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 Cu_2-xS/MoS₂ electrocatalysts via epitaxial growth of an ultra-thin MoS₂ layer on monodispersed Cu_2-xS quantum dots. The highest NH₃ yield of 22.1 µg h^-1 mg_cat.^-1 and Faraday efficiency of 6.06% were obtained at -0.5 V (versus reversible hydrogen electrode) on Cu_2-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 Cu_2-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.

电催化氮还原反应 (NRR) 被认为是一种高效、环保的 NH ₃生产替代方法。然而，选择性和催化活性之间的平衡仍然是开发高效电催化剂的最大挑战之一。在这里，我们提出了一种通过在单分散 Cu _2-x S 量子点上外延生长超薄 MoS ₂层来制备 Cu _2-x S/MoS ₂电催化剂的简单方法。最高 NH ₃产量为 22.1 µg h ^{- 1} mg _cat。^-1在具有超薄 MoS ₂壳（~1 nm）的Cu _2-x S/MoS ₂ -2.5% 上，在 -0.5 V（相对于可逆氢电极）下获得了 6.06% 的法拉第效率。但随着 Mo/Cu 比进一步增加到 5% 和 10%，由于析氢的竞争和随后法拉第效率的降低，它开始下降。进一步的机理研究表明，超薄MoS ₂壳对核/壳结构的精细调节可以提高氮吸附能力、电化学活性表面积和电荷转移率。提出了一种在 Cu _2-x S/MoS ₂核/壳催化剂上进行 NRR 的合理机制，其中可控的超薄 MoS ₂层可以有效地提高界面处的 NRR 性能，同时避免不必要的析氢增强。这项工作为通过合理的核/壳纳米结构工程设计 NRR 电催化剂提供了提高活性和选择性的范例。