Electrochemical Synthesis of Ammonia With Proton Conducting Solid Electrolyte Fuel Cells at Intermediate Temperatures

摘要

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.