High Temperature Proton Conductors Research Articles

High-Temperature Protonic Conduction in La2 NiO4+ δ -Based Ruddlesden-Popper Type Oxides: Correlation with Concentration of Interstitial Oxide Ions.

Oxygen-excess La2 NiO4+ δ (LNO) conducts oxide ions, electron holes, and hydroxide ions simultaneously on exposing to wet oxygen, exhibiting the potential as a cathode material in protonic ceramic fuel cells. Since the incorporation of protons in oxygen-excess LNO is via the hydration reaction assisted by interstitial oxide ions, in this work, the concentration of interstitial oxide ions is reduced and increased by substituting Ni with Cu and Co, respectively. A higher concentration of interstitial oxide ions leads to a high proton concentration, indicating the predominant role of interstitial oxide ions in the hydration reaction, different from that in the oxygen-deficient oxides, where protons are introduced by dissociative absorption of water molecules by oxygen vacancies. The theoretical calculation indicates that protons in Co-doped LNO prefer to locate between the interstitial oxide ions and unshared apical oxide ions. A trapping effect is found between protons and the oxide ions near Cu, leading to decreased proton mobility. Protonic conductivity at 400-575 °C is then directly measured by a Hebb-Wagner direct current polarization method with La0.99 Ca0.01 NbO4- δ as the blocking electrode, enabling the observation that Co-doped LNO has the highest protonic conductivity among the samples studied in this work.

SYNTHESIS OF POLYMER ELECTROLYTE MEMBRANES BASED ON IONIC LIQUID DOPED SPEEK

The sustainable and environmentally benign energy demand of the world has been increasing. Among the various options, proton exchange membrane fuel cell is an attractive choice for energy supply due to its high efficiency and application conditions without waste. In this research, triazole-based ionic liquid doped sulfonated polyether ether ketone (SPEEK) composite membranes were presented for proton exchange membrane fuel cell (PEMFC) applications. Composite membranes were prepared by incorporating 1,2,3-triazole-based ionic liquids (TIL 1-2-3) into poly(ether ether ketone) (PEEK) matrices. The mechanical, structural, and thermal properties of both composite membranes and the triazole-based ionic liquids were thoroughly characterized using dynamic mechanical analysis (DMA), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The performance and viability of composites for PEMFC applications that involve elevated temperatures were conducted by proton conductivity test across a broad range of temperatures (30-180 oC). High-temperature proton conductivity was measured as 1.73x10-2 S/cm for SPEEK/TIL-3(1.0). According to the proton conductivity test results, it was concluded that the composite membranes may exhibit improved performance in PEMFC applications due to increased proton conductivity values.

Nanocellulose as a Sustainable Polymer Electrolyte

Polymer electrolyte membranes in fuel cells and electrolyzers will play a key role in the hydrogen economy. These membranes are generally made of sulfonated fluoropolymers, which have excellent proton conductivity, impressive redox stability, and good gas barrier properties. However, the complex synthetic processes mean that they remain expensive. Their synthesis also involves ecologically damaging perfluorosulfonic acids (PFSAs), otherwise known as “forever chemicals” due to their persistence in the environment. More sustainable and lower cost hydrocarbon electrolytes should therefore be investigated.Cellulose is the most abundant biopolymer in nature, and is derived from plant matter. It is used at vast scale and low cost to make paper and cardboard. Cellulose can be chemically or mechanically treated to break up the fibers to form “nanocellulose”. Nanocellulose is a low-cost nanomaterial which can be formed into thin membranes which are much stronger than conventional cellulosic paper.We propose nanocellulose as an alternative electrolyte to replace sulfonated fluoropolymers in fuel cells. We confirmed that unmodified nanocellulose can conduct protons due to acidic hydroxyl groups. We also showed that nanocellulose membranes present a much better barrier to hydrogen compared to Nafion, and can successfully be used as an electrolyte in fuel cells. However, the current-voltage performance of unmodified nanocellulose was insufficient due to a high membrane resistance.We went on to improve the proton conductivity by introducing sulfonic acid groups and reduced the membrane resistance by using spray deposition to create thinner membranes, resulting in significantly improved fuel cell power density of 160 mW/cm2. We also implemented crosslinking with sulfosuccinic acid to simultaneously improve the ionic conductivity, increase strength, and reduce swelling in water. This work shows that nanocellulose is a promising new class of polymer electrolyte which could significantly reduce the cost and improve sustainability of fuel cell and electrolyser systems.1. Cellulose Nanocrystals Crosslinked with Sulfonic Acid as Sustainable Proton Exchange Membranes for Electrochemical Energy Applications, O. Selyanchyn, T. Bayer, D. Klotz, R. Selyanchyn, K. Sasaki, S. M. Lyth, Membranes 12 (7), 658 (2022)2. Spray Deposition of Sulfonated Cellulose Nanofibers as Proton Conducting Membranes for Fuel Cells, T. Bayer, B. Cunning, R. Selyanchyn, B. Smid, S. Fujikawa, K. Sasaki, S. M. Lyth, Cellulose, 28, 1355–1367 (2021)3. Proton Conductivity in Cellulosic Materials: A Review, O. Selyanchyn, R. Selyanchyn, S. M. Lyth, Frontiers in Energy Research: Fuel Cells, 8, 596164 (2020)4. High Temperature Proton Conductivity in Nanocellulose: Paper Fuel Cells, T. Bayer, R. Selyanchyn, S. Fujikawa, K. Sasaki, and S. M. Lyth, Chemistry of Materials, 28 (13), 4805–4814 (2016)

Polybenzimidazole-based polymers of intrinsic microporosity membrane for high-temperature proton conduction

Anhydrous proton conducting polymer membrane materials have raised much attention in the application of high-temperature proton-exchange membranes (HT-PEMs) fuel cells, which convert chemical energy into electrical energy. Polybenzimidazole-based polymers, as typical materials for HT-PEMs, their compact structures result in small fractional free volumes (FFV), which is not conducive to the adsorption and retention of proton carriers. Herein, a series of polybenzimidazole-based polymers of intrinsic microporosity (PIM-PBIs) were synthesized. PIM-PBIs possess the benzimidazole units and porous structures, and have good thermal stability and large specific surface area (100 ∼ 400 m2/g). PIM-PBIs are further embedded in polyvinylidene fluoride (PVDF) to form mixed matrix membranes for high-temperature proton conduction. The resulting membranes exhibit high proton conductivity up to 90.11 mS cm−1 at 140 ℃ and high phosphoric acid (PA) retention rate of 90.0 %. This work provides a facile method for the precise design and preparation of proton-conducting porous materials.

TiO2 nanoparticle enhanced high temperature proton conductivity in hyperbranched sulfonated polyarylene aliphatic ketones for proton exchange membrane fuel cell applications

AbstractA new hyperbranched sulfonated poly(arylene aliphatic ketones) (HB‐SPAAK) has been synthesized and loaded with titania nanoparticles to obtain HB‐SPAAK/TiO2 nanocomposites for thermally stable proton‐conducting electrolyte membrane fuel cell (PEMFC) applications. The synthesis of HB‐SPAAKs was carried out through the polycondensation reaction of different aliphatic and aromatic acids with simultaneous loss of H2O, trifluromethane sulfonic acid used as catalyst. The long chain hyperbranched polymers and TiO2‐loaded nanocomposites were characterized by FT‐IR, 1H‐NMR, SEM and HR‐TEM. Proton conductivity (PC), swelling ratio, water uptake and oxidative stability. The SEM image of TiO2 NPs and HB‐SPAAKs/TiO2 nanocomposites membrane clearly showed the spherical of TiO2 and porous structure of HB‐SPAAKs with a pore diameter of 2–50 μm. TEM image reveals the uniform particle size distribution of TiO2 nanoparticles having a nanosize of 100 nm. TiO2 loaded polymer nanocomposites showed lower values of W/U and S/R when compared to the unmodified HB‐SPAAK, while 3% TiO2 loaded HB‐SPAAKs exhibited a threefold increment of proton conductivity of 1.439 × 10−2 S cm−1 compared to HB‐SPAAKs (0.41 x 10−2 S cm−1) and lower than that of Nafion 117 (0.1003 S cm−1 at 80°C). The 5% TiO2 NPs‐embedded with HB‐SPAAKs nanocomposites membranes also presented admirable oxidative stability with a degradation value of 13.8% during immersion in Fenton reagent for 8 h at 70°C.

A porous cobalt(II)-organic framework exhibiting high room temperature proton conductivity and field-induced slow magnetic relaxation.

A two-dimensional (2D) cobalt(II) metal-organic framework (MOF) constructed by a ditopic organic ligand, formulated as {[Co(Hbic)(H2O)]·4H2O}n (1) (H2bic = 1H-benzimidazole-5-carboxylic acid), was hydrothermally synthesized and structurally characterized. Single-crystal X-ray diffraction shows that the distorted octahedral Co2+ ions, as coordination nodes, are bridged to form 2D honeycomb networks, which are further organized into a 3D supramolecular porous framework through multiple hydrogen bonds and interlayer π-π interactions. Dynamic crystallography experiments reveal the anisotropic thermal expansion behavior of the lattice, suggesting a flexible hydrogen-bonded 3D framework. Interestingly, hydrogen-bonded (H2O)4 tetramers were found to be located in porous channels, yielding 1D proton transport pathways. As a result, the compound exhibited a high room-temperature proton conductivity of 1.6 × 10-4 S cm-1 under a relative humidity of 95% through a Grotthuss mechanism. Magnetic investigations combined with theoretical calculations reveal giant easy-plane magnetic anisotropy of the distorted octahedral Co2+ ions with the experimental and computed D values being 87.1 and 109.3 cm-1, respectively. In addition, the compound exhibits field-induced slow magnetic relaxation behavior at low temperatures with an effective energy barrier of Ueff = 45.2 cm-1. Thus, the observed electrical and magnetic properties indicate a rare proton conducting SIM-MOF. The foregoing results provide a unique bifunctional cobalt(II) framework material and suggest a promising way to achieve magnetic and electrical properties using a supramolecular framework platform.

Pressure-induced negative capacitance and enhanced grain boundary conductivity in nanocrystalline solid electrolyte BaZrO3

Proton-conducting BaZrO3-doped electrolytes are considered as potential high temperature proton conductors due to their high ionic conductivity and electrical efficiency in the operating temperature range of solid oxide fuel cells. However, doping leads to a decrease in grain boundary conductivity and greatly limits its applications. Here, the charge transport properties of sub-micro and nano-BaZrO3 electrolytes were studied by in situ high-pressure impedance measurements and first-principles calculations. Mixed ionic-electronic conduction was found in both samples in the whole pressure range. Pressure-induced negative capacitance in the tetragonal phase of nano-BaZrO3 was observed, which was related to the space charge layer of grain boundaries as well as the electrostrictive strain of grains. The enhanced electrostrictive effect was attributed to the existence of polar nano-domains in nano-BaZrO3. Furthermore, the coincident imaginary part of impedance and modulus peaks on the frequency scale indicated a non-localized carrier conduction in the tetragonal phase of nano-BaZrO3. The grain boundary conductivity of nano-BaZrO3 was enhanced by four orders of magnitude, and the impedance response changed from a constant phase element to an ideal capacitance, which was accompanied by the cubic to tetragonal phase transition. At a switching frequency of 0.1 Hz, the real part of the dielectric function of nano-BaZrO3 increases sharply with frequencies from negative to positive values, exhibiting a plasma-like Drude behavior. Our results provide insight into the optimization and application of BaZrO3-based proton conductors in solid oxide fuel cells.

Phase-Changeable Polyoxometalate-Based Acid–Base Adduct for High-Temperature Proton Conduction

Phase-Changeable Polyoxometalate-Based Acid–Base Adduct for High-Temperature Proton Conduction

Development of 1,2,3-Triazole Based Ionic Liquid Doped Sulfonated Polysulfone (SPSU) Electrolytes for Anhydrous Proton Exchange Membrane Applications

In this study, triazole based ionic liquid doped sulfonated polysulfone (SPSU) composite membranes were evaluated for high temperature proton exchange membrane fuel cell (PEMFC) systems. SPSU obtained by sulfonation of aromatic polysulfone (PSU) polymer matrix was used in the preparation of composite electrolytes. Sulfonated polymer matrices were doped with three different triazole-based ionic liquids (TIL-1, TIL-2 and TIL-3) synthesized within the scope of the study and composite membrane series were formed. Structural, thermal and mechanical characterizations were performed by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA), respectively. Proton conductivities were measured over a wide temperature range (380-450 K) and the effectiveness of composite membranes in high temperature PEMFC systems was evaluated. As a result of TGA analysis, all triazole based ionic liquid doped membrane series exhibited high thermal resistance. It was observed that the proton conductivity of the composite structures was greatly improved with high temperature proton conductivity measurements (8.05 mS/cm for SPSU; 58.1 mS/cm for SPSU/TIL-3(1.0)) and the obtained membranes could be an alternative in high temperature PEMFCs.

X-ray Micro-Computed Tomography: A Powerful Device to Analyze the 3D Microstructure of Anode-Electrolyte in BaZr0.8Y0.2O3 Protonic Ceramic Electrochemical Cells and the Reduction Behavior

New advanced fuel cell technologies are moving towards high-temperature proton conductors (HTPCs) to meet environmental issues. Their elaboration remains a challenge and micro-computed tomography (µCT) is an innovative way to control their quality. NiO-BZY anodic supports of a protonic ceramic electrochemical cell (PCEC), elaborated by co-tape casting and co-sintered at 1350 °C, were coated with a BZY20 electrolyte layer by DC magnetron sputtering. The µCT allowed to observe defects inside the volume of these PCEC half-cells and to show their evolution after an annealing treatment at 1000 °C and reduction under hydrogen. This technique consists in obtaining a 3D reconstruction of all the cross-sectional images of the whole sample, slice by slice. This allows seeing inside the sample at any desired depth. The resolution of 0.35 µm is perfectly adapted to this type of problem considering the thickness of the different layers of the sample and the size of the defects. Defects were detected, and their interpretation was possible thanks to the 3D view, such as the phenomenon of NiO grain enlargement explaining defects in the electrolyte, the effect of NiO reduction, and finally, some anomalies due to the shaping process. Ways to anticipate these defects were then proposed.

High-Temperature Proton Conduction in Covalent Organic Frameworks Interconnected with Nanochannels for Reverse Electrodialysis.

The crystalline porous organic framework offers a highly ordered and stable structure under hydrated conditions at high temperatures. Here, we demonstrated a method for preparing high-performance membrane buildup using "heterogeneous networks" and "polymer phase-separated nanochannels". A well-interconnected "nanochannel" with a "crystalline organic framework" forms a highly stable hybrid membrane above 80 °C under 100% hydration under acidic and basic conditions. The prepared structure provides a self-standing membrane that easily overcomes the problem faced by conventional high ion-exchange capacity (IEC)-based membranes such as swelling, gelling, fragility, and dissolving at elevated temperatures. Apart from structural stability, it also shows better chemical stability with enhanced proton conduction at elevated temperatures. This proton conduction with better structural stability in the high IEC sample confirms from thermal analysis, whereas it also offers relatively low in-plane membrane swelling as compared to the conventional membranes. These hybrid membranes were further combined with the FAA-3 membrane to manufacture a reverse electrodialysis system for generating a power output. We also evaluated the maximum power density (Pmax) of the stack theoretically and experimentally. The determined net power density (Pnet) is reported to be 0.45 W m-2 at a flow rate of 40 mL min-1. These results confirm that the developed membrane can withstand robustly under realistic ambient conditions maintaining stable cell performance.

Insights into Interfacial Proton Transport in Protonic Ceramic Conductors

Understanding the mechanism of proton conduction at the interface of materials enables the development of a new generation of protonic ceramic conductors at low temperatures (< 300 °C) through water absorption and proton transport on the interface. In-situ Raman spectroscopy was performed on water-saturated, porous, and nanostructured TiO2 membranes directly observe the isotope exchange reactions suggested a Grotthuss-type proton transport and faster isotope exchange rate at 175 °C than that at 25 °C with a corresponding activation energy of 9 kJ mol-1. Comparing to traditional high-temperature protonic ceramic conductors through bulk transport, water absorption on the interface in simple oxides system has higher proton mobility and similar proton concentration, indicating the interface is a facile route for proton transport. In addition, the measured hydrogen isotope exchange rates in nanostructured BCZYYb by in-situ Raman spectroscopy in the temperature range of 100-300 °C were comparable or even higher than that in fully dense BCZYYb in the range of 400-600 °C, suggesting the possibility of using the nanostructured BCZYYb membrane as an electrolyte materials in protonic ceramic fuel cells at low temperatures (<300 °C).

High performance polymer electrolyte membrane with efficient proton pathway over a wide humidity range and effective cross-linking network

It is vital to constructing long-term proton transfer channels with sufficient conduction sites in proton exchange membranes. The mPBI-TGDDM/ZrSP polymer electrolyte membranes are prepared by covalent cross-linking with tetrafunctional N,N,N′,N′-tetraglycidy-4,4′- diaminodiphenyl-methane (TGDDM) and doping with the zirconium 3-sulfopropyl phosphonate (ZrSP). The new high-temperature proton conductor ZrSP contains sulfonic acid groups and phosphonic acid groups. TGDDM has high functionality which efficiently enhanced the dimensional stability, mechanical properties, and oxidative resistance of the membranes under low cross-linking degrees (5%–10%). The low cross-linking degree and good mechanical stability also allow high doping levels of ZrSP and consequently high proton conductivity. At 100% relative humidity (RH), 50% RH and 0 RH, the proton conductivity of mPBI-TGDDM(5%)/ZrSP(50%) membrane is 0.127, 0.078 and 0.0186 S cm−1 at 180 °C, respectively. A large number of sulfonic and phosphonic acid groups in the membrane can establish an efficient proton pathway over a wide humidity range. High cross-linking will decrease the conductivity, and high doping will increase the conductivity, thus affecting the performance of the fuel cells. The mPBI-TGDDM/ZrSP membranes exhibited good methanol resistance and good membrane selectivity and thus the membranes have great application potential in direct methanol fuel cells (DMFCs).

Construction of Novel Proton Transport Channels by Triphosphonic Acid Proton Conductor-Doped Crosslinked mPBI-Based High-Temperature and Low-Humidity Proton Exchange Membranes

High proton conductivity and sufficient stability of the polybenzimidazole membrane are important for the application of high-temperature proton exchange membrane fuel cells (HT-PEMFCs). A series of composite membranes based on crosslinked mPBI (cPBI) with cerium 2,4,6-triphosphono-1,3,5-triazine (CeTPT) were resoundingly fabricated. Novel cPBI networks with tetrafunctional N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) were synthesized. It is noteworthy that a new high-temperature proton conductor CeTPT was added. CeTPT contained three phosphonic acid groups, which offered good proton conductivity at moderate-to-low humidity and had good thermal stability. Tetrafunctional crosslinker TGDDM had multiple functional groups. With a relatively low crosslinking degree (CLD), the mechanical properties, dimensional stability, and oxidative resistance of the membranes were efficiently improved. The low CLD and good physicochemical stability also allowed high doping levels of CeTPT (up to 50%) and consequently high proton conductivity. At 180 °C and 50% RH, the proton conductivity of cPBI-5-CeTPT-50 and cPBI-10-CeTPT-50 was 0.072 and 0.068 S cm–¹, respectively. The cPBI-CeTPT membranes showed good methanol resistance and membrane selectivity, and thus the membranes were suitable for direct methanol fuel cells.

Preparation and characterization of zirconium (1,3,5,2λ5,4λ5,6λ5-triazatriphosphinine-2,2,4,4,6,6-hexyl) hexa(phosphate) as a novel high-temperature proton conductor

Zirconium (1,3,5,2λ5,4λ5,6λ5-triazatriphosphinine-2,2,4,4,6,6-hexyl) hexa(phosphate) (ZrTHPA) is synthesized by chelation combination (1,3,5,2λ5,4λ5,6λ5-triazatriphosphinine-2,2,4,4,6,6-hexyl) hexa(phosphonic acid) (THPA) with zirconium ion in a certain ratio. The THPA is synthesized by hexachlorocyclotriphosphazene with P(OEt)3, and hydrolyzed in HCl. Their structure is characterized by nuclear magnetic resonance (NMR) and infrared spectroscopy (IR), and hydrogen bonding and chelation interactions between Zr4+ and phosphonic acid are detected. X-ray diffraction and scanning electron microscopy (SEM) show that ZrTHPA has a layered structure. Thermogravimetry-differential thermal analysis (TG-DTA) shows that ZrTHPA has good thermal stability. ZrTHPA also has good oxidative stability and hydrolysis resistance. The ion exchange capacity of ZrTHPA (1:2) is 2.21 meq g−1. At 180 °C, the proton conductivity of ZrTHPA (1:2) at 100%, 50%, and 0 relative humidity is 0.128 S cm−1, 0.069 S cm−1, and 0.038 S cm−1, respectively. ZrTHPA can be used as solid acid catalyst or proton conductor which is doped into proton exchange membranes.

(Invited) Mixed Protonic-Electronic Membrane Reactors; Converting Hydrocarbon Resources and CO2 to Fuels

Membrane reactor technology holds the promise to circumvent thermodynamic equilibrium limitations by in-situremoval of product species, resulting in improved chemical yields. Recent advances in mixed-conducting oxide-membrane technology present the possibility for a dramatic reduction in the cost of converting petroleum, coal and biomass derived feed stocks to hydrogen and other “value added” hydrocarbons. We have developed novel membrane reactor technology, based on high temperature proton conductors, that can convert a wide range of hydrocarbons to pure H2, and syngas for synthesis of liquid fuels and chemical feed stocks. By simultaneous H2 permeation and catalysis, we have demonstrated the ability to increase water gas shift yields >70% over thermodynamic limitations. Similarly, we have demonstrated increases in steam reforming yields, and the ability to reform CH4 with CO2.More recently we have developed single-step gas to liquid reactors that convert natural gas to C2+ products with high yields and no unwanted oxidation byproducts. The direct utilization of CH4 and CO2 to simultaneously produce C2+hydrocarbons (C2 and aromatics) and syngas (CO and H2) on opposite sides of a mixed protonic-electronic conducting SrCe0.7Zr0.2Eu0.1O3-δ membrane reactor is demonstrated. On one side (interior) of the membrane reactor, direct non-oxidative methane conversion (DNMC) over an iron/silica catalyst produces C2+ hydrocarbons and H2. On the other side (outer surface) of the membrane, permeated H2 (driving the DNMC reaction) reacts with a CO2 sweep gas to form CO and water via the reverse water gas shift (RWGS) reaction. This novel single H2-permeable membrane reactor simultaneously addresses both reduction of greenhouse gas (CO2 and CH4) emissions as well as production of value-added hydrocarbon products (C2+, CO, and H2) with in situ gas separation.

Stabilizing phosphotungstic acid in Nafion membrane via targeted silica fixation for high-temperature fuel cell application

With PWA as proton transfer and silica as water retainer, stable phosphotungstic acid/silica/Nafion (PWA/Si–N) composite membrane is non-destructively fabricated and exhibits excellent stability and high temperature proton conductivity. Compared with pristine Nafion, high temperature proton conductivity is significantly enhanced due to the collaboration between –SO3H ionic clusters and the in-situ filled silica embedded PWA nanoparticles. PWA is stabilized in the ionic clusters via in-situ catalyzing the hydrolysis silica precursor targeted filled into the –SO3H ionic clusters. Stable proton conductivity of the PWA/Si–N membrane at 110 °C and 60% RH is high to 0.058 S/cm, which is 2.4 folds of that of Nafion. At the same time, the composite membrane still maintains good mechanical and thermal stability. As a result, high temperature fuel cell performance of the composite membrane is improved by 41% compared with the pristine Nafion membrane. The in-situ coating method proved to be an effective method to solve the stability of PWA in Nafion membrane, especially the inorganic oxide with good hygroscopicity as the modifier.

Mechanochemical processing of BaZr1−yYyO3−δ (y = 0.15, 0.20) protonic ceramic electrolytes: Phase purity, microstructure, electrical properties and comparison with other preparation routes

BaZrO3-based materials have been intensively researched due to their potential application as high-temperature proton conductors in devices such as proton ceramic fuel cells (PCFCs), separation membranes and electrolysers. Nonetheless, their implementation in these devices has often been constrained due to their processing difficulties, namely the formation of Ba-deficient compositions, coexistence of separate perovskite phases or the formation of segregated phases of the acceptor dopant. In this context, the current article shows mechanosynthesis to be an efficient preparation method for Ba(Zr,Y)O3-δ materials, producing pure powders, containing nanometric crystallites, that offer good densification and grain growth. The phase formation, microstructure and electrical properties of the most promising BaZr1-yYyO3-δ compositions, with yttrium contents of y = 0.15 (BZY15) and y = 0.20 (BZY20) are investigated and compared with literature data of materials made by other processing routes. Such a comparison highlights that phase separation of such compositions, commonly reported in the literature, does not occur for these mechanosynthesised materials of high homogeneity. Furthermore, high electrical performances can be obtained by this technique that can compete with some of the best reported in the literature. Electrical conductivity as a function of both oxygen and water partial pressure, in the temperature range of 550 °C − 850 °C, are measured for both compositions and the partial conductivities of protons, oxygen vacancies and electron holes are determined from the defect model. The electron-hole conductivity of BZY20 is observed to be higher than that of BZY15 under all conditions, while proton and oxide-ion conductivities are shown to be higher for the composition BZY15.

Mechanism of Proton Conduction in Doped Barium Cerates: A First-Principles Study

Solid oxide fuel cells with high-temperature proton conductors (HTPCs) as the electrolyte have attracted intensive attention for years; however, the mechanism for proton transfer in HTPCs remains u...

Enhanced proton conduction in zirconium phosphate/ionic liquids materials for high-temperature fuel cells

This work reports the synthesis of high temperature proton conductors based on zirconium phosphate and imidazolium-based ionic liquids. This material is evaluated for high temperature proton exchange membrane fuel cells applications operating at 200 °C. The characterization results show high proton conductivity, enhanced water uptake properties, changes in structure, and exfoliation in zirconium phosphates crystal layers upon the introduction of the ionic liquid. The proton conductivity results demonstrate that there is an optimum amount of ionic liquid that can be introduced into zirconium phosphates to enhance its conductivity beyond which, the conductivity starts to decrease. At the optimum conditions, the addition of ionic liquids enhances the proton conductivity of the zirconium phosphates material by orders of magnitude. The results show a high proton conductivity the order of 10−2 S cm−1 at room temperature and high anhydrous proton conductivity of 10−4 S cm−1 at 200 °C. These findings indicate that the zirconium phosphate-ionic liquid material has a great potential as solid proton conductors for fuel cells applications operating at elevated temperatures.