Generation of basic sites on TiO 2 by reduction with H 2

Abstract

The generation of basic sites on a TiO 2 surface by reduction is discussed on the basis of the results of catalytic reactions, temperature-programmed desorption of adsorbed CO 2, and measurements of the numbers of surface hydrogen acceptors and donors (DPPH 2 and DPPH methods). The results of catalytic reactions show that both acidic and basic active sites are present on TiO 2 surfaces and reduction of TiO 2 increases its basic character. The TPD profile of adsorbed CO 2 suggests that basic sites increase following the reduction of TiO 2 but their strengths are not high. Reduction of TiO 2 not only suppresses the surface acidity but also increases the number of surface proton acceptors. This is also supported by DPPH-DPPH 2 experiments. These results lead to the conclusion that basic sites generated by the reduction of TiO 2 are surface oxygen species which can abstract protons from adsorbed species.