Dual-metal-doped high crystalline carbon nitride with cyano groups for enhanced photocatalytic hydrogen evolution

Abstract

The photocatalytic hydrogen (H₂) evolution by graphitic carbon nitride (g-C₃N₄) has been considered a perspective technique. However, the inferior photocatalytic activity was restricted by severe recombination of photogenerated carriers. Hence, doping bimetallic and cyano group-modified high crystalline carbon nitride to tune its band gap is an essential strategy for improving its photocatalytic activity. The hydrogen evolution rate of Zn–K–CN is 31.2 μmol, which is significantly higher than that of pure g-C₃N₄. Its apparent quantum efficiency (AQE) was up to 2.9% at 420 nm. Significantly, the photocatalytic performance can remain stable for 12 h for four consecutive cycles. This remarkable performance can be attributed to the enlarged surface area, which provides a greater number of reactive sites, the narrow bandgap that enhances the absorption of visible light, and the negatively positioned conduction band edge, which facilitates hydrogen reduction.