Enhanced photocatalytic properties due to electron-rich Ti-ion Doping in ZnFe₂O₄ under visible light irradiation

The substitution effect of Ti⁴⁺ at the Fe³⁺ site in the spinel-phase ZnFe₂O₄ system has been studied and further optimized to fabricate an efficient photocatalyst. The material doped with an electron donor (Ti⁺⁴), ZnFe_2-xTi_xO₄, with an optimum composition of x = 0.06 exhibited a unchanged band gap, which generated two times higher photocurrent and showed an enhanced quantum yield (upto 0.77%) for photodecomposition of a H₂O-CH₃OH mixture compared to the undoped material under a visible light (λ ≥ 420 nm). In contrast, the material doped with very high concentration of Ti revealed deteriorated photochemical properties due to constituent impurity phases. The higher electron density caused by n-type doping seemed to be responsible for the more efficient charge separation in ZnFe_2-xTi_xO₄ (0.01 < x < 0.09), and hence, the high photocatalytic activity.