Visible-light-driven H2O2 production from O2 reduction with nitrogen vacancy-rich and porous graphitic carbon nitride

Visible-light-driven H2O2 production from O-2 reduction is an eco-friendly strategy and attracts increasing attentions. In this study, KOH modified graphitic carbon nitrides (CNKx) were constructed through the thermolysis of melamine-cyanuric acid supramolecular-complex in the presence of KOH. The BET specific surface area of CNK0.2 with porous structure was 92 m(2) g(-1). The photocatalyst was characterized by XPS, ESR and element analysis and the analysis suggested that nitrogen vacancy was created in the framework of g-C3N4. Photoluminescence (PL) spectra indicated that the recombination of photogenerated electrons and holes was efficiently suppressed. zeta-potential revealed that more negative charge on the surface of CNK0.2, which promoted the adsorption of O-2 and accelerated the photocatalytic H2O2 production. ESR experimental and radical quenching results illustrated that superoxide radical (O-2-(center dot)) was the primary intermediate during the O-2 reduction process, suggesting the O-2 reduction pathway by CNK0.2 was the sequential two-step single-electron reduction.