Rationalizing notable hole scavenger effects in g-C3N4-catalyzed H2O2 photosynthesis

Hydrogen peroxide (H 2 O 2 ) is a versatile and environmentally friendly oxidant whose industrial production has potentially more sustainable routes. Photocatalyzed H 2 O 2 generation represents a mild and efficient alternative, utilizing solar energy to reduce oxygen. However, how the photooxidation half reactions of hole scavengers affect the overall catalytic performances is largely overlooked. Here, we report that photooxidation half reactions are the real rate-limiting steps and that the choice of hole scavengers vitally affects the overall production rate of H 2 O 2 . The H 2 O 2 formation kinetic constants for 12 hole scavengers are compared with their electrooxidation potentials, calculated orbital energies, and energy gaps. No general correlation is found. Several possibilities are proposed, including the influences of different surface adsorption and surface reaction pathways. Our finding suggests that in practice, it is difficult to choose the right half reaction based on intuition or experiences with other systems. A case-by-case study is needed.