Improved H-adsorption ability and conductivity of a Co-doped Mo2N cocatalyst for efficient photocatalytic H2 generation of g-C3N4

Cocatalysts are usually applied in the photocatalytic water splitting process to accelerate the kinetics of the hydrogen evolution reaction (HER). Specifically, the transition metal nitride (Mo2N) featuring a unique local surface plasmon resonance (LSPR) effect has exhibited great potential to function as a HER cocatalyst. However, the low metallicity of Mo2N hampers its ability to improve charge separation. To address this issue, transition metal atom doping (Co and Cu) engineering was used to modulate the electronic structure of Mo2N nanosheets to achieve a higher electrical conductivity and a lower hydrogen adsorption free energy (|Delta G(H*)|), thereby favoring the HER kinetics. Density functional theory (DFT) calculations and experimental results showed that Co-doping and Cu-doping mainly take place at Mo sites in the crystal structure of Mo2N to form stable structures of Co doped Mo2N (Co-Mo2N) and Cu doped Mo2N (Cu-Mo2N). Compared with pristine Mo2N, both Cu-Mo2N and Co-Mo2N demonstrated a much improved cocatalytic effect over g-C3N4 in promoting charge separation, accelerating HER kinetics and enhancing light absorption. The Co-Mo2N with the highest conductivity and lowest |Delta G(H*)| illustrated the best cocatalytic effect, and the H-2 production performance (367.8 mu mol g(-1) h(-1)) of Co-Mo2N/g-C3N4 achieved was 10 and 5 times higher than those of Mo2N/g-C3N4 and Cu-Mo2N/g-C3N4. This paper provides significant guidance in the design and development of efficient cocatalysts for the HER application.