Photocatalytic Partial Water Oxidation Promoted by a Hydrogen Acceptor‐Hydroxyl Mediator Couple

Hydrogen peroxide (H 2 O 2 ) is an important chemical in synthetic chemistry with huge demands. Photocatalytic synthesis of H 2 O 2 via oxygen reduction and water oxidation reactions (ORR and WOR) is considered as a promising and desirable solution for on‐site applications. However, the efficiency of such a process is low due to the poor solubility of molecular oxygen and the rapid reverse reaction of hydroxyl radicals ( • OH) with hydrogen atoms (H). Here, a strategy is proposed to boost the H 2 O 2 evolution via oxidation of water by employing a H acceptor ( A , nitrocyclohexane), an • OH mediator ( M , dioxane), and a photocatalyst (CdS nanosheets). While • OH radicals are stabilized by dioxane to produce ketyl radicals prior to the formation of H 2 O 2 , H atoms are effectively utilized in the generation of cyclohexanone oxime, an important intermediate in the production of Nylon 6. The system displays a rapid kinetic accumulation of H 2 O 2 (0.13 min −1 ) to a high concentration (6.6 m M ). At optimum reaction conditions, a high quantum efficiency (16.6%) and light‐to‐chemical conversion efficiency (4.9%) can be achieved under 410 nm irradiation.