Proton-conducting Materials Research Articles

Surface strain and co-doping effect on Sm and Y co-doped BaCeO3 in proton conducting solid oxide fuel cells

Although promising, regulating the surface strain is still immature for enhance the performance of proton-conducting materials and no clear law has been found. In this work, surface strain and co-doping effect on dopant segregation, hydration reaction and proton transport of Sm and Y co-doped BaCeO3 (BCYS) in proton-conducting solid oxide fuel cells (P-SOFC) was investigated. We found that although the dopant segregation trend is reduced as the surface strain increase from −2% to 2%, which means that a large tensile strain is beneficial to enhance structural stability, oxygen vacancy formation energy and proton binding energy near the BCYS surface do not change monotonously with the surface strain. We found that the fewer electrons around the oxygen atoms before hydrogen adsorption, the more stable the proton. It is worth noting that 1% tensile strain is most favorable for enhancing the degree of surface hydration and proton transport in our calculation results, which helps to weaken the negative effects of the space charge layer formed by the accumulation of positive charges on the surface. The collocation of Sm and Y has a synergistic effect, which means Sm facilitates oxygen vacancy formation, while Y promotes hydration reaction. Moreover, the introduction of Sm and Y can hardly change the electronic conductivity of BCYS, which is conducive to the open circuit voltage of P-SOFC.

Multiple Strategies to Fabricate a Highly Stable 2D CuIICuI–Organic Framework with High Proton Conductivity

Using multifunctional organic ligands with multiple acidic groups (carboxylate and sulfonate groups) to synthesize metal-organic frameworks (MOFs) bearing effective H-bond networks is a promising strategy to obtain highly proton conductive materials. In this work, a highly stable two-dimensional MOF, [CuII5CuI2(μ3-OH)4(H2O)6(L)2(H2L)2]·3H2O (denoted as YCu161; H3L = 6-sulfonaphthalene-1,4-dicarboxylic acid) containing mixed-valence [CuII5CuI2(μ3-OH)4]8+ subunits, was successfully prepared. It exhibited excellent stability and temperature- and humidity-dependent proton conduction properties. Its optimal proton conductivity reached 1.84 × 10-3 S cm-1 at 90 °C and 98% relative humidity. On the basis of a crystal structure analysis, water vapor adsorption test results, and activation energy calculations, we deduced the proton conduction pathway and mechanism. Apparently, uncoordinated sulfonic and carboxyl groups and a network of abundant H-bonds inside the framework were responsible for the efficient proton transfer. Therefore, the strategy of selecting suitable bifunctional ligands to construct two-dimensional Cu-cluster-based MOFs with excellent proton conductivity is feasible.

Synthesis of highly water‐absorbing chromium oxyhydroxide as a dopant in a hybrid proton‐conducting membrane

Proton-conductive membranes restrict the energy conversion efficiency and operating performance of the proton exchange membrane fuel cells. In this work, we develop a simple and easy scale-up method to synthesise a new proton-conductive material, amorphous chromium oxyhydroxide (CrO(OH)·xH2O). The CrO(OH)·xH2O shows a high water-adsorption value of 450 mg g−1, contributing to the construction of continuous and ordered hydrogen-bonding network within the materials. An ultra-high proton conductivity of 0.31 S cm−1 is obtained in CrO(OH)·xH2O at 90°C and 98% relative humidity, with an activation energy of 0.39 eV, which indicates a proton hopping mechanism. To further study the application potential of CrO(OH)·xH2O in proton exchange membranes, CrO(OH)·xH2O is added to sulfonated poly(ether ether ketone) (SPEEK) as a dopant, forming a SPEEK-CrO(OH) proton exchange membrane. The composite membrane exhibits a proton conductivity comparable to Nafion, 0.17 S cm−1 at 80°C in water without decreasing in 36 hours. This research enlightens us the development of metal oxyhydroxide via a simple and feasible strategy as efficient proton conductors.

Efficient Proton Transport in Stable Functionalized Channels of Zirconium Metal–Organic Frameworks

Exploring stable proton-conducting materials with high and durable proton conductivity is expected, but it is still a challenge. Here, we report a strategy of modifying the channels of Zr-metal–organic frameworks (MOFs) [UiO-66, Zr6O4(OH)4(bdc)6, bdc = 1,4-benzenedicarboxylate/MOF-808, Zr6O4(OH)4(BTC)2(HCOO)5(H2O)1(OH)1, BTC = benzenetricarboxylate] by an ionic liquid, 1-(propyl-3-sulfonate) imidazolium hydrosulfate, ([(CH2)3SO3H-HIM]HSO4), via the free-solvent reaction to synthesize stable IL@UiO-66 and IL@MOF-808, which show ultrahigh proton conductivities of 1.42 × 10–1 and 7.01 × 10–1 S cm–1 at 70 °C and 98% relative humidity. The conductivity values are comparable to the highest performance of reported MOF-based proton conductors. Furthermore, the proton conduction mechanism of IL@UiO-66 is clearly clarified by the conjoint analysis of the well-defined crystal structure and proton dynamics. Notably, IL@UiO-66 and IL@MOF-808 are fabricated into hybrid membranes with efficient proton transport and good performance stabilities, which lay the foundation for further application. This work provides a basis for studying the proton conduction mechanism and has a promotion on the iterative cycle of understanding, design, and evaluation of advanced proton-conducting materials.

In Situ Aliovalent Nickle Substitution and Acidic Modification of Nanowalls Promoted Proton Conductivity in InOF with 1D Helical Channel.

Proton-conductive materials have attracted increasing attention because of their broad explorations in chemical sensors, water electrolysis, fuel cells, and biological systems. Especially, metal-organic frameworks (MOFs) have been demonstrated to be extremely promising candidates as proton-exchange membrane (PEM) fuel cells. Compared with other configurations, MOFs with one-dimensional (1D) channels have the characteristics of enhancing the host-guest interaction and promoting the anisotropic motion of proton carriers in restricted volume, which are beneficial for acquiring rich proton sources and forming successive hydrogen bonds to improve proton conductivity. We are endeavored to screen and find a helical three-dimensional (3D) framework InOF-1, namely, [In2(OH)2(BPTC)]·6H2O (BPTC4- = 3,3',5,5'-biphenyl tetracarboxylate), as a typical 1D-channel MOF, which is pristinely grafted with spirally distributed -OH groups on the channel surface. Accompanied by an aliovalent substitution Ni(II) for In(III), isostructural NiOF-1 ([Ni2(BPTC)(HCOOH)2]·3H2O) is successfully prepared and massive formic acids are anchored at interior walls, which are interacted with adsorbed water molecules via the formation of stronger O-H···O bonds. This interaction between host-guest molecules and dynamics of lattice water has already led to a remarkable conductivity of InOF-1 (σ = 7.86 × 10-3 S/cm at 328 K under 95% RH). The synergistic effect of the acidic-modified nanowall, contracted volume, and enhanced adsorption of water molecules in the NiOF-1 channel contributes to a high conductivity value of 3.41 × 10-2 S/cm (at 328 K under 95% RH). Moreover, the proton conduction mechanism is further visually presented by molecular dynamic (MD) simulation. In contrast to InOF-1, aliovalent-substituted and acidic-modified NiOF-1 has a stronger host-guest interaction and more abundant hydrogen-bond networks, resulting in shorter proton migration distances and more frequent proton hopping, in agreement with the experimental results.

Synergistic effect of MOF-Directed acid-base pairs for enhanced proton conduction

Developing novel proton-conducting materials is crucial to improve the energy conversion performance of proton exchange membrane fuel cells, especially under the condition of low humidity. Metal-organic frameworks (MOFs) have expressed an apparent potential in proton conduction applications due to their orderly and tunable structure. Previous studies mainly focus on the MOFs modified with homogeneous functional groups to tune the proton conductivities. In this study, an acid-base pair synergistic strategy, namely introducing the acidic and basic groups into mix-linker MOF simultaneously to obtain acid-base coexistence materials, was firstly proposed to improve the proton conduction performance at 75% RH. Herein, 10 kinds of ML-UiO-66-(A)(B)-X were synthesized and the effects of content and ratio of acid-base pairs in MOF matrix on proton-conducting properties were studied. It was found that ML-UiO-66-(NH 2 )(SO 3 H)-5:5 possessed the highest proton conduction in the ML-UiO-66 materials, with the value of 2.8 × 10 -2 S·cm −1 at 353 K. In addition, at 303K, 75% RH, the proton conductivity of ML-UiO-66-(NH 2 )(SO 3 H)-5:5 reached 7.4 × 10 −3 S·cm −1 , which is three orders of magnitude higher than pristine UiO-66 (~980 times), two orders of magnitude higher than the base-functionalized UiO-66-NH 2 (~529 times) and about 218% higher than the acid-functionalized UiO-66-SO 3 H at 97% RH. The results show that at relatively lower humidity 75%, ML-UiO-66-(NH 2 )(SO 3 H)-5:5 has the better proton conductivity than other UiO-66 materials at nearly 100% RH. Meanwhile, ML-UiO-66-(NH 2 )(SO 3 H)-5:5 shows high water and thermal stability under high humidity and high temperature, which ensures its application in complex environment. Performance and mechanism studies show that the strategy of introducing acid-base pair into MOF matrix may open an avenue to design novel proton-conducting materials with excellent properties. UiO-66-directed ordered acid-base coexistence materials are prepared with the conductivity being 2.8 × 10 −2 S cm −1 at 353 K and 75% RH. • The proton conductivity of ML-UiO-66-(NH 2 )(SO 3 H)-5:5 is 2.8 × 10 −2 S cm −1 at 353 K, 75% RH. • The acid-base pairs in MOFs helps to reduce the activation energy of proton conduction. • The MOF-directed acid-base coexistence strategy is helpful to reduce the production cost and has high practical application value.

Analysis of Pressurized, Tubular, Proton-conducting, Ceramic Reversible Fuel Cells for Efficient, Low-Cost Energy Storage

This work analyzes pressurized, tubular, proton-conducting, ceramic reversible fuel cells (PreTProCRFC) for efficient, low-cost energy storage. PreTProCRFC have the potential to facilitate low carbon energy economies and power-to-gas applications. In the power-to-gas concept, excess electricity from wind turbines and solar photovoltaic arrays is sent to high temperature electrolyzers, like the PreTProCRFC, that store energy as hydrogen (H2) and oxygen (O2) for short or long durations (> 4 hours). When electricity is needed, the PreTProCRFC runs as a fuel cell and consumes the stored H2 and O2 to generate electricity. In this way, PreTProCRFCs have the potential to significantly augment the growth of renewables globally. This research analyzes the potential for PreTProCRFCs as viable short or long-term energy storage devices. This work develops thermodynamic and techno-economic analyses (TEA) for these PreTProCRFC systems and identifies cost drivers important to their R&D and commercialization path. This work also explores the value propositions presented by pressurized, tubular designs, for different segments of the energy storage market.Approach:This work is conducted in close collaboration with project partners Special Power Sources Inc. (SPS), which currently manufactures tubular ceramic fuel cells for research and niche energy applications, and Kansas State University (KSU), which is developing novel, proton-conducting ceramic materials. To execute this research, Gaia works with SPS and KSU to identify and analyze cell, stack, and system engineering performance data. Gaia then develops and deploys custom computer models and data sets that include, but are not limited to, chemical engineering process plant designs of PreTProCRFC systems and detailed TEA models. Gaia also builds on existing U.S. DOE modelling tools, such as the H2A H2 production analysis modelling tools and existing DOE electrolysis case studies.Results:Modelling results indicate that the primary cost drivers for the lifecycle energy storage costs of PreTProCRFC systems include, but are not limited to,(1) the system’s ramp rate in fuel cell mode (i.e. the electric power output per unit time);(2) the system’s ramp rate in electrolysis mode (i.e. the electric power input per unit time);(3) the quantity of effective heat reuse between exothermic fuel cell modes and endothermic electrolysis modes;(4) the efficiency of thermal storage between fuel cell and electrolysis modes;(5) the electricity consumed per unit of hydrogen produced in electrolysis mode;(6) the electricity consumed per unit of oxygen produced in electrolysis mode;(7) the capital costs of the stack;(8) the capital costs of the surrounding balance of plant (BOP) subsystems;(9) the electrolysis outlet pressures for hydrogen and oxygen; and(10) the marginal increase in system cost with higher electrochemical outlet pressures.Regarding (1) and (2), when connected to the electricity grid, and receiving intermittent renewable electricity to store, PreTProCRFC systems need the capability to respond rapidly. Electricity storage devices that can either receive and/or supply electricity more quickly can demand a higher premium ($/kWh price). In particular, the electricity balancing market is a submarket within the overall electricity market responsible for reconciling instantaneous differences in electricity supply and demand, and, consequently, sees the highest prices. The proposed SPS PreTProCRFC stack design is tubular, with less total sealant area, and with a close match of stack material thermal expansion coefficient, so it is expected that this design will more readily electrically ramp compared with other designs. (A main failure mechanism of high temperature electrochemical systems under fast-ramping conditions is mechanical cracking of the stack’s materials, due thermal expansion coefficient mismatches.)Regarding (3), (4), (5), and (6), a unique feature of high temperature electrolysis (compared with low temperature electrolysis) is that electricity consumption by the electrolyzer can be displaced by heat consumption, in a one-to-one ratio. In a PreTProCRFC system, heat released during the exothermic fuel cell reaction can be stored and reused to provide heat for electrolysis. Efficient design of this heat reuse subsystem is crucial to the PreTProCRFC system achieving high round-trip efficiencies, a necessity for the energy storage market.Regarding (7) and (8), primary cost drivers for PreTProCRFC system also include stack capital costs, stack power density, and system BOP costs. Over time, stack capital costs are estimated to decline more rapidly with R&D and more high volume manufacture, compared with BOP capital costs, because the BOP already incorporates many mass-produced components.Regarding (9) and (10), the SPS PreTProCRFC stack is also unique in that it has the capacity to supply hydrogen and oxygen at pressure. Model results indicate that electrochemical compression has the most compelling cost advantage over mechanical compression in the lower pressure range included in the proposed stack design.

Crystal structures, proton conductivities and luminescence of two organic-inorganic hybrid materials based on Keggin-type clusters and Cu(II)/Cu(I)-bis(hydroxymethyl)-2,2′-bipyridine complexes

Two proton-conductive and luminescent organic-inorganic hybrid materials, {[Cu(II)(bhmbpy)(H2O)(Cl)0.5(CH3CN)]2[PW(VI) 10W(V) 2O39]}·4H2O(1) and {H2[Cu(I)(bhmbpy)2(Cl)Cu(I)(bhmbpy)2][PW12O40]}·7H2O (2) (where bhmbpy is bis(hydroxymethyl)-2,2′-bipyridine), were synthesized at room temperature. The two products were characterized by infrared spectroscopy, X-ray single-crystal diffraction, X-ray powder diffraction, elemental and thermogravimetric analyses. The proton conductivities and luminescence of 1 and 2 were studied by using alternating-current impedance spectroscopy and luminescence spectroscopy, respectively. X-ray diffraction analysis revealed that 1 includes a decorated polyanion chain {[Cu(II)(bhmbpy)(H2O)(Cl)0.5(CH3CN)]2[PW(VI) 10W(V) 2O39]}n and forms a three-dimensional network structure depending on short Cl…Cl contacts and hydrogen-bonding interactions. X-ray diffraction analysis revealed that 2 includes a butterfly-like bi-nuclear copper cluster unit with a Cl-bridge, [Cu(I)(bhmbpy)2(Cl)Cu(I)(bhmbpy)2]+, and forms a three-dimensional network structure depending on hydrogen-bonding interactions. [PW12O40]3– anions fill in the network based on hydrogen-bonding and electrostatic interactions. In them, the bhmbpy acts as a bidentate nitrogen donor ligand in the chelating fashion to coordinate with the Cu(II) center in 1 and the Cu(I) center in 2. The bhmbpy in 2 successfully constrains the Cu(I) within a rigid environment in a tetragonal-pyramidal geometry. The two compounds exhibit good proton conductivity (10−4 S·cm−1) at 100 °C in the relative humidity range 35–98%. Their luminescence behaviors in the solid state at room temperature have also been investigated. Upon excitation at 384 nm, 1 exhibits three emission peaks centered at 439, 507 and 566 nm. When excited at 364 nm, 2 displays three emission peaks centered at 443, 501 and 553 nm.

High and Tunable Proton Conduction in Six 3D-Substituted Imidazole Dicarboxylate-Based Lanthanide-Organic Frameworks.

Six isostructural three-dimensional (3D) Ln(III)-organic frameworks, {[Ln2(HMIDC)2(μ4-C2O4)(H2O)3]·4H2O}n [LnIII = GdIII (1), EuIII (2), SmIII (3), NdIII (4), PrIII (5), and CeIII (6)], have been fabricated by using a multifunctional ligand of 2-methyl-1H-imidazole-4,5-dicarboxylic acid (H3MIDC). Ln-metal-organic frameworks (MOFs) 1-6 present 3D structures and possess abundant H-bonded networks between imidazole-N atoms and coordinated and free water molecules. All the six Ln-MOFs demonstrate humidity- and temperature-dependent proton conductivity (σ) having the optimal values of 2.01 × 10-3, 1.40 × 10-3, 0.93 × 10-3, 2.25 × 10-4, 1.11 × 10-4, and 0.96 × 10-4 S·cm-1 for 1-6, respectively, at 100 °C/98% relative humidity, in the order of CeIII (6) < PrIII (5) < NdIII (4) < SmIII (3) < EuIII (2) < GdIII (1). In particular, the σ for 1 is 1 order of magnitude higher than that for 6, and it enhances systematically according to the decreasing order of the ionic radius, indicating that the lanthanide-contraction tactics can effectively regulate the proton conductivity while retaining the proton conduction routes. This will offer valuable guidance for the acquisition of new proton-conducting materials. In addition, the outstanding water stability and electrochemical stability of such Ln-MOFs will afford a solid material basis for future applications.

Positive Cooperative Protonation of a Metal-Organic Framework: pH-Responsive Fluorescence and Proton Conduction.

Positive cooperative binding, a phenomenon prevalent in biological processes, holds great appeal for the design of highly sensitive responsive molecules and materials. It has been demonstrated that metal-organic frameworks (MOFs) can show positive cooperative adsorption to the benefit of gas separation, but potential binding cooperativity is largely ignored in the study of sensory MOFs. Here, we report the first demonstration of positive cooperative protonation of a MOF and the relevant pH response in fluorescence and proton conduction. The MOF is built of Zr-O clusters and bipyridyl-based tetracarboxylate linkers and has excellent hydrolytic stability. It shows a unique pH response that features two synchronous abrupt turn-off and turn-on fluorescent transitions. The abrupt transitions, which afford high sensitivity to small pH fluctuations, are due to cooperative protonation of the pyridyl sites with a Hill coefficient of 1.6. The synchronous dual-emission response, which leads to visual color change, is ascribable to proton-triggered switching between (n, π*) and (π, π*) emissions. The latter emission can be quenched by electron donating anion-dependent through photoinduced electron transfer and ground-state charge transfer. Associated with cooperative protonation, the proton conductivity of the MOF is abruptly enhanced at low pH by two orders, but overhigh acid concentration is adverse because excessive anions can interrupt the conducting networks. Our work shows new perspectives of binding cooperativity in MOFs and should shed new light on the development of responsive fluorescent MOFs and proton conductive materials.

Mesoscale Morphologies of Nafion-Based Blend Membranes by Dissipative Particle Dynamics

Polymer electrolyte membrane (PEM) composed of polymer or polymer blend is a vital element in PEM fuel cell that allows proton transport and serves as a barrier between fuel and oxygen. Understanding the microscopic phase behavior in polymer blends is very crucial to design alternative cost-effective proton-conducting materials. In this study, the mesoscale morphologies of Nafion/poly(1-vinyl-1,2,4-triazole) (Nafion-PVTri) and Nafion/poly(vinyl phosphonic acid) (Nafion-PVPA) blend membranes were studied by dissipative particle dynamics (DPD) simulation technique. Simulation results indicate that both blend membranes can form a phase-separated microstructure due to the different hydrophobic and hydrophilic character of different polymer chains and different segments in the same polymer chain. There is a strong, attractive interaction between the phosphonic acid and sulfonic acid groups and a very strong repulsive interaction between the fluorinated and phosphonic acid groups in the Nafion-PVPA blend membrane. By increasing the PVPA content in the blend membrane, the PVPA clusters’ size gradually increases and forms a continuous phase. On the other hand, repulsive interaction between fluorinated and triazole units in the Nafion-PVTri blend is not very strong compared to the Nafion-PVPA blend, which results in different phase behavior in Nafion-PVTri blend membrane. This relatively lower repulsive interaction causes Nafion-PVTri blend membrane to have non-continuous phases regardless of the composition.

3D-Printing of Proton Conducting Ceramics

3D-printing technology is being extensively utilized in energy sector, as it allows for manufacturing complex structures (compacted stacks, desired microarchitectures and porosity) and customizable shapes for specific devices. Moreover, fast prototyping time and reduction of production cost make this technology promising for industrial applications. Up to now, plenty of 3D-printed energy conversion and storage devices and hence precursor materials have been proposed. Reported examples concern solar cells, biofuel cells, rechargeable ion batteries, carbon-based supercapacitors and others [1-2]. On the other hand, 3D-printing of proton-conducting materials is rarely reported. The pioneering research was presented by Mu et al., who have developed novel laser 3D-printing method which allows to obtain protonic ceramics with the desired crystal structures, microstructures, and geometries [3]. The method consists of the preparation of printable paste from component raw materials (carbonate and single metal oxides) mixed with sintering aid, the deposition of a thin green film of the targeted protonic ceramics, and the reactive sintering by rapid CO2 laser scanning. Such method was successfully applied for the synthesis of dense electrolytes (e.g. BCZYYb, BZY20), porous electrodes (e.g. BCZYYb+NiO, BaCo0.4Fe0.4Zr0.1Y0.1O3-δ), dense interconnect (La0.7Sr0.3CrO3-δ/LSC), and dense mixed protonic and electronic-conduction composite (BaCe0.85Fe0.15O3-δ– BaCe0.15Fe0.85O3-δ/BCF) [4]. The second available example is devoted to the 3D-printed proton exchange membrane and has been recently reported by K. Iwase and co-workers [5]. Scientists developed UV-cured ink (mixture of proton-conducting ionic liquids, inorganic silica nanoparticles, and UV-sensitive photocurable resins) which can be successfully applied to the printing of proton exchange membranes.In the present study, we developed 3D-printing of protonic ceramics- Ba0.5La0.5Co1-xFexO3-δ (0 ≤x≤ 1), which are promising materials for positrodes in protonic ceramic fuel cells [6]. The Project is devoted both to the construction of 3D-printer and ink preparation. Two printing technology- fused deposition modeling and extrusion-based 3D-printing were selected and embedded into one 3D-printer. In addition, the system was equipped with IR laser for post-processing. Ink (solid filament or gel) was prepared from ceramic powder and polymer (i.e. polylactic acid or polyvinyl alcohol), which act as a matrix and is removed at the end. Various compositions (e.g.ceramic to polymer ratio, polymer concentration, solvent) and synthesis conditions (e.g. time, temperature) were tested. A lot of attention was paid to the proper ceramic dispersion, which ensures printouts homogeneity. Therefore, various approaches such as ball-milling of ceramic and ultrasonication of gel were optimized and implemented. The last important step was devoted to the laser post-processing, during which polymer is removed and ceramic is sintered. Various laser powers, scan speeds and number of scans were tested. Printed layers before and after post-processing were characterized by X-Ray diffraction, Fourier Transform Infra-Red spectroscopy and Scanning Electron Microscopy. In the future it is planned to adopt developed technology and use it for the printing of multi-layered positrodes with graded functionality.

ПРОТОНПРОВОДЯЩИЕ МАТЕРИАЛЫ НА ОСНОВЕ ПОЛИВИНИЛХЛОРИДА И АРОМАТИЧЕСКИХ СУЛЬФОКИСЛОТ

Proton-conducting materials based on polyvinyl chloride modified with aromatic sulfonic &#x0D; acids were obtained.

Self-Standing combined covalent-organic-framework membranes for subzero conductivity assisted by ionic liquids

The development of proton-conducting materials in cold regions is still at the initial stage due to the challenge in breaking the subzero temperature limit, especially in covalent organic frameworks (COFs). Herein, we fabricated a series of proton-conductive COFs as self-standing, highly flexible combined membranes (ssc-COFMs) composed of a processable TpBD-Me2 and a conductive Tp-TGCl, in-situ encapsulated proton-conducting ionic liquids (PCILs) as additional proton sources into backbones. Compositions and microstructures of ssc-COFMs are monitored by XRD, FTIR, nitrogen adsorption and elemental analysis. Comparison to other porous organic conductors, a great advance propelled renders the combined COF membranes to have a high protonic conductivities at medium and subzero temperatures (243 to 353 K), owing to the resultant multifaceted synergistic effect of multiple proton units. Specifically, the proton conductivities of the ssc-COFMs loaded with –SO4H functionalized PCILs reaches 2.87 × 10-4 S cm−1 (~58% RH) and 9.93 × 10−4 S cm−1 (~98% RH) at 243 K, together with 6.84 × 10−2 S·cm−1 under 353 K and ~ 98% RH.

Ultrafast and Stable Proton Conduction in Polybenzimidazole Covalent Organic Frameworks via Confinement and Activation

Polybenzimidazoles are engineering plastics with superb thermal stability and this specificity has sparked a wide-ranging research to explore proton-conducting materials. Nevertheless, such materials encounter challenging issues owing to phosphoric acid proton carrier leakage and slow proton transport. We report a strategy for designing porous polybenzimidazole frameworks to address these key fundamental issues. The built-in channels are designed to be one-dimensionally extended, unidirectionally aligned, and fully occupied by neat phosphoric acid, while the benzimidazole walls trigger multipoint, multichain, and multitype interactions to spatially confine a phosphoric acid network in pores and facilitate proton conduction via deprotonation. The materials exhibit ultrafast and stable proton conduction for low proton carrier content and activation energy-a set of features highly desired for proton transport. Our results offer a design strategy for the fabrication of porous polybenzimidazoles for use in energy conversion applications.

Characteristics of a Plasticized PVA-Based Polymer Electrolyte Membrane and H+ Conductor for an Electrical Double-Layer Capacitor: Structural, Morphological, and Ion Transport Properties.

Poly (vinyl alcohol) (PVA)-based solid polymer electrolytes doped with ammonium thiocyanate (NH4SCN) and glycerol were fabricated using a solution casting method. Lithium-based energy storage devices are not environmentally friendly materials, and they are toxic. Thus, proton-conducting materials were used in this work as they are harmless and are smaller than lithium. The interaction between PVA and the electrolyte elements was shown by FTIR analysis. The highest conductivity of 1.82 × 10−5 S cm−1 was obtained by the highest-conducting plasticized system (PSP_2) at room temperature. The mobility, diffusion coefficient, and number density of anions and cations were found to increase with increasing glycerol. FESEM was used to investigate the influence of glycerol on film morphology. TNM showed that the cations and anions were the main charge carriers. LSV showed that the electrochemical stability window of the PSP_2 system was 1.99 V. The PSP_2 system was applied in the preparation of an electrical double layer capacitor device. The shape of the cyclic voltammetry (CV) curve was nearly rectangular with no Faradaic peaks. From the galvanostatic charge-discharge analysis, the power density, energy density, and specific capacitance values were nearly constant beyond the first cycle at 318.73 W/Kg, 2.06 Wh/Kg, and 18.30 F g−1, respectively, for 450 cycles.

Isotopic effect of proton conductivity in gadolinium sesquioxide

Due to the higher hydrogen solubility and diffusivity, gadolinium sesquioxide (Gd2O3) could be expected as a proton conductive material. In this study, monoclinic Gd2O3 was used to evaluate the possible proton conductivity in Ar (σAr), Ar+4% H2 (σH2), Ar+4% D2 (σD2), Ar+H2O (σH2O), Ar+D2O (σD2O), and O2 (σO2) atmospheres in the temperature range from 500°C to 1000°C, to understand its possible application in the DT fuel system of a nuclear fusion reactor. At all temperatures, the conductivity σD2 was lower than that of the σH2. Similarly, the σD2O was always lower than that of the σH2O. The isotope dependence was appreciable at higher temperatures, indicating that Gd2O3 is a proton-conductive oxide at elevated temperatures. However, much improvement is required for the use of Gd2O3 in the DT fuel recovery, analysis, and purification system of fusion reactors.

Control of Proton-Conductive Behavior with Nanoenvironment within Metal-Organic Materials.

Solid-state proton-conductive materials have been of great interest for several decades due to their promising application as electrolytes in fuel cells and electrochemical devices. Metal-organic materials (MOMs) have recently been intensively investigated as a new type of proton-conductive materials. The highly crystalline nature and structural designability of MOMs make them advantageous over conventional noncrystalline proton-conductive materials-the detailed investigation of the structure-property relationship is feasible on MOM-based proton conductors. This review aims to summarize and examine the fundamental principles and various design strategies on proton-conductive MOMs, and shed light on the nanoconfinement effects as well as the importance of hydrophobicity on specific occasions, which have been often disregarded. Besides, challenges and future prospects on this field are presented.

Ionic liquid-impregnated covalent organic framework/silk nanofibril composite membrane for efficient proton conduction

Covalent organic frameworks (COFs) hold great potential for proton-conducting materials due to the intrinsic pore channels and high surface areas. However, their limited functional groups and poor film-forming properties remain significant challenge. Silk nanofibrils (SNFs) have good mechanical property and abundant functional groups, which can be exfoliated from natural bombyx mori silks. Herein, we demonstrate a novel strategy of utilizing the flexibility of SNFs to assemble conductive COFs into a stable membrane form. Ionic liquids (ILs)-impregnated sulfonic acid-based COF (IL-COF-SO3H) is prepared and then is combined with SNF to fabricate IL-impregnated COF/SNF composite membrane. The uniformly distributed ILs inside COF-SO3H increase the number of proton hopping sites. Meanwhile, the –SO3H groups can form strong interactions with imidazole-type ILs and immobilize ILs within the channels, endowing COF-SO3H pores low-barrier proton transfer pathways. Additionally, the hydrogen-bonding interactions between IL-COF-SO3H and SNFs enable interfacial binding and structure stability, as well as facilitate proton transfer. Thus, the resultant IL-COF-SO3H@SNF composite membrane simultaneously obtains enhanced conductivity (224 mS cm−1 at 90 °C and 100% RH) and mechanical performance (tensile strength of 28.6 MPa). This study provides novel insight into fabrication of stable COF-based membrane for high-performance conduction materials.

High temperature compressive creep behavior of BaCe0.65Zr0.2Y0.15O3−δ in air and 4% H2/Ar

AbstractThe proton conductive material BaCe0.65Zr0.2Y0.15O3−δ has great potential for the separation and purification of hydrogen. However, due to the demanding application conditions regarding both temperature and atmosphere, the elevated temperature structural stability needs to be characterized and warranted. Hence, in this research work, the elevated temperature compressive creep behavior of BaCe0.65Zr0.2Y0.15O3−δ in the temperature regime of 850°C to 1200°C was studied in both air and 4% H2/Ar as a function of the applied stress. The results indicate different creep mechanisms depending on atmosphere and temperature range. While dislocation creep was observed in 4% H2/Ar over the full range, a dislocation creep mechanism was observed in air at temperatures ≤1050°C and a diffusional creep mechanism at temperature ≥1100°C. A detailed microstructural analysis of the post‐creep test specimens revealed that the exposure to oxygen leads to localized stoichiometric changes and a decomposition at the surface.