The incorporation of cocatalyst cobalt sulfide into graphitic carbon nitride: Boosted photocatalytic hydrogen evolution performance and mechanism exploration

Abstract

2D-layered graphitic carbon nitride (g-C₃N₄) is regarded as a great prospect as a photocatalyst for H₂ generation. However, g-C₃N₄'s photocatalytic hydrogen evolution (HER) activity is significantly restricted by the recombination of photocarriers. We find that cobalt sulfide (CoS₂) as a cocatalyst can promote g-C₃N₄ nanosheets (NSs) to realize very efficient photocatalytic H₂ generation. The prepared CoS₂/g-C₃N₄ hybrids display highly boosted photocatalytic H₂ generation performance and outstanding cycle stability. The optimized 7%-CoS₂/g-C₃N₄ hybrids show a much improved photocatalytic H₂ generation rate of 36.2 ​μmol⁻¹ ​h⁻¹, which is about 180 times as much as bare g-C₃N₄ (0.2 ​μmol⁻¹ ​h⁻¹). In addition, the apparent quantum efficiency (AQE) of all the samples was computed under light at λ=370 ​nm, in which the AQE of 7%-CoS₂/g-C₃N₄ hybrids is up to 5.72%. The experimental data and the DFT calculation suggest that the CoS₂/g-C₃N₄ hybrid's excellent HER activity is attributable to the lower overpotential and the smaller Co-H bond activation energy for HER. Accordingly, the CoS₂ cocatalyst loading effectively boosts the photocatalytic performance of g-C₃N₄ for H₂ evolution. The project promotes fast development of high-efficiency photocatalysts and low-cost for photocatalytic H₂ generation.