Preparation and characterization of Ce/Zr mixed oxides and their use as catalysts for the direct oxidation of dry CH4

Solid oxide fuel cells have a promissory future in the direct combustion of fuels but, their main drawbacks are the high operation temperature and the rapid performance degradation due to carbon deposition in the anode. The development of ceria-based anodes with good electronic conductivity at lower temperatures seems to be a promising way to solve those problems. In this work, preparation of compositionally homogeneous Ce/Zr oxides by a gel-combustion process and their characterization are reported. A detailed crystallographic study performed by synchrotron radiation X-ray diffraction has been carried out, in order to analyze the correlation between crystal structure and catalytic properties. The oxides presented specific area values, porous size distribution and carbon content values desirable for solid catalysts. Likewise, increasing the content of ZrO2 facilitates the reducibility of both surface and bulk sites in the solid. The oxides have been active in the combustion of methane. Their performances were stable during a typical work period of 8 h, with no evidence of formation of carbonaceous deposits. The experiments were carried out confirm the promising features of these oxides as anodic materials in solid oxide fuel cells.