Se and O co-insertion induce the transition of MoS2 from 2H to 1T phase for designing high-active electrocatalyst of hydrogen evolution reaction

Abstract MoS2 is identified as a potential electrocatalyst for H2 evolution reaction (HER) due to its low cost and robust durability. However, the limited active site and low electrical conductivity severely hinder the practical application of MoS2. To address these issues, we herein propose a Se-insertion engineering strategy to fabricate Se- and O-co-inserted MoS2 (Se-MoS2) microspheres composed of intertwined nanosheets. Se and O co-insertion create abundant S defects on the basal plane of MoS2 and thus increase the number of active sites. Additionally, Se and O co-insertion are apt to induce the transition of MoS2 from 2H to 1T phase (~60% 1T MoS2), thereby exhibiting more excellent electric conductivity (~2 orders larger than that of MoS2). Furthermore, optimized Se-MoS2 not only shows electrocatalytic HER activity (an overpotential of 108 mV at 10 mA cm−2 and a Tafel slope of 47 mV dec–1), also inherits the outstanding electrocatalytic durability of pristine MoS2. Density function theory (DFT) calculations reveal that the excellent HER performance of optimized Se-MoS2 can be explained with Volmer-Heyrovsky mechanism, which is intrinsically attributed to the emergence of new band structures near the Fermi energy level of MoS2, increasing the electrical conductivity and reducing the Gibbs free energy of hydrogen adsorption.