Electrochemical ammonia synthesis from steam and nitrogen has been systematically investigated using a proton-conducting electrolyte supported cell based on 20 mol% yttrium doped barium zirconate (BaZr0.8Y0.2O3-delta) in a temperature range of 475-600 degrees C at atmospheric pressure. Silver (Ag), platinum (Pt), and lanthanum strontium cobalt ferrite (La0.6Sr0.4CO0.2Fe0.8O3-delta) are used for both anode and cathode electrocatalysts. Maximum ammonia formation rates of 4.9 x 10(-11) mol cm(-2) s(-1) and 8.5 x 10(-11) mol cm(-2) s(-1) are observed for Ag and La0.6Sr0.4C0.2Fe0.8O3-delta electrocatalysts, respectively, when a voltage of 0.8 V is applied. However, Pt electrocatalyst shows a negligible ammonia formation rate lower than 1 x 10(-12) mol cm(-2) s(-1). This is ascribed to the high activity of Pt for the hydrogen evolution reaction rather than the ammonia formation reaction. The conversion efficiency of all electrocatalysts is below 1%, primarily due to the limited nitrogen disassociation activity of the electrocatalysts. (C) 2015 Elsevier B.V. All rights reserved.