Z-Scheme Photocatalytic System Utilizing Separate Reaction Centers by Directional Movement of Electrons

Increasing of electron-hole separation is crucial to the improvement in the activity of photocatalyst. Photosynthesis involving the Z-scheme mechanism provides a unique process to utilize the solar energy by various biosystems and natural lives through effective electron-hole pair separation. This is an inspiring approach to the solar energy conversion for, e.g., photocatalysis of H-2 evolution. Although some progress has been made in this technological area, a nontoxic photo catalytic system with a wide pH range by directional electron transfer with simple coupling of components has still not been achieved. In this study, a photocatalytic system mimicking the Z-scheme without electron mediators was developed, in which PS I and PS II were separated in space but operated simultaneously, resulting in two photochemical reactions that operate in parallel. This approach of utilizing two light beams including UV and visible light provides a new route for efficient conversion of solar energy. This nontoxic system has demonstrated higher stability in a wide pH range from 1 to 13, higher effectiveness in separating electron-hole pairs, and greater photoactivity than a single component system. Such improvement is attributed to the directional electron transfer actuated by the photoexcitation of TiO2 and heteropoly blue, respectively.