Studies on Electrochemical Performance of Mn- and Y-Codoped CeO2 under Pure and Impure Hydrogen Fuels

Currently, research has been focusing on the development of mixed ionic electronic conductors (MIECs) for applications in catalysis, gas separation membranes and solid oxide fuel cells (SOFCs). The present anode Ni/Y-doped ZrO2 (YSZ) is suffering from coking, sulfur poisoning under hydrocarbon fuels.    Doped ceria has shown mixed ionic electronic characteristics under reducing atmosphere that could be potentially promising anode for solid oxide fuel cells. Using MIEC electrode materials is expected to enlarge electrochemical reaction zone (ERZ) over the entire electrode-gas interfacial area and alleviate or inhibit anode poisoning.

Here, we report synthesis and electrochemical properties of novel nanostructured CYMO (Ce_0.8Y_0.1Mn_0.1O_2-δ)   prepared by autocombustion method using metal salt precursors. The investigated samples were characterized using several solid state techniques such as powder X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDX), and infrared spectroscopy (IR). The electrochemical performance of the prepared anode was tested using a symmetrical cell CYMO/YSZ/CYMO at 600-800^○C in humidified H₂ / N₂ under open circuit and polarization conditions using ac electrochemical impedance spectroscopy (EIS) and DC method. Area specific resistance (ASR) of 0.3 Ωcm² at 800^oC was observed for CYMO and is comparable to that of Ni-YSZ / Ni-ScSZr (0.185 Ωcm²)¹ and La_0.65Ce_0.1Sr_0.25Cr_0.5Mn_0.5O_3-δ (0.2 Ωcm²) .² Interestingly, a noticeable enhancement in the performance of the symmetrical cell was observed upon exposing the cell to 10 ppm H₂S in H₂ / N₂ (Fig.1).   In this talk, a detailed analysis for electrochemical results will be presented.