Atomic layer deposition on Pd nanocrystals for forming Pd-TiO2 interface toward enhanced CO oxidation

Pd typically exhibits relatively low catalytic activity in CO oxidation, as CO is apt to be adsorbed on Pd to poison the surface for O 2 activation. In this Letter, we report that this limitation can be overcome by integrating Pd with TiO 2 . The TiO 2 was coated on Pd nanocubes with a controllable thickness using atomic layer deposition (ALD) method. Given the different work functions of TiO 2 and Pd, the electrons in TiO 2 semiconductor will flow toward Pd. With the electron density increased on Pd, the adsorption of CO to Pd will be weakened while the oxygen activation can be facilitated. Meanwhile, the interface-confined sites at Pd-TiO 2 may further enhance the oxygen activation. As the species adsorption and activation are strongly correlated with electron density, the performance of Pd-TiO 2 in CO oxidation turns out to depend on the TiO 2 thickness, which determines the number of transferred electrons, within a certain range (<1.8   nm). This work provides a new strategy for enhancing catalytic performance through tailoring charge densities in hybrid catalysts.