Nanostructured Pd/lanthanide-doped ceria spheres with high catalytic activity for CH4 combustion

R. O. FUENTES; R. T. BAKER; J. J. DELGADO-JAÉN; L. M. ACUÑA; H. PAN; A. G. LEYVA; X. CHEN

Buenos Aires

Workshop; 1st Argentine-German Workshop on Nanotechnology and Nanobiosensors (A-G Nanobio); 2017

Ceria-based mixed oxides are materials with a large technologicalimpact, especially in the area of environmental protection.Nanostructured ceria materials can be used as supports for highlydispersed noble metal nanoparticles. The resulting catalystsystems exhibit much improved catalytic activity and redoxproperties. In particular, Pd-based catalysts are active for NOreduction and CO and hydrocarbon oxidation reactions. Enhancedmetal-support interactions led to exceptionally high methaneoxidation, with complete conversion below 400°C. [1]In this work, nanostructured Ce0.9Ln0.1O2-d (LnDC; Ln: Gd, Pr)spheres previously obtained by microwave assisted hydrothermalhomogeneous co-precipitation (HMW)[2,3] were impregnatedwith 1% wt Pd by incipient wetness impregnation (WI) of anaqueous Pd2+ solution. Their properties were characterized bysynchrotron radiation X-ray diffraction (SR-XRD), X-rayabsorption near-edge spectroscopy (XANES) and scanning andhigh resolution electron microscopy (SEM and HRTEM) with Xrayspectroscopy (EDS). In situ XRD and XANES experimentswere carried out under reducing and oxidizing conditions in orderto investigate the redox behaviour of these materials. Theaddition of Pd to the LnDC increased the reducibility of the Ce inthe mixed oxide. This was demonstrated by analysis of in situXANES spectra obtained under reducing conditions. Clearly, thePd improves the Ce3+/Ce4+ redox couple in LnDC materials. Highactivity for CH4 oxidation was observed in nanostructruredPd/LnDC spheres with a total conversion of CH4 temperaturelower than 400ºC. In fact, the reaction rates here reported at350ºC show the highest efficiency per palladium atom incomparison with other palladium-based catalysts reported inliterature. [1,4] These findings open up an interesting avenue forfuture working this area, and indicate a promising possibleapplication for this particular system.