Combined computational and experimental approaches were used to evaluate defective 2H-MoS₂ nanosheets for their activity and selectivity for hydrogen evolution reaction (HER) and nitrogen reduction reaction (NRR). Density functional theory calculations were used to understand the relationship between HER and NRR activity on the ideal basal MoS₂ plane, seven grain-boundaries, ten single-/few-atom vacancies and anti-sites, and zigzag and armchair edge sites. The results confirm that 2H-MoS₂ should contain several defects with high activity for HER: armchair and zigzag edges, V_S vacancy, Mo_S2 anti-site, and S-S and Mo-Mo grain boundaries. Considering Gibbs free energy change for all the steps in the NRR mechanism and kinetic barriers for a key NRR step, we have found that activation of perspective NRR selective sites in 2H-MoS₂, namely V_MoS6 and clusters of S-vacancies, would require large overpotential, conditions at which HER dominates. The DFT conclusions are supported by the electrochemical studies of NRR activity and selectivity under aqueous conditions, which show an increase in NRR activity but a decrease in Faradaic efficiency as applied cell potential becomes more negative. The results of this work therefore highlight the challenges in activating natural 2H-MoS₂ for NRR, which would require additional material engineering or reaction condition optimization as a way to suppress HER, decrease the NRR overpotential or preferentially both.

结合计算和实验方法来评估有缺陷的2H-MoS ₂纳米片的活性和对析氢反应（HER）和氮还原反应（NRR）的选择性。使用密度泛函理论计算来了解HER和NRR活性在理想的基础MoS ₂平面，七个晶界，十个单原子/很少原子的空位和反位点以及之字形和扶手椅状边缘位点之间的关系。结果证实2H-MoS ₂应该包含一些对HER具有高活性的缺陷：扶手椅和锯齿形边缘，V _S空位，Mo _S2反位点，以及SS和Mo-Mo晶界。考虑到NRR机制中所有步骤的吉布斯自由能变化和关键NRR步骤的动力学障碍，我们发现激活2H-MoS _2中的透视NRR选择位点（即V _MoS6和S空位簇）将需要HER占主导地位的巨大超电势条件。DFT结论得到了在水性条件下NRR活性和选择性的电化学研究的支持，这些研究表明NRR活性增加，但法拉第效率降低，因为施加的电势变得更负。因此，这项工作的结果突显了激活天然2H-MoS ₂的挑战 对于NRR，这将需要额外的材料工程或反应条件优化，以抑制HER，从而降低NRR的超电势或优先考虑两者。