Achieving efficient self-humidification is critical for reducing the complexity, cost, and parasitic energy consumption of proton exchange membrane fuel cell (PEMFC) systems, thereby accelerating their large-scale commercialization. This review provides a comprehensive overview of recent advances in electrode engineering strategies for self-humidifying PEMFCs from the perspective of internal water management. The fundamental mechanisms governing water generation, transport, retention, and redistribution within membrane electrode assemblies (MEAs) are first discussed. Subsequently, the evolution of self-humidification strategies is systematically reviewed, spanning hygroscopic additives, multifunctional catalyst supports, gradient and double-layer catalyst architectures, advanced gas diffusion media, directional water-transport structures, and emerging porous materials such as metal–organic frameworks (MOFs) and covalent organic frameworks (COFs). Particular emphasis is placed on the transition from localized water-retention approaches toward multiscale water-management engineering that simultaneously regulates proton transport, reactant accessibility, and water distribution. The durability challenges associated with self-humidifying operation, together with recent advances in artificial intelligence-assisted electrode design and optimization, are also highlighted. More broadly, the concepts and design principles discussed in this review may contribute to establishing a new paradigm of integrated water-management engineering, providing a foundation for the development of highly efficient, durable, and commercially viable PEMFC systems for future sustainable energy applications.

Generating a cost‐effective precious‐metal catalyst is essential for achieving low‐cost, large‐scale green hydrogen production. Since the majority of the overpotential in the proton exchange membrane water electrolyzer arises during the oxygen evolution reaction (OER), the remarkable performance of the IrO 2 makes it an ideal anodic catalyst. Herein, a simple, straightforward method was used to prepare an IrO 2 ‐loaded transition‐metal carbide‐supported catalyst. The IrO 2 nanoparticles were loaded on TiC (Ir x TC 1‐x ) and Ti 2 AlC (Ir x TAC 1‐x ) at 20 to 80 wt% IrO 2 loadings, using the modified Adams fusion method. A diameter of 2 nm was obtained to exhibit improved OER performance in 0.5 M H 2 SO 4 compared with commercial IrO 2 . The catalysts showed a uniform distribution of IrO 2 nanoparticles on the supports. Overpotentials of 260 and 250 mV were obtained for Ir 80 TC 20 and Ir 80 TAC 20 at 10 mA cm −2 . The prepared Ir 80 TC 20 and Ir 80 TAC 20 showed good OER activity, delivering 10 mA cm −2 at 1.47 and 1.46 V versus RHE, respectively. The catalysts exhibited OER stability at 10 mA cm −2 for 73 and 58 h, respectively, for Ir 80 TC 20 and Ir 80 TAC 20 . The precursor solution proved significant recyclability, and the study demonstrated a new approach to rapidly design low‐cost, high‐performance anodic catalysts for overall OER performance.

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) offer significant advantages for clean energy conversion. However, their performance is severely hindered by the dual role of phosphoric acid (PA), which serves as the proton conductor but also acts as a potent poison for platinum (Pt) catalysts, inhibiting the oxygen reduction reaction (ORR) and demanding high Pt loadings. This review provides a systematic analysis of the extensive efforts to mitigate PA poisoning. A diverse range of strategies is surveyed, including the development of poison-tolerant Pt-alloy catalysts (e.g., Pt–Ni, Pt–Co), the use of advanced carbon and metal oxide supports to leverage strong metal-support interactions, the design of protective surface modifications, the exploration of Pt-free catalysts like Fe–N–C, and the engineering of the catalyst layer with functional additives. Despite significant progress at the catalyst level, a critical performance gap persists between lab-scale tests and real-world membrane electrode assemblies (MEAs). This discrepancy arises because particle-centric approaches often neglect the severe mass transport limitations and low catalyst utilization within conventional, randomly structured electrodes flooded with viscous PA. To overcome these challenges, a paradigm shift is necessary. It is proposed that the future of HT-PEMFCs lies in a holistic approach that integrates advanced catalyst design with the fabrication of 3D ordered electrode architectures. These engineered structures create efficient transport pathways, maximize the functional triple-phase boundary, and can finally unlock the full potential of poison-tolerant catalysts, enabling high performance with drastically reduced Pt loadings.

Managing phosphoric acid (PA) distribution within the catalyst layers is a critical challenge for the development of high-performance high-temperature proton exchange membrane fuel cells (HT-PEMFCs). This work introduces a novel strategy using hexamethylenediamine tetra(methylenephosphonic acid) (HDTMPA) as a functional additive in the cathode to precisely regulate the local PA environment. HDTMPA performs a dual function: its strong hydrogen-bonding interactions with PA effectively anchor the acid, which prevents the excessive flooding and poisoning of Pt catalyst sites, while its electron-rich nitrogen atoms help establish a robust proton-conduction network. Consequently, a membrane electrode assembly (MEA) with an HDTMPA-modified cathode (0.5 mgPt cm−2) achieves a peak power density of 715 mW cm−2 at 150 °C, a 42% enhancement over the unmodified baseline (503 mW cm−2). Furthermore, the modified MEA demonstrates exceptional durability, exhibiting only a 5.0% performance decay after an accelerated durability test of 10,000 cycles, compared to a 17.5% decay for the control. In-situ electrochemical analysis confirms the enhanced kinetics, validating this molecular design approach as a new avenue for developing highly stable and efficient HT-PEMFCs.

Generating a cost-effective precious-metal catalyst is essential for achieving low-cost, large-scale green hydrogen production. Since the majority of the overpotential in the proton exchange membrane water electrolyzer arises during the oxygen evolution reaction (OER), the remarkable performance of the IrO2 makes it an ideal anodic catalyst. Herein, a simple, straightforward method was used to prepare an IrO2-loaded transition-metal carbide-supported catalyst. The IrO2 nanoparticles were loaded on TiC (IrxTC1-x) and Ti2AlC (Ir(x)TAC(1-x)) at 20 to 80 wt% IrO2 loadings, using the modified Adams fusion method. A diameter of 2 nm was obtained to exhibit improved OER performance in 0.5 M H2SO4 compared with commercial IrO2. The catalysts showed a uniform distribution of IrO2 nanoparticles on the supports. Overpotentials of 260 and 250 mV were obtained for Ir80TC20 and Ir(80)TAC(20) at 10 mA cm(-2). The prepared Ir80TC20 and Ir(80)TAC(20) showed good OER activity, delivering 10 mA cm(-2) at 1.47 and 1.46 V versus RHE, respectively. The catalysts exhibited OER stability at 10 mA cm(-2) for 73 and 58 h, respectively, for Ir80TC20 and Ir(80)TAC(20). The precursor solution proved significant recyclability, and the study demonstrated a new approach to rapidly design low-cost, high-performance anodic catalysts for overall OER performance.

The intrinsically sluggish kinetics of the oxygen evolution reaction (OER) remains a critical bottleneck for efficiently electrochemical water splitting, demanding catalysts that are both highly active and robust. Herein, this work overcomes this challenge through a heterostructure engineering strategy, fabricating a strongly coupled Ce(OH)3/NiFe2O4 heterogeneous interface on nickel foam (NF). This unique configuration is shown to critically modulate the catalyst's electronic structure and electrochemical reconstruction, unlocking substantial gains in OER performance. The optimized Ce(OH)3/NiFe2O4/NF catalyst exhibits exceptional OER performance, requiring a low overpotential of only 192 mV to achieve a current density of 10 mA cm-2 and a small Tafel slope of 40.7 mV dec-1, and demonstrating outstanding long-term stability for 400 h at 400 mA cm-2 in 1 M KOH. Mechanistic studies, including pH-dependent kinetics and molecular probe experiments, reveal that the OER process predominantly follows the lattice oxygen-mediated mechanism (LOM) of Ce(OH)3/NiFe2O4/NF, bypassing the scaling relations limitations of the conventional adsorbate evolution mechanism (AEM). Moreover, the in-situ Raman spectroscopy studies reveal a substantially decreased formation potential of the active NiOOH phase, while density functional theory (DFT) computations demonstrate that the interfacial coupling optimizes electronic structure via weakened metal-oxygen bonds and a modulated O-p band center in Ce(OH)3/NiFe2O4/ NF. Besides, the integrated Pt/C||Ce(OH)3/NiFe2O4/NF electrolyzer exhibits excellent overall water splitting activity, demanding exceptionally low cell voltages of only 1.44 V and 1.58 V to achieve 10 and 100 mA cm-2, respectively. This work highlights the efficacy of rare-earth-based interface engineering in activating the LOM pathway and provides a valuable strategy for designing high-performance OER electrocatalysts.

The performance of high-temperature proton exchange membrane fuel cells (HT-PEMFCs) is severely limited by the poisoning effect and low oxygen solubility of the phosphoric acid (PA) electrolyte. To address this, we report an innovative catalyst architecture consisting of one-dimensional hollow PtNi nanochains coated with a functional ionic liquid (IL), termed PtNi@IL/C. This design creates a multifunctional interface that demonstrates exceptional PA tolerance, achieving an oxygen reduction reaction (ORR) half-wave potential of 0.840 V in a PA-containing electrolyte, which is 90 mV higher than commercial Pt/C. The IL coating synergistically enhances performance by suppressing PA adsorption on Pt active sites while simultaneously boosting O2 mass transport through its high oxygen solubility, and providing a highly efficient proton conduction pathway. As a result, a membrane electrode assembly utilizing the PtNi@IL/C catalyst achieves a high peak power density of 521 mW cm-2 at 150 degrees C. Furthermore, the catalyst exhibits outstanding durability, with a negligible 4 mV activity loss after 5000 electrochemical cycles and only a 2 % power density decay in single-cell tests, significantly outperforming the 14.3 % decay of Pt/C. This stability is attributed to the IL mechanically reinforcing the porous nanochain structure, preventing degradation. This work presents a powerful catalyst-interface engineering strategy for developing next-generation, high-performance fuel cells.

The EU Horizon2020 RISE project 778,307 "Hydrogen fuelled utility and their support systems utilising metal hydrides" (HYDRIDE4MOBILITY) worked on the commercialization of hydrogen powered forklifts using metal hydride (MH) based hydrogen stores. The project consortium joined forces of 9 academic and industrial partners from 4 countries. The work program included a) Development of the materials for hydrogen storage and compression; b) Theoretical modelling and optimisation of the materials performance and system integration; c) Advanced fibre reinforced composite cylinder systems for H-2 storage and compression; d) System validation. Materials development was focused on i) Zr/Ti-based Laves type high entropy alloys; ii) Mg-rich composite materials; iii) REMNiSn intermetallics; iv) Mg based materials for the hydrolysis process; v) Cost-efficient alloys. For the optimized AB(2 +/- x) alloys the Zr/Ti content was optimized at A = Zr78-88Ti12-22 while B=Ni10Mn5.83VFe. These alloys provided a) Low hysteresis of hydrogen absorption-desorption; b) Excellent kinetics of charge and discharge; c) Tailored thermodynamics; d) Long cycle life. Zr0.85Ti0.15TM2 alloy provided a reversible H storage and electrochemical capacity of 1.6 wt% H and 450 mAh/g. The tanks development targeted: i) High efficiency of heat and hydrogen exchange; ii) Reduction of the weight and increasing the working H-2 pressure; iii) Modelling, testing and optimizing the H-2 stores with fast performance. The system for power generation was validated at the Implats plant in a fuel cell powered forklift with on-board MH hydrogen storage and on-site H-2 refuelling. The outcome on the HYDRIDE4MOBILITY project (2017-2024) (http://hydride4mobility.fesb.unist.hr) was presented in 58 publications.

This article presents the results of an experimental study on the preparation and characterisation of metal–organic frameworks (MOFs) formed by coordination polymers of Ni(II) and Co(II) itaconates (Ni–IA and Co–IA), as well as the products of thermolysis of their mixtures. It is found that the thermolysis results in the formation of heterometallic CoNi nanoparticles enveloped in a porous carbonaceous matrix (CoNi@C core-shell structures). The catalytic effect of the as-synthesised MOFs and their CoNi@C derivatives on the hydrogenation of Mg during high-energy reactive ball milling (HRBM) in hydrogen has been studied. These catalysts were shown to increase the rate of hydrogenation of Mg during HRBM by about ninefold as compared with non-catalysed magnesium. The kinetic improvements are superior to those observed earlier for other catalysts, including Pd-doped UiO-66 MOF and Ni nanoparticles deposited onto graphene-like materials. At the same time, the achieved reacted fractions when using MOFs and their derivatives as catalysts for magnesium hydrogenation were incomplete. It was found that the use of the as-synthesised MOFs as additives to Mg during HRBM results in the slow hydrogenation of pristine magnesium at room temperature during pauses between the first milling sessions. Almost full conversion of Mg into MgH _2 was achieved when the milling vial was kept during these pauses until pressure stabilisation. Based on this observation, it was assumed that the intermediate products of MOF decomposition are more active catalysts of magnesium hydrogenation than the CoNi@C core–shell structures formed as the final MOF decomposition product.

Advancing of hydrogen and metal hydride energy technologies requires purposeful development of efficient hydrogen storage materials, particularly, tuning their composition towards optimization of hydrogen sorption properties suitable for the end-use applications. This study employed linear regression modelling to analyze hydrogen storage properties of low-, medium- and high-entropy alloys with BCC, C14- and C15-AB2 and AB5 structures found in the literature (>350 entries in total) and to make predictions based on the model further validated by additional reference data and results of own experiments. It was found that the applied model gives a good qualitative correspondence with the reference data on hydrogen sorption capacity and thermodynamics of hydrogen interaction with the alloys but has a limiting predicting capacity allowing only rough quantitative estimations. It was also concluded that the unit cell volume, valence electron concentration, and, to a lesser extent, electronegativity mismatch, exhibit strong effects on the hydrogen sorption properties of the studied alloys while the influence of other factors including the mixing entropy is much less pronounced.

HySA Systems and TF Design have recently developed a single-stage prototype high-pressure metal hydride hydrogen compressor (MHHC) which is able to compress hydrogen from 100 to >700 bar at the working temperatures from 20 to 150 degrees C, with estimated productivity about 1 Nm(3)/h. The MHHC comprises of two 2 m-long fibre-wound high-pressure MH containers developed by the authors earlier and assembled in two modules operating in a mode of a cyclic lower-pressure H-2 absorption (on cooling) and high-pressure H-2 desorption (on heating). The containers operate using a self-developed multicomponent C14 Laves type Ti-based AB(2) intermetallic alloy. The article considers phase-structural and hydrogen sorption properties of the utilized metal hydride material, hydrogen compression performances of the metal hydride container, as well as layout and the expected performance characteristics of the compressor assembly.

In the search of sustainable energy solutions, proton exchange membrane water electrolyzers (PEMWEs) have emerged as a promising alternative for sustainable clean hydrogen production. This study focuses on synthesis and characterization of Ruthenium (Ru)-modified iridium oxide (IrO2) catalysts. The anode is the principal reason for the high overpotential of PEMWEs and it also greatly increases the cost of the electrolyzers. IrO2 is highly stable and corrosion-resistant, particularly in acidic environments, making it a durable catalyst for the oxygen evolution reaction (OER) in PEMWEs, though it suffers from a relatively high overpotential. Ruthenium oxide (RuO2), on the other hand, is more catalytically active with a lower overpotential, but is less stable under the same conditions. In this study, the goal was to improve the catalytic activity and stability of the anode catalyst, IrO2, through the controlled incorporation of Ru and to reduce overall catalyst cost due to the reduced iridium content. This synergistic combination allows for better performance in terms of conductivity, efficiency, and durability, making Ru-modified IrO2 an ideal catalyst for OER in PEMWE applications. The Adams fusion method was adapted and used to synthesize the catalysts. The modified catalysts were characterized using analytical instruments. These analyses provided insights into the structural, morphological, and electrochemical properties of the Ru-modified IrO2 catalysts.

The air compressor holds paramount importance due to its significant energy consumption when compared to other Balance of Plant components of polymer electrolyte membrane (PEM) fuel cells. The air supply system, in turn, plays a critical role in ensuring the stable and efficient operation of the entire fuel cell system. To enhance system efficiency, the impact of varying the stoichiometric ratio of air and air pressure was observed. This investigation was carried out under real loading conditions, replicating the conditions experienced by the power module when fuel cells are in use within a forklift. The air compressor can be operated at different pressure and excess air ratios, which in turn influence both the fuel cell’s performance and the overall efficiency of the power module system. Our research focused on assessing the performance of PEM fuel cells under different load cycles, adhering to the VDI60 requirements for forklift applications. This comprehensive examination encompassed the system’s minimum and maximum load scenarios, with the primary goal of optimizing excess air and pressure ratio parameters, especially under dynamic load conditions. The results revealed that higher air pressures and lower excess air ratios were conducive to increasing system efficiency, shedding light on potential avenues for enhancing the performance of PEM fuel cell systems in forklift applications.

IrO2 is a current state-of-the-art catalyst for polymer electrolyte membrane water electrolyser (PEMWE) applications due to its high stability during the oxygen evolution reaction (OER). However, its activity needs to be significantly improved to justify the use of such a high-cost material. In this study, the activity of the IrO2 catalyst was improved by optimising and comparing two synthesis methods: the modified Adams fusion method (MAFM) and the molten salt method (MSM). Optimum OER performances of the IrO2 catalysts synthesised with the two synthesis methods were obtained at different temperatures. For the MAFM, a synthesis temperature of 350 °C produced the IrO2 catalyst with an overpotential of 279 mV and the highest OER stability of ~ 82 h at 10 mAcm−2. However, for the MSM, the lowest overpotential of 271 mV was observed for IrO2 synthesised at 350 °C, while the highest stability of ~ 75 h was obtained for the IrO2 synthesised at 500 °C.

A first-principles method based on the density functional theory (DFT) was employed in conjunction with quasi-harmonic Debye model to investigate the structural, elastic, and thermodynamic properties of a series of AB2-based Laves phases alloys and their hydrides. Simulation results revealed that the studied materials possess the Laves phase structure with lattice parameters comparable to experimental findings. For the first time, to the best of our knowledge, mixing entropy determined using Debye model was used to classify alloys into (Low- Medium-High Entropy Alloys) LEA, MEA and HEA categories rather than the commonly used ideal solution model, which is often inaccurate and ignores the impact of temperature. Lattice analyses of the alloy materials indicated that cell volume increases with the addition of elements, while the enthalpy of hydride formation indicates that hydrogen absorption in these alloys is exothermic and that the 3.00 H/F.U configuration is energetically stable. The alloys and their hydrides are metallic with no band gap at the Fermi level. The thermodynamic properties were studied using the quasi-harmonic Debye model and it was found that Bulk modulus decreases with increasing volume, and the hydrides possess lower bulk modulus compared to their metallic counterparts. Moreover, Debye temperature decreases with the gradual addition of elements, indicating weaker chemical bonds in ternary and other alloys. All hydrides have lower Debye temperature than their parent alloy materials. Finally, The alloys are classified into low-, medium-, and high-entropy alloys based on mixing entropy calculated using the Debye model. TiMn2 is classified as a low-entropy alloy, ZrMn2, Ti0.5Zr0.5Mn2, and Ti0.5Zr0.5MnFe as medium-entropy alloys, and Ti0.5Zr0.5(MnCr)2, Ti0.5Zr0.5Mn2/3Fe2/3Cr2/3, and Ti0.5Zr0.5Mn0.5Fe0.5Cr0.5Ni0.5 as high-entropy alloys.

Recently, the utilization of phase change materials (PCM) for the heat storage/recovery of the metal hydride's reaction heat has received increasing attention. However, the poor heat management process makes hydrogen sorption very slow during heat recycling. In this work, the H2 charging/discharging performance of a metal hydride tank (MHT) filled with LaNi5 and equipped with a paraffin-based (RT35) PCM finned jacket as a passive heat management medium is numerically investigated. Using a two-dimensional mathematical model validated with our in-house experiments, the effects of design parameters such as PCM thermophysical properties and the fin size on hydrogen charging/discharging times of the MHT are investigated systematically. The results showed that the PCM's melting point and apparent heat capacity have a conflicting impact on the hydrogen sorption times, i.e., the low melting point and high specific heat capacity reduce the H2 charging time. In contrast, the hydrogen discharging time follows the opposite trend. As a result, a multi-objective optimization was conducted to simultaneously minimize the H2 charging/discharging times using the thermal properties and size of the PCM. The optimum solutions selected from the Pareto front show that the PCM melting point should be around 42-43 degrees C for fixed hydrogen ab/desorption pressures of 10/1.5 bar. Moreover, the comparison between the MHT-PCM using the optimized PCM and reference PCM showed that the former reduced the hydrogen charging/discharging times by 48.6 % and 4 %, respectively. At the same time, the hydrogen storage efficiency of the optimal design is 100 % as compared to 96 % for the reference design. Besides, among the practical PCMs, inorganic PCMs (salt hydrates and eutectics) display favorable hydrogen charging time below 3000 s at the expense of hydrogen discharging time (above 7000 s) in our case study.

Thermal batteries utilizing metal hydride pairs are gaining tremendous research appeal for their applications in thermochemical energy storage. The pair consisting of a high-temperature metal hydride (HTMH: Mg-based hydride) and a low-temperature metal hydride (LTMH: AB2 type hydride) is attractive due to its relatively high energy storage density and medium energy storage efficiency. The energy storage efficiency can be significantly increased by improving the heat discharging performance of the thermal battery. In this study, we experimentally explore the heat releasing performance of an MgH2/(TiZr)(MnFeCr)2-based thermal battery. More specifically, the effects of LTMH bed heat transfer conditions on the heat discharging performance were briefly discussed. These heat transfer conditions include natural convection, forced convection, and resistive heating. The results showed that when operating the LTMH bed under active heat transfer conditions (forced convection or resistive heating), the thermochemical energy storage density varies between 1500 and 1820 kJ/ kg-Mg with relatively high-temperature lift (heat upgrade) between 47 and 55 degrees C. On the other side, the thermal battery discharges heat at a relatively high specific power, ca. 100-225 W/kg-Mg, which can be a benefit for heat-to-work conversion applications using organic or steam Rankine cycles.

A study was conducted on the power system of a forklift equipped with PEM fuel cells. A fuel cell assembly relies on several components for proper functioning, and among these, the air compressor holds paramount importance due to its significant energy consumption when compared to other Balance of Plant components. The air supply system, in turn, plays a critical role in ensuring the stable and efficient operation of the entire fuel cell system. To enhance system efficiency, we delved into the impact of varying the stoichiometric ratio of air and air pressure on the validated and optimized power module model. This investigation was carried out under real loading conditions, replicating the conditions experienced by the power module when fuel cells are in use within a forklift. The air compressor, being a pivotal component of a PEM fuel cell system, can be oper-ated at different excess air and pressure ratios, which in turn influence both the fuel cell's performance and the overall efficiency of the power module system. Our research focused on assessing the performance of polymer electrolyte membrane (PEM) fuel cells under different load cycles, adhering to the VDI60 requirements for forklift applications. This comprehensive examination encompassed the system's minimum and maximum load scenarios, with the primary goal of optimizing excess air and pressure ratio parameters, especially under dynamic load conditions. The results revealed that higher air pressures and lower excess air ratios were con-ducive to increasing system efficiency, shedding light on potential avenues for enhancing the performance of PEM fuel cell systems in forklift applications.

The high cost of catalyst materials suitable for the oxygen evolution reaction (OER) in polymer electrolyte membrane water electrolyzers (PEMWE) is still a major hurdle that needs overcoming before commercial PEMWE can have a meaningful impact as a technology in the hydrogen economy. Metal oxides based on precious metals are currently still the most reliable and most used materials as catalysts in PEMWE; however, alternative or modified materials are desirable to help reduce the cost associated with the catalyst component. In this study, we report on binary metal oxide catalysts based on Ru and Ni. Ni-based electrodes are typically used in alkaline water electrolyzers due to their high performance, robustness and low cost; however, Ni and NiO electrodes do not show promising performance in acidic environments due to corrosion. By combining NiO with acid stable RuO2, we have demonstrated that the performance of the RuO2 catalyst can be improved and due to the lower cost of Ni, the cost of the catalyst can ultimately be reduced. The Ni addition was limited to 10 mol% to achieve improved OER performance followed by noticeable performance degradation as the Ni composition was increased. The metal oxide catalysts were synthesized via a modified Adams fusion method that produced nano-sized catalysts with superior performance compared to a state-of-art commercial RuO2 catalyst. Physical characterizations were performed via high-resolution transmission electron microscopy, X-ray diffraction, energy dispersive X-ray, and Brunauer Emmett Teller analyses. OER performances were evaluated via cyclic voltammetry, linear sweep voltammetry, chronopotentiometry, and chronoamperometry analyses.

Abstract IrO2 is a commonly used catalyst for polymer electrolyte membrane water electrolyzer (PEMWE) applications due to its high stability during the oxygen evolution reaction (OER). However, its activity needs to be significantly improved to justify the use of such a high-cost material. In this study, the activity of the IrO2 catalyst was improved by optimizing two synthesis methods i.e., the modified Adams fusion method (MAFM) and the molten salt method (MSM). Physical characterizations were done via x-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and brunauer-emmett-teller (BET) analyses. The OER performances were evaluated ex-situ via cyclic voltammetry (CV), linear sweep voltammetry (LSV), and chronopotentiometry (CP) analyses. The XRD results showed that the IrO2 crystallinity and crystallite size increased with increasing temperatures. Optimum OER performances of the IrO2 catalysts were obtained at different temperatures for the two synthesis methods. For the MAFM, a synthesis temperature of 350℃ produced the IrO2 catalyst with the highest OER activity and stability. However, for the MSM, a synthesis temperature of 350℃ produced the IrO2 catalyst with the highest activity while a synthesis temperature of 500℃ produced the catalyst with the highest stability. The IrO2 catalysts showed significantly improved OER performances compared to a commercial IrO2 catalyst under the study’s test conditions.