Mo-doped SnS2 with enriched S-vacancies for highly efficient electrocatalytic N2 reduction: the critical role of the Mo–Sn–Sn trimer

Abstract

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 SnS₂ toward the N₂ reduction reaction (NRR) by means of Mo-doping, which simultaneously induced the generation of enriched S-vacancies (V_s). The developed Mo-doped SnS₂ nanosheets with enriched V_s presented a conspicuously enhanced NRR activity with an NH₃ yield of 41.3 μg h⁻¹ mg⁻¹ (−0.5 V) and a faradaic efficiency of 20.8% (−0.4 V) and are among the best SnS₂-based NRR catalysts to date. Mechanistic studies revealed that the co-presence of the Mo dopant and V_s enabled the creation of Mo–Sn–Sn trimer catalytic sites, capable of strongly activating N₂ even for the cleavage of the NN triple bond to the NN double bond at the N₂ adsorption stage, consequently leading to a downhill process of the first hydrogenation step and a largely reduced energy barrier.