P-doped melon-carbon nitride for efficient photocatalytic H₂O₂ production

Melon-based carbon nitride (CN) is a semiconductor photocatalyst with a conduction band position suitable for photocatalytic H₂O₂ production. However, the thermodynamic inability to adsorb O₂ molecules greatly limits its photocatalytic efficiency for H₂O₂ production. In this paper, P-doped CN with good performance for H₂O₂ production was synthesized by a simple one-step calcination method. The experimental results show that when the doping amount of P is about 9.0 wt% of CN, the yield of H₂O₂ can reach 12990 μM/h/g, which is about 6.6 times as that of pure CN. The mechanism of H₂O₂ production over P-CN was firstly revealed by using the density functional theory calculations based on the melon crystal structure of carbon nitride. The results show that P-doping is easier to the strong thermodynamic adsorption of O₂ on CN, which is more beneficial to the formation of intermediate products. Further experimental results show that the substitution of C in CN by P-doping suppresses the electron and hole recombination, and therefore promoting the photocatalytic performance of P-doped CN.