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

Electrocatalytic nitrogen reduction reaction (NRR) offers an environmentally benign and sustainable alternative for NH₃ 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 MoS₂ with well-controlled S vacancies (MoS₂-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 (MoS₂-7H) in a suitable S-vacancy concentration (17.5%) is empowered with an excellent NRR activity (NH₃ 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 N₂ 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 H₂ desorption kinetics, which sets it markedly apart from other reported defective MoS₂-based catalysts. © 2023 Wiley-VCH GmbH.