Engineering the Metal-Support Interaction and Oxygen Vacancies on Ru@P-Fe/Fe3O4 Nanorods for Synergetic Enhanced Electrocatalytic Nitrate-to-Ammonia Conversion

Abstract

Ruthenium (Ru) loaded catalysts show high activity and selectivity for ammonia (NH₃) synthesis via electrochemical reduction of nitrate (NO₃⁻), but their practical application is still restricted by their high cost and insufficient stability. Herein, a multi-component electrocatalyst of Ru nanoclusters loaded on phosphorus-doped/phosphate-modified and oxygen vacancy (O_V)-rich Fe/Fe₃O₄ composite nanorods (Ru@P-Fe/Fe₃O₄) to synergistically promote electrocatalytic NO₃⁻ reduction reaction (NO₃⁻RR)-to-NH₃ performance via strong metal-support interaction (SMSI) is reported. Impressively, the best Ru@P-Fe/Fe₃O₄ catalyst exhibits outstanding NO₃⁻RR activity, selectivity, and durability in 0.1 M KNO₃ + 0.5 M KOH solution, with an NH₃ yield rate of 14.37 ± 0.21 mg_NH3 h⁻¹ cm⁻² (1710.71 ± 25 mg_NH3 h⁻¹ mg_Ru⁻¹) at −0.75 V versus reversible hydrogen electrode (vs. RHE), an NH₃ Faradaic efficiency (FE) of 97.2% at −0.55 V vs. RHE, and a superior stability over 50 h, suppressing most of reported Fe-based and Ru-based electrocatalysts. The characterizations and theoretical calculations unveil that the SMSI between Ru nanoclusters and P-Fe/Fe₃O₄ composite nanorods can promote the generation of O_V, tune the electronic structure of Ru species, and stabilize Ru nanoclusters, thereby reducing the reaction energy barrier of NO₃⁻RR-to-NH₃, inhibiting the competitive hydrogen evolution reaction, and boosting the NH₃ yield rate NH₃ FE, and stability.