Electrode Assembly Research Articles

Recent Progress in Materials Design and Fabrication Techniques for Membrane Electrode Assembly in Proton Exchange Membrane Fuel Cells

Proton Exchange Membrane Fuel Cells (PEMFCs) are widely regarded as promising clean energy technologies due to their high energy conversion efficiency, low environmental impact, and versatile application potential in transportation, stationary power, and portable devices. Central to the operation and performance of PEMFCs are advancements in materials and manufacturing processes that directly influence their efficiency, durability, and scalability. This review provides a comprehensive overview of recent progress in these areas, emphasizing the critical role of membrane electrode assembly (MEA) technology and its constituent components, including catalyst layers, membranes, and gas diffusion layers (GDLs). The MEA, as the heart of PEMFCs, has seen significant innovations in its structure and manufacturing methodologies to ensure optimal performance and durability. At the material level, catalyst layer advancements, including the development of platinum-group metal catalysts and cost-effective non-precious alternatives, have focused on improving catalytic activity, durability, and mass transport. Similarly, the evolution of membranes, particularly advancements in perfluorosulfonic acid membranes and alternative hydrocarbon-based or composite materials, has addressed challenges related to proton conductivity, mechanical stability, and operation under harsh conditions such as low humidity or high temperature. Additionally, innovations in gas diffusion layers have optimized their porosity, hydrophobicity, and structural properties, ensuring efficient reactant and product transport within the cell. By examining these interrelated aspects of PEMFC development, this review aims to provide a holistic understanding of the state of the art in PEMFC materials and manufacturing technologies, offering insights for future research and the practical implementation of high-performance fuel cells.

Platinum-Nickel@High-Entropy Alloy Core@Satellite Nanowires as Efficient Bifunctional Electrocatalysts for PEMFC.

The optimized composition and precisely tailored structure configuration play critical roles in enhancing the catalytic reaction kinetics. Here we report a distinctive core@satellite strategy for designing the advanced platinum-nickel@platinum-nickel-copper-cobalt-indium high-entropy alloy nanowires (Pt3Ni@HEA NWs) as efficient bifunctional catalysts in the proton exchange membrane fuel cell. Impressively, the Pt3Ni@HEA NWs/C shows 19.4/15.3 times higher mass/specific activity than that of commercial Pt/C for the oxygen reduction reaction. More importantly, synchronously as the cathodic and anodic catalysts, it can achieve a high membrane electrode assembly power density of 1653.5 mW cm-2 and long-term stability (only 3.9% voltage loss) for 280 h, largely outperforming those of commercial Pt/C. The weakened Pt-CO binding strength, quick removal of CO with linear adsorption, and favorable CO adsorption form contribute to the high performance of Pt3Ni@HEA NWs/C. This core@satellite strategy provides a new paradigm to develop the comprehensively efficient Pt-based functional catalysts for fuel cells and beyond.

Active Hydroxyl-Mediated Preferential Cleavage of Carbon-Carbon Bonds in Electrocatalytic Glycerol Oxidation.

Electrocatalytic glycerol oxidation reaction (GOR) to produce high-value formic acid (FA) is hindered by high formation potential of active species and sluggish C-C bond cleavage kinetics. Herein, Ni single-atom (NiSA) and Co single-atom (CoSA) dual sites anchored on nitrogen-doped carbon nanotubes embedded with Ni0.1Co0.9 alloy (Ni0.1Co0.9@NiSACoSA-NCNTs) are constructed for electrochemical GOR. Remarkably, it can reach 10 mA cm-2 at a low potential of 1.15 V versus the reversible hydrogen electrode (vs. RHE) and realize a high formate selectivity of 91.3% even at high glycerol conversion of 99.8% at 1.45 V vs. RHE. The GOR mechanism and pathway are systematically elucidated via experimental analyses and theoretical calculations. It is revealed that the active hydroxyl (*OH) can be produced during the GOR. The NiSA, CoSA, and Ni0.1Co0.9 synergistically optimizes the electronic structure of CoSA active sites, reducing the energy barriers of *OH-mediated cleavage of C-C bonds and dehydrogenation of C1 intermediates. This decreases the number of reaction intermediates and reaction steps of GOR-to-FA, thus increasing the formate production efficiency. After coupling GOR with hydrogen evolution reaction in a membrane electrode assembly cell, 14.26 g of formate and 23.10 L of H2 are produced at 100 mA cm-2 for 108 h.

Electrochemical Sensor for Hydrogen Leakage Detection at Room Temperature.

The use of hydrogen as fuel presents many safety challenges due to its flammability and explosive nature, combined with its lack of color, taste, and odor. The purpose of this paper is to present an electrochemical sensor that can achieve rapid and accurate detection of hydrogen leakage. This paper presents both the component elements of the sensor, like sensing material, sensing element, and signal conditioning, as well as the electronic protection and signaling module of the critical concentrations of H2. The sensing material consists of a catalyst type Vulcan XC72 40% Pt, from FuelCellStore, (Bryan, TX, USA). The sensing element is based on a membrane electrode assembly (MEA) system that includes a cathode electrode, an ion-conducting membrane type Nafion 117, from FuelCellStore, (Bryan, TX, USA). and an anode electrode mounted in a coin cell type CR2016, from Xiamen Tob New Energy Technology Co., Ltd, (Xiamen City, Fujian Province, China). The electronic block for electrical signal conditioning, which is delivered by the sensing element, uses an INA111, from Burr-Brown by Texas Instruments Corporation, (Dallas, TX, USA). instrumentation operational amplifier. The main characteristics of the electrochemical sensor for hydrogen leakage detection are operation at room temperature so it does not require a heater, maximum amperometric response time of 1 s, fast recovery time of maximum 1 s, and extended range of hydrogen concentrations detection in a range of up to 20%.

Surface borate layer dramatically enhances the stability of NiFe-layered double hydroxide for alkaline seawater oxidation

Seawater electrolysis presents a sustainable approach for producing green hydrogen using renewable energy sources. However, chloride ions (Cl−) and their derivatives significantly reduce the durability of anode catalysts, severely hindering their practical application. In this work, we developed a borate (Bi) modified NiFe layered double hydroxide on nickel foam (NiFe LDH@NiFe-Bi/NF) to blocks Cl− and mitigates chlorine reactions during alkaline seawater oxidation (ASO). In situ electrochemical spectroscopic studies show that the Bi layer effectively promotes NiOOH formation, thereby enhancing oxygen evolution reaction (OER) activity. Specifically, the B4O72−-rich anionic overlayer effectively prevents Cl− adsorption and thus protect the active site during ASO. As a result, NiFe LDH@NiFe-Bi/NF requires a lower overpotential (ƞ) of 354 mV to achieve an industrial current density (j) of 1000 mA cm−2 compared to NiFe LDH/NF, which requires 407 mV, in a 1 M KOH + seawater. Notably, NiFe LDH@NiFe-Bi/NF exhibits exceptional long-term electrochemical durability, maintaining stable operation for 600 h at a j of 1000 mA cm−2 in alkaline seawater. Additionally, membrane electrode assembly fabricated with NiFe LDH@NiFe-Bi/NF requires lower ƞ to reach the same voltages than Pt/C/NF||RuO2/NF. Furthermore, Pt/C/NF||NiFe LDH@NiFe-Bi/NF operates at 300 mA cm−2 for 150 h without significant activity degradation.

Nanomechanical and nanoelectrical analysis of the proton exchange membrane water electrolyzer anode – impact of reinforcement fibers and porous transport layer

An operated reinforced membrane electrode assembly anode was analyzed with high resolution. The fiber-reinforcement provided long-term stability, while nanomechanical and nanoelectrical aging was especially observed at porous transport layer marks.

Water state variation of membrane electrode assemblies during shutdown purge of proton exchange membrane fuel cells based on fast electrochemical impedance spectroscopy measurements

Water state variation of membrane electrode assemblies during shutdown purge of proton exchange membrane fuel cells based on fast electrochemical impedance spectroscopy measurements

Development and application of ordered membrane electrode assemblies for water electrolysis.

With the development of hydrogen energy, there has been increasing attention toward fuel cells and water electrolysis. Among them, the zero-gap membrane electrode assembly (MEA) serves as an important triple-phase reaction site that determines the performance and efficiency of the reaction system. The development of efficient and durable MEAs plays a crucial role in the development of hydrogen energy. Consequently, a great deal of effort has been devoted to developing ordered MEAs that can effectively increase catalyst utilization, maximize triple-phase boundaries, enhance mass transfer and improve stability. The research progress of ordered MEAs in recent advances is highlighted, involving hydrogen fuel cells and low temperature water electrolysis technology. Firstly, the fundamental scientific understanding and structural characteristics of MEAs based on one-dimensional nanostructures such as nanowires, nanotubes and nanofibers are summarized. Then, the classification, preparation and development of ordered MEAs based on three-dimensional structures are summarized. Finally, this review presents current challenges and proposes future research on ordered MEAs and offers potential solutions to overcome these obstacles.

In Situ Quantification of Transition Metal Cation Leaching from a Pt-Alloy Cathode Catalyst in a PEM Fuel Cell

The application of Pt-alloy cathode catalysts for proton exchange membrane fuel cells (PEMFCs) is hampered by the leaching of the alloyed transition metal into the ionomer phase of the membrane electrode assembly (MEA). To date, accelerated stress tests used to assess the degradation of Pt-alloy catalysts lack non-destructive, facile diagnostics to quantify transition metal leaching in an operating PEMFC. Here, we present a method based on electrochemical impedance spectroscopy that exploits the high sensitivity of the high frequency resistance (HFR) at low relative humidity (RH) to quantify transition metal cation contamination. A series of model MEAs with varying fractions of protons intentionally exchanged by Co2+ cations was fabricated. Based on these, we identified the HFR at 30% RH and zero current (i.e., at a homogenous Co2+ distribution in the ionomer phase) as a robust measure of Co2+ contamination. A calibration curve that correlates the HFR at 30% RH to the fraction of protons displaced by Co2+ in the model MEAs could be established, which then allowed quantitative tracking of the Co leached from a PtxCo/C cathode catalyst, both at the beginning-of-test (∼6%) and after 100,000 voltage cycles (∼30%). Capabilities and limitations of this method for Pt-alloy catalyst testing are discussed.

Laser scribed proton exchange membranes for enhanced fuel cell performance and stability

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) offer solutions to challenges intrinsic to low-temperature PEMFCs, such as complex water management, fuel inflexibility, and thermal integration. However, they are hindered by phosphoric acid (PA) leaching and catalyst migration, which destabilize the critical three-phase interface within the membrane electrode assembly (MEA). This study presents an innovative approach to enhance HT-PEMFC performance through membrane modification using picosecond laser scribing, which optimises the three-phase interface by forming a graphene-like structure that mitigates PA leaching. Our results demonstrate that laser-induced modification of PA-doped membranes, particularly on the cathode side, significantly enhances the performance and durability of HT-PEMFCs, achieving a peak power density of 817.2 mW cm⁻² after accelerated stress testing, representing a notable 58.2% increase compared to untreated membranes. Furthermore, a comprehensive three-dimensional multi-physics model, based on X-ray micro-computed tomography data, was employed to visualise and quantify the impact of this laser treatment on the dynamic electrochemical processes within the MEA. Hence, this work provides both a scalable methodology to stabilise an important future membrane technology, and a clear mechanistic understanding of how this targeted laser modification acts to optimise the three-phase interface of HT-PEMFCs, which can have impact across a wide array of applications.

Heating dictates the scalability of CO2 electrolyzer types.

Electrochemical CO2 reduction offers a promising method of converting renewable electrical energy into valuable hydrocarbon compounds vital to hard-to-abate sectors. Significant progress has been made on the lab scale, but scale-up demonstrations remain limited. Because of the low energy efficiency of CO2 reduction, we suspect that significant thermal gradients may develop in industrially relevant dimensions. We describe here a model prediction for non-isothermal behavior beyond the typical 1D models to illustrate the severity of heating at larger scales. We develop a 2D model for two membrane electrode assembly (MEA) CO2 electrolyzers; a liquid anolyte fed MEA (exchange MEA) and a fully gas fed configuration (full MEA). Our results indicate that full MEA configurations exhibit very poor electrochemical performance at moderately larger scales due to non-isothermal effects. Heating results in severe membrane dehydration, which induces large Ohmic losses in the membrane, resulting in a sharp decline in the current density along the flow direction. In contrast, the anolyte employed in the exchange MEA configuration is effective in preventing large thermal gradients. Membrane dehydration is not a problem for the exchange MEA configuration, leading to a nearly constant current density over the entire length of the modeled domain, and indicating that exchange MEA configurations are well suited for scale-up. Our results additionally indicate that a balance between faster kinetics, higher ionic conductivity, smaller pH gradients and lower CO2 solubility causes an optimum operating temperature between 60 and 70 °C.

Microenvironment Regulation to Unlock Platinum Catalyst Activity in Membrane Electrode Assemblies

Microenvironment Regulation to Unlock Platinum Catalyst Activity in Membrane Electrode Assemblies

In Situ Reconstructed Hydroxyl-Rich Atomic-Thin Bi2O2CO3 Enables Ampere-Scale Synthesis of Formate from CO2 with Activated Water Dissociation.

Renewable electricity-driven CO2 electroreduction provides a promising route toward carbon neutrality and sustainable chemical production. Nevertheless, the viability of this route faces constraints of catalytic efficiency and durability in near-neutral electrolytes at industrial-scale current densities, mechanistically originating from unfavorable accommodation of *H species from water dissociation. Herein, a new strategy is reported to accelerate water dissociation by the rich surface hydroxyl on bismuth subcarbonate nanosheets in situ electrochemical transformed from bismuth hydroxide nanotube precursors. This catalyst enables the electrosynthesis of formate at current densities up to 1000mA cm-2 with >96% faradaic efficiencies in flow cells, and a 200h durable membrane electrode assembly in a dilute near-neutral environment. Combined kinetic studies, in situ characterizations, and theoretical calculations reveal that the atomic thickness strengthens the hydroxyl adsorption, and with a highly localized electron configuration, the hydroxyl-functionalized surface is more affinitive to oxygenated species, thus lowering the barrier for water dissociation and the crucial hydrogenation step in the proton-coupled electron transfer from *OCHO to *HCOOH.

High-Performance Pure Water-Fed Anion Exchange Membrane Water Electrolysis with Patterned Membrane via Mechanical Stress and Hydration-Mediated Patterning Technique.

Despite rapid advancements in anion exchange membrane water electrolysis (AEMWE) technology, achieving pure water-fed AEMWE remains critical for system simplification and cost reduction. Under pure water-fed conditions, electrochemical reactions occur solely at active sites connected to ionic networks. This study introduces an eco-friendly patterning technique leveraging membrane swelling properties by applying mechanical stress during dehydration under fixed constraints. The method increases active sites by creating additional hydroxide ion pathways at the membrane-electrode interface, eliminating the need for additional ionomers in the electrode. This innovation facilitates ion conduction via locally shortened pathways. Membrane electrode assemblies (MEAs) with patterned commercial membranes demonstrated significantly improved performance and durability compared to MEAs with conventional catalyst-coated substrates and flat membranes under pure water-fed conditions. The universal applicability of this technique was confirmed using in-house fabricated anion exchange membranes, achieving exceptional current densities of 13.7 A cm-2 at 2.0 V in 1.0 M potassium hydroxide (KOH) and 2.8 A cm-2 at 2.0 V in pure water at 60°C. Furthermore, the scalability of the technique was demonstrated through successful fabrication and operation of large-area cells. These findings highlight the potential of this patterning method to advance AEMWE technology, enabling practical applications under pure water-fed conditions.

Negatively Charged Pt Atoms on Pd Nanocubes for an Enhanced Hydrogen Oxidation Performance in a Membrane Electrode Assembly

Negatively Charged Pt Atoms on Pd Nanocubes for an Enhanced Hydrogen Oxidation Performance in a Membrane Electrode Assembly

Fabrication and surface characterization of a novel approach for membrane electrode assembly using Nafion/PPy electrochemically coated with copper, nickel and silver

Fabrication and surface characterization of a novel approach for membrane electrode assembly using <scp>Nafion</scp>/<scp>PPy</scp> electrochemically coated with copper, nickel and silver

Silver‐Based Supportless Membrane Electrode Assemblies for Electrochemical CO2 Reduction

ABSTRACTMost commonly, electrochemical CO2 reduction is performed in a three‐compartment setup employing gas diffusion electrodes (GDEs) to decrease mass transport limitations of the gaseous reactant CO2 to the reaction interface. However recently, there has been a rising number of investigations on suitable membrane electrode assemblies (MEAs) to overcome ohmic potential losses caused by the electrolyte gaps in the systems. While the significant majority of MEAs exhibited in literature is based on catalyst‐coated gas diffusion layers, this work presents an approach that does not require a likewise support. On the basis of a catalyst suspension similar to mixtures already employed for GDE production on industrial level, a method to directly transfer the resulting catalyst layers to the membrane is developed. The Faradaic efficiency of carbon monoxide, i.e. target product formation of GDEs manufactured according to a similar procedure, can be matched or even exceeded for individual modifications of the exchange MEAs. Simultaneously, the cell potentials can be remarkably decreased in this setup. By gradual adaptation of the fabrication procedure, the influence of important manufacturing parameters is unraveled, also discussing the effect of hydrogen permeation through the membrane.

Constructing Highly Porous Low Iridium Anode Catalysts Via Dealloying for Proton Exchange Membrane Water Electrolyzers.

Iridium (Ir) is the most active and durable anode catalyst for the oxygen evolution reaction (OER) for proton exchange membrane water electrolyzers (PEMWEs). However, their large-scale applications are hindered by high costs and scarcity of Ir. Lowering Ir loadings below 1.0 mgcm-2 causes significantly reduced PEMWE performance and durability. Therefore, developing efficient low Ir-based catalysts is critical to widely commercializing PEMWEs. Herein, an approach is presented for designing porous Ir metal aerogel (MA) catalysts via chemically dealloying IrCu alloys. The unique hierarchical pore structures and multiple channels of the Ir MA catalyst significantly increase electrochemical surface area (ECSA) and enhance OER activity compared to conventional Ir black catalysts, providing an effective solution to design low-Ir catalysts with improved Ir utilization and enhanced stability. An optimized membrane electrode assembly (MEA) with an Ir loading of 0.5 mgIr cm-2 generated 2.0 A cm-2 at 1.79V, higher than the Ir black at a loading of 2.0 mgIr cm-2 (1.63 A cm-2). The low-Ir MEA demonstrated an acceptable decay rate of ≈40 µV h-1 during durability tests at 0.5 (>1200 h) and 2.0 A cm-2 (400 h), outperforming the commercial Ir-based MEA (175 µV h-1 at 2.0 mgIr cm-2).

Ferrocene-Functionalized Atomically Precise Metal Clusters Exhibit Synergistically Enhanced Performance for CO2 Electroreduction.

The integration of organometallic compounds with metal nanoparticles can, in principle, generate hybrid nanocatalysts endowed with augmented functionality, presenting substantial promise for catalytic applications. Herein, we synthesize an atomically precise metal cluster (Ag9Cu6) catalyst integrated with alkynylferrocene molecules (Ag9Cu6-Fc). This hybrid catalyst design facilitates a continuous electron transfer channel via an ethynyl bridge and establishes a distinctive local chemical environment, resulting in remarkably enhanced catalytic activity in CO2 electroreduction. The Ag9Cu6-Fc catalyst achieves a record-high product selectivity of CO Faradaic efficiency of 100 % and an industrial-level CO partial current density of -680 mA/cm2, surpassing the performance of the Ag9Cu6 cluster (62 % and -230 mA/cm2, respectively) without ferrocene functionalization in a membrane electrode assembly cell. Operando experimental and computational findings offer valuable insights into the role of ferrocene functionalization in synergistically improving the catalytic performance of metal clusters, propelling the advancement of metallic-organometallic hybrid nanoparticles for energy conversion technologies.

Industry-Level Electrocatalytic CO2 to CO Enabled by 2D Mesoporous Ni Single Atom Catalysts.

Electrocatalytic CO2 reduction reaction (eCO2RR) has captivated widespread attentions, yet achieving the requisite efficiency, selectivity and stability for industrial applications poses a persistent challenge. Here, we report the synthesis of 2D mesoporous Ni single atom catalysts in N-doped carbon framework via a bottom-up interfacial assembly strategy. The 2D mesoporous Ni-N-C catalyst showcases an ultrathin thickness (~6.7 nm) with well-distributed 5 to 40 nm-width mesopores in plane and a high surface area. As a result, the Ni single atom sites with a high density (~6.0 wt %) are almost completely exposed and can be accessible, and the mass transfer can be greatly promoted even at high current densities. Thus, a high current density of 446 mA cm-2 with >95 % CO selectivity in a flow cell can be obtained. Concurrently, the catalyst demonstrates an impressive stability, maintaining a 50-hours continuous electrolysis in the membrane electrode assembly test and achieving an energy efficiency of 42 %. Finite element analysis reveals that the 2D mesoporous design enhances CO2 diffusion, ensuring efficient adsorption and swift CO desorption at high current densities. Our study paves a way for the fabrication of 2D mesoporous single atom catalysts with nearly 100 % accessibility and expedited mass transport.