Photocatalytic activity of Zn²⁺ doped TiO₂ based on Chinese fir template

  Objective  In view of the waste of processing residues in wood processing industry, Zn²⁺ doped TiO₂ composite photocatalyst with hierarchical porous structure of wood was prepared by impregnation calcination method. Chinese fir was used as template to improve the photocatalytic performance.

  Method  Taking methylene blue solution as the target degradation object, the effects of different concentrations of Zn²⁺ doping on the photocatalytic activity of wood template TiO₂ were discussed. The photocatalytic degradation mechanism of wood template TiO₂ was analyzed by XRD, SEM, XPS, BET, TEM and UV-Vis.

  Result  The Zn²⁺ doped wood template TiO₂ presents good pore structure that hierarches from wood. It is a mixed crystal structure of anatase and rutile TiO₂. The average grain size was 22.0 nm. The Zn²⁺ replaced the lattice position of Ti⁴⁺, which made the absorption wavelength of TiO₂ presenting red shift in the visible region. Under UV irradiation, the degradation efficiency of methylene blue solution with 1.0% Zn-TiO₂ reached 99.31%. Compared with the TiO₂ without template, its degradation efficiency increased by 27%. Compared with the templated TiO₂, the band gap decreased from 3.08 to 2.41 ev. The degradation efficiency can be retained 90% after five repeated experiments.

  Conclusion  Zn²⁺ doped TiO₂ prepared with wood template shows excellent photocatalytic degradation performance and stability. The unique pore structure is conducive to light absorption and mass transfer, and the higher specific surface area provides more active sites for photocatalysis. Due to the difference of radius and valence state between Zn²⁺ and Ti⁴⁺, lattice defects will appear in the lattice, which can inhibit the recombination of photogenerated electrons and holes, increase the carrier transport and improve the photocatalytic performance. Thus, wood residues utilization with functional inorganic materials can present a promising prospect in industrial applicaion.