Pt/Ga-SBA-15 composites synthesis and characterization

Abstract

Pt (0.5, 1 and 1.5 wt%) was impregnated by incipient wetness on SBA-15 and corresponding Ga-modified (3, 5, 10 and 20 wt%) composites. Gallium nitrate was incorporated directly during the mesoporous siliceous network synthesis. Materials were characterized by N2 physisorption, X-ray diffraction, Fourier transformed infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. SBA-15 had surface area greater than 800 m²/g that decreased by Ga incorporation in binary materials. It seemed that tetrahedral gallium was well-incorporated into mesoporous silica walls. Pt dispersion slightly diminished (as to that on SBA-15) by augmenting Ga concentration in composites. Corresponding pore size maxima shifted to lower diameters (as to that of non-impregnated supports) after platinum loading suggesting Pt crystals inside pores of SBA-15 and Ga-modified carriers. Large cubic platinum crystals were observed over all prepared materials probably due to sintering (during calcining at 500 °C) of metallic particles weakly interacting with the carriers surface. After materials annealing (500 °C under static air) metallic platinum was evidenced (by XRD) pointing out to noble metal reduction that could be facilitated by decomposition of organic remains from Si alkoxide used during supports synthesis which presence was ascertained by FTIR.

La-Modified SBA-15 Prepared by Direct Synthesis: Importance of Determining Actual Composition

“…In any case, all impregnated solids had well defined peaks, pointing out sintering due to weak interaction with carriers. Determined crystal sizes (Table 2) were rather similar to those observed over catalysts supported on SBA-15 modified by various Ga contents and at similar NM loading [13]. Pt autoreduction could lead to crystals agglomeration in samples in weak interaction with the carrier [11].…”

Concentrated Platinum‐Gallium Nanoalloy for Hydrogen Production from the Catalytic Steam Reforming of Ethanol

“…No reflections related to Ga 2 O 3 defined domains were identified on any binary support pointing out the absence of defined gallium oxide crystals. Although the existence of well‐dispersed oxidic gallium domains (undetectable by XRD) could not be ruled out that fact suggested good integration of Ga 3+ species into the walls of mesoporous tetrahedral silicon oxide network [66,67] . According to the Scherrer formula and by using the most intense Pt (111) reflection corresponding crystal sizes for solids with MCF‐17 and Ga‐doped ones as carriers were estimated in Table 1.…”

Degradación fotocatalítica de los contaminantes 2-clorofenol y 4-clorofenol presentes en agua residuales empleando SBA-15 modificado con galio como fotocatalizador

“…Esto se debe a que, bajo tales condiciones fuertemente ácidas, los metales existen solo en la forma catiónica en lugar de sus correspondientes especies de oxo y, por lo tanto, los heteroátomos no pueden introducirse en las paredes mesoporosas a través de un proceso de condensación con especies de silicio. 77 Para la obtención de materiales mesoporosos modificados con galio son utilizados procedimientos de síntesis directa y síntesis directa con ajuste de pH en el gel de síntesis al final de la reacción o bien por métodos de deposición/inserción 78 . La estabilidad de los materiales permite mantener el ordenamiento hexagonal y sus propiedades físicas.…”