Anodic behaviour of Y_0.20Ti_0.18Zr_0.62O_1.90 towards hydrogen electro-oxidation in a high temperature solid oxide fuel cell

The electrochemical oxidation of humid hydrogen was investigated on a Y_0.20Ti_0.18Zr_0.62O_1.90 (YTZ) anode in a high temperature planar solid oxide fuel cell. Cells using platinum counter and reference electrodes on a YSZ based electrolyte were fabricated and tested in H2/H₂O atmospheres versus air in the temperature range (788-932) °C. Steady state polarisation measurements, cyclic voltammetry and impedance analysis were used to characterise the behaviour of the anode and determine kinetic parameters of the electro-oxidation reaction. The power output of the cell H₂,H₂O/YTZ//YSZ-Al₂O₃//Pt/air was stable over an operation period of 500 h. For 97%H₂/3%H₂O at 932 °C it amounted to 37 mW cm^-2 and the maximum current density obtained was 203 mA cm^-2. The apparent reaction order with respect to hydrogen was calculated to be in the region of 0.5 at 932 °C. The impedance spectra showed three apparent processes dependent on temperature, fuel concentration and overpotential. Anode polarisation resistance decreased significantly with anodic overpotential. At open and short circuit (E^cell = 0 V) conditions the total area specific polarisation resistance was 12.67 and 0.96 Ω cm² respectively.