The interference mechanism of Na+ and Cl- on photocatalytic properties of phosphate-oxygen co-doped graphite carbon nitride for hydrogen production from water splitting: Experimental and theoretical calculations

Phosphorus-oxygen co-doped graphite carbon nitride (POx-CN) are successfully fabricated by in situ impregnation and two-stage thermal polycondensation to investigate the effect of Na + and Cl - on the photocatalytic hydrogen evolution from artificial seawater splitting. The as-prepared POx-CN exhibits a hydrogen evolution rate of 1054.29 μmolg −1 h −1 in artificial seawater , lower than fresh water , indicating that Na + and Cl - play an inhibitory effect on hydrogen evolution reaction . The theoretical calculation indicates that the phosphorus-oxygen binary doping changed the electrostatic potential of the modified layer in carbon nitride molecule, accelerating the electron transfer rate from the structural O in triazine ring to P-N bond. In artificial seawater, the competition between Na + and Pt 2+ at active sites in the modified layer and electron capture by Cl - in the mutual conversion of Cl - and chlorine radicals result in the reduction of hydrogen evolution efficiency.