Membrane Water Electrolysis Research Articles

Effect of Anion-Conducting Electrolytes in Pore-Filling Membranes on Performance and Durability in Water Electrolysis

This study examines the effect of the structural characteristics of anion-conducting monomers within pore-filling anion exchange membranes on the performance and durability of anion exchange membrane water electrolysis. Analysis reveals that acrylamide- and acrylate-based membranes show optimal performance without methyl groups, with acrylamide-based membranes outperforming their acrylate counterparts in current density, particularly at 1.8 V. The AC-AA and AC-MAA monomers demonstrate durability, with AC-MAA showing enhanced alkaline stability, likely due to the presence of a methyl group, resulting in an increase rate of 746.6 μV/h compared to AC-AA’s 1150 μV/h. This study also shows that a commercial membrane exhibits a decrease rate of 3116 μV/h, underscoring the pore-filling membrane’s superior durability. Furthermore, the findings highlight that pore-filling membrane technology enables better durability and performance in electrolysis environments compared to the commercial homogeneous membrane, particularly when alkaline conditions are present. This research provides a foundation for designing high-performance, durable membranes for efficient hydrogen production, particularly under water electrolysis conditions.

2D MOF Structure Tuning Atomic Ru Sites for Efficient and Robust Proton Exchange Membrane Water Electrolysis.

Developing cost-effective ruthenium (Ru)-based HER electrocatalysts as alternatives to commercial Pt/C is crucial for the advancement of proton exchange membrane water electrolysis (PEMWE). However, the strong hydrogen adsorption of Ru-based catalysts restricts its activity. Herein, a strategy is reported to tune the electronic structure and improve mass transfer by implanting Ru atoms onto the (002) facet of two-dimensional zeolitic imidazolate framework-67(Ru@LZIF(002)) to optimize the d-band center (εd) of Ru and the hydrogen spillover behavior. Benefiting from the ultrathin nanosheet structure and optimized εd of Ru, the over-strong H adsorption energy is weakened and the electron/mass transfer is facilitated. Ru@LZIF(002) exhibits an overpotential of 9.2mV at 10mA cm-2 and a long-lasting stability of 35 days at 100mA cm-2. The mass activity and price activity of Ru@LZIF(002) is 2.9 and 14.7 times higher than Pt/C, respectively. More impressively, Ru@LZIF(002) delivers a cell voltage of 2.01V at a high current density of 4 A cm-2 in PEMWE. The excellent long-term durability of 1200 hours operating at 4 A cm-2 with an ultralow decay rate of 7.5 × 10-3mV h-1 has been achieved, making it promising as a cost-effective alternative to Pt/C catalyst for PEMWE applications.

Dynamic-Cycling Zinc Sites Promote Ruthenium Oxide for Sub-Ampere Electrochemical Water Oxidation.

Although iridium-based electrocatalysts are commonly regarded as the sole stable operating acidic oxygen evolution reaction (OER) catalysts in proton-exchange membrane water electrolysis (PEMWE) devices, their exorbitant cost and scarcity severely restrict their widespread application. Herein, we introduce a promising alternative to iridium: zinc-doped ruthenium dioxide (TE-Zn/RuO2), which exhibits remarkable and enduring activity for acidic OER. In situ characterizations elucidate that the dynamic cycling of zinc dopants serves as both electron acceptors and donors, facilitating the activation of Ru sites at low overpotentials while thwarting peroxidation at high overpotentials, thus concurrently achieving heightened activity and robust stability. Additionally, the incorporation of zinc induces weakened Ru-O covalency, thereby stabling *OOH intermediates and instigating a sustained adsorbate evolution mechanism, dramatically stabilizing the RuO2 lattice. Importantly, the TE-Zn/RuO2 catalyst as an anode exhibits good stability over 300 h at a water-splitting current of 500 mA cm-2 in the PEMWE device, underscoring its considerable promise for practical applications.

Pioneering Built-In Interfacial Electric Field for Enhanced Anion Exchange Membrane Water Electrolysis.

As a half-reaction in anion exchange membrane water electrolysis (AEMWE) technology, the hydrogen evolution reaction (HER) at the cathode is severely hindered by the sluggish reaction kinetics involved in additional water dissociation step, which results in large overpotentials and low energy conversion efficiency. Here, we develop a nano-heterostructure composed of ultra-thin W5N4 shells over Ni3N nanoparticles (Ni3N@W5N4) as efficient catalysts, in which built-in interfacial electric field (BIEF) is created owing to the distinct lattice arrangements and work functions of biphasic metal nitrides. The BIEF facilitates the electron localization around the interface and enables high valence W and more exposed binding sites in the surface W5N4 shell for accelerating the water dissociation step, ultimately leading to a remarkable reduction in the energy barriers of RDS from 1.40 eV to 0.26 eV. Theoretical calculations and operando X-ray absorption spectroscopy analysis results demonstrated that surface W5N4 serves as the active species for HER. Moreover, the ultra-thin shell characteristics enable the optimized W5N4 with enhanced intrinsic catalytic activity to be fully exposed as active sites. Consequently, the Ni3N@W5N4 exhibits exceptional performance in alkaline HER (60 mV@10 mA cm-2) and remarkable long-term stability (500 mA cm-2 for 100 hours). When employed as the cathode in the AEMWE device, the synthesized Ni3N@W5N4 demonstrates stable performance for 90 hours at a current density of 1 A cm-2.

Pioneering Built‐In Interfacial Electric Field for Enhanced Anion Exchange Membrane Water Electrolysis

AbstractAs a half‐reaction in anion exchange membrane water electrolysis (AEMWE) technology, the hydrogen evolution reaction (HER) at the cathode is severely hindered by the sluggish reaction kinetics involved in additional water dissociation step, which results in large overpotentials and low energy conversion efficiency. Here, we develop a nano‐heterostructure composed of ultra‐thin W5N4 shells over Ni3N nanoparticles (Ni3N@W5N4) as efficient catalysts, in which built‐in interfacial electric field (BIEF) is created owing to the distinct lattice arrangements and work functions of biphasic metal nitrides. The BIEF facilitates the electron localization around the interface and enables high valence W and more exposed binding sites in the surface W5N4 shell for accelerating the water dissociation step, ultimately leading to a remarkable reduction in the energy barriers of RDS from 1.40 eV to 0.26 eV. Theoretical calculations and operando X‐ray absorption spectroscopy analysis results demonstrated that surface W5N4 serves as the active species for HER. Moreover, the ultra‐thin shell characteristics enable the optimized W5N4 with enhanced intrinsic catalytic activity to be fully exposed as active sites. Consequently, the Ni3N@W5N4 exhibits exceptional performance in alkaline HER (60 mV@10 mA cm−2) and remarkable long‐term stability (500 mA cm−2 for 100 hours). When employed as the cathode in the AEMWE device, the synthesized Ni3N@W5N4 demonstrates stable performance for 90 hours at a current density of 1 A cm−2.

Synthesis and performance of cross-linked poly(aryl ether nitrile) anion exchange membranes with dense cations and flexible side-chain structures for water electrolysis

Anion exchange membranes (AEMs) are the core components in anion exchange membrane water electrolysis (AEMWE), which play crucial role and affect the performance of AEMWE. In this work, a series of cross-linked poly(aryl ether nitrile) anion exchange membranes (CPAEN-dDQA-x) with dense cations and flexible side-chain structures are synthesized. By introducing multiple modification elements into the polymer structure simultaneously, the ion conductivity, dimensional stability, and alkali resistance stability of the prepared AEMs are effectively improved and balanced. The representative CPAEN-dDQA-0.25 showed water absorption of only 27.6 %, swelling rate of 11.2 %, and conductivity of 115.37 mS/cm at 80°C. The IEC and conductivity retention value of CPAEN-dDQA-0.25 after in 2 M NaOH solution at 80°C for 480 h were up to 86.2 % and 82 %, respectively. Meanwhile, the current density of the water electrolysis cell based on CPAEN-dDQA-0.25 is up to 477.0 mA/cm2 in 1 M KOH and 2.2 V, and its voltage don’t has significant change after 480 h of operation at a constant current density of 500 mA/cm2.

Intermittent polarity inversion of stainless-steel paired electrodes for efficient and durable water electrolysis

Designing robust and cost-effective catalysts through straightforward and replicable techniques is crucial for advancing water electrolysis. In this study, we introduce a dynamic polarization control method for the continuous activation of stainless steel (SS) substrates to achieve high water-splitting performance and durability. By applying periodic inverted current density during high-current–density operation (0.5 or 1 A cm−2) on bare SS adopted as both cathode and anode substrates, a NiFe-based oxide structure favorable for the hydrogen evolution reaction is formed at the cathode, while a Fe-incorporated NiOOH structure with high efficacy for the oxygen evolution reaction develops at the anode. Implemented in an anion exchange membrane water electrolysis system, this inverted polarization approach applied for the SS paired electrolyzer system successfully maintains a cell voltage of approximately 1.9 V for 500 h at a current density of 1 A cm−2 using bare SS for both electrodes.

Polysaccharide derived Ru/Ni HER catalysts for long-run anion exchange membrane water electrolysis

Polysaccharide derived Ru/Ni HER catalysts for long-run anion exchange membrane water electrolysis

Quantitative analysis of fluid heat transfer behavior in a proton exchange membrane water electrolysis cell

The development of heat transfer models for proton exchange membrane water electrolysis (PEMWE) cells is necessary to enhance their efficiency, durability, and safety. Although modeling efforts have indicated that the heat transfer to fluids is significant, the magnitude of the heat transfer and mechanism have not been adequately studied. To fill this knowledge gap, we quantified the amounts of heat transferred in a thermally insulated cell and associated system. We found that heat transfer to the inflow water accounted for the majority of heat transfer to the fluids, and the rise of the membrane (CCM + PTL) temperature was due mainly to deterioration of the distribution of water at high current density. The sensible heat transfer and the resistive heat were directly proportional to each other, and the quantity of latent heat transfer could be influenced by resistive heating and kinetic factors. This study was the first to provide detailed experimental insights into the factors that mainly affect heat transfer to fluids in PEM water electrolysis cells.

Anion exchange membrane electrolysis at work—Investigating impact of starting parameters and start-stop operation on cold start behavior and degradation

Water electrolysis is a key technology for the production of green hydrogen, with anion exchange membrane water electrolysis (AEMWE) showing promising properties. Future energy systems will require transient electrolysis operation to combine electrolysis with fluctuating renewably generated power. This study examines and optimizes the cold start process (ambient temperature and 0 V stack voltage) of an AEMWE stack system in terms of starting time, energy demand and degradation. The influence of relevant parameters such as voltage slope, target voltage, downtime and heating strategy on the starting process is experimentally quantified. A temporary increase in cell voltage during the starting process thereby represents a suitable compromise between acceleration of the startup and maintaining a low degradation. In addition, the start-stop degradation analysis with 150 cold starts per parameter set reveals that the degradation of the AEMWE stack during the starting process is independent of the maximum cell voltage and instead correlates with the steepness of the current slope. Using electrochemical impedance spectroscopy, the degradation is assigned to electrode processes. Under moderate starting conditions, degradation rates of 2–10 μV start−1 are observed. This shows that AEMWE is highly compatible with regular operational interruptions.

Advanced Iridium Catalysts on Multi-porous Tantalum Oxide Supports for Efficient Proton Exchange Membrane Water Electrolysis

Advanced Iridium Catalysts on Multi-porous Tantalum Oxide Supports for Efficient Proton Exchange Membrane Water Electrolysis

Metal oxide plating for maximizing the performance of ruthenium(IV) oxide-catalyzed electrochemical oxygen evolution reaction.

Hydrogen production by proton exchange membrane water electrolysis requires an anode with low overpotential for oxygen evolution reaction (OER) and robustness in acidic solution. While exploring new electrode materials to improve the performance and durability, optimizing the morphology of typical materials using new methods is a big challenge in materials science. RuO2 is one of the most active and stable electrocatalysts, but further improvement in its performance and cost reduction must be achieved for practical use. Herein, we present a novel technology, named "metal oxide plating", which can provide maximum performances with minimum amount. A uniform single-crystal RuO2 film with thickness of ∼2.5 nm was synthesized by a solvothermal-post heating method at an amount (x) of only 18 μg cm-2 (ST-RuO2(18)//TiO2 NWA). OER stably proceeds on ST-RuO2(18)//TiO2 NWA with ∼100% efficiency to provide a mass-specific activity (MSA) of 341 A gcat-1 at 1.50 V (vs. RHE), exceeding the values for most of the state-of-the-art RuO2 electrodes.

Machine learning in PEM water electrolysis: A study of hydrogen production and operating parameters

Proton exchange membrane water electrolysis (PEMWE) powered by renewable energy stands out as a promising technology for the sustainable production of high-purity hydrogen. This study employed three machine learning (ML) algorithms, random forest (RF), support vector machine (SVM), and eXtreme gradient boosting (XGBoost), to predict hydrogen production in PEMWE. Model performance was evaluated using root mean squared error (RMSE), coefficient of determination (R²), and mean absolute error (MAE) metrics. The top-performing models, RF and XGBoost, were further refined through hyperparameter tuning. The final models demonstrated high reliability in predicting hydrogen production rates, with RF consistently outperforming XGBoost. The RF model achieved a predictive accuracy of R² = 0.9898, RMSE = 19.99 mL/min, and MAE = 10.41 mL/min, while the XGBoost model achieved R² = 0.9894, RMSE = 20.43 mL/min, and MAE = 11.50 mL/min. Partial dependency plots (PDPs) emphasized the critical role of optimizing both cell voltage and current to maximize hydrogen production in PEMWE. These insights provide valuable guidance for operational adjustments, ensuring optimal system performance for high efficiency and productivity. The study suggests further research on the impact of parameters like temperature and power density on hydrogen production, incorporating them for better optimization.

Green hydrogen production by PEM water electrolysis up to the year 2050: Prospective life cycle assessment using learning curves

AbstractWater electrolysis technologies for producing green hydrogen are promising options for avoiding the use of fossil fuels and thus limiting climate change. Hydrogen can be used in a variety of sectors, enabling sector coupling, and strengthening the security of the energy supply through its storability. Environmental impacts provoked by green hydrogen production are comparatively low and improving manufacturing processes and technological advances will enable to further reduce the demand for raw materials and electricity and thus the environmental impacts. The objective of this study is to compare the status quo with prospective trends and target values. Learning curves of expected specific electricity demand and critical raw material (CRM) intensity are applied, and environmental impacts are subsequently analyzed via life cycle assessment. This study focuses on the polymer electrolyte membrane water electrolysis technology. As a result of the calculated learning curves, the CRM intensity could be reduced by more than 96% between 2022 and 2050. The specific electricity demand is projected to be reduced by 11.2%–22.5%. Combining the extrapolated reductions of electricity and CRM demand, a climate change impact decrease of 16.5%–28.5% is possible for green hydrogen production until the year 2050.

Strontium Doped IrOx Triggers Direct O−O Coupling to Boost Acid Water Oxidation Electrocatalysis

AbstractThe discovery of efficient and stable electrocatalysts for the oxygen evolution reaction (OER) in acidic conditions is crucial for the commercialization of proton‐exchange membrane water electrolyzers. In this work, we propose a Sr(OH)2‐assisted method to fabricate a (200) facet highly exposed strontium‐doped IrOx catalyst to provide available adjacent iridium sites with lower Ir−O covalency. This design facilitates direct O−O coupling during the acidic water oxidation process, thereby circumventing the high energy barrier associated with the generation of *OOH intermediates. Benefiting from this advantage, the resulting Sr−IrOx catalyst exhibits an impressive overpotential of 207 mV at a current density of 10 mA cm−2 in 0.5 M H2SO4. Furthermore, a PEMWE device utilizing Sr−IrOx as the anodic catalyst demonstrates a cell voltage of 1.72 V at 1 A cm−2 and maintains excellent stability for over 500 hours. Our work not only provides guidance for the design of improved acidic OER catalysts but also encourages the development of iridium‐based electrocatalysts with novel mechanisms for other electrocatalytic reactions.

Reversible Degradation Phenomenon in PEMWE Cells: An Experimental and Modeling Study

Abstract In proton exchange membrane water electrolysis (PEMWE) systems, voltage cycles dropping below a threshold are associated with reversible performance improvements, which remain poorly understood despite being documented in literature. The distinction between reversible and irreversible performance changes is crucial for accurate degradation assessments. One approach in literature to explain this behavior is the oxidation and reduction of iridium. Iridium-based electrocatalyst activity and stability in PEMWE hinge on their oxidation state, influenced by the applied voltage. Yet, full-cell PEMWE dynamic performance remains underexplored, with a focus typically on stability rather than activity.

This study systematically investigates reversible performance behavior in PEMWE cells using Ir-black as an anodic catalyst. Results reveal a recovery effect when the low voltage level drops below 1.5 V, with further enhancements observed as the voltage decreases, even with a short holding time of 0.1 s. This reversible recovery is primarily driven by improved anode reaction kinetics, likely due to changing iridium oxidation states, and is supported by alignment between the experimental data and a dynamic model that links iridium oxidation/reduction processes to performance metrics. This model allows distinguishing between reversible and irreversible effects and enables the derivation of optimized operation schemes utilizing the recovery effect.

Effects of the Dynamic Loading Frequency on Performance of the Proton Exchange Membrane Water Electrolysis.

Green hydrogen production via PEM water electrolysis is challenged by fluctuating input power when coupled with renewable energy sources. This study investigates the effects of dynamic loading frequencies on membrane electrode assembly (MEA) performance and durability. We found that higher loading frequencies facilitate the growth of the oxide layer of Ti porous transport layer (Ti-PTL) due to increased duration in the voltage spike region. These thicker and coarser oxide layers directly induce cracks and delamination in the anodic catalyst layers by spontaneously adsorbing an ionomer. These changes negatively impact the interface contact quality and anodic electrochemical active area, ultimately reducing the performance of the MEA, with higher frequencies accelerating this degradation. Additionally, applying a Pt coating to PTL effectively mitigates these adverse effects. This work highlights the importance of dynamic loading studies and reveals that effective management of the Ti-PTL and catalyst/PTL interface is necessary to achieve long-term operational durability of PEM water electrolysis.

A Chalcogenide-Derived NiFe2O4 as Highly Efficient and Stable Anode for Anion Exchange Membrane Water Electrolysis.

Developing low-cost, highly active, and durable oxygen evolution reaction (OER) electrodes is one of the critical scientific issues for anion exchange membrane water electrolyzer (AEM-WE). Herein, we report a vacancy-rich and alkali-stable NiFe2O4-type electrode (named as NiFeOx-350-Ov), derived from the chemical-vapor deposited precursor NiFeSexSy-350, as an efficient and robust anode material. The obtained electrode affords current densities of 100 and 500 mA cm-2 at overpotentials of 245 and 270 mV, respectively, and displays excellent long-term durability sustaining 1.0 A cm-2 at least for 1000 h. When coupled with Ni4Mo/MoO2/NF as a hydrogen evolution reaction (HER) catalyst, the resulting platinum-group metal (PGM)-free single-cell AEM-WE exhibits a cell voltage of 1.71 V at the current density of 1000 mA cm-2 at 80 °C and long-term durability during a current-cycling test between 0.5 A cm-2 and 1.0 A cm-2 over 150 h at 60 °C. This work highlights a unique reconstruction strategy for preparing highly active and durable OER catalysts used in PGM-free AEM-WE.

Investigation on corrosion and interface conductivity of TA1 under dynamic loads in proton exchange membrane water electrolyzer anodic environment

In this paper, the electrochemical and corrosion behavior of pure titanium (TA1) in simulated Proton Exchange Membrane Water Electrolysis (PEMWE) anodic environment was investigated. In this condition, the corrosion potential of TA1 was −689 mV, with a self-corrosion current density of 232.5 μA cm–2, and a polarization resistance of 125.9 Ω cm2. During potentiostatic polarization at 2 V, the current density was maintained at approximately 6 mA cm–2. However, the passivation process exhibited instability. Furthermore, this process has been shown to significantly facilitate the formation of surface oxides, and the passive film that formed displays the lowest bound water and OH−, and the highest content of O2–, exhibiting the highest average valence. Notably, dynamic potentials caused current transients, among which square wave potential was the most remarkable. The square wave potential shows an O2– content just below that of 2V potential polarization when fluctuating potentials are applied. The interfacial contact resistance (ICR) of 2 V potentiostatic polarization was slightly higher than that of square, sine and triangular waves. Additionally, the high temperature condition of PEMWE will aggravate the corrosion of TA1 by fluoride ions.

Rapid Scalable One‐step Production of Catalysts for Low‐Iridium Content Proton Exchange Membrane Water Electrolyzers

AbstractProton exchange membrane water electrolysis (PEMWE) is a promising technology for green hydrogen production, although its widespread development with state‐of‐the‐art loadings is threatened by the scarcity of iridium (Ir). Homogeneous dispersion of Ir in an immiscible electro‐ceramic matrix can enhance catalytic mass activity and structural stability. The study presents IrySn0.9(1−y)Sb0.1(1−y)Ox solid solutions produced by highly scalable flame spray pyrolysis (FSP) process as efficient anode electrocatalysts for PEMWE, containing only 0.2 mg cm−2 of Ir in the catalyst layer (CL). Intense mixing of metal vapor and large thermal gradients in the precursor‐derived high‐temperature flame aids stabilizing sub‐nanoscale entropic mixing within self‐preserved 4–6 nm particles. Detailed investigations confirm that the one‐step prepared solid solution electrocatalysts exhibit up to fourfold higher activity toward the oxygen evolution reaction (OER) compared to Ir black. The anode of a PEMWE utilizing this catalyst exhibits high performance and stability over 2000 h but with tenfold lower Ir loading than the state‐of‐art.