Ni/YSZ anode is a well-studies catalyst in solid oxide fuel cell which works best in hydrogen. Hydrogen does not naturally exist and is produced by steam reforming of hydrocarbon fuels. High operating temperature of solid oxide fuel cells has made them popular for direct oxidation of hydrocarbons. A direct hydrocarbon SOFC will remove the energy losses and complexities of the external reformers but introduces problems such as coking and sulfur poisoning which both lead to anode deactivation.
Anode modification is required to develop a direct hydrocarbon SOFC. Cu electroless plating has been studied as an approach to improve the durability of Ni/YSZ anode both in pure and sulfurous CH4. The first objective of this study was to investigate the effect of Cu concentration on the durability of the Cu electroless plated anode operated in CH4. Two cells with different Cu concentrations were studies under long-term exposure to CH4 for this purpose. The second objective was to investigate the effect of the Cu electroless plated anode on increasing the sulfur tolerance of the Ni/YSZ, while exposed to sulfurous fuel. A Ni/YSZ anode and a Cu electroless plated anode were exposed to mixture of CH4 and SO2 and their performance were compared.
The long-term durability was measured by polarization curves and electrochemical impedance spectroscopy (EIS). The experiments were complemented by post characterization of cells with scanning electron microscopy (SEM), dispersive X-ray spectroscopy (EDS), X-ray fluorescence (XRF), and X-ray diffraction (XRD). Results of this study showed that Cu electroless plating was successful in increasing the durability of Ni/YSZ anode in CH4 and sulfurous fuels. High Cu concentration on the surface and well diffusion of Cu into Ni/YSZ matrix was required to prevent coking.