Electrochemical synthesis of ammonia based on doped-ceria-carbonate composite electrolyte and perovskite cathode

Electrochemical synthesis of ammonia was investigated using a cobalt-free La0.6Sr0.4Fe0.8Cu0.2O3-δ-Ce0.8Sm0.2O2-δ (LSFCu-SDC) composite cathode and SDC-ternary carbonate composite electrolyte. La0.6Sr0.4Fe0.8Cu0.2O3-δ and Ce0.8Sm0.2O2-δ were prepared via combined EDTA-citrate complexing sol–gel and glycine nitrate processes, respectively, and characterised by X-ray diffraction (XRD). Ammonia was successfully synthesised from wet hydrogen and dry nitrogen under atmospheric pressure using Ni-SDC, SDC-carbonate and LSFCu-SDC composites as anode, electrolyte and cathode respectively. Ammonia formation was observed at 400, 425, 450 and 475 °C and the maximum rate of ammonia production was found to be 5.39 × 10−9 mol s−1 cm−2 at 450 °C and 0.8 V. The AC impedance measurements were recorded before and after the ammonia synthesis in the range of temperature 400–475 °C. The formation of ammonia at the N2 side together with stable current at 450 °C under constant voltage demonstrates that SDC-(Li/Na/K)2CO3 composite electrolyte exhibits significant proton conduction at a temperature around 450 °C.

► Synthesis of ammonia based on SDC-ternary carbonate composite electrolyte.
► La0.6Sr0.4Fe0.8Cu0.2O3-δ was used for electrochemical synthesis of ammonia.
► An ammonia formation rate of 5.39×10-9 mol s-1 cm-2 was achieved at 450 ºC.
► The SDC-ternary carbonate composite exhibits significant proton conduction.