Direct Attack and Indirect Transfer Mechanisms Dominated by Reactive Oxygen Species for Photocatalytic H2O2 Production on g-C3N4 Possessing Nitrogen Vacancies

It is widely accepted that photogenerated holes are the only driving force for oxidizing an electron donor to form H+ during photocatalytic H2O2 production (PHP). Here, we use nitrogen deficiency carbon nitride as a model catalyst and propose several different reaction mechanisms of PHP based on the comprehensive analysis of experiment and simulation results. Nitrogen vacancies can serve as a center for oxidation, reduction, and charge recombination, promoting the generation of h+, •O2–, and 1O2, respectively, and thus induce H2O2 generation through five different pathways. In particular, the 1O2 anchored on the catalyst surface can realize the indirect oxidation of isopropanol with the assistance of surrounding water molecules and produce H2O2 with the lowest barrier. This work proves that H2O2 can be generated through multiple pathways and highlights the main roles of 1O2, which are ignored by previous studies.