A simple strategy to improve Pd dispersion and enhance Pd/TiO2 catalytic activity for formaldehyde oxidation: The roles of surface defects

Highly dispersed precious metals are critical to many important catalytic reactions and strongly affect the activity of catalysts. In this work, a simple method to stabilize noble metals on Pd/TiO2 catalyst by constructing Ti3+ defects on the surface of TiO2 supports. The TiO2 samples with different contents of Ti3+ defects were used to prepare a series of Pd/TiO2 catalysts, which were tested in formaldehyde (HCHO) oxidation. Multiple characterization results illustrated that the Ti3+ defects on TiO2 produced by hydrogen pretreatment during high temperature reduction (HTR), favored the stabilization of Pd particles through the strong metal-support interaction (SMSI). The increasing Pd dispersion induced more oxygen vacancies on the surfaces of Pd/TiO2 catalysts, because of hydrogen spillover, and further increased the electron density of Pd species. The activation of water and oxygen was also promoted to form more surface oxygen species. Therefore, the more surface defects existing, the better performance of Pd/TiO2 catalysts displayed for HCHO oxidation.