Ce 0.8 M 0.2 O 2 − δ ( M = Mn , Fe , Ni

Abstract

Oxide anodes such as doped ceria offer improved tolerance for nonidealities in anode environment such as redox cycles, sulfur and other poisons, and hydrocarbons. Mixed-valence transition element in ceria provides an additional redox couple besides Ce4+∕Ce3+ in reduced atmosphere, facilitating its electrocatalytic reaction for oxidation of fuels. This paper presents the electrochemical characteristics of Ce0.8M0.2O2−δ(M=Mn,Fe,Ni,Cu) for oxidation of hydrogen and methane. Ce0.8M0.2O2−δ was synthesized, and crystal phase analysis by X-ray diffraction was performed. Single-phase Ce0.8M0.2O2−δ(M=Mn,Fe,Ni) were formed. A second phase, CuO, was found in the powders with the nominal composition of Ce0.8Cu0.2O2−δ. Ce0.8M0.2O2−δ exhibited stability in reducing atmosphere. In comparison, similar microstructural characteristics were found for Ce0.8M0.2O2−δ(M=Mn,Fe,Cu). However, Ce0.8Ni0.2O2−δ exhibits poor microstructure with large cracks. The electrochemical oxidation of wet hydrogen and wet methane was investigated with impedance spectroscopy by using the three-electrode configuration. It was found that Ce0.8M0.2O2−δ(M=Mn,Fe,Ni,Cu) demonstrates relatively low electrochemical activity in both hydrogen and methane. Regarding low n-type conductivity of transition metal cation-containing ceria, it was suggested that an oxide with a high electronic conductivity be added into the Ce0.8M0.2O2−δ matrix for improvement of the electrode performance.

Synthesis, Structure and Electrical Properties of Mo‐doped CeO2–Materials for SOFCs

“…H 2 , CH 4 ) as a result of mixed ionic and electronic conduction [16,20,23,30]. The excellent catalytic activity for fuel oxidation stems from the oxygen-vacancy formation and migration associated with reversible CeO 2 -Ce 2 O 3 transition [31][32][33][34]. Ceria also shows excellent stability against coke-formation [16], which permits the direct supply of dry hydrocarbon fuels to the anode.…”

“…However, the major concern is the low electronic conductivity of ceria-based anodes, which increases the overall impedance of SOFCs. Therefore, introducing elements with multiple oxidation states might enhance the electronic conductivity, and also facilitate catalytic activity [34][35][36][37][38][39][40].…”

Mo‐doped CeO2 Synthesized by the Combustion Method for Carbon‐Air Solid Oxide Fuel Cell (CA‐SOFC) Applications

“…Cerium dioxide or ceria (CeO 2 ) has shown an excellent electrocatalytic activity for oxidation of carbonaceous fuels, due to the CeO 2 ‐Ce 2 O 3 transition taking place during this process ; besides it does not suffer from carbon deposition and presents both electronic and ionic conductivity at high temperatures (above ca. 700 °C) and under low oxygen partial pressures , .…”

Synthesis of Mo-doped CeO2by the Combustion Method for Carbon-Air Fuel Cells Applications: Study of Composition, Crystalline Structure and Mechanical Properties

“…In this respect, ceria (CeO 2 ) appears as a material of interest due to its catalytic activity in the oxidation of carbonaceous fuels and its good tolerance to sulfur poisoning (5). However, ceria-based materials present low electronic conductivity for SOFCs applications, thus it needs to be improved by doping ceria with other metal oxides, such as molybdenum trioxide (MoO 3 ) which shows similar catalytic and stability properties than ceria (6)(7)(8)(9).…”