Nitrogenase-Inspired Vs-MoS2/Vo-Fe2O3 Heterojunction with Fixed Molar Ratio Promotes Bifunctional Nitrogen Fixation

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The development of efficient heterojunction catalysts for electrochemical bifunctional nitrogen reduction reaction (NRR) and nitrate reduction reaction (NO 3 RR) as a replacement for the Haber–Bosch (H–B) process is on the stage, yet the controlled synthesis of heterojunction catalysts with fixed composition ratios remains a formidable challenge. Herein, we employed oxygen-rich polyoxometalates (POMs) as precursors to form a metal sulfide/metal-oxide heterojunction catalyst via the one-pot method, specifically nanoflower-like MoS 2 /Fe 2 O 3 heterojunctions enriched with vacancies (Vs-MoS 2 /Vo-Fe 2 O 3 ). Notably, the composition ratio of the heterojunction precisely mirrors the proportion of metal components in the POMs. This catalyst has demonstrated efficient all-pH nitrogen reduction activity, with the highest performance observed in acidic electrolytes (NH 3 yield rate = 73.14 ± 1.35 μg h –1 mg –1 cat., Faraday efficiency = 42.68 ± 2.12%). Simultaneously, it exhibits superior nitrate reduction activity in neutral electrolytes (Selectivity = 97.50 ± 0.75%, Faraday efficiency = 80.39 ± 3.71%). In situ Raman spectroscopy, extended X-ray absorption fine structure spectroscopy (EXAFS) combined with Density functional theory (DFT) calculations have verified that superior catalytic activity of Vs-MoS 2 /Vo-Fe 2 O 3 can be primarily attributed to facile N 2 adsorption at S vacancies, an electronic coupling between Fe and Mo, enhanced conductivity at heterojunctions, and a reduced Gibbs free energy for NH* hydrogenation to NH 2 * at O vacancies.