Amorphous Bimetallic Cobalt Nickel Sulfide Cocatalysts for Significantly Boosting Photocatalytic Hydrogen Evolution Performance of Graphitic Carbon Nitride: Efficient Interfacial Charge Transfer

Noble metals usually work as the cocatalyst for photocatalytic water splitting, but their rare and expensive properties narrowed their wide development. Transition-metal sulfides have appeared to be promising non-noble metal cocatalysts in the hydrogen evolution reaction (HER) to meet future energy demands. Meanwhile, many studies focus on the fabrication of bimetallic catalysts because of their remarkably superior catalytic activity compared with monometallic substances. Herein, amorphous bimetallic cobalt nickel sulfide (CoNiSx) was fabricated to work as a cocatalyst in the photocatalytic H2 evolution reaction, which can couple with pristine graphitic carbon nitride (g-C3N4). CoNiSx-CN exhibits a larger specific surface area compared with g-C3N4, making it possess more reaction active sites. Moreover, the contacted interface in the CoNiSx-CN composite photocatalyst contributes to higher separation efficiency of photogenerated carriers, which was proved by experimental and theoretical calculations. More importantly, the theoretical calculation also verified that CoNiSx-CN has relatively closer Gibbs free energy to zero than pure g-C3N4 and corresponding monometallic cocatalyzed g-C3N4. Therefore, the prepared CoNiSx-CN composite exhibited a dramatic photocatalytic HER performance of 2.366 μmol mg-1 h-1, which is about 76-fold higher in comparison with pristine g-C3N4 and comparable to g-C3N4 with Pt as a cocatalyst under 420 nm light irradiation. This study reveals a promising and efficient bimetallic cocatalyst for the photocatalytic H2 evolution reaction.