Rational Design of Original Materials for the Electrocatalytic Hydrogenation Reactions:  Concept, Preparation, Characterization, and Theoretical Analysis

Abstract

Original and versatile new materials for the electrocatalytic hydrogenation of organic compounds were designed. The materials consist of reticulated glassy carbon cathode electrodes in which the modified silica particles (average diameter 40-63 microm) were dynamically circulated. The modification of the silica surface is 2-fold. First, the silica is surface-modified using organic functions such as -OSi(CH3)2(CH2)3OCH2CH-(OH)(CH)2OH (SiO2-Diol), -OSi(CH3)2(CH2)7CH3 (SiO2-C8), and -OSi(CH3)2C6H5 (SiO2-Phenyl). Second, these silica particles were further modified by vapor phase deposition of nickel nanoaggregates (used as sites for hydrogen atoms and electric contacts with the electrode material), which does not destroy or alter the organic functionalization as demonstrated by thermogravimetric analysis-mass spectrometry and Raman, diffuse reflectance IR Fourier transform, and Auger electron spectroscopies. The new concept stems from relative adsorption and desorption properties of the organic molecules and their corresponding reduced products into the organic functionalization of the surface-modified silica. In this work, the electrocatalytic hydrogenation cyclohexanone was used to test the concept. The performances (amount of cyclohexanol vs time of generated electrolysis at constant current) are measured and compared for the various bonded organic functions of the silica surface listed above, along with the unmodified silica particles (but still containing nickel nanoaggregates) and the presence or absence of methanol in solution. The measurements of the adsorption isotherms of cyclohexanone, and the calculations of the interaction energies (MM3 force field) between the chemisorbed organic functions and the substrates, corroborate perfectly the electrocatalysis results.

Synthesis and characterization of partially fluorinated aerogels and xerogels from environmentally-compatible precursors

“…Within the TEOS only aerogels and xerogels, there is an additional mass loss event that occurs above 250 C and is assigned to the loss of physisorbed water and the dehydration of free silanol sites. 22,23 If the overall mass loss for the aerogel and xerogel samples are corrected for the adsorbed volatile species, unreacted silanol sites, and the percent of the degradable component of 2 is taken into account ($80%), then the overall mass losses for the aerogel and xerogel samples fall within range of what one might expect for each sample. For example, the expected mass loss for the 20, 30, 50, and 100 mol% samples would be 54, 64, 78, and 94%, respectively.…”

High temperature stability of n-decanethiol by adsorption on nickel powders used as reforming catalysts in solid oxide fuel cells (SOFC)

“…The change recorded during the heating shows that the molecules adsorbed on silica were dissociated at a temperature lower than 700°C. Saint-Pierre et al [29] performed the TGA-MS method to determine the temperature stability of the organic phase bonded at the surface of silica particles (SiO 2 -C 8 ) and reported the decomposition commencing at 200°C.…”

Degradation of Reactive Black 5 and Basic Yellow 28 on Metallic-Polymer Composites

“…Since at high cathodic potentials chemisorbed hydrogen is generated at the Ni-PVC electrode surface by electrolysis of water, we considered the possibility of achieving the decolorization by a cathodic electron transfer according to the reactions 1 and 2 and by ECH. The decolorization achieved by electron transfer and by ECH of azo dyes has already been described [38][39][40][41][42][43][44][45][46][47]. In the case of decolorization by ECH, we considered that the active hydrogen species can lead to the rupture of azo-bonds accompanied by an adsorption step [29, 39-41, 43, 44, 47].…”