Abstract
Ultrafine ruthenium nanoparticles (NPs) within the mesopores of the SBA-15 have been successfully prepared by using a “double solvents” method, in which n-hexane is used as a hydrophobic solvent and RuCl3 aqueous solution is used as a hydrophilic solvent. After the impregnation and reduction processes, the samples were characterized by XRD, TEM, EDX, XPS, N2 adsorption-desorption, and ICP techniques. The TEM images show that small sized Ru NPs with an average size of 3.0 ± 0.8 nm are uniformly dispersed in the mesopores of SBA-15. The as-synthesized Ru@SBA-15 nanocomposites (NCs) display exceptional catalytic activity for hydrogen generation by the hydrolysis of ammonia borane (NH3BH3, AB) and hydrazine borane (N2H4BH3, HB) at room temperature with the turnover frequency (TOF) value of 316 and 706 mol H2 (mol Ru min)−1, respectively, relatively high values reported so far for the same reaction. The activation energies (Ea) for the hydrolysis of AB and HB catalyzed by Ru@SBA-15 NCs are measured to be 34.8 ± 2 and 41.3 ± 2 kJ mol−1, respectively. Moreover, Ru@SBA-15 NCs also show satisfied durable stability for the hydrolytic dehydrogenation of AB and HB, respectively.
Highlights
A lot of metal nanocatalysts have been tested for hydrogen generation from the hydrolysis of AB and HB22–33, among which platinum group metals including Pt, Rh, and Ru based catalysts display a remarkable performance in hydrogen production as compared to other catalysts even at a very low metal concentration[14,19,31,32,33]
Ultrafine Ru NPs within the pores of the mesoporous SBA-15 were prepared via a double solvents technique, in which n-hexane is used as a hydrophobic solvent to suspend SBA-15 and RuCl3 aqueous solution is used as a hydrophilic solvent to fill mesopores
After the impregnation and reduction processes, the obtained Ru@SBA-15 NCs were isolated from the reaction solution by centrifugation and characterized by X-ray diffraction (XRD), SEM, transmission electron microscopy (TEM), energy-dispersive X-ray detector (EDX), and X-ray photoelectron spectroscopy (XPS) techniques
Summary
A lot of metal nanocatalysts have been tested for hydrogen generation from the hydrolysis of AB and HB22–33, among which platinum group metals including Pt, Rh, and Ru based catalysts display a remarkable performance in hydrogen production as compared to other catalysts even at a very low metal concentration[14,19,31,32,33]. Compared to the conventional support materials such as zeolites[40], carbon black[41], Al2O342, SiO237, TiO243, MCM-4144, SBA-15 has a short history, which was firstly synthesized and reported by Zhao et al.[45]. It attracted rapid attention in materials science and catalysis, and has been emerged as a potential support for growing and anchoring metal NPs due to its ordered structure, narrow and controllable pore size and large specific surface area[46,47,48,49,50,51]. The kinetics of hydrolysis of AB and HB by Ru@SBA-15 NCs were studied under different catalyst concentrations, substrate concentrations, and reaction temperatures
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