Electrocatalytic N2 reduction to NH3 under ambient conditions is an eco-friendly and sustainable alternative to the traditional Haber-Bosch process.However,inhibited by the high activation barrier of N2,this process needs efficient electrocatalysts to adsorb and activate the N2,enabling the N2 reduction reaction (NRR).Herein,we report that porous LaFeO3 nanofiber with oxygen vacancies acts as an efficient NRR electrocatalyst with abundant active sites to enhance the adsorption and activation of N2.When tested in 0.1 M HCl,such electrocatalyst achieves a high Faradaic efficiency of 8.77％ and a large NH3 yield rate of 18.59 μg h-1 mgcat.-1 at-0.55 V versus reversible hydrogen electrode.This catalyst also shows high long-term electrochemical stability and excellent selectivity for NH3 formation.Density functional theory calculations reveal that,by introducing oxygen vacancy on LaFeO3,the subsurface metallic ions are exposed with newly localized electronic states near the Fermi level,which facilitates the adsorption and activation of N2 molecules as well as the subsequent hydrogenation reactions.