Binary CoOx–SiO2 Porous Nanostructures for Catalytic CO Oxidation

Via integrative chemistry, the first CoOx–SiO2(HIPE) self-standing monoliths of cobalt nano-oxides embedded within silica macro–mesocellular hosts have been prepared. These binary CoOx–SiO2 porous nanostructure (MUB-100(x)) materials present an average of 95% porosity. We found out that high cobalt concentration maintains the hexagonal-2D organization of the mesoscopic voids when applying the thermal treatment at 700 °C. Their specific surface areas fall between 400 and 500 m2 g–1 when assessed by Ar physisorption measurements. At the microscopic length scale, as revealed through magnetic investigations, the low cobalt content foams MUB-100(1) and MUB-100(2) are made of the amorphous β-Co(OH)2 phase coexisting with the silica network, whereas increasing the cobalt concentration during the one-pot syntheses (MUB-100(3) and MUB-(4) materials) favors the formation of the spinel Co3O4 and olivine Co2SiO4 crystalline nanoparticles embedded within silica. When considering the CO oxidation catalytic performance, the MUB-100(4) is able to totally convert the CO flow before 200 °C (starting at 125 °C) while achieving 50% conversion for a light-off temperature (T50) of 145 °C, revealing the good efficiency of the MUB-100(4) in CO oxidation with which up to 4 catalytic cycles have been performed without disrupting drastically the catalytic performance and reaching thermodynamic stability from cycle 2 to cycle 4.