Xiaoxi Zuo

One-pot solvothermal synthesis of three-dimensional (3D) BiOI/BiOCl composites with enhanced visible-light photocatalytic activities for the degradation of bisphenol-A

Three-dimensional (3D) BiOI/BiOCl composite microspheres with enhanced visible-light photodegradation activity of bisphenol-A (BPA) are synthesized by a simple, one-pot, template-free, solvothermal method using BiI(3) and BiCl(3) as precursors. These 3D hierarchical microspheres with heterojunction structures are composed of 2D nanosheets and have composition-dependent absorption properties in the ultraviolet and visible light regions. The photocatalytic oxidation of BPA over BiOI/BiOCl composites followed pseudo first-order kinetics according to the Langmuir-Hinshelwood model. The highest photodegradation efficiency of BPA, i.e., nearly 100%, was observed with the BiOI/BiOCl composite (containing 90% BiOI) using a catalyst dosage of 1 g L(-1) in the BPA solution (C(0)=20 mg L(-1), pH=7.0) under visible light irradiation for 60 min. Under these conditions, the reaction rate constant was more than 4 and 20 times greater than that of pure BiOI and the commercially available Degussa P25, respectively. The superior photocatalytic activity of this composite catalyst is attributed to the suitable band gap energies and the low recombination rate of the photogenerated electron-hole pairs due to the presence of BiOI/BiOCl heterostructures. Only one intermediate at m/z 151 was observed in the photodegradation process of BPA by liquid chromatography combined with mass spectrometry (LC-MS) analysis, and a simple and hole-predominated photodegradation pathway of BPA was subsequently proposed. Furthermore, this photocatalyst exhibited a high mineralization ratio, high stability and easy separation for recycling use, suggesting that it is a promising photocatalyst for the removal of BPA pollutants.

Efficient adsorption and visible-light photocatalytic degradation of tetracycline hydrochloride using mesoporous BiOI microspheres.

A novel microsphere-like BiOI hierarchical material was successfully synthesized by a one-step solution method at room temperature using polyvinylpyrrolidone (PVP) as structure directing reagent, its morphology, structure, surface area, photoabsorption were characterized, and the removal of tetracycline hydrochloride (TC) was evaluated under dark adsorption and visible light irradiation. It was shown that the BiOI microspheres formed in the precursor solution with PVP exhibit a mesoporous surface layer, 28.1m(2)g(-1) surface area, 1.91 eV band gap energy (E(g) value), and twofold removal ability to tetracycline hydrochloride (TC), i.e. adsorptive separation and visible light photocatalytic degradation. The adsorption process of TC on BiOI microspheres can be described by pseudo-second-order kinetics model and both Freundlich and Langmuir equations well described the adsorption isotherm but the former is better. More importantly, the BiOI microspheres exhibit an excellent photocatalytic degradation and mineralization capability to TC under visible light irradiation, which comes from its electronic band structure, high surface area and high surface-to-volume ratio. In addition, the BiOI microspheres are stable during the reaction and can be used repeatedly, showing promising prospect for the treatment of TCs in future industrial application.

Oxygen-rich bismuth oxyhalides: generalized one-pot synthesis, band structures and visible-light photocatalytic properties

A series of bismuth oxyhalides with controllable composition and band structure have been successfully synthesized by a facile and general one-pot hydrothermal route using Bi2O3 as the starting material; their band structures and visible-light-induced photocatalytic performances are investigated.

Adsorptive separation and photocatalytic degradation of methylene blue dye on titanate nanotube powders prepared by hydrothermal process using metal Ti particles as a precursor.

Titanate nanotube powders (TNTPs) with the twofold removal ability, i.e. adsorptive separation and photocatalytic degradation, are synthesized under hydrothermal conditions using metal Ti particles as a precursor in the concentrated alkaline solution, and their morphology, structure, adsorptive and photocatalytic properties are investigated. Under hydrothermal conditions, the titanate nanotubes (TNTs) with pore diameter of 3-4nm are produced on the surface of metal Ti particles, and stacked together to form three-dimensional (3D) network with porous structure. The TNTPs synthesized in the autoclave at 130°C for 24h exhibits a maximum adsorption capability of about 197mg g(-1) in the neutral methylene blue (MB) solution (40mg L(-1)) within 90min, the adsorption process can be described by pseudo second-order kinetics model. Especially, in comparison with the adsorptive and the photocatalytic processes are performed in turn, about 50min can be saved through synchronously utilizing the double removal ability of TNTPs when the removal ratio of MB approaches 95% in MB solution (40mg L(-1)) at a solid-liquid (S/L) ratio of 1:8 under ultraviolet (UV) light irradiation. These 3D TNTPs with the twofold removal properties and easier separation ability for recycling use show promising prospect for the treatment of dye pollutants from wastewaters in future industrial application.

One-pot synthesis of micro/nano structured β-Bi2O3 with tunable morphology for highly efficient photocatalytic degradation of methylparaben under visible-light irradiation

β-Bi2O3 micro/nanostructures with tunable morphologies were synthesized via a one-pot solvothermal–calcining route, and their photocatalytic activity toward degrading methylparaben (MeP, a widely used preservative with estrogenic activity) was evaluated under visible-light (λ ≥ 420 nm) irradiation. The formation process of β-Bi2O3 catalysts can be described as reduction of Bi3+ through a solvothermal reaction, followed by oxidization of metal Bi via calcination in air. During this process, the organic reductants (single or a mixture of ethylene glycol, D-fructose, and ascorbic acid) play important roles in determining the final morphologies and structures of the materials. Photocatalytic tests reveal that MeP can be effectively degraded and mineralized by using synthetic β-Bi2O3 catalysts, and the reaction rate constant of an optimum sample is more than 25 and 160 times faster than a commercial Bi2O3 and synthetic N-TiO2, respectively. The superior photocatalytic activity of the optimum product is ascribed to its pure beta phase with a narrower band gap, good absorption of visible light, more efficient separation of electrons and holes, relatively higher BET specific surface area, and three-dimensional architectures, which favor more surface active sites and easier mass and photoinduced charge transportations. In addition, the main reactive oxygen species and possible degradation intermediates were detected, and the results suggest that photogenerated holes and superoxide radicals are the predominant species in the photochemical oxidation process.

Electrocatalytic oxidation and simultaneous determination of catechol and hydroquinone at a novel carbon nano-fragment modified glassy carbon electrode

In this paper, the electrochemical oxidation and differential pulse voltammetry (DPV) determination of catechol (CC) and hydroquinone (HQ) are studied at a novel carbon nano-fragment (CNF) modified glassy carbon electrode (CNF/GCE). The CNF modifier is prepared using the graphite cycled in lithium-ion batteries as the raw material through a ball mill process. The redox reactions of CC and HQ at the CNF/GCE are a two proton and electron process and controlled by the diffusion step. Compared to the GCE, the as-prepared CNF/GCE shows enhanced electrocatalytic activity and a peak potential difference of about 104 mV towards the oxidation of CC and HQ in a 0.1 mol L−1 acetate buffer solution (ABS, pH = 5.9), which makes it suitable for simultaneous determination of CC and HQ by DPV. Under the optimized conditions, the oxidation peak current of CC is linear over a range from 2.0 × 10−6 mol L−1 to 2.0 × 10−4 mol L−1 in the presence of 5.0 × 10−5 mol L−1 HQ with a detection limit of 1.0 × 10−7 mol L−1 (S/N = 3). Correspondingly, the oxidation peak current of HQ is linear over a range from 6.0 × 10−6 mol L−1 to 2.0 × 10−4 mol L−1 in the presence of 5.0 × 10−5 mol L−1 CC with a detection limit of 2.5 × 10−7 mol L−1 (S/N = 3). In addition, this CNF/GCE exhibits high selectivity, reproducibility and stability, showing its promising application prospect.

Flower-like Bi4O5I2/Bi5O7I nanocomposite: facile hydrothermal synthesis and efficient photocatalytic degradation of propylparaben under visible-light irradiation

Nonstoichiometric bismuth oxyiodide materials have exhibited high potential for applications in visible-light photocatalytic environmental cleaning and solar energy conversion. Herein, novel Bi4O5I2/Bi5O7I nanocomposites, BiOI nanosheets, Bi4O5I2 nanoflowers, and Bi5O7I microfibers are synthesized by controlling the alkalinity of reaction solutions in a facile one-pot hydrothermal route. The as-prepared Bi4O5I2/Bi5O7I nanocomposite exhibits excellent visible-light photocatalytic performance for the degradation of propylparaben (PPB, a potential environmental contaminant structure that contains a benzene ring, hydroxyl, and carboxyl), which is approximately 32, 33, and 4 times higher than that of pure BiOI, Bi5O7I, and Bi4O5I2, respectively. The enhanced photocatalytic activity of the Bi4O5I2/Bi5O7I composite can be attributed to enhancement of charge separation by the formation of Bi4O5I2/Bi5O7I interfaces, more positive valence band edge potential at +2.18 V, good absorption from UV to visible light, three-dimensional flower-like morphology composed of number nanoflakes, and large specific surface area with mesoporous features. The band structures of Bi4O5I2 and Bi5O7I, the electrochemical oxidation behaviors of PPB, and the roles of the primary photogenerated oxidative species are analyzed, then a reasonable photocatalytic mechanism is proposed based on the experimental results. In addition, the as-synthesized Bi4O5I2/Bi5O7I heterojunction remains stable throughout photocatalytic process and can be used repeatedly, indicating its potential for practical applications.

Reclaiming the spent alkaline zinc manganese dioxide batteries collected from the manufacturers to prepare valuable electrolytic zinc and LiNi0.5Mn1.5O4 materials.

A process for reclaiming the materials in spent alkaline zinc manganese dioxide (Zn-Mn) batteries collected from the manufacturers to prepare valuable electrolytic zinc and LiNi0.5Mn1.5O4 materials is presented. After dismantling battery cans, the iron cans, covers, electric rods, organic separator, label, sealing materials, and electrolyte are separated through the washing, magnetic separation, filtrating, and sieving operations. Then, the powder residues react with H2SO4 (2 mol L(-1)) solution to dissolve zinc under a liquid/solid ratio of 3:1 at room temperature, and subsequently, the electrolytic Zn with purity of ⩾99.8% is recovered in an electrolytic cell with a cathode efficiency of ⩾85% under the conditions of 37-40°C and 300 A m(-2). The most of MnO2 and a small quantity of electrolytic MnO2 are recovered from the filtration residue and the electrodeposit on the anode of electrolytic cell, respectively. The recovered manganese oxides are used to synthesize LiNi0.5Mn1.5O4 material of lithium-ion battery. The as-synthesized LiNi0.5Mn1.5O4 discharges 118.3 mAh g(-1) capacity and 4.7 V voltage plateau, which is comparable to the sample synthesized using commercial electrolytic MnO2. This process can recover the substances in the spent Zn-Mn batteries and innocuously treat the wastewaters, indicating that it is environmentally acceptable and applicable.

L-Asparagine-assisted synthesis of flower-like β-Bi2O3 and its photocatalytic performance for the degradation of 4-phenylphenol under visible-light irradiation

Large-scale synthesis of nanosized β-Bi2O3 is a significant challenge due to its metastable state. A facile L-asparagine-assisted reflux–calcination route was successfully developed for the large-scale preparation of β-Bi2O3 micro/nanostructures under mild conditions (low temperature, atmospheric pressure, and wide temperature windows). The composition, phase structure, morphology, surface area, and photoabsorption properties of as-synthesized β-Bi2O3 and its precursor were systematically characterized. The phase transformation conditions and possible formation mechanism of flower-like β-Bi2O3 were discussed. It is found that with a simple reflux process under atmospheric pressure at 100 °C, uniform monodisperse bismuth–asparagine complex microspheres with average diameters of ∼500 nm were produced and flower-like β-Bi2O3 micro/nanostructures were then conveniently obtained after precursor calcination at temperatures ranging from 340 °C to 420 °C. A surface CO32− coordination effect introduced from L-asparagine explained the formation of stabilized β-Bi2O3 at low temperatures (up to 420 °C). The as-synthesized β-Bi2O3 shows excellent photocatalytic activity toward the degradation of 4-phenylphenol under visible-light irradiation, which is 3.7 and 21.4 times faster than the removal rates of β-Bi2O3 nanospheres and a commercial β-Bi2O3, respectively, and allows for the elimination of 93.2% total organic carbon after 60 min of irradiation. In addition, the photogenerated reactive species were identified by radical scavenger experiments and electron paramagnetic resonance spectroscopy, and a possible visible-light-induced photocatalytic mechanism was then proposed.

A reconstructed graphite-like carbon micro/nano-structure with higher capacity and comparative voltage plateau of graphite

A reconstructed graphite-like carbon (r-GC) micro/nano-structure with a higher capacity than and a comparative voltage plateau to commercial graphite anodes of lithium-ion batteries (LIBs) is synthesized from an expandable graphite raw material based on an up-down-up synthetic strategy. The expandable graphite powders are thermally expanded, hydrothermally cut, and ultrasonically crushed in turn to prepare a suspension containing nano-fragments with a graphitic plane nano-structure as a carbon precursor. Then, the r-GC micro/nano-structure can be obtained by stacking the graphite nano-fragments through spray drying the suspension and subsequently conducting a calcining treatment. This r-GC exhibits an initial capacity of 575.3 mA h g−1 at 0.1C and a reversible capacity of 508.4 mA h g−1 after 100 cycles. Especially, its comparative voltage plateau of commercial graphite is incapable for other known anode materials for LIBs. In the potential window of 0.3–0.01 V (vs. Li+/Li), a maximum capacity of approximately 432.1 mA h g−1, 1.16 times the theoretical capacity of graphite (372 mA h g−1), is obtained. The unique element stability, capacity, and voltage plateau indicate that the as-synthesized r-GC is a promising sheet-like anode material for LIBs. In addition, an embedded-defect and graphite-dominant graphite/graphene cooperative lithiation mechanism is proposed to elaborate the capacity and voltage plateau of r-GC.