Bimetal Networked Nanosheets Co x Ni 3−x S 2 as An Efficient Electrocatalyst for Hydrogen Evolution

For the first time, 3D networked Co x Ni 3−x S 2 nanosheets were facilely grown on Ni foam via two‐step hydrothermal method forming a composite electrode (Co x Ni 3−x S 2 /NF) for electrocatalytic hydrogen evolution reaction (HER) under alkaline condition. With x value being 1.4, the as‐prepared Co 1.4 Ni 1.6 S 2 /NF shows superior performance as a HER electrode with low overpotentials of 68 mV, 160 mV and 226 mV at current densities of 10, 50 and 100 mA cm −2 respectively and exhibits remarkable electrochemical durability for 50 h in 1.0 M KOH solution. We propose that the synergistic and electron‐coupling effect between Co and Ni atoms in the Co x Ni 3−x S 2 /NF networked nanosheets lead to abundant active sites on surface and optimizes electronic structure. Density functional theory calculations indicate the introduction of Co atom can reduce the adsorption of H* thus optimize the hydrogen adsorption free energy. The Co x Ni 3−x S 2 nanosheets not only break through the limitations of traditional Ni−Co−S materials at the ratio of Ni and Co : S as 3 : 4 but also improve the activity of hydrogen evolution. The 3D Co x Ni 3−x S 2 /NF nanomaterials become a promising alternative to the Pt‐based electrocatalysts for hydrogen evolution.