Formation and structure of Au/TiO2 and Au/CeO2 nanostructures in mesoporous SBA-15

The catalytic activity of gold nanoparticles deposited on the SBA-15 and modified by various oxide promoters has been investigated. 5 wt.% TiO2 was introduced into SBA-15 (sample denoted by TiSBA). Gold using HAuCl4 precursor was deposited (i) by deposition–precipitation (DP) (AuTiSBA_DP), (ii) by adsorption of Au colloid previously prepared by NaBH4 reduction, and stabilized by polyvinylalcohol (PVA) (AuTiSBA_PVA) and (iii) by NaBH4 reduction of Au precursor in the presence of poly(diallyldimethylammonium) chloride (PDDA) in the suspension of the support (AuTiSBA_PDDA). Au/5 wt.% TiO2/SiO2 reference sample (AuTiSiO2_DP) was prepared using high surface area amorphous silica by similar TiO2 introduction and DP of Au. The Au/SBA-15 references (AuSBA_PVA, AuSBA_PDDA) were made by gold deposition type (ii) and (iii) on SBA-15. 5 wt.% TiO2 and 10 wt.% CeO2 containing SBA-15 supported gold were prepared via impregnation of AuSBA_PVA by Ti(IV) bis(ammoniumlactato)dihydroxide (TALH) and Ce(NO3)3 solutions (AuSBA_PVA_Ti, AuSBA_PVA_Ce), respectively. All the samples were calcined before catalytic measurements and were characterized by BET technique, transmission electron microscopy (TEM) with EDS and X-ray diffraction (XRD). The activity sequence in the CO oxidation was AuSBA_PVA_Ce > AuTiSBA_DP > AuTiSBA_PVA > AuSBA_PVA_Ti ≈ AuSBA_PVA > AuTiSiO2_DP > AuTiSBA_PDDA > AuSBA_PDDA. The activity is strongly affected by gold/oxide interface (the length of Au-TiO2 and Au-CeO2 perimeter), which emerged during the preparation and discussed in terms of the surface charges of the components. The Au nanoparticles in the SBA-15 could be stabilized more efficiently than those on amorphous silica.