Photocatalytic composite membranes (BPMs) are preferred materials for wastewater treatment due to their high photocatalytic activity and ease of recovery. However, conventional blending modification methods for preparing BPMs often lead to drawbacks such as uneven distribution of photocatalysts, low loading efficiency, facile detachment of photocatalysts, poor reusability, and a limited specific surface area of the membranes. These issues significantly diminish their photocatalytic activity and restrict their practical applications. To address these challenges, this thesis introduces a novel preparation method for PVP-modified PVDF/BiOBr photocatalytic membranes, using a combination of electrospinning and solvothermal techniques. This approach enhances the stability of BiOBr microspheres on the PVDF nanofiber membranes, effectively tackling the issue of loading powder photocatalysts. These membranes, composed of PVDF nanofibers and uniformly sized BiOBr microspheres, exhibit a significant specific surface area of 15.69 m 2 /g. The modified PVDF/BiOBr photocatalytic membranes demonstrate remarkable degradation efficiencies: 100 % degradation of Rhodamine B (RhB) in 25 min, 93.8 % degradation of tetracycline (TC) in 30 min, and 74.6 % degradation of hexavalent chromium ions (Cr 6+ ) in 60 min. Moreover, after five cyclic experiments, the photocatalytic degradation rate of sample M 3 remains above 99 % with a minimal loss rate of only 0.5 %. The method developed for preparing PVDF/BiOBr photocatalytic membranes represents a universally applicable and straightforward strategy for fabricating advanced membrane materials. This preparation technique not only provides innovative design ideas and fabrication methods for new photocatalytic materials but also extends to other functional materials. The PVDF/BiOBr photocatalytic membrane materials hold great promise in offering technical and theoretical support for photocatalytic wastewater treatment.
Zhongyu Qiu,Naibao Huang,Xiaowen Ge,Jiaping Xuan,Pei Wang
In order to reduce the cost of oxygen reduction reaction (ORR) catalyst, a metal-free N-doped carbon nanocage as ORR catalysts is prepared by using Polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) three-block copolymer (F127), polyvinyl pyrrolidone (PVP) and Zn (OH) 2 as a carbon source, nitrogen source and the morphology retaining agent, respectively, via a self-template method. The structure and microstructure of the N-doped carbon nanocage are characterized via physical characterization methods such as X-ray diffraction, Raman spectroscopy , scanning electron microscopy, transmission electron microscopy , Brunauer–Emmett–Teller method, and X-ray photoelectron spectroscopy. Electrochemical properties are evaluated in an O 2 -saturated alkaline solution. The obtained sample pyrolyzed at 800 °C with 10% content of PVP (C–N-800) presents nano-hollow carbon capsule with a diameter of 100 nm and shell thickness of 8 nm, and has the maximum surface area of 978 m 2 ·g −1 . In O 2 -saturated 0.1 M KOH solution, C–N-800's onset potential, limit current density, and half-wave potential, which are 0.87 V, 5.73 mA/cm 2 @0.45 V, and 0.77 V, respectively, are close to those of commercial 20% Pt/C catalysts. Meanwhile, its electrochemical performance only loss 11.75% after 5000 cycles, showing excellent ORR catalytic performance and stability. During self-assembly of F127, the added PVP participated into the process. Pyrolysis at 800 °C would result in the complete decomposition of F127 and PVP's lipophilic. So, the metal-free N-doped carbon nanocage was obtained and behaved excellent ORR catalytic activity and stability.
In this paper, using PVP-modified polystyrene microspheres as template, tetrabutyl titanate (TEOT), tetraethyl orthosilicate (TEOS) and melamine as precursor, we developed a facile one-pot two-step method to preparing a novel kind of mesoporous hollow SiO 2 @TiO 2 @g-C 3 N 4 ternary composite microspheres with plush surface, in which highly active black titanium dioxide (TiO 2 ) was formed by simple calcination without further chemical reduction treatment. The structure and morphology of the composite microspheres were detailed characterized for understanding the formation mechanism. Research results indicated that the hollow SiO 2 microspheres can promote the formation of oxygen vacancies in TiO 2 , and the ternary combination narrowed the bandgap width of the black hollow composite microspheres to 1.43 eV, thus endowing it with excellent broad-spectrum catalytic performance for rapid photo-degradation of persistent organic pollutants (POPs) such as dyes and antibiotics in water under sunlight. The removal rates of dyes reached more than 70 %, as well as that of antibiotics more than 50 % within one hour. Finally, a plausible catalytic degradation mechanism was discussed.
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