Formation, composition, structure, and catalytic activity in CO oxidation of SiO2+ TiO2/Ti composite before and after modification by MnOx or CoOx

The composition and structure of SiO2 +TiO2 oxide layers formed on titanium by plasma electrolytic oxidation (PEO) and MOx(M=Co or Mn)+SiO2 +TiO2/Ti composites fabricated on their basis using impregnation and annealing methods have been investigated. It has been demonstrated that silicon and titanium are rather homogeneously distributed within the SiO2 +TiO2 coating bulk. In the galvanostatic process mode, the titanium/silicon ratio in the coating bulk can be controlled by the current density value. The coating outer part is silicon-enriched and titanium-depleted. The MnOx +SiO2 +TiO2/Ti composites catalyze the CO oxidation into CO2 at temperatures above 100 degree C, whereas the CoOx +SiO2 +TiO2/Ti composites do the same above 200 degree C. Nanosized particles have been found on the surface of the composites under study: for CoOx +SiO2 +TiO2/Ti - granules of a diameter of a few dozen nm; for MnOx +SiO2 +TiO2/Ti - nanowhiskers consisting predominantly of manganese oxides. The obtained oxide catalysts are promising for testing as catalysts of redox reactions, including titanium-based microreactors.