Ito K.,International Institute for Carbon Neutral Energy Research WPI I2CNER
ECS Transactions | Year: 2015
The effect of cathode current collectors on polymer electrolyte membrane water electrolysis (PEMWE) was evaluated with I-V and I-high frequency resistance (HFR) characteristics. Results reveal that cathode current collectors can impact water electrolysis performance by controlling the amount of water accumulation there, which is proved with overpotential analysis and systematic operation such as feeding additional nitrogen gas to cathode. The hydrophilic cathode current collectors invited better performance than hydrophobic ones, because the hydrophilic ones gives less water accumulation there and enough water content in catalyst coated membrane (CCM). The thickness of cathode current collector did not impact the performance. © 2015 The Electrochemical Society.
Alahmer A.,University of Tasmania |
Alahmer A.,Tafila Technical University |
Wang X.,University of Tasmania |
Al-Rbaihat R.,Tafila Technical University |
And 3 more authors.
Applied Energy | Year: 2016
Performance of an adsorption cooling system driven by solar thermal energy was studied under different climatic conditions. The effects of solar collector area, collector slope, hot water temperature and flow rate on the system performance were investigated using the real-time weather data of two cities: Perth, Australia (a representative city in the southern hemisphere) and Amman, Jordan (a representative city in the northern hemisphere). The simulation results showed that the two cities had similar solar radiation during the summer period and that the solar adsorption chiller could reliably provide cooling at a reasonably high system COP. For residential cooling with a total CPC (Compound Parabolic Collector) solar collector area of 36.22 m2, the average system COP was 0.491 for Perth weather conditions and 0.467 for Amman weather conditions, respectively while the cooling capacity was 10.3 kW for Perth and 8.46 kW for Amman, respectively at peak times. Optimum performance occurred when the system run with the CPC collector slope of around 30°, the solar water storage tank volume of 1.4 m3, inlet hot water temperature of 80 °C, and a hot water flow rate of 0.33 kg/s. An economic analysis was further investigated and the results showed that the solar driven adsorption cooling system could reduce the electricity consumption for Perth and Amman cities by 34% and 28%, respectively in comparison to a conventional vapour compression cooling system. © 2016 Elsevier Ltd.
Staykov A.,International Institute for Carbon Neutral Energy Research WPI I2CNER |
Derekar D.,International Institute for Carbon Neutral Energy Research WPI I2CNER |
Yamamura K.,International Institute for Carbon Neutral Energy Research WPI I2CNER
International Journal of Quantum Chemistry | Year: 2016
Oxygen dissociation reaction on gold, palladium, and gold-palladium core/shell nanoparticles was investigated with plane wave basis set, density functional theory. Bader population analysis of charge and electron distribution was employed to understand the change of catalytic activity as a function of the nanopaticle composition. The nanoparticles' electronic properties were investigated and the degree of core/shell charge polarization was estimated for each composition. It was found that surface polarization plays an important role in the catalysis of the initial step of electrophile reactions such as oxygen dissociation. We have investigated the O2 adsorption energy on each nanoparticle and the activation barrier for the oxygen dissociation reaction as a function of the nanoparticle structure. Furthermore, we have investigated the influence of surface geometry, that is., surface bond lengths on the catalytic activity. We have compared the electronic and the geometry effects on the oxygen activation and dissociation. Our design rules for core/shell nanoparticles offer an effective method for control of the surface catalytic activity. Palladium and gold are often used as catalysts in synthetic chemistry. First-principles calculations elucidate the mechanisms that control the surface reactivity of gold, palladium, and gold-palladium core shell nanoparticles in oxygen dissociation reactions. Oxygen dissociation is promoted on the gold surface of gold/palladium core-shell nanoparticles by favorable electron transfer from the core to the shell. Such core-shell electronic effects can be used for fine-tuning the nanoparticles catalytic activity. © 2016 Wiley Periodicals, Inc.
Jiang F.,International Institute for Carbon Neutral Energy Research WPI I2CNER |
Tsuji T.,International Institute for Carbon Neutral Energy Research WPI I2CNER
Water Resources Research | Year: 2015
We develop a numerical simulation that uses the lattice Boltzmann method to directly calculate the characteristics of residual nonwetting-phase clusters to quantify capillary trapping mechanisms in real sandstone. For this purpose, a digital-rock-pore model reconstructed from micro-CT-scanned images of Berea sandstone is filtered and segmented into a binary file. The residual-cluster distribution is generated following simulation of the drainage and imbibition processes. The characteristics of the residual cluster in terms of size distribution, major length, interfacial area, and sphericity are investigated under conditions of different interfacial tension (IFT). Our results indicate that high interfacial tension increases the residual saturation and leads to a large size distribution of residual clusters. However, low interfacial tension results in a larger interfacial area, which is beneficial for dissolution and reaction processes during geological carbon storage. Analysis of the force balance acting on the residual clusters demonstrates that trapping stability is higher in high interfacial tension case, and the interfacial tension should be a controlling factor for the trapping stability in addition to the pore geometry and connectivity. The proposed numerical method can handle the complex displacement of multicomponent systems in porous media. By using this method, we can obtain residual-cluster distributions under different conditions for optimizing the storage capacity of carbon-storage projects. © 2015. American Geophysical Union.
Kamimura S.,Kyushu University |
Yamada H.,Kyushu University |
Yamada H.,Japan National Institute of Advanced Industrial Science and Technology |
Xu C.-N.,Kyushu University |
And 2 more authors.
Applied Physics Letters | Year: 2013
We report photochromism (PC) in Sr2SnO4:Eu 3+ with layered perovskite-related structure. The Sr 2SnO4:Eu3+ turned purple upon irradiation with UV light (λ < 350 nm), and the colored Sr2SnO 4:Eu3+ returned to its initial colorless state when visible light (λ = 400-700 nm) was irradiated. Furthermore, the PC was strongly dependent on the firing temperature; purple color upon UV irradiation can be enhanced by increasing the firing temperature, which was attributed to an increase of the Sr vacancies in the host lattice from the results of crystal structure analysis. This suggests that controlling the lattice defect plays an important role for enhancing the PC performance. © 2013 American Institute of Physics.
Lorenzino P.,Universidad Politécnica de Ingeniería |
Okazaki S.,Kyushu University |
Matsunaga H.,Kyushu University |
Matsunaga H.,International Institute for Carbon Neutral Energy Research WPI I2CNER |
Murakami Y.,Kyushu University
Fatigue and Fracture of Engineering Materials and Structures | Year: 2015
In order to clarify the effect of defect orientation on the fatigue limit of two types of steels, JIS-S15C and JIS-S45C, a small semi-circular slit was introduced onto the surface of a round specimen. The slit was tilted at 0 , 30 or 60 with respect to the plane normal to the loading axis, but all of them had the same defect size, area?=?188 μm, where the area denotes the area of the domain defined by projecting the defect on a plane normal to the loading axis. In all the combinations of the materials and tilt angles, a non-propagating crack was found at or just below the fatigue limit, that is, the fatigue limit was determined by the non-propagation condition of a crack initiated from the defect. In both steels, the fatigue limit was found to be nearly independent of the tilt angle for the same value of projected size area, which was in good agreement with the prediction by the area parameter model. In this paper, a mechanistic explanation for the insensitivity of the fatigue limit to the tilt angle is proposed. © 2015 Wiley Publishing Ltd.
Inoishi A.,Kyushu University |
Sakai T.,Kyushu University |
Ju Y.W.,Kyushu University |
Ida S.,Kyushu University |
And 3 more authors.
Journal of Power Sources | Year: 2014
The effect of operating temperature on the discharge potential and cycle stability of an Fe-air solid oxide rechargeable battery was studied. An Fe-air cell operated at 773 K exhibited the highest discharge potential (1.07 V) and high cycle stability with a current density of 5 mA cm-2. The high discharge potential at lower operating temperatures is due to aggregation of the anode and Fe powder being suppressed. The high redox cycle stability of the Ni-Fe-based anode at 773 K is explained by the small volume change with suppressed aggregation under low-temperature operation. Electrochemical charge-discharge measurements at 773 K revealed excellent cycle stability for 30 cycles with a high energy density (round trip efficiency >80%). © 2014 Elsevier B.V. All rights reserved.
Inoishi A.,Kyushu University |
Ju Y.W.,Kyushu University |
Ida S.,Kyushu University |
Ishihara T.,Kyushu University |
Ishihara T.,International Institute for Carbon Neutral Energy Research WPI I2CNER
Journal of Power Sources | Year: 2013
Solid oxide fuel cell concept was applied for Fe-air rechargeable battery by using H2/H2O as a mediator for Fe redox. Oxygen partial pressure in Fe set chamber during discharge was monitored simultaneously with O2 sensor for analysis of discharge mechanism. On the cell consisting of Pt anode, Y2O3 stabilized ZrO2(YSZ) electrolyte, and Pt cathode, 10 cycles of charge and discharge was stably performed, although decrease in capacity was observed at initial cycle. Oxygen partial pressure (PO2) was monitored by zirconia oxygen sensor which is used for Fe set chamber. Simultaneous monitoring the oxygen partial pressure during the charge and discharge, the reasonable response of PO2 in Fe set chamber was observed and for discharge, Fe seems to be oxidized to FeO and reduction to Fe was also confirmed. Impedance plots suggested that degradation could be assigned to the increased diffusion overpotential because of the decreased oxidation rate of Fe powder. However, after second cycles, internal resistance of the cell was stable up to 10 cycles examined. Therefore, application of SOFC concept and H2/H2O redox mediator is successfully demonstrated for the Fe-air rechargeable battery. © 2012 Elsevier B.V. All rights reserved.
Wang S.,Kyushu University |
Inoishi A.,International Institute for Carbon Neutral Energy Research WPI I2CNER |
Hong J.-E.,International Institute for Carbon Neutral Energy Research WPI I2CNER |
Ju Y.-W.,International Institute for Carbon Neutral Energy Research WPI I2CNER |
And 3 more authors.
Journal of Materials Chemistry A | Year: 2013
A solid oxide electrolysis cell for reducing CO2 to CO was studied using a LaGaO3-based electrolyte at intermediate temperatures (973-1173 K). Various metals were examined as cathodes for CO2 reduction, and it was found that Ni shows high activity. However, coke formation was observed during the initial period. Furthermore, we found that the electrolysis current could be greatly improved by adding Fe to Ni, resulting in a current density of 1.84 A cm-2 at 1.6 V and 1073 K on a Ni-Fe (9:1) cathode. SEM observation suggests that improved cathodic activity can be explained by stabilizing Ni fine particles with the addition of Fe. Therefore, diffusion resistance can be decreased by adding Fe to Ni. The formation rate of CO is slightly lower than the consumption rate of CO2, suggesting coke formation during the initial period. However, stable CO2 electrolysis can be performed for at least 12 h, and Fe addition is effective for increasing long-term stability of electrolysis. © 2013 The Royal Society of Chemistry.
Yamauchi M.,International Institute for Carbon Neutral Energy Research WPI I2CNER |
Ozawa N.,Institute for Materials Research |
Kubo M.,Institute for Materials Research
Chemical Record | Year: 2016
Renewable electricity must be utilized to usefully suppress the atmospheric CO2 concentration and slow the progression of global warming. We have thus proposed a new concept involving CO2-free electric power circulation systems via highly selective electrochemical reactions of alcohol/carboxylic acid redox couples. Design concepts for nanocatalysts able to catalyze highly selective electrochemical reactions are provided from both experimental and quantum mechanical perspectives. © 2016 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.