Cell Setup Research Articles

External Short-Circuit Scenarios under Different Mechanical Pressures Applied to Lithium-Ion Cells with Silicon-Dominant Anodes

Abstract The safety behavior of lithium-ion cells using high contents of silicon as new anode active material was barely investigated. This work investigates the short-circuit behavior of self-manufactured single-layered pouch cells using 70%wt microscale silicon and NCA cathodes in a novel dual reference cell setup consisting of a gold wire and a lithium metal reference electrode. Six cells were externally shortened at three different compression levels using a novel developed quasi-isothermal calorimetric shortcircuit test bench. The same current plateaus and transition zones were observed for all pressure settings, as reported in the literature for graphite-containing anodes. In addition, a direct dependency of the short-circuit intensity and the heat generation is measured for the differently compressed cells. This higher short-circuit intensity was quantitatively explained by the decreasing impedance at increased pressure levels. The built-in reference electrodes allow for monitoring of the negative terminal voltage, revealing potentials of up to 3:508 V versus Li+/Li and thus explaining the measured over-discharge in the range of ≈25% SoC. The post-mortem analysis reveals copper deposition on both electrodes and the separator, confirming the electrochemically measured over-discharge. Linear scans and potential trajectories reveal 3.379 V versus Li+/Li as oxidation potential for copper dissolution using copper||lithium-metal coin cells.

PH Dependence of Dihydroxyacetone Oxidation by Electrocatalytic Viologen Self-Assembled Monolayers on Gold Electrodes.

Carbohydrate fuel cells garner much research interest as the world's focus shifts from fossil fuels to renewable energy. Many catalyst options are available for carbohydrate fuel cell development, including enzymes and microbes, various metal-based catalysts, and natural or synthetic mediators. Research challenges include low power output, system fouling and poisoning, inefficient electron release, and complex mechanisms, with multiple pathways leading to low product selectivity. Here, we further investigate a novel approach to catalyze carbohydrate oxidation using Au electrodes with viologen self-assembled monolayers (SAMs). SAM-mediated fuel cells have the potential to address the challenges of other catalyst systems by protecting the electrode surface and controlling the local concentration and structure to increase current generation. The effects of increasing pH on dihydroxyacetone (DHA) oxidation by three viologen SAMs on Au electrodes are presented. Current and power generated during DHA oxidation at varying pH were measured and compared to those of bare Au performance. Two of the SAMs produced more current and power than bare Au at elevated pH. The SAM system produced more current and peak power per molecule than both dilute and concentrated homogeneous viologen systems in the same cell setup. These results demonstrate the benefits and limitations of electrodes modified with redox-active groups for the production of electricity from simple sugars and other carbohydrate sources. These results are encouraging for the development of new strategies for electrical power generation from renewable resources.

Development of surface-texturized black silicon through metal-assisted chemical etching and its application in the thermophotovoltaic field: a review and recommendation

Abstract The Shockley-Queisser limit poses a significant challenge in solar technology research, limiting the theoretical efficiency to around 30%. Thermophotovoltaic (TPV) systems have emerged as a solution by incorporating a thermal absorber in traditional solar cell setups to achieve total efficiency beyond the limits. The efficiency of the overall system heavily depends on the performance and quality of the thermal absorber, which absorbs photons from the heat source and transfers them to the TPV cell. However, complex and expensive fabrication processes have hindered widespread adoption of TPV technology. The well-established metal assisted chemical etching (MACE) method could be the best choice to mitigate these as it is a cost-effective, scalable, and mass-production-friendly process, which is widely used for surface texturization, creating nanostructures like nanopores, pyramids, and nanowires. MACE
technique is also suitable for producing highly efficient silicon-based thermal absorbers with over 90% absorption rate, which can contribute to increased total conversion efficiency. However, it does not come without challenges such as maintaining control over the etch rate in order to achieve uniformity. This paper comprehensively reviews the utilization of MACE for fabricating silicon-based thermal absorbers in TPV systems with the range of effective wavelengths of 600 – 2000 nm which corresponds to the energy level of 0.55 – 1.85 eV. The advantages and challenges of MACE, along with characterization techniques, are extensively discussed. By providing valuable insights, this paper aims to support researchers interested in advancing TPV technology.

An open source electrochemical channel flow cell setup for kinetics studies. Application to investigations on oxygen electrocatalysis.

An open source electrochemical channel flow cell setup for kinetics studies. Application to investigations on oxygen electrocatalysis.

Stereoselective Electrochemical Synthesis of E-Tetrasubstituted Haloalkenyl Chalcogenides.

Herein, we describe an electrochemical method for the synthesis of haloalkenyl chalcogenides from internal alkynes using hydrobromic and hydrochloric acids as halogenating agents, with the sole byproduct being hydrogen gas. This e-halochalcogenation protocol generates electrophilic chalcogenium species under mild conditions in a simple, undivided cell setup, enabling the synthesis of 25 examples of chloro- and bromovinyl selenides and sulfides with yields ranging from 10 % to 94 %, predominantly as the E-isomer. The synthetic utility of the halovinyl chalcogenides was demonstrated through various transformations, yielding densely functionalized tetra-substituted olefins. This underscores the versatility and efficiency of our method in assembling intricate molecular frameworks.

Innovative Study on Solar Energy Conversion and Storage Through Malachite Green + Ascorbic Acid + Sodium Lauryl Sulphate For Photogalvanics

Objective: To improve the output of photogalvanics (PG) cell. Methods: The specially designed H shaped PG cell was studied for better electrical outcomes. The PG cell setup consists of two electrode, digital pH meter, resistance key, carbon pot, and microammeter. The system consisting of Malachite Green (MCG), Ascorbic acid (AA), and Sodium Lauryl Sulphate (SLS) was examined in terms of photopotential (PP) and photocurrent (PC). Findings: The measured PC was 391.00 µA, while the observed PP was 926.00 mV. The finest and most dependable renewable energy option to help the world's population meet their energy requirements is solar energy. Novelty: Better results on Photo Galvanic (PG) cells are reported in the present research, helping to achieve the goal providing clean and sustainable energy. The intended electrical outcomes were obtained by using the MCG + AA + SLS, PG cell arrangement. Keywords: Malachite Green, Photogalvanics, Sodium Lauryl Sulphate, Ascorbic acid, Photopotential

Advanced characterization of alkaline water electrolysis through electrochemical impedance spectroscopy and polarization curves

Improved electrolyzer components are needed to make alkaline water electrolyzers more flexible and durable. The performance of these new components can be assessed through in situ electrochemical characterization in the form of polarization curves and electrochemical impedance spectroscopy (EIS). Presently, EIS is still mostly used for the IR-correction of the polarization curve, but more valuable information can be extracted. In this work we show how EIS data can be used to determine the dependence of ohmic resistance on current density, to derive anodic and cathodic Tafel slopes and exchange current densities from fitted charge transfer resistances and to derive anodic and cathodic capacitances from fitted constant phase elements. We do this for both a two electrode alkaline electrolysis flow cell setup as well as for a three electrode beaker type setup with 2D nickel electrodes. The presented tools can be used in performance studies of new and existing electrodes and membranes in alkaline water electrolysis.

Understanding the Impact of Gas Diffusion Layer Degradation on Water Inventory in Low Temperature PEM Fuel Cells for Heavy Duty Vehicles Application: Operando X-Ray and Neutron Imaging Study

Samples from two materials representing the condition at begin and end of life, were selected from testing of commercial, state-of-the-art PEM fuel cell stacks. Using small-area single cell setups specifically developed for visualization purposes, operando synchrotron and neutron imaging experiments to visualize water dynamics and distribution within these cells were performed. In this study, the effects of aging on water inventory in the gas diffusion layers throughout the lifespan of the cells are investigated. The findings provide insights into how aging influences water management, which is crucial for optimizing the performance and longevity of PEM fuel cells for heavy-duty applications.

Understanding the Impact of Gas Diffusion Layer Degradation on Water Inventory in Low Temperature PEM Fuel Cells for Heavy Duty Vehicles Application: Operando X-Ray and Neutron Imaging Study

Samples from two materials representing the condition at begin and end of life, were selected from testing of commercial, state-of-the-art PEM fuel cell stacks. Using small-area single cell setups specifically developed for visualization purposes, operando synchrotron and neutron imaging experiments to visualize water dynamics and distribution within these cells were performed. In this study, the effects of aging on water inventory in the gas diffusion layers throughout the lifespan of the cells are investigated. The findings provide insights into how aging influences water management, which is crucial for optimizing the performance and longevity of PEM fuel cells for heavy-duty applications.

Comprehensive 3E -energetic, economic, and environmental-analysis of a hybrid solar dish-Brayton engine and fuel cell system for green hydrogen and power generation

This work aims to assess the energy, economic, and environmental performance of a novel hybrid solar dish Bryton engine and fuel cell (SDBE-FC) system for generating green hydrogen and electricity. The system includes solar dish units, fuel cells, an electrolyzer, a converter, and a hydrogen storage tank. The study introduces a novel SDBE-FC system, replacing typical photovoltaic/fuel cell setups, to achieve higher efficiency and improved financial and environmental competitiveness. A vigorous energy-enviro-economic analysis is carried out using MATLAB/Simulink® to model system components. Key parameters have been analyzed, including the electrolyzer efficiency, flow rate, power, and the SDBE plant and FC stack's power, area, and efficiency. The total levelized cost of energy (LCOE) and the reduction in CO2 emissions are also calculated. Results showed that using 50 stacked fuel cells achieved an efficiency of 7%, increasing the number of staked fuel cells to 400 increased the efficiency by eightfold achieving a peak power of 297 kW. The efficiency and power output of the fuel cell decreased by 16% and 22.2%, respectively, when the operational temperature increased from 40 °C to 80 °C. Furthermore, LCOE as low as 0.218 US$/kWh was achieved using 25 SDBE units at 1100 °C. At 30 kW, the SDBE system produces 750 kW of power with 18.3% efficiency and occupies 4099.8 m2 as the temperature (Th) reaches to 1100 °C. The SDBE, with a rated power range of 15 kW–30 kW, achieved a 390.8% CO2 emissions reduction, amounting to 34,120.76 tons of CO2, when 25 SDBE units were utilized.

A novel binary composite of CuCoNi-MOF/MoO3 with exceptional capacitance as electrode material for supercapacitors

Metal-organic framework (MOF), a new type of electrode material with a porous structure, has shown promise as a good choice for supercapacitors in the next generation of energy storage devices. These research endeavors initiated the development of a doping technique and the creation of a composite material using solvothermal synthesis. This study involves the successful synthesis of CuCo-MOF and CuCoNi-MOF by introducing Co and Ni metals into the Cu-MOF. The CuCoNi-MOF is then combined with MoO3 to form a novel binary composite known as CuCoNi-MOF/MoO3. These prepared materials are then subjected to several physiochemical and electrochemical characterization techniques. The electrochemical characteristics of the prepared samples are estimated using a three-electrode cell setup. The analysis included cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge/discharge (GCD). The examination of the CV reveals that the binary composite CuCoNi-MOF/MoO3 exhibits exceptional capacitance (937.5 Fg−1 at 5 mVs−1) in comparison to the other materials that were synthesized. Moreover, the GCD study reveals that it has a capacity of 1364.69 Fg−1 at 0.5 Ag−1. Furthermore, it retained 91.5 % of its capacity after 5000 cycles demonstrating its exceptional stability. Owing to the exceptional electrochemical properties of CuCoNi-MOF/MoO3, it is employed as the positive electrode and activated carbon (ActC) as a negative electrode for device fabrication. The supercapattery (CuCoNi-MOF/MoO3||Act-C) showed an excellent specific capacitance of 218.83 Fg−1 at 1 Ag−1 along with an outstanding energy density of 59.57 Wh.kg−1 and power density of 704.9 W.kg−1. Moreover, the assembled supercapattery device shows remarkable stability of 95.2 % at 10 Ag−1 after 15,000 cycles.

Comparing Electrode Overpotential Contributions in Vrfbs Amongst Multiple Techniques

Redox flow batteries (RFBs) offer a potential remedy for the escalating need for energy storage amid the ongoing transition from carbon-intensive fossil energy to renewable energy sources. Yet, many RFB chemistries are shown to have low energy efficiencies which can be attributed, in part, to ineffective electrode materials. Identifying overpotential contributions from electrodes under operating conditions is a key step in understanding how to design better RFB electrodes Previously, three-electrode setups using rotating disk electrodes (RDE) were the effective technique at isolating overpotentials; however, this can only be accomplished by looking at one side of the RFB at a time. RDEs do not easily replicate the operational conditions of a power cell or the porous nature of carbon electrodes used in RFBs. Alongside the normal operation of an RFB, symmetry cells are another approach that can be utilized in quantifying the performance of electrodes. The advantage of a symmetrical cell setup allows us to monitor the overpotential contributions of two different electrodes in the same electrolyte concurrently. Membrane-based reference electrodes (MBRE), and other reference electrode integration concepts, allow us to use three-electrode techniques in operational RFB power cells. As a case study, we examined the effect of oxidative electrode treatments on the positive and negative side of the VRFB using multiple methods. While other studies have shown that an untreated negative electrode may be the key inhibitor in VRFB performance, we have quantified the overpotential at 50% state of charge to be 194 mV when 50 mA cm-2 is applied. After an oxidative treatment is applied to the negative electrode, the overpotential is reduced to 111 mV. Applying this to other techniques, we can compare the effectiveness of a non-symmetry cell setup vs. a symmetry cell setup, which displayed that oxidative treatment techniques appear to have an opposite effect on the positive electrode. A treated-positive electrode shows an overpotential of around 100 mV whereas an untreated-positive electrode only contributes 15 mV less of overpotential. These findings are further compared using common reference electrodes placed in the electrolyte tank, providing insights into the effectiveness of power cell techniques in improving RFB electrode performance.

Investigation of Anion Exchange Membrane Water Electrolysis Efficiencies at Cell Level Using Online Mass Spectrometry

In the future, water electrolysis (WE) will play a decisive role in the energy-efficient and sustainable production of green hydrogen. In this respect, anion exchange membrane water electrolysis (AEMWE) is a promising technology that combines the advantages of the already established alkaline and acidic water electrolysis systems. The alkaline environment makes it possible to replace precious metal catalysts with nickel or iron as cost-effective alternatives. At the same time, using an anion-conducting membrane instead of a porous separator enables higher current densities and flexible operation.1 In direct comparison to proton exchange membrane water electrolysis (PEMWE), durability and stability are still the main problems of AEMWE, but significant progress has been made in recent years. Electrochemical cell tests lasting a year and longer are available for the commercial AEMs Sustainion®2 and Aemion+®3. In addition, piperidinium-based membranes have now also been tested for 1000 hours.4 While the stability improvements of AEMWE are going in the right direction, the question remains to what extent the high efficiencies achieved in PEMWE can be matched. For the latter, the individual contributions to the cell voltage5, 6 and the expected gas permeations7, 8 at different current densities have already been studied in detail – an understanding that is still missing for AEMWE systems.Consequently, in this work, we want to give an insight into AEMWE efficiencies for a standard cell configuration. For this purpose, we used the novel PiperION® membrane and a scalable non-noble NiFe-LDH catalyst from Matteco as the anode catalyst in a self-designed 5 cm² cell setup. Furthermore, we set the focus on implementing product gas analysis using online mass spectrometry to investigate the faradaic efficiency and draw a conclusion on the gas-crossover mechanisms of the novel technology. Tracking the weight of our electrolyte reservoirs during operation additionally allowed us to analyze the water drag. Both phenomena were examined over a wide range of current densities from 0 to 5 A cm-2 at 70 °C and 1 M KOH to provide currently missing information for AEMWE development. References H. A. Miller, K. Bouzek, J. Hnat, S. Loos, C. I. Bernäcker, T. Weißgärber, L. Röntzsch and J. Meier-Haack, Sustainable Energy Fuels, 4(5), 2114–2133 (2020).B. Motealleh, Z. Liu, R. I. Masel, J. P. Sculley, Z. Richard Ni and L. Meroueh, Int. J. Hydrog. Energy, 46(5), 3379–3386 (2021).M. Moreno-González, P. Mardle, S. Zhu, B. Gholamkhass, S. Jones, N. Chen, B. Britton and S. Holdcroft, Journal of Power Sources Advances, 19, 100109 (2023).C. Hu, J. Y. Lee, Y. J. Lee, S. H. Kim, H. Hwang, K. Yoon, C. Park, S. Y. Lee and Y. M. Lee, Next Energy, 1(3), 100044 (2023). M. Suermann, T. J. Schmidt and F. N. Büchi, ECS Trans., 69(17), 1141–1148 (2015). M. Bernt and H. A. Gasteiger, J. Electrochem. Soc., 163(11), F3179-F3189 (2016). M. Bernt, J. Schröter, M. Möckl and H. A. Gasteiger, J. Electrochem. Soc., 167(12), 124502 (2020). P. Trinke, B. Bensmann and R. Hanke-Rauschenbach, Int. J. Hydrog. Energy, 42(21), 14355–14366 (2017).

Redox Stability Analysis of Co-Doped Barium Niobate Thin Films Via Cyclic Voltammetry

The electrochemical oxidative coupling of methane (E-OCM) to higher hydrocarbons, requires anodes that are stable under reducing conditions. We have previously demonstrated high activity with long term stability/durability for the perovskite anode BaMg0.33Nb0.67-xFexO3-δ (BMNF) while performing E-OCM1. Our group has also improved the total conductivity and activity of barium niobate perovskites via exchange of Mg for Ca (from 18 mS/cm-1 to 41 mS/cm-1), while also decreasing the Goldschmidt tolerance factor below 1 for increased cubic perovskite structural stability2. Perovskite metal oxide thin films can be produced with well-defined thicknesses and stoichiometries through pulsed laser deposition (PLD)3. These thin films are utilized in cyclic voltammetry experiments on YSZ substrates to further elucidate the chemical stability and oxygen sub-stoichiometry of high temperature SOFC/SOEC electrodes. Through application of reducing potentials to the electrode of interest, the voltage and current responses can be correlated to effective oxygen activities in which reduction of the electrode may occur. Usage of this technique with calcium and iron doped barium niobate perovskites (BaCa0.33Nb0.67-xFexO3-δ - BCNF) provides insights into the thermochemical stability and iron doping effects under highly reducing environments. The BCNF thin film electrodes were characterized via grazing incidence XRD and XRF for crystal structure and chemical composition. After initial characterization, cyclic voltammetry experiments were performed in a novel cell setup. These BCNF thin films show promise for evaluating stability mechanisms for E-OCM operation while providing details on compositional changes and oxygen loss of BCNF in reducing environments.

(Invited) Single-Atom Cu Catalysts for Electrochemical CO2 Reduction – Combining Theory, Synthesis and Electrochemical Characterization

Electrochemical CO2 reduction (CO2RR) is a leading sustainable approach for transforming atmospheric CO2 into valuable chemicals. This electrocatalytic process relies on a delicate balance of electron and proton transfer steps, resulting in the formation of diverse 1-carbon and some 2-carbon products, contingent on the surface properties. Extensive exploration of various transition metals for CO2RR has revealed that the binding strength of reaction intermediates on these metals significantly influences product selectivity. Notably, metals such as Au, Ag, Pd, Zn, Cd, Bi, Sn, and In, recognized for their activity in CO2RR, exhibit lower binding strengths for CO2 intermediates, leading to the predominant production of either HCOOH or CO as sole products. In contrast, Cu, with its moderate ability to bind CO2RR intermediates, yields multiple products during CO2RR, albeit with reduced selectivity [1]. Moreover, the overall efficiency of CO2 conversion is hampered by the simultaneous occurrence of the competing hydrogen evolution reaction (HER) at the potentials required for producing desired products. Thus, it is imperative to develop new, effective catalysts. Catalysts capable of suppressing HER while enhancing selectivity are essential for advancing the overall efficiency of CO2 conversion [2].Single-atom catalysts (SACs) are a relatively new class of materials that hold great promise due to their high specific activity and maximum atom utilization [3]. These catalysts often provide singular types of active sites, enhancing selectivity in reactions. However, the vast array of possible SACs, deployable on various supports, makes it impractical, if not possible, to use the traditional trial-and-error studies to yield high performing catalysts within reasonable timeframes. To navigate this complexity, theoretical investigations, especially DFT computations and machine learning techniques, have emerged as powerful tools. They can facilitate the identification of suitable catalyst structures and enable the precise engineering of atomic arrangement, therefore achieving targeted product formation from CO2 with enhanced conversion efficiency. Additionally, conventional synthesis methods suffer from various drawbacks, involving multiple steps, harsh conditions, and a lack of control over the metal site distribution in the carbon matrix, limiting the desired coordination structure [4, 5].Therefore, the work presented in this talk represents our combined experimental-theoretical effort. Specifically, Cu single atoms were strategically deposited onto defective carbon supports and systematically investigated for their performance as CO2RR electrocatalysts. These catalysts were inspired by DFT results showing how the product profile could be manipulated on catalyst surfaces, along with a prediction of the most likely products that would arise from the reaction.These catalysts were synthesized using a novel method denoted as switched solvent synthesis. This approach involves initially impregnating metals onto a carbon support, followed by switching the solvent from aqueous to an organic solvent with a higher dipole moment, and subsequently reducing the resulting mixture under an H2 environment. This innovative method offers notable advantages, enabling the efficient production of SACs in less time, at lower temperatures (~100-500 °C), and with high yields. In this study, Cu SACs were synthesized, and the influence of reaction parameters on the distribution of Cu metal atoms was systematically examined. The confirmation of SAC formation was achieved through various characterization techniques, including aberration-corrected STEM, XRD, and XPS.To assess the electrochemical activity and CO2 reduction abilities of the Cu SACs, electrochemical characterization techniques were employed under both He and CO2-saturated 0.1 M KHCO3 electrolytes. Furthermore, the product distribution and CO2 conversion efficiencies, including activity, stability, selectivity, and faradaic efficiency, of the Cu SACs were rigorously evaluated through electrolysis in a flow cell setup. Quantification of the results was performed using an integrated GC/MS instrument.

Efficient Electrochemical Reduction through Flow Cells Using Spherical-Polymer Based Carbon Supported Catalysts as Fixed-Bed Electrode

The transition to economically friendly feedstocks and the electrification of chemical synthesis reactions gained much attention in the recent years. To be able to compete with the conventional processes, it is crucial not only to concentrate on the electrochemical reactions itself but also to constantly improve the reactor concepts. A vast variety of designs are imaginable and already well-described – from a simple, undivided beaker cell setup to a divided flow cell with separate electrolytes at cathode and anode. [1] As electrode material not only flat metal electrodes are studied, but also the concept of using carbon supported metal nanoparticles is well-known to employ high dispersion to lower the total amount of required metal. [2,3] While there are already commercial flow reactors and electrodes available for electrosynthesis with flat standard electrodes, reactors using a fixed-bed of porous carbon with nanodispersed metals as electrode just recently started to attract attention. [4] Dealing with the pressure drop over the catalyst bed, while the electrical contact is still ensured, are key challenges for this reactor design. Spherical polymer-based carbons (SPBC) combine porous carbons properties with a high purity and especially spherical character. [5] While these advantages led already to commercial products for chromatographic applications (e.g. Carboxen®) the potential regarding flow-electrochemistry has not been leveraged. Key developments for this are reproducible synthesis procedures to deposit active metal on the SPBCs and the design of an electrochemical flow cell using these catalysts in a fixed-bed electrode configuration.The first part of this work presents the deposition of Cu through different impregnation and reduction procedures on a SPBC (Carboxen® 1032, 50 µm, Merck). The carbon was characterized by physisorption, TPD-MS, TPO, Raman and SEM. The resulting metal-impregnated carbon catalysts were additionally investigated regarding the metal loading. Using the applied impregnation and reduction parameters targeted metal loadings (3 – 20 wt%) could be well achieved. The second part focuses on the design and commissioning of a flow-cell for the application of the SPBC-supported catalysts as a fixed-bed at the cathode side. Electrochemical synthesis reactions are targeted in the cell and the reduction of 5-HMF to BHMF was chosen as the test reaction in this work. In the framework of the cell development multiple aspects not only regarding the construction but also reaction engineering issues had to be considered: material stability of the pump, fixation and pressure drop of catalyst bed, choice of electrolyte, effect of dissolved oxygen in the catholyte, optimal flow rate, reliable electrochemical protocol and selection of contact material. The latter has to be a compromise between chemical inertness and an enhanced electron transfer between the catalyst bed and the contact material (e.g. soft foil vs. hard metal). Figure 1A shows the current voltage characteristics of two possible contact materials (graphite foil, boron-doped diamond (BDD)) in the targeted electrolyte (0.5M borate buffer with 0.25M potassium chloride). Here, the graphite foil clearly shows a higher activity towards the hydrogen evolution reaction which may result in a less effective electrolysis later on. The comparison of BDD as contact material without and with a catalyst bed (Carboxen® 1032 loaded with 20 wt% Cu) resulted in a significant shift in the current voltage characteristic to lower overpotentials. Therefore, the electronic contact with the carbon bed is clearly enabled and the carbon spheres loaded with copper catalyze the reaction. Figure 1B presents the results of the test reaction with the conversion of the educt 5-HMF as well as the selectivity to the targeted product BHMF over the reaction time with BDD as contact material without and with a fixed bed of Cu/SPBC catalyst. The experiments prove full 5-HMF conversion within 23 h on stream in combination with a high selectivity towards BHMF with the catalyst bed. The mass-based productivity reaches values of up to 1.78 mmol h-1 gCu -1 and is therefore about 15 times higher compared to the use of conventional Cu foil (Pliterature = 0.11 mmol h-1 gCu -1 [6]). It is possible that due to the metal-support approach in the fixed-bed configuration, the copper is leveraged more efficiently and small amounts allow to provide sufficient metal surface area for the catalytic reaction.

La0.8Sr0.2CoO3 Electrocatalyst for Oxygen Evolution Reaction in Alkaline Electrolysis: From Powder to the Fuel Cell Application

In recent years, there has been a growing need for new renewable energy sources due to the rapid depletion of conventional energy sources and an escalating energy demand. Since environmental protection concerns are increasing, electrochemical processes are becoming increasingly essential [1]. Specifically, the focus has shifted towards storing energy in hydrogen and its subsequent conversion into on-demand electricity [2]. Here, hydrogen, generated via water electrolysis, serves as either an intermediary for generating energy carriers like liquid fuels or plays a key role as an energy carrier [3]. Despite significant efforts focused on enhancing electrolyzers for energy conversion, the progression towards practical application has encountered challenges stemming from differing catalyst development requisites in academic and industrial research. This study proposes a systematic approach for efficiently transitioning electrocatalysts from fundamental research to application readiness for alkaline oxygen evolution reactions.Herein, La0.8Sr0.2CoO3 was chosen as a catalyst and compared with the benchmark material NiFe2O4. Initially, the La0.8Sr0.2CoO3 catalyst was successfully synthesized by scalable spray-flame synthesis. Following this, various inks were formulated utilizing different binders (Nafion®, Naf; Sustainion®, Sus). The dispersion stability of La0.8Sr0.2CoO3 and commercial NiFe2O4 inks was investigated in the presence of Nafion and Sustainion using analytical centrifugation and transmittograms. Subsequently, these selected dispersions were applied onto nickel substrates via spray coating techniques, ensuring a homogeneous catalyst distribution. Finally, the La0.8Sr0.2CoO3 and NiFe2O4 catalysts were subjected to extensive electrochemical evaluations, including glassy carbon rotating disk electrode, scanning droplet cell (SDC), compression cell, flow cell, and zero-gap cell, to evaluate the material performance. SDC findings highlight the excellent uniformity in La0.8Sr0.2CoO3 electrodes and NiFe2O4-Sustainion (standard deviation < 11%). However, the NiFe2O4-Sustainion film experienced delamination, exhibiting a standard deviation of 28%. SDC experiments offer advantages over various half-cell techniques by enabling the detection of any inhomogeneities or coating defects within the catalytic film. Additionally, complementary compression and flow cell experiments provide detailed information on the chemical and mechanical stress parameters resembling those in a full cell configuration. In assessing industrial applicability, the catalytic materials were undergone examination within a scalable full cell under industrial conditions (500 mA/cm² and 60 °C) utilizing a zero-gap cell setup. The observed trend in the full cell for the coated electrodes is as follows: La0.8Sr0.2CoO3-Naf > La0.8Sr0.2CoO3-Sus > NiFe2O4-Sus > NiFe2O4-Naf.These findings achieved through a well-structured coherent workflow, enhance our knowledge of the electrocatalytic system and offer essential insights for implementing novel materials in large-scale industrial applications. REFERENCES: [1] M.-S. Park, J. Kim, K.J. Kim, J.-W. Lee, J.H. Kim, Y. Yamauchi, Porous nanoarchitectures of spinel-type transition metal oxides for electrochemical energy storage systems, Phys. Chem. Chem. Phys. 17 (2015) 30963–30977. https://doi.org/10.1039/C5CP05936D.[2] J.R. Varcoe, P. Atanassov, D.R. Dekel, A.M. Herring, M.A. Hickner, P.A. Kohl, A.R. Kucernak, W.E. Mustain, K. Nijmeijer, K. Scott, T. Xu, L. Zhuang, Anion-exchange membranes in electrochemical energy systems, Energy Environ. Sci. 7 (2014) 3135–3191. https://doi.org/10.1039/C4EE01303D.[3] C. Van Pham, D. Escalera-López, K. Mayrhofer, S. Cherevko, S. Thiele, Essentials of High Performance Water Electrolyzers – From Catalyst Layer Materials to Electrode Engineering, Adv. Energy Mater. 11 (2021) 2101998. https://doi.org/https://doi.org/10.1002/aenm.202101998.

Stability of Bipolar Plates in Proton Exchange Membrane Water Electrolysis: Dissolution Studies of Titanium and Stainless Steel

Due to its high current densities and fast system response proton exchange membrane water electrolysis (PEMWE) is an ideal system for green hydrogen production from renewable energies. However, its widespread use is still hindered by the high costs rendering the produced green hydrogen not competitive. Therefore, a cost reduction is highly needed. The bipolar plates (BPPs) are causing a colossal factor in material costs. They are usually produced from titanium and coated with even more expensive materials such as gold or platinum. A possible, cheaper alternative is stainless steel. However, it is suspected to suffer from corrosion leading to the leaching of cations that can poison the catalyst or membrane.[1] Thus, we investigated the stability of BPP materials, the currently used titanium, and its cheaper alternative stainless steel (316L).[2] Therefore, we use a modified scanning flow cell setup coupled to an inductively coupled plasma mass spectrometer for investigating the stability of both materials on-line, as well as with scanning electron microscopy. To mimic the conditions at the BPP under operation, deionized (DI) water and highly diluted (0.5 mM) H2SO4 are chosen as electrolytes combined with a sample temperature of 60 °C.For Ti, we show that the dissolution is negligible, whereas 316L corrodes. For 316L, in DI water mainly Cr dissolves, while in the H2SO4 solution, the dissolution is more pronounced, and all alloy components are detected. Besides the pH value, the applied potentials play a crucial for its stability. However, our findings suggest that the contamination for a typical full cell architecture remains below 1 ppm, even for the highest measured dissolution rate of SS 316L.These capabilities of on-line high-throughput stability tests for BPP materials are, furthermore, used to investigate the influence of contaminations, such as F- or Cl-, and of the temperature-dependence on the stability of 316L. These results give further insights into 316L stability as BPP material and therefore contribute to the development towards cost-effective PEMWE.[1] a) N. Rojas, M. Sánchez-Molina, G. Sevilla, E. Amores, E. Almandoz, J. Esparza, M. R. Cruz Vivas, C. Colominas, Int. J. Hydrogen Energy 2021, 46, 25929-25943; b) H. Becker, J. Murawski, D. V. Shinde, I. E. L. Stephens, G. Hinds, G. Smith, Sustain. Energy Fuels 2023, 7, 1565-1603.[2] L. Fiedler, T. C. Ma, B. Fritsch, J. H. Risse, M. Lechner, D. Dworschak, M. Merklein, K. J. J. Mayrhofer, A. Hutzler, ChemElectroChem 2023, e202300373. Figure 1

Developing Online ICP-MS Methodology for Examining Catalyst Degradation Dynamics during Electrochemical CO2 Reduction

The electrochemical CO2 reduction reaction (CO2RR) provides a path towards sustainable production of carbon-based fuels and chemicals, using renewable electricity to drive the conversion of CO2 into products such as ethylene, ethanol, and methane. A challenge limiting the implementation of CO2RR is catalyst stability during operation, and greater fundamental understanding is needed to uncover the governing physical, chemical, and electrochemical factors, as well as degradation mechanisms, operative under reducing conditions. One tool that can be used for conducting such fundamental studies is online inductively coupled plasma mass spectrometry (ICP-MS). In this study, an experimental framework was developed for using online ICP-MS for time-resolved degradation studies during CO2RR conditions. Using a customized flow cell setup, we coupled an ICP-MS to a potentiostat to simultaneously apply a potential or current while evaluating dynamics and degradation for both Au and Cu catalysts. Both ionic dissolution and degradation in the form of nanoparticle detachment can be detected and analyzed. The presence of nanoparticles is indicated by spikes in ICP-MS data. The intensity of the spikes is directly related to particle size. We used ICP-MS to determine particle mass, size distribution, and cumulative mass loss over time. We found the use of ICP-MS to obtain particle size distribution gave comparable results to transmission electron microscopy (TEM) determination of particle size distribution.Au foil as the CO2 reduction catalyst was used as a model system for detecting and quantifying degradation in situ using ICP-MS. We found Au degradation to occur in the form of nanoparticle detachment, with increasingly negative applied potential (0 V vs RHE to -1 V vs. RHE) in the presence of CO2 leading to increased number of nanoparticles in the electrolyte; however, no ionic dissolution was observed. In comparison, when the electrolyte was saturated with N2, nanoparticles detached from the electrode at a lower rate than in CO2-saturated conditions. We also examined Cu degradation under the same conditions as the Au system. Cu degradation occurs as both ionic dissolution and nanoparticle detachment, but under all conditions, Cu has less nanoparticle detachment and cumulative mass loss due to nanoparticles than Au. The developed experimental framework in this study would be translatable to a variety of electrocatalytic reactions and environments. Examination of catalyst degradation behavior in situ, including non-traditional degradation mechanisms such as nanoparticle detachment from bulk materials, can be used to obtain greater fundamental understanding of degradation mechanisms and rational design of materials with improved stability.

Evaluation of Nickel-Iron (Oxy)Hydroxide Catalysts in Varied Electrode Geometries Under Industrially Realistic Conditions for Enhanced Alkaline Water Electrolysis

In pursuit of realizing a hydrogen-based economy, the challenge lies in enhancing the efficiency of crucial water electrolysis technologies. Alkaline water electrolysis (AWE) holds promise as an ecologically friendly method for H2 production, primarily due to its capacity for employing non-precious metals as electrocatalysts, in contrast to more costly options which can only switch to noble metals such as ruthenium or iridium. However, this technology faces a significant challenge arising from the sluggish kinetics of the oxygen evolution reaction (OER), which constrains the overall efficiency. [1] Furthermore, the limited stability of many OER catalysts alternatives developed at lab scale and less harsh conditions poses a substantial obstacle to the commercialization of this technology.[2] To overcome this issue, the development of highly active OER catalysts that maintain their activity under industrial conditions is of major importance explaining the growing attention that this topic is gaining in literature. Nevertheless, most of the reported systems are tested at low current densities under easily manageable conditions in the laboratory (≤ 100 mA cm-2, 1 M KOH, RT). Without disagreeing that this approach is necessary to identify promising options among the numerous catalyst systems, it is not sufficient when competing with existing technologies that already achieve high current densities. In this context, we investigate a low-cost, abundantly available non-precious metal based OER-catalyst under industrially relevant conditions (≤ 1.2 A cm-2, 30 wt.-% KOH, 80 °C). The synthesis is based on a multistep galvanic deposition method introduced by Wu et al [3], receiving a highly porous NiFeOOH catalyst. Addressing the complexity of the multiphase process of AWE that involves gas-liquid-solid interfaces, the catalyst system is transferred to numerous nickel electrodes with different 3D geometries (plain woven mesh, knitted mesh, expanded metal mesh) for the investigation of their impact on bubble formation and detachment. To further optimize the catalyst system a variation of the iron content with respect to its’ molar fraction relatively to nickel has been carried out from x(Fe)=0 to x(Fe)=0.75, which after synthesis were first examined using SEM and EDS. The structure can be considered as pompom-shaped particles, forming a porous framework, as can be seen exemplarily in Figure 1a) on a knitted nickel-wire mesh coated with NiFeOOH. Observing variations in iron content, it becomes evident that a higher iron content results in larger particle sizes, thereby altering pore sizes. However, the surface morphologies of each catalyst until a molar fraction x(Fe)=0.5 is reached, can be considered as very similar. When comparing the SEM images of the mesh with a molar fraction x(Fe)=0.75 to the other molar fractions, a secondary phase becomes apparent on the surface. Notably, the porous structure persists within the crystalline phase. It could be shown by EDS that the target values for the molar fractions set in the galvanic bath and the actual molar fractions nearly show no deviations. Further, a uniform dispersion of Ni, Fe and O is observed.The electrochemical investigation of the prepared catalysts was done in a 3-electrode PTFE beaker cell setup in 30 wt % KOH and at 80 °C. The measurement protocol we introduce consists of galvanostatic steps between 0-1.2 A cm-2. The stability is tested chronopotentiometrically as well by maintaining a current density of 500 mA cm-2 for 100 h. It becomes apparent that no optimum is reached in the tested range of iron content and that the potential continues to drop as the molar fraction of Fe increases, achieving the lowest potential with 1.38 V vs. RHE at 50 mA cm-2 and 1.42 V vs. RHE at 750 mA cm-2 with x(Fe)=0.75. It could be further proved that the NiFeOOH catalyst with x(Fe)=0.75 is a highly stable catalyst, resulting in a potential increase of 27 mV over 100 h of testing at 500 mA cm-2, making it to an appropriate OER catalyst for the application in the AWE. The highly porous structure is maintained after testing, proved by SEM imaging. The iron contents after testing are also very similar, which means that there is almost no iron loss in the coating. For the different tested electrode geometries coated with NiFeOOH (x(Fe)=0.5), similar activity is observed, shown in Figure 1b) with a ranging potential between 1.38 V to 1.41 V vs. RHE at 50 mA cm-2 and 1.42 V to 1.45 V vs. RHE at 750 mA cm-2.[1] a) Cao et al., Energy Environ. Sci. 2012 b) Zhao et al., ACS Chemical Reviews 2023.[2] Zeng et al., Journal of Energy Chemistry 2022.[3] Wu et al., Applied Surface Science 2021. Figure 1