Surface oxygenous groups modified graphitic carbon nitride with significant positive shift of valence band for efficient photocatalytic oxidation

Abstract

Graphitic carbon nitride (g-C3N4) is a remarkable metal-free photocatalyst which is widely used for photocatalytic reductive reaction due to its suitable potential of conduction band, but also suffers from intrinsically weak photocatalytic oxidation ability. Here, by simply refluxing g-C3N4 in H2O2, oxygenous groups are introduced into g-C3N4. The resultant oxygenous groups modified g-C3N4 (g-C3N4(H2O2)) exhibits significantly improved hydrophilic ability and photocatalytic oxidative ability. It is well evidenced that valence band position is positive shifted significantly by introduction of surface oxygenous groups. However, the photocatalytic activity for oxygen evolution is not improved obviously, suggesting that the driving force for water oxidation is not increased simultaneously. Luckily, the photocatalytic oxidative activity of the modified g-C3N4 (include oxygen evolution, pollutant degradation and antibacterial property) could be further improved after forming TiO2-containing nanocomposites during the H2O2 reflux treatment with the addition of tertrabutyl titanate (g-C3N4/TiO2(H2O2) due to much increased driving force and accelerated charge migration. Herein, a facile and simple method is proposed to engineer the band structure of g-C3N4 for improving its photocatalytic oxidative ability, which expand the application of carbon nitride.