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.

Keywords

• Non-precious-metal cocatalysts
• Photocatalytic hydrogen evolution reaction
• CoS2 cocatalysts
• 2D-layered g-C3N4