Combination of Pressure Modulation and Impedance Spectroscopy for Study of Electrode Kinetics on Solid Electrolytes: The Porous Gold/Solid Sodium Carbonate Interface

An experimental scheme for the analysis of electrode kinetics on solid electrolytes using a combination of pressure modulation and electrochemical impedance spectroscopy is described. The data interpretation involves two-port electrical equivalent circuits. Application to the Au/solid Na{sub 2}CO{sub 3} interface reveals that only one of the two electrode processes found in the impedance spectra determines the response behavior to O{sub 2} and CO{sub 2} partial pressure modulation. The rate-determining step is assigned to the formation of oxygen radical anions O{sup {minus}} from molecular oxygen at the Na{sub 2}CO{sub 3} covered Au surface. Porous electrodes on solid electrolytes are important in high-temperature fuel cells, environmental gas sensors, oxygen pumps, and solid-state electrolyzers.