Ultra-thin shelled Cu2-xS/MoS2 quantum dots for enhanced electrocatalytic nitrogen reduction

Abstract

Electrocatalytic nitrogen reduction reaction (NRR) has been considered as an efficient and environment-friendly alternative method for NH3 production. However, the balance between selectivity and catalytic activity is still one of the biggest challenges for developing efficient electrocatalysts. Here, we propose a simple method for the preparation of Cu2-xS/MoS2 electrocatalysts via epitaxial growth of an ultra-thin MoS2 layer on monodispersed Cu2-xS quantum dots. The highest NH3 yield of 22.1 µg h-1 mgcat.-1 and Faraday efficiency of 6.06% were obtained at -0.5 V (versus reversible hydrogen electrode) on Cu2-xS/MoS2-2.5% with an ultrathin MoS2 shell (~1 nm). But it started to decrease with further Mo/Cu ratio increase to 5% and 10%, due to the competition of hydrogen evolution and subsequent reduction of the Faraday efficiency. Further mechanism studies demonstrate that the delicate core/shell structure regulation with an ultrathin MoS2 shell can enhance the nitrogen adsorption capacity, electrochemical active surface area, and charge transfer rate. A plausible mechanism was proposed for NRR on the Cu2-xS/MoS2 core/shell catalysts, where the controllable ultrathin MoS2 layer can effectively increase the NRR performance at the interface while avoiding the unwanted enhancement of hydrogen evolution. This work provides a paradigm for enhancing activity and selectivity through rational core/shell nanostructure engineering for the design of NRR electrocatalysts.