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Magnetic field effect on heterogeneous photocatalysis

Paper ID Volume ID Publish Year Pages File Format Full-Text
53642 46977 2015 14 PDF Available
Title
Magnetic field effect on heterogeneous photocatalysis
Abstract

•Highly reproducible magnetic field effect (MFE) on heterogeneous photocatalysis.•Various parameters related to MFE revelation and perturbation are discussed.•A model for MFE involving dissolved oxygen (DO) is presented (OANS model).

Magnetic field effect (MFE) on heterogeneous photocatalysis is investigated, using mostly ZnO powder and methylene blue (MB) solution. Reproducibility with errors less than 2% is obtained with our newly-developed in-situ measurement system. Multiple parameters are involved in MFE phenomena. MFE magnitude depends on magnetic field intensity, while other parameters are also important, including: initial MB concentration, settling time of solution, and level/state of dissolved oxygen (DO). Short-range-order, or very-short-range-order diffusion in the Helmholtz layer just outside powder appears responsible for MFE. Accordingly, powder surface conditions, e.g. H2O, CO2 adsorption, significantly influence MFE, and magnetic adsorption appears correlated. Temperature-dependent MFE and magneto-hydrodynamic effect on photocatalytic silver reduction/deposition are also observed for the first time.A model is proposed, whereby, in the volume in close proximate to the powder, electrostatic potential and the corresponding magnetic flux would be perturbed, resulting in the appearance of a net Lorentz force on paramagnetic DO, which is essentially responsible for various MFE phenomena (OANS model). DO could be involved with (i) formation of DO-dye complex, (ii) modifying powder adsorption layer, (iii) scavenging rate of excited electrons, (iv) spin chemistry involving singlet–triplet conversion, and (v) manifestation of magneto-hydrodynamic effect. Simultaneous multiple mechanisms are suggested for MFE.

Graphical abstractSchematic illustration of OANS model (for Graphical Abstract).Figure optionsDownload full-size imageDownload high-quality image (143 K)Download as PowerPoint slide

Keywords
Magnetic field effect (MFE); Heterogeneous photocatalysis; Dissolved oxygen (DO); ZnO powder; Methylene blue (MB) solution; Magnetic adsorption
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Publisher
Database: Elsevier - ScienceDirect
Journal: Catalysis Today - Volume 258, Part 2, 1 December 2015, Pages 634–647
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us