Photoelectrochemical pathways to green hydrogen. analysis, overview, and foresight

Photoelectrochemical (PEC) water splitting represents a promising pathway for sustainable hydrogen production by directly converting solar energy into chemical fuel within a single integrated system. Despite decades of intensive research on semiconductor photoelectrodes, PEC technologies remain largely confined to laboratory-scale demonstrations due to limited solar-to-hydrogen efficiency, insufficient operational stability, and challenges related to scalability and system integration. This review provides a critical and technology-oriented synthesis of recent advances in PEC hydrogen generation, focusing on material platforms, device architectures, and modification strategies that govern performance and durability. Emphasis is placed on oxide, nitride, chalcogenide, and hybrid photoelectrode systems, alongside interface engineering approaches such as heterojunction formation, defect and vacancy control, surface passivation, and cocatalyst integration. Beyond materials-level considerations, the analysis situates PEC water splitting within a broader technoeconomic and system context, addressing cost drivers, integration with variable renewable energy supply, and infrastructure constraints. Drawing on representative academic results and patent-informed technological developments, the review identifies key bottlenecks limiting practical deployment and highlights pathways for translating laboratory advances toward demonstrator-scale systems. On this basis, a foresight-oriented roadmap extending to 2035 is proposed, outlining strategic milestones in efficiency, stability, system integration, and policy alignment required for PEC water splitting to emerge as a viable contributor to the future hydrogen economy.