CoMo2S4 with Superior Conductivity for Electrocatalytic Hydrogen Evolution: Elucidating the Key Role of Co

Abstract CoMo 2 S 4 2D nanosheets are constructed by a hard template‐limited domain strategy, meanwhile the hydrogen evolution reaction (HER) properties and the function of Co in CoMo 2 S 4 are systematically investigated. Electrochemical tests show that CoMo 2 S 4 possesses high HER performance with an overpotential of 55 and 150 mV at 10 and 100 mA cm −2 , respectively, outperforming Pt/C (20%) and the state of art Mo–S, Co–S, and Co–Mo–S‐based materials. An in‐depth mechanism study reveals that the main active site of CoMo 2 S 4 is Mo rather than Co, whereas Co plays a key role in improving the electrical conductivity of the catalyst and thus improving the HER performance. X‐ray photoelectron spectroscopy and density of state tests demonstrate that the introduction of Co leads to electron delocalization in the catalyst, making the electrons transport easier and finally endowing the catalyst with better conductive performance. It is believed this is the first time that the effect of Co on improving the bulk conductivity of Co–Mo–S catalyst is proposed, which highlights the potency of Co in improving the electrocatalytic HER activity of Mo–S‐based materials.