Effects of Elemental Chemical State in NiFe₂O₄@TiO₂ on the Photocatalytic Performance

Abstract

The elemental chemical state of NiFe₂O₄@TiO₂ was changed by the reduction in order to investigate its effects on the photocatalytic performance. The synthesized NiFe₂O₄@TiO₂ samples were characterized by means of X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), magnetic and photocatalytic measurements. Unexpectedly, the reduction reaction does not produce oxygen vacancies O _v and TiO _x in the TiO₂ lattice. The optimal catalyst was obtained at the reducing temperature of 800 °C, and its degradation efficiency D _e to the methylene blue and reaction rate constant K _app are the highest, reaching 99.9% and 3×10⁻² min⁻¹, respectively. The reason could not be explained by both the visible light absorption and the appropriate amount of O _v and TiO _x. Instead, the lowest ratios of TiOH and Ti-O-Fe(Ni) may be responsible for the optimum photocatalytic performance.

Keywords

photocatalyst / TiO₂ / self-doping / NiFe₂O₄ / photocatalytic performance

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