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Wakolo SW, Tryk DA, Nishiyama H, Miyatake K, Iiyama A, Inukai J. Various states of water species in an anion exchange membrane characterized by Raman spectroscopy under controlled temperature and humidity. Phys Chem Chem Phys 2024; 26:1658-1670. [PMID: 38009441 DOI: 10.1039/d3cp03660j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2023]
Abstract
Anion exchange membrane fuel cells (AEMFCs) hold the key to future mass commercialisation of fuel cell technology, even though currently, AEMFCs perform less optimally than proton exchange membrane fuel cells (PEMFCs). Unlike PEMFCs, AEMFCs have demonstrated the capability to operate independently of Pt group metal-based catalysts. Water characterization inside the membrane is one factor that significantly influences the performance of AEMFCs. In this paper, different water species inside an anion exchange membrane (AEM), QPAF-4, developed at the University of Yamanashi, were studied for the first time using micro-Raman spectroscopy. Spectra of pure water, alkaline solutions, and calculations based on density functional theory were used to identify the water species in the AEM. The OH stretching band was deconvoluted into nine unique Gaussian bands. All the hydrogen-bonded OH species increased steadily with increasing humidity, while the CH and non-H-bonded OH remained relatively constant. These results confirm the viability of micro-Raman spectroscopy in studying the various water-related species in AEMs. The availability of this technique is an essential prerequisite in improving the ionic conductivity and effectively solving the persisting durability challenge facing AEMFCs, thus hastening the possibility of mass commercialisation of fuel cells.
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Affiliation(s)
- Solomon Wekesa Wakolo
- Integrated Graduate School of Medicine, Engineering, and Agricultural Sciences, University of Yamanashi, 4-3-37 Takeda, Kofu, Yamanashi 400-8510, Japan
| | - Donald A Tryk
- Hydrogen and Fuel Cell Nanomaterials Research Center, University of Yamanashi, 6-43 Miyamae, Kofu, Yamanashi 400-0021, Japan.
| | - Hiromichi Nishiyama
- Hydrogen and Fuel Cell Nanomaterials Research Center, University of Yamanashi, 6-43 Miyamae, Kofu, Yamanashi 400-0021, Japan.
| | - Kenji Miyatake
- Hydrogen and Fuel Cell Nanomaterials Research Center, University of Yamanashi, 6-43 Miyamae, Kofu, Yamanashi 400-0021, Japan.
- Clean Energy Research Center, University of Yamanashi, 4-3-11 Takeda, Kofu, Yamanashi 400-8510, Japan
- Department of Applied Chemistry, Waseda University, Tokyo 169-8555, Japan
| | - Akihiro Iiyama
- Hydrogen and Fuel Cell Nanomaterials Research Center, University of Yamanashi, 6-43 Miyamae, Kofu, Yamanashi 400-0021, Japan.
| | - Junji Inukai
- Hydrogen and Fuel Cell Nanomaterials Research Center, University of Yamanashi, 6-43 Miyamae, Kofu, Yamanashi 400-0021, Japan.
- Clean Energy Research Center, University of Yamanashi, 4-3-11 Takeda, Kofu, Yamanashi 400-8510, Japan
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Egan CK, Paesani F. Assessing Many-Body Effects of Water Self-Ions. I: OH–(H2O)n Clusters. J Chem Theory Comput 2018. [DOI: 10.1021/acs.jctc.7b01273] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Colin K. Egan
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093, United States
| | - Francesco Paesani
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093, United States
- Materials Science and Engineering, University of California San Diego, La Jolla, California 92093, United States
- San Diego Supercomputer Center, University of California San Diego, La Jolla, California 92093, United States
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Ogata Y, Kawashima Y, Takahashi K, Tachikawa M. Theoretical vibrational spectra of OH(-)(H2O)2: the effect of quantum distribution and vibrational coupling. Phys Chem Chem Phys 2015; 17:25505-15. [PMID: 26365920 DOI: 10.1039/c5cp03632a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
We performed ab initio path integral molecular dynamics simulations for the hydroxide-water cluster, OH(-)(H2O)2, at 50 K, 100 K, and 150 K to investigate its flexible structure. From our simulations, we found that nuclear quantum effects enhance hydroxide hydrogen atom inversion and the conformational change between isomers occurs by simultaneous rotation of the free hydrogen atom. We propose the importance of including the transition state conformer with C2 symmetry, for the description of this system at temperatures realized in predissociation experiments. Temperature dependence of relative populations of each conformer along with multidimensional vibrational calculations were used to simulate the vibrational spectra and compare with the experimental spectra of Johnson and coworkers. We assign the doublet peaks seen in the experiment at 2500 to 3000 cm(-1), as the mixture of the ionic hydrogen bonded OH stretching overtone, ionic hydrogen bonded OH bending overtone, and the combination band of the ionic hydrogen bonded OH stretch and bend, which are modulated by the van der Waals OO vibrations. We concluded that for OH(-)(H2O)2, the vibrational couplings between the ionic hydrogen bonded motion and floppy modes contribute to the broadening of peaks observed in the 2500 to 3000 cm(-1) region.
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Affiliation(s)
- Yudai Ogata
- Graduate school of Nanobioscience, Yokohama City University, Yokohama 236-0027, Japan.
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