Surface modification of Co3O4 nanocubes with TEOS for an improved performance in the Fischer-Tropsch synthesis

The surface of Co3O4 nano-cubes has been modified by adsorption of small amounts of tetraethoxysilane from a solution in n-hexane. The resulting silicate species on and near the Co3O4 surface have been characterized using XPS, FTIR and XANES, and may have formed neso or island silicates. The presence of these silicate species hinders the reduction of Co3O4. IR-visible bonds of some of the adsorbed species remain intact even after reduction in hydrogen at elevated temperatures. The intrinsic catalytic activity of the modified, reduced modified Co3O4 nano-cubes have been tested for their activity and selectivity in the Fischer-Tropsch synthesis under industrially relevant conditions. It is observed that the cobalt time yield increasing more than 7-fold by the presence of the silicate species on the surface. The increase in activity does not seem to correlate with a change in the resulting metal surface area.