Activation and Ripening of Impregnated Manganese Containing Perovskite SOFC Electrodes under Redox Cycling

Abstract

The impregnation of electrode precursor solutions is a very powerful technique for creating novel electrode microstructures constrained within preformed scaffolds. Here we report on the microstructural evolution of Mn-containing perovskites impregnated into yttria stabilized zirconia scaffolds on heating and redox cycling. Good performances have previously been reported for SOFC anodes with similar structure, and our objective is to better understand the origins of this good performance. For La 0.75 Sr 0.25 Cr 0.5 Mn 0.5 O 3-δ a remarkable thin coating with microfissures is formed on the scaffold after firing the electrode precursors at 1200 °C, and such behavior can be considered as wetting of one oxide by another. On further treating this microstructure at 800 °C in H 2 the microstructure changes dramatically forming an interconnected array of ∼10 nm scale particles. This seems to offer a very attractive structure with extensive triple phase boundary regions where electrochemical reactions can occur. On reoxidation at this temperature the particles reagglomerate to form a structure approaching the initial smooth coating. Performing similar procedures on the system La 0.33 Sr 0.67 Ti x Mn 1-x O 3(δ , we find that the wetting only occurs if Mn is present in the oxide and that the degree of wetting increases with Mn concentration. This favorable interaction between the Mn containing perovskites and the zirconia scaffold must be associated with a chemical interaction between impregnated oxide and substrate. The strength of this interaction decreases on reduction allowing the perovskite electrode to form nanoscale particles which along with appropriate additional catalysts provide good electrode functionality.

Evolution of the electrochemical interface in high-temperature fuel cells and electrolysers

“…Interestingly, MIECs are often activated by redox cycles, even those that are chemically and dimensionally stable both in air and fuel environments. Coatings of (La,Sr)(Cr,Mn)O3 (LSCM) or CGO nanoparticles on certain ionic or electronic conducting backbones have been observed to change morphology and surface area after a redox cycle 58,66,67 . Finally, more extreme surface changes driven by exposure of certain oxides to low pO2 or cathodic polarisation is the exsolution of reduced (metallic or oxide) nanoparticles from the oxide, which can be reversed by redox cycles.…”

Investigation of Microstructural and Electrochemical Properties of Impregnated (La,Sr)(Ti,Mn)O3±δ as a Potential Anode Material in High-Temperature Solid Oxide Fuel Cells

“…The manganese content was found to have a significant effect on the microstructure. 43 As with LSCM, the morphology of these compounds was found to undergo a transformation into nanostructures upon reduction. The ABSTRACT: The microstructural and electrochemical properties of La 0.4 Sr 0.6 Ti 0.8 Mn 0.2 O 3(δ (LSTM) fabricated via liquidphase impregnation have been investigated for solid oxide fuel cell (SOFC) applications.…”

Synthesis of Na2WO4-Mn Supported YSZ as a Potential Anode Catalyst for Oxidative Coupling of Methane in SOFC Reactor

“…However, the SiO2 support had low electrical conductivity, thus it was required to be mixed with a conductive component such as silver to increase the electrical conductivity [10]. In addition, the performance-limiting factor in solid oxide fuel cells (SOFC) is often the electrode impedance [11][12][13] which can be avoided by using low-temperature, infiltration procedures to synthesize the electrodes [14][15][16][17]. This procedure involves a preparation of porous YSZ (dense YSZ is the electrolyte) scaffold together with the electrolyte layer, then infiltrating the required precursor salts to form the particle within the scaffold.…”