The electrocatalytic reduction reaction of nitrate (NO3−) to ammonia (NH3) provides an efficient and clean NH3 production method, which has the potential to replace the traditional industrial preparation methods. However, the limited activity and Faraday efficiency (FE) of existing catalysts impede the practical application of this technology. Herein, in this work, a high-performance catalyst with high NH3 yield and FE was fabricated. Co–Ni bimetallic oxide (NiCo2O4) catalysts with tuned surface oxygen vacancies (OVs) contents were prepared by changing the heating rate during calcination, NiCo2O4 calcined at a heating rate of 5 °C/min (NiCo2O4-5) possessed the highest surface OVs content. Experimental studies showed that NiCo2O4 with higher surface OVs had better NO3RR activity, inhibited the production of nitrite (NO2−), and exhibited higher selectivity to NH3. Among prepared catalysts, NiCo2O4-5 demonstrated superior performance in electrocatalytic reduction of NO3− to NH3, achieving a high NH3 FE (94.4 %) and yield (193.2 mmol/h g−1) at a suitable applied voltage. Besides, in situ Fourier transform infrared spectroscopy analysis suggested that NiCo2O4-5 preferentially followed the NO3RR pathway as follows: *NO3 → *HNO3 → *NO2 → *HNO2 → *NO → *HNO → *N → *NH → *NH2 → *NH3.
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