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Haber-Bosch" synthesis is the dominant NH 3 synthesis process. Parallel to catalyst optimization, current research efforts are also focused on the investigation of new methods for ammonia synthesis, including the electrochemical synthesis with the use of solid electrolyte cells. Since the first report on Solid State Ammonia Synthesis (SSAS), more than 30 solid electrolyte materials were tested and at least 15 catalysts were used as working electrodes. Thus far, the highest rate of ammonia formation reported is 1.13 × 10-8 mol s-1 cm-2 , obtained at 80°C with a Nafion solid electrolyte and a mixed oxide, SmFe 0.7 Cu 0.1 Ni 0.2 O 3 , cathode. At high temperatures (>500°C), the maximum rate was 9.5 × 10 −9 mol s-1 cm-2 using Ce 0.8 Y 0.2 O 2-δ-[Ca 3 (PO 4) 2-K 3 PO 4 ] as electrolyte and Ag-Pd as cathode. In this paper, the advantages and the disadvantages of SSAS vs. the conventional process and the requirements that must be met in order to promote the electrochemical process into an industrial level are discussed.

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Abstract. The eleclxokinetics at the H 2 -Pd/SrCeo.95Ybo.0503_ct interphase are presented, Currentoverpotential (I-'q) curves were obtained at 400-700 ~ and at hydrogen partial pressures from 1 kPa to 100 kPa, using a three electrode single chamber cell. The present data were assumed to be free of mass transfer effects. The anodic and cathodic charge transfer coefficients as well as the exchange current density were calculated from the experimental results by using the Butler-Volmer equation. The high and low field approximations were used to simplify the analysis.

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