Reduced Oxygenated g-C3N4 with Abundant Nitrogen Vacancies for Visible-Light Photocatalytic Applications

A novel g-C3N4 photocatalyst (RCNO) with abundant nitrogen vacancies and oxygen-containing electron-withdrawing groups was prepared. Oxygen was gradually introduced into the g-C3N4 structure by a hydrothermal hydrolysis/condensation process, and nitrogen vacancies were produced with H-2 reduction. The presence of nitrogen vacancies reduced the conduction band energy of g-C3N4 from -0.75 to -0.5eV and introduced plenty of defect levels in the band gap (just below the conductive band with a width of 0.45eV). The oxygenation of g-C3N4 induced the formation of oxygen-containing functional groups, such as C=O and C-O, as well as effectively enhancing the separation efficiency of photogenerated carriers and reducing the valence band energy from 2.05 to 2.30eV. Therefore, the photocatalytic activity and photocurrent responses of RCNO were about nine and eight times higher than that of g-C3N4, respectively.