Carbon vacancy regulated photoreduction of NO to N2 over ultrathin g-C3N4 nanosheets

Abstract

Photocatalytic oxidation has recently been recognized as an attractive technology for NO removal, in which the main products are NO2 or HNO3. However, these products may cause secondary pollution and deactivation of the involved photocatalysts. In this study, we demonstrate that carbon vacancy-modified nanosheet structure g-C3N4 (Ns-g-C3N4) can efficiently and selectively reduce NO to N2 under visible light. Since N2 is a green gas and can easily desorb from the active sites, the problems such as secondary pollution and catalyst deactivation are largely avoided. It was found that two structural characters of Ns-g-C3N4, ultrathin nanostructure and abundant surface defect sites, could promote its visible light absorption, and favor the separation and transfer of photogenerated charge carriers as well as strong chemisorption of NO, leading to high photoreactivity. Meanwhile, the surface defects of Ns-g-C3N4 shift the adsorption structure of NO from CNO for the bulk counterpart to CvON (adsorbed at the carbon vacancy site, Cv), eventually resulting in its high selectivity of converting NO to N2. The present study underlines the impetus of utilizing surface defect structure to regulate photocatalytic reaction pathway.