The Experts below are selected from a list of 6891 Experts worldwide ranked by ideXlab platform
Jingtao Wang - One of the best experts on this subject based on the ideXlab platform.
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porous nafion nanofiber composite membrane with vertical pathways for efficient through plane Proton Conduction
Journal of Membrane Science, 2019Co-Authors: Jingtao Wang, Yafang Zhang, Yarong Liu, Jindun LiuAbstract:Abstract Nafion has been the benchmark of Proton exchange membrane for decades due to the excellent Proton Conduction and physicochemical properties. While the strong dependence of transfer channel continuity on humidity always causes serious conductivity drops and hampers the wide application. Herein, a combination of electrospinning and soft template (ionic liquid) methods is proposed to fabricate porous Nafion nanofiber. The resultant nanofiber mat is then impregnated with chitosan (CS) to prepare porous nanofiber composite membrane (PNFCM). This is different from traditional nanofiber composite membrane (NFCM), of which through-plane conductivity is much lower than in-plane one (i.e., strong transfer anisotropy). The abundant pores inside porous nanofibers provide numerous vertical transfer channels at interfaces between CS and pore walls. Meanwhile, the –NH/–NH2 groups on CS form acid-base pairs with –SO3H groups along pore walls. These stable vertical pathways significantly facilitate the through-plane Proton Conduction at both hydrated and anhydrous conditions. Particularly, PNFCM attains perpendicular conductivities of 307 mS cm−1 at 90 °C and 100% RH, and 150 mS cm−1 at 120 °C and 0% RH, which are, respectively, 3.2 and 2.7 times of that of NFCM. Consequently, the transfer anisotropy coefficient decreases and fuel cell performances enhance obviously.
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constructing long range transfer pathways with ordered acid base pairs for highly enhanced Proton Conduction
ACS Applied Materials & Interfaces, 2019Co-Authors: Yarong Liu, Jianlong Lin, Zhihao Yang, Jingtao WangAbstract:Acid-base pairs hold great superiority in creating Proton defects and facilitating Proton transfer with less or no water. However, the existing acid-base complexes fail in assembling into ordered acid-base pairs and thus cannot always take full advantage of the acid-base synergetic effect. Herein, polymer quantum dots with inherent ordered acid-base pairs are utilized and anchored on dopamine-coated graphene oxide, thus forming into long-range conducting pathways. The resultant building blocks ( nPGO) are integrated in a sulfonated poly(ether ether ketone) matrix to fabricate composite membranes. The constructed long-range transfer highways with ordered acid-base pairs impart to the composite membrane significantly enhanced Proton Conduction ability. Under the hydrated state, the composite membrane attains 91% increase over the control membrane in conductivity, and the single-cell fuel based on the membrane achieves 71% promotion in maximum power density. Under anhydrous conditions, more striking augment in Conduction is observed for the composite membrane, reaching 7.14 mS cm-1, almost 10 times of the control membrane value (0.78 mS cm-1). Remarkably, such anhydrous Proton Conduction performance is even comparable to that of the composite membrane impregnated with ionic liquids, which is hard to realize with conventional fillers. Collectively, these results endow composite membranes great potential for applications in hydrogen-based fuel cells, sensors, and catalysis.
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molecular level hybridization of nafion with quantum dots for highly enhanced Proton Conduction
Advanced Materials, 2018Co-Authors: Jindun Liu, Jingtao Wang, Shizhang Qiao, Kenneth DaveyAbstract:Nanophase-separated membranes hold promise for fast molecule or ion transfer. However, development and practical application are significantly hindered by both the difficulty of chemical modification and nanophase instability. This can be addressed by organic-inorganic hybridization of functional fillers with a precise distribution in specific nanophase. Here, a molecular-level hybridization for nanophase-separated Nafion using 2-5 nm quantum dots (QDs) as a new smart filler is demonstrated. Two kinds of QDs are prepared and used: hydrophilic polymer-like QDs (PQDs) and hydrophobic graphene oxide QDs (GQDs). Because of selective interactions, QDs offer advantages of matched structural size and automatic recognition with the nanophase. A distinctive synthesis of subordinate-assembly, in which QDs are driven by the self-assembly of Nafion affinity chains, is reported. This results in a precise distribution of QDs in the ionic, or backbone, nanophases of Nafion. The resulting PQDs in the ionic nanophase significantly increase membrane Proton Conduction and device output-power without loss of mechanical stability. This is difficult to realize with conventional fillers. The GQDs in the backbone nanophase reduce the crystallinity and significantly augment membrane water uptake and swelling capacities.
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imidazole microcapsules toward enhanced phosphoric acid loading of polymer electrolyte membrane for anhydrous Proton Conduction
Journal of Membrane Science, 2018Co-Authors: Jingchuan Dang, Jingtao Wang, Jindun Liu, Liping Zhao, Jie ZhangAbstract:Abstract Polymer electrolyte membrane (PEM) with high loading, stable ion solvents remains challenging at present and significantly impedes its practical application in energy-relevant devices including hydrogen fuel cell. Here, a series of imidazole microcapsules (ImMCs) are synthesized and utilized as distinct reservoirs to access high phosphoric acid retention for PEM. We demonstrate that the ImMCs can significantly enhance the acid loading capability using the large lumens, bringing abundant Proton-hopping sites and hence significantly enhanced Proton Conduction of membrane. In particular, 10 wt% ImMCs can afford a 78 wt% phosphoric acid loading and a consequent 75 times' increase of Proton conductivity relative to the control membrane. Additionally, the cross-linked imidazole shells render membrane high acid retention ability. The acid release is almost stopped after immersing in water for 40 min, helping the membrane to retain as high as 62% of the initially loaded phosphoric acid. These features readily impart notably boosted hydrogen fuel cell performances to composite membrane under the desired conditions of elevated temperature and reduced humidity. As a further description, the acid retention and Proton Conduction properties of membrane can be efficiently tailored by adjusting microcapsule architectures (lumen size and shell thickness).
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embedding sulfonated lithium ion sieves into polyelectrolyte membrane to construct efficient Proton Conduction pathways
Journal of Membrane Science, 2016Co-Authors: Jingtao Wang, Wenjia Wu, Haoqin Zhang, Zhongjun Li, Yifan Li, Xiang ZhangAbstract:Abstract In this study, acidified lithium ion-sieves (HMOs) containing unique inner ionic channels suitable for the transfer of H + are selected as Proton-conductive fillers to prepare hybrid membranes for the first time. By using facile distillation-precipitation polymerization process, two types of sulfonated HMOs (SHMOs) are prepared: L-SHMOs, which are modified by sulfonate polyelectrolyte layer, and B-SHMOs, which are sulfonate polyelectrolyte brushes. The results demonstrate that these fillers improve the thermal and mechanical stabilities of chitosan (CS) control membranes. The incorporation of pristine HMOs enhances the water uptakes and Proton Conduction abilities of hybrid membranes at suitable loading. By comparison, SHMOs-filled membranes possess higher Proton conductivities than those of HMO-filled membranes, owing to the additional Proton hopping sites of –SO 3 H and acid-base pairs (–SO 3 − ··· + 3 HN–). Moreover, B-SHMO-filled membranes exhibit superior Proton conductivities over L -SHMO-filled ones, demonstrating that the polymer brushes on HMOs allow more –SO 3 H groups to form acid-base pairs with CS chains. Particularly, CS/B-SHMO-12 obtains the highest hydrated and anhydrous conductivities of 0.0224 S cm −1 and 10.03 mS cm −1 , enhancing by 91.4% and 98.6% respectively compared with those of CS control membrane under identical conditions. The enhanced Proton conductivities offer SHMO-filled membranes elevated cell performances.
George K H Shimizu - One of the best experts on this subject based on the ideXlab platform.
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single crystal Proton Conduction study of a metal organic framework of modest water stability
Journal of the American Chemical Society, 2017Co-Authors: Biplab Joarder, Jianbin Lin, Zaida Romero, George K H ShimizuAbstract:A sulfonated indium (In) metal organic framework (MOF) is reported with an anionic layered structure incorporating hydrogen-bonded dimethylammonium cations and water molecules. The MOF becomes amorphous in >60% relative humidity; however, impedance analysis of pelletized powders revealed a Proton Conduction value of over 10–3 S cm–1 at 25 °C and 40% RH, a very high Proton Conduction value for low humidity and moderate temperature. Given the modest humidity stability of the MOF, triaxial impedance analyses on a single crystal was performed and confirmed bulk Proton conductivity over 10–3 S cm–1 along two axes corroborating the data from the pellet.
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Proton Conduction with metal organic frameworks
Science, 2013Co-Authors: George K H Shimizu, Jared M Taylor, Sirim KimAbstract:Proton-exchange membrane fuel cells (PEMFCs) generate electricity because the electrons generated by the reaction of hydrogen and oxygen must travel through an external circuit; the membrane electrolyte only transfers Protons. The membrane materials of choice have been ionomeric polymers, such as sulfonated fluoropolymers (Nafion), that achieve Proton conductivities of up to 1 S cm−1, but the requirement to keep these materials hydrated limits their operating temperature and efficiency. Metal-organic frameworks (MOFs), in which inorganic assemblies are joined by organic linkers, have inherent porosity that could be exploited for the development of Proton-conducting membranes. Among recent studies of experimental Proton-conducting MOFs [e.g., ( 1 )], two general targets for PEMFC operation have emerged: developing better materials for operations under humid conditions (below 100°C), and developing efficient anhydrous Proton conductors that could unlock the cost efficiencies enabled by humidity-independent operation above 100°C.
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enhancing Proton Conduction in a metal organic framework by isomorphous ligand replacement
Journal of the American Chemical Society, 2013Co-Authors: Sirim Kim, Jared M Taylor, Karl W Dawson, Benjamin S Gelfand, George K H ShimizuAbstract:Using the concept of isomorphous replacement applied to entire ligands, a C3-symmetric trisulfonate ligand was substituted with a C3-symmetric tris(hydrogen phosphonate) ligand in a Proton conducting metal–organic framework (MOF). The resulting material, PCMOF21/2, has its Proton Conduction raised 1.5 orders of magnitude compared to the parent material, to 2.1 × 10–2 S cm–1 at 90% relative humidity and 85 °C, while maintaining the parent MOF structure.
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facile Proton Conduction via ordered water molecules in a phosphonate metal organic framework
Journal of the American Chemical Society, 2010Co-Authors: Jared M Taylor, Roger K Mah, Igor L Moudrakovski, Christopher I Ratcliffe, Ramanathan Vaidhyanathan, George K H ShimizuAbstract:A new phosphonate metal−organic framework (MOF) with a layered motif but not that of the classical hybrid inorganic−organic solid is presented. Zn3(L)(H2O)2·2H2O (L = [1,3,5-benzenetriphosphonate]6−), henceforth denoted as PCMOF-3, contains a polar interlayer lined with Zn-ligated water molecules and phosphonate oxygen atoms. These groups serve to anchor free water molecules into ordered chains, as observed by X-ray crystallography. The potential for Proton Conduction via the well-defined interlayer was studied by 2H solid-state NMR spectroscopy and AC impedance spectroscopy. The Proton conductivity in H2 was measured as 3.5 × 10−5 S cm−1 at 25 °C and 98% relative humidity. More interestingly, an Arrhenius plot gave a low activation energy of 0.17 eV for Proton transfer, corroborating the solid-state NMR data that showed exchange between all deuterium sites in the D2O analogue of PCMOF-3, even at −20 °C.
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anhydrous Proton Conduction at 150 c in a crystalline metal organic framework
Nature Chemistry, 2009Co-Authors: Jeff A Hurd, Venkataraman Thangadurai, Igor L Moudrakovski, Christopher I Ratcliffe, Ramanathan Vaidhyanathan, George K H ShimizuAbstract:Metal organic frameworks (MOFs) are particularly exciting materials that couple porosity, diversity and crystallinity. But although they have been investigated for a wide range of applications, MOF chemistry focuses almost exclusively on properties intrinsic to the empty frameworks; the use of guest molecules to control functions has been essentially unexamined. Here we report Na(3)(2,4,6-trihydroxy-1,3,5-benzenetrisulfonate) (named β-PCMOF2), a MOF that conducts Protons in regular one-dimensional pores lined with sulfonate groups. Proton Conduction in β-PCMOF2 was modulated by the controlled loading of 1H-1,2,4-triazole (Tz) guests within the pores and reached 5 × 10(-4) S cm(-1) at 150 °C in anhydrous H(2), as confirmed by electrical measurements in H(2) and D(2), and by solid-state NMR spectroscopy. To confirm its potential as a gas separator membrane, the partially loaded MOF (β-PCMOF2(Tz)(0.45)) was also incorporated into a H(2)/air membrane electrode assembly. The resulting membrane proved to be gas tight, and gave an open circuit voltage of 1.18 V at 100 °C.
Jared M Taylor - One of the best experts on this subject based on the ideXlab platform.
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confined water mediated high Proton Conduction in hydrophobic channel of a synthetic nanotube
Nature Communications, 2020Co-Authors: Kenichi Otake, Kazuya Otsubo, Tokutaro Komatsu, Shun Dekura, Jared M Taylor, Ryuichi Ikeda, Kunihisa SugimotoAbstract:Water confined within one-dimensional (1D) hydrophobic nanochannels has attracted significant interest due to its unusual structure and dynamic properties. As a representative system, water-filled carbon nanotubes (CNTs) are generally studied, but direct observation of the crystal structure and Proton transport is difficult for CNTs due to their poor crystallinity and high electron Conduction. Here, we report the direct observation of a unique water-cluster structure and high Proton Conduction realized in a metal-organic nanotube, [Pt(dach)(bpy)Br]4(SO4)4·32H2O (dach: (1R, 2R)-(–)-1,2-diaminocyclohexane; bpy: 4,4’-bipyridine). In the crystalline state, a hydrogen-bonded ice nanotube composed of water tetramers and octamers is found within the hydrophobic nanochannel. Single-crystal impedance measurements along the channel direction reveal a high Proton Conduction of 10−2 Scm−1. Moreover, fast Proton diffusion and continuous liquid-to-solid transition are confirmed using solid-state 1H-NMR measurements. Our study provides valuable insight into the structural and dynamical properties of confined water within 1D hydrophobic nanochannels. Water confined in natural or synthetic hydrophobic nano-spaces behaves differently than in the bulk. Here the authors investigate water in hydrophobic synthetic 1D nanochannels revealing water clustering in tetramers and octamers and high Proton conductivity, along with a continuous liquid to solid transition.
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a metal organic framework impregnated with a binary ionic liquid for safe Proton Conduction above 100 c
Chemistry: A European Journal, 2017Co-Authors: Xiaoli Sun, Jared M Taylor, Weihua Deng, Hui Chen, Hongliang Han, Chongqing WanAbstract:To develop Proton conducting materials under low humidity condition and moderate working temperature still remains challenging for fuel-cell technology. Herein, we show a new type of Proton-conducting material, EIMS-HTFSA@MIL, which was prepared by impregnating binary ionic liquids, EIMS-HTFSA, into mesoporous metal-organic framework, MIL-101. Taking advantages of the ionic liquid, such as high thermal stability, non-volatility, non-flammability and low corrosivity, EIMS-HTFSA@MIL shows potential application on Proton Conduction above 100 oC as a safe electrolyte.
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Proton Conduction with metal organic frameworks
Science, 2013Co-Authors: George K H Shimizu, Jared M Taylor, Sirim KimAbstract:Proton-exchange membrane fuel cells (PEMFCs) generate electricity because the electrons generated by the reaction of hydrogen and oxygen must travel through an external circuit; the membrane electrolyte only transfers Protons. The membrane materials of choice have been ionomeric polymers, such as sulfonated fluoropolymers (Nafion), that achieve Proton conductivities of up to 1 S cm−1, but the requirement to keep these materials hydrated limits their operating temperature and efficiency. Metal-organic frameworks (MOFs), in which inorganic assemblies are joined by organic linkers, have inherent porosity that could be exploited for the development of Proton-conducting membranes. Among recent studies of experimental Proton-conducting MOFs [e.g., ( 1 )], two general targets for PEMFC operation have emerged: developing better materials for operations under humid conditions (below 100°C), and developing efficient anhydrous Proton conductors that could unlock the cost efficiencies enabled by humidity-independent operation above 100°C.
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enhancing Proton Conduction in a metal organic framework by isomorphous ligand replacement
Journal of the American Chemical Society, 2013Co-Authors: Sirim Kim, Jared M Taylor, Karl W Dawson, Benjamin S Gelfand, George K H ShimizuAbstract:Using the concept of isomorphous replacement applied to entire ligands, a C3-symmetric trisulfonate ligand was substituted with a C3-symmetric tris(hydrogen phosphonate) ligand in a Proton conducting metal–organic framework (MOF). The resulting material, PCMOF21/2, has its Proton Conduction raised 1.5 orders of magnitude compared to the parent material, to 2.1 × 10–2 S cm–1 at 90% relative humidity and 85 °C, while maintaining the parent MOF structure.
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facile Proton Conduction via ordered water molecules in a phosphonate metal organic framework
Journal of the American Chemical Society, 2010Co-Authors: Jared M Taylor, Roger K Mah, Igor L Moudrakovski, Christopher I Ratcliffe, Ramanathan Vaidhyanathan, George K H ShimizuAbstract:A new phosphonate metal−organic framework (MOF) with a layered motif but not that of the classical hybrid inorganic−organic solid is presented. Zn3(L)(H2O)2·2H2O (L = [1,3,5-benzenetriphosphonate]6−), henceforth denoted as PCMOF-3, contains a polar interlayer lined with Zn-ligated water molecules and phosphonate oxygen atoms. These groups serve to anchor free water molecules into ordered chains, as observed by X-ray crystallography. The potential for Proton Conduction via the well-defined interlayer was studied by 2H solid-state NMR spectroscopy and AC impedance spectroscopy. The Proton conductivity in H2 was measured as 3.5 × 10−5 S cm−1 at 25 °C and 98% relative humidity. More interestingly, an Arrhenius plot gave a low activation energy of 0.17 eV for Proton transfer, corroborating the solid-state NMR data that showed exchange between all deuterium sites in the D2O analogue of PCMOF-3, even at −20 °C.
Zhongyi Jiang - One of the best experts on this subject based on the ideXlab platform.
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combined intrinsic and extrinsic Proton Conduction in robust covalent organic frameworks for hydrogen fuel cell applications
Angewandte Chemie, 2020Co-Authors: Yi Yang, Zhongyi Jiang, Penghui Zhang, Yassin H Andaloussi, Hailu Zhang, Yao Chen, Peng Cheng, Zhenjie ZhangAbstract:Developing new materials for the fabrication of Proton exchange membranes (PEMs) for fuel cells is of great significance. Herein, a series of highly crystalline, porous, and stable new covalent organic frameworks (COFs) have been developed by a stepwise synthesis strategy. The synthesized COFs exhibit high hydrophilicity and excellent stability in strong acid or base (e.g., 12 m NaOH or HCl) and boiling water. These features make them ideal platforms for Proton Conduction applications. Upon loading with H3 PO4 , the COFs (H3 PO4 @COFs) realize an ultrahigh Proton conductivity of 1.13×10-1 S cm-1 , the highest among all COF materials, and maintain high Proton conductivity across a wide relative humidity (40-100 %) and temperature range (20-80 °C). Furthermore, membrane electrode assemblies were fabricated using H3 PO4 @COFs as the solid electrolyte membrane for Proton exchange resulting in a maximum power density of 81 mW cm-2 and a maximum current density of 456 mA cm-2 , which exceeds all previously reported COF materials.
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constructing facile Proton Conduction pathway within sulfonated poly ether ether ketone membrane by incorporating poly phosphonic acid silica nanotubes
Journal of Power Sources, 2014Co-Authors: Lingli Nie, Xi Han, Hao Dong, Zhongyi JiangAbstract:Abstract The objective of this study is to exploit the one-dimension structure and good Proton Conduction of phosphorylated silica nanotubes for high Proton conductivity of Proton exchange membrane (PEM). Three types of poly(vinylphosphonic acid-co-divinylbenzene)/silica nanotubes with different aspect ratios are synthesized and incorporated into the sulfonated poly(ether ether ketone) (SPEEK) matrix to prepare composite membranes. The poly(vinylphosphonic acid) segments in the nanotubes could construct facile Proton-Conduction pathway along this one-dimensional nanostructure. The nanotubes with high aspect ratio exhibit more pronounced effect in elevating the Proton conductivity of membranes, revealing the importance of continuity of Conduction pathway on Proton transport. The membrane incorporated with the nanotubes of the largest aspect ratio of 45.9 exhibits the highest Proton conductivity of 0.1032 S cm−1 at 30 °C, 100% RH, which was 84% higher than that of SPEEK control membrane. Moreover, the nanotubes can reduce the methanol permeability, and improve mechanical stability of the membranes.
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zwitterionic microcapsules as water reservoirs and Proton carriers within a nafion membrane to confer high Proton conductivity under low humidity
ACS Applied Materials & Interfaces, 2014Co-Authors: Xinlin Yang, Zhongyi JiangAbstract:Zwitterionic microcapsules (ZMCs) based on sulfobetaine with tunable hierarchical structures, superior water retention properties, and high Proton Conduction capacities are synthesized via precipitation polymerization. The incorporation of ZMCs into a Nafion matrix renders the composite membranes with significantly enhanced Proton conductivity especially under low humidity. The composite membrane with 15 wt % ZMC-I displayed the highest Proton conductivity of 5.8 × 10–2 S cm–1 at 40 °C and 20% relative humidity after 90 min of testing, about 21 times higher than that of the Nafion control membrane. The increased Proton conductivity is primarily attributed to the versatile roles of ZMCs as water reservoirs and Proton conductors for rendering a stable water environment and an additional Proton Conduction pathway within the membranes. This study may contribute to the rational design of water-retaining and Proton-conducting materials.
K D Kreuer - One of the best experts on this subject based on the ideXlab platform.
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the mechanism of Proton Conduction in phosphoric acid
Nature Chemistry, 2012Co-Authors: Linas Vilciauskas, Stephen J Paddison, Mark E Tuckerman, Gabriel Bester, K D KreuerAbstract:Neat liquid phosphoric acid (H(3)PO(4)) has the highest intrinsic Proton conductivity of any known substance and is a useful model for understanding Proton transport in other phosphate-based systems in biology and clean energy technologies. Here, we present an ab initio molecular dynamics study that reveals, for the first time, the microscopic mechanism of this high Proton conductivity. Anomalously fast Proton transport in hydrogen-bonded systems involves a structural diffusion mechanism in which intramolecular Proton transfer is driven by specific hydrogen bond rearrangements in the surrounding environment. Aqueous media transport excess charge defects through local hydrogen bond rearrangements that drive individual Proton transfer reactions. In contrast, strong, polarizable hydrogen bonds in phosphoric acid produce coupled Proton motion and a pronounced protic dielectric response of the medium, leading to the formation of extended, polarized hydrogen-bonded chains. The interplay between these chains and a frustrated hydrogen-bond network gives rise to the high Proton conductivity.
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on the complexity of Proton Conduction phenomena
Solid State Ionics, 2000Co-Authors: K D KreuerAbstract:Abstract The Proton transport mechanisms in systems containing water and in cubic perovskite-type oxides are analyzed in detail in terms of chemical interactions. Some features of Proton transport in hydroxides and systems containing oxo-acid anions or heterocycles as Proton solvents are also described. Despite the differences between the rather complex Proton Conduction mechanisms in these systems, significant structural and dynamical variations of hydrogen bond interactions as a result of a good balance of chemical interactions in a wide range of configuration space have been identified as common features. These allow for high rates of Proton transfer and structural reorganization, the two reactions involved in long-range Proton transport. From the analyses and additional information on mesoscopic effects, suggestions are also made for the optimization of the mobility of Protonic defects in hydrated, acidic polymers and perovskite-type oxides, which are interesting as separator materials for fuel cells. For the former, the importance of the microstructure is emphasized, while, for the latter, the prospects for III–III perovskites are stressed.
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Proton conductivity materials and applications
Chemistry of Materials, 1996Co-Authors: K D KreuerAbstract:In this review the phenomenon of Proton conductivity in materials and the elements of Proton Conduction mechanismsProton transfer, structural reorganization and diffusional motion of extended moietiesare discussed with special emphasis on Proton chemistry. This is characterized by a strong Proton localization within the valence electron density of electronegative species (e.g., oxygen, nitrogen) and self-localization effects due to solvent interactions which allows for significant Proton diffusivities only when assisted by the dynamics of the Proton environment in Grotthuss and vehicle type mechanisms. In systems with high Proton density, Proton/Proton interactions lead to Proton ordering below first-order phase transition rather than to coherent Proton transfers along extended hydrogen-bond chains as is frequently suggested in textbooks of physical chemistry. There is no indication for significant Proton tunneling in fast Proton Conduction phenomena for which almost barrierless Proton transfer is suggest...
