Targeted Modulation of Competitive Active Sites toward Nitrogen Fixation via Sulfur Vacancy Engineering Over MoS_2

摘要

Electrocatalytic nitrogen reduction reaction (NRR) offers an environmentallybenign and sustainable alternative for NH_3 synthesis. However, developingNRR electrocatalysts with both high activity and selectivity remains asignificant challenge. Guided by the density functional theory (DFT)calculations and further verified by the experiment, a modulated MoS_2 withwell-controlled S vacancies (MoS_2-Vs) is prepared as an excellentelectrocatalyst for NRR, where both the activity and selectivity of NRR mightilyrely on the S-vacancy concentration. The optimized catalyst (MoS_2-7H) in asuitable S-vacancy concentration (17.5) is empowered with an excellent NRRactivity (NH_3 yield rate: 66.74 μg h~(?1) mg~(?1) at ?0.6 V) and selectivity (Faradicefficiency (FE): 14.68 at ?0.5 V). Further mechanistic study reveals that theNRR performance is powerfully concentration-dependent since its activity isenhanced due to the S-vacancy-strengthened N_2 adsorption and reducedreaction energy barrier. Simultaneously, its selectivity is synchronouslyimproved by the steadily enhanced NRR activity and inversely suppressedhydrogen evolution reaction through limiting H_2 desorption kinetics, whichsets it markedly apart from other reported defective MoS_2-based catalysts.