Electrocatalytic ammonia synthesis via a proton conducting oxide cell with BaCe_0.5Zr_0.3Y_0.16Zn_0.04O_3-δ electrolyte membrane

Ceramic membrane cells of BaCe_0.5Zr_0.3Y_0.16Zn_0.04O_3-δ (BCZYZ) have been developed for electrocatalytic ammonia syn-thesis. Unlike the high-pressure Haber-Bosch process, an atmospheric synthesis of ammonia was attempted in this work. The membrane cells were fabricated by tape casting and the electrode materials were applied by ion impregnation. The impregnated electrodes comprised NiO/CeO₂ composite anode and iron oxide cathode. The formation of ammonia was studied in the range of 400–500 °C. The addition of Pd catalyst into the iron oxide cathode enhanced the ammonia forma-tion rate while the addition of Ru improved only the electrochemical performance. The highest ammonia formation rate of 4 × 10⁻⁹ mol s⁻¹ cm⁻² was obtained from Pd-modified cell at 450 °C. The current efficiency of ammonia formation was in the range of 1–2.5% while that of H₂ evolution varied from 0 to 60% depending on applied potentials. The total current efficiency close to 100% was obtained from Pd-modified cell.