S dopant-mediated hydrogen evolution reaction activity of CoSe₂

CoSe₂ has become one of the most appealing non-noble metal catalysts for hydrogen evolution reaction (HER) in the field of electrolysis water due to its abundant resources and good activity. Inversely, its slow kinetic behavior is still restrained, which plays a negative influence for high-efficiency HER. Herein, a certain of Ni or S was introduced into the (100) crystal facet of CoSe₂ on the basis of density functional theory (DFT) calculations. Thermodynamic calculation results reveal that the HER activity for CoSe₁S₁ is relatively better than those of Ni_0.375Co_0.625Se₂ and pristine CoSe₂ when a certain of S atoms were introduced into CoSe₂. More strikingly, the active sites of CoSe₁S₁ are reversed from cationic Co to anion S, which is close to the ideal value (0) of Gibbs free energy. Meanwhile, the kinetic performance of H adsorbed on the anionic S or Se site is optimal, and their migration energy barrier is lower in comparison with 1/2 of the cationic Co site. According to the electronic structure analysis, the conductivity of CoSe₁S₁ is prominent than other counterparts (such as Ni_0.375Co_0.625Se₂ and CoSe₂). This work indicates that CoSe₁S₁ exhibits an excellent catalytic performance for HER, and offers theoretical guidance in the aspect of experiments for designing high-efficient HER catalysts.