Janus effect of O2 plasma modification on the electrocatalytic hydrogen evolution reaction of MoS2

Abstract Oxygen incorporation is a promising and effective way for simultaneously engineering the edge and planar sites of MoS 2 to fabricate high-performance HER electrocatalysts. However, the insulating MoO 3 species are inevitably generated during the oxygen incorporation process. Here, controlled plasma exposure time has been designed to explore the influence of MoO 3 species on the HER performance for the O 2 plasma modified MoS 2 catalysts. We find that the MoO 3 species in MoS 2 are not conductive to the HER electrocatalysis. More importantly, the Raman spectrum, X-ray photoelectron spectroscopy, energy-disperse X-ray spectrum and transmission electron microscope analyses demonstrate that these co-generated MoO 3 species are reduced and resolved from the MoS 2 lattice during the electrocatalytic hydrogen evolution, leading to a holey structure in the MoS 2 nanosheets and thus a significant improvement of its hydrogen evolution stability. This work not only helps to understand the electrocatalytic influence of the co-generated MoO 3 species in MoS 2 , but also presents a methodological improvement in designing defect-rich, oxygen incorporated and holey MoS 2 nanosheets for highly efficient hydrogen evolution.