Covalent 0D–2D Heterostructuring of Co9S8–MoS2 for Enhanced Hydrogen Evolution in All pH Electrolytes

• Published in: Advanced functional materials 2020-10, Vol.30 (40), p.n/a
• Main Authors: Kim, Minkyung, Anjum, Mohsin Ali Raza, Choi, Min, Jeong, Hu Young, Choi, Sun Hee, Park, Noejung, Lee, Jae Sung
• Format: Article
• Language: English
• Subjects: Basal plane; Cobalt sulfide; Covalence; covalent 0D/2D heterostructure; Covalent bonds; Defect annealing; Density functional theory; Electrocatalysts; Electrolytes; Heterostructures; hydrogen evolution reaction; Hydrogen evolution reactions; Materials science; Metal foams; Molybdenum disulfide; molybdenum sulfide; Nanoparticles; Noble metals; nonprecious metal electrocatalysts; Platinum; Stability; Synergistic effect; Water splitting
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202002536

Ultrasmall Co9S8 nanoparticles are introduced on the basal plane of MoS2 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 Co9S8 and MoS2 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 MoS2 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–MoS2 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–MoS2 heterostructure make it a promising pH universal alternative to expensive Pt‐based electrocatalysts for practical water electrolyzers. Co9S8 nanoparticles grow on the MoS2 sheet via covalent bonds of the Co–S–Mo type. The charge redistribution at the interface makes the Mo sites electron‐rich and abundant S defects on MoS2 activate the inert basal plane. The strong connection and interaction with S defects of 0D–2D heterostructure eventually lead to amplified hydrogen evolution reaction activity as well as stability in all pH electrolytes.