Carbon dots with different energy levels regulate the activity of metal-free catalyst for hydrogen peroxide photoproduction

Artificial photoproduction of hydrogen peroxide (H2O2) from H2O and O2 by metal-free catalysts (e.g., graphitic carbon nitride) is regarded as an ultra-clean approach. Metal-free catalysts are often hindered by unpropitious rapid charge recombination and unfavorable selectivity. Herein, three carbon dots (CDs1 to CDs3) decorated modified-carbon nitride (CDs1-NCN, CDs2-NCN and CDs3-NCN) were designed and fabricated, which show diverse activity of H2O2 photoproduction. Among them, CDs1-NCN, as a two-channel photocatalyst, achieves H2O2 production with high efficiency (1938 μmol h-1 g-1). This process is at normal pressure and without sacrificial agent under visible region (λ≥420nm), which is 27.5- times higher than that of pristine C3N4. The apparent quantum efficiency can be calculated to 7.03 % (λ=365nm). In this system, CDs with different energy levels dominate the activity of metal-free catalyst for hydrogen peroxide photoproduction. Combining with photoelectrochemical test and transient photovoltage analysis, the active site and the catalytic mechanism of these composite catalysts are also clarified. Our work provides a clearly insight for understanding of the regulation of interfacial electron transport in metal-free photocatalysts.