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Ba0.9Sr0.1Ce0.4Zr0.6−xYbxO3−δ(x = 0.05, 0.1, 0.15, 0.2) proton-conducting electrolyte powders were synthesized by the nitrate combustion method. The effects of co-doping of Sr and Yb on the phase composition and electrochemical performance were studied. X-ray diffraction (XRD) results indicate that Sr and Yb were successfully doped into the lattice of BaCe0.4Zr0.6O3, forming a single perovskite phase. The AC impedance technique was used to investigate the total conductivity of the materials under air and water vapor atmospheres at 400–800°C. The results show that BSCZY20 demonstrated the highest electrical conductivity of 0.033 S cm−1 at 800°C in water vapor. This suggests that the co-doping strategy can effectively enhance the conductivity of BaCe0.4Zr0.6O3 proton-conducting material, which provides valuable insight for the development of high-performance proton-conducting solid oxide fuel cells. [ABSTRACT FROM AUTHOR]

The present study explores a nano-grained perovskite material for use in an intermediate-temperature solid oxide fuel cell. Electrolytes with the formula Ba1−xCaxCe0.8Nd0.2O3−δ (BCCN), where x = 0.0, 0.01, 0.02, 0.03, 0.04, and 0.05, were synthesized through the sol–gel auto-combustion process. Structural, surface morphology and vibrational analyses were conducted through XRD, SEM, FTIR, and Raman studies. Scherer's formula revealed predicted crystallite sizes for the electrolyte materials ranging from 25.13 to 38.69 nm. Morphological assessments determined grain diameters between 1 to 3 µm. Raman spectroscopy identified the 355 cm−1 vibrational mode associated with CeO6 octahedra, while FT-IR identified bands corresponding to M–O vibrations. Electrical impedance spectroscopy results indicated ionic behavior conducive to electrolytes, with overall conductivities increasing with measurement temperature. Notably, bulk conductivity surpassed grain boundary conductivity, with the highest overall conductivity observed in x = 0.05 compositions among the examined perovskite oxides. [ABSTRACT FROM AUTHOR]

To study the electrochemical properties of Yb-doped CaZrO3 in more detail, the CaZr1−xYbxO3−δ (x = 0.000, 0.025, 0.050, 0.075, and 0.100) solid electrolyte specimens were prepared by high-temperature solid-state method at the temperatures of 1523 K and 1873 K for 8 h. XRD, SEM, EDS, and electrochemical workstation were used to test the micromorphology and electrochemical performance of the electrolyte samples. When the doping amount of Yb is 0.05, the electrolyte sample has excellent electrical properties. The total conductivity of electrolyte CaZr0.95Yb0.5O3−δ is 1.13 × 10−5 to 1.28 × 10−3 S/cm and the conductivity activation energy falls in 0.69–1.34 eV in hydrogen and oxygen atmosphere at 973–1173 K. The chemical diffusion coefficient of hydrogen in CaZr0.95Yb0.05O3−δ electrolyte is between 1.55 × 10−6 and 5.82 × 10−6 cm2/s in the temperature range of 973 to 1373 K, and the diffusion activation energy is 12,278 kJ/mol. [ABSTRACT FROM AUTHOR]

As the third generation of fuel cells, solid oxide fuel cell (SOFC) provides a clean and low-pollution technology. Electrolyte material, which often plays a vital role in SOFC, has always been the focus and difficulty of research. Y-doped barium cerate-based proton conductor electrolyte, BaCe1–xYxO3–δ (x = 0, 0.05, 0.1, 0.15), were prepared using the nitrate-citrate-glycine combustion method. A series of tests and characterizations were performed to examine the structural, morphological, and electrical properties. X-ray diffraction (XRD) analysis proved that the BCY powders with pure cubic perovskite structure were formed after calcined at 1100 °C. SEM results showed that the BCY ceramics sintered at 1350 °C were dense and well-developed grains. The electrochemical performance of BCY proton conductor electrolyte was determined using the electrochemical impedance spectroscopy in dry air and wet air atmosphere at 400–800 °C. Results showed that Y-doped BaCeO3-based material had superior conductivity in air and the conductivity of proton conductor was significantly improved under wet air environment. Furthermore, the electrical conductivity of BCY samples was related to the amount of Y3+ doping. The conductivity in a water vapor environment achieved a maximal value of 0.039 S cm−1 at 800 °C when x = 0.15. So BaCe1–xYxO3-based materials can be used as a proton conductor electrolyte for SOFC in the medium temperature range. [ABSTRACT FROM AUTHOR]

A new decavanadate hybrid material, (C4H7N2S)4[H2V10O28]·4H2O, (2A4MT V10), was successfully grown in aqueous solution as single crystals with acidic decavanadate (V10) cluster and 2-amino-4-methyltiazolium (2A4MT) cation. It was thoroughly characterized by XRD, IR, DTA-TGA and alternating current impedance spectroscopy measurements. Crystal structure of (2A4MT V10) exhibits a typical 3D-porous supramolecular topology of diprotonated V10 clusters and water molecules featuring tunnel-voids filled with 2A4MT cations mainly connected through O···H/H···O, H bonding with considerable contributions of 65.9% as indicated by Hirshfeld surface analysis. The conductivity study shows that the hybrid crystal possesses significant conductivities above 10−4 S cm−1 in the temperature range of 130–180 °C to rich 9 × 10−4 S cm−1 at 423 K (150 °C), which can be considered as promising proton conductor for fuel cell applications. [ABSTRACT FROM AUTHOR]

The fourth industrial revolution indispensably brings explosive data processing and storage; thus, a new computing paradigm based on artificial intelligence-enabling device structure is urgently required. Memristors have received considerable attention in this regard because of their ability to process and store data at the same location. However, fundamental problems with abrupt switching characteristics limit their practical application. To address this problem, we utilized the concept of metaplasticity inspired by biosystems and observed gradual switching in the peptide-based memristor at high proton conductivity. An unexpectedly high slope value > 1.7 in the log/-V curve at low voltage (≤ 400 mV) was considered the main origin, and it might arise from the modulatory response of proton ions on the threshold of Ag ion migration in the peptide film. With the obtained gradual switching property at high proton conductivity, the device showed significantly increased accuracy of image recognition (∼ 82.5%). We believe that such a demonstration not only contributes to the practical application of neuromorphic devices but also expands the bioinspired functional synthetic platform. [ABSTRACT FROM AUTHOR]

A concept for electrolytic water splitting is presented, applying super-proton-conducting cesium-dihydrogen-phosphate (CsH2PO4) mixed with polyvinylbutyral shaped as disks. Our two-chamber pilot setup enabled continuous water electrolysis at above ~ 240 °C/26 bar of argon/water. Anodes consisted of ruthenium-dioxide (RuO2) and cathodes of nickel or platinum-coated steel felts. The conditions during electrolysis (flow rates of H2O, current density) were investigated. The water vapor pressure in the anode chamber had a decisive influence on the electrolysis efficiency: the CsH2PO4 electrolyte needs a stable supply of humidity to retain its super-proton-conductivity. H2O forms O2 gas at the anode and H+ ions depart to the cathode and react with electrons to form H2. Without stable water addition, higher potentials are needed to maintain efficiency for stable current densities. Our investigations also comprised measurements of polarization curves at ~ 240 °C for Ru-coated steel anodes and Ni or Pt cathodes, with the latter reaching a current density of 250 mA/cm2 at 2 V. [ABSTRACT FROM AUTHOR]

Bulk solid-state polyantimonic-acid-(PAA)-based proton-conducting membranes were manufactured via cold isostatic pressing using an inert polymeric binder. Precursor PAA powder was obtained using stepwise aqueous hydrolysis of antimony pentachloride. X-ray diffraction (XRD) data showed that hydrolysis resulted in crystalline PAA with the pyrochlore structure. The composition of the powder obtained via solid-state synthesis corresponded to sodium antimonate having the ilmenite structure. The logarithm of the conductivity of PAA membranes in air was linearly dependent on inverse temperature in the range 293 – 452 K. Based on XRD and conductivity data, the obtained solid-state PAA-based membranes were prospective proton conductors having a conductivity of 10–4 S/m and an activation energy of conductivity of 0.395 eV. [ABSTRACT FROM AUTHOR]

Protonic ceramic fuel cells have become extremely interesting due to their high power output at the intermediate temperature range (400–700 °C). Significant progress has been made to develop electrolyte materials, doped barium cerates-zirconate, which gets the leading role due to its high chemical stability and high ionic conductivity. Here, we present a new composition BaCe0.5Zr0.3Y0.1Yb0.05Zn0.05O3-δ (BCZYYbZn05), where addition of 5 mol% Zn with Ce, Zr, Y, and Yb at the B-site of the perovskite material shows high stability with high conductivity. The material was synthesized by solid-state reaction route at 1400 °C which showed 98% relative density. Rietveld analysis of neutron powder diffraction data reveal an orthorhombic structure with Pbnm space group. Thermogravimetric analysis shows about 1.06% weight loss from 200 to 1000 °C which is mainly related to the formation of the oxygen vacancies. In wet hydrogen atmosphere, this material shows higher conductivity and lower activation energy than dry hydrogen atmosphere indicates the conduction type as protonic conduction. The anode-supported single test cell based on this electrolyte material demonstrates peak power densities 649 mW cm−2 at 700 °C using conventional BSCF cathode, representing an important step toward commercially viable SOFC technology. [ABSTRACT FROM AUTHOR]

To understand electrochemical properties of the rare earth-doped CaZrO3 system in more detail, a solid-state electrolyte Er-doped CaZrO3 was successfully prepared using solid-state reaction method at the temperatures of 1673 K and 1823 K for 10 h. The microstructures and electrochemical properties of these materials were systemically investigated. The results from structural analysis showed that the electrolyte has a pure perovskite phase structure. According to the H/D isotope effect, protons were determined as the dominant charge carriers in hydrogen atmosphere between 773 and 1273 K. The electrochemical impedance spectroscopy test showed that ionic electrical conductivities are approximately 1.86 × 10−8 ~ 2.93 × 10−4 S/cm at 773 ~ 1273 K, and ionic conductance activation energy (Ea) is in the range of 0.823–1.416 eV, Furthermore, ionic electrical conductivity decreases with increasing Er2O3 doping amount, which is completely different from that of In2O3 or other dopant-doped CaZrO3. The abnormal phenomenon is associated with the defect association introduced by incorporation of Er2O3 into CaZrO3 lattice on the basis of the DFT calculation. [ABSTRACT FROM AUTHOR]

The construction of inorganic porous frameworks from discrete polyoxometalate (POM) units is a major research challenge. Herein, a three-dimensional (3D) all-inorganic porous structure {Mo154}n that consists of classic Mo154 rings connected by Mo-O-Mo covalent bonds was synthesized. Interestingly, the proton conductivity of the 3D-{Mo154}n framework is 1.1×10−2 S cm−1 at 22 °C and 100% relative humidity (RH), which is one of the highest proton conductivities reported thus far for POM-based conductive materials. Compared to the discrete {Mo154} cluster and 1D-{Mo154}n, the enhanced conductivity of 3D-{Mo154}n suggests that assembling POM-based all-inorganic porous frameworks is a promising method for designing proton-conductive materials. [ABSTRACT FROM AUTHOR]

In this work, a series of CaHf1-xScxO3-α (x = 0, 0.10, 0.15, 0.20, and 0.30) perovskite oxides have been prepared by a solid-state reaction. The crystal structure and lattice parameters of the orthogonally-distorted perovskite phases of CaHf1-xScxO3-α were obtained. The results revealed that Sc-doping could significantly improve the conductivity and proton transport properties of CaHfO3. However, at x > 0.2, the conductivity decreased with increase in Sc concentration. CaHf0.85Sc0.15O3-α exhibited the highest conductivity among all specimens in the temperature range of 400 to 900 °C. The conduction activation energy of CaHfO3 significantly decreased with Sc-doping in the range of 0.66 to 1.52 eV. Overall, the CaHf1-xScxO3-α demonstrated pure proton conduction in the temperature range of 300 to 600 °C under wet 1%H2-Ar, whereas the proton relative transport number decreased with increasing temperature to within the range of 600–900 °C. At an optimal Sc concentration of x = 0.1, CaHf1-xScxO3-α rendered the highest proton transport number. [ABSTRACT FROM AUTHOR]

Lithium dihydrogen phosphate, LiH2PO4 (LDP), was studied for water electrolysis at elevated temperatures. It is shown that pure LDP, melting at ~ 224 °C and with correct DSC and X-ray diffraction diagram, in presence of sufficient humidity is stable up to 360 °C. Both solid and liquid LDP is structurally disordered and superprotonic conducting with conductivities reaching 0.48 S*cm−1, when determined in sealed conductivity cells. The vapor pressure above LDP, pure and mixed with LiPO3 or H2O, was determined by means of Raman spectroscopy based on N2 as internal reference gas. Pressures up to ~ 20 bar at 350 °C were found and conductivities are given for solid and liquid states. Water splitting by electrolysis, 2H2O ➔ 2H2 + O2, was demonstrated by Raman spectroscopy at ~ 225 °C and ~ 4.2 bar with Pt/W electrodes, thus showing that molten LDP has a significant potential for elevated temperature water electrolysis with high efficiency. [ABSTRACT FROM AUTHOR]

Transition-metal oxide perovskites usually exhibit mixed ionic and electronic conductivity and have been widely investigated as electrode materials for use in solid-oxide fuel cells. Recently, samarium nickelate SmNiO3 was found experimentally to show promising potential for use in proton-conducting fuel cells. To understand the ionic conductivity of SmNiO3, the oxygen and proton diffusion therein are investigated via density functional theory calculations in this work. Based on the vacancy hopping mechanism, oxygen diffusion in SmNiO3 shows a migration barrier of 0.84 eV. The proton diffusion is studied in terms of different diffusion mechanisms, including reorientation, intraoctahedral, and interoctahedral hopping. The migration barrier for intraoctahedral migration is calculated to be lower than that for interoctahedral hopping. To realize long-range diffusion, the proton is predicted to exhibit reorientation and intraoctahedral hopping. These findings provide a theoretical guide for the development of mixed ionic and electronic perovskite conductors. [ABSTRACT FROM AUTHOR]

Synthesis of the proton-conducting electrolyte SrZr0.9Y0.1O3−δ(SZY) was undertaken by the sol–gel method employing an all-alkoxide route from reaction of strontium alkoxide produced in-situ and commercial zirconium and yttrium alkoxides. The solution was homogenized by a previous ligand exchange in 2-methoxyethanol to control the polycondensation rate and achieve SZY at the low final firing temperature of 700–800 °C. SZY thin films (~270 nm) were assisted by dip-coating on different substrates and characterized by scanning and transmission electron microscopy, grazing X-ray diffraction and confocal micro-Raman spectroscopy, revealing well-crystallized SZY phase with orthorhombic symmetry (space group, Pnma). Impedance spectroscopy of a thin film deposited on a quartz substrate revealed that protons contribute to transport in wet conditions as confirmed by a lower conductivity in D2O-humidified air (1.02 eV) compared to H2O-wetted air (0.99 eV), with the difference in activation energy consistent with a conductive isotope effect. Highlights: Proton-conducting electrolytes SrZr0.9Y0.1O3−δ thin-films were successfully obtained. Novel all-alkoxide sol–gel route via in-situ synthesis of triple alkoxide was performed. Ligand exchange in 2-methoxyethanol allows soft thermal treatment SZY thin-film was well crystallized at low temperature and time (700 °C, 1 h). Protonic electrical contribution is present in wet conditions. SZY thin-films synthesized at 700 °C present similar conductivity than a pellet at 1300 °C. [ABSTRACT FROM AUTHOR]

Y-doped BaZrO3 (BZY) is a promising candidate for electrolytes in protonic ceramic fuel cells. To achieve the high proton conductivities of sintered electrolyte membranes, the poor sintering nature is one of the problems because of the high resistance at grain boundaries. To obtain single-phase BZY with sufficient grain growth (> 1 μm), the information of phase stable conditions of BZY is important. However, in previous studies, there are discrepancies in the single-phase composition range of BZY, and the phase relationships between BZY and other phases at a sintering temperature (1600 °C). In this work, we clarified the phase stable conditions of BZY by reexamining the critical part of the phase diagram of the BaO-ZrO2-Y2O3 system. Based on X-ray diffraction, at certain temperatures below 1600 °C, the single-phase composition range of BZY is not continuous at ~ 10% in the molar ratio of Y/(Zr + Y). Even when sintering at 1600 °C, this separate region probably retards the formation of single-phase and grain growth. Besides, we revealed the other ternary phases, i.e., γ phase and Zr-substituted Ba3Y4O9 are stable in XBaO < 50 mol% and can coexist with BZY at 1600 °C. This information is discussed on the Gibbs triangles and should be useful for all researchers working on BZY. [ABSTRACT FROM AUTHOR]

Simulation of proton ceramic fuel cell is of great importance in understanding their working mechanisms. Cathode activation polarization is a critical concern in the simulation. In this paper, Sm0.5Sr0.5CoO3−δ–Ce0.8Sm0.2O2−δ cathode is selected as studied case. The effective reaction order, which is the exponential of the oxygen partial pressure in cathode Butler-Volmer equation, is determined via our model. The dominant process in cathode reaction is investigated and identified. Among the involved reaction steps, model result points out that the surface diffusion of absorbed oxygen ion is dominant, which is in accord with the report. Moreover, single button cells with BaCe0.7Zr0.1Y0.2O3−δ electrolyte and Sm0.5Sr0.5CoO3−δ–Ce0.8Sm0.2O2−δ cathode are prepared, and the measured cell output voltages are compared with the simulated ones. The predicted cell outputs via our full cell simulation match the measurements under diverse experimental settings, suggesting that the method and parameters in our simulation are applicable. Our models facilitate both the analysis of experimental results and the development of proton-conducting solid oxide fuel cell model. [ABSTRACT FROM AUTHOR]

In order to investigate the effects of Na2CO3/ZnO co-addition on the sinterability and electrical conductivity of BaZr0.1Ce0.7Y0.1Sc0.1O3-δ (BZCYSc) ceramic, Na2CO3 and ZnO were added and BZCYSc/ZnO/Na2CO3 ceramic was prepared by mechanical ball milling and high-temperature sintering in air. The crystalline structure, micro-morphology, chemical composition, density, and electrical conductivity of the sintered ceramics were characterized by XRD, SEM, EDS, Archimedes method, and electrochemical impedance spectrum, respectively. The grains size of BZCYSc-2%ZnO-5%Na2CO3 is about 2.5~5 μm. Na2CO3/ZnO co-addition is beneficial to improve the sinterability and electrical conductivity of BZCYSc. The sintering temperature of BZCYSc can be lowered from 1550 to 1350 °C when 2 mol%ZnO is added. At 550 °C, the electrical conductivities of BZCYSc-2%ZnO-10%Na2CO3 and BZCYSc are 1.90 × 10−3 S/cm and 1.81 × 10−3 S/cm. The activation energies of BZCYSc and BZCYSc-2%ZnO-10%Na2CO3 are 0.7529 eV and 0.5641 eV, respectively. [ABSTRACT FROM AUTHOR]

A solid-state electrolyte CaZr0.98−xIn0.02AlxO3−α (x = 0.002, 0.004, 0.006, and 0.008) was prepared using a solid-state reaction method at the temperatures of 1823 K and 1873 K for 10 h. The structures, micromorphologies, and electrical conductivities of these materials were investigated. The results show that CaZr0.98−xIn0.02AlxO3−α has a pure CaZrO3 perovskite phase structure. The electrical conductivities are approximately 1.86 × 10−8–7.13 × 10−6 S/cm at 1073–1273 K, and they significantly increase with increasing temperature under the same atmospheric conditions and gradually increase with increasing water vapor or oxygen partial pressure. This high-temperature proton conductor material would be used as hydrogen sensors of molten metals. [ABSTRACT FROM AUTHOR]

Heterointerfaces introduce unique localized defects into ionic conductors. This study explores the nanoionic characteristics exhibited by the proton-conducting oxides SrZr0.9Y0.1O3-δ and SrCe0.95Yb0.05O3-δ including finely dispersed precipitated platinum nanoparticles. The electrical conductivity of both the platinum-doped oxides revealed reversible nanoionic phenomena caused by the exsolution of the platinum in the form of platinum nanoparticles, at 0.5 vol% relative to the metal oxides, and dissolution in response to a change in gas atmosphere. In comparison with the original conductivity of SrZr0.9Y0.1O3-δ and SrCe0.95Yb0.05O3-δ, the conductivity of platinum-doped SrZr0.9Y0.1O3-δ decreased significantly in a wet hydrogen atmosphere, whereas platinum-doped SrCe0.95Yb0.05O3-δ showed almost no decrease in conductivity in the same atmosphere. The different responses of the two materials to the change in gas atmosphere are discussed in relation to the precipitation of platinum nanoparticles. [ABSTRACT FROM AUTHOR]

Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) is one of the most active cathode materials and shows significant hydration effect suggesting possible proton conductivity. In this study, the performance of BSCF cathode on a proton-conducting BaZr0.1Ce0.7Y0.2O3−δ (BZCY) electrolyte with silver and gold current collectors was determined. The electrochemical characteristics of the symmetrical and anode-supported cell with diluted silver electrode, silver current collector or gold current collector on BSCF electrode were compared. The significant result is that, although the diluted silver electrode itself shows poor operation stability, the silver current collector has strong electrocatalytic contribution to the BSCF cathode performance on the proton-conducting electrolyte, leading to higher cell performance than that with the gold current collector. [ABSTRACT FROM AUTHOR]

The paper reports the effect of SiO2 nano-filler on structural, thermal, and ion transport properties of polymer electrolyte system comprising polyvinyl alcohol (PVA) and 1-butyl-3-methylimidazolium hydrogen sulfate [C4C1Im][HSO4] ionic liquid. The addition of SiO2 nano-filler results into enhancement in amorphicity and thermal stability and lowering of glass transition temperature of the membranes. A detailed investigation of possible interactions among the constituents PVA, [C4C1Im][HSO4] and SiO2, and cation-anion and anion-anion pairs of [C4C1Im][HSO4] in the polymer electrolyte and their dissociation due to SiO2 filler has been carried out in the membranes using Fourier transform infra-red (FTIR) and Raman spectroscopy. The membranes show maximum room temperature ionic conductivity as 9.9 × 10−3 S cm−1 for 6 wt.% of the nano-filler which is about four times higher than the membrane without nano-filler and an order higher than pure [C4C1Im][HSO4]. With temperature, the ionic conductivity shows VTF behavior in the temperature range 40-120 °C. On the basis of FTIR and ion transport results, a model for ion transport in the membranes is proposed.Schematic model of ion transport in nanocomposite polymer electrolyte membrane of PVA-[C4C1Im][HSO4]-SiO2 [ABSTRACT FROM AUTHOR]

The paper reports the effect of SiO2 nano-filler on structural, thermal, and ion transport properties of polymer electrolyte system comprising polyvinyl alcohol (PVA) and 1-butyl-3-methylimidazolium hydrogen sulfate [C4C1Im][HSO4] ionic liquid. The addition of SiO2 nano-filler results into enhancement in amorphicity and thermal stability and lowering of glass transition temperature of the membranes. A detailed investigation of possible interactions among the constituents PVA, [C4C1Im][HSO4] and SiO2, and cation-anion and anion-anion pairs of [C4C1Im][HSO4] in the polymer electrolyte and their dissociation due to SiO2 filler has been carried out in the membranes using Fourier transform infra-red (FTIR) and Raman spectroscopy. The membranes show maximum room temperature ionic conductivity as 9.9 × 10−3 S cm−1 for 6 wt.% of the nano-filler which is about four times higher than the membrane without nano-filler and an order higher than pure [C4C1Im][HSO4]. With temperature, the ionic conductivity shows VTF behavior in the temperature range 40-120 °C. On the basis of FTIR and ion transport results, a model for ion transport in the membranes is proposed.Schematic model of ion transport in nanocomposite polymer electrolyte membrane of PVA-[C4C1Im][HSO4]-SiO2 [ABSTRACT FROM AUTHOR]

Single phase polycrystalline BaZrCeYYbO electrolyte material was prepared by solid state reaction route. Rietveld analysis of the XRD data confirms the tetragonal symmetry in the I4/mcm space group with unit cell parameters of a = b = 6.0567(3) Å and c = 8.5831(5) Å. The addition of ZnO as a sintering additive was found to reduce the sintering temperature and enhance both overall sinterability and grain growth. Sintering temperature was reduced by 200-300 °C, and a very high relative density of about 98% was achieved at 1400 °C. Impedance spectroscopy in humidified 5% H/Ar atmosphere shows that the protonic conductivity at 600 °C was 8.60 × 10 S cm. Thermal analysis performed in pure CO atmosphere shows very good chemical stability up to 1200 °C. Good biaxial flexure strength of 100-200 MPa was reported which makes this material a promising electrolyte material for intermediate temperature solid oxide fuel cells (IT-SOFCs). [ABSTRACT FROM AUTHOR]

Proton-conducting ceramics have been very useful due to their potential applications in fuel cells, electrolysers, and hydrogen membranes. The proton-conducting fuel cell electrolytes (BaSr)(CeZrY)O ( x = 0-1.0) have been synthesized through sol-gel method and characterized with regard to phase, structural stability, and electrical conductivity. The structural behavior has been investigated by X-ray diffraction and theRaman spectroscopy. The XRD analysis shows perovskite-type cubic structure and values of lattice parameter lie in the range of ~4.29 to ~4.40 Å. Strontium substitution leads to lattice contraction, strengthening of the metal-oxygen bond, and increase of oxygen content (3− δ). The Raman spectra show different types of stretching/vibrations corresponding to octahedral, M-O stretching, and oxygen vacancies. The electrical conduction was found to be protonic in nature and decreases with increase of strontium insertion. The composition x = 0.4 shows relatively better structural stability against humid air/boiling water condition while inferior in carbon dioxide atmosphere. [ABSTRACT FROM AUTHOR]

Ceramic-based proton conductors enable high-temperature hydrogen economy applications such as hydrogen separation membranes, fuel cells, and steam electrolyzers. BaZrYO (BZY) proton-conducting oxide possesses the highest level of proton conductivity reported to date, but poor sinterability hinders its widespread utilization. In this paper, we report a two-step reactive aid sintering (TRAS) method involving the introduction of BaCO and BO-LiO for the preparation of dense BZY ceramics sintered at 1500°C. The resulting BZY samples showed a pure perovskite structure with a dramatic increase in the relative density to 91.5%. In addition, the shrinkage during sintering was improved to 19.3% by a TRAS method as compared to 2.6% by the conventional solid date reaction method. The bulk conductivity was improved due to enhanced densification, while the grain boundary conductivity decreased due to the blocking behavior of the sintering aid resulting in a decrease in the total conductivity of the samples. [ABSTRACT FROM AUTHOR]

The results of studies of polyantimonic crystalline acid with the composition of SbO · 3.2HO using the impedance spectroscopy technique at low temperatures are presented. Dependences of dielectric permittivity, slope of dielectric losses, and electric module are studied in the frequency range of 100 Hz to 2MHz and temperature range of 220-290 K. It is shown that the limiting stage is proton transport through crystal interface. The activation energy of proton conductivity is 50.21 kJ/mol. [ABSTRACT FROM AUTHOR]

Iron sulfophenyl phosphate (FeSPP) is successfully synthesized by an optimized process from the reaction of iron chloride and m-sulfophenyl phosphonic acid (msPPA) by a simple and environmentally friendly method. Experimental results show FeSPP has a kind of layered structure, and multilayer sheet is about 2 nm thick. FeSPP exhibits good thermal stability and does not decompose under 200 °C. Protons transfer through vehicle and Grotthuss mechanisms at different relative humidities (RH). The conductivity of FeSPP can reach to 0.115 S/cm at 180 °C and RH = 100 %. Under this condition, vehicle mechanism plays the leading role, and the Grotthuss mechanism plays the minor role. At low RH, Grotthuss plays the leading role, and vehicle plays the minor role. In a drying oven at 180 °C, the proton conductivity remains 2.15 × 10 S/cm. Good conductivities at different RH and thermal stabilities clearly demonstrate that FeSPP is a highly effective conductor. It can be used as catalysts, chemical sensors, and in the preparation of composite membrane. [ABSTRACT FROM AUTHOR]

Effects of cobalt addition on structural, thermal and electrical properties of praseodymium-yttrium co-doped barium cerates have been investigated. Relative densities >98 % have been achieved after sintering at 1400 °C or 1500 °C for only 1 h. All studied compounds are stable in ambient air up to the measured 900 °C and, in reducing atmosphere (both wet and dry 5 % H-Ar) up to the measured 800 °C. The Co-free sample (BaCeYPrO) exhibits the highest conductivity of 1.21 × 10 S cm at 700 °C in air while the corresponding cobalt containing sample (BaCeYPrCoO) has a conductivity of 9.85 × 10 S cm at 700 °C in air. Cobalt addition allows the ability to retain much larger amounts of water to be retained as suggested by the higher conductivities obtained in wet hydrogen compared to the values in dry reducing atmosphere. This latter phenomenon is of special interest as it suggests the possibility of higher ionic conductivities in water-containing atmosphere and would benefit to intermediate- and high-temperature solid oxide fuel cells and/or electrolysers. The thermal expansion coefficients for the Co-free and Co-containing samples were around 12.0 × 10 K between 25 and 1000 °C. [ABSTRACT FROM AUTHOR]

In order to prepare high proton conducting oxide with high chemical stability against CO at 600-800 °C, preparation of BaCeZrYO was examined. Almost single-phase could be prepared for the specimens with x = 0.0-0.2 by Pechini method. Reaction kinetics between BaCeZrYO and CO could be explained by Jander model. With increasing Zr content up to 0.2, apparent rate constant determined from Jander plot decreased by about one order, showing improvement of kinetic stability against CO. It was also clarified that influence of partial Zr substitution on electrical property was slight, leading to the conclusion that BaCeZrYO exhibited both high kinetic stability against CO and relatively high proton conduction. [ABSTRACT FROM AUTHOR]

The effect of zinc oxide as a sintering aid on proton migration across a barium zirconate super cell with a Σ5 (310)/[001] tilt grain boundary was investigated using density functional theory. The proton was trapped by high energy barriers in the range of 1.28-1.49 eV near the zinc ion that was substituted for a zirconium ion at the grain boundary. However, there were available pathways for proton migration across the grain boundary away from the zinc ion with relatively low energy barriers in the range of 0.61-0.78 eV. Therefore, the zinc ion located at the grain boundary did not affect the energy barrier for proton migration, although the number of mobile protons could decrease as a result of being trapped near the zinc ion. [ABSTRACT FROM AUTHOR]

A proton-conducting nanocomposite gel polymer electrolyte (GPE) system, [35{(25 poly(methylmethacrylate) (PMMA) + 75 poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP)) + xSiO} + 65{1 M NHSCN in ethylene carbonate (EC) + propylene carbonate (PC)}], where x = 0, 1, 2, 4, 6, 8, 10, and 12, has been reported. The free standing films of the gel electrolyte are obtained by solution cast technique. Films exhibit an amorphous and porous structure as observed from X-ray diffractometry (XRD) and scanning electron microscopy (SEM) studies. Fourier transform infrared spectrophotometry (FTIR) studies indicate ion-filler-polymer interactions in the nanocomposite blend GPE. The room temperature ionic conductivity of the gel electrolyte has been measured with different silica concentrations. The maximum ionic conductivity at room temperature has been observed as 4.3 × 10 S cm with 2 wt.% of SiO dispersion. The temperature dependence of ionic conductivity shows a typical Vogel-Tamman-Fulcher (VTF) behavior. The electrochemical potential window of the nanocomposite GPE film has been observed between −1.6 V and 1.6 V. The optimized composition of the gel electrolyte has been used to fabricate a proton battery with Zn/ZnSO·7HO anode and PbO/VO cathode. The open circuit voltage (OCV) of the battery has been obtained as 1.55 V. The highest energy density of the cell has been obtained as 6.11 Wh kg for low current drain. The battery shows rechargeability up to 3 cycles and thereafter, its discharge capacity fades away substantially. [ABSTRACT FROM AUTHOR]

A series of Ba(CeZr)YO solid solutions (0.05 ≤ x ≤ 0.30) were prepared by solid-state reaction method. XRD results reveal that samples with 0.05 ≤ x ≤ 0.20 are homogenous perovskite phases, while the samples with x ≥ 0.25 contain impure phase (identified YO), and solubility limit of Y in BaCeO-BaZrO solid solutions is estimated as x ≈ 0.23. Samples are dense with average grain size in the range of 3-4 μm from SEM observations when Y dopant content is less than solubility limit. The solid solutions are relatively stable in CO and boiling water except a small amount of amorphous phases forming for Ba(CeZr)YO in boiling water. Impedance spectra reveal a strong influence of Y concentration on electrical conductivity and apparent activation energy of Ba(CeZr)YO. The sample with x = 0.20 has the maximal electrical conductivity and minimal apparent activation energy. At 800 °C, the total conductivity of Ba(CeZr)YO proton conductor in air is 2.07 × 10 S·cm, and apparent activation energy is 72 kJ mol. Several different sites are occupied by protons in these materials from infrared absorption spectra. Furthermore, it is found that the intensity of O-H bands can be related to the dopant concentration dependence of the electrical conductivity. [ABSTRACT FROM AUTHOR]

The proton conduction properties of sulfuric acid-modified nano-titania prepared by impregnation method were investigated. The proton conductivity of sulfuric acid-modified nano-titania was almost the same as that of hydrous sulfated nano-titania investigated in our previous work when the amount of adsorbed sulfate groups was almost the same. The highest conductivity was obtained at an adsorbed sulfate group amount of 0.42 mmol/g, not 0.97 mmol/g. This result indicates that the enhancement of conductivity with increasing amount of adsorbed sulfate groups is limited. This might be attributable to insufficient water molecule adsorption on the Ti site coordinated with a bidentate sulfate group due to the prevention by excess sulfuric acid. [ABSTRACT FROM AUTHOR]

The proton-conducting polymer electrolytes based on poly ( N-vinylpyrrolidone) (PVP), doped with ammonium chloride (NHCl) in different molar ratios, have been prepared by solution-casting technique using distilled water as solvent. The increase in amorphous nature of the polymer electrolytes has been confirmed by XRD analysis. The FTIR analysis confirms the complex formation of the polymer with the salt. A shift in glass transition temperature ( T) of the PVP/NHCl electrolytes has been observed from the DSC thermograms which indicates the interaction between the polymer and the salt. From the AC impedance spectroscopic analysis, the ionic conductivity of 15 mol% NHCl-doped PVP polymer complex has been found to be maximum of the order of 2.51 × 10 Scm at room temperature. The dependence of T and conductivity upon salt concentration has been discussed. The linear variation of the proton conductivity of the polymer electrolytes with increasing temperature suggests the Arrhenius type thermally activated process. The activation energy calculated from the Arrhenius plot for all compositions of PVP doped with NHCl has been found to vary from 0.49 to 0.92 eV. The dielectric loss curves for the sample 85 mol% PVP:15 mol% NHCl reveal the low-frequency β relaxation peak pronounced at high temperature, and it may be caused by side group dipoles. The relaxation parameters of the electrolytes have been obtained by the study of Tanδ as a function of frequency. [ABSTRACT FROM AUTHOR]

The results of concentration cell electromotive force methods (EMF) and electrochemical impedance spectroscopy measurements on the pyrochlore system SmCaTiO are presented. The data have been used to estimate total and partial conductivities and determine transport numbers for protons and oxide ions under various conditions. The EMF techniques employed include corrections for electrode polarisation resistance. The measurements were performed using wet and dry atmospheres in a wide $$ {p_{{{{\rm{O}}_{{2}}}}}} $$ range using mixtures of H, N, O, and HO in the temperature region where proton conductivity was expected (500-300 °C). The impedance measurements revealed the conductivity to be mainly ionic under all conditions, with the highest total conductivity measured being 0.045 S/m under wet oxygen at 500 °C. Both bulk and grain boundary conductivity was predominantly ionic, but electronic conductivity appeared to play a slightly larger part in the grain boundaries. EMF data confirmed the conductivity to be mainly ionic, with oxide ions being the major conducting species at 500 °C and protons becoming increasingly important below this temperature. [ABSTRACT FROM AUTHOR]

Ammonia is one of the most produced chemicals worldwide, and it is not only a major end product but also an important energy storage intermediate. The solid-state electrochemical synthesis of ammonia has the promise to overcome the limitations of the conventional catalytic reactors such as the limited conversion, severe environmental pollution and high energy consumption. Solid-state electrolytes either protonic or oxide ion conductors have been reviewed and particular emphasis is placed on their application to synthesise ammonia. The highest rate of ammonia formation according to the type of electrolyte utilised were in the following order; solid polymers > CeGdO-(Ca(PO)-KPO) composites > fluorites > perovskites > pyrochlores although the catalysts in electrodes also play an important role. The highest rate reported so far is found to be 1.13 × 10 mol s cm at 80 °C with a potential of 2 V using Nafion membrane, SmFeCuNiO (SFCN), and Ni-CeSmO as solid electrolyte, cathode and anode, respectively. Synthesising ammonia from steam and N, by-passing H stage offers many advantages such as reduction of device numbers and then the overall costs. The factors affecting the rate of ammonia formation have been discussed as well. [ABSTRACT FROM AUTHOR]

new solid-state hydrogen reference electrode has been developed that is based on the two-component two-phase mixture of β-zirconium and δ-zirconium hydride, and is suitable for use in conjunction with the high-temperature proton-conducting CaZrInO solid electrolyte. Coulometric titration studies have confirmed the presence of a true two-phase plateau, existing over a wide composition range, which may be exploited as a precision thermodynamic buffer for reference hydrogen partial pressure. Cell voltage measurements have demonstrated that potentiometric hydrogen sensors incorporating this reference electrode exhibit Nernstian response over a broad range of temperature and hydrogen partial pressure, as well as excellent thermal cycling and long-term stability. The new solid-state hydrogen reference electrode is of considerable technological relevance and has already found application in a commercialised sensor unit. [ABSTRACT FROM AUTHOR]

Continuing previous reviews on mixed-conducting electrodes for intermediate-temperature solid oxide fuel cells (IT SOFCs), this work presents a short overview of novel cathode and anode materials, their electrochemical performance in contact with oxygen anion- and proton-conducting solid electrolytes, and specific features determining possible applications. Priority was given mainly to recent research reports published during the last 2-5 years. Particular emphasis is focused on the relevant methodological aspects, potential limitations and drawbacks, and factors affecting electrode polarization and durability. Typical ranges of the polarization resistances, overpotentials, power densities in the cells with various current collectors, and the electrode materials total conductivity and thermal expansion are compared. The electrode compositions appraised in single-chamber and micro-SOFCs, hydrocarbon- and carbon-fueled cells, high-temperature electrolyzers, and other solid-electrolyte appliances are briefly covered in light of their similarity to the common SOFC materials discussed in the previous parts. [ABSTRACT FROM AUTHOR]

We report on the crystal structures of two hydrates of benzenehexasulfonic acid, its water sorption isotherm, temperature- and humidity-dependent conductivity, along with H NMR studies. At comparable humidities and temperatures, this crystalline material shows conductivity similar to Nafion, which conducts protons via liquid water channels. We believe that the presented discovery of fast protonic conductivity in benzenehexasulfonic acid at low humidities is encouraging for further efforts in developing highly sulfonated polymers as membranes for fuel cells. [ABSTRACT FROM AUTHOR]

A simulation method based on the integral equation for the sticking probability of ion in well was discussed for its application to study energy distributions of protons carried in simple and complex perovskite-like structures. In the terms of the Wiener—Hopf computational technique, a numerical algorithm was developed to detect deviations of the energy distribution function from the Boltzmann distribution near the potential barrier peak due to random interaction of ion with the nearest environment. Being considered as non-equilibrium in this sense, the derived distributions essentially deviated from the equilibrium distribution for a wide energy loss range of protons carried from one lattice position to another. The developed simulation algorithm may be of methodological interest in general practice for numerical solution of the Wiener—Hopf equations, because the known solution techniques for integral equations of this type are inapplicable to the studied problems of electrochemical kinetics due to their essentially different boundary conditions. [ABSTRACT FROM AUTHOR]

Electrical, thermal and mechanical studies were carried out on proton conducting electrolytes, based on poly(vinylpyrrolidone) (PVP) with ammonium perchlorate (NH4ClO4). Considering both the conductivity and manageability of films, the optimal PVP and NH4ClO4 weight ratio was 7:3 with 15 wt% water, exhibiting a protonic conductivity of 0.91×10−44 Scm−1 at 30°C and 1.12×10−2 Scm−1 at 80°C. Thermal studies showed that the crystallites of excess NH4ClO4 were formed inside the electrolyte, but they were decreased significantly with increasing water content. Cellulose was mixed to improve the mechanical strength of the hydrated samples. In a reinforced matrix of PVP/Cellulose complexes, the water retention property was improved significantly, thus exhibiting a slower decrease in conductivity over time. [ABSTRACT FROM AUTHOR]

The ternary system SiO2-P2O5-ZrO2 electrolyte and phosphotungstic acid (PWA) doped SiO2-P2O5-ZrO2 electrolyte were prepared for intermediate temperature fuel cell by using sol-gel technique. These silica-based proton conductors were confirmed to be non-crystalline structure without phase separation and good thermal stability by XRD and TG/DTA analysis. The doped PWA was found to be stabilized within the silica matrix and to enhance the proton conductivity. The proton conductivities of SiO2-P2O5-ZrO2 and SiO2-P2O5-ZrO2-PWA electrolytes showed 3.3×10−5 and 1.8×10−3 S/cm at 90 °C, respectively, and the cell performance of SiO2-P2O5-ZrO2-PWA electrolyte was obtained as 0.02–0.25 mA/cm2 at 300 °C under humid condition. [ABSTRACT FROM AUTHOR]

Urea combustion method was adopted to prepare precursor powder, MCeO3 doped with Zr (M is alkaline earth element, such as barium, strontium, and calcium). The precursor powder has typically perovskite structure after being calcined at 873 K. In 773 K∼1,273 K, BaCe0.425Zr0.475Y0.1O3 has the highest conductivity above 10−2 S cm−1 and good chemical stability, while the phase transition may exist in H2S atmosphere for the proton conductors. In the single fuel cell composed of MoS2-BaCe0.425Zr0.475Y0.1O3-σ-Ag with BaCe0.425Zr0.475Y0.1O3-σ as electrolyte, the best performance is obtained. The open circuit voltage of fuel cell is all about 0.72 V, the max power density, 1.55 mW cm−2. The performance drop is attributed to ohmic loss resulting from the separation of electrolyte and electrode, and improvement is required to bring out new anode materials compatible to the proton conductor, BaCe0.425Zr0.475Y0.1O3-σ, as electrolyte. [ABSTRACT FROM AUTHOR]

Heterogeneous composite BaZr0.1Y0.9O2.95/Na2SO4 was designed and fabricated with Y-doped BaZrO3 as matrix and Na2SO4 as dispersant by conventional powder processing to improve the total conductivity of barium zirconate. The electrical conduction of the composite was studied by electrical and electrochemical methods. Microstructure of the heterogeneous composite was examined by SEM. The experimewtal results show that the protonic conductivity of Y-doped BaZrO3 is greatly improved upon incorporating Na2SO4 in the material. Microstructure observation indicates that a multiphase structure with Na2SO4 disperses at the grain boundaries of BaZr0.1Y0.9O2.95. Electromotive force (EMF) measurements under fuel cell conditions reveal that the total ionic transport number of the composite is more than 0.9 at 750 °C. [ABSTRACT FROM AUTHOR]

Thermally stable and water-free proton conductor based on Brønsted acidic ionic liquid and silicate network was prepared by sol-gel processing. As a Brønsted acidic ionic liquid, mixture of bis(trifluoromethyl sulfonyl)imide (HTf2N) and 1-(1-ethyl-3-imidazolio)butane-4-sulfonate (eim4S) was employed. The sol-gel process was successfully done, since the ionic liquid worked as acidic catalyst for the dehydration and the condensation reactions of tetramethoxysilane. Although the gel containing equimolar eim4S and HTf2N showed high ionic conductivity, the thermal stability was poor because of sublimation of the HTf2N. Use of a small excess amount of eim4S effectively suppressed the sublimation of HTf2N. The obtained glassy ionogel showed high degradation temperature reflecting the thermal stability of both the silicate and the ionic liquid. The ionic conductivity reached to 10-3 S cm-1 at 150°C without any humidification. Contribution of protons to the ionic conductivity was confirmed by chronoamperometry and impedance spectroscopy under hydrogen atmosphere. [ABSTRACT FROM AUTHOR]

The reaction of NH3 decomposition was studied on Ag in a proton conducting double chamber cell-reactor. The proton conductor was a strontia-ceria-ytterbia (SCY) perovskite of the form SrCe0.95Yb0.05O3−α. The reaction was studied at 350–700 °C and atmospheric total pressure. The proton transference number (PTN) was calculated by simultaneous measurement of the imposed current and the proton flux and it was found to vary between 0.5 and 0.7. The effects of imposed current, temperature and inlet gas composition on the reaction rate and the PTN, were examined. Although the faradaic efficiency (Λ) remained near unity in all experiments, reaction rate enhancements (ρ) as high as 57 were achieved. An up to 90% decrease in the activation energy of the reaction was observed when protons were electrochemically “pumped” away from the catalyst. [ABSTRACT FROM AUTHOR]

SrZr1− x Y x O3 coatings were co-sputtered from metallic Zr–Y (84–16 at.%) and Sr targets in the presence of a reactive argon–oxygen gas mixture. The structural and chemical features of the film have been assessed by X-ray diffraction and scanning electron microscopy. The electrical properties have been investigated for different substrates by Complex Impedance Spectroscopy as a function of crystalline state, temperature and atmosphere. The as-deposited coatings are amorphous and crystallise after annealing at 673 K for 2 h under air. The stabilisation of the perovskite structure is a function of the nominal composition. The films are dense and present a good adhesion on different substrates. Crystallisation and mechanical stresses are detected by alternating current (AC) impedance spectroscopy. Significant ionic conductivity in the 473–823 K temperature range is evidenced in air. Two different conduction regimes in the presence of steam are attributed to a modification of the charge carrier nature. In spite of low conductivity values ( σ ~10−6 S.cm−1 at 881 K), the activation energies are in agreement with that of Y-doped strontium zirconate ceramics (~0.7 eV in air). [ABSTRACT FROM AUTHOR]

The solid-state proton conductor, P2O5.5H2O, is found very difficult to handle due to presence of a very high content of moisture and corrosive nature. The addition of Al2O3 and SiO2 into P2O5.5H2O, forming composite electrolytes, obviates said drawback. The Zn + ZnSO4 used as an anode to prepare cells with different cathode viz. I2, MnO2, PbO2, and V6O13 characterized under different conditions. Open circuit voltage, discharge current and discharge time, on load voltage, discharge capacity, power density, and energy density are evaluated from discharge properties. Protonically conducting composite 70(P2O5.5H2O)/30[(92SiO2)/08(Al2O3)] is found to be the optimum combination with the optimized 50Zn/50ZnSO4 as anode and 40MnO2/60 graphite as cathode from secondary battery view point. [ABSTRACT FROM AUTHOR]

With a view to developing a new proton conducting solid electrolyte usable at more elevated temperatures, the proton conduction in α-alumina was examined by reviewing the historical literatures and our recent works. It was clarified that acceptor-doped α-alumina had the possibility to exhibit a certain amount of proton conduction when hydrogen or water vapor was contained in the surrounding. In the case of Mg-doped α-alumina, proton conduction was found to dominate in the considerably wide range of oxygen and hydrogen potentials at temperatures 1273–1673 K. The excellent performance of the hydrogen sensor for molten metals employing Mg-doped α-alumina was experimentally ascertained. [ABSTRACT FROM AUTHOR]