Visible-light-driven photocatalytic performance of nitrogen-doped Ti1−xZrxO2 solid solution

Nitrogen-doped Ti1−xZrxO2 solid solutions have been synthesized by a multi-step sol–gel process followed by hydrothermal treatment in ammonia solution. XRD, XPS and UV–vis diffuse reflectance analyses indicated that nitrogen was doped in the surface layer of catalyst, introducing surface states located close to valence band. However, Zr4+ was successfully incorporated into the bulk lattice of TiO2 so as to induce the up-shift of conduction band. Compared to pristine TiO2 and nitrogen-doped TiO2, nitrogen-doped Ti1−xZrxO2 exhibited much higher efficiency for the degradation of Acid Red 88 solution and gaseous benzene under visible light irradiation, attributed to the synergetic effect of nitrogen and zirconium on the energy band. Specifically, the presence of surface states in the band gap enabled the extended visible light response and the up-shift of conduction band facilitated the excited electron interfacial transfer and hence suppressed efficiently the recombination of charge carriers.