Catalytic study of SOFC electrode materials in engine exhaust gas atmosphere

Abstract

A single chamber solid oxide fuel cell (SC-SOFC) is a device able to produce electricity from a mixture of hydrocarbons and oxidant. An innovative application of this system would be to recover energy from exhaust gas of a thermal engine. This paper presents a study of stability and catalytic behaviour of electrode materials composing the cell in a mixture of hydrocarbons (propane, propene), oxygen, carbon monoxide, carbon dioxide, hydrogen and water corresponding to a composition of exhaust gas. A screening of four cathode materials was done, some well-known materials in literature and leading to highest performances such as La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF), Sm0.5Sr0.5CoO3−δ and Ba0.5Sr0.5Co0.8Fe0.2O3−δ and a last one Pr2NiO4+δ (PNO) very promising for conventional SOFCs. Anode material was a cermet composed of nickel and Ce0.9Gd0.1O1.95 which was also selected as the electrolyte material. Chemical stability tests and catalytic activity studies in the gas mixture were performed on the raw materials and have led to a first selection among cathodes. Two hydrocarbons/oxygen ratios (R = HC/O2) were investigated for materials tests considering the gas mixture stability at high temperature (600 °C): R = 0.21 and 0.44. LSCF and PNO were considered as the most stable cathode materials, besides LSCF demonstrated a lower catalytic activity towards hydrocarbon partial oxidation than PNO especially for the R = 0.44 ratio. As for the anode side, nickel was tested regarding its catalytic activity towards hydrocarbons oxidation. It exhibited catalytic activity towards hydrocarbons partial oxidation, especially for the oxygen-lean ratio (0.44), which gradually decreased while lowering temperature from 620 to 450 °C.