A universal molecular oxygen-mediated photocatalysis strategy to boost visible-light induced hydrogen evolution through partial water splitting

A universal oxygen-mediated, stepwise strategy is proposed for efficiently inducing visible-light photocatalytic partial water decomposition into hydrogen over various semiconductor photocatalysts with conduction band bottoms below the single-electron oxygen reduction potential. In this scenario, molecular O can be transformed into reactive oxygen species, serving as both an oxidant and a homogeneous catalyst for producing hydrogen from alkaline aqueous solution containing various organic substrates. Further enhancement the performance is achieved by doping with phosphorous and oxygen, which constructs a local internal electric field and introduces sulfur vacancies, thereby facilitating the transport of photogenerated charge carriers, particularly on a representative CdS photocatalyst. The optimal hydrogen evolution performance reaches 2321.4 and 8521.4 μmol·g·h in methanol and formaldehyde solution systems, respectively, with an apparent quantum efficiency exceeding 59.4 % under 450 nm visible light irradiation. Mechanistic studies demonstrate that the oxygen-mediated, sequential single-electron transfer process can occur with virtually zero activation energy.