Electrochemical generation of sulfur vacancies in the basal plane of MoS2 for hydrogen evolution

Charlie Tsai,Frank Abild-Pedersen,Xiaolin Zheng,Sangwook Park,Joonsuk Park,Hong Li,Jens K Nørskov,Hyun Soo Han

doi:10.1038/ncomms15113

Abstract

Recently, sulfur (S)-vacancies created on the basal plane of 2H-molybdenum disulfide (MoS2) using argon plasma exposure exhibited higher intrinsic activity for the electrochemical hydrogen evolution reaction than the edge sites and metallic 1T-phase of MoS2 catalysts. However, a more industrially viable alternative to the argon plasma desulfurization process is needed. In this work, we introduce a scalable route towards generating S-vacancies on the MoS2 basal plane using electrochemical desulfurization. Even though sulfur atoms on the basal plane are known to be stable and inert, we find that they can be electrochemically reduced under accessible applied potentials. This can be done on various 2H-MoS2 nanostructures. By changing the applied desulfurization potential, the extent of desulfurization and the resulting activity can be varied. The resulting active sites are stable under extended desulfurization durations and show consistent HER activity.

Highlights

Sulfur (S)-vacancies created on the basal plane of 2H-molybdenum disulfide (MoS2) using argon plasma exposure exhibited higher intrinsic activity for the electrochemical hydrogen evolution reaction than the edge sites and metallic 1T-phase of MoS2 catalysts
We demonstrated that active sites could be directly created on the basal plane of common 2H-MoS2 materials by generating sulfur (S)-vacancies, whose intrinsic activity can be optimized by fine tuning the S-vacancy concentration and introducing elastic tensile strain[9]
Using density functional theory (DFT) calculations, we investigated the conditions where S-vacancies in the 2H-MoS2 basal planes become thermodynamically favoured in an EC environment

Summary

Introduction

Sulfur (S)-vacancies created on the basal plane of 2H-molybdenum disulfide (MoS2) using argon plasma exposure exhibited higher intrinsic activity for the electrochemical hydrogen evolution reaction than the edge sites and metallic 1T-phase of MoS2 catalysts. The concentration of S-vacancies can be varied by changing the applied desulfurization voltage These predictions are experimentally verified on a well-defined model system of continuous MoS2 monolayers supported on gold (Au) (the same system considered previously9), showing that electrochemically generated S-vacancies are comparable to Ar plasma generated ones. Using MoS2 supported on carbon foam, we show that the HER activity is stable under extended desulfurization durations as well as operating durations and that the concentration of S-vacancies and activity can be varied using the applied potential

Methods

Results

Conclusion