Global prospects of low-carbon photocatalytic hydrogen based on regionalised optimisation

Photocatalytic hydrogen has gained interest as a solar-driven pathway for renewable hydrogen production, particularly in regions with abundant sunlight and remote locations with limited industrial infrastructure. However, its large-scale potential and environmental performance remain unexplored. This study aims to estimate the global production potential of photocatalytic hydrogen under realistic environmental, technological and land-use constraints based on a representative system, and to assess its prospective carbon footprint in 2050. A bottom-up, regionalised optimisation framework was developed by coupling an experimental kinetic model with global datasets of direct normal irradiance and air temperature (11,301 points worldwide). The photocatalytic hydrogen carbon footprint was optimised for each location. Land-use filtering was applied to retain only degraded and desert soils outside key biodiversity areas. Results show that the global production potential reaches 4.58 Mt H 2 per year, associated with a carbon footprint of 10.27 Mt CO 2 eq per year. Although this production potential represents 1.31% of the projected 2050 hydrogen demand, these greenhouse gas emissions correspond to 0.15% of the global climate change carrying capacity, emphasising the need to contextualise performance relative to environmental thresholds. Overall, the results identify the locations where photocatalytic hydrogen could become feasible under future conditions, while showing that its global production contribution remains conditioned by further improvements in catalyst performance, key material carbon footprints, and light-to-fuel conversion.