Shape-Controlled Pathways in the Hydrogen Production from Ethanol Steam Reforming over Ceria Nanoparticles.

The ethanol surface reaction over CeO2 nanooctahedra (NO) and nanocubes (NC), which mainly expose (111) and (100) surfaces, respectively, was studied by means of infrared spectroscopy (TPSR-IR), mass spectrometry (TPSR-MS), and density functional theory (DFT) calculations. TPSR-MS results show that the production of H2 is 2.4 times higher on CeO2-NC than on CeO2-NO, which is rationalized starting from the different types of adsorbed ethoxy species controlled by the shape of the ceria particles. Over the CeO2(111) surface, monodentate type I and II ethoxy species with the alkyl chain perpendicular or parallel to the surface, respectively, were identified. Meanwhile, on the CeO2(100) surface, bidentate and monodentate type III ethoxy species on the checkerboard O-terminated surface and on a pyramid of the reconstructed (100) surface, respectively, are found. The more labile surface ethoxy species on each ceria nanoshape, which are the monodentate type I or III ethoxy on CeO2-NO and CeO2-NC, respectively, react on the surface to give acetate species that decompose to CO2 and CH4, while H2 is formed via the recombination of hydroxyl species. In addition, the more stable monodentate type II and bidentate ethoxy species on CeO2-NO and CeO2-NC, respectively, give an ethylenedioxy intermediate, the binding of which is facet-dependent. On the (111) facet, the less strongly bound ethylenedioxy desorbs as ethylene, whereas on the (100) facet, the more strongly bound intermediate also produces CO2 and H2 via formate species. Thus, on the (100) facet, an additional pathway toward H2 formation is found. ESR activity measurements show an enhanced H2 production on the nanocubes.

PARAFAC and MCR-ALS applied to the quantitative monitoring of the photodegradation process of polycyclic aromatic hydrocarbons using three-dimensional excitation emission fluorescent spectra Comparative results with HPLC.

Two methods were developed for the simultaneous quantitative monitoring of photodegradation process of dibenz[a,h]anthracene (DibA), benz[a]anthracene (BaA), benz[a]pyrene (BaP) and benz[k]fluorantene (BkF) using excitation-emission fluorescence spectroscopy. Parallel factor analysis (PARAFAC) and multivariate curve resolution-alternating least squares (MCR-ALS) were satisfactory applied to the data obtained during this process. The results achieved were statistically compared by means of the joint interval test of slope and intercept, with the data obtained using the reference methodology, high performance liquid chromatography (HPLC) method. There are not significant differences between the methodologies proposed and the standard one, and may be a good alternative to the traditional methods of analysis for monitoring the degradation of these pollutants.