The electrochemical synthesis of ammonia from N2 and H+ ions was studied over a Ni–BZCY72 cermet, with and without H2 in the gas phase. The effect of temperature, cathode chamber feed composition and applied voltage was explored in detail. Without H2 in the cathode chamber, the highest rate was 1.7×10−9mol/s·cm2 at 620°C. When H2 was present in the gas phase, ammonia was synthesized electrochemically at much higher rates and Faradaic efficiencies. The maximum net electrochemical synthesis rate of 4.1×10−9mol/s·cm2 was obtained with ΡΗ2/ΡΝ2=1 at 620°C, corresponding to a 140% enhancement of the open circuit rate at the cost of electrical energy. In both cases these high rates were accompanied by a low Faradaic efficiency, pointing to the need for catalyst improvement. •Electrochemical synthesis of ammonia is enhanced by co-feeding H2 to the cathode.•A high open circuit rate can be electrochemically enhanced by up to 140%.•Electrochemical synthesis is optimal at equimolar and not at stoichiometric feed.•High current densities can have a negative effect on electrochemical synthesis.