Conversion of Layered WS 2 Crystals into Mixed-Domain Electrochemical Catalysts by Plasma-Assisted Surface Reconstruction.

Electrocatalytic water splitting is crucial to generate clean hydrogen fuel, but implementation at an industrial scale remains limited due to dependence on expensive platinum (Pt)-based electrocatalysts. Here we report an all-dry process to transform electrochemically inert bulk WS 2 into a multidomain electrochemical catalyst that enables scalable and cost-effective implementation of the hydrogen evolution reaction (HER) in water electrolysis. Direct dry transfer of WS 2 flakes to a gold thin film deposited on a silicon substrate provides a general platform to produce the working electrodes for HER with tunable charge transfer resistance. By treating the mechanically-exfoliated WS 2 with sequential Ar-O 2 plasma, mixed domains of WS 2 , WO 3 , and tungsten oxysulfide form on the surfaces of flakes, which gives rise to a superior HER with much greater long-term stability and steady-state activity compared to Pt. Using density functional theory, we identified ultraefficient atomic sites formed on the constituent nanodomains, and the quantification of atomic scale reactivities and resulting HER activities fully support our experimental observations. This article is protected by copyright. All rights reserved.