Proton-conducting Solid Electrolyte Research Articles

Bridging the Gap between fundamentals and efficient devices: Advances in proton-conducting oxides for low-temperature solid oxide fuel cells

Low-temperature solid oxide fuel cells (LT-SOFCs) represent a cutting-edge solution in the domain of clean energy, poised to revolutionize electricity generation for both stationary and mobile applications. At the core of LT-SOFCs lies the proton-conducting solid oxide electrolyte, a subject of extensive exploration and advancement. This comprehensive review investigates the evolution of proton-conducting solid oxide electrolytes for LT-SOFCs, exploring the landscape from fundamental materials to diverse device architectures. The review meticulously examines three pivotal dimensions: 1) strategies for fine-tuning the properties and structures of ceramics and proton-conducting oxides, 2) advancements in techniques for protonic-conducting fuel cells (PCFCs), and 3) an exploration of the opportunities and challenges intrinsic to the progression of electrolyte-based PCFCs. By elucidating the advancements made in optimizing conductivity, chemical stability, sinterability, and electron-blocking characteristics of proton-conducting electrolytes, this review offers invaluable insights into the state-of-the-art for LT-SOFC technology. Furthermore, it casts a forward-looking perspective, envisioning the future trajectory of proton-conducting electrolyte research and its potential to reshape the landscape of LT-SOFC technology. By providing a comprehensive overview of past achievements and future prospects, this review serves as a valuable resource for researchers, engineers, and stakeholders, guiding them towards the realization of efficient and sustainable energy solutions.

Bilayer Cell Model and System Design of Highly Efficient Protonic Ceramic Fuel Cells

Protonic ceramic fuel cells (PCFCs) are promising devices for highly efficient next-generation fuel cell systems. PCFCs provide several benefits. Water formation at the cathode can improve fuel utilization. Also, lowering operation temperature using proton-conducting solid electrolyte membranes will enable a long lifetime and low system costs. On the other hand, ionic and electronic transport properties, i.e., proton, oxide ion, hole, and electron conductions, in PCFCs induce leakage current in electrolyte membranes and decrease energy conversion efficiency. Therefore, controlling the transport properties and designing cell structures to prevent them are important issues for developing highly efficient PCFCs. In this study, a comprehensive design approach was conducted from a bilayer cell to a PCFC system.It has been reported that bilayer electrolytes can improve the interface between cathode and electrolyte and also prevent nickel diffusion (1). Additionally, it has been reported that bilayer electrolytes can suppress leakage current by using a hole blocking layer (2, 3). Therefore, the use of bilayer electrolytes can help improve the efficiency and performance of PCFCs. In this study, a bilayer PCFC consisting of BaZr0.8Y0.2O3−δ (BZY) and BaZr0.1Ce0.7Y0.1Yb0.1O3−δ (BZCYYb) was modeled by considering the transport properties of each electrolyte. The main objective of the modeling was to determine the best cell design and operating conditions that maximize PCFC efficiency. Calculations were done by solving the set of integral equations described by Choudhury and Patterson (4) but extended for bilayer electrolytes (3) to obtain the cell potential, and the total and proton current densities.It was found that higher efficiencies were obtained when using a thin layer of BZY with a thicker layer of BZCYYb. The calculations suggest that the thin BZY layer acts as an electron-blocking layer. For example, leakage currents of less than 5% can be achieved by using a BZY(1 µm)|BZCYYb (19 µm). It was also found that the PCFC efficiency increased with decreasing temperature. Thus, higher efficiencies were obtained at 500°C than at 600°C.In addition, the energy conversion efficiency of a 5kW(DC)-class PCFC system was evaluated. In this study, the fuel in an anode was assumed to be hydrogen obtained by steam reforming of methane. Gas compositions in the streams of the PCFC system were calculated based on thermodynamic equilibrium at atmospheric pressure. The operating temperature of PCFC module was set as 500°C-600°C, and the external current density was assumed to be 300 mA/cm2. Here, the leakage current ratio was defined as a percentage of the leakage current to the total ion current density. The system efficiency was defined as an extracted power of the PCFC to the combustion heat of methane (25°C, LHV).The results are described as a standard case of 600°C as follows. A system efficiency of 69.5％ (LHV, DC) was attainable, assuming the cell voltage of 0.85 V, leakage current ratio of 1%, and fuel utilization of 94.2％. In this case, the steam-to-carbon ratio (S/C) was 2.5. In addition, a system efficiency of over 70％ (LHV, DC) was obtained under the cell voltage of 0.9 V, leakage current ratio of less than 5%, and fuel utilization of over 90％. Based on the above results, a cell design with bilayer electrolyte was discussed considering electrode/electrolyte materials and physical properties (e.g., transport number and conductivity). Acknowledgments This work was supported by a project, (JPNP20003), commissioned by the New Energy and Industrial Technology Development Organization (NEDO) and JSPS KAKENHI JP21H04938 and JP21J14251.

Особенности протонного транспорта в допированных перовскитах BaLa0.9M0.1InO4 (M = Nd, Gd, Pr) и BaLaIn0.9M0.1O4 (M = Sc, Y) на основе индата бария-лантана

The paper discusses the features of proton transport in isovalently doped layered perovskites based on barium-lanthanum indate BaLaInO4. The effect of the nature and concentration of the dopant on the unit cell size, water absorption, and proton conductivity was estimated. It is shown that the doping of the cationic sublattices of the layered perovskite BaLaInO4 with Nd3+, Gd3+, Pr3+, In3+, Y3+ ions makes it possible to increase the proton conductivity up to ~ 2 orders of magnitude, and the complex oxides obtained by this method are promising from the point of view of their further study as a material for a proton-conducting solid oxide electrolyte fuel cell.

In situ manipulation of perpendicular magnetic anisotropy in half-metallic NiCo2O4 thin film by proton insertion

Herein we report the manipulation of perpendicular magnetic anisotropy (PMA), a very important technique for spintronics devices, which is achieved in an all-solid-state redox (reduction/oxidation) device. The device consisted of NiCo2O4 (NCO) thin film with a c-axis orientation and a proton-conducting polymer (Nafion). The PMA of NCO can be manipulated in situ with low voltage (V ≤ 0.7 V) due to the utilization of a proton-conducting solid electrolyte. The magnetic anisotropy variation was quantitatively evaluated by an anomalous Hall measurement. The magnetic anisotropy field of the NCO thin film was successfully manipulated in the range of 5%, although the rotation of the easy axis of magnetization was not observed. This modulation is attributed to the strain and electronic configuration variation by proton insertion. This manipulation method for PMA with the solid electrolyte enables a variety of reservoir states and contributes to lower power consumption and high-precision machine learning.

Electrochemical control and protonation of the strontium iron oxide SrFeOy by using proton-conducting electrolyte

To electrochemically control structural and transport properties of oxygen-deficient perovskite SrFeOy (2.5 ≦ y ≦ 3) (SFO) epitaxial films, we employed electric-field-effect transistor structures in which the proton-conducting solid electrolyte Nafion is used as a gate insulator. When a positive gate voltage (VGS) is applied and protons are injected toward the film channel layer, the SFO films are electrochemically reduced, leading to increases in the channel resistance. On the other hand, when a negative VGS is applied and protons are removed, the SFO films are oxidized, and as a result, the channel resistances decrease. In addition, we found that the electrochemically reduced SFO films accommodate protons, forming the proton-containing oxide HxSrFeO2.5 whose proton concentration is determined by elastic recoil detection analysis to be x ∼ 0.11. Our results indicate the usefulness of the proton-conducting solid electrolyte for electrochemically controlling transition metal oxides and for exploring proton-containing oxides.

Layered and hexagonal perovskites as novel classes of proton-conducting solid electrolytes. A focus review

Solid oxide electrolytes have attracted significant attention due to their possible applications in energy conversion devices, including solid oxide fuel cells (SOFCs) and electrolysis cells (SOECs). Although a large amount of data has been accumulated to date, the design of new representatives of ionic electrolytes is of unquenchable interest. In this paper, a review of the new classes of proton-conducting solid electrolytes is provided. The physicochemical and transport properties of layered perovskites (BaNdInO4, BaNdScO4, SrLaInO4, BaLaInO4) and hexagonal perovskites (Ba7Nb4MoO20, Ba5Er2Al2ZrO13 and Ba5In2Al2ZrO13) were analyzed and summarized. Based on the performed analysis, the most promising compositions among the considered phases were identified and the effective approaches aimed at improving their functional characteristics were provided.

Hourglass-Type Polyoxometalate-Based Crystalline Material as an Efficient Proton-Conducting Solid Electrolyte.

Proton exchange membrane fuel cells are limited because they are limited to working temperatures and are susceptible to damage by dramatic electrochemical environments such as hydrogen peroxide/radicals. It is necessary to develop new proton-conducting materials that are water-stable and can operate at high temperatures. The hourglass reduced molybdophosphate-based compound (H2bimb)3[Zn3(H6P4Mo6O31)2] (bimb = 1,4-bis[(1H-imidazol-1-yl)methyl]benzene) was designed and synthesized under solvothermal conditions. Single-crystal X-ray diffraction analyses demonstrated noticeably that CUST-571 was composed of an hourglass {Zn[P4Mo6]2} structure, which consisted of two fully reduced half-units {P4Mo6}. It was found that CUST-571 possessed an excellent proton conductivity of 4.54 × 10-3 S cm-1 at 85 °C and 98% RH (relative humidity). In addition, CUST-571 is capable of an excellent catalytic decomposition of H2O2, which is beneficial to increase the life of fuel cells. On the basis of the aforementioned results, CUST-571 may be a promising proton-conducting polyoxometalate hybrid material in the future.

On-site H2O2 electro-generation process combined with ultraviolet: A promising approach for odorous compounds purification in drinking water system

The on-site generation of hydrogen peroxide (H2O2) attracts much attention for advanced oxidation processes (AOPs) in water treatment. In this work, we reported a novel on-site H2O2 generation reactor combined with ultraviolet (UV) for taste and odor (T&O) compounds removal in drinking water purification systems. The reactor is equipped with a gas diffusion electrode (GDE) accompanied by a proton-conducting solid electrolyte. In this reactor, GDE is used to improve the oxygen transfer efficiency. The porous solid electrolyte is selected for the proton and electron conduction instead of an electrolyte solution, which is crucial for producing pure H2O2 solution. The production rate and concentration of H2O2 can be controlled through adjusting the applied current efficiency and the flow rate of deionized water in a solid chamber. Meanwhile, this system exhibits long-term stability during a continuous operation for 96 h. For the application of the system, the single-cell was assembled into cell stacks, which improved the H2O2 concentration from 780.9 to 2301.3 mg·L−1, along with the energy consumption reduced from 23.81 to 6.67 kWh·kg−1 under the applied current density of 30 mA·cm−2. To evaluate the water purification performance of this system, the oxidation degradation of 2,4,6-trichloroanisoles (TCA) was conducted using the on-site H2O2 generation process under both static and dynamic flow conditions combined with UV light. The degradation rate of TCA was >95% with its initial concentration of 1 μg·L−1 under the hydraulic retention time from 10 to 40 min−1 and H2O2 dosage from 10 to 100 mg·L−1. Meanwhile, almost no residual H2O2 was detected after the degradation process. This study proposed a promising device for drinking water purification.

Design and Modeling of Proton-Conducting Bilayer Electrolytes Using a Nernst-Planck-Poisson Formulation

Proton-conducting oxides have attracted much attention in recent years due to their good ion conductivity at intermediate temperatures (500-700°C), as opposed to conventional oxide ion-conducting oxides that require high temperatures (usually, >900°C). Lowering the operating temperature of reversible protonic ceramic electrochemical cells (RePCECs) is desirable as it reduces material, heating, and insulation costs, while also increasing the operating life of the cell. Nevertheless, along with the desired proton conductivity, typical proton-conducting solid electrolytes also allow the transport of other charged defects like oxygen-vacancies, electrons, and electron holes. The presence of these other defects, especially the electron holes, causes leakage current that significantly reduces the cell’s electrical efficiency. Therefore, an electrolyte capable of reducing leakage current is necessary. Unfortunately, there is usually a trade-off between high ionic conductivity and low hole conduction. For example, while lanthanum tungstate (LWO) has a low electron conductivity and is capable of suppressing hole conduction below 800°C, its proton conductivity is lower than that of commonly used perovskite materials like yttria-doped barium cerate (BCY) or yttria-doped barium zirconate (BZY). Nonetheless, previous studies showed that LWO67 can act as a leakage current-blocking layer when deposited on a BZY82 base electrolyte and the estimated leakage current was almost 200 times lower than that of a BZY82 single layer electrolyte under open-circuit conditions. This suggests that under certain operating conditions, bilayer electrolytes can achieve better performance when compared to their corresponding single-layer electrolytes. Therefore, in this study, we design proton-conducting bilayer electrolytes by investigating the incorporation and transport of charged defects using a steady-state Nernst-Planck-Poisson (NPP) model.The main goals of this work are twofold. Firstly, to find the combination of electrolytes that better suppresses leakage current. For this purpose, we calculate the defect concentration, flux, and electrostatic profiles inside common materials like BCY, BZY, BZCYYb, BZCY, LWO, and different combinations of bilayer electrolytes to better understand how the addition of a leakage current-blocking layer affects proton conduction and overall efficiency. We consider three mobile defects when solving the NPP equation, protons (OHO •), oxygen vacancies (vO ••), and electron holes that are treated as small polarons localized at oxygen sites (OO •). Afterward, the I-V curve and relevant theoretical efficiency are predicted within and A cm-2 (fuel cell and electrolyzer operation) at 500, 600 and 700°C, in order to identify the most promising one. Secondly, to design a cell by finding the optimal thickness of the better performing bilayer electrolyte that maximizes efficiency.

Synthesis and Research Using Computer Simulation of Proton-Conducting Solid Electrolytes Based on Hafnate and Barium Zirconate

Synthesis and Research Using Computer Simulation of Proton-Conducting Solid Electrolytes Based on Hafnate and Barium Zirconate

Design and Performance of a Proton-Conducting Solid Oxide Reversible Cell

Introduction Renewable and clean energies have attracted much interest in recent years due to environmental and economic concerns related to the use of fossil fuels. For this reason, solar and wind energies have become popular alternatives and are widely used in many countries as reliable energy sources. However, these technologies are intermittent by nature which makes it challenging to successfully integrate them into power grids. Reversible electrochemical cells provide an attractive way to store solar and wind energy surplus by operating as an electrolysis cell to produce hydrogen that can be later used to generate electricity by operating as a fuel cell.Reversible cells using proton conductive solid oxide electrolytes have some advantages over other technologies, for instance, they show higher ionic conductivity in the intermediate temperature range which lowers the need for heating. Nonetheless, previous studies show low faradaic efficiencies (FEs) that are usually between 20 and 70%, which means that less than 70% of the applied current is used to produce hydrogen. A state-of-the-art reversible cell by Choi et al [1]. in 2019 yielded a remarkable current density of -1.8 A cm-2 at 600°C and 1.3 V, but the reported faradaic efficiencies ranged from 40 to 75%. In a recent study BCZYYb+1.0wt% NiO electrolyte was used to obtain one of the highest reported faradaic efficiencies to date, between 90-98%. According to the authors, “low faradaic efficiencies can be almost entirely attributed to higher current leakage” [2]. Therefore, an electrolyte capable of considerably reducing leakage current is necessary. Lanthanum tungstate (LWO) is a promising electrolyte material since it has a good ionic conductivity, low electron conductivity and it is capable of suppressing hole conduction below 800°C [3]. In this study, we assess the performance of a solid oxide reversible cell using LWO and other common electrolyte materials like BCY10, BZY20 and BZCYYb1711. Methods The performances for LWO67 and other commonly used electrolyte materials were predicted based on their transport properties using Choudhury’s model [4] with the required conductivity parameters obtained by fitting to reported experimental data (Table 1). Power efficiencies (PEs) were computed for fuel cell operation and faradaic efficiencies for electrolysis cell operation. Additionally, the performances of LWO67/BCY10 electrolyte-supported-platinum (Pt)-symmetric cells were also evaluated using a fuel cell testing unit with an in-line gas chromatograph (GC) to measure the produced hydrogen. A potentiostat/galvanostat was used to measure the characteristic I-V curves and electrochemical impedance. Both the predictions and experiments were performed with a gas composition of 20% O2 in Ar (3% H2O) for the air electrode side and 1% H2 in Ar (3% H2O) for the hydrogen side. Pt was chosen as both the fuel and air electrode to be able to easily compare the efficiencies of LWO67 and BCY10 under the exact same conditions. This is because LWO can react with other electrodes and a thin protective layer would be necessary to prevent this from happening. Results and discussion According to the predictions, LWO67 exhibits the highest PE in fuel cell operation at typical operating conditions of current p-SOFC systems (Fig. 1). In the same way, LWO67 shows the highest faradaic efficiency in electrolysis operation (Fig. 2) exceeding that of BZCYYb by more than 10%. These results are due to LWO67’s low electron and hole conductivities and they suggest that it has great potential as an electrolyte for reversible cells. It was also found that the optimum electrolyte thickness is around 10 µm and lower values produce a decrease in the FE. This occurs because as ionic conductivity increases with decreasing thickness, so does the leakage current. Therefore, there is a trade-off relationship between the electrolyte thickness, the current density, and the efficiency. Moreover, the FEs measured experimentally were higher for LWO67. For example, at 650°C the FE was 26% for BCY10 while it was 37% for LWO67. Nevertheless, this difference is expected to be even higher in anode-supported cells with thinner electrolytes, indicating that LWO67 has potential as an electrolyte material. Additionally, it has been shown that poor electrode performance can affect the FE. Thus, a more active electrode should improve the performance.

Hydrogen Production by Steam Electrolysis in Solid Acid Electrolysis Cells.

Hydrogen production by steam electrolysis at intermediate temperatures has potential for both the high energy conversion efficiency and the flexible operability suitable for the utilization of renewable energy resources. Employment of proton-conducting solid acid electrolytes at around 200 °C is considered promising but has rarely been investigated. Here, steam electrolysis was performed at 160-220 °C using a solid acid electrolysis cell (SAEC) composed of a CsH2 PO4 /SiP2 O7 composite electrolyte and Pt/C electrodes. Hydrogen production was successfully demonstrated with Faraday efficiencies around 80 %. Key factors affecting the SAEC stability were investigated in detail for the first time. It was revealed that a certain part of the electrolyte migrated into the porous anode structure during the operation. The migrated electrolyte prevented the gas diffusion and flooded the Pt/C catalyst layer. It was also found that carbonaceous materials in the anode was oxidized, leading to the decrease in the number of electrochemically active sites. Based on the findings, Pt mesh was employed as an alternative anode. The SAEC with the Pt mesh anode showed superior stability, demonstrating the importance of the anode design. The present work provides a comprehensive view of the stability issues, which is essential for the development of durable and practical SAECs.

Effect of High Ammonium Salt Concentration and Temperature on the Structure, Morphology, and Ionic Conductivity of Proton-Conductor Solid Polymer Electrolytes Based PVA.

Polyvinyl alcohol (PVA) based proton-conducting solid polymer electrolyte was prepared with a high salt concentration of ammonium nitrate (NH4NO3) by the technique of solvent casting. From the X-ray diffraction studies, the semicrystalline nature of PVA with the inclusion of NH4NO3 was studied. XRD analysis indicates that the highest ion conductive sample exhibits the minimum crystalline nature. The decreasing trend of Jonscher-exponent with temperature rise reveals that the present system is insured by the correlated barrier hopping (CBH) model. The maximum room temperature conductivity was found to be 5.17 × 10−5 S/cm for PVA loaded 30 wt.% of NH4NO3. The ionic transport of the proton-conducting solid polymer electrolyte was studied at the temperature range of 303–353 K. The conductivity-temperature relationship of the systems was analyzed using both the Arrhenius and Vogel–Tammann–Fulcher (VTF) models to explain the ionic hopping mechanism for the system.

Constructing p-sulfonatothiacalix[4]arene-based coordination squares as new type of efficient proton-conducting solid electrolytes

To develop high-conductivity solid-state proton-conducting materials is a hot topic in the fuel-cell technology. Herein, p-sulfonatothiacalix[4]arene was chosen as the terminal ligand to construct porous coordination compounds, {[Co4Cl(H2TC4AS)]4(BDC)8}12- (CIAC-240) and {[Co4Cl(H4TC4AS)]4(SIP)8}12- (CIAC-241) (Na4H4TC4AS = tetrasodium p-sulfonatothiacalix[4]arene; H2BDC = isophthalic acid; NaH2SIP = 5-sulfoisophthalic acid sodium salt). Both structures are featured with some window frame-like squares which are constructed by bridging the shuttlecock-like Co4-TC4AS secondary building units (SBUs) with the BDC/SIP ligands and further stacked into the supramolecular extended structures. The proton conduction and vapor adsorption of the compounds were discussed and compared. The experimental results gave the maximum values of 3.22 mS cm−1 and 11.6 mS cm−1 for the proton conductivity of CIAC-240 and CIAC-241, respectively.

(Invited) Electrosynthesis in Proton Conducting Solid Electrolytes a) CO2/H2o Co-Electrolysis and b) NH3 Synthesis

In addition to their applications in the construction of fuel cells, hydrogen separators and sensors, solid state proton (H+) conductors can be used as the main component of catalytic and electrocatalytic reactors. Their advantage, compared to low-temperature proton conductors, is that they can operate in a temperature range within which the kinetics of several industrially important catalytic hydro- and dehydrogenation are acceptably fast. In most of the applications of H+ cell reactors in catalytic research, the reaction of interest takes place on the working electrode while the counter electrode serves for the formation of protons from a hydrogen containing compound. These reactors, however, would become more competitive if useful chemicals were produced on both, working and counter electrode [1, 2].Results on two reaction systems in which both, cathode and anode were properly utilized are presented here. The aim of this study is the electrochemical production of methanol from carbon dioxide and steam, in a co-ionic conducting solid electrolyte cell at atmospheric pressure. Steam and CO2 are introduced at the anode and cathode side, respectively, of a co-ionic (H+ and O2-) conductor. Steam is electrolyzed to form O2 and protons (H+). The latter are transferred to the cathode and react with CO2 to form CH3OH. The second system is an electrochemical Haber-Bosch (H-B) Process [3, 4]. A mixture of steam and methane is fed over the anode (a Ni-composite electrode) and gaseous N2 is fed over the cathode (VN-Fe). Hydrogen extraction from the steam reforming compartment, enhances the thermodynamically limited methane conversions, whereas 5-14% of the protons pumped are converted to ammonia. A protonic ceramic fuel cell is used to recover electricity and separate nitrogen from ambient air by exploiting by-product hydrogen. This process could potentially require less energy and release fewer CO2 emissions than its conventional counterpart.

Suppression of Leakage Current in Proton-Conducting BaZr0.8Y0.2O3−δ Electrolyte by Forming Hole-Blocking Layer

Solid oxide fuel cells (SOFCs) with proton-conducting solid electrolyte, instead of the oxide-ion conducting solid electrolyte have attracted attentions because of their high potential to reduce operating temperatures and to enhance the electrical efficiencies of SOFCs. In addition, the proton-conducting SOFCs with multistage electrochemical oxidation configuration will be promising technology for critically-high electric efficiencies. However, it is known that there are non-negligible charge -carriers other than protons in typical proton-conducting solid oxide electrolytes at relatively high temperatures. The existence of the partial conductivities of holes and/or electrons will cause the internal leakage current that consumes fuel but never generates any electrical power output. The higher ratio of the leakage current to external current will more deteriorate the electrical efficiency. In this study, the effects of blocking -layers formed on the air side surface of base electrolyte layer consisting of BaZr0.8Y0.2O3−δ (BZY82) for suppressing the leakage current have been investigated by using electrochemical parameters of the partial conduction of the materials. The chemical potential profile and leakage current showed large dependence on the material of the blocking-layer. Lanthanum tungstate was found to play a role as unique and strong blocking-layer against the leakage current.

Microstructural, dielectric, and transport properties of proton-conducting solid polymer electrolyte for battery applications

Poly (vinyl alcohol) (PVA) complexed with ammonium chloride (NH4Cl) solid polymer electrolyte films was prepared using solution casting technique. Complexation of dopant with polymer was studied using Fourier transform infrared spectroscopy (FTIR). X-ray diffraction (XRD) results reflect that degree of crystallinity of the polymer increases with doping level. Surface morphology and topology of the electrolyte were studied using Scanning electron microscopy (SEM) and atomic force microscopy (AFM). Thermogravimetric analysis (TGA) results accounts for the increase of thermal stability of PVA due to the incorporation of NH4Cl. Impedance analysis was carried out to understand relaxation phenomena of polymer electrolyte. Dielectric studies revealed that the mobility of charge carriers follows non-Debye nature of ionic relaxation. Electrical studies reveal that proton conduction occurs in this polymer electrolyte through Grotthus mechanism and maximum conductivity of the polymer electrolyte (7.5 wt% NH4Cl/PVA) has been observed to be 1.81 × 10−3 S/cm at 353 K. Transport parameters have been determined using Wagner’s polarization technique. The observed highest conductivity of polymer electrolyte indicates utilizing this electrolyte for the fabrication of proton battery applications, and accordingly, the cell parameters have been measured.

Leakage Current and Chemical Potential Profile in Proton-Conducting Bi-Layered Solid Oxide Electrolyte with BZY and Hole-Blocking Layers

Solid oxide fuel cells (SOFCs) with proton-conducting solid electrolyte, instead of the oxide-ion conducting solid electrolyte have attracted attentions because of their high potential to reduce operating temperatures and to enhance the electrical efficiencies of SOFCs. In addition, the proton-conducting SOFCs with multistage electrochemical oxidation configuration will be promising technology for critically-high electric efficiencies. However, it is known that there are non-negligible charge -carriers other than protons in typical proton-conducting solid oxide electrolytes at relatively high temperatures. The existence of the partial conductivities of holes and/or electrons will cause the internal leakage current that consumes fuel but never generates any electrical power output. The higher ratio of the leakage current to external current will more deteriorate the electrical efficiency. In this study, the effects of blocking -layers formed on the air side surface of base electrolyte layer consisting of BaZr0.8Y0.2O3-δ (BZY82) for suppressing the leakage current have been investigated by using electrochemical parameters of the partial conduction of the materials. The chemical potential profile and leakage current showed large dependence on the material of the blocking -layer. Lanthanum tungstate was found to play a role as unique and strong blocking -layer against the leakage current.

Synthesis of BaCe0.9-xZrxY0.1O3-δ nanopowders and the study of proton conductors fabricated on their basis by low-temperature spark plasma sintering

Using a citrate-nitrate process, BaCe0.9-xZrxY0.1O3-δ (x = 0, 0.5, 0.6, 0.7 and 0.8) nanopowders were synthesized, on the basis of which proton-conducting solid electrolytes (average size of coherent scattering region (CSR) - 15–53 nm) were obtained by spark plasma sintering (SPS) at a low temperature (900°С). The dependence of phase composition, microstructure and electrophysical properties of the obtained samples on ZrO2 content and consolidation conditions was established. It was found that the BaCe0.4Zr0,5Y0.1O3-δ solid solution had the highest electrical conductivity among zirconium-containing ceramic materials in the studied concentration range. It was shown that SPS is a promising method for obtaining solid electrolytes for proton-conducting solid oxide fuel cells (PCFC) at lower temperatures (by 400–500°С), compared to traditionally-used temperature conditions (1400–1800 °C).

Al2O3-incorporated proton-conducting solid polymer electrolytes for electrochemical devices: a proficient method to achieve high electrochemical performance

A new series of proton-conducting solid polymer electrolytes with different compositions, comprising polyvinylpyrrolidone (PVPK40) and polymethylmethacrylate (PMMA) as host polymers, methanesulfonic acid (MSA) as a proton-conducting salt, and alumina (Al2O3) as the nanofiller, were prepared using solution casting. High proton-conducting samples were identified and utilized for the construction of primary proton batteries. The electrical properties of the prepared electrolytes were investigated through AC impedance analysis. The highest proton conductivity (2.51 × 10−5 S/cm) was achieved at room temperature by PMMA-PVPK40-MSA-based blended polymer electrolytes (BS3). The discharge characteristics of filler-dispersed solid polymer electrolytes were better than those of other solid polymer electrolytes. The estimated energy density of the constructed proton battery using solid polymer electrolytes with blended polymers and nanofillers was 0.66 and 3.25 Wh kg−1, respectively.