Electrochemically plated nickel-decorated ceria nanostructures for direct hydrocarbon solid oxide fuel cell electrodes

Abstract

Solid oxide fuel cells can, in principle, use natural gas as a fuel and thus are attracting attention as promising next-generation energy conversion devices. However, severe carbon deposition (coking) in the state-of-the-art Ni-yttria-stabilized zirconia (YSZ) anode remains a grand challenge. Here, we address this issue by coating a highly porous ceria layer uniformly decorated with Ni nanoparticles over a Ni-YSZ anode via a simple two-step cathodic electrochemical deposition process. The size and distribution of the Ni nanoparticles are successfully controlled by the deposition time and the physical and chemical properties of the resulting composite coatings are characterized by SEM, TEM, XRD and EDS. Their catalytic activities toward methane steam reforming and hydrogen electro-oxidation reactions are evaluated by gas chromatography and AC impedance spectroscopy, respectively. The nanocomposite coatings show a high level of internal reforming reactivity and excellent H-2 electro-oxidation reactivity. As a result, only 15 minutes of the two-step deposition reduces the electrode resistance of the model Ni-YSZ anode (patterned Ni||YSZ||patterned Ni) to nearly 1/300 of the original level in 3% humidified CH4 at 550 degrees C and allows stable operation for 90 hours at 650 degrees C. These results present a useful strategy for implementing high-performance and robust anodes for direct-hydrocarbon utilization.