Targeted Modulation of Competitive Active Sites toward Nitrogen Fixation via Sulfur Vacancy Engineering Over MoS2

Abstract Electrocatalytic nitrogen reduction reaction (NRR) offers an environmentally benign and sustainable alternative for NH 3 synthesis. However, developing NRR electrocatalysts with both high activity and selectivity remains a significant challenge. Guided by the density functional theory (DFT) calculations and further verified by the experiment, a modulated MoS 2 with well‐controlled S vacancies (MoS 2 ‐Vs) is prepared as an excellent electrocatalyst for NRR, where both the activity and selectivity of NRR mightily rely on the S‐vacancy concentration. The optimized catalyst (MoS 2 ‐7H) in a suitable S‐vacancy concentration (17.5%) is empowered with an excellent NRR activity (NH 3 yield rate: 66.74 µg h − 1 mg − 1 at −0.6 V) and selectivity (Faradic efficiency (FE): 14.68% at −0.5 V). Further mechanistic study reveals that the NRR performance is powerfully concentration‐dependent since its activity is enhanced due to the S‐vacancy‐strengthened N 2 adsorption and reduced reaction energy barrier. Simultaneously, its selectivity is synchronously improved by the steadily enhanced NRR activity and inversely suppressed hydrogen evolution reaction through limiting H 2 desorption kinetics, which sets it markedly apart from other reported defective MoS 2 ‐based catalysts.