Ammonia (NH3) is one of the most essential ingredients on earth as it has been widely applied in fertilizer manufacture and as a source of green energy. Artificial nitrogen fixation exceeds 2% of the world consumption based on the traditional Haber-Bosch process, but it is realized at high temperature and pressure and at a cost of CO2 emission. Electrochemical reduction of N-2 to NH3 is thus deemed as an alternative and effective approach for nitrogen fixation at ambient conditions. Nevertheless, efficient and selective catalysts are indispensable to split the strong N N triple bonds. In this work, 8 mol% Y2O3 doped zirconia nanoparticles (8YSZ-NPs) is used as a noble-metal free catalyst for reducing nitrogen to ammonia, which enhances the performances of zirconia and ytrria to a high faradic efficiency (FE) of 12.3% and a large NH3 yield of 10.84 mu g h(-1) mg(cat)(-1) in 0.1 M Na2SO4 electrolyte at - 0.5 V vs. reversible hydrogen electrode, which also shows a preeminent selectivity and high electrochemical stability even compared with the catalysts running under high temperature and pressure.