Catalyst innovations for green hydrogen: recent advances, challenges, and future prospects.

Hydrogen has emerged as a key energy carrier for achieving global decarbonization and enabling the transition to sustainable energy systems. Among the various production pathways, green hydrogen generated through water electrolysis using renewable electricity offers a carbon-free alternative to conventional fossil fuel-based hydrogen production. However, the efficiency, cost, and durability of water electrolysis technologies are strongly dependent on the development of advanced electrocatalysts. This study reviews the recent progress in catalyst materials and design strategies for water-splitting reactions, focusing on both hydrogen evolution and oxygen evolution reactions. This study examines the performance and limitations of conventional noble-metal catalysts alongside emerging Earth-abundant alternatives such as transition metal oxides, sulfides, phosphides, and alloyed or doped nanostructures. Key catalyst design strategies, including doping and alloying, single-atom and bifunctional catalysts, and catalyst support and layer engineering, are discussed in relation to their activity, stability, and scalability. This study also highlights the major technical challenges, including catalyst degradation, limited long-term stability, and high production costs. Furthermore, future research directions are explored, emphasizing the integration of machine learning and computational design for catalyst discovery, sustainable recycling and material utilization, and pathways toward large-scale commercialization of the developed catalysts. Overall, advancing efficient, durable, and low-cost electrocatalysts is essential for accelerating the deployment of green hydrogen technologies and supporting the global transition to a clean and sustainable energy economy.