Revealing the Distinctive Roles of Nitrogen Vacancies in Generating H ₂ and H ₂ O ₂ in Carbon Nitride Photocatalysts

High Resolution Image Download MS PowerPoint Slide Graphitic carbon nitride (GCN) is extensively utilized for photocatalytic H 2 evolution reaction (HER) and H 2 O 2 production at scale. However, to overcome the performance bottlenecks, it is critical to establish the role of N-vacancies on the optical properties and the interfacial electron transfer process that are indispensable to generate both H 2 and H 2 O 2 . In this direction, rationally inducing N-vacancies significantly extends the optical absorption of GCN from 460 to 700 nm. Nevertheless, the HER performance was reduced by a factor of two, attributed to electron trapping by the N-vacancies in GCN. In contrast, H 2 O 2 production efficiency increases with N-vacancies. This intriguing observation is validated based on the lower thermodynamic driving energy required for a one-step O 2 reduction reaction to directly form H 2 O 2, compared to the reduction potential of H + ions to form H 2 . Control experiments with charge scavengers and photophysical and electronic structure analysis via theoretical calculations reveal that the N-vacancies promote O 2 adsorption that facilitates efficient electron transfer to form H 2 O 2 . Overall, a comprehensive correlation between the effect of N-vacancies on the electron transfer/trapping and their distinctive influence on photocatalytic HER and H 2 O 2 production in GCN is elucidated.