The effect of the nature of the support and the promotion achieved by a Rh additive on Co-based catalysts in the ethanol steam reforming reaction were studied. The catalysts with 2% Co loading were characterized by temperatureprogrammed reduction (TPR) and X-ray photoelectron spectroscopy (XPS). In situ diffuse reflectance Fourier-transform infrared spectroscopy (DRIFTS) identified the surface intermediates formed during the reaction, whereas gas phase products were detected by gas chromatography (GC). Upon heating in hydrogen to 773 K, cobalt could not be reduced to Co 0 on alumina, but on silica the reduction was almost complete. On ceria, half of the Co could be reduced to the metallic state. By the presence of a small amount (0.1%) of Rh promoter, the reduction of both cobalt and ceria was greatly enhanced. For Co on the acidic Al 2 O 3 support, the dehydration mechanism was dominant, although on the basic CeO 2 support, a significant amount of hydrogen was also formed. Addition of a small amount of Rh as promoter to the Co/CeO 2 catalyst resulted in a significant further increase in the hydrogen selectivity.
The interaction of CeO 2 -supported Rh, Co and bimetallic Rh-Co nanoparticles, which are active catalysts in hydrogen production via steam reforming of ethanol, a process related to renewable energy generation, was studied by X-ray diffraction (XRD), high resolution electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and low energy ion scattering (LEIS). Furthermore, diffuse reflectance infrared spectroscopy (DRIFTS) of adsorbed CO as a probe molecule was used to characterize the morphology of metal particles. At small loadings (0.1%), Rh is in a much dispersed state on ceria, while at higher contents (1-5%), Rh forms 2-8 nm particles. Between 473-673 K pronounced oxygen transfer from ceria to Rh is observed and at 773 K significant agglomeration of Rh occurs. On reduced ceria, XPS indicates a possible electron transfer from Rh to ceria. The formation of smaller ceria crystallites upon loading with Co was concluded from XRD and HRTEM; for 10% Co, the CeO 2 particle size decreased from 27.6 to 10.7 nm. A strong dissolution of Co into ceria and a certain extent of encapsulation by ceria were deduced by XRD, XPS and LEIS. In the bimetallic system, the presence of Rh enhances the reduction of cobalt and ceria.During thermal treatments, reoxidation of Co occurs, and Rh agglomeration as well as oxygen migration from ceria to Rh are hindered in the presence of cobalt.
Kinetics of the CO oxidation reaction on Pt(111) studied by in situ high-resolution x-ray photoelectron spectroscopy J. Chem. Phys. 120, 7113 (2004) The oxidation of CO on Pt(111) was investigated simultaneously by near ambient pressure X-ray photoelectron spectroscopy and online gas analysis. Different CO:O 2 reaction mixtures at total pressures of up to 1 mbar were used in continuous flow mode to obtain an understanding of the surface chemistry. By temperature-programmed and by isothermal measurements, the onset temperature of the reaction was determined for the different reactant mixtures. Highest turnover frequencies were found for the stoichiometric mixture. At elevated temperatures, the reaction becomes diffusionlimited in both temperature-programmed and isothermal measurements. In the highly active regime, no adsorbates were detected on the surface; it is therefore concluded that the catalyst surface is in a metallic state, within the detection limits of the experiment, under the applied conditions. Minor bulk impurities such as silicon were observed to influence the reaction up to total inhibition by formation of non-platinum oxides. C 2016 AIP Publishing LLC.[http://dx
Rh films of 5−50 monolayers (ML) were grown on TiO 2 (110)−(1 × 1) surface by physical 8 vapor deposition (PVD) at 300 K followed by annealing at max. 1050 K. In the coverage range of 5−15 ML,
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.