Construction of proton relay on carbon quantum dots for highly efficient hydrogen peroxide photo-production

The activity of photocatalytic oxygen reduction to produce hydrogen peroxide (H2O2) is still severely limited by its slow charge dynamics. Compared to previous work that focused on promoting electron-hole separation, this study emphasizes a strategy to optimize H2O2 photosynthesis by enhancing proton supply. The amino polycarboxylic acid (APCA) chelating agent was connected to the surface of a novel carbon-based photocatalyst, carbon quantum dots (CQDs), resulting in an increase in H2O2 production rate from 512 to 2200 mu mol g- 1h- 1. Impressively, the prepared CQDs can directly capture oxygen from the air, increasing the dissolved oxygen content in solution by 40 %. Air was used as a sustainable oxidant in energy conversion. Mechanism research found that the incorporation of APCA caused a negative shift in the conduction band position of CQDs, and the amide bonds formed on the catalyst acted as a proton relay. The accelerated proton transport promoted the separation and transfer of electrons, and enhanced the continuous single electron reduction of oxygen through proton coupled electron transfer reactions, with a selectivity of up to 94 % for H2O2 production. This study proposes a simple and excellent functional group mediated proton transfer enhancement method as a new choice for high-performance H2O2 green production.