Electrolytic Reaction Research Articles

Electrode Selection and Catalyst Evaluation in Hydrogen Production from Alkaline Water Electrolysis: A Review

Generating hydrogen, through alkaline water electrolysis shows promise as an energy source. This review delves into the significance of choosing the electrodes and evaluating catalysts to enhance the efficiency and performance of hydrogen production. It summarizes the activation energy and losses linked to reactions in alkaline electrolysis emphasizing the necessity for electrode materials and catalysts. The review also touches upon challenges such as electricity consumption and platinum group metal based electro catalysts proposing various electrode materials and catalysts with superior activity and selectivity for hydrogen production. Additionally, it discusses electrolysis cell designs that facilitate separating by-products from hydrogen gas. The study reveals that with low over potentials of 70, 318, and 361 mV at 10, 500, and 1000 mA cm−2, respectively, NiOx/NF exhibits strong alkaline hydrogen evolution activity, resulting in great performance in alkaline HER. Moreover, it outlines advancements in alkaline water electrolysis technology focusing on enhanced efficiency and reduced operating costs associated with electricity consumption. Overall this review underscores the role of selecting electrodes and evaluating catalysts in optimizing hydrogen production from alkaline water electrolysis.

Impact of Aerogel Modification for Fe-N-C Activity and Stability towards Oxygen Reduction Reaction in Phosphoric Acid Electrolyte.

Resorcinol-formaldehyde based carbon aerogel (CA) has been tailored to meet the requirements as a Fe-N-C carbon support, aiming to provide sufficient, inexpensive cathode catalysts for high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). Therefore, different treatments of the aerogel are explored for optimal pore structure and incorporation of surface functionalities, which are crucial for Fe-N-C synthesis and electrochemical performance. Fe-N-Cs of differently modified aerogel are investigated in phosphoric acid electrolyte. The results show that HNO3 treatment for 5 h yields the Fe-N-C with highest mass activity and selectivity, attributed to the highest amount of nitrogen functionalities revealed by energy dispersive X-ray spectroscopy (XPS) and proper Fe-Nx site formation. HNO3 oxidation for 2 h leads to Fe-N-C with slightly lower oxygen reduction reaction (ORR) activity and selectivity. In contrast, the Fe-N-C synthesized from CA with H3PO4 treatment shows negligible ORR activity. The feasibility of one-step activation and carbonization treatment with K2CO3 and, for the first time, with K2CO3 and melamine is proven as the obtained Fe-N-Cs exhibit promising ORR activity. The results are compared with the commercial Fe-N-C PMF-014401. This study contributes to the advancement of cost-efficient HT-PEMFCs by optimizing Fe-N-C catalyst properties.

Non-Aqueous Electrochemical CO2 Reduction to Multivariate C2-Products Over Single Atom Catalyst at Current Density up to 100mAcm-2.

Electrochemical CO2 reduction reaction (CO2-RR) in non-aqueous electrolytes offers significant advantages over aqueous systems, as it boosts CO2 solubility and limits the formation of HCO3 - and CO3 2- anions. Metal-organic frameworks (MOFs) in non-aqueous CO2-RR makes an attractive system for CO2 capture and conversion. However, the predominantly organic composition of MOFs limits their electrical conductivity and stability in electrocatalysis, where they suffer from electrolytic decomposition. In this work, electrically conductive and stable Zirconium (Zr)-based porphyrin MOF, specifically PCN-222, metalated with a single-atom Cu has been explored, which serves as an efficient single-atom catalyst (SAC) for CO2-RR. PCN- 222(Cu) demonstrates a substantial enhancement in redox activity due to the synergistic effect of the Zr matrix and the single-atom Cu site, facilitating complete reduction of C2 species under non-aqueous electrolytic conditions. The current densities achieved (≈100mAcm- 2) are 4-5 times higher than previously reported values for MOFs, with a faradaic efficiency of up to 40% for acetate production, along with other multivariate C2 products, which have never been achieved previously in non-aqueous systems. Characterization using X-ray and various spectroscopic techniques, reveals critical insights into the role of the Zr matrix and Cu sites in CO2 reduction, benchmarking PCN-222(Cu) for MOF-based SAC electrocatalysis.

Flow field design and visualization for flow-through type aqueous organic redox flow batteries

Aqueous organic redox flow batteries (AORFBs), which exploit the reversible redox reactions of water-soluble organic electrolytes to store electricity, have emerged as a promising electrochemical energy storage technology. Organic electrolytes possess fast electron-transfer rates that are two or three orders of magnitude faster than those of their inorganic or organometallic counterparts; therefore, their performance at the electrode is limited by mass transport. Direct adoption of conventional cell stacks with flow fields designed for inorganic electrolytes may compromise AORFB performance owing to severe cell polarization. Here, we report the design of a flow field for flow-through type AORFBs based on three-dimensional multiphysics simulation, to realize the uniform distribution of electrolyte flow and flow enhancements within a porous electrode. The electrolyte flow is visualized by operando imaging. Our results show that multistep distributive flow channels at the inlet and point-contact blocks at the outlet are crucial geometrical merits of the flow field, significantly reducing local concentration overpotentials. The prototype pH-neutral TEMPTMA/MV cell at 1.5 M assembled with the optimized flow field exhibits a peak power density of 267.3 mW cm-2. The flow field design enables charging of the cell at current densities up to 300 mA cm-2, which is unachievable with the conventional serpentine flow field, where immediate voltage cutoff of the cell occurs. Our results highlight the importance of AORFB cell stack engineering and provide a method to visualize electrolyte flow, which will be appealing to the field of aqueous flow batteries.

Insights into polymer electrolyte stability and reaction pathways: A first-principle calculations study.

To identify suitable polymer candidates for electrolytes in solid-state batteries, this study investigates the electrochemical behavior and decomposition pathways of four monomers involving esters, ethers, and carbonates via first-principles calculations. In particular, we determine the oxidation and reduction potentials of these monomers near different ions (Li+, TFSI-, and [Li]+[TFSI]-) and the corresponding reorganization energies. The latter quantity is central to Marcus theory of electron transfer and, therefore, provides additional kinetic information. Our results reveal notable sensitivity of the monomers to reduction in a Li+-rich regime and to oxidation in a TFSI--rich regime. Additionally, the reactivity and decomposition pathways of the monomers were investigated for various electrochemical environments, focusing on the quantification of gaseous and ionic products during the initial stage of formation of interphasial layers. Based on the electrochemical windows and spontaneous Ab initio molecular dynamics calculations, we observe that monomers containing carbonate groups exhibit greater stability against decomposition caused by reduction, especially in different regimes, when compared to monomers with ester and ether groups.

Porous Amorphous-Crystalline Heterostructured CoNiP Nanowire Arrays for Enhanced Hydrogen Evolution Performance under Acid-Base Conditions.

A novel porous amorphous-crystalline heterostructured CoNiP nanowire arrays ((a-c)CoNiP/CC) is presented. TEM observations and compositional calculations revealed ≈14.5% of the amorphous regions (a-CoNiP) are interleaved in the crystalline regions (c-(Co3.6Ni0.4)P4), forming massive amorphous-crystalline heterogenous interfaces composed of the same elements. Only 38 and 64mV overpotentials for the (a-c)CoNiP/CC catalyst are required to reach the current density of -10mAcm2 in acid and alkaline electrolyte, respectively, which is very close to the overpotentials (35 and 55mV) of the commercial Pt/C HER catalyst. The theoretical calculation revealed that the (a-c)CoNiP/CC has a completely different enhancement mechanism of HER reaction in acid-base electrolytes. In particular, due to the natural corrosion resistance of the amorphous interface, the HER performance of this catalyst under the high current density condition is much better than that of the Pt/C catalyst either in acidic or in alkaline, suggesting its prospect for commercial applications.

Design Concepts of High-Entropy Materials for Zinc Ion Batteries.

Zinc-ion batteries have emerged as strong candidates for replacing Li/Na-ion batteries owing to their high safety and environmental friendliness. However, the large electrostatic repulsion between the cathode and Zn2+, the irreversible growth of zinc dendrites at the anode, and the hydrogen precipitation side reaction in the aqueous electrolyte have hindered the practical application of zinc ion batteries. Fortunately, the emergence of the revolutionary concept of high entropy has provided new opportunities for the development of battery materials. High-entropy materials, with their unique atomic structures and uniform distribution of multiple elements, offer flexible options for material compositions and electronic structures, thus attracting significant attention in battery systems. In this concept article, we summarize the definitions and intrinsic structural characteristics of high-entropy materials and provide a detailed overview of the latest design concepts from the perspectives of cathodes, anodes, and electrolytes. Finally, we outline the challenges faced by high-entropy materials and potential solutions to guide researchers in developing efficient and stable zinc-ion batteries.

Electrochemical Performance of Fuel Electrodes in Solid Oxide Co-Electrolysis Cells Operated Under Various Conditions

Introduction Solid oxide co-electrolysis cells are electrochemical devices which can electrolyze steam and carbon dioxide at the same time into hydrogen and carbon monoxide which are components of synthesis gas. Waste heat can be recycled effectively by creating a combined system of carbon hydrate synthesizer and the cells, and along with high temperature operation, carbon dioxide can be also recycled to carbon hydrates with high efficiency. To design a co-electrolysis system, and calculate efficiency numerically, characteristics of the solid oxide co-electrolysis cells must be clarified. In this study, we aim to obtain and quantify electrochemical characteristics of fuel electrodes in solid oxide co-electrolysis cells by measuring I-V curve and calculating exchange current density in various operating conditions, to be applied in solid oxide co-electrolysis system planned as future work. Experimental The tested electrolyte-supported solid oxide cell consists of Ni-YSZ (8 mol%Y2O3 – 92 mol%ZrO2) cermet, a composite of Ni and YSZ, as fuel electrode, YSZ plate as electrolyte, and LSCF ((La0.6Sr0.4)(Co0.2Fe0.8)O3) as air electrode. Gas mixture of hydrogen, vapor, carbon-dioxide, and nitrogen were supplied to the fuel electrode with the total flow rate of 100 ml min-1. Some conditions to evaluate the effect of gas composition on the fuel electrode performance are shown in Figure 1 (a). On the other hand, dry air was supplied to the air electrode with the total flow rate of 150 ml min-1. I-V curve and electrochemical impedance were obtained using a Solartron electrochemical measurement system. A phenomenological exchange current density equation of the fuel electrode was obtained by regression analysis based on the experimental results [1-3]. Results and Discussion Figure 1 (b) shows the fitted exchange current density obtained by considering hydrogen-water vapor reaction as well as carbon monoxide-carbon dioxide reaction. From the peak in the graph, the obtained exchange current density depended on the partial pressures of hydrogen and water vapor. Therefore, in the cases shown in Figure 1 (a), compared with CO2 electrolysis reaction, steam electrolysis reaction seems to be the dominant reaction at fuel electrodes in solid oxide co-electrolysis cells [4,5]. In the presentation, dependencies of operating temperature, and partial pressure of each gas component will be discussed. Reference [1] T. Fukumoto, N. Endo, K. Natsukoshi, Y. Tachikawa, G.F. Harrington, S.M. Lyth, J. Matsuda, and K. Sasaki, Int. J. Hydrogen Energy, 47 (37), 16626-16639 (2022).[2] K. Takino, Y. Tachikawa, K. Mori, S.M. Lyth, Y. Shiratori, S. Taniguchi, and K. Sasaki, Int. J. Hydrogen Energy, 45 (11), 6912-6925 (2020).[3] W. Dreyer, C. Guhtke, and R. Müller, Phys. Chem. Chem. Phys., 18, 24966-24983 (2016).[4] S.D. Ebbesen, R. Knibbe, and M. Mogensen, J. Electrochem. Soc., 159 (8), F482-F489 (2012).[5] S-H. Lee, J-W. Lee, S-B. Lee, S-J Park, R-H. Song, U-J. Yun, T-H. Lim, Int. J. Hydrogen Energy, 41 (18), 7530-7537 (2016). Figure 1

Characterization of Electrolyte Reduction Reactions on Freshly Plated Lithium Using Electrochemical Heat Flow Calorimetry

Electrochemical heat flow calorimetry can be used to measure the evolved heat during the operation of a lithium-ion battery cell. The data obtained are useful for the optimization of thermal management systems on the cell and system level, but they can also be used to detect and characterize parasitic reactions, such as unwanted reactions of the electrolyte. The heat evolved from a reversibly operated lithium-ion cell can be described as the sum of irreversible heat, resulting from cell polarization, and reversible heat, related to entropy changes.1 In order to quantitatively measure the contribution of a parasitic heat flow, which is usually small in comparison, the irreversible and reversible heat flow must be known to a high accuracy. Two main approaches have been reported in the literature to obtain such defined measurement conditions.2, 3 The first method requires the integration of the heat flow over a full charge/discharge cycle.2 This cancels the reversible heat flow contributions and enables an estimation of the total irreversible heat from the difference of the charge and discharge energies. The second method analyzes the heat flow during a voltage hold after the cell has reached a steady-state condition and exclusively exhibits parasitic processes.3 Both of these approaches allow for an estimation of the mean reaction enthalpies per mole of electrons when the parasitic heat is correlated to the irreversible capacity or to the parasitic current, respectively.In the present work, we introduce an approach to characterize the heat of the electrolyte reduction reactions on freshly plated lithium. For this, we measure the heat flow during overlithiation of an artificial graphite electrode in a half-cell, using our previously reported setup.4 Figure 1 shows the voltage profile and the measured heat flow for an exemplary experiment, where the graphite electrode is first fully lithiated and then overlithiated to induce significant lithium plating before the electrode is fully delithiated again. Both the voltage and heat flow curves show characteristic features indicating lithium plating (LP) and lithium stripping (LS).5 During continuous lithium plating we expect a significant contribution of a parasitic heat flow from the electrolyte reduction reactions on the newly exposed lithium surface. The here analyzed conditions enable a straightforward separation of this parasitic heat flow from the reversible and irreversible heat flow contributions from lithium plating: since lithium is being plated on already deposited lithium on the graphite electrode surfaces and simultaneously being stripped from the lithium metal counter electrode, the system can be considered a quasi-symmetrical cell. This means that the reversible heat flow contributions cancel out and that the irreversible heat flow from cell polarization can be calculated from the offset of the measured cell voltage from 0 V. In the present study, we analyzed the parasitic heat flow during lithium plating, changing different measurement parameters (e.g., degree of overlithiation, plating current, electrolyte) to gain insights into the interplay of lithium plating and electrolyte reactions. By a correlation to the irreversible capacity losses, the mean reaction enthalpy per mole of electrons can be estimated. Finally, the results were correlated to electrolyte reduction reactions postulated by gassing analysis from online electrochemical mass spectrometry (OEMS) measurements. The gas analysis allows for comparing electrolyte reduction pathways at larger potentials (~0.8 V vs. Li+/Li) during the formation of a pristine graphite surface as compared to electrolyte decomposition onto plated lithium at potentials around 0 V vs. Li+/Li. Acknowledgements We gratefully acknowledge the German Federal Ministry of Education and Research (BMBF) for its financial support within the AQua HysKaDi project (03XP0321B).

Toward a Fundamental Understanding of Solid-Solid Interfaces in Hydrogen Fuel Cells and Water Electrolysis through First-Principles Based Modeling

To achieve Net-Zero Emissions by 2050, hydrogen and hydrogen fuel cells will play a significant role in powering vehicles. In this talk, I will show, through first-principles-based modeling, how to achieve rigorous modeling and a fundamental understanding of the solid-solid interface for the oxygen reduction reaction in hydrogen fuel cells and the hydrogen evolution and oxygen evolution reactions in water electrolysis. I will further show how the fundamental understanding paves the way toward developing both model and industrial electrocatalysts with significantly improved performance. Specifically, I will introduce the following three topics.[1] metal-metal interfaces: strain generation and strain tuning of epitaxial, stepped and free-standing platinum group metals for the oxygen reduction reaction in hydrogen fuel cells. (1, 2)[2] metal-oxide interfaces: stability and activity of monolayer oxide/Pt interface toward improving the hydrogen evolution reaction in the alkaline electrolysis.(3)[3] oxide-oxide interfaces: self-consistent modeling of active phases, reaction centers, and catalytic mechanisms of Ni- and Co-based layered double hydroxides for the oxygen evolution reaction in the alkaline electrolysis.(4-6)

CO2 Electrolysis Coupled with Hydrogen Oxidation Reaction in Non-Aqueous Aprotic Electrolytes

CO2 electrolysis (CO2E) coupled with renewable energy is an important strategy to mitigate the effects of the green house gas in the atmosphere. By effectively transforming CO2 into higher value chemicals and fuels, the carbon cycle can be closed.[1] In order to produce C2+ products, most of the studies have been done in aqueous electrolytes, using Cu based catalysts. Nevertheless, these systems show different critical problems. First, in low temperature CO2E, CO2 carbonation in water is the primary source of energy and carbon losses.[2] Moreover, these systems rely on low faradaic efficiencies (FE) towards the single C2+ products (ethylene, ethanol, propanol). CO2E in organic aprotic electrolyte is gaining more and more attention due to the possibility of controlling the proton dynamics and the higher FE towards target products, mainly CO and oxalate. One challenge of these systems is the counter reaction. Many are using sacrificial anodes, which are not suitable for continuous industrial application.[3] Hydrogen oxidation reaction (HOR) is a promising reaction that could lower down the overall cell voltage, and, at the same time, produce more protonated products. This approach is not new in these systems, lithium mediated ammonia electrosynthesis, for example, has achieved relevant results using HOR at the anode and aprotic based electrolytes.[4] Based on these prerogatives, this study investigates the feasibility of couple CO2E with HOR in organic aprotic systems with controlled water content. A DMF/TBAPF6 electrolyte was used due to the good CO2 solubility (194 mmol L-1)[5] and conductivity. The rotating disk electrode experiments set up in a glovebox proved the stability of the chosen electrolyte, with a potential window of 3.6V, a HOR’s onset potential at -0.5V vs Ag/AgCl, and an onset potential for CO2 reduction at around -1.5V vs Ag/AgCl. A gas diffusion electrode (GDE) cell was used to perform CA or CP studies. A sputtered Cu GDE was used at the cathode. At the anode, an electrochemical deposited Pt/Au GDE was implemented for the HOR. [4] From the gas analysis, CO, H2 and ethylene have been detected at current densities of 10 mA/cm2. To investigate further the catalyst stability, XPS and SEM were used on the catalyst before and after the electrochemical reaction. ICP-MS analyses were done on the electrolyte to assess the eventual metal leaching during reaction.

Surface Reaction of Argyrodite-Type Sulfide Solid Electrolyte in Air with a Dew Point of −20°C

Sulfide solid electrolytes are expected to be used for practical all solid-state batteries because they combine high formability with high ionic conductivity. However, unlike oxide and organic solid electrolytes, sulfide solid electrolytes have problems such as toxic hydrogen sulfide generation and conductivity degradation due to even slight moisture. In this study, we investigated the details of the denaturation of argyrodite-type sulfide solid electrolyte (ASSE) by a small amount of water, with the aim of further increasing the water resistance of ASSE. The denaturation of ASSE in air with moisture at the dew point −20 °C, which is comparable to a typical dry room environment, was already reported; EIS and XRD revealed only the surface of ASSE degraded by moisture in the air. Surface analysis was also conducted and revealed that surface degraded components such as Li2CO3, Li2SO4 are formed on the surface.In this study, the effects of oxygen and carbon dioxide were also examined in addition to water. Details of the denaturation was investigated using XRD, XPS, IR and Raman. This investigation revealed that the denaturant is formed only on the surface by moisture, that the denaturant is oxidized by oxygen, and that Li2CO3 is formed by carbon dioxide. More details will be discussed at the meeting site.

(Invited) Electrocatalytic Synthesis of Ammonia and Urea

The electrocatalytic hydrogen cycle with nitrogen and carbon resources is of emerging interest for renewable energy and environment. Among nitrogen species, electrosynthesis of ammonia (NH3) from N2 or NOx and urea (CO(NH2)2) from N2 or NOx together with CO2 have attracted great attention with substantial progress in recent years as clean and energy-saving approach, to potentially replace the commercialized energy- & capital-intensive Haber-Bosch process.In order to accelerate the ammonia production rate, nitric oxide (NO) can be employed and converted to ammonia with high selectivity by capturing NO with FeII-EDTA.1) However, low concentration and the low solubility of NO (~1.94 mM in water at 25°C) is expected to affect ammonia production rate from direct electrochemical NO reduction reaction (NORR) in aqueous electrolytes. In order further increase the ammonia production rate, we employed a gas diffusion electrode (GDE) to circumvent the mass transport issue with a dilute NO gas.2) In addition, urea was successfully synthesized using Cu with atomic-scale spacings between copper facets, which lowers the energy barrier for C-N coupling and enhances the reaction kinetics, therefore leading to improved urea formation from co-reduction of carbon dioxide and nitrate in a flow-cell system.3) 1) ACS Energy Lett., 2020, 5, 3647-3656.2) ACS Energy Lett., 2022, 7, 958-965.3) Energy Environ. Sci., 2023, 16, 2003-2013.

Influence of Strong Metal-Support Interaction to the Noble Metal Catalyst for the Activity and Durability Oxygen Reduction Reaction

The stability and the activity of electrocatalysts in fuel cells and other applications can be improved by the strong interaction between noble metal nanoparticles and transition metal oxide, a phenomenon known as “strong metal-support interaction (SMSI).” Understanding and harnessing this interaction could lead to the development of more efficient and durable electrocatalysts. When SMSI occurs, the d-band center of noble metal as the catalyst changes to the favored state for the catalytic reaction or stability. Naturally, the variation of the d-band center depends on the combination of noble metal elements and transition metal oxide species, and the optimum state of the d-band is determined by the reaction. We focused on the oxygen reduction reaction (ORR), which is the cathode reaction of polymer electrolyte fuel cells (PEFCs). Because PEFCs require highly active and durable electrocatalysts.Generally, in catalysts where SMSI occurs, the electron-poor metal oxide covers the electron-rich noble metal particles in the reduction environment. On the other hand, the covered noble metal particles recover by conducting the oxidation treatment. An essential point for this phenomenon is that noble metal particles are smaller enough than metal oxide as the support or substrate. Therefore, the metal oxide layer can cover the noble metal particles. Theoretically, if the oxide layer is a few nanometers thick, it is difficult to cover the noble metal particles because the oxide layer is insufficient around them. In other words, it is expected that the electron structure of catalyst particles may be dramatically changed.The aim of this study was to find the optimum combination between noble metal and oxide for ORR in cathode catalysts in PEFCs. As the first step, Ir nanoparticles were deposited on the TiO2 layer, which was a few nanometers thick, and its ORR activity was evaluated. Electrooxidation by potential scanning was employed as the oxidation method for a model electrode. Moreover, the prepared Ir/TiO2 model electrode was conducted in the thermal reduction treatments, and the XPS analysis was performed to investigate the change in its electron structure. Other combinations, for example, Pt/TiO2, Ir/CeO2, etc., will be also done. Ir/TiO2 model electrode was composed of a glassy carbon substrate, a 1 nm TiO2 middle layer made from titanium oxide nanosheet, and Ir nanoparticles on the top deposited using the arc plasma deposition method. The electrochemical measurements were conducted using a three-electrode cell with a working electrode, a carbon rod counter electrode, an RHE reference electrode, and 0.1 M HClO4 at room temp. The reduction method was calcination at 500ºC under the reduction environment. The XPS results indicated that the TiO2 middle layer suppressed the valence variation of Ir nanoparticles. In this study, it was confirmed that the effects on ORR by introducing the TiO2 middle layer were stabilization of ORR activity in the Ir/TiO2 model electrode and inhabitation of the dissolution of Ir nanoparticles. In the day's presentations, we will compare with other combination model electrodes and discuss the relationship between valence variation and ORR activities of several model electrodes.

Advantageous Li3PO4 Coating on Conductive Agents for Sulfide-Based All-Solid-State-Batteries

Sulfide-based all-solid-state-batteries (ASSBs) are garnering attentions as a next-generation battery system due to their high ionic conductivity and the ductility-derived processability. However, it is imperative to address the issue of side reactions between carbon additive-based conductive agents and solid electrolytes. Irreversible reactions of solid electrolytes, stemming from narrow electrochemical stability window, lead to capacity fading of ASSBs. Previous research has explored conductive agents in the form of fibers with a smaller specific surface area or reducing the proportion of conductive agents. Nevertheless, these approaches have not provided a fundamental solution.Herein, we apply an oxide coating to the surface of carbon nanofiber conductive agents to prevent interfacial side reactions between the electrolyte and the conductive agent. Through computational screening among various oxide-based coating candidates, Li3PO4 is identified as possessing the highest chemical interfacial stability and superior ionic conductivity when interfaced with cathode active materials and solid electrolytes. This approach not only preserves the electronic percolation pathway essential for high-rate capability but also effectively suppress the decomposition of solid electrolytes through a stable ceramic layer. The efficacy of the Li3PO4 coating is demonstrated through enhanced ionic conductivity by up to 150% and improved rate capability and cycle performance in ASSBs, without significant loss of electronic conductivity in the composite cathode. This work introduces a novel concept in conductive agent modification, offering significant advantages in both ionic and electronic conductivity aspects.

Architecting Manganese Oxide Oxygen Reduction Electrocatalysts Adds New Function to Zinc–Air Cells

In aqueous alkaline electrolyte, why use platinum in the air cathode to electrocatalyze oxygen reduction (ORR) when the 2×2 tunnel polymorph of MnO2 (cryptomelane) is effective, more sustainable, and a lower cost catalyst? A polymorphic cousin, lamellar birnessite MnO2, also catalyzes ORR and is the morphology attained by sacrificially oxidizing the walls of carbon nanofoam papers (CNFPs) with permanganate thereby creating an architected catalyzed air cathode. Birnessite-painted CNFP (MnOx@CNFP) brings high areal capacity for pulse power through Mn4+/3+ redox-based capacitance, even while catalyzing ORR in primary zinc–air cells. The oxide spontaneously recovers the +4 charged state as residual molecular in the meso/macroporous electrode re-oxidizes the discharged +3 state. In powder-composite air cathodes, cryptomelane expressed as an ultraporous, covalently networked aerogel architecture sustains continuous high load demands in a primary zinc–air cell that the denser xerogel form of cryptomelane cannot. But in rechargeable zinc–air cells, manganese oxides are less effective electrocatalysts for oxygen evolution (OER), requiring high charging voltage that degrades the oxide coupled with parasitic oxidation reactions of electrolyte and carbon that limit cycle life. Formulating powder-composite air cathodes with cryptomelane aerogel and an OER electrocatalyst, such as Ni ferrite expressed as an aerogel, keeps charging voltage < 2 V while cryptomelane still dominates ORR catalysis for a higher discharge cell voltage. Versus a dendrite-suppressing zinc sponge anode, the cell using an air electrode formulated with two architected oxygen electrocatalysts delivers state-of-the-art low voltage hysteresis and power performance. The interdependent role catalytic activity and carbon stability play on cycle life point to the importance of cell metrics to rethink catalyst and electrode design. Preventing carbon corrosion, whether by replacing carbon with other electronic conduits or improving electrocatalyst activity, needs greater emphasis as a strategy for rechargeable zinc–air cells to achieve high total areal energy density.

(Invited) Organic Catalysis Promotor for Accelerating Oxygen Evolution Reaction Toward Advanced Water Electrolysis

As the concerns about energy and environmental issues rapidly increase, the requirements for developing renewable energy sources are highly demanded to achieve the carbon-neutrality by 2050. Among the suggested strategies for carbon neutrality, green hydrogen production via water electrolysis is treated as a promising breakthrough to alternate the currently used fossil fuel-based energy production since it utilizes clean and eco-friendly resources of water and electricity. However, there still remains a limitation of which mostly used noble metal-based catalyst materials such as iridium, and platinum result in severe carbon dioxide emission during production and recycling processes in addition to the extremely high cost and scarcity. Therefore, it is mandatory to minimize the noble metal contents in catalyst electrodes to ultimately reach carbon neutrality. Diverse approaches have been suggested to reduce the amount of noble metal contents such as developing non-noble metal catalysts and single-atom catalysts as well as designing electrode architecture for low loading on the support materials. Nonetheless, limited catalytic performances or increased process cost from suggested strategies still hinders the development of large-scale water electrolyzer. Herein, we suggest a novel concept of organic catalysis promotor as a strategy for minimizing noble metal contents in catalysts. Organic catalysis promotor as an additive in an electrolyte can enhance the hydrogen production efficiency with the spontaneous chemical interaction with the intermediate state of a catalyst during water electrolysis reaction, which can further result in reducing the required amount of noble metals for green hydrogen production. We developed the model organic catalysis promotor for oxygen evolution reaction in alkaline water electrolysis, and it successfully reduced overpotential of 70 mV at a current density of 100 mA cm-2 with only adding a slight amount of 1 mM organic catalysis promotor in KOH electrolyte. This catalysis promoting capability could be maintained even over a week, and the possibilities of further expansion of organic catalysis promotor material group and general applicability to representative oxygen evolution reaction catalysts were also proved. This novel concept of organic catalysis promotor has a great potential to be further expanded toward hydrogen evolution reaction promotion and acidic water electrolyzer. Furthermore, it can suggest a new breakthrough for the development of large-scale water electrolyzer with minimizing the noble metal contents in a sustainable and economical way.

Eco-Friendly and Cost-Effective Electrochemical Synthesis of High-Purity Lithium Hydroxide Monohydrate

In recent years, lithium compounds have been seen as energy materials of great commercial value as the global energy industry develops. The use of lithium-ion batteries (LIBs) in electric vehicles (EVs) is driving the global demand for lithium resources. While many studies have shown that EVs have environmental benefits over internal combustion engine vehicles, the impact of battery production is still uncertain. We need to dramatically reduce greenhouse gas (GHG) emission from the LIBs manufacturing process and raw battery material production. Typically, lithium compounds have been produced from hard rock minerals or continental brines. The former consumes large amounts of sulfuric acid and is more energy-intensive and expensive than the latter. When extracting lithium from conventional brine, we first produce technical-grade lithium carbonate (Li2CO3), which can then react with calcium hydroxide to produce battery-grade lithium hydroxide (LiOH·H2O). In the LCA study, the GHG emissions of producing Li2CO3 from brine were found to be between 2.7 and 3.1 tonne CO2e/tonne Li2CO3, while the GHG emissions of producing LiOH were more than twice as high, between 6.9 and 7.3 tonne CO2e/tonne LiOH·H2O. Therefore, there is a need to further reduce greenhouse gas emissions from the LiOH manufacturing process. In this study, we developed an eco-friendly and cost-effective process for producing high purity LiOH·H2O from Li2CO3 solution using a membrane-based water electrolysis reaction. This process significantly reduces the energy consumption of the LiOH manufacturing process. We investigated the impact of various operational variables on process efficiency, including solution concentration, current-voltage, and flow rate. The mechanism of LiOH synthesis, the role of membrane, and greenhouse gas emissions will be discussed.

Two-Dimensional, Multi-Reaction, and Multi-Species Porous Electrode Modeling of Metal Oxide Electroreduction with Applications in Nuclear Fuel Reprocessing and Iron Oxide Reduction

Many electrochemical processes involve the reduction of a porous solid metal oxide into pure metal such as the Fray-Farthing-Chen (FFC) Cambridge process 1 for titanium and ULCOWIN 2 process for iron. With optimal electrolysis cell designs, these processes would produce metal efficiently without energy losses to parasitic side reactions. Predictive modeling of the reaction rate (current) distribution underlying these processes can allow for increased energy efficiency and higher metal electrowinning yields. This would be beneficial to the fields of nuclear fuel reprocessing and sustainable metals production, which utilize electro-reduction of uranium oxides and iron oxides, respectively. This presentation will cover the development of a two-dimensional, multi-reaction model that simulates the current distribution during oxide reduction and models the potential profiles of both the metal oxide phase and the liquid electrolyte phase within the oxide pores. The model applies the concepts of porous electrode theory developed by Newman and Tobias 3 but modifies it to incorporate multiple reactions.4, 5 The model is then applied to uranium oxide reduction in a molten salt electrolyte, and aqueous processing of iron oxide ores for iron electrowinning. This modeling study helps establish the main controlling parameters for the current distribution uniformity, i.e., the solid electronic conductivity of the oxide phase, the liquid electrolyte conductivity of the molten (or aqueous) electrolyte, the tortuosity and porosity of the porous oxide matrix, and the exchange current densities of the metal oxide and the liquid electrolyte reactions. Experimentally measured current distribution profiles on a porous electrode comprising iron oxide particles will be shown as validation of model findings.References G. Z. Chen, D. J. Fray, and T. W. Farthing, Nature, 407 (6802), 361-364 (2000).M. Abdul Quader, S. Ahmed, S. Z. Dawal, and Y. Nukman, Renewable and Sustainable Energy Reviews, 55 537-549 (2016).J. S. Newman and C. W. Tobias, Journal of The Electrochemical Society, 109 (12), 1183 (1962).D. R. Baker and M. W. Verbrugge, Journal of The Electrochemical Society, 165 (16), A3952-A3964 (2018).D. R. Baker, M. W. Verbrugge, and W. Gu, Journal of The Electrochemical Society, 166 (4), A521-A531 (2019).

Effect of the Lactation Phases on the Amplitude of Variation in Blood Serum Steroid Hormones and Some Hematochemical Analytes in Three Dairy Cow Breeds.

Lactation in dairy cows implies comprehensive endocrine and metabolic changes including a systemic electrolytic reaction. Previous studies have rarely considered these specific demands due to the influence of lactation periods. Therefore, this study aimed to assess the effects of early, middle, and late lactation phases on the dynamic changes in serum concentrations of progesterone (P4), 17β-oestradiol (E2), cortisol, and some electrolytes (Ca++, Mg++, Na+, K+, Cl-, Pi) and biochemical parameters (alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), creatine kinase (CK), total bilirubin, urea, and iron (Fe++) in 10 Holstein, 10 Brown Swiss, and 10 Modicana multiparous healthy dairy cows (4.2 ± 1.7 years of age) sampled at 60-day intervals throughout lactation. Lactation induced significant changes in the concentrations of P4, which peaked at >120-180 days, decreased at >240-300 days, and increased again after 300 days. Cortisol showed an opposite trend to P4, with concentrations progressively decreasing, except for the phase between >240 and 300 days, and a steep drop at >300 days compared to previous phases. Na+ concentrations showed the lowest values at 0-60 d and the highest ones at >180-240 days, whereas Mg++ showed the highest values at >60-120 d and the lowest at >300 d. Significant correlations were found between P4 with cortisol, Cl- and K+, and cortisol with Ca++ and LDH. Significant differences in average concentrations of AST, ALT, LDH, Ca++, Mg++, and Fe++ were observed among different dairy cow breeds. Understanding the dynamic changes in hormone levels, electrolytes, and biochemical parameters during different lactation phases, while considering breed differences in dairy cows, is crucial for improving herd health management and milk production in commercial dairy farms.