The excellent catalytic activity of metallic MoS₂ edges for the hydrogen evolution reaction (HER) has led to substantial efforts towards increasing the edge concentration. The 2H basal plane is less active for the HER because it is less conducting and therefore possesses less efficient charge transfer kinetics. Here we show that the activity of the 2H basal planes of monolayer MoS₂ nanosheets can be made comparable to state-of-the-art catalytic properties of metallic edges and the 1T phase by improving the electrical coupling between the substrate and the catalyst so that electron injection from the electrode and transport to the catalyst active site is facilitated. Phase-engineered low-resistance contacts on monolayer 2H-phase MoS₂ basal plane lead to higher efficiency of charge injection in the nanosheets so that its intrinsic activity towards the HER can be measured. We demonstrate that onset potentials and Tafel slopes of ~−0.1 V and ~50 mV per decade can be achieved from 2H-phase catalysts where only the basal plane is exposed. We show that efficient charge injection and the presence of naturally occurring sulfur vacancies are responsible for the observed increase in catalytic activity of the 2H basal plane. Our results provide new insights into the role of contact resistance and charge transport on the performance of two-dimensional MoS₂ nanosheet catalysts for the HER.

Nature Materials (2016) doi:10.1038/nmat4660
Received 21 January 2016 Accepted 03 May 2016 Published online 13 June 2016

http://www.nature.com/nmat/journal/vaop/ncurrent/full/nmat4660.html