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.