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[en] Highlights: • A catalytic approach is used to optimize proton conductivity of LCNO electrolytes. • Exsolution of Ni nanoparticles is achieved by heating under reducing atmosphere. • Ni nanocatalysts significantly improve the proton conductivity of LCNO electrolytes.
[en] Highlights: • Nafion modified carbon dots (NCDs) with multi-functional groups were successfully synthesized. • The aggregation structure of the Nafion matrix was adjusted by NCDs. • NCD Nafion composite PEMs present a 5–10 times increase in proton conductivity compared to recast Nafion. • The methanol permeability of the NCD Nafion composite PEMs is effectively decreased. - Abstract: It is of great necessity to achieve a proton exchange membrane (PEM) with high proton conductivity and low methanol permeability for the practical applications. Nafion modified carbon dots (NCDs) with multi-functional groups were successfully synthesized via the pyrolysis of citric acid (CA) with the existence of Nafion. The modification process is motivated by the hydrophilicity-to-hydrophobicity transformation of CA as well as the non-covalent hydrophilic-hydrophobic interaction during the pyrolysis procedure. Multi-functionalized NCDs with moderate hydrophilicity influence the aggregation structure of Nafion matrix of the composite membranes and effectively enhance the high-temperature water retention ability. Both the proton conductivity and the methanol resistance ability of the composite PEMs are significantly enhanced. 0.5-NCD-0.5 Nafion composite PEM presents a 5–10 times increase in proton conductivity and 50% percent decrease in methanol permeability than that of recast Nafion.
[en] In this study, we synthesized a molecular hybrid conductor electrolyte using PWA ([H3PW12O40.nH2O]) and [1-butyl-3-methylimidazole][bis-(fluoromethanesulfonyl) amide] ([BMIM][TFSI]) ionic liquid. The [BMIM][TFSI] ionic liquid can interact with the strongly acidic PWA. The hybrids were hydrophilic, and included some water molecules in the structure of the hybrids. The water molecules remained up to 80 deg. C, contributing to improve conductivity under an anhydrous N2 atmosphere. The conductivity of PWA-[BMIM][TFSI] hybrid under anhydrous conditions increased from 10-4 S/cm to 0.04 S/cm at 60 deg. C. The conductivity of the hybrids at each temperature was higher than that of pure PWA and [BMIM][TFSI] under anhydrous condition. It can be due to the protonic carriers
[en] Anhydrous proton conducting membranes based on sulfonated polyimide (sPI) and imidazole derivatives were prepared. The acid-base composite membranes show a good chemical oxidation stability and high thermal stability. The addition of imidazole derivatives in sPIs can improve the chemical oxidation stability of the composite membranes enormously, and even much better than that of pure sPI. The proton conductivity of a typical sPI/xUI(2-undecylimidazole) composite membrane can reach 10-3 S cm-1 at 180 deg. C under the anhydrous condition. The proton conductivity of the acid-base composite membranes increases significantly with increasing content of UI. Moreover, UI in sPI/xUI composite membrane is difficult to be brought out by the vapor due to the existence of long hydrophobic moiety, which will improve the stability and lifetime of the membranes in the fuel cells
[en] Heterogeneities such as point defects, inherent to material systems, can profoundly influence material functionalities critical for numerous energy applications. This influence in principle can be identified and quantified through development of large defect data sets which we call the defect genome, employing high-throughput ab initio calculations. However, high-throughput screening of material models with point defects dramatically increases the computational complexity and chemical search space, creating major impediments toward developing a defect genome. In this paper, we overcome these impediments by employing computationally tractable ab initio models driven by highly scalable workflows, to study formation and interaction of various point defects (e.g., O vacancies, H interstitials, and Y substitutional dopant), in over 80 cubic perovskites, for potential proton-conducting ceramic fuel cell (PCFC) applications. The resulting defect data sets identify several promising perovskite compounds that can exhibit high proton conductivity. Furthermore, the data sets also enable us to identify and explain, insightful and novel correlations among defect energies, material identities, and defect-induced local structural distortions. Finally, such defect data sets and resultant correlations are necessary to build statistical machine learning models, which are required to accelerate discovery of new materials.
[en] We report a cesium sulfonate metal organic framework (Cs3(L)(H2O)3.3, 1, L = 1,3,5-trisulfonato-2,4,6-trihydroxybenzene) with hydrated channels that conduct protons at 1.1 x 10-5 S cm-1 at 50% relative humidity and 70 oC. Water was crystallographically observed in the structure, and the likely proton-transfer pathway was studied. The material was not robust, and appropriate parameters were employed to ensure meaningful data were extracted from the study. (author)
[en] The purification and separation technologies are of great importance to industry and agriculture in modern society. Two-dimensional (2D) crystals emerge as superior membrane materials showing desirable molecular permeability and selectivity. Among them, 2D materials with a nanomesh structure show the greatest potential in molecular transport and separation. Here, we highlight the recent theoretical progresses in molecular transport across 2D graphdiyne membrane with the nanomesh structure. Firstly, the nonlinear and activated water flow were demonstrated through the graphdiyne membranes under external hydrostatic pressure. Then, the superior proton conductivity and perfect selectivity were shown for graphdiyne membrane at ambient conditions. Lastly, graphdiyne was shown to exhibit perfect small gas molecule permeability and selectivity at the atmospheric conditions. The mechanisms for molecular transport and selectivity are also discussed. (topical review)
[en] Proton conductivity plays an important role in many important processes like the photosynthesis in green plants, the production of electricity in a hydrogen fuel cell etc. Hence, proton-transport transfer phenomena have been studied extensively by material scientists, chemists, physicists, as well as biologists. Basically there are two mechanisms of proton migration in materials, they are Grotthuss mechanism and vehicle mechanism, both these mechanisms involve mainly two steps, (i) proton transfer between molecular species and (ii) the reorientation or diffusion of molecular species. Hydrogen bonding plays a key role in the first step i.e. proton transfer between molecular species takes place mainly through the hydrogen bonds. Hence a good understanding of the nature of hydrogen bonds can go a long way in understanding the mechanism of proton conduction. Single crystal neutron diffraction (SCND) is the method of choice for studying the hydrogen bond network in crystalline solids; hence SCND investigations on crystalline solid state proton conductors have lead to a significant enhancement in the understanding of Proton conductivity The compounds belonging to the family M_mH_n(XO_4)(m+n)/_2 (M = K, Rb, Cs, NH_4; X = S, Se, P) exhibit superprotonic conductivity and hence are used as the electrolyte of the fuel cell. A comparison between the structures of crystals belong to M_3H(AO_4)_2 family of crystals revealed that slight changes in the hydrogen bond geometry due to compositional variation can lead to a significant change in the nature of superionic phase transition in the crystals. (author)
[en] Proton conductivity in graphene oxide and Nafion films depending on humidity and voltages across electrodes is studied in the model of a field-effect transistor. The electrical characteristics of the films are similar to one another, but the mobility of positive charges in Nafion and the current gain are higher by 2–3 orders of magnitude compared with graphene oxide. The negative ion current in graphene-oxide films at positive bias voltage is significant compared with the proton current (up to ~10%), while it is almost lacking in Nafion films (<1%).
[en] This paper explores the potential to design a “superprotonic conductor” for operation in the intermediate temperature (IT) range through a doping approach with a conventional proton conductor. This approach is validated scientifically, based on the enhanced macroscopic transport properties of the oxide ion conductor. This system consists of a BaZr0.8Y0.2O3−δ (BZY) proton conductor and a small amount of palladium oxide (PdO). The influence of the PdO on the sinter activity of the highly refractory BZY material is not significant, with low rates of grain growth under typical sintering conditions, even though the addition of some PdO favors the grain growth of BZY materials to some extent. The conductivity of PdO-modified BZY (BZPY) is higher than that of BZY in the IT range, in all atmospheres and at all temperatures. The conductivity of 3 mol.% PdO-modified BZPY was 8.60 × 10−3 S cm−1 at 600 °C in wet 5% H2. The electrical conductivity of BZPY increases systematically with increasing PdO content (0.5–3 mol.%) in all atmospheres investigated