Electrochemically modified, robust solid oxide fuel cell anode for direct-hydrocarbon utilization

Abstract

A main advantage of solid oxide fuel cells (SOFCs) operating at a high temperature (>650°C) is the flexibility of the fuel they use, specifically as they offer the possibility to utilize methane (natural gas). Unfortunately, however, the state-of-the-art SOFC anodes, composed of a nickel and an anionically conducting oxide such as yttria-stabilized zirconia (YSZ), are associated with Ni-catalyzed carbon deposition and the ensuing degradation of the anode performance. Here, we address these issues through the application of a simple, scalable, cost-effective ceramic coating method known as cathodic electrochemical deposition (CELD). Samaria-doped CeO2 (SDC) was chosen as the coating material due to its high chemical stability against carbon formation, high electronic and ionic conductivities, and favorable electrocatalytic activity toward fuel oxidation reaction. Nanostructured SDC layers with a high specific surface area were successfully coated onto Ni surfaces via CELD. The physical and chemical attributes of each coating were characterized by a range of analysis tools, in this case SEM, TEM, XRD, EDS, ICP-MS and Raman spectroscopy. An analysis of the AC impedance spectroscopy (ACIS) of Ni-patterned YSZ symmetric cells (anode|electrolyte|anode) with SDC coatings revealed significantly enhanced electrode activity toward fuel oxidation and coking stability under dry or wet methane fuel at 650°C. These results suggest that the Ni-surface modification via CELD can be a feasible solution for the direct use of hydrocarbon fuels in SOFCs.