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.