Microscale Evolution of Surface Chemistry and Morphology of the Key Components in Operating Hydrocarbon-Fuelled SOFCs

Replacement of hydrogen with hydrocarbon fuels in solid-oxide fuel cells (SOFCs) is an appealing alternative for reducing the implementation costs of SOFCs technology, but the electrode stability and susceptibility to carbon deposition still remain important issues to be solved. The present in situ photoelectron microscopy study of a prototype hydrocarbon-fuelled SOFC, operated at 650 degrees C in C2H4 + H2O gas mixture and voltages in the range 0-3 V, provides insights into morphology-chemistry changes of the Ni electrodes and Cr interconnects with decisive impact on the electrochemical activity and durability. The results reveal the combination of thermal and electromigration of Ni across the electrode-electrolyte interface that can cause sensible material losses and structural changes responsible for the deterioration of device performance. The C 1s spectra evidence deposition of C and formation of carbides on the Ni electrodes and Cr interconnects at 650 degrees C as result of C2H4 dissociation, the process being promoted applying cathodic potential and reversed by switching to anodic potential. Following the attenuation of the C signal under anodic potential, the effect of the stability of different carbides on the reaction rate was observed.