Cu and Zr surface sites in photocatalytic activity of TiO$_{2}$ nanoparticles: the effect of Zr distribution

TiO$_{2}$ is the most studied photocatalyst for environmental application. The industrial scale application of TiO$_{2}$ is facing numerous problems andimmobilization of active and stable layers is among them. There is always a compromise between good mechanical stability and good photocatalytic activity ofimmobilyzed layers. Since zirconium oxide is claimed to have outstanding mechanical properties and in some cases causing the increase in catalytic activityof metal modified TiO$_{2}$., we have studied influence of Zr modification of TiO$_{2}$. and Cu modified TiO$_{2}$ photocatalysts, with the goal to improve their photocatalyticand mechanical properties.Copper/zirconium surface modified photocatalysts were prepared by modification of commercial titanium dioxide Aeroxide Degussa P25.Hardness test (Fig. 1) of active layers obtained from modified TiO$_{2}$ showed that Zr loading leads to improvement of mechanical properties compared to onlyCu modified samples. Microscopic investigation of copper modified powders (Fig. 4) showed formation of copper nanoclusters about 1-2 nm size on thesurface of TiO$_{2}$. EXAFS results (Figs. 5 and 6) suggest formation of separate ZrO$_2$ and CuO species attached to TiO$_{2}$ surface. The surface acidity titrationshowed, that Zr modification, leads to covering of all rutile acidic sites (Fig. 3). Thus, while combined Cu/Zr modification, Zr acts as a shield, covering rutilesurface, that results in preferably copper/anatase interaction. Thus, zirconium modification prevents formation of harmful copper/rutile interactions, whichappear at higher copper loading, and improves photocatalytic activity of combined Cu/Zr modified TiO$_{2}$ photocatalyst