Intermediate-temperature proton conductors and their applications to energy and environmental devices

Hibino, Takashi

doi:10.2109/jcersj2.119.677

Cited by 20 publications

(20 citation statements)

References 72 publications

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“…Here, (P 2 O 7 ) x P2O7 , (2PO 4 )″ P2O7 , and (HP 2 O 7 ) · P2O7 denote pyrophosphate ions, phosphate ions, and hydrogen pyrophosphate defects at pyrophosphate sites, respectively. Measurements of the H/D isotope effect on proton conductivity gave useful knowledge concerning these active protons; because the protons function as the predominant charge carrier in the sample, it has been proposed that proton transfer occurs through hydrogen bonds with oxide ions in the P 2 O 7 units (hopping mechanism) …”

Section: Resultsmentioning

confidence: 99%

Solid‐state NMR study of dopant effects on the chemical properties of Mg‐, In‐, and Al‐doped SnP₂O₇

Nishida

Tanaka

Fukaya

et al. 2014

Magnetic Reson in Chemistry

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The effects of doped low-valence cations on the properties of the SnP2 O7 proton conductor at ambient temperature are investigated from changes in solid-state NMR spectra and nuclear magnetic relaxation times. Although the T1 H values increased with decreasing acidity as a result of cation exchange, the (1)H chemical shifts moved to lower field in Al- and In-doped materials compared with undoped ones. Furthermore, the shifts changed to higher field in Mg-doped materials, suggesting the existence of different protonic species in those materials. The bulk phosphate chemical shifts in the (31)P dipolar-decoupling MAS NMR spectra were very similar, regardless of the nature and amount of the doping species. On the other hand, by (1)H/(31)P cross-polarization MAS NMR, P2O7 signals interacting with an interstitial proton [Q(1)(proton)] were observed in all the undoped and doped SnP2 O7, while acidic P-OH-type phosphate signals [Q(1)(acid)] were additionally observed in the Mg-doped conductor. The different affinity of the proton with the dopants and phosphates caused lower conductivity and larger activation energy in the Mg-doped materials, compared with those in the In- and Al-doped materials.

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Section: Resultsmentioning

confidence: 99%

Solid‐state NMR study of dopant effects on the chemical properties of Mg‐, In‐, and Al‐doped SnP₂O₇

Nishida

Tanaka

Fukaya

et al. 2014

Magnetic Reson in Chemistry

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“…[16][17][18] powder (0.04 g) was added to 1.00 g of Sn 0.95 Al 0.05 P 2 O 7 powder, kneaded using a mortar and pestle, and then cold-rolled to a thickness of 250 μm using a laboratory rolling mill.…”

Section: Methodsmentioning

confidence: 99%

Rechargeable PEM Fuel-Cell Batteries Using Quinones as Hydrogen Carriers

Nagao

Kobayashi

Yamamoto

et al. 2015

J. Electrochem. Soc.

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Rechargeable fuel-cell batteries (RFCBs) that employ organic chemical hydrides as hydrogen storage media have potential as nextgeneration power sources; however, the reversible storage and release of hydrogen remains a significant challenge. In particular, the hydrogenation of organic compounds during cell charge is difficult to achieve with 100% conversion. However, this report demonstrates that quinones, especially anthraquinone (AQ), can function as a hydrogen carrier for RFCBs, where AQ is hydrogenated to anthrahydroquinone (AH 2 Q) during charge and AH 2 Q is dehydrogenated to AQ during discharge. This redox reaction occurred at a more positive potential than that for hydrogen reduction, so that undesired hydrogen production can be avoided by adjusting the charge voltage to 1 V. The resulting RFCB maintained 100% electrical capacity at room temperature, 91% at 50 • C, and 63% at 75 • C of the respective initial performance with coulombic efficiencies greater than 90% after 300 cycles. Moreover, the RFCB functioned as a secondary battery with energy densities of 0.8-3.4 Wh kg −1 , power densities of 9.5-258.9 W kg −1 , and as a fuel cell with power densities of 0.001-0.26 W cm −3 . Based on the performance and degradation data, the limitations of this RFCB and directions for future research are discussed. A system or device capable of operating an electrochemical cell alternately in electrolyzer and fuel cell modes is called a rechargeable or regenerative fuel cell (RFC).1,2 Applications for RFCs include large-scale renewable energy storage and middle-scale emergency or auxiliary power sources, 3 where hydrogen is usually stored outside the fuel cell to obtain substantially high energy. In contrast, RFCs can be used as energy storage systems for portable electronic devices by integration of the fuel cell with the hydrogen storage medium; however, such electrochemical cells should be classified as batteries rather than fuel cells, because the fuel is not supplied from an external source, but is an integral part of the device. 4 Thus, we have designated this type of cell as a rechargeable fuel-cell battery (RFCB).Hydrogen storage with high capacity, excellent reversibility, and good cycle stability is a key technology for both RFC and RFCB. Typical hydrogen storage methods (in addition to liquefaction or compression of hydrogen) include the physical and chemical adsorption of hydrogen atoms or molecules into materials such as activated carbon and metal hydrides. Activated carbon often requires low temperatures (>−200• C) and/or high pressures (<10 MPa) to achieve high hydrogen adsorption capacity.5 Metal hydrides typically release hydrogen at high temperatures (>150• C). 6 Thus, it is difficult to use these materials as reversible hydrogen carriers for RFCBs because a series of hydrogen production, storage, supply, and utilization processes cannot be conducted under the RFCB operating conditions (e.g., room temperature to 80• C at ambient pressure). Organic chemical hydrides, such as benzene/cyclohexane, tolue...

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“…The presence of leftover phosphoric acid in the unsintered pellets is responsible for the high conductivity values for the unsintered pellets [22,23]. Hibino et al [24,25] exhibited relatively high proton conductivities in the temperature range of 100-700 • C. It seems that the performance of SnP 2 O 7 -based ceramic materials is highly dependent upon the prepared route used.…”

Section: Introductionmentioning

confidence: 99%

Proton and oxide-ion conduction in ZnO doped SnP2O7 ceramics

Xiao

Zhang

Yang

et al. 2012

Journal of Alloys and Compounds

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Intermediate-temperature proton conductors and their applications to energy and environmental devices

Cited by 20 publications

References 72 publications

Solid‐state NMR study of dopant effects on the chemical properties of Mg‐, In‐, and Al‐doped SnP₂O₇

Solid‐state NMR study of dopant effects on the chemical properties of Mg‐, In‐, and Al‐doped SnP₂O₇

Rechargeable PEM Fuel-Cell Batteries Using Quinones as Hydrogen Carriers

Proton and oxide-ion conduction in ZnO doped SnP2O7 ceramics

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Intermediate-temperature proton conductors and their applications to energy and environmental devices

Cited by 20 publications

References 72 publications

Solid‐state NMR study of dopant effects on the chemical properties of Mg‐, In‐, and Al‐doped SnP2O7

Solid‐state NMR study of dopant effects on the chemical properties of Mg‐, In‐, and Al‐doped SnP2O7

Rechargeable PEM Fuel-Cell Batteries Using Quinones as Hydrogen Carriers

Proton and oxide-ion conduction in ZnO doped SnP2O7 ceramics

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Product

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Solid‐state NMR study of dopant effects on the chemical properties of Mg‐, In‐, and Al‐doped SnP₂O₇

Solid‐state NMR study of dopant effects on the chemical properties of Mg‐, In‐, and Al‐doped SnP₂O₇