Further performance enhancement of a DME-fueled solid oxide fuel cell by applying anode functional catalyst

Abstract

In order to increase the coking resistance of SOFCs operating on DME fuel, a Pt/Al2O3–Ni/MgO mixture catalyst was investigated for internal partial oxidation of DME. Catalytic test demonstrated the mixture catalyst has higher activity for DME partial oxidation and lower CH4 selectivity than the individual Pt/Al2O3 and Ni/MgO catalysts. O2-TPO analysis demonstrated that the mixture catalyst also had much higher coke resistance than sintered Ni-YSZ anode, especially at high O2 to DME ratio. Raman spectroscopy of the carbon-deposited catalysts demonstrates that the graphitization degree of carbon is reduced with introducing O2 into DME, and the carbon deposited on the mixture catalyst is almost in amorphous structure. Two operation modes of the mixture catalyst for indirect internal partial oxidation of DME, i.e, directly depositing on the anode surface and locating in the anode chamber were tried. The performance of the cells operating on DME fuel through both operation modes was studied by I–V polarization test and EIS characterization. The cells delivered attractive peak power density of around 750 mW cm−2 by operating on DME-O2 mixture gas, modestly lower than 1012–1065 mW cm−2 operating on pure hydrogen fuel at 700 °C. The direct deposition of Pt/Al2O3–Ni/MgO onto anode surface to perform as a functional layer and a DME to O2 ratio of 2:1 in the mixture gas is preferred to minimize coke formation and maximize power output for the cell to operate on DME fuel.