Toward the efficient utilization of solar energy for hydrogen production through photocatalytic reforming: A literature and patent review

The increasing global energy demand and urgent need to curb greenhouse gas emissions have intensified efforts to develop solar-driven hydrogen production technologies. Photocatalytic reforming of organic substrates – including biomass-derived compounds, organic species, and wastewater – has emerged as a promising route capable of simultaneously generating hydrogen and degrading pollutants. Recent advances have led to substantial improvements in photocatalyst performance, with reported hydrogen evolution rates ranging from below 1 mmol/g cat ‧h for non-metal-doped semiconductors to over 50 mmol/g cat ‧h for optimized dye-sensitized and heterojunction systems, and up to 112 mmol/g cat ‧h for functionalized COF nanosheets. Apparent quantum yields span a similar breadth, from modest values below 1% to over 80% in state-of-the-art organic frameworks. Wastewater valorization studies demonstrate both environmental and energetic benefits, achieving hydrogen productivities up to 6.5 mmol/L in solar pilot plants and pollutant removal efficiencies exceeding 90% for dyes and pharmaceuticals. Techno-economic analyses indicate that integrated hydrogen–wastewater systems can reduce levelized hydrogen costs, with some configurations achieving internal rates of return above 10% and hydrogen yields approaching 800 L H₂ per kg of organic removed. This review integrates scientific literature with international patent trends, providing a unified assessment of photocatalyst development, sacrificial agent strategies, and photoreactor design innovations. Building on these insights, the review delineates a forward-looking roadmap that prioritizes photocatalyst performance, wastewater matrices, scalable reactor architectures, and techno-economic integration as key research and engineering directions required to translate photocatalytic reforming from laboratory studies to commercially viable, large-scale hydrogen production.