Fuel Cell Nanomaterials Center


Fuel Cell Nanomaterials Center

Time filter
Source Type

Tsuneda T.,Fuel Cell Nanomaterials Center | Singh R.K.,Fuel Cell Nanomaterials Center | Nakata A.,Japan National Institute of Materials Science
Journal of Computational Chemistry | Year: 2017

Low-lying excited states of planarly extended nanographenes are investigated using the long-range corrected (LC) density functional theory (DFT) and the spin-flip (SF) time-dependent density functional theory (TDDFT) by exploring the long-range exchange and double-excitation correlation effects on the excitation energies, band gaps, and exciton binding energies. Optimizing the geometries of the nanographenes indicates that the long-range exchange interaction significantly improves the C-C bond lengths and amplify their bond length alternations with overall shortening the bond lengths. The calculated TDDFT excitation energies show that long-range exchange interaction is crucial to provide accurate excitation energies of small nanographenes and dominate the exciton binding energies in the excited states of nanographenes. It is, however, also found that the present long-range correction may cause the overestimation of the excitation energy for the infinitely wide graphene due to the discrepancy between the calculated band gaps and vertical ionization potential (IP) minus electron affinity (EA) values. Contrasting to the long-range exchange effects, the SF-TDDFT calculations show that the double-excitation correlation effects are negligible in the low-lying excitations of nanographenes, although this effect is large in the lowest excitation of benzene molecule. It is, therefore, concluded that long-range exchange interactions should be incorporated in TDDFT calculations to quantitatively investigate the excited states of graphenes, although TDDFT using a present LC functional may provide a considerable excitation energy for the infinitely wide graphene mainly due to the discrepancy between the calculated band gaps and IP-EA values. © 2017 Wiley Periodicals, Inc.

Uchida H.,Clean Energy Research Center | Uchida H.,Fuel Cell Nanomaterials Center | Puengjinda P.,Clean Energy Research Center | Shimura K.,Yamanashi University | And 3 more authors.
ECS Transactions | Year: 2017

We have examined the durability of oxygen and hydrogen electrodes for reversible solid oxide cells (R-SOCs). The use of a dense, uniform samaria-doped ceria (SDC) interlayer was very important to obtain high performance and high durability of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) - SDC composite oxygen electrode. Double-layer hydrogen electrodes, consisting of SDC scaffold with highly dispersed Ni-Co nanoparticles as the catalyst layer (CL) and a thin current collecting layer (CCL) of either Ni-SDC or Ni-YSZ cermet, exhibited nearly identical initial performance at 800°C, while the use of Ni-YSZ CCL together with three-dimensional network of Ni in the CL resulted in higher durability. © The Electrochemical Society.

Bae B.,Fuel Cell Nanomaterials Center | Hoshi T.,Yamanashi University | Miyatake K.,Fuel Cell Nanomaterials Center | Miyatake K.,Yamanashi University | Watanabe M.,Fuel Cell Nanomaterials Center
Macromolecules | Year: 2011

Poly(arylene ether sulfone) multiblock copoly. were synthesized via oligomeric sulfonation. The successful oligomeric sulfonation enabled multiblock copolymer membranes with different hydrophobic block moiety (biphenyl and naphthalene units). High local concentration of sulfonic acid groups within the hydrophilic blocks enhanced the phase separation between hydrophilic and hydrophobic moiety. Rigid, nonpolar, and planar hydrophobic moiety such as naphthalene groups were effective in increasing proton conductivity and decreasing gas permeability. The multiblock copolymers with naphthalene hydrophobic units with IEC = 2.01 mequiv/g showed comparable proton conductivity to Nafion NRE 212 membrane (0.91 mequiv/g) at >40% RH. The longer blocks were found to increase a characteristic factor (ratio of the proton conductivity to the water volume fraction) as well as phase separation. The membrane showed relatively low oxidative stability under Fenton's test conditions due to higher water uptake and swelling. However, low gas permeability could compensate this drawback for fuel cell applications. © 2011 American Chemical Society.

Uchida H.,Clean Energy Research Center | Uchida H.,Fuel Cell Nanomaterials Center | Nishida R.,Yamanashi University | Tatsuzawa M.,Yamanashi University | And 3 more authors.
ECS Transactions | Year: 2011

We have synthesized nanometer-sized Ni 100-xCo x (X = 0 to 50) alloy catalysts supported on hollow particles of samaria-doped ceria [SDC, (CeO 2) 0.8(SmO 1.5) 0.2] by spraying a mixed solution of the corresponding metal nitrates and acetates in an atmospheric pressure plasma. The performances of Ni 80Co 20/SDC catalyst in both SOFC and steam electrolysis (p[H 2O] = 0.6 atm) were found to be the highest among alloys and pure Ni (X = 0) supported on the SDC at 800 to 900°C. ©The Electrochemical Society.

Yano J.,Fuel Cell Nanomaterials Center | Watanabe M.,Fuel Cell Nanomaterials Center | Uchida H.,Fuel Cell Nanomaterials Center | Uchida H.,Yamanashi University
Langmuir | Year: 2011

The effects of anion adsorption on the activities for the oxygen reduction reaction (ORR) at a Pt film electrode in electrolyte solutions (HClO4 and HF at various concentrations) were analyzed using an electrochemical quartz crystal microbalance (EQCM) and a rotating disk electrode (RDE). With an increasing HClO4 concentration [HClO4], the onset potential for the Pt oxide formation in the voltammogram shifted in the positive direction, accompanied by a compression of the hydrogen adsorption/oxidation wave to less positive potentials. This is ascribed to a specific adsorption of the ClO4 - anion, because the [HClO4] dependence of the mass change δm detected by EQCM in the double-layer region was found to be fitted well by a Frumkin-Temkin adsorption isotherm. The potential dependencies of δm in both 0.1 and 0.5 M HClO4 solutions accord well with those of the ν(Cl-O) intensities observed by in situ Fourier transform infrared (FTIR) spectroscopy in the potential range from 0.3 to 0.6 V. The kinetically controlled current densities jk for the ORR at the Pt-RDE were found to decrease with increasing [HClO4], because of the blocking of the active sites by specifically adsorbed ClO4 -. The values of jk in the non-adsorbing 0.1MHF electrolyte solution, however, were smaller than those in 0.1MHClO4. It was found that the low ORR activity could be ascribed to the lowH+ activity in the weak acid solution of HF. We, for the first time, detected a reversible mass change for one or more adsorbed oxygen species on the Pt-EQCM in O2-saturated and He-purged HF and HClO4 solutions. The coverages of oxygen species θO on Pt were found to increase in theO2-saturated solution. High values of θO inO2-saturated 7mMHF suggest that the ORR rate was limited by the very low H+ activity in the solution, and the adsorbed oxygen species remained on the surface because of a slow consumption rate. © 2011 American Chemical Society.

Ono H.,Japan Science and Technology Agency | Miyake J.,Yamanashi University | Miyake J.,Japan Science and Technology Agency | Uchida M.,Fuel Cell Nanomaterials Center | And 4 more authors.
Journal of Materials Chemistry A | Year: 2015

A novel series of ammonium-containing copolymers (QPAFs) were synthesized as anion exchange membranes for alkaline fuel cell applications. The precursor copolymers (Mw = 28.3-90.1 kDa) composed of perfluoroalkylene and phenylene groups were obtained by a nickel promoted polycondensation reaction. Chloromethylation and quaternization reactions of the precursors provided thin and ductile QPAF membranes with ion exchange capacity (IEC) ranging from 0.79 to 1.74 meq g-1. The QPAF membranes exhibited a phase-separated morphology based on the hydrophilic/hydrophobic differences in the main chain structure. The QPAF membrane with an optimized copolymer composition and IEC = 1.26 meq g-1 showed high hydroxide ion conductivity (95.5 mS cm-1 in water at 80 °C), excellent mechanical properties (large elongation at break (218%)), and reasonable alkaline stability at 80 °C. An alkaline fuel cell using the QPAF as the membrane and electrode binder achieved the maximum power density of 139 mW cm-2 at a current density of 420 mA cm-2. © 2015 The Royal Society of Chemistry.

Uchida H.,Clean Energy Research Center | Uchida H.,Fuel Cell Nanomaterials Center | Puengjinda P.,Clean Energy Research Center | Miyano K.,Yamanashi University | And 4 more authors.
ECS Transactions | Year: 2013

For the hydrogen electrode in the solid oxide electrolysis cell (SOEC), nanometer-sized Ni catalysts were highly dispersed on samaria-doped ceria (SDC). It was found that the current density on Ni-dispersed SDC at 900 °C and the potential of -1.0 V vs. air increased by 1.5 times with decreasing the Ni particle size from 70 nm to 40 nm, even when the Ni-loading was decreased from 17 vol.% to 8 vol.%. © The Electrochemical Society.

Loading Fuel Cell Nanomaterials Center collaborators
Loading Fuel Cell Nanomaterials Center collaborators