DFT study on CO oxidative coupling to DMO over Pd4/TiO2 and Pd4/TiO2-Ov: A role of oxygen vacancy on support

The reaction mechanisms for CO oxidative coupling to DMO on Pd-4 supported on TiO2(0 0 1) catalysts were studied by using the density functional theory calculations with a Hubbard U correction (DFT + U). Two different supports including perfect TiO2(0 01) and oxygen vacancy TiO2(0 01) were investigated. The interaction between Pd-4 and supports showed that the binding energy of Pd-4 cluster with oxygen vacancy TiO2(0 01) was stronger than that with the perfect TiO2(0 0 1), and the relatively weak adsorption energy of CO was obtained on Pd-4/TiO2-O-v, implied that it was easier for CO removing and reacting. In addition, reaction mechanisms of CO oxidative coupling to DMO on Pd-4/TiO2 and Pd-4/TiO2-O-v were studied, and the Pd-4/TiO2-O-v catalyst showed higher activity than Pd-4/TiO2. Moreover, compared with Pd(1 1 1), Pd-4/TiO2-O-v not only reduced the amount of Pd, but also improved the activity of CO oxidative coupling to DMO. However, DMO and DMC were competitive products on Pd-4/TiO2 and Pd-4/TiO2-O-v, showed that they were with poor selectivity to DMO.