Photocatalytic enhancement of TiO₂ by B and Zr co-doping and modulation of microstructure

Graphical abstract: B and Zr codoped sample was prepared by a sol–gel method, which exhibits the best photocatalytic performance on degradation of methylene blue solution under a simulated solar light source in comparison with undoped and singly doped TiO₂ nanocrystals. The enhancement was tentatively attributed to: (1) The incorporation of interstitial boron dopants creates oxygen vacancies (Ov··) and reduce Ti⁴⁺ to Ti³⁺ to form [Ov··-Ti³⁺]⁺, which traps the carriers and prolongs carrier lifetime; (2) Zr⁴⁺ ions replace Ti⁴⁺ ions and form impurity levels, which could improve visible light response, and (3) reduction of average crystallite size. - Highlights: • B and Zr co-doping can effectively improve the visible-light photocatalytic activity of TiO₂ by more than twice. • XRD, Raman, and XPS measurements demonstrated that all the samples are anatase phase of TiO₂ and Zr⁴⁺ ions replace the Ti⁴⁺ ions while the B³⁺ ions occupy the interstitial sites. • The incorporation of interstitial boron dopants creates oxygen vacancies (Ov··) and reduce Ti⁴⁺ to Ti³⁺ to form [Ov··-Ti³⁺]⁺, which traps the carriers and prolongs carrier lifetime. • Zr⁴⁺ ions replace Ti⁴⁺ ions and form impurity levels, which could improve visible light response. • The co-doped samples are benefited from both B interstitials and Zr substitutes. - Abstract: Visible-light photodegradation test revealed that B and Zr co-doping can raise the photocatalytic ability of the undoped TiO₂ by a fold. XRD crystallography and Raman phonon spectroscopy measurements suggest that the Zr⁴⁺ ions replace the Ti⁴⁺ ions while the B³⁺ ions occupy the interstitial sites, expanding the unit-cell volume and reducing crystallite size. The incorporation of interstitial boron dopants creates oxygen vacancies (Ov··) and reduce Ti⁴⁺ to Ti³⁺ to form [Ov··-Ti³⁺]⁺, which traps the carriers and prolongs carrier lifetime. Moreover, Zr⁴⁺ ions replace Ti⁴⁺ ions and form impurity levels, which could improve visible light response. The co-doped samples are benefited from both B interstitials and Zr substitutes.