Construction of oxygen-enriched graphitic carbon nitride polymers for highly efficient and selective H₂O₂ production via photocatalytic O₂ reduction.

Oxygen defects play an important role in many catalytic reactions. Increasing surface oxygen defects can be done through reduction treatment. However, excessive reduction blocks electron channels and deactivates the catalyst surface due to electron-trapped effects by subsurface oxygen defects. How to effectively extract electrons from subsurface oxygen defects which cannot directly interact with reactants is challenging and remains elusive. Here, we report a metallic In-embedded In₂O₃ nanoflake catalyst over which the turnover frequency of CO₂ reduction into CO increases by a factor of 866 (7615 h⁻¹) and 376 (2990 h⁻¹) at the same light intensity and reaction temperature, respectively, compared to In₂O₃. Under electron-delocalization effect of O-In-(O)V_o-In-In structural units at the interface, the electrons in the subsurface oxygen defects are extracted and gather at surface active sites. This improves the electronic coupling with CO₂ and stabilizes intermediate. The study opens up new insights for exquisite electronic manipulation of oxygen defects.