Hydrogen Generation on Metal/Mesoporous Oxides: The Effects of Hierarchical Structure, Doping, and Co-catalysts

Photocatalytic water splitting for the generation of hydrogen fuel under solar-light illumination is a sustainable and renewable energy technology to solve environmental issues. Numerous attempts have been made to develop a stable and efficient visible-light-driven photocatalyst for hydrogen evolution. Several factors (e.g., morphology, surface area, crystallinity, and band structure of the catalyst and charge transfer at the oxide-metal interface) have been shown to affect the solar-to-hydrogen energy-conversion efficiency. Recently, various modification strategies for metal-oxide photocatalysts, including cation/anion doping for visible-light harvesting, have been suggested. Furthermore, a series of new engineering methods that introduce co-catalysts, dye sensitizers, and quantum dots appear to improve the photocatalytic activity for hydrogen generation. In this article, we give an overview of the molecular-scale factors that influence the efficiency of hydrogen evolution and outline recent progress of commonly used engineering strategies that search for higher efficiency in the generation of hydrogen. Specifically, nanostructured photocatalysts, including hierarchical mesoporous structures, were investigated for the production of hydrogen. Finally, great achievements in the emerging field of surface-plasmon-induced hot-electron-driven hydrogen generation are discussed.