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The electrochemical synthesis of ammonia using solid electrolyte fuel cells with proton conducting solid electrolyte, yttrium-doped barium cerate, was investigated at intermediate temperature (around 500°C). Ru-based electrode catalysts consisting of a mixed ionic-electronic conductor containing Ru active sites, i.e., electrode catalysts with highly dispersed Ru nanoparticles on a lanthanum strontium titanate support, were synthesized. Pd-based catalyst (AgPd) was also examined for comparison. A two-electrode configuration was used with a dynamic hydrogen electrode as the counter electrode. Ammonia formed on the working electrode through reaction of nitrogen with protons diffused from the counter electrode with Ru-and Pd-based catalysts. The ammonia production rate was influenced by the electrode potential; it was maximum at -500 to -1000 mV. The faradaic efficiency of ammonia formation with Ru-based catalyst was 2%, whereas that with Pd-based catalyst was lower than 1%. Highly dispersed Ru active sites may contribute to improving the faradaic efficiency.

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