Key Role of Valence Band Position in Porous Carbon Nitride for Photocatalytic Water Splitting
Decong Xie, Yutong Li, Haonan Dong, Weijun Jing, Yongxing Liu, Fayu Wu, Junwei Zhang, Zheng Zhang
Abstract
The microstructure, electrical energy band, and photocatalytic properties of carbon nitride were regulated and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), and UV–vis methods. Using oxygen-containing functionalization, equivalent overpotentials for oxygen and hydrogen production were realized in porous and amorphous carbon nitride with a constant narrow band gap. As the valence band position in such carbon nitride changes only from +1.51 to +1.67 eV with the increase in oxygen-containing functional groups, the oxygen production increased from 5.5 to 9.3 μmol with 3 h of irradiation, and the hydrogen production increased from 75.4 to 143.9 μmol in spite of the negative effect caused by the concurrent drop in the conduction band. The valence band position plays a very critical role in combining oxidation with the reduction half-reaction of photocatalysis.