Controllable selenium vacancy engineering in basal planes of mechanically exfoliated WSe₂monolayer nanosheets for efficient electrocatalytic hydrogen evolution

Abstract

Engineering intrinsic selenium vacancies (Se-vacancies) was achieved in mechanically exfoliated WSe monolayer nanosheets (WSe MLNSs) via an annealing treatment. Our theoretical and experimental results reveal that these Se-vacancies can efficiently activate and optimize the basal planes of the WSe MLNSs. As expected, the optimized catalyst exhibits efficient electrocatalytic hydrogen evolution.

Noble Metal‐Free Nanocatalysts with Vacancies for Electrochemical Water Splitting

“…The existence of vacancies would strikingly change the local chemical and electronic environment of the atoms in materials, which is reflected as obvious XAFS spectral change. The XAFS has been generically used to detect various vacancies including metal and nonmetal in the nanocatalysts . Zhang and co‐workers have synthesized an ultrathin δ‐MnO 2 nanosheets electrocatalyst (≈1.4 nm, denoted as NS‐MnO 2 ) with abundant oxygen vacancies for overall water splitting .…”

“…As a result, the HER performance of the a‐MoS 1.7 outperforms Pt catalyst at high current density (Figure c). Analogously, Cai and co‐workers have reported a controllable engineering of selenium vacancies in basal planes of mechanically exfoliated WSe 2 monolayer nanosheets for efficient electrocatalytic H 2 evolution . The selenium vacancies have been verified to act as highly active and tunable catalytic sites for HER.…”

“…c) TEM image of WSe 2 nanosheets. Reproduced with permission . Copyright 2016, Royal Society of Chemistry.…”

“…For the first route, the hydrogen that is adsorbed on the nanocatalyst can transfer electrons to the lattice atoms at high temperature, which could reduce the catalysts and lead to the formation of vacancies. Sun et al have introduced selenium vacancies into tungsten selenide (WSe 2 ) nanosheets (Figure c) via reductive annealing treatment in Ar/H 2 of 95:5 volume ratio atmosphere . It is shown that selenium vacancies increase with annealing temperature up to 900 °C while the degree of structural disorder remains admissible.…”

Earth‐Abundant Transition‐Metal‐Based Electrocatalysts for Water Electrolysis to Produce Renewable Hydrogen

“…[20] Other researchers have mentioned that thermodynamically stable defects existed in the metallic twin boundaries of slightly Mo-enriched MoTe 2 and some other chalcogenides, endowing the basal plane of the 2H phase with ah igh HER activity. [32] Yang and co-workers have synthesized am ix-phased W(Se x S 1Àx ) 2 nanoporous material, which exhibited catalytically active defects due to the lattice mismatch and disordering. Vertically oriented MoO 3 nanowires with ad iameterofabout 20-50 nm have been used as cores to support an MoS 2 shell about 2-5nmi nt hickness.…”