The Preparation And Properties Of N-Fe₂O₃/p-CaFe₂O₄ Heterojunction Photocatalyst

Semiconductor photocatalyst is expected as highly promising strategy fir both harvesting solar energy and decomposing toxic origanics in water by soalr light irradiation.However,the low quantum efficiency and high recombination of photogenerated electron-hole limits the technology breakthrough in this area.Therefore,to design and develop highly efficient photocatalyts has become the focus of current research.a-Fe2O3 has a proper band gap of about 2.1 eV which lies in the visible region of solar spectrum.Together with the environmental compatibility and low cost,a-Fe2O3 in consider as good candidate for visible light photocatalyst.In recent years,accelerating the separation of the electrons and holes by constructing the N-semidonductor/P-semiconductor heterojunction has received lots of attention.In this study,we focus on the solution of the main drawbacks of a-Fe2O3 such as the short lifetime of photogenrated carriars and short depath of holes,we prepared n-Fe2O3/p-CaFe2O4 heterojunction photocatalitic nanomaterial by controllable in-situ growth methods.The main contents were discussed as follows.1、1D a-Fe2O3 nanofibers were fabricated by an electrospinning method followed by a calcination in air at 600℃ progress.The a-Fe2O3 nanofibers exhibit higher photocatalytic activity than the commercial a-Fe2O3 powders for the degradation of MO under visible light illumination.More than 90%of MO was degradated after 40min.And the kinetic rate constant of a-Fe2O3 nanofibers for the photocatalytic degradation of MO was 5 times larger than commercial a-Fe2O3 powder.The photocurrent density of a-FR2O3 nanofibers was 12 times higher than commercial a-Fe2O3 powders.The enhancement of the photocatalytic activity of a-Fe2O3 nanofibers can be ascribed to their larger surface area,improved light absorption property and the reduced recombination of the photoexcited electrons and holes.2、In order to avoid the problem of large particle size of CaFe2O4 synthesized by traditional solid-state reaction method,a small size CaFe2O4 nanofibers with a diameter of 130 nm were fabricated by electrospinnng method.The main factor of the fabrications of CaFe2O4 nanofibers was discussed.And then the photocatalytic activity for the degradation of MO and the photoelectrochemical performance under visible light illumination were investigated.The result shows that the CaFe2O4 nanofibers only can be fabricated under the condition of stoichiometric ratio of Fe/Ca and the heat treat temperature of 800℃.CaFe2O4 nanofibers show higher photocatalytic activity than CaFe2O4 bulk fabricated by traditional method under visible light illumination.3、n-Fe2O3/p-CaFe2O4 heterojunction photocatalitic nanofibers were fabricated by in-situ growth method.The as prepared sample is composed of α-Fe2O3 nanoparticles growing on the primary CaFe2O4 nanofibers.The influence of reaction time,and the probably mechanism of the in-situ growth was discussed.The results indicate that the n-Fe2O3/p-CaFe2O4 heterojunction photocatalitic nanofibers exhibit much higher photocatalysis activity than pure CaFe2O4 nanofibers.And the heterojunction as prepared by 40min under 150℃ shows the highest photocatalysis activity,the photocurrent density of n-Fe2O3/p-CaFe2O4 heterojunction was increased 22.9%than pure CaFe2O4 nanofibers.4、n-Fe2O3/p-CaFe2O4 film heterojunction photocatalitic was fabricated by combining the hydrothermal process and electrophoresis deposition method.The onset potential of n-Fe2O3/p-CaFe2O4 film heterojunction shift neatly by 0.31V for Fe2O3 film.