Evaluating the Behavior of CO/CO2 in Ni/GDC Solid Oxide Fuel Cell Anodes

Abstract

To better understand carbon oxide chemistry in Ni/GDC anode functional layers, we have studied CO oxidation and CO2 dissociation on sputtered thin-film GDC (Ce0.8Gd0.2O1.9) electrodes with open Ni sputtered overlayers. The well-characterized electrode allows optical access to study fundamental CO and CO2 reactions around Ni/GDC interfaces in both dry and wet environments. To isolate the GDC chemistry, Ni/GDC cell results were compared to those from GDC films with less active Au overlayers. Dry CO oxidation and CO2 dissociation are slower than their H2 and H2O analogs on Ni/GDC with fitted exchange current densities for CO/CO2 approximately one order of magnitude lower than H2/H2O from 600 to 700 °C. With optical access to the active Ni and GDC interfaces, ambient pressure XPS was used to obtain local overpotentials across the Ni/GDC for some test conditions and thereby extract fundamental information about the CO and CO2 chemistry in the Ni/GDC cell.