Mo-doped SnS with enriched S-vacancies for highly efficient electrocatalytic N reduction: The critical role of the Mo-Sn-Sn trimer

Vacancy engineering and heteroatom doping are two effective approaches to tailor the electronic structures of catalysts for improved electrocatalytic activity. Herein, these two approaches were rationally combined to modulate the structure of SnS toward the N reduction reaction (NRR) by means of Mo-doping, which simultaneously induced the generation of enriched S-vacancies (V). The developed Mo-doped SnS nanosheets with enriched V presented a conspicuously enhanced NRR activity with an NH yield of 41.3 μg h mg (-0.5 V) and a faradaic efficiency of 20.8% (-0.4 V) and are among the best SnS-based NRR catalysts to date. Mechanistic studies revealed that the co-presence of the Mo dopant and V enabled the creation of Mo-Sn-Sn trimer catalytic sites, capable of strongly activating N even for the cleavage of the NN triple bond to the NN double bond at the N adsorption stage, consequently leading to a downhill process of the first hydrogenation step and a largely reduced energy barrier.