Ruthenium Effect on Formation Mechanism and Structural Characteristics of LaCo1–xRuxO3Perovskites and Its Influence on Catalytic Performance for Hydrocarbon Oxidative Reforming

This work deals with the formation mechanism of LaCo1-xRuxO3 perovskites (x = 0, 0.05, 0.1, 0.2 and 0.4). In situ characterization of perovskite during formation were monitored with X-ray diffraction and Raman spectroscopy techniques, revealing that perovskite formation occurs via an oxo-lanthanum carbonate intermediate phase. Structural characterization of perovskites showed structural changes in the perovskite as the Ru inserted in the structure increases. It was observed that the insertion of Ru affects the bulk structure by creating rotational and Jahn-Teller distortions in the perovskite structure. Raman spectroscopy completed the description, proving the strong distortions of the lattice oxygen and the La-O coordination induced by the presence of ruthenium. Such distorted configuration gave rise to a weakening of metal-oxygen bonds, maximizing anionic mobility and reactants adsorption. Surface changes were also observed with the insertion of Ru in the perovskite structure. XPS showed that there are cobalt spinel species, unaltered by ruthenium, and lanthanum oxide species that become more carbonated when Ru is present. The formation of carbonate-like structures is enhanced by ruthenium, which must be interacting with lanthanum entities, loosening La-O bonds in order to facilitate the adsorption of CO2. Relating these structural effects with catalytic performance in hydrocarbons reforming, we can conclude that the structural distortion induced by ruthenium favours catalytic stability, probably by stabilizing metallic Co and Co-Ru sites, increasing metal dispersion and by making oxygen mobility easier in the disturbed La2O3 supportThe authors gratefully acknowledge the support provided by the Spanish Ministry of Economy and Competitiveness (MINECO) under grant CTQ2013-48669-P and by CAM under grant S2013/MAE-2882. Our appreciation goes to I. Peral and C. Popescu for their help in the acquisition of HR-XRD at MSPD ALBA beamline. We thank J. Hanson and W. Xu for their help in performing the TR-XRD experiment at X7B beamline (NSLS). We also wish to thank N. Marinkovic for his help in the XAFS measurements at X18B (NSLS). Use of the National Synchrotron Light Source, BNL, was supported by the US DoE, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886.Peer reviewe