H2 oxidation on doped yttrium chromites/yttrium stabilized zirconia anode of solid oxide fuel cell

Co and Ni doped yttrium chromites as potential anodes for solid oxide fuel cell (SOFC) are studied with respect to the electrode performance and anode reaction mechanisms. Both electrical conductivity and electrode performance of yttrium chromites have been enhanced after Co and Ni doping. Electrochemical impedance spectroscopy (EIS) results indicate that charge transfer process at high frequency and surface adsorption/diffusion processes at low frequency domain can be the dominant anode reaction steps. Ni doping accelerates the surface processes by reducing the related activation energy from 1.2 to 0.5 eV. It also substantially improves the charge transfer process probably by increasing the amount of adsorbed H on electrode surface. The resistance of high frequency is found to be dependent on H2 content. The observed reaction order is 1/4 for Co doped and 1/3-1/2 for Ni doped yttrium chromites. A model of H2 oxidation reaction is proposed, revealing this dependence stems from the reaction between adsorbed H and the lattice oxygen.