erformance of photocatalysts. A large number of new semiconductor photocatalysts, such as CdS, SnO2, ZnO, ZnS, and WO3, have been explored since Fujishima and Honda [8] first achieved photocatalytic splitting of water by a TiO2 electrode. Among these photocatalysts, TiO2 is considered an almost ideal example because it is cheap, nontoxic, stable, reproducible, and recyclable [9]. However, there are still two major bottlenecks limiting the industrial application of nanosized TiO2 (nano‐TiO2) as a photocatalyst: (1) it only responds to ultraviolet (UV) light, so the use efficiency of solar energy is very low because UV light is less than 5% of the solar spectrum [5,10,11]; and (2) the recombination rate of photoexcited charge carriers is high, so the quantum