Recent advances in the design, preparation, and applications of different catalysts for electrochemical and photochemical H ₂ O ₂ production are summarized, and some invigorating perspectives for future developments are also provided.

Introducing nitrogen vacancies is an effective method to improve the catalytic performance of g‐C₃N₄‐based photocatalysts, whereas understanding how nitrogen vacancies types affect the catalytic performance remains unclear. Herein, two different types of nitrogen vacancies were successfully introduced into g‐C₃N₄ by pyrolysis of melamine under argon and ammonia atmosphere with subsequent HNO₃ oxidation. The pyrolysis atmosphere is found to have a significant influence on the introduced nitrogen vacancies type, where tertiary nitrogen groups (N₃C) and sp²‐hybridized nitrogen atoms (N₂C) were the preferred sites for the formation of nitrogen vacancies under ammonia and argon pyrolysis, respectively. Moreover, nitrogen vacancies from N₃C are experimentally and theoretically demonstrated to facilitate the narrowed band gap and the improved oxygen absorption capability. As expected, the optimal catalyst exhibits high H₂O₂ yield of 451.8 µM, which is 3.8 times higher than the pristine g‐C₃N₄ (119.0 µM) after 4 h and good stability after10 photocatalytic runs.