MoS₂ quantum dots as an efficient catalyst material for oxygen evolution reaction

The development of an active, earth-abundant and inexpensive catalyst for oxygen evolution reaction (OER) is highly desirable but remains a great challenge. Here, by combining experiments and first-principles calculations, we demonstrate that MoS₂ quantum dots (MSQDs) are an efficient material for OER. We use a simple route for the synthesis of MSQDs from a single precursor in aqueous medium avoiding the formation of unwanted carbon quantum dots (CQDs). The as-synthesized MSQDs exhibit higher OER activity with the lower Tafel slope as compared to that for the state-of-the-art catalyst IrO₂/C. The potential cycling of the MSQDs activates the surface and improves the OER catalytic properties. The density functional theory calculations reveal that MSQD vertices are reactive and the vacancies at the edges also promote the reaction, which indicates that the small flakes with defects at the edges are efficient for OER. The presence of CQDs affects the adsorption of reaction intermediates and dramatically suppresses the OER performance of the MSQDs. Our theoretical and experimental findings provide important insights into the synthesis process of MSQDs and their catalytic properties and suggest promising routes to tailoring the performance of the catalysts for OER applications.