Chemisorption

About: Chemisorption is a research topic. Over the lifetime, 16298 publications have been published within this topic receiving 554989 citations.

Dependence of metal cluster reaction kinetics on charge state. I. Reaction of neutral (Nbx) and ionic (Nb+x, Nb−x) niobium clusters with D2

Abstract: The effect of charge state on niobium cluster chemisorption kinetics is explored via measurement of the relative rates of D2 activation by Nb−x, Nbx, and Nb+x containing up to 28 atoms. The presence of the + or − charge is found to have only a minor effect on rate for the majority of the clusters, with the reactivity of the ions being generally within a factor of 2.5 of the corresponding neutrals. The excess charge does, however, have a profund influence on reaction rate for a number of clusters in the 7≤x≤16 size range, which may be indicative of the importance of cluster electronic structure in the chemisorption process. Kinetic data for Nb9, Nb12, and Nb+12 are found to deviate significantly from the expected pseudo‐first‐order behavior, suggesting the existence of structural isomers for these species. The anomalous behavior for Nb9 and Nb12 was not observed in previous neutral Nbx chemisorption studies. The maximum uptake of D2 by niobium clusters is found to be essentially independent of charge state...

Surface Characterization of Nanoscale TiO2 Film by Sum Frequency Generation Using Methanol as a Molecular Probe

Abstract: Sum frequency generation (SFG) vibrational spectroscopy is applied to study the surface characteristics of a film composed of nanoscale TiO2 particles, in which methanol is employed as a molecular probe. The SFG signal from methanol adsorbed on the TiO2 film surface in the CH region consists of four primary peaks located at 2828, 2855, 2935, and 2968 cm-1. The peaks at 2855 and 2968 cm-1 arise from molecular methanol; the other two are attributed to methoxy produced by dissociative chemisorption of methanol on TiO2. Changes in the SFG features with methanol pressure and with surface temperature provide the first direct proof of methoxy generation on nanoparticulate films. In comparison with molecular methanol, methoxy sits more perpendicularly on the surface. The chemisorption is barrierless, and a Langmuir constant of (2.13 ± 0.14) × 103 is derived from the adsorption isotherm. Moreover, UV pretreatment of the TiO2 film substantially increases the methoxy signal. Changes in SFG intensity are in good agre...

Spatially Resolved Raman Spectroscopy of Carbon Electrode Surfaces: Observations of Structural and Chemical Heterogeneity

Abstract: Raman spectroscopy and Raman imaging were used to examine several types of carbon electrode materials, including glassy carbon (GC) and highly ordered pyrolytic graphite (HOPG). Variations in the intensity ratio of the D and E2g Raman bands across the carbon surface indicated varying carbon microstructure. The D/E2g ratio for polished GC and pyrolytic graphite edge (PG) was relatively constant, while that of basal HOPG and PG varied significantly due to defects. The spatial heterogeneity of Rhodamine 6G Raman intensity following physisorption to carbon surfaces indicated that adsorption occurs at disordered regions, particularly defects on HOPG. This observation provides visual confirmation of previously reported correlations of defect area and physisorption. Chemisorption of dinitrophenylhydrazine was observed only at edge plane regions, confirming the localization of surface carbonyl groups on graphitic edge plane. Finally, chemisorption of nitroazobenzene radical formed from a diazonium precursor occur...