Barium, calcium and magnesium doped mesoporous ceria supported gold nanoparticle for benzyl alcohol oxidation using molecular O2

In the era of sustainable energy, catalysis using gold nanoparticles has drawn considerable attention from
world researchers. Oxidation of benzyl alcohol by molecular O2 is an atom efficient path to synthesize
benzaldehyde. Nanocrystalline ceria has been proven as a useful support to disperse gold nanoparticles
since last few years, however there are a few reports on mesoporous ceria supported gold nanoparticles.
In this work a systematic investigation was carried out to improve the activity of Au/CeO2 catalyst by
incorporating Ba2+, Ca2+ and Mg2+ cations into the ceria lattice through a sol–gel procedure. Both the
doped ceria and ceria supported gold nanoparticles are characterized by BET S.A, XRD, TEM, SAXS, XPS,
TPR, CO2-TPD techniques. BET S.A measurements show the mesoporous oxides where H3 hysteresis loops
are found. The decrease in the crystallite size of ceria after doping by metal cations is observed in the
XRD measurement. The TEM and HRTEM characterization shows the nanocrystalline particle size around
30–50 nm and gold nanoparticles around 10–15 nm in size. Distribution in the particle size for doped
ceria have been obtained using SAXS measurements where narrow distributions of ceria particles are
found in the 10–20 nm range. The existence of oxide vacancies and the mixture of Ce3+/Ce4+ oxidation
states are observed for doped ceria materials in the XPS investigation. The strong gold-support interaction
was also evidenced by XPS characterization where oxidic gold was found on the doped ceria surface.
Lowering of the reduction peak in ceria after gold nanoparticle deposition was observed from TPR
investigation whereas the change in basic site distribution is observed from CO2 TPD experiment,
instigating new insights into the surface properties of the catalysts. The catalytic activities of the catalysts
were determined for benzyl alcohol oxidation reactions using molecular O2. The catalytic activity was in
the order of Au/Ba–CeO2 4 Au/Ca–CeO2 4 Au/Mg–CeO2 4 Au/CeO2. The synergistic effect of gold
nanoparticles and dopant cations to the ceria was explained in this work.