Development of Mixed-Anion Photocatalysts with Wide Visible-Light Absorption Bands for Solar Water Splitting

Rapid fossil-fuel consumption, severe environmental concerns, and growing energy demands call for the exploitation of environmentally friendly, recyclable, new energy sources. Fuel-producing artificial systems that directly convert solar energy into fuels by mimicking natural photosynthesis are expected to achieve this goal. Among them, the conversion of solar energy into hydrogen energy through the photocatalytic water-splitting process over a particulate semiconductor is one of the most promising routes due to advantages such as simplicity, cheapness, and ease of large-scale production. Abundant metal oxide photocatalysts have been developed in the last century, but most are only active under UV-light irradiation. To harvest a much wider range of the solar spectrum, the development of photocatalysts with wide visible-light absorption bands has become increasingly popular this century. Herein, a brief overview of materials developed for promising solar water splitting, with an emphasis on a mixed-anion structure and wide visible-light absorption bands, is presented, with some basic information on the principles, approaches, and research progress on the photocatalytic water-splitting reaction with particulate semiconductors. Typical progress on research into one- and two-step (Z-scheme) overall water-splitting systems by utilizing mixed-anion photocatalysts is highlighted, together with research strategies and modification methods.