Electrochemical synthesis of ammonia from N2 and H2O based on (Li,Na,K)2CO3–Ce0.8Gd0.18Ca0.02O2−δ composite electrolyte and CoFe2O4 cathode

• (Li,Na,K)2CO3–Ce0.8Gd0.18Ca0.02O2−δ electrolyte was used ammonia synthesis.
• High ionic conductivity was observed in (Li,Na,K)2CO3–Ce0.8Gd0.18Ca0.02O2−δ.
• Ammonia was synthesised from N2 and H2O at intermediate temperature.
• Ammonia formation rate was 6.5 × 10−11 mol s−1 cm−2 at 400 °C and 1.6 V.

Electrochemical synthesis of ammonia from water vapour and nitrogen was investigated using an electrolytic cell based on CoFe2O4–Ce0.8Gd0.18Ca0.02O2−δ (CFO-CGDC), CGDC-ternary carbonate composite and Sm0.5Sr0.5CoO3−δ–Ce0.8Gd0.18Ca0.02O2−δ (SSCo-CGDC) as cathode, electrolyte and anode respectively. CoFe2O4, CGDC and SCCo were prepared via a combined EDTA-citrate complexing sol–gel and characterised by X-ray diffraction (XRD). The AC ionic conductivities of the CGDC-carbonate composite were investigated under three different atmospheres (air, dry O2 and wet 5% H2–Ar). A tri-layer electrolytic cell was fabricated by a cost-effective one-step dry-pressing and co-firing process. Ammonia was successfully synthesised from water vapour and nitrogen under atmospheric pressure and the maximum rate of ammonia production was found to be 6.5 × 10−11 mol s−1 cm−2 at 400 °C and 1.6 V which is two orders of magnitude higher than that of previous report when ammonia was synthesised from N2 and H2O at 650 °C.