Controlling the CO oxidation rate over Pt/TiO2 catalysts by defect engineering of the TiO2 support

Defect engineering of the TiO2 anatase support controls the CO oxidation rate over a Pt/TiO2 catalyst. DFT calculations show that increased charge transfer decreases the CO adsorption energy, consistent with the rate measurements. [Display omitted] •Pt CO oxidation activity is manipulated by controlling TiO2 support properties (Schwab effect).•TiO2 thin films with an order of magnitude variation in carrier concentration were prepared.•Variation in TiO2 carrier concentration influences electronic properties of Pt clusters.•DFT shows that charge injection reduces CO adsorption enthalpy on Pt by Pauli repulsion.•Variation in measured activity is consistent with changes in calculated CO adsorption enthalpy. The activity and selectivity of supported metal clusters can in principle be manipulated by controlling the electronic properties of the support, as initially proposed by Schwab. To quantitatively demonstrate this effect, a series of anatase TiO2 thin films with an order of magnitude variation in the carrier concentration were grown by atomic layer deposition. The change in the TiO2 carrier concentration influences the electronic properties of supported Pt clusters, as shown by photoelectron spectroscopy. The gradual increase in the carrier concentration increases the CO oxidation rate over the Pt/TiO2 catalysts by 70% for excess CO conditions and decreases the rate by 30% for excess O2 conditions, providing a quantitative connection between the support properties and the measured reaction rate. Density functional theory calculations and natural bond analysis show that charge injection into Pt clusters reduces the CO adsorption energy due to increased Pauli repulsion, which is consistent with the observed changes in the reaction rate.