A photochromic nano-system via self-recovery for stable photocatalytic hydrogen evolution by optimizing TiO2 surface energy

Abstract

TiO₂-based photocatalysts are promising candidates for photocatalytic hydrogen evolution that utilizes solar energy due to their low cost and high stability, but their activities are usually limited by the drawbacks of TiO₂. Specifically, the fluctuation of surface energy, disturbed by light irradiation, can change the relative stability of the TiO₂ exposed crystal faces, which has a great influence on the photocatalytic activity. Focusing on this problem, we built a bromine containing TiO₂-based photochromic self-recovery system to immobilize bromine in the photocatalyst after photocatalysis. After a series of charge migration experiments, the photocatalysis of our photochromic system was clarified, and proved that TiO₂ is the final electron accepter. This conclusion further emphasizes the importance of optimizing the TiO₂ surface energy to promote TiO₂-based photocatalysts. As a result, a sustained effect of reducing TiO₂ surface energy can be achieved by repeating the bromine adsorption to harvest stable photocatalytic hydrogen evolution under ultraviolet and visible light irradiation.