Efficient anoxic pollutant removal with oxygen functionalized graphitic carbon nitride under visible light

Photocatalytic oxidation of organic pollutants is often carried out oxically because molecular oxygen plays important roles like capturing photogenerated electrons to habilitate electron-hole pair recombination and produce reactive oxygen species during photocatalysis. It would be very attractive to extend the application of photocatalytic oxidation technology to the anoxic removal of organic pollutants existing in some oxygen-free spaces, but still a challenge. In this study, we demonstrate that oxygen functionalization endows g-C3N4 with anoxic photocatalytic organic pollutant oxidation ability. The oxygen functionalization could increase the anoxic photocatalytic pollutant degradation and mineralization constants by about 18 and 7 times under visible light, respectively. After systematically investigating the relationship between oxygen functional groups and anoxic photo-oxidation properties of g-C3N4, we attribute the anoxic photocatalytic oxidation ability of g-C3N4 to the holes that remained after photogenerated electron trapping by oxygen functional groups for hydrogen evolution. The anoxic photo-oxidation activity of oxygen functionalized g-C3N4 did not significantly decrease after four cycles, suggesting its high stability. This study provides some new insight into the correlation between oxygen functionalization and semiconductor photocatalysis as well as the design and fabrication of anoxic photocatalysts.