraction (XPRD) (Fig. 1), thermogravimetric analysis (TG), oxygen temperature-programmed desorption (O2-TPD) and X-ray photoelectron spectroscopy (XPS). LSFPtX were tested in symmetric cells to evaluate their activity as air electrode materials in terms of polarization resistance vs. temperature and vs. pO2. The rate-limiting steps of oxygen exchange reactions were investigated by means of electrochemical impedance spectroscopy (EIS) fitting experimental data with equivalent circuit (EC) modelling and distribution of relaxation times (DRT). Results were compared both to the undoped (LSF) and to a commercially available state-of-art 20 mol% Co-substituted LSCF. LSFPtX structural evolution is evaluated at different pO2 and in several SOCs operational environments (5%H2/Ar, 100% CO2 and 50% CO2 : 50% CO). B-site exsolution was studied by means of temperature-programmed reduction (H2-TPR) and scanning electron microscopy (FE-SEM) to assess their applicability as fuel electrode materials as well. Finally, LSGM-based symmetric cells were tested as SOFC and CO2-SOEC, evaluating the operational reversibility and the long-term stability.[1] IEA, Total Cobalt Demand by Sector and Scenario, October 2022, pp. 2020–2040.[2] Marcucci, A., Zurlo, F., Sora, I. N., Placidi, E., Casciardi, S., Licoccia, S., & Di Bartolomeo, E. (2019). A redox stable Pd-doped perovskite for SOFC applications. Journal of Materials Chemistry A, 7(10), 5344-5352.[3] Marasi, M., Duranti, L., Luisetto, I., Fabbri, E., Licoccia, S., & Di Bartolomeo, E. (2023). Ru-doped lanthanum ferrite as a stable and versatile electrode for reversible symmetric solid oxide cells (r-SSOCs). Journal of Power Sources, 555, 232399.[4] Karim, S., & Ting, Y. P. (2021). Recycling pathways for platinum group metals from spent automotive catalyst: A review on conventional approaches and bio-processes. Resources, Conservation and Recycling, 170, 105588.[5] Kothari, M., Jeon, Y., Miller, D. N., Pascui, A. E., Kilmartin, J., Wails, D., ... & Irvine, J. T. (2021). Platinum incorporation into titanate perovskites to deliver emergent active and stable platinum nanoparticles. Nature Chemistry, 13(7), 677-682. Figure 1

Leveraging Temperature-Dependent (Electro)Chemical Kinetics to Accelerate Redox Flow Battery Active Material Characterization

Aqueous Organic Redox Flow Batteries (AORFBs) have emerged as promising and potentially disruptive technologies for the storage of electrical energy from intermittent renewable sources for use over long discharge durations when the sun isn’t shining and the wind isn’t blowing. AORFBs could become preferred over Li-ion batteries for grid-scale stationary storage due to their potentially low-cost active materials made of earth-abundant elements, their inherent non-flammability, and the intrinsic decoupling of energy and power capacities in the flow battery design. Our group has demonstrated that calendar life, rather than cycle life, limits molecular lifetimes in AORFBs due to various molecular instabilities that lead to side reactions, thus inhibiting performance [1]. To accurately determine molecular fade rates, we utilize potentiostatic cycling to avoid artifacts caused by drifts in internal resistance and employ volumetrically unbalanced, compositionally symmetric cell configurations to distinguish molecular fade from membrane crossover or cell unbalancing. Redox-active organic molecule stability has improved to the point that the most stable chemistries degrade at less than 1% per year [2]. With further lifetime increases, the measurement of lower capacity fade rates necessitates higher precision coulometry methods [3] and thermally accelerated degradation protocols [4] to determine which stabilizing approaches are most effective without waiting for multi-month cycling tests to quantify capacity fade.We have developed a high-throughput setup for cycling AORFBs at elevated temperatures, providing a new dimension in the flow battery characterization space to explore. Capacity fade rates of previously published redox-active organic molecules, as functions of temperature, are evaluated in the high-throughput setup providing the ability to extrapolate fade rates to lower operating temperatures. The effect of temperature on electrochemical regeneration [5,6] of decomposed organic molecules is also explored. Collectively, these results highlight the importance of accelerated decomposition protocols to expedite the screening process of candidate molecules for long lifetime AORFBs, which may enable massive grid penetration of intermittent renewable energy.[1] M.-A. Goulet and M. J. Aziz, “Flow Battery Molecular Reactant Stability Determined by Symmetric Cell Cycling Methods,” Journal of The Electrochemical Society , 165, A1466 (2018).[2] M. Wu, Y. Jing, A. A. Wong, E. M. Fell, S. Jin, Z. Tang, R. G. Gordon, M. J. Aziz, “Extremely Stable Anthraquinone Negolytes Synthesized from Common Precursors,” Chem, 6, 1432 (2020).[3] T. M. Bond, J. C. Burns, D. A. Stevens, H. M. Dahn, J. R. Dahn, "Improving Precision and Accuracy in Coulombic Efficiency Measurements of Li-Ion Batteries", Journal of The Electrochemical Society, 160, A521 (2013).[4] D. A. Stevens, R. Y. Ying, R. Fathi, J. N. Reimers, J. E. Harlow, J. R. Dahn, "Using High Precision Coulometry Measurements to Compare the Degradation Mechanisms of NMC/LMO and NMC-Only Automotive Scale Pouch Cells", Journal of The Electrochemical Society, 161, A1364 (2014).[5] M. Wu, M. Bahari, E. M. Fell, R. G. Gordon, M. J. Aziz, “High-performance anthraquinone with potentially low cost for aqueous redox flow batteries”, Journal of Materials Chemistry A, 9, 26709 (2021).[6] Y. Jing, E. W. Zhao, M.-A. Goulet, M. Bahari, E. M. Fell, S. Jin, A. Davoodi, E. Jónsson, M. Wu, C. P. Grey, R. G. Gordon, M. J. Aziz, “In situ electrochemical recomposition of decomposed redox-active species in aqueous organic flow batteries,” Nature Chemistry, 14, 1103, (2022).Figure caption: Capacity fade rates of an anthraquinone derivative, measured in symmetric cells, as a function of temperature. Figure 1

Phase Stability of SrTi1-XFexO3- δ Under Solid Oxide Cell Fuel-Electrode Conditions: Implications for Related Exsolution Electrode Materials

Perovskite oxides with catalytically active metal nanoparticle exsolution are receiving considerable attention as alternative Solid Oxide Cell fuel-electrode materials. For exsolution, a small amount of a cation is substituted on the B-site of the base oxide and then is reduced out of the host lattice to form nanoparticles that promote electrochemical processes. During exsolution, the host lattice generally becomes more B-site deficient. In some cases, the oxide is made initially A-site deficient to compensate for the loss of B-site cations. Thus, the stability of these oxides under a range of stoichiometries and fuel electrode conditions is of interest.Here we focus on one perovskite host material of interest, SrTi1-xFexO3- δ (STF), which has shown good fuel electrode characteristics that can be enhanced by the substitution of Ru or Ni, resulting in exsolution to form Ru-Fe or Ni-Fe alloy nanoparticles, respectively. (1, 2) Although the amounts of Ru or Ni substituted are small, typically ~ 7% of the B-site cations, the co-exsolution of a comparable amount of Fe is usually observed, resulting in substantial B-site deficiency, potentially de-stabilizing the host perovskite phase. The stability of Fe in STF is also of interest because it helps to determine the Fe content of the alloy nanoparticles. (3)This study seeks to determine the stability of STF in various reducing fuel environments. While STF has been mostly studied as SrTi0.3Fe0.7O3-δ (STF-7), it is not known if this composition provides the best combination of stability and electrochemical performance. Thus, a few additional compositions, SrTi0.5Fe0.5O3- δ (STF-5), SrTi0.4Fe0.6O3- δ (STF-6), and SrTi0.2Fe0.8O3- δ (STF-8), have been studied. In general, the Fe-rich compositions are expected to possess higher electronic and ionic conductivity, leading to good electrochemical performance, whereas the more Ti-rich compositions are expected to provide better stability. Exposure to 97% H2 – 3% H2O at 850°C for 4 h resulted in STF decomposition into BCC α-Fe and a Ruddlesden-Popper (RP) phase, but the decomposition became more limited for the more Ti-rich compositions (Figure 1a). The main Fe peak overlaps with one of the RP peaks, but the presence of α-Fe particles is clearly visible in STEM energy dispersive x-ray spectroscopy chemical mapping, shown for STF-7 in Figure 1b. Figure 1c shows that there is a critical p(O2), 1.3 x 10-20 atm, below which decomposition of perovskite STF-7 occurs. In addition to ex situ XRD as shown in Figure 1, in situ XRD results will be presented and used to confirm and quantify phase changes in combination with thermogravimetric analysis (TGA). Additionally, the conductivity and electrochemical performance of the various STF compositions will be reported and discussed relative to the phase change from perovskite to Ruddlesden Popper and the Fe exsolution. The other main materials variable to be explored is the A-to-B site stoichiometry, which will be studied over the range expected during exsolution. The implications of these results for various exsolution electrode compositions will be discussed.Figure 1: a) Reductions of STF-5 through STF-8 all yield significant decomposition as the initially pristine perovskite acquires several additional peaks. b) Using energy dispersive x-ray spectroscopy, it can be shown that significant Fe deposits appear in STF-7 after reduction at 850°C (effective pO2 1.2e-21 atm for 4 hours). c By increasing pO2 by a factor of 10, XRD patterns for STF-7 show no clear Ruddlesden-Popper or α-Fe peaks, indicating that decomposition requires significantly reducing conditions and that STF may remain stable under more oxidizing conditions.References R. Glaser, T. Zhu, H. Troiani, A. Caneiro, L. Mogni and S. Barnett, Journal of Materials Chemistry A, 6, 5193 (2018).T. Zhu, H. Troiani, L. V. Mogni, M. Santaya, M. Han and S. A. Barnett, Journal of Power Sources, 439 (2019).T. Zhu, H. E. Troiani, L. V. Mogni, M. Han and S. A. Barnett, Joule, 2, 478 (2018). Figure 1

(Digital Presentation) Renewable Energy Storage Based on the Electrochemical Cycle of Hydrogen Peroxide

The large-scale application of intermittent renewable energy sources (such as wind and solar) requires low-cost, efficient, and zero-emission energy storage systems.1-5 Recently, we proposed an energy storage concept based on the electrochemical cycle of hydrogen peroxide (H2O2).6-8 As a proof-of-concept, we demonstrated a highly efficient PEM H2O2 electrolyzer (HPEL) for power-to-hydrogen conversion, and a unitized regenerative hydrogen peroxide cycle cell (UR-HPCC) with a round-trip efficiency (RTE) of above 90% for renewable energy storage.6, 7 The employment of platinum group metal-free (PGM-free) catalysts and other low-cost carbon materials in these devices promised a low system cost for large-scale energy storage.In this talk, we will present our recent study on the key factors affecting the performance and H2O2-cycle ability of the HPCC system. We identify the selectivity of anode catalyst in HPEL for hydrogen peroxide oxidation reaction (HPOR), the catalyst loading, and membrane thickness as the main performance-determining factors for HPEL. Specifically, the cobalt and nitrogen-doped carbon (Co-N-C) catalyst exhibits higher selectivity for HPOR over the H2O2 disproportionation reaction (HPDR) than Fe-N-C and Pt/C catalysts. Increasing the catalyst loading and membrane thickness can effectively inhibit the H2O2 crossover and thus improve the H2O2 utilization. By optimizing these factors, the crossover and disproportionation of H2O2 in the HPEL can be reduced significantly, resulting in higher system performance. On the other hand, high efficiency for H2O2 regeneration in the fuel cell component of the HPCC system is the key to the H2-H2O2 cycle. By optimizing the MEA fabrication method, catalyst loading, and operating conditions, we achieved high efficiency for H2O2 generation and remarkable power density in a PEM fuel cell. These results can guide the development of the next-generation large-scale renewable energy storage system. Acknowledgments Financial support from the State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences is greatly appreciated. This study is financially supported by the autonomous research project of SKLCC (Grant No. 2021BWZ006), ICC CAS (Grant No. 2020SC001), Key Research and Development (R&D) Projects of Shanxi Province (Grant No. 202102070301018), and Shanxi Province grant (Grant No. 202103021224442 and 20210302123011). References S. J. Davis et al., Net-zero emissions energy systems. Science 360, eaas9793 (2018).X. Yang, C. P. Nielsen, S. Song, M. B. McElroy, Breaking the hard-to-abate bottleneck in China’s path to carbon neutrality with clean hydrogen. Nature Energy 7, 955-965 (2022).A. C. Bhosale, P. C. Ghosh, L. Assaud, Preparation methods of membrane electrode assemblies for proton exchange membrane fuel cells and unitized regenerative fuel cells: A review. Renewable and Sustainable Energy Reviews 133, 110286 (2020).Z. Pu et al., Regenerative fuel cells: Recent progress, challenges, perspectives and their applications for space energy system. Applied Energy 283, 116376 (2021).J. Tang, C. Su, Y. Zhong, Z. Shao, Oxide-based precious metal-free electrocatalysts for anion exchange membrane fuel cells: from material design to cell applications. Journal of Materials Chemistry A, 9, 3151-3179 (2021).R. Ding et al.. Low-voltage hydrogen peroxide electrolyzer for highly efficient power-to-hydrogen conversion. ChemRxiv, doi:10.26434/chemrxiv-2021-9dmp4 (2021).J. Yang et al., Highly efficient unitized regenerative hydrogen peroxide cycle cell with ultralow overpotential for renewable energy storage. Journal of Power Sources 545, 231948 (2022).R. Ding et al., (Digital presentation) Hydrogen peroxide electrolyzer and reversible hydrogen peroxide cycle cell for renewable energy storage, Meeting s, The Electrochemical Society, MA2022-01, 2495 (2022).

Synergistic Microfluidic and Optical Performance Enhancements of Photoelectrodes for Space Applications

The realisation of long-term space missions as well as lunar habitats require reliable and efficient oxygen and chemical producing devices e.g., for life support, fuel generation and in-situ resource utilisation (ISRU). We have recently demonstrated that integrated semiconductor-electrocatalyst systems can be operated in microgravity environments generated for 9.2 s at the Bremen Drop Tower (Center of Applied Space Technology and Microgravity, ZARM) at terrestrial efficiencies, thus opening the possibility of utilising these photoelectrochemical (PEC) devices for chemical synthesis in space. 1,2 , 3 Our findings reveal that by altering the electrocatalyst surface morphology through nanostructuring, we can introduce catalytic hot-spots on the photoelectrode which - through their hydrophilic nature - can also enhance gas bubble detachment in microgravity and thus circumvent the near-absence of buoyancy.1,3 We have found that the surface hydrophilicity and electrocatalyst loading require however careful balancing as the most effective nanostructures for gas bubble desorption can also result in less catalyst material on the photoelectrode surface, which in turn leads to a non-optimal PEC device performance.Here, we present a combined theoretical and experimental microfluidic, optical and photoelectrocatalytic performance analysis of photoelectrodes with integrated, nanostructured electrocatalysts, aiming at providing a guideline for an optimal design for microgravity applications. Focusing on the hydrogen evolution reaction (HER) and a well-investigated photoabsorber for this reaction, p-type InP, we firstly built an optoelectronic model in COMSOL Multiphysics in pursuit of quantifying the optical performance enhancements of Rh and Pt electrocatalyst nanostructures such as nanopyramids, nanowires and sub-wavelength aperture holes.4 We then developed a microfluidic model using the same nanostructure geometries to predict the hydrophilicity of the device surface and subsequently, the gas bubble contact angle. The best-performing nanostructured photoelectrodes predicted in our models where then manufactured, photoelectrochemically tested and fully optically and spectroscopically characterised. Predicted local electric field enhancements through catalytic hotspot formation were moreover experimentally validated using scanning electrochemical cell microscopy (SECCM). Our findings indicate that our developed optoelectronic and microfluidic models can be utilised to design a theoretical framework for identifying ideal electrocatalyst nanostructures for microgravity applications.References Brinkert K, et al. Efficient solar hydrogen generation in microgravity environment. Nature Communications 9, (2018). Brinkert K, Mandin P. Fundamentals and future applications of electrochemical energy conversion in space. npj Microgravity 8, (2022). Akay Ö, et al. Releasing the Bubbles: Nanotopographical Electrocatalyst Design for Efficient Photoelectrochemical Hydrogen Production in Microgravity Environment. Advanced Science 9, 2105380 (2022). Tembhurne S, Haussener S. Integrated Photo-Electrochemical Solar Fuel Generators under Concentrated Irradiation. Journal of The Electrochemical Society 163, H988 (2016). Pan Y, Huang S, Li F, Zhao X, Wang W. Coexistence of superhydrophilicity and superoleophobicity: theory, experiments and applications in oil/water separation. Journal of Materials Chemistry A 6, 15057-15063 (2018).

(Invited) Diffuse Light Harvesting to Structured Information with Hybrid Photovoltaics

By 2025 about 75 billion IoT devices will be installed, of which the majority will reside indoors. It is therefore crucial to find an energy source that yields high efficiencies in this environment.1,2 At 34% efficiency under ambient light, while being more environmentally friendly, sustainable to produce and to recycle. Dye-sensitized solar cells (DSCs) are known for efficient conversion of ambient light. Fast charge separation in a variety of organic dyes and tuneable energy levels in CuII/I redox systems combined with negligible recombination processes allow DSCs to maintain a high photovoltage under ambient light.1 We tailored dye-sensitized photovoltaic cells based on a copper (II/I) electrolyte for power generation under ambient lighting with an unprecedented conversion efficiency (PCE 34 %, 103 mW cm-2 at 1000 lux; 32.7 percent, 50 mW cm-2 at 500 lux; and 31.4 percent, mW cm-2 at 200 lux from a fluorescent lamp) using a novel co-sensitization strategy.2 Though there are additional factors to consider when converting ambient light. First, rather of simply extending the absorption range, the DSC's spectral conversion response should be tailored to the source of ambient lighting. Second, at low light intensities, recombination suppression is critical for DSC performance.3 Though there are additional factors to consider when converting ambient light. First, rather of simply extending the absorption range, the DSC's spectral conversion response should be tailored to the source of ambient lighting. Second, at low light intensities, recombination suppression is critical for DSC performance. Herein, we developed DSCs with CuII/I(tmby)2 (tmby = 4,4′,6,6′-tetramethyl-2,2′-bipyridine) hole transport material with a combination of organic sensitizers XY1 and L1. Under simulated sunlight (AM 1.5G, 100 mW cm−2), the best device reached a photovoltage of 1080 mV, a photocurrent density of 15.9 mA cm−2, a fill factor of 0.67 and a PCE of 11.5%.4,5 Under 1000 lux lighting, 64 cm2 photovoltaic area gives 152 J or 4.41 1020 photons sufficient for training and testing of an artificial neural network in less than 24 hours. Ambient light harvesters enable a new generation of self-powered and "smart" IoT gadgets to be fueled by a hitherto untapped energy source.2 Muñoz-García, A. B. et al. Dye-sensitized solar cells strike back. Chemical Society Reviews 50, 12450–12550 (2021).Michaels, H. et al. Dye-sensitized solar cells under ambient light powering machine learning: towards autonomous smart sensors for the internet of things. Chemical Science 11, 2895–2906 (2020).Freitag, M. et al. Dye-sensitized solar cells for efficient power generation under ambient lighting. Nature Photonics 11, 372–378 (2017).Michaels, H., Benesperi, I. & Freitag, M. Challenges and prospects of ambient hybrid solar cell applications. Chemical Science (2021) doi:10.1039/D0SC06477G.Benesperi, I., Michaels, H. & Freitag, M. The researcher’s guide to solid-state dye-sensitized solar cells. Journal of Materials Chemistry C (2018) doi:10.1039/C8TC03542C.

Micropatterned Ion-Exchange Membranes for Membrane Capacitive Deionization

US Marine missions require technologies that produce potable water from various water sources that include both seawater and ground water. Reverse osmosis (RO) is the most wide-spread and economical process for desalinating water from seawater. However, it is only cost-competitive and practical when deployed in large, centralized production facilities and is not conducive for marine squad units. Membrane capacitive deionization (MCDI) is an alternative water desalination platform that is enticing to military missions as it does not require high pressure piping and it does not generate significant acoustic, thermal, or electromagnetic signals. MCDI removes ions from the liquid solution using electrical energy, and the commercialized variant, flow-by MCDI, feature two porous electrodes covered by ion-exchange membranes(1). During deionization, the positively biased electrode has an anion exchange membrane (AEM) in front of it while the negatively biased electrode contains a cation exchange membrane (CEM) in front of it.Our previous research improved the energy efficiency of MCDI by using ion-exchange membranes with lower area-specific resistance (ASR) values(2) and porous ionic conductors in the spacer channel that augment solution conductivity and curtail ohmic losses(3). Reducing these resistances enabled the MCDI to operate at higher current density – which is important for shrinking the size of the MCDI unit and lowering the overall capital costs.This talk highlights our recent work examining ionic charge transport resistance at the membrane-electrode interface in MCDI. We studied the impact of this resistance on MCDI performance metrics (salt removal and energy normalized adsorbed salt (ENAS)) by systematically changing the interfacial area of the ion-exchange membrane-electrode interface via patterning of the ion-exchange membrane surfaces using soft-lithography. This strategy has been shown to be effective in reducing charge-transfer resistances in both proton exchange membrane (PEM)(4) and AEM(5) fuel cells and reducing the water dissociation kinetics resistance in bipolar membranes(6). Micropatterned AEMs and CEMs based upon poly(arylene ether) and all-carbon poly(arylene) backbones(7) were fabricated with periodic line and cylinder topographies and lateral feature sizes that vary from 2 to 20 μm. The patterned membranes were coated with graphitic carbon electrodes. It is posited that smaller lateral feature sizes, which gives rise to larger interfacial area values, reduces interfacial resistance values in MCDI and larger ENAS values. Keywords: Desalination, Membrane capacitive deionization, Ion exchange membranes, Soft lithography, Energy normalized adsorbed salt, Membrane electrode assembly References S. Porada, L. Zhang and J. E. Dykstra, Desalination, 488, 114383 (2020).V. M. Palakkal, J. E. Rubio, Y. J. Lin and C. G. Arges, ACS Sustainable Chemistry & Engineering, 6, 13778 (2018).V. M. Palakkal, M. L. Jordan, D. Bhattacharya, Y. J. Lin and C. G. Arges, Journal of The Electrochemical Society, 168, 033503 (2021).Y. Jeon, D. J. Kim, J. K. Koh, Y. Ji, J. H. Kim and Y.-G. Shul, Scientific Reports, 5, 16394 (2015).S. Jang, M. Her, S. Kim, J.-H. Jang, J. E. Chae, J. Choi, M. Choi, S. M. Kim, H.-J. Kim, Y.-H. Cho, Y.-E. Sung and S. J. Yoo, ACS Applied Materials & Interfaces, 11, 34805 (2019).S. Kole, G. Venugopalan, D. Bhattacharya, L. Zhang, J. Cheng, B. Pivovar and C. G. Arges, Journal of Materials Chemistry A, 9, 2223 (2021).W.-H. Lee, Y. S. Kim and C. Bae, ACS Macro Letters, 4, 814 (2015).