Proton Exchange Membrane Electrolyzer Research Articles

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).

IrPdCuFeNiCoMo BasedCore-Shell Icosahedron Nanocrystals and Nanocages for Efficient and RobustAcidic Oxygen Evolution.

Facets engineering of high entropy alloy (HEA) nanocrystals might be achieved via shape-controlled synthesis, which is promising but remains challenging in designing Ir-based catalysts towards efficient and robust oxygen evolution reaction (OER) in acidic medium. Herein, icosahedra nanocrystals featured with PdCu core and IrPdCuFeNiCoMo shell were prepared by wet-chemical reduction in one-pot, ascribing to the initial formation PdCu core and subsequent deposition and diffusion of IrPdCuFeNiCoMo HEA shell. Sequential selective chemical etching of PdCu core results in IrPdCuFeNiCoMo HEA nanocages, delivering an overpotential of 235 mV at 10 mA cm-2, 51.0 mV dec-1, and 1624 A gIr-1 at 1.50 V in a conventional three electrode cell. In a proton exchange membrane water electrolyzer, it delivers a low cell voltage of 1.65 and 1.77 V at a current density of 1.0 and 2.0 A cm-2, respectively, and maintains stable over 900 h at 500 mA cm-2. Theoretical calculations attribute the enhanced intrinsic activity to the broad distribution of the binding energy for OER intermediates on IrPdCuFeNiCoMo HEA, which breaks the linear scaling relationship and accelerates the OER process.

Integrating Interactive Ir Atoms into Titanium Oxide Lattice for Proton Exchange Membrane Electrolysis.

Iridium (Ir)-based oxide is the state-of-the-art electrocatalyst for acidic water oxidation, yet it is restricted to a few Ir-O octahedral packing modes with limited structural flexibility. Herein, the geometric structure diversification of Ir is achieved by integrating spatially correlated Ir atoms into the surface lattice of TiO2 and its booting effect on oxygen evolution reaction (OER) is investigated. Notably, the resultant i-Ir/TiO2 catalyst exhibits much higher electrocatalytic activity, with an overpotential of 240 mV at 10 mA cm-2 and excellent stability of 315 h at 100 mA cm-2 in acidic electrolyte. Both experimental and theoretical findings reveal that flexible Ir─O─Ir coordination with varied geometric structure plays a crucial role in enhancing OER activity, which optimize the intermediate adsorption by adjusting the d-band center of active Ir sites. Operando characterizations demonstrate that the interactive Ir─O─Ir units can suppress over-oxidation of Ir, effectively widening the stable region of Ir species during the catalytic process. The proton exchange membrane (PEM) electrolyzer, equipped with i-Ir/TiO2 as an anode, gives a low driving voltage of 1.63 V at 2 A cm-2 and maintains stable performance for over 440 h. This work presents a general strategy to eliminate the inherent geometric limitations of IrOx species, thereby inspiring further development of advanced catalyst designs.

Numerical study on dynamic response characteristics of proton exchange membrane water electrolyzer under transient loading

Under dynamic operating conditions, the proton exchange membrane water electrolyzers are prone to voltage overshoot, resulting in fluctuations under transient operation. In this paper, a three-dimensional, two-phase, non-isothermal model is developed to investigate the role of various factors on the dynamic response characteristics of electrolyzers. The results demonstrate that the overshoot phenomenon can be significantly mitigated by using a linear loading strategy and a multi-step loading strategy compared to a step loading strategy. Meanwhile, the effect of the flow field structure was examined, revealing that single-serpentine flow field exhibited excellent dynamic response performance. Additionally, calculated through multiple evaluation methods, it was found that the effect of loading magnitude was significantly greater than that of the other factors, including temperature, flow field structure and anode porous transport layer porosity. Finally, under combined variable load conditions, research revealed that whereas single-serpentine flow field shown benefits regarding dynamic response and energy dissipation.

Innovative biogas energy system: Enhancing efficiency and sustainability through multigeneration integration

This research suggests using landfill gas, derived from landfilling operations, as a feasible alternative to fossil fuels. This study introduces a novel and all-encompassing method for utilizing landfill biogas. The proposed system utilizes a supercritical Brayton cycle with carbon dioxide as the working fluid, a transcritical CO2 cycle, two ammonia Rankine cycles, a single-effect desalination cycle, a proton exchange membrane electrolyzer, and an improved Kalina cycle. The system underwent evaluation using Aspen HYSYS software, enabling assessments in terms of energy, exergy, thermo-economic, and environmental variables. The examination of the findings indicates that the suggested solution has much higher energy efficiency compared to similar studies. The assessments determined the energy efficiency of the process in power generation, combined heat and power, combined cooling, heat and power, and multigeneration modes to be 23.62 %, 80.89%, 81.19%, and 82.72%, respectively. Furthermore, environmental research has revealed that the new process emits a total of 1743 kg/h of carbon dioxide and has an emission rate of 0.23 kg/kWh. The exergy analysis indicated that the fuel burner exhibited the greatest degree of irreversibility, accounting for 40%. Furthermore, a sensitivity analysis was performed on crucial parameters, including the temperature of the heat source in the single-effect desalination section and the rate at which water flows into the electrolyzer. The objective was to evaluate the influence of changes in these parameters on energy efficiency, exergy efficiency, carbon dioxide emission intensity, product production rate, and levelized energy cost. The economic analysis determined that the proposed scheme would have a total annual cost of 8,667,124 $ with a levelized energy cost of 0.17 $/kWh.

Green hydrogen, power, and heat generation by polymer electrolyte membrane electrolyzer and fuel cell powered by a hydrokinetic turbine in low-velocity water canals, a 4E assessment

Thousands of kilometers of man-made low-velocity water transfer canals around the world can be used as a source of renewable energy for electricity and green hydrogen production. These canals have not been well investigated as an energy source, according to the literature. In the present paper, three technologies of Hydrokinetic Turbine (HKT), Polymer Electrolyte Membrane Fuel Cell, and Electrolyzer (PEM-FC/EL) are utilized to produce electricity, green hydrogen, and heat using these canals. Thermodynamic, economic, and environmental models of the cycle are presented, coded in the Engineering Equation Solver software, and finally validated with published research and manufacturers’ data. Two scenarios were examined, first HKT, PEMEL, and PEMFC were used for electricity generation (power-to-hydrogen-to-power, P2X2P) and second only HKT and PEMEL were used for green hydrogen production (power-to-hydrogen, P2X). While both scenarios are economical, the P2X scenario has a smaller payback period (less than 2 years) and a higher net present value. Practical correlations are derived to determine the rate of hydrogen production, power generation, and emission reduction as a function of water velocity. The round-trip energy and exergy efficiency of the system is 46.17% and 20.78% and it reduces carbon dioxide by 0.874 tons/year when water velocity is 1.5 m/s.

99.6% efficiency DC-DC coupling for green hydrogen production using PEM electrolyzer, photovoltaic generation and battery storage operating in an off-grid area

This paper presents a novel connection and control strategy for a hydrogen generation system using a proton exchange membrane electrolyzer powered by solar energy in an off-grid area without network backup. Given that, the proposed architecture is based on the indirect control of the Photovoltaic plant (achieved by removing a power-converter), the presented solution is more efficient and more reliable than the traditional scheme. Furthermore, with this innovation one can reach the same hydrogen production with smaller electrolyzers.The methodology includes detailed models of the photovoltaic panel and the electrolyzer, along with a control strategy that considers the degradation mechanisms of the electrolyzer to ensure reliable and prolonged operation. The results show that the proposed strategy keeps the operating power of the electrolyzer constant, even under variations in irradiance, thanks to energy storage in batteries. It is demonstrated that the proposed system offers efficiency above 99.6% during the analyzed period, with a 100% utilization rate of the electrolyzer, avoiding periods of inactivity and high current peaks. The study also includes simulations and experimental tests that confirm the feasibility and effectiveness of the presented solution, highlighting its advantages in terms of efficiency and investment costs compared to direct connections and other existing methods.

Corrigendum to “A multi-energy production system utilizing an absorption refrigeration cycle, and a PEM electrolyzer powered by geothermal energy: Thermoeconomic assessment and optimization” [Renew. Energy, (229), August 2024, 120744]

Corrigendum to “A multi-energy production system utilizing an absorption refrigeration cycle, and a PEM electrolyzer powered by geothermal energy: Thermoeconomic assessment and optimization” [Renew. Energy, (229), August 2024, 120744]

Fault diagnosis of cells in PEM electrolyzer stack under fluctuating power source

The scale of hydrogen production using renewable energy is expanding with the global energy transition accelerating. Safety in hydrogen production is gaining increased attention. Compared to stable power supplies, the voltage of the electrolyzer stack fluctuates dynamically with input power in the wind and photovoltaic systems. For this reason, a fault diagnosis method for electrolyzers under fluctuating power sources is proposed. Firstly, the faults of the sensor and electrolyzer are distinguished by interleaved voltage detection to avoid the misdiagnosis caused by the sensor failure. Secondly, an improved variable mode decomposition method is introduced to process the raw voltage signals to weaken the influence of inter-cell inconsistency on fault diagnosis. Furthermore, the fault characteristics are highlighted with a shortened fault identification time. Then, the fault characteristics are extracted by the degree of cell voltage fluctuation with the occurrence of faults is judged by the difference in the degree of fluctuation between neighboring electrolyzers. Finally, faults such as short circuits and water shortages in the electrolyzer are diagnosed using the correlation differences in cell voltage between different faults. The feasibility of this fault diagnosis method is validated through case studies and comparative analyses.

Techno-economic assessment of a green liquid hydrogen supply chain for ship refueling

Maritime transportation is an essential component of international trade and global economic growth: according to the 2021 Review of Maritime Transport, transportation by sea is responsible for more than 80% of the global product flow. To facilitate decarbonization and reduce pollutant emissions in the maritime sector, the International Maritime Organization (IMO) has set very ambitious targets, and hydrogen is one of the most promising energy vectors capable of supporting the required low-carbon energy transition. Recently, therefore, more attention has been paid to finding technical solutions for the development of hydrogen-based alternative propulsion systems and, at the same time, a hydrogen distribution infrastructure suitable for shipping. In this scenario, this study aims to analyze, through design, modeling and optimization approaches, the energy and economic performance of an offshore wind power plant integrated with a liquid hydrogen production system to be used for refueling ships far from ports. This study focuses on the development of an optimization procedure dedicated to finding the best technical solution in terms of component sizes and management strategies that ensure the minimum Levelized Cost of Hydrogen (LCOH). Resultshave highlighted that the proposed innovative plant configuration for the offshore liquid hydrogen production is able to produce 317 tons per year of green hydrogen with a LCOH of 16.77 €/kg by using 19 MW offshore wind farm and 5 MW PEM electrolyzer.

Investigation of oxygen transport in porous transport layer with different porosity gradient configurations using phase field method

Minimizing oxygen accumulation in the porous transport layer (PTL) is crucial for reducing mass transfer losses in proton exchange membrane (PEM) electrolyzer. This study develops a two-dimensional transient model of gas-liquid two-phase flow at the anode of PEM electrolyzer using the phase field method. The model investigates the mechanisms of oxygen transport and the interactions among various oxygen paths in PEM electrolyzer. We explore the impact of porosity gradient configurations in the PTL and the presence of a surface microporous layer (MPL) on oxygen transport. The findings indicate that for PTL with an average porosity of 60%, forward gradient configuration—where porosity increases from the catalyst layer (CL) towards the channel (CH)—promotes the merging of bubble sites and path contraction, thereby reducing oxygen saturation. The optimal gradient configuration, with porosities of 50% at the CL and 70% at the CH, achieves a 29.5% reduction in oxygen saturation. Conversely, reverse gradient configuration, with decreasing porosity from CL to CH, results in increased oxygen saturation. The addition of surface MPL further lowers oxygen saturation and shortens oxygen breakthrough time; smaller MPL particle sizes correspond to lower oxygen saturation and shorter breakthrough times. This study provides valuable insights for the optimal design of PTL structures in PEM electrolyzers.

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

Atomically engineered interfaces inducing bridging oxygen-mediated deprotonation for enhanced oxygen evolution in acidic conditions

The development of efficient and stable electrocatalysts for water oxidation in acidic media is vital for the commercialization of the proton exchange membrane electrolyzers. In this work, we successfully construct Ru–O–Ir atomic interfaces for acidic oxygen evolution reaction (OER). The catalysts achieve overpotentials as low as 167, 300, and 390 mV at 10, 500, and 1500 mA cm−2 in 0.5 M H2SO4, respectively, with the electrocatalyst showing robust stability for >1000 h of operation at 10 mA cm−2 and negligible degradation after 200,000 cyclic voltammetry cycles. Operando spectroelectrochemical measurements together with theoretical investigations reveal that the OER pathway over the Ru–O–Ir active site is near-optimal, where the bridging oxygen site of Ir–OBRI serves as the proton acceptor to accelerate proton transfer on an adjacent Ru centre, breaking the typical adsorption-dissociation linear scaling relationship on a single Ru site and thus enhancing OER activity. Here, we show that rational design of multiple active sites can break the activity/stability trade-off commonly encountered for OER catalysts, offering good approaches towards high-performance acidic OER catalysts.

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.

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.

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.

Design Principle and Regulation Strategy of Noble Metal‐Based Materials for Practical Proton Exchange Membrane Water Electrolyzer

AbstractGreen hydrogen holds immense promise in combating climate change and building a sustainable future. Owing to its high power‐to‐gas conversion efficiency, compact structure, and fast response, the proton exchange membrane water electrolyzer (PEMWE) stands out as the most viable option for the widespread production of green hydrogen. However, the harsh operating conditions of PEMWE make it heavily dependent on noble metal‐based catalysts (NMCs) and incur high operational and maintenance costs, which hinder its extensive adoption. Hence, it is imperative to improve the performance and lifespan of NMCs and develop advanced components to reduce the overall costs of integrating PEMWE technology into practical applications. In light of this, the fundamental design principles of NMCs employed in acidic water electrolysis are summarized, as well as recent advancements in compositional and structural engineering to enhance intrinsic activity and active site density. Moreover, recent innovations in stack components of practical PEMWE and their impact on cost‐benefit and lifespan are presented. Finally, the current challenges are examined, and potential solutions for optimizing NMCs and PEMWE in electrocatalytic hydrogen production are discussed.

A Combined Investment and Operational Optimization Approach for Power-to-Methanol Plants

In the global effort for industrial decarbonization, repurposing closed coal-fired power plants into power-to-methanol (PtM) plants offers a promising pathway to reduce CO₂ emissions while leveraging existing infrastructure. This study introduces a novel combined optimization approach using mixed-integer linear programming (MILP) to simultaneously optimize the investment and operation of a PtM plant, assessing its economic viability. The model incorporates the operational flexibility of proton exchange membrane (PEM) electrolyzers in response to fluctuating electricity prices through a piecewise linear representation of its load–efficiency characteristic curve. A case study of a repurposed coal plant in Austria demonstrates the model's applicability and practical relevance. The results show that larger electrolyzer capacities, i.e., 434 MW, with flexible part-load operation can significantly reduce methanol production costs, i.e., EUR 0.8/kg, achieving competitiveness under high CO₂ pricing scenarios, i.e., EUR 500/ton. A sensitivity analysis is performed to identify the critical factors influencing production costs. This study concludes that the combined investment and operational optimization approach effectively captures the essential elements of PtM systems, enabling faster, better, and operation-informed investment decisions for innovative technologies to support the ongoing energy transition. These findings indicate that PtM technologies can be a viable solution for asset repurposing, grid stabilization, and decarbonizing hard-to-abate sectors.

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.

Fluoride emission rate analysis in proton exchange membrane water electrolyzer cells

The assessment of PEM water electrolyzer (PEMWE) degradation is essential for understanding their long-term durability and performance under real-world conditions. This research focuses on the fluoride emission rate (FER) as a crucial parameter during PEMWE operation. Two different FER analysis methods were evaluated, considering their feasibility and ease of integration into a PEMWE system. Various stressors were examined to gain insights into membrane degradation and explore potential mitigation strategies. The utilization of a photometric detection method allowed for the quantification of FER in each test. Results highlight a noteworthy correlation between applied stressors and FER, with variations depending on specific test conditions. An accelerated stress test conducted for 100 hours revealed a high FER at the anode of 0.83 μg h−1 cm−2 during the initial phase. Correspondingly, energy dispersive X-ray (EDX) mapping showed a reduction in Nafion™ content on the catalyst-coated membrane (CCM) surfaces, likely impacting proton conductivity and performance. Electrochemical results further support these findings, indicating performance changes corresponding to the observed membrane degradation.