N-2 AND H2O ADSORPTION ON COMBINATIONS OF TIO2 AND FE2O3

Simple experiments aimed at uncovering any changes in adsorption properties as Fe2O3 is added to TiO2-based photocatalysts show that the Fe2O3 additions do very little to the N2 and H2O adsorption until the Fe2O3 content becomes higher than 80 wt % . Above 80 wt % Fe2O3, the amount of strongly adsorbed water begins to increase and it blocks the strong N2 physisorption. Strongly adsorbed water on surfaces of materials that are less than 80 wt % Fe2O3 haa virtually no influence on N2 physisorption. X-ray photoelectron spectroscopic (XPS) analysis indicates that the surfaces do not become rich in Fe until the bulk Fe2O3 concentration goes above 80 wt %. The tendency for the surface to remain rich in TiO2 prevents significant adsorption changes from occurring as the Fe2O3 increases from low to moderate levels. Hence, the changes in photocatalytic properties that, have been reported for TiO2 doped with Fe2O3 are not expected to stem from gross changes in adsorptive properties.