Photocatalytic and photoelectrochemical H₂ generation for sustainable future: Performance improvement, techno-economic analysis, and life cycle assessment for shaping the reality

Photocatalytic (PC) and photoelectrochemical (PEC) water splitting to produce H₂ as clean fuel utilizing renewable solar irradiation offers an excellent opportunity to address the global energy crisis and reduce carbon emissions. For improving the solar to hydrogen (STH) efficiencies, modifying the material characteristic with dye sensitization, co-catalyst doping, engineered nano-structuring, formulating heterojunction and Z-schemes, and different sacrificial agents are used, resulting in higher H₂ efficiencies than the unmodified ones. In the last decade, the growing interest in developing and improving soft polymeric photocatalysts (carbon nitrides, linear π conjugated polymers, CMP, COF, etc.) and plasmonic photocatalysts have also emerged significantly. However, for the industrial scale-up and reducing the cost of renewable H₂, efficient photo-reactor design with integrated separation, collection, and storage facilities are more crucial with the Techno-Economic Analysis (TEA) and Life Cycle Assessment (LCA) of the proposed production schemes. This article is focused on bridging the gaps to upscale the lab-scale research in PC/PEC water splitting to industrial scale by extensively reviewing the existing photo-reactor design, process integration, process scale-up, TEA, and LCA. With this, the recent advances and approaches in modifying photocatalytic materials are reviewed starting with the mechanism, nature, and properties of the PC and PEC H₂ generation. Thus, this article will provide a complete overview of the solar-based photocatalytic and photoelectrochemical H₂ generation, technical barriers to implementation on a large scale with the current trends and solutions, with a few potential directions for future research, development, and deployment.