Nanocatalysts in photocatalytic and electrochemical hydrogen production

With the growth in energy demand around the globe, researchers have highly developed interest in producing environmentally friendly hydrogen by water splitting. This review discusses the electrocatalytic and photocatalytic nanocatalyst for water splitting process for obtaining clean hydrogen from water and renewable energy sources. Cutting-edge materials that possess outstanding performance as sunlight-driven catalysts have been featured here including semiconductor nanoparticles, hybrid composites, carbon-based materials, and plasmonic nanostructures and approaches such as framework doping, nanocomposite design, and defect engineering. The emerging hybrid architectures integrating photo- and electrocatalysis, photoelectrochemical (PEC) devices, and system integrations relevant to fuel cells and renewable-powered electrolysis have been mapped. Sustainability controls such as circular economy feedstocks, life cycle/techno-economic assessment, and policy needs are discussed. Finally, we outline machine learning, in situ characterization, and earth-abundant catalyst platforms as cross-cutting directions to bridge laboratory advances with durable, scalable, and commercially viable hydrogen production.