Paper SS2+NC-ThM1
Hybrid Nano-Oxide System for Oxidation of Methanol at Lower Temperatures

Thursday, October 23, 2008, 8:00 am, Room 208

Paradigm shift in the global energy policy towards cleaner and alternate fuels, arising out of uncontrolled green house emissions and rapid depletion of fossil based fuels, paved the way for various challenging areas of research. Among the various alternatives, direct oxidation of alcohols to hydrogen offer one promising alternative to primary fuels. Hydrogen produced from the alcohols can be used as a primary fuel source for DMFCs. Preliminary work on conversion of methanol to hydrogen and other byproducts, in presence of noble metals such as platinum and gold as catalysts, has shown promising results. However, the use of noble metal catalysts makes the conversion an expensive deal. Nanomaterials such as titanium oxide (titania), zirconium oxide (zirconia), cerium oxide (ceria) have been tried as active catalyst supports in varying range of particle sizes and molar ratios of noble metals with limited success. To overcome the hurdles in the existing systems, we have focused on the hybrid ceria-titania nanostructures synthesized using sol gel and co-precipitation methods for optimizing the efficiency of the catalyst in methanol oxidation. The percent conversion of methanol to various species was studied using an in-house built catalytic reactor coupled to a mass spectrophotometer for analysis of gaseous reaction products. The selectivity and efficiency of the hybrid nano-oxide system as a catalyst support was studied as a function of mixture concentration, percent loading of the noble metal catalyst and the phase structure. Experimental results were normalized with respect to the surface area of the supporting catalysts. The adsorption characteristics of methanol and byproducts on the catalyst surface were evaluated using Diffuse Reflectance Infra-red Fourier Transform Spectroscopy (DRIFTS). Powder samples were characterized using X-ray Diffraction (XRD) and Transmission Electron Microscope (TEM) for determining the phase, particle size and shape of the particles in mixed systems. X-ray Photoelectron spectroscopy (XPS) was used to verify the oxidation state of the metal catalyst as well as mixed ceria-titania supports as a function of molar concentration of the constituents. Preliminary results have shown that the onset temperature for methanol decomposition was as low as 150^oC and both the onset as well as complete conversion temperature varies as a function of molar ratio of ceria to titania.