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

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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/TiO1.96C0.04, 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.