Yi Ma,Pan Lv,Fang Duan,Jialiang Sheng,Shuanglong Lu,Han Zhu,Mingliang Du,Mingqing Chen
Reasonable design of heterojunctions is considered to be an effective way to construct highly efficient photocatalysts . In this work, Bi 2 S 3 /BiFeO 3 heterojunction nanofibers with tightly integrated interface were prepared by electrospinning technique and in-situ anion exchange method. Various characterizations were conducted to analyze the structure and morphology of Bi 2 S 3 /BiFeO 3 composites. The photocatalytic activities of the obtained Bi 2 S 3 /BiFeO 3 heterojunctions were evaluated by photodegradation of tetracycline hydrochloride (TC) under visible light irradiation. It can be found that Bi 2 S 3 /BiFeO 3 heterojunctions showed enhanced photocatalytic degradation performance, and their photocatalytic activities can be easily optimized by changing the amount of thioacetamide (TAA). When the amount of TAA was 0.1 mmol, the obtained Bi 2 S 3 /BiFeO 3 (TAA-2) sample exhibited the best photocatalytic performance, which was 5 and 6 times of pure BiFeO 3 and Bi 2 S 3 , respectively. Besides, the photocatalytic mechanism was systematically studied by monitoring the active species and radicals, and by performing the optical and photoelectrochemical tests. Accordingly, a direct Z-scheme charge migration mechanism for Bi 2 S 3 /BiFeO 3 heterojunctions was proposed. The enhanced photocatalytic performance of Bi 2 S 3 /BiFeO 3 heterojunctions can be attributed to the improved visible light response and efficient charge separation and transfer.
BiFeO 3 @carbon core/shell nanofibers (BFO@C NFs) with different thickness of carbon layers were successfully prepared by combining the electrospining technique and hydrothermal process. Scanning electron microscopy and transmission electron microscopy were employed to characterize the products. The results demonstrated that a uniform carbon layer was coated on the surface of BFO NFs. It was proposed that the introduction of carbon should not only enhance the light absorption of BFO NFs and the adsorption capacity for methyl orange, but also facilitate the separation of photogenerated electron–hole pairs, both of which result in the enhanced photocatalytic activity of BFO NFs. In addition, BFO@C NFs are stable under visible light irradiation and could be easily recycled, indicating that they can be used as effective photocatalysts under visible light.
Constituting solid solutions has been an appealing means to gain control over various physicochemical properties. In this work, we synthesized a series of SrTiO 3 -BiFeO 3 solid solutions and systematically explored their structural, optical and photocatalytic properties. Our results show that all solid solutions crystallize in a primitive cubic structure and their band gap values can be easily tuned by adjusting molar ratios between SrTiO 3 and BiFeO 3 . Photocatalytic hydrogen production under both full range and visible light irradiation is greatly improved after forming solid solutions. The highest hydrogen production rate obtained is ∼180 μmol/h under full range irradiation (λ ≥ 250 nm) and ∼4.2 μmol/h under visible light irradiation (λ ≥ 400 nm), corresponding to apparent quantum efficiency ∼2.28% and ∼0.10%, respectively. The activity is found to be strongly influenced by surface area and light absorption. Theoretical calculation suggests that Fe contributes to the formation of spin-polarized bands in the middle of original band gap and is responsible for the band gap reduction and visible light photocatalytic activity .
To improve the utilization of solar energy and the efficiency of photocatalytic organic pollutant degradation, novel Z-scheme heterojunctions with high visible light catalytic performances have been widely developed. Herein, a novel Z-scheme BiFeO3/Ag/g-C3N4 heterojunction with a hierarchical 1D/0D/2D structure and visible light absorption was constructed by matching the suitable band structure between 1D BiFeO3 and 2D g-C3N4 and employing the localized surface plasmon resonance (LSPR) effect of 0D Ag nanoparticles. BiFeO3 nanofibers were synthesized via the electrospinning technique, providing short electron transport paths and visible light absorption range for g-C3N4. Plasmonic Ag nanoparticles were photodeposited on the surface of BiFeO3 to enhance the separation efficiency of the photogenerated electron–hole pairs between the bulk interfaces. UV-vis DRS, PL, photocurrent and EIS spectra confirmed the important roles of Ag and BiFeO3 in improving the photocatalytic activity of the Z-scheme heterojunction. The working principle of the BiFeO3/Ag/g-C3N4 Z-scheme heterojunction was proposed, indicating that ˙O2− and ˙OH are the main active species for the photocatalytic degradation of methylene blue (MB). The prepared BiFeO3/Ag/g-C3N4 heterojunction exhibited the highest photocatalytic activity, where its rate constant was 5.84 times higher than that of the pristine BiFeO3 and 3.26 times higher than that of the pristine g-C3N4. This study offers a new means for the design of novel high-performance photocatalysts, which can be a promising candidate in industrial applications.
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