Dyadic promotion of photocatalytic aerobic oxidation via the Mott–Schottky effect enabled by nitrogen-doped carbon from imidazolium-based ionic polymers

Abstract

Metal/semiconductor systems are one type of promising heterogeneous photocatalyst for solar conversion. The injection of hot electrons from photoactivated metals to semiconductors is the rate-determining step owing to the Schottky barrier created at the interface. It is highly desirable to develop new approaches for promoting hot electron transfer. Herein, we present one type of new Mott–Schottky-type photocatalytic material consisting of TiO₂ nanosheets and Ru nanoparticles (NPs) coated with nitrogen-doped carbon (TiO₂@NC-Ru-T). They are readily available through the conformal coating of TiO₂ with a main-chain imidazolium-based ionic polymer (ImIP), followed by anion exchange with perruthenate and subsequent pyrolysis; the sintering of Ru NPs is effectively inhibited by ImIP, generating small-sized and well-dispersed Ru NPs. The nitrogen-doped carbon in TiO₂@NC-Ru-T both strengthens the performance of Ru NPs and facilitates photoelectron transfer from photoactivated Ru NPs to TiO₂ through a Mott–Schottky contact. The dyadic effects greatly promote selective aerobic oxidation of alcohols with air as an oxidant under visible light irradiation. This work provides a feasible protocol for improving visible light absorption and charge/electron transfer in photocatalytic reactions, and holds great promise for developing a new type of solar-to-chemical energy conversion reaction.