Mechanistic insights and challenges in noble metal nanocatalysts for green hydrogen production via water splitting

Green hydrogen production via electrochemical water splitting is a key strategy for global decarbonization, offering a scalable and sustainable route to clean energy. When integrated with renewable sources such as solar and wind, it enables large-scale electrification with minimal environmental impact. The development of efficient electrocatalysts is essential to advance water electrolysis by lowering overpotential, reducing Tafel slopes, and achieving high activity at low cost. Noble metal catalysts, including Ru, Ir, and Pt, exhibit outstanding performance due to their high intrinsic activity, stability, and abundant active sites. However, challenges remain in optimizing crystal phases, designing ultrathin nanostructures, and engineering defect-rich surfaces to enhance catalytic efficiency further. Recent progress in operando and in situ techniques such as atomic-resolution electron microscopy, UV–vis spectroscopy, and X-ray absorption spectroscopy has provided valuable insights into structural and electronic evolution during HER and OER. These studies emphasize the role of crystal phase transitions and electronic configurations in governing reaction intermediates. Despite significant advances, universal activity descriptors, especially in alkaline media, remain the subject of debate. Future research should focus on rational catalyst design to control reaction pathways, increase active site exposure, and exploit electronic effects for efficient, scalable hydrogen production.