Heavily Doped Carbon Nitride Nanocrystal Promotes Visible-Near-Infrared Photosynthesis of Hydrogen Peroxide with Near-Unit Photon Utilization.

Direct photosynthesis of hydrogen peroxide (H 2 O 2 ) from water and oxygen represents an intriguing alternative to the current indirect process involving the reduction and oxidation of quinones. However, limited light utilization and sluggish charge transfer largely impede overall photocatalytic efficiency. Herein, we present a heavily doped carbon nitride (CN KLi ) nanocrystal for efficient and selective photoproduction of H 2 O 2 via a two-electron oxygen reduction reaction (ORR) pathway. CN KLi induces metal-to-ligand charge transfer (MLCT) and electron trapping, which broadens the light absorption to the visible-near-infrared (vis-NIR) spectrum and prolongs the photoelectron lifetime to the microsecond time scale with an exceptional charge diffusion length of ∼1200 nm. Near-unit photoutilization with an apparent quantum yield (AQY) of 100% for H 2 O 2 generation is achieved below 420 nm. Impressively, CN KLi exhibits an appreciable AQY of 16% at 700 nm, which reaches the absorption capacity (∼16%), thus suggesting a near-unit photon utilization <700 nm. In situ characterization and theoretical calculations reveal the facilitated charge transfer from K + to the heptazine ring skeleton. These findings provide an approach to improve the photosynthetic efficiency of direct H 2 O 2 preparation in the vis-NIR region and expand applications for driving kinetically slow and technologically desirable oxidations or high-value chemical generation.