Molybdenum and Sulfur Doping To Create Active Sites and Regulate d-Band Centers of Ni–Mo–S Electrocatalysts for the Hydrogen Evolution Reaction

Defining the active sites and further optimizing their activity are of great significance for enhancing the hydrogen evolution reaction (HER) performances, especially for inexpensive Ni-based catalysts doped with metals and nonmetal elements. This work reports the role of the incorporated molybdenum and sulfur in enhancing the HER activity of nickel. The prepared molybdenum and sulfur coincorporated Ni (NMS) electrocatalysts exhibit excellent HER performance, with an overpotential and Tafel slope of 77.0 mV (10 mA·cm^-2) and 64.4 mV·dec^-1, respectively, because of the large electrochemically active surface area, quick reaction kinetics, and charge-transfer capability. The theoretical calculation results reveal that the incorporated Mo atoms play the role of reaction sites, and the introduced S atoms can further enhance the activity of Mo atom. The high HER activity of the Mo atom can be attributed to the regulated d-band center by optimizing the composition of NMS, which tunes the interaction between Mo and intermediate species. The elucidated mechanism can make it possible to design Ni-based electrocatalysts doped with metals and nonmetals for efficient hydrogen evolution.