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Abstract

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Materials

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Chemistry

Preparation of Polyoxometalate-based Photo-responsive Membranes for the Photo-activation of Manganese Oxide Catalysts

Published: August 7th, 2018

DOI:

10.3791/58072

1Department of Applied Chemistry, The University of Tokyo, 2Clean Energy Research Center, University of Yamanashi, 3Biofunctional Catalyst Research Team, RIKEN Center for Sustainable Resource Science, 4Earth-Life Science Institute (ELSI), Tokyo Institute of Technology, 5Department of Materials Science and Engineering, Tokyo Institute of Technology, 6National Institute for Materials Science

Here, we present a protocol to prepare charge transfer chromophores based on a polyoxometalate/polymer composite membrane.

This paper presents a method to prepare charge-transfer chromophores using polyoxotungstate (PW12O403-), transition metal ions (Ce3+ or Co2+), and organic polymers, with the aim of photo-activating oxygen-evolving manganese oxide catalysts, which are important components in artificial photosynthesis. The cross-linking technique was applied to obtain a self-standing membrane with a high PW12O403- content. Incorporation and structure retention of PW12O403- within the polymer matrix were confirmed by FT-IR and micro-Raman spectroscopy, and optical characteristics were investigated by UV-Vis spectroscopy, which revealed successful construction of the metal-to-metal charge transfer (MMCT) unit. After deposition of MnOx oxygen evolving catalysts, photocurrent measurements under visible light irradiation verified the sequential charge transfer, Mn → MMCT unit → electrode, and the photocurrent intensity was consistent with the redox potential of the donor metal (Ce or Co). This method provides a new strategy for preparing integrated systems involving catalysts and photon-absorption parts for use with photo-functional materials.

The development of solar energy conversion systems using artificial photosynthesis or solar cells is necessary to enable the provision of alternative energy sources that can ameliorate global climate and energy issues1,2,3,4. Photo-functional materials can be broadly categorized into two groups, semiconductor-based systems and organic molecule-based systems. Although many different system types have been developed, improvements still need to be made because semiconductor systems suffer from a lack of precise charge transfer control, and orga....

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It is advisable to refer to all relevant material safety data sheets (MSDS) prior to using chemicals, as some used in these syntheses are highly acidic and corrosive. In addition, one polymer used in this work (polyacrylamide) may contain the carcinogenic monomer, acrylamide. The use of personal protective equipment (safety glasses, gloves, lab coat, full-length pants, closed-toe shoes) is required to prevent injuries from chemicals or heat. After conducting the cross-linking process, membrane samples should be stored in.......

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Retention of the POM structure in the polymer matrix was confirmed by FT-IR and micro-Raman spectroscopy (Figure 1); vibration peaks corresponding to the Keggin structure of POM were observed, and peaks of the polymers were found to be shifted due to hydrogen bonding with POM. Spectroscopic analysis was very useful for determining successful construction of the charge transfer unit, and this was also confirmed by the apparent color change of the samples (

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It is critical to apply the cross-linking method introduced by Helen et al.14 to develop a self-standing membrane. When polyvinyl acetate was applied as the base polymer in this study, aggregation of H3PW12O40 occurred, which prevented formation of the self-standing membrane. However, when fabrication of the membrane was attempted utilizing Nafion as the base polymer, there was no progression of the reaction with Ce3+ and Co2+, althou.......

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A. Y. received financial support from the Global Center of Excellence for Mechanical Systems Innovation program of the University of Tokyo and from the University Tokyo Grant for Ph.D. Research. This work is partly supported by JSPS KAKENHI Grant-in-Aid for Young Scientists (B) (17K17718).

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Name Company Catalog Number Comments
Poly(vinyl Alcohol) 1000, Completely Hydrolyzed Wako 162-16325
Polyacrylamide, Mv 6,000,000 Polyaciences, Inc. 2806 May contain carcinogenic monomer, acrylamide.
12 Tungsto(VI)phosphoric Acid n-Hydrate Wako 164-02431 Highly acidic
Acetone 99.5 + %(GC) Wako 012-00343
25% Glutaraldehyde Solution Wako 079-00533
Hydrochloric Acid 35-37% Wako 080-01066
Cerium(III) Nitrate Hexahydrate 98 + %(Ti) Wako 031-09732
Cobalt(II) Chloride Hexahydrate 99 + %(Ti) Wako 036-03682
Pottasium Permanganate 99.3 + %(Ti) Wako 167-04182 Highly oxydative
Sodium Thiosulfate Pentahydrate 99 + %(Ti) Wako 197-03585
Automatic spray gun Lumina ST-6

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