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.