Enhanced N2 Electroreduction over LaCoO3 by Introducing Oxygen Vacancies

Electroreduction of N2 into NH3 represents a promising method for N2 fixation. However, due to the inertness of N≡N covalent triple bonds, this process remains a huge challenge to achieve a high yield rate of NH3. In this work, we designed an effective approach to promoting N2 activation by introducing oxygen vacancies into LaCoO3. In N2 electroreduction, LaCoO3 with oxygen vacancies (denoted as Vo-LaCoO3) exhibited a Faradaic efficiency of 7.6% for NH3 at −0.6 V versus the reversible hydrogen electrode (RHE). Notably, at −0.7 V versus RHE, the yield rate for NH3 of Vo-LaCoO3 reached 182.2 μgNH3 mg–1cat. h–1, which was 2.8 times higher than that (65.3 μgNH3 mg–1 h–1) of pristine LaCoO3. To the best of our knowledge, the yield rate for NH3 of Vo-LaCoO3 approaches the activities of the state-of-the-art catalysts toward N2 electroreduction. Density functional theory calculations revealed that enhanced activation of N2 over Vo-LaCoO3 originated from the increased charge density around the valence band edge via the introduction of oxygen vacancies. Furthermore, the analysis of the thermodynamic limiting potentials for N2 reduction and H2 evolution demonstrated the higher selectivity for N2 electroreduction over Vo-LaCoO3 relative to pristine LaCoO3.