The Experts below are selected from a list of 6207 Experts worldwide ranked by ideXlab platform
Hector D Abruna - One of the best experts on this subject based on the ideXlab platform.
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multifunctional electrocatalysts ru m m co ni fe for Alkaline Fuel Cells and electrolyzers
ACS Catalysis, 2020Co-Authors: Hongsen Wang, Yao Yang, Francis J Disalvo, Hector D AbrunaAbstract:Moving from proton exchange membrane Fuel Cells to anion exchange membrane Fuel Cells (AEMFCs) enables the use of non-Pt-group (NPG) metals as cathodes for the oxygen reduction reaction, since the ...
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combinatorial studies of palladium based oxygen reduction electrocatalysts for Alkaline Fuel Cells
Journal of the American Chemical Society, 2020Co-Authors: Yao Yang, Rui Zeng, Francis J Disalvo, Guanyu Chen, Andres Molina Villarino, Bruce R Van Dover, Hector D AbrunaAbstract:Hydrogen Fuel Cells have emerged as promising, potentially renewable energy-based, energy conversion technologies for powering electric vehicles. However, the sluggish oxygen reduction reaction (OR...
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octahedral spinel electrocatalysts for Alkaline Fuel Cells
Proceedings of the National Academy of Sciences of the United States of America, 2019Co-Authors: Yao Yang, Yin Xiong, Megan E Holtz, Xinran Feng, Rui Zeng, Gary Chen, Francis J Disalvo, David A Muller, Hector D AbrunaAbstract:Designing high-performance nonprecious electrocatalysts to replace Pt for the oxygen reduction reaction (ORR) has been a key challenge for advancing Fuel cell technologies. Here, we report a systematic study of 15 different AB2O4/C spinel nanoparticles with well-controlled octahedral morphology. The 3 most active ORR electrocatalysts were MnCo2O4/C, CoMn2O4/C, and CoFe2O4/C. CoMn2O4/C exhibited a half-wave potential of 0.89 V in 1 M KOH, equal to the benchmark activity of Pt/C, which was ascribed to charge transfer between Co and Mn, as evidenced by X-ray absorption spectroscopy. Scanning transmission electron microscopy (STEM) provided atomic-scale, spatially resolved images, and high-energy-resolution electron-loss near-edge structure (ELNES) enabled fingerprinting the local chemical environment around the active sites. The most active MnCo2O4/C was shown to have a unique Co-Mn core-shell structure. ELNES spectra indicate that the Co in the core is predominantly Co2.7+ while in the shell, it is mainly Co2+ Broader Mn ELNES spectra indicate less-ordered nearest oxygen neighbors. Co in the shell occupies mainly tetrahedral sites, which are likely candidates as the active sites for the ORR. Such microscopic-level investigation probes the heterogeneous electronic structure at the single-nanoparticle level, and may provide a more rational basis for the design of electrocatalysts for Alkaline Fuel Cells.
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rock salt type mnco2o3 c as efficient oxygen reduction electrocatalysts for Alkaline Fuel Cells
Chemistry of Materials, 2019Co-Authors: Yao Yang, Yin Xiong, Rui Zeng, Francis J Disalvo, Hector D AbrunaAbstract:The search for nonprecious metal-based electrocatalysts with high activity and long durability for the oxygen reduction reaction (ORR) has been long pursued by the renewable energy material community. Here, we designed a new Mn–Co bimetallic oxide MnCo2O3/C with the rock-salt-type structure, derived from a spinel-type precursor MnCo2O4/C under mild reduction using NH3 at 300 °C. In-depth electron microscopic and spectroscopic investigations suggest that MnCo2O3/C predominantly has Mn(II) and Co(II) and can be written as MnO(CoO)2/C. Charge transfer between Mn and Co was probed by electron energy-loss near-edge structure (ELNES) analysis. MnCo2O3/C has a Co-rich core and a thin 1–3 nm Mn shell with a mesoporous morphology. MnCo2O3/C achieved a high ORR activity with a half-wave potential of 0.86 V in 1 M KOH, which was ascribed to the microstructure and the synergistic effects between Mn and Co, serving as co-active sites for the ORR.
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metal organic framework derived co fe bimetallic oxygen reduction electrocatalysts for Alkaline Fuel Cells
Journal of the American Chemical Society, 2019Co-Authors: Yin Xiong, Yao Yang, Francis J Disalvo, Hector D AbrunaAbstract:The oxygen reduction reaction (ORR) is considered the cornerstone for regenerative energy conversion devices involving Fuel Cells and electrolyzers. The development of non-precious-metal electrocat...
Yanxun Fu - One of the best experts on this subject based on the ideXlab platform.
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novel silica poly 2 6 dimethyl 1 4 phenylene oxide hybrid anion exchange membranes for Alkaline Fuel Cells effect of heat treatment
Journal of Membrane Science, 2009Co-Authors: Yonghui Wu, Cuiming Wu, Tongwen Xu, Yanxun FuAbstract:Abstract A series of silica/poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) anion exchange hybrid membranes are prepared. PPO is modified by bromination, hydroxylation and quaternization in sequence. Subsequent sol–gel reaction with monophenyl triethoxysilane (EPh) and tetraethoxysilane (TEOS), followed by heat treatment at 120–140 °C for different times, yields the hybrid membranes. Results show that the physico-chemical properties of the membranes, including ion exchange property, hydrophilicity, OH − conductivity and tensile property, can be easily controlled by adjusting the heating temperature and time. The membranes have proper conductivity (up to 0.0085 S/cm) and favorable tensile properties. The tensile strength (TS) can be higher than 20 MPa and the elongation at break ( E b ) is in the range of 5.5–19.5%. Besides, the chemical stability in alkali conditions and thermal stability are comparable to those of anion-exchange membranes based on (partially) fluorinated-polymer. Hence, the hybrid membranes are suitable for potential application in Alkaline Fuel Cells.
Keith Scott - One of the best experts on this subject based on the ideXlab platform.
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direct oxidation Alkaline Fuel Cells from materials to systems
Energy and Environmental Science, 2012Co-Authors: Xu Wang, Ulrike Krewer, Keith ScottAbstract:Direct oxidation Alkaline Fuel Cells (DOAFCs) possess particular advantages on the possibility of employing low cost non-noble metal catalysts. A wide range of Fuels can be used due to superior reaction kinetics in Alkaline media. The development of DOAFCs was hindered by the carbonation of electrolyte due to the presence of CO2. The application of the anion exchange membrane (AEM) provides the possibility of reducing the effect of carbonation and Fuel crossover which is an issue in the proton exchange membrane Fuel Cells (PEMFCs). The latest developments in Alkaline Fuel Cells are examined in this paper, considering different types of Fuels, novel catalysts and anion exchange membranes. Moreover, Alkaline Fuel cell systems and configurations are studied, particularly the new designs for portable or microelectronic devices. Further development of DOAFCs will rely on novel AEMs with good ionic conductivity and stability, low cost non-Pt catalysts with high activity and good stability for various Fuels and oxidant. We envisage that DOAFCs will play a major role in energy research and applications in the near future.
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Direct methanol Alkaline Fuel Cells with catalysed anion exchange membrane electrodes
Journal of Applied Electrochemistry, 2005Co-Authors: Eileen Hao Yu, Keith ScottAbstract:Membrane electrodes prepared by chemical deposition of platinum directly onto the anion exchange membrane electrolyte were tested in direct methanol Alkaline Fuel Cells. Data on the cell voltage against current density performance and anode potentials are reported. The relatively low Fuel cell performance was probably due to the low active surface area of Pt deposits on the membrane comparing to other membrane electrode assembly (MEA) fabrication methods. However, the catalysed membrane electrode showed good performance for oxygen reduction. A reduction in cell internal resistance was also obtained for the catalysed membrane electrode. By combining the catalysed membrane electrodes with a catalysed mesh, maximum current density of 98 mA cm−2 and peak power density of 18 mW cm−2 were achieved.
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development of direct methanol Alkaline Fuel Cells using anion exchange membranes
Journal of Power Sources, 2004Co-Authors: Keith ScottAbstract:Research into the development of direct methanol Alkaline Fuel cell (DMAFC) using an anion exchange polymer electrolyte membrane is described. The commercial membrane used had a higher electric resistance, but a lower methanol diffusion coefficient than Nafion® membranes. Fuel cell tests were performed using carbon supported Pt catalyst, and the effect of temperature, methanol concentration, methanol flow rate, air pressure and Pt loading were investigated. It was found that the cell performance improved drastically with a membrane assembly electrode (MEA) which did not include the gas diffusion layer on the anode, because of lower reactant mass transfer resistance. To give suitable cathode performance, humidification of the air and a subtle balance between the air pressure and water transport is required.
Nanwen Li - One of the best experts on this subject based on the ideXlab platform.
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quaternized poly 2 6 dimethyl 1 4 phenylene oxide anion exchange membranes based on isomeric benzyltrimethylammonium cations for Alkaline Fuel Cells
Journal of Membrane Science, 2020Co-Authors: Chenyang Shao, Rou Chen, Peiwei Zhao, Nanwen LiAbstract:Abstract Benzyltrimethylammonium (BTMA) is most frequently-used organic cations in anion exchange membrane (AEM) materials. However, BTMA-based AEMs always suffer from low ionic conductivity and insufficient Alkaline stability for practical Alkaline Fuel Cells. Here, we present a systematic investigation of a series of side-chain-type poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) AEMs with constitutional isomerism in BTMA cations. Three isomeric BTMA cations, e.g. meta-BTMA, ortho-BTMA, and para-BTMA, were tethered onto PPO backbones via a flexible spacer using CuAAC reaction, producing side-chain-type AEMs, namely m-QPPO, o-QPPO, and p-QPPO membranes, respectively. As expected, side-chain-type PPO AEMs displayed higher hydroxide conductivity as compared to a control PPO-QA membrane where BTMA cations were directly linked on PPO backbones, due to the microphase-separated morphologies as confirmed by small-angle X-ray scattering (SAXS) results. Although these isomeric quaternized PPO copolymers had identical chemical composition and polymer architectures, they did not share similar properties. Specifically, among three side-chain-type AEMs, the highest hydroxide conductivity of 42.8 mS/cm was observed for m-QPPO membrane having meta-BTMA cations with an ion exchange capacity of 1.93 meq./g at 20 °C, as a result of its high water uptake. In addition to high conductivity, m-QPPO membrane showed superior Alkaline stability with respect to o-QPPO and p-QPPO membranes. After 200 h of aging in 1 M NaOH at 60 °C, 85% of the hydroxide conductivity was retained for m-QPPO AEMs, while more than 30% conductivity loss was observed for o-QPPO and p-QPPO membranes. NMR analysis of the aged membrane suggested that SN2 nucleophilic substitution at benzyl groups is the dominant degradation mechanisms. Furthermore, the AEM Fuel Cells using these PPO AEMs with isomeric BTMA cations were investigated, and the cell with highly conductive and durable m-QPPO membranes exhibited the best performance with a peak power density of 333 mW/cm2 at a current density of 700 mA/cm2 at 60 °C, comparable to other AEMFCs with PPO-based AEMs. Consequently, this work not only provides a facile and effective strategy to precisely synthesize isomeric AEMs, but also contributes to fundamental insights into the structure-property relationship as well as Alkaline Fuel cell performance for these isomeric BTMA-based AEMs, which are not explored before.
Qing Lin Liu - One of the best experts on this subject based on the ideXlab platform.
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phenolphthalein based poly arylene ether sulfone nitrile s multiblock copolymers as anion exchange membranes for Alkaline Fuel Cells
ACS Applied Materials & Interfaces, 2015Co-Authors: Ao Nan Lai, Li Sha Wang, Chen Xiao Lin, Yizhi Zhuo, Qiu Gen Zhang, Ai Mei Zhu, Qing Lin LiuAbstract:A series of phenolphthalein-based poly(arylene ether sulfone nitrile)s (PESN) multiblock copolymers containing 1–methylimidazole groups (ImPESN) were synthesized to prepare anion exchange membranes (AEMs) for Alkaline Fuel Cells. The ion groups were introduced selectively and densely on the unit of phenolphthalein as the hydrophilic segments, allowing for the formation of ion clusters. Strong polar nitrile groups were introduced into the hydrophobic segments with the intention of improving the dimensional stability of the AEMs. A well-controlled multiblock structure was responsible for the well-defined hydrophobic/hydrophilic phase separation and interconnected ion–transport channels, as confirmed by atomic force microscopy and small angle X-ray scattering. The ImPESN membranes with low swelling showed a relatively high water uptake, high hydroxide ion conductivity together with good mechanical, thermal and Alkaline stability. The ionic conductivity of the membranes was in the range of 3.85–14.67 × 10–2 S...
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quaternized cardo polyetherketone anion exchange membrane for direct methanol Alkaline Fuel Cells
Journal of Power Sources, 2009Co-Authors: Ying Xiong, Qing Lin Liu, Qing-hua ZengAbstract:Abstract Quaternized cardo polyetherketone (QPEK-C) membranes for Alkaline Fuel Cells were prepared via chloromethylation, quaternization and alkalization of cardo polyetherketone (PEK-C). The chemical reaction for PEK-C modification was confirmed by nuclear magnetic resonance ( 1 H NMR) and energy-dispersive X-ray spectroscopy (EDAX). The QPEK-C membrane was characterized by X-ray photoelectron spectroscopy (XPS) and thermo gravimetric analysis (TG). The ion-exchange content (IEC), water and methanol uptakes, methanol permeability and conductivity of the QPEK-C membranes were measured to evaluate their applicability in Alkaline methanol Fuel Cells. The ionic conductivity of the QPEK-C membrane varied from (1.6 to 5.1) × 10 −3 S cm −2 over the temperature range 20–60 °C. The QPEK-C membrane showed excellent methanol resistance. When the concentration of methanol was 4 M, the methanol permeability was less than 10 −9 cm 2 s −1 at 30 °C.