Edge-Site Nanoengineering of WS2 by Low-Temperature Plasma-Enhanced Atomic Layer Deposition for Electrocatalytic Hydrogen Evolution.

Abstract

Edge-enriched transition metal dichalcogenides, such as WS2, are promising electrocatalysts for sustainable production of H2 through the electrochemical hydrogen evolution reaction (HER). The reliable and controlled growth of such edge-enriched electrocatalysts at low temperatures has, however, remained elusive. In this work, we demonstrate how plasma-enhanced atomic layer deposition (PEALD) can be used as a new approach to nanoengineer and enhance the HER performance of WS2 by maximizing the density of reactive edge sites at a low temperature of 300 °C. By altering the plasma gas composition from H2S to H2 + H2S during PEALD, we could precisely control the morphology and composition and, consequently, the edge-site density as well as chemistry in our WS2 films. The precise control over edge-site density was verified by evaluating the number of exposed edge sites using electrochemical copper underpotential depositions. Subsequently, we demonstrate the HER performance of the edge-enriched WS2 electrocatalyst, and a clear correlation among plasma conditions, edge-site density, and the HER performance is obtained. Additionally, using density functional theory calculations we provide insights and explain how the addition of H2 to the H2S plasma impacts the PEALD growth behavior and, consequently, the material properties, when compared to only H2S plasma.