A comprehensive review of photocatalytic hydrogen evolution incorporating mechanisms and key parameters accompanying future outlook

The growing demand for sustainable and carbon-neutral energy carriers has intensified interest in hydrogen production via solar-driven photocatalysis. Despite extensive research on photocatalytic water splitting, practical implementation remains limited by low efficiency, stability issues, and the complexity of real-water matrices, particularly seawater. Unlike existing reviews that primarily emphasize catalyst design, this review uniquely integrates reaction parameters with water-source-specific behavior to provide a comprehensive understanding of photocatalytic hydrogen evolution. Key operational variables including water type, synthesis method, pH, temperature, light source, dissolved oxygen, and catalyst loading are systematically analyzed in relation to performance trends. A bibliometric analysis reveals rapid global growth in this field, dominated by China, India, and the United States, while highlighting underrepresentation in regions such as Malaysia. The parametric analysis identifies seawater salinity, ion interference, and operational conditions as critical bottlenecks limiting hydrogen yield and catalyst durability. By consolidating mechanistic insights, parameter-dependent effects, and bibliometric trends, this review outlines targeted research directions and provides a roadmap toward efficient, scalable, and seawater-compatible photocatalytic hydrogen production.