Synergistic O2 Activation and H2O Dissociation Triggered by Spatially Proximal Frustrated Lewis Pairs on Hydroxylated Indium Oxide for Boosted Photocatalytic H2O2 Generation

Efficient activation of O2 and H2O at active sites is the core prerequisite for high-performance photocatalytic H2O2 generation, yet current photocatalytic systems are severely restricted by spatially separated sites-induced blocked proton transfer/intermediate coupling and competitive substrate activation among different active sites. Herein, frustrated Lewis pairs (FLPs) are rationally engineered on the hydroxylated indium oxide (In2O3-x(OH)y) surface, where spatially proximal Lewis acid (LA) and Lewis base (LB) sites are integrated to realize synergistic photocatalysis. The electron-deficient LA sites efficiently adsorb and activate O2 through a Pauling-type adsorption configuration. The proximal LA/LB sites cooperatively facilitate H2O adsorption and O-H bond cleavage. Following H2O dissociation, the resulting surface In-OH species can participate in a water-assisted proton exchange process, providing a plausible pathway for proton transfer to oxygen-derived intermediates. Through the spatially coordinated activation of O2 and H2O, the proximal LA/LB sites facilitate interfacial proton transfer and promote the coupling of O2 reduction intermediates with protonic species, thereby enhancing H2O2 formation. Benefiting from the aforementioned dual-site synergistic effect, the optimized In2O3-x(OH)y catalyst exhibits a photocatalytic H2O2 production rate in pure water that is nearly three-fold higher than those of control samples with sole LA or LB active sites. This work successfully extends the spatial synergistic mechanism of FLPs toward efficient photocatalytic H2O2 synthesis, which provides a feasible strategy and insights for the rational design of high-performance bifunctional photocatalysts.