g-C3N4 is a visible-light photocatalyst with a suitable band gap and good stability. Moreover, g-C3N4 is considered to be earth-abundant, which makes it an appealing photocatalyst. However, due to its small specific surface area, low utilization of visible light, and high photogenerated electron-hole pair recombination rate, the photocatalytic activity of g-C3N4 remains unsatisfactory. In this work, a highly efficient nonmetallic photocatalyst, i.e., g-C3N4 doped with uracil (denoted U-C3N4) was successfully developed. Based on the various characterizations and calculations, it is shown that the triazine group in g-C3N4 is replaced with the diazine group in uracil. This occurrence leads to the formation of a new electron-transfer pathway between triazine groups, which can promote the separation of photogenerated electrons and holes. Concurrently, due to the ultrathin structure of the as-prepared U-C3N4, the material possessed a larger specific surface area than pristine g-C3N4, which can provide more active sites. Furthermore, the transfer pathway between the electron and hole was also shortened, and the recombination of the electron and hole was inhibited. According to the results, an optimal hydrogen evolution rate of 31.7 mol h-1 g-1 was achieved by U-C3N4, which is 5.1 times higher as compared to that achieved by pristine g-C3N4 (6.26 mol h-1 g-1). For the photocatalytic degradation of rhodamine B, the reaction rate constant of U-C3N4 (11.3 × 10-2 min-1) is about 5.5 times that of g-C3N4 (2.07 × 10-2 min-1). Furthermore, the uracil-doped catalyst was also able to demonstrate good stability after five successive runs.
Keywords: g-C3N4; molecule doping; photocatalytic degradation; photocatalytic hydrogen evolution; uracil.