Atomic-scale vacancy engineering unlocks basal-plane catalytic activity in metallic WSe2 for reversible oxygen electrocatalysis

Abstract

Two-dimensional metallic transition metal dichalcogenides offer high electrical conductivity and large surface areas for electrocatalysis, yet their inherent basal planes are catalytically inert. Here, we present an atomic-scale vacancy engineering strategy to activate the basal surfaces of metallic WSe2 for reversible oxygen electrocatalysis. This approach, based on intentionally designed substitutional metal doping, promotes the spontaneous formation of selenium vacancies while preserving the metallic 1 T ' phase, thereby creating highly reactive and oxygen-affinitive sites. Density functional theory calculations reveal that these vacancy-mediated metal complexes dramatically lower the energy barriers for initial oxygen adsorption, enabling dissociative oxygen adsorption. Operando and ex-situ spectroscopic analyses confirm that vacancy-mediated metal complexes transform into dynamic Se/W-oxide intermediates under operating conditions. Se/W-oxides on the surface experimentally and theoretically prove electrocatalytic activity and reversibility. Applying this strategy in lithium-oxygen batteries, the basal-plane activated WSe2 shows high discharge capacities (9868 mA h g- 1, corresponding to 3947 mA h g- 1cathode), impressive cycle retention over 550 cycles at 1000 mA h g-1, and outstanding rate-capability over a wide current-density range (100-3000 mA g- 1) during 256 cycles.