(310a) A Combined Experimental and Theoretical Study for the Conversion of Carbon Dioxide to Carbon Monoxide on Noble Metal Impregnated Perovskite Structures

The last decade has seen lots of interest in achieving efficient conversion of carbon dioxide to carbon monoxide, which is a major energy currency towards generating hydrocarbon energy fuels via Fischer Tropsch synthesis. Amongst the many different types of material being studied for achieving the conversion of carbon dioxide, mixed perovskites have garnered a significant prominence in this field. Novel perovskite materials, La_(1-x)Sr_xCoO₃(x=0.25, 0.5) in particular, impregnated with noble metals like Pt, Ag have been studied for the same purpose. The conversion process involves heating the materials in inert atmosphere of helium gas, resulting in the generation of oxygen vacancies on the surface of these materials. These heated oxygen vacant materials are proposed as active sites for the dissociation of carbon dioxide to carbon monoxide.

   La_0.75Sr_0.25CoO₃ and La_0.5Sr_0.5CoO₃ samples had been prepared by Pechini process. They revealed the presence of mixed crystal phases like cubic, hexagonal and orthorhombic of which cubic phase had the major prominence as was evident from the X-ray diffraction (XRD) patterns. Controlled temperature programmed reactions were conducted to probe the two stage carbon dioxide conversion cycle. The reaction acutely depends on the various structural and electronic states of the material surface. Hence a theoretical analysis of the materials and the process was undertaken using density functional theory (DFT) calculations in order to hypothesize the reaction mechanism involved and to propose the best material candidate for this reaction. Based on the DFT calculations, the most stable bulk phase crystal structure of these materials have been proposed and the various surface states along the major crystal planes (100) and (110) were investigated. Dissociative chemisorption energy is a key representative parameter for studying these reactions. Henceforth a systematic study has been pursued towards obtaining a trend in the dissociative chemisorption energy as a function of the structural and electronic properties of the material.