Boosting the Electrocatalytic Dinitrogen ReductionReaction with Selenium Vacancy in Transition Metal Dichalcogenides

The electrochemical nitrogen reduction reaction (NRR) is emerging as a sustainable and carbon-free ammonia production approach under mild conditions, but it is highly dependent on the activity of the electrocatalyst material. Nevertheless, the availability of active sites on electrocatalysts for N₂ adsorption and activation limits the overall NRR performance. Herein, active site generation with defect engineering strategy is employed to explore selenium vacancy-rich transition metal dichalcogenides ex-MoSe₂ and ex-WSe₂ toward NRR. Thick-layered bulk MoSe₂ and WSe₂ are converted to selenium vacancy-rich few-layered nanosheets on chemical exfoliation. Highly promising electrocatalytic activity is witnessed for both materials. Typically, ex-MoSe₂ exhibited an NH₃ yield rate of 15.86 μg mg_cat^–1 h^–1 and a Faradaic efficiency of 9.39% at −0.9 V vs Ag/AgCl in 0.1 M Na₂SO₄ electrolyte of pH = 7. Moreover, validation of the true ammonia production with the elimination of probable contamination is done via feeding gas purification, control experiments, and isotope labeling experiments. Importantly, density functional theory calculations exhibit selenium vacancy as a favorable active site for N₂ adsorption and activation for efficient NRR and strongly support the experimental findings.