Hybrid bibliometric and literature review of green hydrogen production via photocatalytic water splitting: trends, advances, and future directions

Green hydrogen is a pivotal vector for decarbonization, and photocatalytic water splitting (PWS) offers a direct, sunlight-to-fuel pathway with minimal carbon footprint. This paper presents a hybrid bibliometric and literature review to map the evolution, impact, and technological advances in PWS for green hydrogen. The analysis using the Scopus database (2014 to 2025) on publications, citations, and collaboration networks computes standard bibliometric indicators and visualizes co-authorship and keyword structures with network-mapping tools. It is observed that there is a rapid rise in outputs and dense international collaboration, with China and India as productivity hubs and strong links to Saudi Arabia and the United States. Research trends converge on TiO₂, g-C₃N₄, Z-/S-scheme heterojunctions, single-atom catalysts, MOF/COF composites, and non-noble co-catalysts (e.g., Ni₂P, CoP, MoS₂), alongside device-level advances in PEC cells, membranes, and microreactors. Low unbiased solar-to-hydrogen (STH) efficiency, dependence on noble metals, stability limits, and non-standardized testing are among the critical research areas. Future research should also focus on multi-component photocatalysts, seawater-compatible operation, visible-light operation, reactor-aware discovery, and physics-informed AI/ML.