Electrochemical synthesis of ammonia based on a carbonate-oxide composite electrolyte

Electrochemical synthesis of ammonia based on carbonate electrolyte is presented in this paper. Spinel oxide CoFe₂O₄ was synthesised via a co-precipitation method and characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Ammonia was successfully synthesised from hydrogen and nitrogen under atmospheric pressure using CoFe₂O₄ as catalyst (primary particle size 10-20 nm) together with silver at the cathode, Ag-Pd at the anode and carbonate-LiAlO ₂ composite as electrolyte respectively. Ammonia formation was observed at 400, 425 and 450 °C and the maximum rate of ammonia production was found to be 2.32 × 10^-10 mol s^-1 cm^-2 at 400 °C and 0.8 V. The AC impedance measurements were recorded before and after the ammonia synthesis at 400, 425 and 450 °C. The electrolytic cell during the ammonia synthesis process was more stable at 450 °C and 0.8 V over a period of 2 h. This experiment also indicates that the carbonate-LiAlO₂ composite electrolyte exhibits proton conduction. © 2010 Elsevier B.V.