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

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 N adsorption and activation is essential for nitrogen fixation. Herein, we introduced surface oxygen vacancies in bimetal oxide NiMnO by pyrolysis at 450 °C (450-NiMnO) to achieve remarkable NRR activity. The NiMnO 3D nanosphere with a rough surface could increase catalytically active metal sites and introduce oxygen vacancies that are able to enhance N adsorption and further improve the reaction rate. Benefiting from the introduced oxygen vacancies in NiMnO, 450-NiMnO showed excellent performance for nitrogen reduction to ammonia with a high NH yield of 31.44 μg h mg (at -0.3 V RHE) and a splendid FE of 14.5% (at -0.1 V RHE) in 0.1 M KOH. 450-NiMnO also shows high long-term electrochemical stability with excellent selectivity for NH formation. N isotope labeling experiments further verify that the source of produced ammonia is derived from 450-NiMnO. The present study opens new avenues for the rational construction of efficient electrocatalysts for the synthesis of ammonia from nitrogen.