Single-Layer Cu₂WS₄ with Promising Electrocatalytic Activity toward Hydrogen Evolution Reaction

Abstract

Two-dimensional hydrogen evolution reaction (HER) electrocatalysts\nare outstanding alternatives to high-cost Pt due to their good material\nproperties. However, the few existing two-dimensional HER electrocatalysts\nhave shortcomings that restrict their performance. Here, we report\na first-principles study of single-layer A₂BS₄ (A = Ag, Cu; B= Mo, W) as HER electrocatalysts and identify single-layer\nCu₂WS₄ as a promising candidate. Single-layer\nA₂BS₄ is found to be chemically, dynamically,\nand thermally stable. They require only a small energetic cost to\nbe created from their layered bulks, suggesting the possibility of\ntheir exfoliation in experiments. Most importantly, without significant\ndensity of vacancies and in the absence of large applied strain, the\nbasal plane of single-layer Cu₂WS₄ shows excellent\nelectrocatalytic activity toward HER. Such an activity is attributed\nto the introduced in-gap states and d band center shifting upon adsorbing\nhydrogen. These characteristics suggest that single-layer Cu₂WS₄ is an extraordinary two-dimensional HER electrocatalyst.