Proton Exchange Membrane Electrolyzer Research Articles

Synergistic Engineering of Dopant and Support of Ru Oxide Catalyst Enables Ultrahigh Performance for Acidic Oxygen Evolution

AbstractActive and robust electrocatalysts for acidic oxygen evolution reaction (OER) are of crucial importance for efficient proton exchange membrane water electrolyzer (PEM‐WE). Ruthenium (Ru) oxide has attracted considerable attention due to its high activity. However, the unsatisfying stability of Ru oxide in acidic OER environments hinders the application. Here, Ce‐doped RuO2 nanoparticles are designed and supported on Co─N─C material (Ce@RuO2/CoNC) for acidic OER. It is demonstrated that Ce@RuO2/CoNC delivers a super low overpotential of 150 mV and an excellent stability of 1000 h at 10 mA cm−2, outperforming most previously reported Ru‐based catalysts. The mass activity is estimated as 2365.5 AgRu−1 at 1.5 V (vs RHE), representing ≈2× advance compared to the best prior study. Furthermore, applied in a single‐cell PEM‐WE device, it can steadily operate for 1000 h at 200 mA cm−2. The studies show that Ce‐doping and Co─N─C support synergistically enhance the activity and stability of Ru oxide by optimizing the free energies of OER intermediates and suppressing the dissolution of Ru.

Bridging gaps between lab- and fab-oriented anode design for proton exchange membrane water electrolyzers

Bridging gaps between lab- and fab-oriented anode design for proton exchange membrane water electrolyzers

Ruthenium Single-Atom Modulated Protonated Iridium Oxide for Acidic Water Oxidation in Proton Exchange Membrane Electrolysers.

Proton exchange membrane water electrolysers promise to usher in a new era of clean energy, but they remain a formidable obstacle in designing active and durable electrocatalysts for the acidic oxygen evolution reaction (OER). In this study, a protonated iridium oxide embedded with single-atom dispersed ruthenium atoms (H3.8Ir1- xRuxO4) that demonstrates exceptional activity and stability in acidic water oxidation is introduced. The single Ru dopants favorably induce localized oxygen vacancies in the Ir─O lattice, synergistically strengthening the adsorption of OOH* intermediates and enhancing the intrinsic OER activity. In addition, the preferential oxidation of Ru and the electronegativity of the oxygen vacancies significantly stabilize the Ir─O active sites, improving the OER stability. Consequently, the H3.8Ir1─ xRuxO4 catalyst shows an overpotential of 255mV at 10mA cm-2 and displays exceptional catalytic endurance in acidic electrolytes, surpassing 1100 h, representing a remarkable one-order-of-magnitude increase in stability compared to that of pristine H3.8IrO4. A proton exchange membrane electrolyser utilizing the H3.8Ir1- xRuxO4 catalyst as an anode exhibits stable performance for more than 1280 h under a high current density of 2 A cm-2.

Optimal Electrocatalyst Design Strategies for Acidic Oxygen Evolution.

Hydrogen, a clean resource with high energy density, is one of the most promising alternatives to fossil. Proton exchange membrane water electrolyzers are beneficial for hydrogen production because of their high current density, facile operation, and high gas purity. However, the large-scale application of electrochemical water splitting to acidic electrolytes is severely limited by the sluggish kinetics of the anodic reaction and the inadequate development of corrosion- and highly oxidation-resistant anode catalysts. Therefore, anode catalysts with excellent performance and long-term durability must be developed for anodic oxygen evolution reactions (OER) in acidic media. This review comprehensively outlines three commonly employed strategies, namely, defect, phase, and structure engineering, to address the challenges within the acidic OER, while also identifying their existing limitations. Accordingly, the correlation between material design strategies and catalytic performance is discussed in terms of their contribution to high activity and long-term stability. In addition, various nanostructures that can effectively enhance the catalyst performance at the mesoscale are summarized from the perspective of engineering technology, thus providing suitable strategies for catalyst design that satisfy industrial requirements. Finally, the challenges and future outlook in the area of acidic OER are presented.

Recent Research on Iridium-Based Electrocatalysts for Acidic Oxygen Evolution Reaction from the Origin of Reaction Mechanism.

As the anode reaction of proton exchange membrane water electrolysis (PEMWE), the acidic oxygen evolution reaction (OER) is one of the main obstacles to the practical application of PEMWE due to its sluggish four-electron transfer process. The development of high-performance acidic OER electrocatalysts has become the key to improving the reaction kinetics. To date, although various excellent acidic OER electrocatalysts have been widely researched, Ir-based nanomaterials are still state-of-the-art electrocatalysts. Hence, a comprehensive and in-depth understanding of the reaction mechanism of Ir-based electrocatalysts is crucial for the precise optimization of catalytic performance. In this review, the origin and nature of the conventional adsorbate evolution mechanism (AEM) and the derived volcanic relationship on Ir-based electrocatalysts for acidic OER processes are summarized and some optimization strategies for Ir-based electrocatalysts based on the AEM are introduced. To further investigate the development strategy of high-performance Ir-based electrocatalysts, several unconventional OER mechanisms including dual-site mechanism and lattice oxygen mediated mechanism, and their applications are introduced in detail. Thereafter, the active species on Ir-based electrocatalysts at acidic OER are summarized and classified into surface Ir species and O species. Finally, the future development direction and prospect of Ir-based electrocatalysts for acidic OER are put forward.

Enriched Oxygen Coverage Localized within Ir Atomic Grids for Enhanced Oxygen Evolution Electrocatalysis.

Inefficient active site utilization of oxygen evolution reaction (OER) catalysts have limited the energy efficiency of proton exchange membrane (PEM) water electrolysis. Here, an atomic grid structure is demonstrated composed of high-density Ir sites (≈10atoms per nm2) on reactive MnO2-x support which mediates oxygen coverage-enhanced OER process. Experimental characterizations verify the low-valent Mn species with decreased oxygen coordination in MnO2-x exert a pivotal impact in the enriched oxygen coverage on the surface during OER process, and the distributed Ir atomic grids, where highly electrophilic Ir─O(II-δ)- bonds proceed rapidly, render intense nucleophilic attack of oxygen radicals. Thereby, this metal-support cooperation achieves ultra-low overpotentials of 166mV at 10mA cm-2 and 283mV at 500mA cm-2, together with a striking mass activity which is 380 times higher than commercial IrO2 at 1.53V. Moreover, its high OER performance also markedly surpasses the commercial Ir black catalyst in PEM electrolyzers with long-term stability.

Research on typical operating conditions of hydrogen production system with off-grid wind power considering the characteristics of proton exchange membrane electrolysis cell

Hydrogen energy, with its abundant reserves, green and low-carbon characteristic, high energy density, diverse sources, and wide applications, is gradually becoming an important carrier in the global energy transformation and development. In this paper, the off-grid wind power hydrogen production system is considered as the research object, and the operating characteristics of a proton exchange membrane (PEM) electrolysis cell, including underload, overload, variable load, and start- stop are analyzed. On this basis, the characteristic extraction of wind power output data after noise reduction is carried out, and then the self-organizing mapping neural network algorithm is used for clustering to extract typical wind power output scenarios and perform weight distribution based on the statistical probability. The trend and fluctuation components are superimposed to generate the typical operating conditions of an off-grid PEM electrolytic hydrogen production system. The historical output data of an actual wind farm are used for the case study, and the results confirm the feasibility of the method proposed in this study for obtaining the typical conditions of off-grid wind power hydrogen production. The results provide a basis for studying the dynamic operation characteristics of PEM electrolytic hydrogen production systems, and the performance degradation mechanism of PEM electrolysis cells under fluctuating inputs.

Integrated wind farm solutions: Harnessing clean energy for electricity, hydrogen, and freshwater production

This research explores the design, modeling, and feasibility of a multi-energy wind power plant in South Korea, aimed at producing electricity, fresh water, hydrogen, and oxygen. The main goal of the current study is to help the energy production system that uses the high potential of wind energy in areas with wind potential to increase power and efficiency and reduce harmful environmental effects for the production of hydrogen and fresh water. The system employs a PEM electrolyzer unit and reverses osmosis technology for hydrogen, oxygen, and freshwater generation. The innovation of this study lies in the integration of wind farm design with optimal electricity allocation to electrolyzers, reverse osmosis units, and the grid, maximizing efficiency and sustainability. A comprehensive case study is presented, evaluating the viability of putting the suggested strategy into practice in ten South Korean cities, with a focus on hydrogen production from wind energy. The study investigates ten scenarios for selecting the number of wind turbines, electrolyzers, and reverse osmosis devices, and sixteen scenarios for dividing wind farm coefficients to supply grid electricity, electrolyzer electricity, and reverse osmosis electricity. The optimal result indicates that 5% of wind farm electricity should be allocated to reverse osmosis units, 15% to electrolyzers, and 80% to the grid. The economic analysis indicates that among the system components, the wind farm, reverse osmosis, and PEM electrolyzer represent the highest costs. The system's performance is assessed across ten cities in South Korea, with Yeosu, Incheon, and Busan determined to be the best sites for the proposed power plant because of their strong potential to produce hydrogen using wind energy. Implementing the system in Yeosu, the optimal city, may stop 9664.326 tons of carbon dioxide from being released, generate 47374.15 MWh of electricity, and expand 46 ha of green space. Additionally, selling 9474.83 MW of electricity to the grid would meet the annual electricity needs of 929 people in Yeosu, South Korea. This study emphasizes the potential of wind power plants in South Korea to contribute to sustainable energy production and carbon dioxide reduction, highlighting their potential for a greener and more sustainable future.

Recycling spent battery components into highly efficient hydrogen and oxygen evolution electro-nano-catalysts

Inspired by the 'waste-to-resource' strategic theme for environmental recovery, here we present the recycling of spent dry cells and spent Lithium-ion batteries aiming to achieve the preparation of cheap and efficient electrocatalysts for Proton Exchange membrane electrolyzers instead of the precious-based electrocatalysts. Graphite doped with manganese (IV) oxide nanoparticles, graphite doped with manganese (IV) oxide and aluminum oxide nanoparticles, lithium cobalt oxide doped with copper oxide nanoparticles, and lithium cobalt oxide doped with copper oxide and zinc oxide nanoparticles synthesis procedures are done via hydrothermal method at a pressure of 4.5 Mpa at 180 ○C. Electrochemical characterization is done to determine overpotential, tafel slope, and electrocatalytic stability via a three-electrode system. The optimum results are observed by the graphite doped with manganese (IV) oxide nanoparticles, which show -55.06 mV and -41.33 mV/dec as overpotential and tafel slope at -10 mA/cm2 for hydrogen evolution reaction with surface area of 40.87 m2/g and 21.05 nm as crystal size and Graphite doped with manganese oxide and aluminum oxide nanoparticles, which show 321.58 mV and 174.14 mV/dec as overpotential and Tafel slope for oxygen evolution reaction at 10 mA/cm2 with surface area of 7.64 m2/g and 44.43 nm as crystal size.

A gradient porous transport layer enabling a high-performance proton-exchange membrane electrolysis cell

Large-scale green hydrogen production through proton-exchange membrane electrolysis cells (PEMECs) is constrained by high costs. Operating PEMECs at high current densities while minimizing overpotentials, particularly the mass transport overpotential due to intense water-oxygen two-phase flow, is crucial. The porous transport layer (PTL) plays a key role in facilitating water-oxygen two-phase flow and affecting ohmic resistance and catalyst utilization. In this study, a gradient PTL has been developed by introducing titanium mesh with tunable pores between the titanium felt and the flow field. The woven mesh structure with large pores facilitates water transport under the ribs, while the titanium felt reduces ohmic resistance and improves catalyst utilization. Experimental results demonstrate that the gradient PTL with a single layer of titanium mesh (pore size: 0.6 mm) can reduce the mass transport overpotential from 0.478 V to 0.206 V at 5 A/cm2 and maintain low ohmic and activation overpotentials compared with the conventional PTLs. Additionally, the gradient PTL with two titanium mesh layers (pore sizes: 0.6 mm and 0.28 mm) can further facilitate water transport, reducing mass transport overpotential to 0.149 V at 5 A/cm2. Numerical simulations reveal that the developed gradient PTL increases the volume fraction of liquid water and ensures uniform water distribution in the catalyst layer. The combined results indicate that the gradient PTL design is promising for enhancing mass transport performance while maintaining low ohmic resistance and high catalyst utilization, making PEMECs more viable for large-scale hydrogen production.

Topologically Close-Packed Frank-Kasper C15 Phase Intermetallic Ir Alloy Electrocatalysts Enables High-Performance Proton Exchange Membrane Water Electrolyzer.

Chemical synthesis of unconventional topologically close-packed intermetallic nanocrystals (NCs) remains a considerable challenge due to the limitation of large volume asymmetry between the components. Here, a series of unconventional intermetallic Frank-Kasper C15 phase Ir2M (M = rare earth metals La, Ce, Gd, Tb, Tm) NCs is successfully prepared via a molten-salt assisted reduction method as efficient electrocatalysts for hydrogen evolution reaction (HER). Compared to the disordered counterpart (A1-Ir2Ce), C15-Ir2Ce features higher Ir-Ce coordination number that leads to an electron-rich environment for Ir sites. The C15-Ir2Ce catalyst exhibits excellent and pH-universal HER activity and requires only 9, 16, and 27mV overpotentials to attain 10mA cm-2 in acidic, alkaline, and neutral electrolytes, respectively, representing one of the best HER electrocatalysts ever reported. In a proton exchange membrane water electrolyzer, the C15-Ir2Ce cathode achieves an industrial-scale current density of 1 A cm-2 with a remarkably low cell voltage of 1.7V at 80°C and can operate stably for 1000 h with a sluggish voltage decay rate of 50 µV h-1. Theoretical investigations reveal that the electron-rich Ir sites intensify the polarization of *H2O intermediate on C15-Ir2Ce, thus lowering the energy barrier of the water dissociation and facilitating the HER kinetics.

Thermodynamic and Economic Analysis of the Green Ammonia Synthesis System Driven by Synergistic Hydrogen Production Using Alkaline Water Electrolyzers and Proton Exchange Membrane Electrolyzers

Green ammonia and hydrogen from renewable energy sources have emerged as crucial players during the transition of the chemical industry from a fossil energy‐dominated economy to one that is environmentally friendly. This work proposes a green ammonia synthesis system driven by synergistic hydrogen generation using alkaline water electrolyzers (AWE) and proton exchange membrane electrolyzers (PEMEC). The effects of hydrogen‐production ratios of PEMEC and AWE on the thermodynamic and economic performance of the system are compared and analyzed via multi‐objective optimization. The findings showed that an increase in the amount of hydrogen produced by PEMEC improves the system's energy efficiency, but the payback period is delayed because of the PEMEC high initial investment cost. The techno‐economic performance of the system at a 1:1 ratio of PEMEC to AWE hydrogen production are investigated considering the system level heat integration based on the pinch point analysis method to maximize the heat recovery. The results show that increasing the operational temperature, the pressure of the electrolyzer, and the ammonia synthesis pressure will enhance the system's thermal performance. Economic analysis shows that reducing electricity prices and electrolyzer investment costs will be the key to achieving the economic feasibility of the green ammonia system.

Evaluating the economic influence of water sources on green hydrogen production: A cost analysis approach

The production of green hydrogen requires significant water usage, making the economic evaluation of different water sources crucial for optimizing the Levelized Cost of Hydrogen (LCOH). This study examines the economic impact of using seawater, groundwater, grid water, industrial wastewater, and rainwater for hydrogen production through PEM electrolysis considering the water abstraction, transport, treatment, and storage costs across various plant sizes (1 MW, 10 MW, 20 MW, 50 MW, and 100 MW) were assessed and a sensitivity analysis on electricity prices was conducted. Findings reveal that while water-related costs are minimal (<2% of LCOH), transport distance significantly impacts LCOH, sometimes exceeding 10%. Future studies should integrate life cycle analysis and sustainability criteria beyond economic factors, considering social, ecological, and technical dimensions.

Segmented catalyst layer with varied catalyst loading to improve the cost performance of proton exchange membrane electrolysis cell, a numerical investigation

In this work, a steady-state, three-dimensional and non-isothermal numerical model for a proton exchange membrane electrolysis cell (PEMEC) is established. Based on this model, the distribution of catalyst loading is specifically designed according to the flow characteristics of both parallel and serpentine channels. In general, the catalyst loading is progressively reduced from inlet to outlet along the flow direction to match the local water content, leading to an innovative segmented catalyst layer which has not been studied yet for PEMEC applications. The electrochemical behavior of different segmentation schemes is investigated by comparing their polarization curves normalized by either electrode area or catalyst loading, while other physical fields such as velocity, pressure, water mole fraction and temperature distributions are also characterized. The numerical results reveal that a reasonable distribution of catalyst can reduce its amount of usage while still maintaining most of the PEMEC performance. In other words, the cost performance is significantly improved. This is mainly attributed to the full use of uneven water distribution in the flow channel, which improves the catalyst utilization efficiency significantly. This strategy is proved to be effective for both serpentine and parallel channels, ensuring a broad application prospect.

Niobium Interlayer Coating: Is it a Practical Approach to Tune the Protective Pt Loading in PEM Water Electrolyzers?

Proton exchange membrane (PEM) water electrolysis is a pioneering and promising method for sustainable green hydrogen generation. However, the high cost of PEM water electrolyzer components poses a significant barrier to the commercialization and widespread application of this technology. In this research, a novel Niobium-Platinum coating is developed for the porous transport layer (PTL) to reduce the precious metal loading. Niobium (Nb)-based coating was applied as an interlayer between Pt and titanium (Ti) felt substrates to increase the adhesion of Pt. For this study, pulsed laser deposition (PLD) technique was applied for the first time to coat Nb and Pt multilayers onto Ti felt substrates. The results demonstrate that incorporating a Nb coating as an interlayer lead to reducing the Pt loading, which holds promise for the practical application of PTLs in PEM water electrolyzers.

Concentric circular flow field to improve mass transport in large-scale proton exchange membrane water electrolysis cells

Uniform reactant supply is challenging for high-performance proton exchange membrane water electrolysis (PEMWE) in renewable energy storage. The anode flow-field pattern, anode flow-field orientation, and stoichiometric ratio influence mass transport. In this study, the performances of two flow-field patterns were compared for a single PEMWE cell with an active area of 100 cm2. Straight serpentine was used as the reference model and a concentric circle with an arc shape was designed. In addition, the optimal anode flow field orientation and stoichiometric ratio were determined. The results indicate that the optimal anode flow-field pattern differs depending on the stoichiometric ratio. At low flow rates, mass transfer via diffusion was dominant; therefore, a straight serpentine flow was preferred. In contrast, a concentric circle, which induces a significant differential pressure between adjacent channels, is preferable at a high flow rate. This is because convection is dominant in mass transfer. Maintaining a stoichiometric ratio of 10 or more is recommended during the operation. At a ratio of less than 10, the reactant was depleted at a high current density, and the mass transfer resistance increased. In addition, water is better distributed by gravity and buoyancy when the electrolyte membrane is parallel to the ground, and the anode flow path is above the porous medium. This leads to high PEMWE cell performance.

(Invited) Development of Novel Coatings on Stainless Steel based Bipolar Plates for Proton Exchange Membrane (PEM) Water Electrolyzer Application

The stainless steel (SS) is an appropriate material for bipolar plate of PEM water electrolyzer owing to its high electron transport, superior mechanical characteristics, and formability, but it needs a coating to increase corrosion resistance. Herein, the multilayer coating of Au/Cr/Au on the SS was developed by electroplating method and corrosion studied were performed for bipolar plate application of PEM water electrolyzer. The gold striking underlayer on the SS substrate passivated the surface oxides and facilitated a dense electroplated chromium layer. Furthermore, a uniform gold protective layer was electroplated on the chromium coated substrate to achieve a promising anti-corrosive property. The Au/Cr/Au 316L SS substrate presented approximately ten times lower corrosion current density, and positive shift of corrosion potential as compared to uncoated SS substrate. The Au/Cr/Au/ 316 L SS was analysed for long time, and it depicted slower corrosion as compared to without striking underlayer of gold (Au/Cr/ 316L SS).

Deciphering Anion Exchange Membrane Water Electrolysis: A Distribution of Relaxation Times Approach

Anion exchange membrane water electrolysis (AEM-WE) is a promising method for hydrogen production, offering advantages over proton exchange membrane water electrolysis (PEM-WE), such as the use of nonprecious metal catalysts and perfluorosulfonic acid free membranes. Despite achieving impressive current densities, challenges in efficiency and stability remain. This study employs electrochemical impedance spectroscopy (EIS), the equivalent circuit model (ECM) and distribution of relaxation times (DRT) analysis to investigate AEM-WE cells. DRT analysis identifies and quantifies five loss mechanisms within the AEM-WE system, including hydrogen and oxygen evolution reactions and ionic transport losses. Long-term experiments reveal catalyst degradation and its impact on performance, providing insights for targeted optimisation. The findings enhance understanding of the electrochemical processes in AEM-WE, offering pathways to improve stability and efficiency.

Deciphering Anion Exchange Membrane Water Electrolysis: A Distribution of Relaxation Times Approach

Anion exchange membrane water electrolysis (AEM-WE) is a promising method for hydrogen production, offering advantages over proton exchange membrane water electrolysis (PEM-WE), such as the use of nonprecious metal catalysts and perfluorosulfonic acid free membranes. Despite achieving impressive current densities, challenges in efficiency and stability remain. This study employs electrochemical impedance spectroscopy (EIS), the equivalent circuit model (ECM) and distribution of relaxation times (DRT) analysis to investigate AEM-WE cells. DRT analysis identifies and quantifies five loss mechanisms within the AEM-WE system, including hydrogen and oxygen evolution reactions and ionic transport losses. Long-term experiments reveal catalyst degradation and its impact on performance, providing insights for targeted optimisation. The findings enhance understanding of the electrochemical processes in AEM-WE, offering pathways to improve stability and efficiency.

Evaluating the techno-economic potential of large-scale green hydrogen production via solar, wind, and hybrid energy systems utilizing PEM and alkaline electrolyzers

The study evaluates the potential of solar, wind, and hybrid PV/WT renewable energy systems for green hydrogen production in four Iraqi cities. Through a comparative analysis of six distinct scenarios involving the deployment of 60 MWp solar panels, 30 MWp wind turbines, and 45 MWp hybrid PV/WT systems, the research aims to ascertain the most energy-efficient and cost-effective strategy for hydrogen generation. This evaluation is aligned with the operational capacities of two types of water electrolyzers: Alkaline (AWE) and proton exchange membrane (PEM), each with a 17.5 MWp capacity. Employing the HOMER Pro software for system simulation and optimization, and considering a project timeline from 2022 to 2042, the study identifies Anbar City as the prime location for green hydrogen production, highlighting solar PV panels as the most economical option with the lowest levelized cost of energy at US $4.5/MWh. The analysis further demonstrates that hydrogen production costs are US $1.98/kg for AWE electrolyzers and US $2.72/kg for PEM electrolyzers, with net present costs of US $26.31 million and US $35.91 million, respectively. Moreover, the annual hydrogen output is estimated at 1.11 million kg for AWE and 1.19 million kg for PEM electrolyzers. These insights significantly contribute to the strategic planning and development of Iraqi green hydrogen sector, offering a valuable framework for policymakers and stakeholders invested in sustainable energy transitions.