Long‐Living Holes in Grey Anatase TiO(2) Enable Noble‐Metal‐Free and Sacrificial‐Agent‐Free Water Splitting

Titanium dioxide has been the benchmark semiconductor in photocatalysis for more than 40 years. Full water splitting, that is, decomposing water into H(2) and O(2) in stoichiometric amounts and with an acceptable activity, still remains a challenge, even when TiO(2)‐based photocatalysts are used in combination with noble‐metal co‐catalysts. The bottleneck of anatase‐type TiO(2) remains the water oxidation, that is, the hole transfer reaction from pristine anatase to the aqueous environment. In this work, we report that “grey” (defect engineered) anatase can provide a drastically enhanced lifetime of photogenerated holes, which, in turn, enables an efficient oxidation reaction of water to peroxide via a two‐electron pathway. As a result, a Ni@grey anatase TiO(2) catalyst can be constructed with an impressive performance in terms of photocatalytic splitting of neutral water into H(2) and a stoichiometric amount of H(2)O(2) without the need of any noble metals or sacrificial agents. The finding of long hole lifetimes in grey anatase opens up a wide spectrum of further photocatalytic applications of this material.