Emerging trends in materials for water splitting catalysts in hydrogen production

Hydrogen is a crucial element for decarbonization, as its conversion into energy results in zero CO 2 emissions, leaving only water as a byproduct. However, pure hydrogen is rare on Earth, necessitating various production methods. Among these, water splitting is a sustainable solution, where water molecules are dissociated into hydrogen and oxygen atoms. Despite its potential, kinetic barriers in hydrogen and oxygen formation lead to overpotential during electrochemical reactions, increasing energy consumption. Catalysts are essential for reducing overpotential, accelerating reaction rates, and minimizing power requirements. Recent studies have demonstrated advancements in catalyst materials such as metal oxides, transition metals, and non-metallic catalysts. For instance, IrO₂ and RuO₂ catalysts achieve high current densities of up to 1620 mA/cm² at 70°C with an overpotential of 2.1 V, while transition metal phosphides like Ni₂P show low overpotentials of 52 mV for hydrogen evolution reaction and 154 mV for oxygen evolution reaction. Furthermore, techniques such as defect engineering and heterostructure design have enhanced catalyst stability and efficiency, achieving turnover frequencies exceeding 32.86 s⁻¹ at 20 mV. The generation of hydrogen via water splitting is advancing swiftly; however, its practical application is currently constrained by kinetic overpotentials, long-term performance stability, cost, and inconsistent benchmarking. Recent advancements in defect engineering, heterostructure design, and the development of heavier, more heteroatom-substituted PGM-based, transition-metal-based, MXene-based, doped-dichalcogenide-based, and carbon-based materials have enhanced intrinsic activity and stability while reducing material intensity. This review correlates synthesis-controlled features with observable performance and feasibility and underscores the trade-offs pertinent to scale-up. This study conclusively address research goals that will facilitate the transformation of laboratory advancements into economically viable, practical green hydrogen. This review discusses advancements in catalyst synthesis, characterization techniques, challenges in catalyst development, proposed solutions, industrial applications, environmental benefits, and sustainability considerations. By addressing these factors, water splitting technology can be optimized for large-scale hydrogen production while minimizing costs and environmental impact. • Comparative analysis of novel sustainable water-splitting catalysts. • Links synthesis methodologies for measured performance. HER/OER. • Performs risk evaluation of classes concerning fuel scale-up, cost, and environmental issues associated with the catalyst. • Identifies specific research deficiencies and prospective considerations in catalyst design. • Integrates the latest advancements, including PGM, TM, MXene, and carbon-based technologies.