Rate determining steps of fuel oxidation over CeO2 impregnated Ni-YSZ in H2 + H2O + CO + CO2 ambient

Polarization resistance of the Ni-Zr0.84Y0.O-16(1.92) anode impregnated with cerium oxide in H-2 + H2O + CO + CO2 + Ar gas mixtures of different composition was studied at temperatures of 700-950 degrees C by means of EIS and subsequent DRT and NLLS analysis of EIS spectra. The electrochemical activity of the anode in the H-2 + H2O + CO + CO2 + Ar was found to be defined basically by the hydrogen-containing components (H-2 and H2O). The EIS spectra analysis revealed that the anode polarization resistance is determined by three processes, registered at high-, middle-and low-frequencies, respectively. The high-frequency resistance had an activation energy of about -0.93 eV and it did not depend on the gas mixture composition. Both the middle-frequency resistance (activation energy of about -1.04 eV) and the low-frequency resistance (0.31 eV) depended on the gas atmosphere composition. Suggestions about the nature of the rate-determined steps were proposed. (C) 2016 Elsevier Ltd. All rights reserved.