BCY Electrolyte Research Articles

Ionic conductivity increase by one order of magnitude in BCY composite electrolyte added with Li2O

The low ionic conductivity of proton conductor electrolytes at low temperatures was one of the key issues that restrict the reduction of operating temperature in ceramic fuel cells. The traditional Y-doped BaCeO3 proton conductor (BCY) has an ionic conductivity of only a few tens of mS·cm−1 at 500 °C, which cannot meet the needs of high-performance low-temperature ceramic fuel cells. In this paper, we found that the ionic conductivity of the composite electrolyte made by adding 20 % Li2O to BCY at 550 °C was 0.526 S cm−1, which was 40 times that of the dense BCY electrolyte sintered at 1550 °C. The maximum power density of a ceramic fuel cell using a BCY- Li2O composite material with a thickness of 1 mm as the electrolyte and porous Ag as the symmetrical electrode was 129 mW cm−2 in H2 at 550 °C. The characterization results of XRD, EPR, and FTIR showed that there may be a region with a large number of oxygen vacancies and lithium vacancies created at the interface of the BCY and Li2O–LiOH composite electrolyte formed in the BCY-Li2O composite electrolyte during the testing conditions for fuel cell performance due to the migration of Li+. The formation of this region should be the main reason for the extremely high conductivity of the BCY-Li2O–LiOH composite electrolytes formed in the cell at low temperatures.

Effect of Li2CO3 and LiOH on the ionic conductivity of BaCe0.9Y0.1O3 electrolyte in SOFCs with a lithium compound electrode

The effects of Li2CO3 and LiOH on the ionic conductivity of BaCe0.9Y0.1O3(BCY)-x%Li2CO3 (x = 0, 5, 10 and 30) and BCY-y%LiOH (y = 0, 2, 5 and 8) composite electrolytes were investigated. Symmetrical cells with the structure of foam Ni–Ni0.8Co0.15Al0.05LiO2 (NCAL)∖BCY-x%Li2CO3 or y%LiOH∖foam Ni-NCAL and Pt∖BCY-x%Li2CO3 or y%LiOH∖Pt were prepared with NCAL-coated foam Ni and porous Pt as symmetrical electrodes, respectively. The ionic conductivity test results of the cells with Pt as the symmetrical electrode showed that the addition of LiOH did not improve the ionic conductivity of the BCY electrolyte, while the addition of Li2CO3 could significantly improve the ionic conductivity of the BCY electrolyte. The maximum power density of the cells with the structure of foam Ni-NCAL∖BCY-x%Li2CO3 or y%LiOH∖foam Ni-NCAL decreases with the increase in the amount of Li2CO3 or LiOH, which indicates that adding Li2CO3 or LiOH to BCY via mechanical mixing did not improve the electrochemical performance of the cells with NCAL as the electrode, and the NCAL electrode has the greatest impact on the performance of the cells. The interface of Li2CO3 and BCY should be a high-speed channel for ion conduction. Increasing the effective area of the interface between BCY and Li2CO3 and optimizing its continuity in the electrolyte should be the main development direction for improving the ionic conductivity.

Ionic conduction mechanism of a nanostructured BCY electrolyte for low-temperature SOFC

A solid oxide fuel cell with 1.2 mm thick nanocrystalline BCY (BaCe0.9Y0.1O3) electrolyte was prepared by the copressing method, and its electrochemical performance was tested in H2/air conditions. The maximum power density of the nanocrystalline electrolyte cell prepared with BCY powders calcined at 1000 °C and operated at 550 °C in H2 is 405.2 mW cm−2. The carriers of nanocrystalline BCY electrolyte were studied by using double-layer electrolyte cells with pure oxygen ion conductor GDC (Gd0.1Ce0.9O2) and proton conductor SCY (SrCe0.95Y0.05O3), sintered at high temperatures as proton and oxygen ion filters. It is found that nanocrystalline BCY is a mixed conductor of oxygen ions and protons. The results of hydrogen and oxygen concentration cells show that the transference number of oxygen ions in the nanocrystalline BCY prepared in this study is higher than that of protons. XPS and HRTEM results of BCY particles before and after performance testing showed that an amorphous layer containing a high concentration of oxygen vacancies and suspected carbonate was formed on the surface of BCY particles after fuel cell performance testing. We believe that the amorphous layer should be a high-speed ion conduction channel for nanocrystalline BCY electrolyte during performance testing.

Chemical stability and electrical and mechanical properties of BaZrxCe0.8-xY0.2O3 with CeO2 protection method

This study investigated the decline in the conductivity and mechanical strength after CO2 poisoning and found a new protective method for BaZrxCe0.8-xY0.2O3 proton-conducting electrolyte. The high temperature solid state reaction (SSR) was used in synthesizing electrolyte to naturally generate CeO2 on the surface. A comparison of the oxides in the conductivity decline test revealed that the sample with CeO2 on the surface substantially improved the stability of conductivity, reducing the decline ratio from 56% to 7% for BCY electrolyte and 50% to 7% for BCZY sample. Raman mapping results indicate the naturally generated CeO2 on electrolyte surface can considerably reduce impurity formation and maintain the microstructure of electrolyte. This work demonstrates that samples with CeO2 on the surface effectively protect the BaCeO3-based proton-conducting electrolyte from CO2 poisoning. This method may be applied to similar BaCeO3-based perovskite materials as a new protective method.

Measurement of Chemical Potential in Bcy Electrolyte with Varying Thickness and Configuration Using Embedded Reference Electrodes

The correlation between internal chemical potential, and durability of anode-supported BCY (yttria-doped barium cerate) electrolyte cells, was investigated as a function of electrolyte thickness and configuration. Internal hydrogen and oxygen chemical potentials were measured using embedded Pt probes. As the electrolyte thickness decreased, the internal chemical potential became dominated by the gases surrounding the cathode, indicating that the thin BCY cell may be vulnerable to water vapor produced at the cathode during operation. BCY cells with BZY (yttria-doped barium zirconate) protecting at the cathode side (bi-layer cells) showed a small chemical potential variation through the electrolyte region close to the electrode side, indicating significant electronic conduction.Constant-current tests were conducted on thin (~ 10 µm) and thick (~ 35 µm) BCY single layer cells, and also on BCY-BZY bi-layer cells, especially under negative voltage conditions. Consistent with the results of the internal chemical-potential measurements, the thin BCY single layer cell showed a significant rate of degradation due to changes in BCY composition in the electrolyte and cathode, while the thick BCY single layer cell showed much better durability, regardless of the sign of cell voltage. The bi-layer cell was stably operated under any severe operating conditions, because of the BZY protecting layer against water vapor’s attack and its significant electronic conduction close to the cathode/electrolyte interface. Thus, the present work shows the effect of BCY electrolyte thickness and configuration on the durability of BCY based cells, in terms of their internal chemical potential.

Reaction Analysis of Electrochemical Synthesis of Ammonia with Proton Conducting BaCe0.9Y0.1O3 Solid Electrolyte

Ammonia is one of candidates as an energy carrier for renewable energies because of its high energy density and easy liquefaction. In this study, we focused on electrochemical synthesis of ammonia using proton conducting solid electrolyte[1]. Ammonia is produced from nitrogen and water with a proton conductor as follows. N2 + 3H2O → 2NH3 + 3/2O2 (1) Water dissociates on an anode to form proton, and then ammonia forms on a cathode by reactions among proton, electron and nitrogen as follows. H2O → 1/2O2 + 2H+ + 2e- (2) N2 + 6H+ + 6e- → 2NH3 (3) Therefore, appropriate reaction among nitrogen, proton and electron at the triple-phase boundary in the cathode is important for the efficient electrochemical production of ammonia. So far, AgPd cathode has been mainly used because Pd can permeate hydrogen[2]. However, to accelerate the ammonia formation rate and to improve Faradaic efficiency for the ammonia formation, the control of cathode microstructure and the comprehension of electrochemical ammonia formation mechanism are required. In this study, Ru-doped La x Sr1-x TiO3 (LSTR) and Ru-doped BaCe1-x Y x O3 (BCYR) were used as cathodes. Ru nanoparticles was expected to be exsoluted from B-site in perovskite lattice in reduction atmosphere and to act as active sites for ammonia formtion[1]. Addiotionally, these perovskite materials have different protonic and electrical conductivities. LaxSr1-xTiO3 (LST) has high electrical conductivity such as 102-103 S cm-1[3]. On the other hand, although the electrical conductivity of BCYR is lower than that of LaxSr1-xTiO3, BCYR is a mixed protonic and electronic conductor[4]. To realize efficient electrochemical ammonia production, the role of the transport properties of these cathode materials was investigated. A kinetic analysis of electrochemical ammonia synthesis was also performed. Proton conducting solid electrolyte, BaCe0.9Y0.1O3 (BCY), was synthesized by the co-precipitation method. Ru-doped La0.3Sr0.6TiO3 and Ru-doped BaCe0.9Y0.1O3 were prepared by the solid state reaction method. BCY electrolyte, LSTR and BCYR cathodes were characterized by XRD, XPS, SEM, TEM and TG. Electrolyte-supported LSTR-BCY|BCY|Pt and BCYR|BCY|Pt cells were fabricated for the electrochemical synthesis of ammonia. The electrochemical synthesis was performed at 500℃ by supplying a gas mixture of 2.1%H2O/98%N2 to the cathode side and 2.1%H2O/10%Ar/88%Ar to the anode side. AC impedance measurements with a frequency range of 10-2-105 Hz and cyclic voltammetry with a sweep rate of 2 mV s-1were conducted. Synthesized ammonia was detected with an ion-exchange chromatograph. 0, 10, 20 and 40% Ru-doped La0.3Sr0.6TiO3 and BaCe0.9Y0.1O3 were synthesized. x% Ru-doped LST and BCY are described as LSTRx and BCYRx hereafter (e.g. 40% Ru doped LST is LSTR40). 40% Ru was successfully doped in LST. On the other hand, impurities such as RuO2were observed for BCYR, especially for BCYR20 and BCYR40. BCYR10 was used for the electrochemical ammonia production because the peak shifts to the higher angle was observed in XRD patterns by 10% Ru doping and peak intensities of the impurities were small in BCYR10. From the observation using TEM, Ru nanoparticles of 2-3 nm were observed on the surface of LSTR and BCYR particles, which were exsoluted from B-site in the perovskite lattice. The amount of the exsoluted Ru nanoparticles was highest in LSTR40. Exsolution of Ru nanoparticles on LSTR and BCYR was also confirmed using CO pulse adsorption measurement and XPS. Electrochemical measurements were conducted with LSTRx (x = 0, 20 and 40)-BCY|BCY|Pt cells and a BCYR10|BCY|Pt cell. Cyclic voltammetry measurements showed that current density was improved with an increase in the amount of Ru-doping. Formation of ammonia was detected for both the LSTR and BCYR cells. The maximum ammonia formation rate was 1.1×10-11 mol s-1 cm-2with the LSTR40 cathode at the applied voltage of -500 mV, as shown in Fig. 1. Although the ammonia formation rate with the mixed protonic and electronic conducting BCYR cathode was relatively low because of the low current density, Faradaic efficiency for the ammonia formation with the BCYR cathode was improved in comparison with the LSTR40 cathode. This result suggests that proton conduction in a cathode may be an important factor for the efficient electrochemical production of ammonia because proton can be effectively transported to active Ru nanoparticles. For further high ammonia formation rate, improvement of the electrical conductivity in mixed protonic and electronic conducting cathode is important. Acknowledments: This work was supported by CREST, JST. [1] J. Otomo et al., ECS Transaction, 68, 2663-2670 (2015). [2] I. Garagounis et al., Frontiers in Energy Research, 2, 1 (2014). [3] X. Zhou et al., RSC Advances, 4, 118 (2014). [4] H. Matsumoto et al., J. Electrochem. Soc., 152, A488 (2005). Figure 1

Internal Partial Pressure and Durability of Bcy Based Protonic Ceramic Fuel Cells As a Function of Electrolyte Thickness

Internal partial pressure in BCY based solid oxide fuel cells were measured as a function of electrolyte thickness. The measurements of internal ΔΦ were conducted on the thin (~ 10 µm) and thick (~ 50 µm) BCY electrolyte using an embedded Pt probe, and it was observed that ΔΦ depends on the electrolyte thickness. Using the values of internal ΔΦ, internal hydrogen and oxygen partial pressure were calculated, and it was found that the internal partial pressure changes with electrolyte thickness. Thin BCY cells are dominated by the near-cathode gases rather than the near-anode gases, indicating it is more vulnerable to water vapor produced at the cathode during fuel-cell operation. The correlation between internal partial pressure profile and performance durability were also investigated. CC tests were conducted on a thin (~ 10 µm) BCY-electrolyte cell with BCY + LSCF cathode, and on a thick (~ 35 µm) BCY electrolyte cell with BZY + LSCF cathode, at positive and negative cell voltage. The former showed a rapid rate of voltage drop under all operating conditions, while the latter showed much more stable performance, even when operating at a negative voltage. No changes in microstructure and composition were detected in the thick BCY electrolyte or the BZY + LSCF cathode. Thus, the present work shows the effect of the electrolyte thickness and cathode-material selection on the durability of BCY based cells, in terms of internal partial pressure.

Development of a Direct Ammonia Fueled Hydrogen Membrane Fuel Cell

Recently, ammonia has attracted a considerable interest as a prospective carbon-free fuel source for fuel cells due to the low cost, ease in liquefaction and transportation at ambient temperatures, and high volumetric energy density. As for SOFCs, some promising performance has been obtained with the use of ammonia. However, only the hydrogen generated from the thermal decomposition of ammonia serves as the fuel. As a result, the anode material is required to be active for the ammonia decomposition as well as the electro-oxidation of hydrogen. Hydrogen membrane fuel cell (HMFC), which was firstly proposed by Ito et al.,1 consists of an ultrathin proton conducting ceramic electrolyte supported on a dense hydrogen permeable metal anode. The cell facilitates efficient power generation, giving 900 mW cm-2 at 500°C,1 since reduced electrolyte thickness can significantly decreases the ohmic loss at lower temperatures. Hence, HMFC is attractive as a direct ammonia fuel cell system at intermediate temperature range, if the ammonia can be electro-oxidized at the surface of hydrogen membrane anodes. In this study, we studied the ammonia-fueled HMFC based on Pd dense anode supports and BaCe0.8Y0.2O3 (BCY) electrolyte thin films. BCY electrolyte thin films of 1.0 mm thickness were deposited on a Pd foil by RF magnetron sputtering. La0.5Sr0.5Fe0.8Co0.2O3 (LSCF) cathode was screen-printed on BCY and thus, HMFC was obtained. The direct ammonia-fuelced HMFC clearly gives a stable open circuit voltage (OCV) of about 0.9 V and a maximum peak power density of about 100 mW cm-2 at 600˚C.

BaCe0.85Y0.15O2.925 dense layer by wet powder spraying as electrolyte for SOFC/SOEC applications

Y-doped barium cerate (BCY) is a protonic conductor showing an excellent conductivity that recently received increasing attention as an electrolyte in solid oxide cells operating at low–intermediate temperatures (<650°C). It has a poor thermal–chemical stability and this limits its practical applications. However, its attractive high conductivity makes BCY suitable to be inset between two other more stable thin layers to form a unique electrolyte in a protonic cell, with only a slight loss of electrochemical performance. In order to obtain a cost-effective and dense BCY electrolyte, the wet powder spraying (WPS) technique was considered in this study for the deposition of a thin (≈10μm) and dense BCY coating (BaCe0.85Y0.15O2.925) on a porous Ni-BCY substrate, to produce an anode-supported cell. To the authors' knowledge, only one paper recently appeared in the literature dealing with BCY deposition by WPS, but in that case the sprayed layer was isostatically pressed to obtain a dense layer.In this study, the optimization of suspension formulation, deposition conditions and sintering process allowed achieving a dense BCY layer without any additional step. The description of the spraying technique details and the parameters affecting a good film densification is reported. Furthermore, such a technique optimized for BCY can then be also considered for the production of thin electrolyte multilayers.

Chemical stability study of nanoscale thin film yttria-doped barium cerate electrolyte for micro solid oxide fuel cells

The chemical stability of a nanoscale yttria-doped barium cerate (Y–BaCeO3 or BCY) thin film electrolyte for low temperature solid oxide fuel cells (SOFCs) are investigated in the temperature range of 300–400 °C. The micro-SOFCs using 300 nm-thick BCY electrolyte show a poor fuel cell performance and continuous decrease in open circuit voltage (OCV) with higher operating temperatures. Characterization results from X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) revealed that the observed degrading fuel cell performance is attributed to the rapid decomposition of BaCeO3 into BaCO3, Ba(OH)2, and CeO2 from reactions with CO2 and H2O during fuel cell test. The lattice parameters of BCY expanded during fuel cell test, resulting in the formation of micro cracks along the electrolyte that possibly induced the OCV drop. The reactions of nano thin film BCY with CO2 and H2O are both active at temperature between 300 and 400 °C, which is unlike bulk BCY material where only the reaction with CO2 is significant. The reduction of Ce4+ species into Ce3+ in the BCY electrolyte has also lead to an electronic conduction in BCY that lowered OCVs.

Measurement of hydrogen and oxygen chemical potential in yttria doped barium cerate (BCY) electrolyte of anode-supported protonic ceramic fuel cells

Yttria doped barium cerate (BCY) electrolyte, Ni + BCY anode supported protonic ceramic fuel cells were fabricated with Pt reference electrodes embedded in a thin (∼40 microns) electrolyte layer. The embedded electrodes function as selective probes exchanging only electrons with the BCY so that the voltage measurements (ΔV) using the embedded probes through the electrolyte correspond to a change in the reduced negative electrochemical potential of electrons (Δφ). Using this method, the corresponding change in hydrogen and oxygen chemical potential (ΔμH2, ΔμO2) or partial pressure of hydrogen and oxygen (ΔpH2, ΔpO2) were determined on the basis of the local equilibrium assumption, allowing us to investigate ionic and electronic transport properties through the BCY electrolyte. The results indicate that the pH2 and pO2 change mainly occurs across the middle electrolyte region while the electrolyte regions close to the anode and the cathode showed very small variation. The present work revealed that the BCY electrolyte consists of three major parts with different transport properties; 1) mixed ionic-electronic conduction in the electrolyte close to the anode side (reducing atmosphere), 2) predominantly ionic conduction in the middle region, 3) mixed ionic-hole conduction in the electrolyte close to the cathode side (oxidizing atmosphere).

Advanced Electrodes for Intermediate Temperature Proton Conducting Fuel Cell

In order to develop efficient Protonic Ceramic Fuel Cell, different composite electrodes made of BaCe0.9Y0.1O3 and NiO or mixed ionic-electronic conductor (BSCF) were investigated as anode and cathode respectively. Ni-BCY composite synthesized by combustion offers sufficient open porosity, shows an electrical conductivity superior to 1000 S.cm-1 and a very low ASR value (0.06 Ω.cm2 at 600°C). The electrochemical properties of BSCF-BCY composite cathode have been studied and the obtained ASR value (0.53 Ω.cm2 at 600 °C) is lower compare to pure BSCF. An anode supported single cell (25 mm in diameter) consisting of a bi-layer Ni-BCY cermet, a dense 15 mm BCY electrolyte and a BCY-BSCF composite cathode were assembled and tested from 550 to 700 °C. Open circuit voltages of 1.055 V and 1.026 V were achieved at 600 °C and 700 °C. Maximum power densities of 156 and 293 mW.cm-2 were obtained at 600 and 700 °C.

A chemically stable electrolyte with a novel sandwiched structure for proton-conducting solid oxide fuel cells (SOFCs)

A chemically stable electrolyte structure was developed for proton-conducting SOFCs by using two layers of stable BaZr0.7Pr0.1Y0.2O3−δ to sandwich a highly-conductive but unstable BaCe0.8Y0.2O3−δ electrolyte layer. The sandwiched electrolyte structure showed good chemical stability in both CO2 and H2O atmosphere, indicating that the BZPY layers effectively protect the inner BCY electrolyte, while the BCY electrolyte alone decomposed completely under the same conditions. Fuel cell prototypes fabricated with the sandwiched electrolyte achieved a relatively high performance of 185mWcm−2 at 700°C, with a high electrolyte film conductivity of 4×10−3Scm−1 at 600°C.

Protonic and Electronic Conduction in Proton Conductive Solid Oxide Fuel Cells

ABSTRACTProtons can fit into the perovskite structure because the O-O distance is approximately that of ice. However, to achieve charge balance, -2e charge must be added for every two protons added. If O2- vacancies are introduced, for instance by doping barium cerate with yttrium to obtain ${\it Ba}^{2 + } {\it Ce}_{1 - {\it x}}^{4 + } {\it Y}_{\it x}^{3 + } {\it O}_{3 - {\it x}/2}^{2 - }$ (BCY), each filled vacancy will add -2e charge. Proton concentration and conductivity can be increased by exposing BCY to steam molecules, which dissociate into 2 protons and an O2- ion. Our impedance spectroscopy measurements and solid oxide fuel cell (SOFC) work shows that exposure to H2 on the anode side can add protons. This requires addition of O2- ions on the cathode side from O2 in air. Alternatively, electrons could be added because BCY is a weak electronic semiconductor. BCY is a hole conductor, and this conductivity decreases upon exposure to steam or H2. From our analysis of V(i) curves for SOFCs with BCY electrolyte, at low H2 concentration, increasing this concentration decreases electronic conductivity somewhat, consistent with adding electrons and reducing hole carrier concentration. At higher H2 concentrations, electronic conductivity remains constant.Proton transfer in perovskites such as BCY resembles that in usual H‑bonded crystals. Such transfer requires two steps, both needed for dc conductivity. One is intrabond proton transfer, O‑H O→O H-O. The other is a proton jump from one H-bond to an adjacent bond, equivalent to rotation of an O-H unit about the O ion. The main difference from usual H-bonded crystals is that the adjacent O-O pair most likely has no proton between the O ions, so that the Pauling ice rule precluding 2 protons in one bond is not much of a restriction in perovskites because the proton concentration is typically below 0.2 per formula unit. Another difference is that, though protonic semiconductor activation energies are high, in the 0.5 to 1 eV range, the high operating temperatures of SOFCs, 600 to 900 oC, give useful amounts of power per unit area, or in the electrolysis mode, useful amounts of H2 out for steam and electric power input.Two applications for proton-conducting perovskite ceramics are SOFCs and hydrogen separation membranes (HSMs). For SOFCs, we have modeled the V(i) behavior with almost no adjustable parameters, and have succeeded in coming close to the Nernst open‑circuit potential as well as fitting the V(i) curves for a variety of H2/O2 partial pressure combinations. For HSMs, unlike for SOFCs, an electronic conductivity comparable to the protonic conductivity is desirable, to avoid using a cermet which may crack because of differential thermal expansion.In conclusion, many oxides and fluorides have O-O or F-F separations in the H‑bonding range and will provide a stimulating playground for further basic and applied research on proton incorporation and dynamics in solids.

A novel way to improve performance of proton-conducting solid-oxide fuel cells through enhanced chemical interaction of anode components

We proposed a novel way to improve the cell performance of proton-conducting solid-oxide fuel cells by increasing the chemical interaction between the anode components using BaZr 0.4Ce 0.4Y 0.2O 3−δ (BZCY4) as the ionic conducting phase of anode for a fuel cell with a BaCe 0.8Y 0.2O 3−δ (BCY) electrolyte. The strength of the chemical interaction between NiO and the ionic conducting phase (BZCY4 or BCY) was analyzed by the hydrogen temperature-programmed reduction (H 2-TPR) technique. The effect of chemical interaction between NiO and the ionic conducting phase on the NiO diffusivity was investigated by SEM-EDX. The results demonstrated NiO had a much stronger interaction with BZCY4 than with BCY, thereby resulting in suppressed diffusivity of NiO into the BCY electrolyte. Using BZCY4 as the ionic conducting phase of the anode, a cell with an ohmic resistance of 0.65 Ω cm 2 at 700 °C was obtained. In contrast, a cell with BCY as the ionic conducting phase of the anode had an ohmic resistance of 0.82 Ω cm 2 at 700 °C. Therefore, the single cell with NiO + BZCY4 anode showed a peak power density higher than that of the cell with the NiO + BCY anode.

Fabrication and performance of a carbon dioxide-tolerant proton-conducting solid oxide fuel cells with a dual-layer electrolyte

A proton-conducting solid oxide fuel cells with a dual-layer electrolyte, constructed of a highly protonic conductive BaCe 0.8Y 0.2O 3−δ (BCY) electrolyte and chemically stable BaZr 0.4Ce 0.4Y 0.2O 3−δ (BZCY4) electrolyte, was easily fabricated by dry pressing the electrolyte powders onto an NiO + BZCY4 anode substrate, followed by co-sintering at a high temperature. The performance of the as-fabricated cell with the BCY and BZCY4 dual-layer electrolyte was studied. Peak power densities of 249 and 101 mW cm −2 were achieved at 700 and 500 °C, respectively. Zinc was applied as a sintering promoter to increase the relative density of the BZCY4 electrolyte. Cross-sectional micrographs of the as-fabricated, dual-layer electrolyte cells were obtained by scanning electron microscopy. The results showed that the sintering ability of BZCY4 was improved by using zinc as sintering aid. A cell with BCY and zinc-modified BZCY4 dual-layer electrolyte delivered peak power densities of 276 and 247 mW cm −2 and OCVs of 1.03 and 1.02 V at 700 °C under humidified hydrogen and 15% CO 2-containing hydrogen atmospheres, respectively. The operation stability of the dual-layer electrolyte cell under a 15% CO 2-containing hydrogen atmosphere was also investigated.

Y-doped BaCeO 3− δ nanopowders as proton-conducting electrolyte materials for ethane fuel cells to co-generate ethylene and electricity

Y-doped BaCeO 3− δ (BCY) powders synthesized using a combustion method are pure perovskite phases. The particles are uniform spherical particles about 50 nm. The properties of BCY proton-conducting electrolyte sintered at different temperatures from pressed nanopowders were systematically investigated. Dense BCY pellets are obtained at temperatures higher than 1400 °C for 10 h. Electrical conductivity and resistance to CO 2 atmosphere each increase with sintering temperature. Fuel cells having about 0.8 mm thick BCY electrolyte and Pt electrodes co-produce 151 mW cm −2 electrical power and value-added ethylene with selectivity over 90% at ethane conversion about 35% at 700 °C.

Cell Performance Stability of HMFC using Ba(Ce1-xZrx)0.8Y0.2O3 Perovskite Type Proton Conductor as Electrolyte

AbstractWe have developed a new type of FC which shows high performance at intermediate temperatures to solve the disadvantage of using hydrocarbon as fuel to FC system. This new FC is an ultra-thin proton conductor electrolyte supported by a metal hydrogen membrane. We have named itHydrogenMembraneFuelCellThe HMFC using BaCe0.8Y0.2O3 (BCY) as the electrolyte and pure Palladium as the substrate exhibits a high cell performance of 2.7 A/cm2 @0.5V, 873K and 1.8 A/cm2 @0.5V, 673K. But the BCY cell performance drops rapidly during several hours. It was inferred that this phenomenon is caused by BCY electrolyte dissolved by hydrothermal reaction with H2O vapor which was generated by the fuel cell reaction.We studied the possibility as HMFC electrolyte of Ba(Ce0.5Zr0.5)0.8YO3 (BCZY) and BaZr0.8Y0.2O3 (BZY) which are exchanged the B site of BCY perovskite ceramic from Ce to Zr to improve the resistance against the hydrothermal dissolution. BCZY and BZY confirmed the resistance against the hydrothermal dissolution improved compared with BCY by analyzing after the hydrothermal treatment. The BCZY cell shows the same level of the performance as the BCY cell and the performance stability has improved over the BCY cell.