Synergistic Role of B and F Dopants in Promoting the Photocatalytic Activity of Rutile TiO2

Herein, we synthesize B,F-doped TiO2 powders and elucidate for the first time the nature of active centers responsible for the catalytic activity of rutile TiO2, even when a very low surface area is present. In particular, we used electron paramagnetic resonance (EPR) for a thorough characterization of catalytically active sites. Since during TiO2 synthesis the presence of B or F dopants induces the low-temperature formation of a mixture of anatase, rutile, brookite polymorphs, the attention was focused on high-temperature-treated materials, containing the pure rutile phase and possessing a negligible surface area. This work demonstrates that a suitable synthetic design can transform even a “stone” with insignificant surface area into a very efficient photocatalyst. Specifically, herein we show the existence of a critical synergic interaction between B and F codopants in rutile titania that weakly enhances Vis-light absorption but, notably, generates active photocatalytic sites. We show that concomitant surface/second layer B and surface F are needed to get a significant MO degradation. The present investigation reveals that dopant distribution in the active material is of key importance and must be carefully considered in tailoring material properties. The simplicity of our preparation synthesis is a significant advantage in view of large-scale applications.