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

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.