Introducing oxygen vacancies in a bi-metal oxide nanosphere for promoting electrocatalytic nitrogen reduction

Abstract

The sluggish breakage of the N–N triple bond, as well as the existence of a competing hydrogen evolution reaction (HER), restricts the nitrogen reduction reaction process. Modification of the catalyst surface to boost N₂ adsorption and activation is essential for nitrogen fixation. Herein, we introduced surface oxygen vacancies in bimetal oxide NiMnO₃ by pyrolysis at 450 °C (450-NiMnO₃) to achieve remarkable NRR activity. The NiMnO₃ 3D nanosphere with a rough surface could increase catalytically active metal sites and introduce oxygen vacancies that are able to enhance N₂ adsorption and further improve the reaction rate. Benefiting from the introduced oxygen vacancies in NiMnO₃, 450-NiMnO₃ showed excellent performance for nitrogen reduction to ammonia with a high NH₃ yield of 31.44 μg h⁻¹ mg_cat⁻¹ (at −0.3 V vs. RHE) and a splendid FE of 14.5% (at −0.1 V vs. RHE) in 0.1 M KOH. 450-NiMnO₃ also shows high long-term electrochemical stability with excellent selectivity for NH₃ formation. ¹⁵N isotope labeling experiments further verify that the source of produced ammonia is derived from 450-NiMnO₃. The present study opens new avenues for the rational construction of efficient electrocatalysts for the synthesis of ammonia from nitrogen.