Efficient Exciton Dissociation in Ionically Interacted Methyl Viologen and Polymeric Carbon Nitride for Superior H2O2 Photoproduction

Restricted by the limited exciton diffusion and unproductive exciton recombination, the efficiency of photon-to-chemical conversion on polymeric carbon nitride (CN) photocatalyst is generally unsatisfactory. The rational design of an efficient polymeric photocatalyst is challenging due to the ambiguous understanding of the structure–property–photocatalytic activity relationship. The study herein demonstrates an unprecedently efficient photocatalyst for the photoproduction of hydrogen peroxide (H2O2), as well as the mechanistic rationale behind the remarkable catalytic performance. Anchoring cationic methyl viologen (MV) on the CN with an anionic moiety generates an ionic link and elicits an internal local electric field in the organic photocatalyst framework, which significantly enhances the exciton dissociation. Femtosecond transient absorption spectroscopy analysis demonstrates that the MV surface complex-induced internal local electric field favors the generation of long-lived trapped electron, especially under the high photon-flux irradiation of >450 mW cm–2. CN–MV thus exhibits superior photocatalytic performance in H2O2 production, for example, 114.2 mM H2O2 in a 53 min reaction in a continuous microbatch photoreactor. The apparent quantum yield reaches a high value of 51.1%. The present study highlights the significant impact of the surface complex on the electronic energy landscape of the photocatalyst toward enhanced exciton dissociation and hence improved photon-to-chemical conversion efficiency in various photocatalytic applications.