Principles on design and fabrication of nanomaterials as photocatalysts for water-splitting

As an energy carrier, hydrogen has been extensively studied to satisfy the increasing demand on green energy. Efficiently producing hydrogen from water under sunlight is one of the challenging and important topics in hydrogen energy technology. Photocatalyst plays a critical role for the photo-production of hydrogen from water. It is essential to design novel photocatalysts with enhanced efficiency for the increasing demand on energy. In this paper, recent development on novel strategies to design photocatalysts and novel nanomaterials for efficient production of hydrogen is comprehensively reviewed based on fundamental principles. The strategies, including codoping, hydrogenation, defect engineering, sensitization, formation of heterojunction, metal decoration, band-edge-states modification, and novel designs of cell structures (tandem cell), are systematically discussed. Nanomaterials, including oxides (such as TiO2, Ta2O5, Fe2O3 and SrTiO3) and nitrides (such as GaN, graphitic carbon nitride, and Ta2N3), are investigated. It is shown that these strategies can generally apply to all of materials, such as oxide and nitride semiconductors. It is believed that maximal conversion efficiency could be achieved by optimizing the electronic structures of photocatalysts and engineering the structures of cells.