Influence of Ti doping level on hydrogen adsorption of mesoporous Ti-SBA-15 materials prepared by direct synthesis

Abstract

The influence of different Ti doping levels on the hydrogen adsorption characteristics of Ti-SBA-15 materials prepared by direct one-step synthesis was systematically investigated. The results showed that the intensity of titanol (Ti-OH) and bridging hydroxyl (Ti-O(H)-Si) groups increased with increasing Ti doping level, whereas the hydrogen adsorption capacity gradually decreased. Nitrogen physisorption, transmission electron microscopy, and small and wide-angle X-ray diffraction analyses revealed that excessive Ti doping led to the growth of TiO2 nanoparticles on the intrawall of the mesopores, which clogged the micropores. However, at comparatively low Ti doping level, Ti substitution and/or dispersion in the silica framework was activated, the number of micropores increased, and consequently the hydrogen adsorption capacity was substantially enhanced. The results from this study suggested that the hydrogen adsorption characteristics of Ti-SBA-15 materials prepared by the direct synthesis method were affected not only by generated titanol and bridging hydroxyl groups but also by the increased number of micropores.