Exchange Membrane Water Electrolysis Cell Research Articles

NdMn1.5Ru0.5O5, a high-performance electrocatalyst with low Ru content for acidic oxygen evolution reaction

A mixed oxide with the crystal structure of the DyMn2O5 family, namely NdMn1.5Ru0.5O5, is reported active for the oxygen evolution reaction (OER) in acidic media. NdMn1.5Ru0.5O5 displays high OER activity of 500 A gRu−1 at 1.5 V. Moreover, is more stable than most Ru oxides reported to date, remaining active for more than 500 cycles between 1.1. and 1.7 V at low scan rate of 10 mV s−1. The high activity and stability are attributed to the Ru cations, as NdMn2O5 exhibits very low OER activity. NdMn1.5Ru0.5O5 has particularly short Ru–Ru distances of 2.60 Å, a value close to the Ru–Ru metallic distances around 2.642 Å. The high activity and durability of NdMn1.5Ru0.5O5 for the OER are also demonstrated in a proton exchange membrane water electrolysis cell by producing a low-loaded anode electrode with 0.5 mgRucm−2. The cell achieves 1.97 V at 0.5 A cm−2, consistent with the performances reported for Ru-based catalysts but with lower Ru loading. This performance is maintained during 100 h of operation. Additionally, NdMn1.5Ru0.5O5 displays visible ORR activity in acidic media, recording an onset potential of 0.85 V at 0.1 mA cm−2. It is noteworthy to highlight the extreme rarity of bifunctional ORR/OER catalysts acidic media.

Development of an ultra-thin electrode for the oxygen evolution reaction in proton exchange membrane water electrolyzers

Noble metal electrocatalysts are highly preferred for the oxygen evolution reaction (OER) in a proton exchange membrane water electrolysis cell (PEMWE) due to their exceptional catalytic activity and stability. This study proposes a novel thin electrode (NTE) design to enhance the performance of noble metal electrocatalysts for the OER in PEMWE. The NTE utilizes a thin porous transport layer for the direct deposition of Iridium (Ir). Unlike conventional gas diffusion electrodes with deep porous structures that underutilize the catalyst due to limited triple-phase boundary conditions, the flat NTEs with straight-through pores overcome this restriction. The paper compares two deposition methods, electroplating and sputter coating. The in-situ electrochemical properties of NTEs with varying Ir loadings (0.06–1.01 mg cm−2) are investigated. The electroplated NTE demonstrates excellent mass activity, achieving 5.05 A mg−1 at 1.6 V and 80 °C. The NTE exhibits a simple fabrication process and low cost while significantly improving catalyst mass activity. Additionally, the NTE reduces electrode thickness from hundreds of micrometers to only 25 μm. This concept holds great promise for the future advancement of compact and high-efficiency PEMWE electrodes, resulting in reduced cost, volume, and mass of both the electrode itself and the overall system.

A Proton exchange membrane water electrolysis cell model for analyzing the effects of liquid water supply characteristics on cell performance

Proton exchange membrane water electrolyzers (PEMWE) have significant potential for green, high-purity hydrogen production. This study proposes a pseudo-two-dimensional cell-level model that considers all the physical characteristics involved in water electrolysis (WE), such as electron transport in the electrodes, proton transport in the membrane electrode assembly (MEA), water transport between the anode and cathode, gas diffusion in the porous electrodes, two-phase transport in the porous electrodes, and flow channel (FC), including the channel pressure drop and heat conduction across the cell. Liquid water dispersion at the electrode/channel interface is proposed based on a geometrical analysis of the bubble patterns inside the anode channel. The model was validated against the experimental data. The simulation results showed the effects of the liquid water supply characteristics on the cell operation, demonstrating that uniform water, temperature, and pressure distributions on the cell are required for higher performance. Furthermore, efficiency maps with operating constraints under different conditions provide basic guidelines for determining the optimum point of PEMWE operation. The proposed model is appropriate for extensive analysis of physical phenomena inside the PEMWE and rapid simulation for cell optimization.

Multi-objective optimization of channel structure for a proton exchange membrane water electrolysis cell

The flow field dominates the process of mass transport and distribution inside the proton exchange membrane water electrolysis cell (PEMEC). Initially, a three-dimensional and non-isothermal PEMEC channel model was estimated to investigate the impact of channel height and width. Based on these results, a complete PEMEC model with a parallel flow-field pattern was developed, and the channel heights and widths of the model were optimized using a genetic algorithm (GA). Compared to the original model, the optimized model decreased the pressure drop by 34.97% at a lower voltage. In addition, because of the optimized flow-field pattern, the optimized model improves the current density on the proton exchange membrane as well as the gas holdup situation in a partial position in the cathode gas diffusion layer.

Activating RuOCo Interaction on the a-Co(OH)2 @Ru Interface for Accelerating the Volmer Step of Alkaline Hydrogen Evolution.

The state-of-the-art active hydrogen evolution reaction (HER) catalysts in acid electrolytes generally lose considerable catalytic performance in alkaline electrolytes mainly due to the additional water dissociation step. Designing composite materials is an effective strategy to accelerate alkaline water electrolysis by optimizing the electronic structure of materials. Here, different phases of Co(OH)2 -supported Ru clusters (α/β-Co(OH)2 @Ru) are prepared for enabling a highly efficient electrocatalytic HER performance in alkaline solution. The prepared α-Co(OH)2 nanosheets facilitate the loading of uniform and high-density Ru clusters and the formed highly active RuOCo bonds at the interface. The synergistic interaction endows the hybrid catalyst with low overpotential of 33mV at 10mA cm-2 . Moreover, the homemade anion exchange membrane water electrolysis cell based on α-Co(OH)2 @Ru affords a cell voltage of 2V to drive a current density of 270mA cm-2 and performs stably during continuous operation for over 100h. Density functional theory calculations demonstrate that active RuOCo bonds in α-Co(OH)2 @Ru optimize the energy barriers for H2 O dissociation and OH- desorption to facilitate the Volmer reaction step. This work offers a strategy for designing interfacial chemical bonds for high electrocatalytic activity.

Highly active and stable OER electrocatalysts derived from Sr2MIrO6 for proton exchange membrane water electrolyzers

Proton exchange membrane water electrolysis is a promising technology to produce green hydrogen from renewables, as it can efficiently achieve high current densities. Lowering iridium amount in oxygen evolution reaction electrocatalysts is critical for achieving cost-effective production of green hydrogen. In this work, we develop catalysts from Ir double perovskites. Sr2CaIrO6 achieves 10 mA cm−2 at only 1.48 V. The surface of the perovskite reconstructs when immersed in an acidic electrolyte and during the first catalytic cycles, resulting in a stable surface conformed by short-range order edge-sharing IrO6 octahedra arranged in an open structure responsible for the high performance. A proton exchange membrane water electrolysis cell is developed with Sr2CaIrO6 as anode and low Ir loading (0.4 mgIr cm−2). The cell achieves 2.40 V at 6 A cm−2 (overload) and no loss in performance at a constant 2 A cm−2 (nominal load). Thus, reducing Ir use without compromising efficiency and lifetime.

Performance Comparison of Proton Exchange Membrane Water Electrolysis Cell Using Channel and PTL Flow Fields through Three-Dimensional Two-Phase Flow Simulation.

Water electrolysis technology is required to overcome the intermittency of renewable energy sources. Among various water electrolysis methods, the proton exchange membrane water electrolysis (PEMWE) cell has the advantages of a fast response and high current density. However, high capital costs have hindered the commercialization of PEMWE; therefore, it is important to lower the price of bipolar plates, which make PEMWE expensive. In addition, since the flow field inscribed in the bipolar plate significantly influences the performance, it is necessary to design the enhanced pattern. A three-dimensional two-phase flow model was used to analyze the two-phase flow and electrochemical reactions of the PEMWE anode. In order to compare the experimental results with the simulation, experiments were conducted according to the flow rate, and the results were in good agreement. First, as a result of comparing the performance of the channel and PTL (porous transport layer) flow fields, the channel flow field showed better performance than the PTL flow field. For the channel flow field, the higher the ratio of the channel width-to-rib width and the permeability of PTL, the performance got better. In the case of the PTL flow field, with the increased capillary pressure, the performance improved even if the PTL permeability decreased. Next, the direction of gravity affected the performance only when the channel flow field was used, and the X+ and Z+ directions were optimal for the performance. Finally, increasing the inlet flow rate could reduce the difference in performance between the channel and PTL flow fields, but the pressure drop gradually increased.

Studying Performance and Kinetic Differences between Various Anode Electrodes in Proton Exchange Membrane Water Electrolysis Cell.

The electrode, as one of the most critical components in a proton exchange membrane water electrolysis (PEMWE) cell for hydrogen production, has a significant impact on cell performance. Electrodes that are fabricated via various techniques may exhibit different morphologies or properties, which might change the kinetics and resistances of the PEMWE. In this study, we have successfully fabricated several electrodes by different techniques, and the effects of electrode coating methods (ultrasonic spray, blade coating, and rod coating), hot press, and decal transfer processes are comprehensively investigated. The performance differences between various electrodes are due to kinetic or high frequency resistance changes, while the influences are not significant, with the biggest deviation of about 26 mV at 2.0 A cm−2. In addition, the effects of catalyst ink compositions, including ionomer to catalyst ratio (0.1 to 0.3), water to alcohol ratio (1:1 to 3:1), and catalyst weight percentage (10% to 30%), are also studied, and the electrodes’ performance variations are less than 10 mV at 2.0 A cm−2. The results show that the PEMWE electrode has superior compatibility and redundancy, which demonstrates the high flexibility of the electrode and its applicability for large-scale manufacturing.

Lattice Boltzmann simulations of gas bubble transport in proton exchange membrane water electrolysis cells

Gas/liquid two-phase transport is the key fundamental scientific issue in the proton exchange membrane (PEM) water electrolysis cell, which has important effects on the overall performance of water electrolysis and microstructure optimization. In this study, a combination of the lattice Boltzmann two-phase model and the QSGS numerical method was used to numerically model the porous diffusion layer and the micro-channel structure, and investigate the effects of porosity and wettability properties on the gas/liquid two-phase transport process. Simulation results show that the value of porosity will obviously affect the association and distribution pattern of solid particles inside the porous diffusion layer, and the reduction of porosity will cause the association part of solid particles to be narrower and longer, resulting in complex and variable pore channels. Some closed pore channels will appear inside the diffusion layer, which is not conducive to the smooth transmission of gas bubbles. In addition, the increase of contact angle will enhance the interaction force between the bubble and the solid wall, making it difficult for the bubble to fall off from the solid surface. Moreover, the increased interaction force will slow down the sliding speed of gas bubbles, which will result in the fusion of more gas bubbles and increase the risk of blocking the flow micro-channel. This study has initially grasped the mechanisms of micro/meso scale gas bubble transport in the PEM water electrolysis cell, which will provide theoretical basis for the optimized development of high-performance water electrolysis system for hydrogen production.

Effect of Gravity and Various Operating Conditions on Proton Exchange Membrane Water Electrolysis Cell Performance.

Water electrolysis is an eco-friendly method for the utilization of renewable energy sources which provide intermittent power supply. Proton exchange membrane water electrolysis (PEMWE) has a high efficiency in this regard. However, the two-phase flow of water and oxygen at the anode side causes performance degradation, and various operating conditions affect the performance of PEMWE. In this study, the effects of four control parameters (operating temperature, flow rate, cell orientation, and pattern of the channel) on the performance of PEMWE were investigated. The effects of the operating conditions on its performance were examined using a 25 cm2 single-cell. Evaluation tests were conducted using in situ methods such as polarization curves and electrochemical impedance spectroscopy. The results demonstrated that a high operating temperature and low flow rate reduce the activation and ohmic losses, and thereby enhance the performance of PEMWE. Additionally, the cell orientation affects the performance of PEMWE owing to the variation in the two-phase flow regime. It was observed that the slope of specific sections in the polarization curve rapidly increases at a specific cell voltage.

Internal Microscopic Diagnosis of Accelerated Aging of Proton Exchange Membrane Water Electrolysis Cell Stack.

The hydrogen production reaction of the proton exchange membrane (PEM) water electrolysis cell stack is the reverse reaction of the fuel cell, but the water electrolysis operation requires high pressure, and the high pressure decomposes hydrogen molecules, thus aging or causing failure in the water electrolysis cell stack. In addition, there are five important physical parameters (current, voltage, flow, pressure and temperature) inside the water electrolysis cell stack, which can change the performance and shorten the life of the cell stack. However, the present techniques obtain data only by external simulation or single measurement; they cannot collect the internal real data in operation instantly and accurately. This study discusses the causes for aging or failure, and develops an internal real-time microscopic diagnosis tool for accelerated aging of the PEM water electrolysis cell stack. A flexible integrated (current, voltage, flow, pressure and temperature) microsensor applicable to the inside (high voltage and electrochemical environment) of the PEM water electrolysis cell stack is developed by using micro-electro-mechanical systems (MEMS) technology; it is embedded in the PEM water electrolysis cell stack for microscopic diagnosis of accelerated aging, and 100-h durability and reliability tests are performed. The distribution of important physical parameters inside the PEM water electrolysis cell stack can be measured instantly and accurately, so as to adjust it to the optimal operating conditions, and the local aging and failure problems are discussed.

Iron Contamination and Local Distribution within a 50 Cm Single-Channel Proton Exchange Membrane Water Electrolysis Cell

Proton exchange membrane water electrolysis (PEMWE) will play a major role in the clean and versatile energy conversion in the near future.[1] Offering scalable solutions of PEMWE are of high industrial interest and have to provide a sufficient durability and reliability.[2] To achieve this, a better understanding of the impact of contamination on the PEMWE performance is very crucial. In this context, the membrane electrode assembly (MEA) is susceptible to several degradation processes like metallic cations (Fe3+/2+ stemmed from tubing). In particular, soluble and reduced iron species forming by Fenton reaction might attack via radicals the MEA.[3,4] Hence, analyzing impurities and their resulting impacts on e.g. the proton transport resistance and degradation mechanisms at different length scales and local distributions are of large interest.In this work, the influence of spatially resolved iron contamination in MEAs on the cell performance has been investigated using a 50 cm single-channel PEMWE cell equipped with local current density measurement setup.[5] Adding defined amounts of FeSO4 via the anode inlet feed, the changes on the three main regimes of overpotentials, i.e. kinetic, ohmic and mass transport, is correlated with the current density mapping as well as local and global electrochemical impedance spectroscopy (EIS) measurements. Ex-situ scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) are used to detect the distribution and agglomeration of iron species within the MEA.With this combined approach of electrochemical and ex-situ physical methods, the contamination pathways and their effects of (spatially resolved) iron contamination on the overall performance of MEA are investigated as a function of degree of contamination and operating conditions. Especially, the (spatially resolved) overpotential-specific degradation processes along the 0.5 m channel, which mimic a technically relevant stack size, allow us to conclude on the optimum design of MEA, targeting use of mitigation strategies and development of accelerated stress test protocols.[1] M.A. Pellow, C.J.M. Emmott, C.J. Barnhart, S.M. Benson, Energy Environ. Sci. 8 (2015) 1938-1952.[2] P.K. Shen, C.-Y. Wang, S.P. Jiang, X. Sun, J. Zhang, Electrochemical Energy: Advanced Materials and Technologies, CRC Press, 2015.[3] X. Wang, L. Zhang, G. Li, G. Zhang, Z.-G. Shao, B. Yi, Electrochim. Acta 158(2015) 253-257.[4] C. Rozain, P. Millet, Electrochim. Acta 131 (2014) 160e167.[5] C. Immerz, B. Bensmann, P. Trinke, M. Suermann, R. Hanke-Rauschenbach, JECS 165 (16) (2018)

Single Nanometer-Sized NiFe-Layered Double Hydroxides as Anode Catalyst in Anion Exchange Membrane Water Electrolysis Cell with Energy Conversion Efficiency of 74.7% at 1.0 A cm–2

We used a liquid phase reaction to synthesize a nickel (Ni) and iron (Fe)-containing layered double hydroxide (NiFe-LDH), having a lateral size less than 10 nm. A chelating agent introduced into th...

On the Effect of Clamping Pressure and Methods on the Current Distribution of a Proton Exchange Membrane Water Electrolyzer

The heterogeneity of the local current distribution (LCD) of proton exchange membrane water electrolysis cell (PEMWE) has a significant effect on its degradation. More heterogeneous LCD leads to faster degradation rate and vice versa. LCD is affected by the amount of clamping pressure and methods. In this work, LCD is measured at the cathode side of 50 cm2 PEMWE cell at different clamping pressures and methods; bolting the cell with 8 bolts around the active area and compressing the overall area of the end plate using pneumatic set-up. S++® Current Scan Lin is used for LCD measurements, where the segmented plate is placed between the current distributor and flow field plate. Initial results show that, increasing the torque in the bolted cell results in heterogeneous LCD and vice versa for the pneumatically compressed cell. Also it is concluded that, higher PEMWE cell performance does not necessary mean homogeneous LCD.

Non-Precious Electrocatalysts for Anion Exchange Membrane Water Electrolysis Cell

The hydrogen has been recognized as a clean, nonpolluting and unlimited energy source that can solve fossil fuel depletion and environmental pollution problems at the same time. Water electrolysis has been the most attractive technology in a way to produce hydrogen, because it does not emit any pollutants compared to other methods such as natural gas steam reforming and coal gasification etc. In order to improve efficiency and durability of the water electrolysis, comprehensive studies for highly active and stable electrocatalysts have been performed. The platinum group metal (PGM; Pt, Ru, Pd, Rh, etc.) and its oxide catalysts showed a higher activity and stability compared with other non-precious catalysts in operating condition. It is necessary to develop non-precious catalysts with high activity and durability because the PGM catalysts are expensive materials with insufficient it’s reserves. In the water electrolysis field, the numerous researchers have been focused on the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) because the OER and HER are a key process (slow kinetics) compared with other resistances such as bubble, electrolyte, diaphragm, membrane, etc. On a point of view of a catalyst, slow kinetics and the use of precious metal (PGM) for high performance should be solved to popularize water electrolysis. The target of this study is the development of non-precious catalysts with high activity via simple and efficient synthesis method that is a wet-chemical based method. The Ni-LaCeO/C (HER catalysts) and CuCoO (OER catalyst) were synthesized through the co-precipitation with oxidation and reduction heat treatment. The catalysts were characterized by various physicochemical analyses such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). To investigate electrocatalytic properties of prepared catalysts, we carried out electrooxidation activity measurements such as cyclic voltammetry (CV), linear sweep voltammetry (LSV), long-term stability test, and electrochemical impedance spectroscopy (EIS). The relationship between their physicochemical properties and electrocatalytic activities will be explored and discussed.

Hydrogen production with a designed clathrochelate-based electrocatalytic materials: Synthesis, X-ray structure and redox-properties of the iron cage complexes with pendant (poly)aryl-terminated ribbed substituents

Cage iron(II) complexes with one, two or six terminal (poly)aromatic group(s), designed for effective physical adsorption on the carbonaceous substrates, were prepared by nucleophilic substitution of their mono-, di- and hexachloroclathrochelate precursors with 3-arene-1(9)-yl-propane-1 thiolate anions. Their cyclic voltammograms contain the single Fe2+/+ reduction wave in the cathodic potential range and two oxidation waves in the anodic potential range, assigned to a metal-centered Fe2+/3+ process and to oxidation of their arylalkylsulfide groups, respectively. Iron(II) hexaphenanthrenylsulfide clathrochelate with six terminal polyaromatic groups was either immobilized or impregnated on the cathode of gas diffusion electrode and its electrochemical activity with regard to hydrogen evolution reaction (HER) was tested in a proton exchange membrane water electrolysis cell for hydrogen production. It was shown that effective immobilization of this (pre)catalyst on the surface of appropriate carbonaceous electrode materials can be successfully used for improving an efficiency of clathrochelate-based hydrogen-producing systems.

음이온 교환막 알칼리 수전해를 위한 운전 조건 및 구성요소의 최적화

The hydrogen has been recognized as a clean, nonpolluting and unlimited energy source that can solve fossil fuel depletion and environmental pollution problems at the same time. Water electrolysis has been the most attractive technology in a way to produce hydrogen because it does not emit any pollutants compared to other method such as natural gas steam reforming and coal gasification etc. In order to improve efficiency and durability of the water electrolysis, comprehensive studies for highly active and stable electrocatalysts have been performed. The platinum group metal (PGM; Pt, Ru, Pd, Rh, etc.) electrocatalysts indicated a higher activity and stability compared with other transition metals in harsh condition such as acid solution. It is necessary to develop inexpensive non-noble metal catalysts such as transition metal oxides because the PGM catalysts is expensive materials with insufficient it's reserves. The optimization of operating parameter and the components is also important factor to develop an efficient water electrolysis cell. In this study, we optimized the operating parameter and components such as the type of AEM and density of gas diffusion layer (GDL) and the temperature/concentration of the electrolyte solution for the anion exchange membrane water electrolysis cell (AEMWEC) with the transition metal oxide alloy anode and cathode electrocatalysts. The maximum current density was <TEX>$345.8mA/cm^2$</TEX> with parameter and component optimization.