Surface engineered carbon quantum dots for efficient photocatalytic hydrogen peroxide production

Photocatalytic production of hydrogen peroxide (H 2 O 2 ) from O 2 and water offers a sustainable and environmentally friendly approach to solar-to-chemical energy conversion. To address the low H 2 O 2 yield of pristine carbon quantum dots (CQDs) (354 µmol g −1 h −1 ), we applied molecular level engineering of CQDs through surface NH functionalization (CQDs-NH), which significantly increased photocatalytic activity of H 2 O 2 production to 2974 µmol g −1 h −1 . This enhanced performance is attributed to the C N-NH- group in CQDs-NH, which improves light absorption, facilitates carrier separation and transfer, increases the selectivity of two-electron oxygen reduction reaction, and promotes oxygen adsorption. Additionally, the hydrogen atom in the C N-NH- group acts as a proton conductor, which significantly promoted the proton-coupled electron transfer process to produce H 2 O 2 in the presence of O 2 . Moreover, a high H 2 O 2 production capacity of 2764 µmol g −1 h −1 was obtained even in the absence of an electron donor. • CQDs as effective photocatalysts for H 2 O 2 production. • NH-functionalized CQDs boost photocatalytic performance. • C N-NH- group aids H 2 O 2 production via proton-coupled electron transfer. • Advanced analysis and DFT calculations provide insights in the mechanism.