TiO2-based photocatalytic generation of hydrogen from water and wastewater

Among emerging techniques for energy recovery, photocatalytic water/wastewater splitting has been recognized as a sustainable option to generate hydrogen. In this work, the working mechanism and performance output between different photocatalytic systems are evaluated after sorting into mono-metallic TiO2, bi-metallic TiO2, and non-TiO2 composite photocatalysts for hydrogen energy recovery via water and wastewater splitting. This comparative analysis is made in relation to the electronic structure, charge carrier dynamics, specific surface area, active sites, and light adsorption potential along with the optical properties of the photocatalysts (e.g., electrons-holes trapping/separation/migration, average lifetime of charge carriers, and activation energy required for H2 recovery). The performance evaluations between different photocatalytic systems are also made in terms of the key metrics (e.g., reaction kinetic rate (r), quantum yield (QY), and figure of merit (FOM)). Considering the present challenges and future of this technique, we propose a feasible roadmap to help establish realistic energy management options using TiO2-based catalytic systems.