Covalent 0D-2D Heterostructuring of Co9S8-MoS2for Enhanced Hydrogen Evolution in All pH Electrolytes

Ultrasmall Co(9)S(8)nanoparticles are introduced on the basal plane of MoS(2)to fabricate a covalent 0D-2D heterostructure that enhances the hydrogen evolution reaction (HER) activity of electrochemical water splitting. In the heterostructure, separate phases of Co(9)S(8)and MoS(2)are formed, but they are connected by Co-S-Mo type covalent bonds. The charge redistribution from Co to Mo occurring at the interface enhances the electron-doped characteristics of MoS(2)to generate electron-rich Mo atoms. Besides, reductive annealing during the synthesis forms S defects that activates adjacent Mo atoms for further enhanced HER activity as elucidated by the density functional theory (DFT) calculation. Eventually, the covalent Co9S8-MoS(2)heterostructure shows amplified HER activity as well as stability in all pH electrolytes. The synergistic effect is pronounced when the heterostructure is coupled with a porous Ni foam (NF) support to form Co9S8-MoS2/NF that displays superior performance to those of the state-of-the-art non-noble metal electrocatalysts, and even outperforms a commercial Pt/C catalyst in a practically meaningful, high current density region in alkaline (>170 mA cm(-2)) and neutral (>60 mA cm(-2)) media. The high HER performance and stability of Co9S8-MoS(2)heterostructure make it a promising pH universal alternative to expensive Pt-based electrocatalysts for practical water electrolyzers.