The Origin of High Activity of Amorphous MoS2 in the Hydrogen Evolution Reaction.

Longfei Wu,Ageeth A Bol,Nelson Y Dzade,Nora H De Leeuw,Jan P Hofmann,Alessandro Longo,Marco M R M Hendrix,Akhil Sharma,Emiel J M Hensen

doi:10.1002/cssc.201901811

Abstract

Molybdenum disulfide (MoS2) and related transition metal chalcogenides can replace expensive precious metal catalysts such as Pt for the hydrogen evolution reaction (HER). The relations between the nanoscale properties and HER activity of well‐controlled 2H and Li‐promoted 1T phases of MoS2, as well as an amorphous MoS2 phase, have been investigated and a detailed comparison is made on Mo−S and Mo−Mo bond analysis under operando HER conditions, which reveals a similar bond structure in 1T and amorphous MoS2 phases as a key feature in explaining their increased HER activity. Whereas the distinct bond structure in 1T phase MoS2 is caused by Li+ intercalation and disappears under harsh HER conditions, amorphous MoS2 maintains its intrinsic short Mo−Mo bond feature and, with that, its high HER activity. Quantum‐chemical calculations indicate similar electronic structures of small MoS2 clusters serving as models for amorphous MoS2 and the 1T phase MoS2, showing similar Gibbs free energies for hydrogen adsorption (ΔG H*) and metallic character.

Highlights

Molybdenum disulfide (MoS2) and related transition metal chalcogenides can replace expensive precious metal catalysts such as Pt for the hydrogen evolution reaction (HER)
Tremendous efforts have been devoted to engineering the surface structure of MoS2 to preferentially expose these edge sites to improve HER performance.[10]
Different polymorphs of MoS2 exist in the form of 2H, 1T, and 3R phases.[3,11] 2H-MoS2 is the thermodynamically stable two-dimensional (2D) phase with semiconductor properties,[12] a low electron mobility, and a limited number of HER-active sites

Summary

Introduction

Molybdenum disulfide (MoS2) and related transition metal chalcogenides can replace expensive precious metal catalysts such as Pt for the hydrogen evolution reaction (HER).

Results

Conclusion