A Combination of Two Visible-Light Responsive Photocatalysts for Achieving the Z-Scheme in the Solid State

Abstract

The light reaction in natural photosynthesis is generally recognized as one of the most efficient mechanisms for converting solar energy into other energy sources. We report herein on a novel strategy for generating H₂ fuel via an artificial Z-scheme mechanism by mimicking the natural photosynthesis that occurs in green plants. Designing a desirable photocatalyst by mimicking the Z-scheme mechanism leads to a conduction band that is sufficiently high to reduce protons, thus decreasing the probability of charge recombination. We combined two visible light sensitive photocatalysts, CdS and carbon-doped TiO₂, with different band structures. The used of this combination, that is, CdS/Au/TiO_1.96C_0.04, resulted in the successful transfer of photogenerated electrons to a higher energy level in the form of the letter ‘Z’. The system produced about a 4 times higher amount of H₂ under irradiation by visible light than CdS/Au/TiO₂. The findings reported herein describe an innovative route to harvesting energy by mimicking natural photosynthesis, and is independent of fossil fuels.