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We study the structure, crystallization, and performances of the sealing glasses with the composition (mol.%) of 12Al2O3·8B2O3·40SiO2·40RO (R = Mg, Ca, Sr) for solid oxide fuel cells (SOFCs) before and after isothermal treatment at 700°C, which is within the operation temperature range (600‐800°C) of SOFCs. The crystallization behavior has been investigated by differential scanning calorimetry and X‐ray diffraction under both dynamic and isothermal conditions. The structural evolution is probed using the Raman and nuclear magnetic resonance spectroscopies. The performances of the sealing glasses are characterized in terms of the coefficient of thermal expansion, the crystallization‐induced stress at glass–steel interface. We find that strong crystallization occurs at the operation temperature (700°C) far below the crystallization onset temperature measured by DSC. The structure origin of this anomalous crystallization is discussed in terms of structural heterogeneity of the three studied glasses. We determine the residual stress at the interface between the Ca‐containing glass and the steel after isothermal treatment at 700°C for 48 h, but this stress does not lead to falling off the glass layer from the steel. This indicates that this glass is a good candidate to be applied in SOFCs. [ABSTRACT FROM AUTHOR]

A numerical model for ceria-based solid oxide fuel cells (SOFCs) with bi-layer electrolyte is proposed to evaluate the internal short circuit by the comparison of two cell configurations: the electronic barrier electrolyte adjacent to cathode and anode, respectively. In this model, the activation polarization of the electrode reaction and the charge transport of the electrolyte with both n/p-type electronic and oxygen ion conductivity are considered. The activation polarization and the charge transport are described by the Butler-Volmer equation and the Nernst-Planck equation, respectively. Parametric simulations are performed to compare the two bi-layer electrolyte configurations in terms of the open circuit voltage, I–V relationship, leakage current density, power density at 0.7 V, oxygen partial pressure distribution and electrochemical efficiency as functions of the temperature and thickness ratio of the electronic barrier electrolyte. From our modeling results, the cell configuration of which the barrier electrolyte is adjacent to cathode has significant p-type leakage current, leading to the lower open circuit voltages and electrochemical efficiency than the other one. The oxygen partial pressure distribution under the open circuit displays the “S” type in the barrier layer, which is related to the change of the n/p-type conductivity of the barrier layer. Besides, the activation polarization greatly influences the open circuit voltage and the oxygen partial pressure distribution between boundaries of electrolytes under open circuit. It is also found that the thickness ratio of the electronic barrier electrolyte can be optimized to maximize the electrochemical performance by balancing the open circuit voltage and ohmic polarization loss. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a series of Sr–Ba–borosilicate glass-ceramics (10–40mole% B2O3) were prepared to investigate the effect of borate content on the thermal properties as well as volatilization behavior. For crystallized samples with increasing borate contents, the dilatometric softening points decrease, from 702 to 660°C, as do the coefficients of thermal expansion, from 9.5 to 7.5×10−6 K−1. In addition, the weight loss from these materials, in wet forming gas at 780°C for 28 days, decreases by a factor of two as the borate content increases from 10 to 40mole%. The borate-containing phase, SrB2O4, forms with increasing borate content. The significant improvement in stability against volatility can be attributed to the formation of SrB2O4, which is consistent with the results of thermochemical calculations. These results therefore indicate one way to design sealing compositions to use B2O3 to tailor thermal properties without sacrificing thermal stability. [Copyright &y& Elsevier]

Abstract: The chemical compatibility of sealing glass is of great importance for Solid oxide fuel cell (SOFC). In this work, the interfacial reaction between sealing glass and Cr-containing interconnect alloy is characterized by reacting Cr2O3 powders with a representative SrO-containing glass crystallized by different heat-treatment schedules. The crystalline structure and crystalline content of sealing glass are determined by X-ray diffraction. The results show that the fraction of Cr6+ decreases from 39.8 ± 1.9% for quenched glass to 8.2 ± 0.4% for glass crystallized at 900 °C for 2 h. In addition, the interfacial reaction can be further reduced with increasing crystallization temperature and time as well as the addition of nucleation agent (TiO2). The formation of some Sr-containing crystalline phases, Sr2SiO4 and Sr(TiO3), contributes to the improvement of chemical compatibility of sealing glass, in agreement with the results of thermodynamic calculations. [Copyright &y& Elsevier]

Abstract: High-temperature interactions between glass–ceramic sealants and Cr-containing ferritic interconnects used in solid oxide fuel cells (SOFC) lead to the formation of detrimental chromate interfacial phases, such as BaCrO4 or SrCrO4, which can cause mechanical failure of the SOFC. In this work, these interactions are characterized by reacting Cr2O3 powders with a SrO-containing sealing glass and by characterizing representative reaction couples between the glass and 430 stainless steel. The extent of chromate formation depends on the reaction time and temperature, and the effect of the partial pressure of oxygen is modeled by thermochemical calculations. [Copyright &y& Elsevier]

Abstract: In this paper, a ceramic sealant (CaB2O4) is developed for the self-healing design of solid oxide fuel cells (SOFCs). The interface between this ceramic sealant and the anode-supported electrolyte, e.g., 8mole% yttria-stabilized zirconia (8YSZ), remains intact after sixty thermal cycles from 800°C to room temperature. An in situ observation verifies that the micro-indentation on the surface of this material can be healed when heating from room temperature to 920°C at a heating rate of 40°Cmin−1. In addition, the weight loss of CaB2O4, held at 850°C in air for 28 days, decreases from 3.26±0.73 for sealed species to 0.81±0.04mgcm−2 for fully crystallized species; meanwhile, the weight loss of CaB2O4, held at 850°C in wet forming gas (30vol% water vapor) for 28 days, decreases from 14.80±1.83 for sealed species to 6.36±0.64mgcm−2 for fully crystallized species. Combining with the good mechanical stability and thermal-stability, this self-healing ceramic sealant provides promising solution for the sealing challenge of planar SOFCs. [Copyright &y& Elsevier]

In order to realize the efficient and stable operation of the solid oxide fuel cell (SOFC)-combined heat and power (CHP) system in the typical applied scenario, three different energy management schemes are proposed in this study. First, a coupled calculation model of the solid oxide fuel cell-gas turbine-combined heat and power (SOFC-GT-CHP) system with a rated power of 30 kW for the SOFC stack is constructed. The inlet temperature and inlet pressure of the SOFC stack are optimized. The recommended design for the proposed system is thence obtained. Second, three operation schemes of SOFC-GT-CHP are proposed. They consist of the operation scheme of single-stack, multi-stack and optimal operation scheme coupled with vanadium redox flow battery (VRB). Finally, four types of typical applied scenarios in North China are selected. The real-time performance of the SOFC-GT-CHP system when applying three different operation schemes is obtained and comparatively analyzed. The results are presented as follows. First, the SOFC-GT-CHP system achieves a rated power of 44.50 kW and a rated system efficiency of 47.20 % when the inlet temperature and pressure of the stack are preferably 505 °C and 709.1 kPa. Second, the application of the multi-stack SOFC-GT-CHP system has the advantage of high efficiency in the low-load operation domain. With a net output power at 20 kW, the time average efficiency of SOFC-GT-CHP is increased from 38.37 % to 46.96 %. Finally, the SOFC-GT-CHP system achieves the highest time average generation efficiency of 46.13 % in the hotel applied scenario when applying the optimal operation scheme coupled with VRB. This meets the practical operation requirement of the SOFC stack. The reduction of the net output power range of SOFC-GT-CHP is 67.87 %. It shows that the optimal operation scheme is efficient and stable. The study can provide a reference for the energy management of the SOFC-GT-CHP system in typical applied scenarios. • The recommended design solution for SOFC-GT-CHP is obtained by constructing the coupled calculation model. • Operation schemes of SOFC-GT-CHP including the single-stack, multi-stack and optimal scheme coupled with VRB are proposed. • The characteristics of the proposed three operation schemes are studied and compared based on simple user loads. • A comparative study of the performance of SOFC-GT-CHP when applying three schemes is conducted with 4 applied scenarios. [ABSTRACT FROM AUTHOR]

Abstract: The poor thermodynamic and thermal stability of self-healing glass sealants restrict their applications in planar solid oxide fuel cells (SOFCs). In this paper, a calcium borate crystalline is prepared by melting-quench and a subsequent crystallization. The crystalline phases include CaB4O7 and CaB2O4. The in situ observation reveals that the micro-indentation on the surface of such crystalline can be healed when heating from room temperature to 840°C at a heating rate of 40°Cmin−1. Combining with the improved thermal stability, the crystalline sealant with desired self-healing property, at the operational temperature of SOFCs (e.g., 700–900°C), provides additional solution for the sealing challenge of SOFCs. [ABSTRACT FROM AUTHOR]

Abstract: High temperature interactions between glass–ceramic sealants and ferritic interconnects used in solid oxide fuel cells (SOFCs) lead to the formation of detrimental chromate phases, such as BaCrO4 or SrCrO4, which lead to the mechanical failure of the cell. In present work, the interactions are characterized using model reactions between Cr2O3 and glass powders. It is found that the addition of MnO2 reduces the formation of SrCrO4 more significantly than that of ZnO and La2O3, in the SOFCs operational temperature range (e.g., 900°C). In addition, the mechanism of the reduction of the chromate phase by different additives is discussed in terms of the possible competing reactions. [Copyright &y& Elsevier]

Glass and glass-ceramic are one of the key sealing materials for solid oxide fuel cells (SOFCs) and they need to meet stringent requirements for long-term operation at high temperatures. Here, we report for the first time the incorporation of aluminum nitride (AlN) dopant into borosilicate glasses and glass-ceramics so as to tailor their basic properties and sealing performance. The results show the AlN-doped glass-ceramics exhibit remarkably enhanced thermal stability and chemical compatibility when adhering to Y 2 O 3 -ZrO 2 electrolyte. The electrical conductivity is also significantly reduced by the AlN doping, and the conductivity of 15 wt.% AlN-doped glass-ceramic is nearly two orders of magnitude lower than that of the undoped glass-ceramic. This work indicates that AlN doping is an effective strategy to obtain a reliable borosilicate glass-ceramics for SOFCs. [ABSTRACT FROM AUTHOR]

The development of high active cathode materials owning low activation energy (Ea) is the most critical core for protonic solid oxide fuel cells (P-SOFCs). Considering this challenge, we herein develop Ba 0.9 La 0.1 Co 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3-δ -BaZr 0.1 Ce 0.7 Y 0.2 O 3-δ (BLCFZY-BZCY) composite as a new proton conducting cathode for P-SOFCs. Anode supported single cells with BLCFZY-BZCY cathode show remarkable performance and low electrode Ea of 83.41 kJ mol −1 . High power densities of 752 and 206 mW cm −2 are achieved at 700 and 500 °C, respectively, while corresponding electrode interfacial polarization resistances (Rp) are 0.08 and 1.2 Ω cm 2 . Interestingly, the electrode polarization processes with a high resolution based on the impedance spectra data were further analyzed using the distribution function of relaxation time (DRT). Three same polarization peaks (P1, P2, P3) meaning three rate-limiting steps are existed in the DRT curves with different temperature, where P3 resulting from the cathode-electrolyte interfacial resistance with oxygen species involved reactions is the dominant rate-limiting step with a proportion of over 49.6% while the anode-electrolyte interfacial resistance corresponding to P1 has almost no increase, from 0.03 Ωcm 2 to 0.09 Ωcm 2 . The experimental results demonstrate BLCFZY-BZCY composite can be a promising proton conducting cathode for P-SOFCs. [ABSTRACT FROM AUTHOR]

In solid oxide fuel cells (SOFCs), it is important that the sealing glass has adequate mechanical strength (rigidity) to withstand stack loads while simultaneously having appropriate resiliency to release the internal stress and thus resist cracking. However, at present, sealing glass is either resilient or rigid. Animal teeth exhibit a bilayer structure that combines remarkable surface hardness to withstand mastication loads with the high resiliency of the inner layer to resist crack propagation. Drawing from this, in this study, we selected a heat-treatment temperature of 700 °C to simulate the operating temperature of the sealing glass and SOFCs, and carried out experimental and theoretical investigation of a typical borosilicate sealing-glass system. The results revealed that surface strengthening occurs within 200 nm depth as the heat-treatment time increases; that is, there is a gradient change in the mechanical property from the surface to the interior of glass, indicating that the surface has greater hardness and elastic modulus to bear stack loads, while the interior has better resiliency and may help resist crack initiation and propagation. A possible mechanism for this strengthening is proposed. The 4-coordinated B and Al centred BO 4 and AlO 4 can form a glass network structure with SiO 4 (i.e., B–O–Si, Al–O–Si), which may lead to surface strengthening due to the increase in the degree of network crosslinking. [ABSTRACT FROM AUTHOR]

Abstract The high volatility of boron from borosilicate glass sealants often leads to boron deposition and poisoning of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF) cathode, presenting a challenge for the development of reliable solid oxide fuel cells (SOFCs). In this paper, we report that boron volatilization from borosilicate glass at 700 °C can be significantly suppressed by appropriate NiO dopant, mainly due to the increase of Si-O-B linkages in the combining B-O− and Si-O− network. Also, the formation of boron-containing phase in NiO-doping glass-ceramics has been studied, which suppresses the reaction between glass and LSCF cathode after heat treatment at 700 °C for 1000 h. Moreover, the change of crystalline phases leads to an improvement in thermal and electrical properties. We believe that our findings will open a new way for the design and development of the reliable sealing glass for SOFCs applications. [ABSTRACT FROM AUTHOR]

Abstract Crack formation at the interface between sealing glass and other cell components is one of the key issues in constraining the development of solid oxide fuel cells (SOFCs). Herein, we report our finding on tuning the mechanical and thermal properties of borosilicate glass by doping Nb 2 O 5. We observe the formation of Ba 3 Nb 10 O 28 crystalline phase in the Nb 2 O 5 -doped glass, leading to significantly enhanced crack-resistant and self-healing abilities of the glass. In addition, we demonstrate long-term thermal and chemical stability at the sealing interface between the Nb 2 O 5 -doped glass-ceramics and Y 2 O 3 -ZrO 2 electrolyte after heat-treatment at 700 °C for 1000 h. The possible mechanism for the improved crack-resistant and self-healing properties is discussed. [ABSTRACT FROM AUTHOR]

The rigid nature of sealing glass-ceramics restricts the thermal cycling stability of Solid Oxide Fuel Cells (SOFCs), which thus evokes an interest in designing a sealing glass without crystallization under the operational condition of SOFCs. In this paper, we report that the sealing performance of 30Na 2 O-70SiO 2 (in mole%) glass-ceramic can be significantly improved by Fe 2 O 3 dopant through a composite approach. In particular, the crystallization in glass can be suppressed by appropriate Fe 2 O 3 dopant amount (8 mol%), which results in the improved sealing property of glass. In addition, the glass modified with Fe 2 O 3 shows good chemical compatibility with 8 mol% yttria-stabilized zirconia (8YSZ) electrolyte and metallic interconnect (430 stainless steel) in dual atmospheres. The possible mechanism for the improved sealing performance of 30Na 2 O-70SiO 2 glass-ceramic by this unique composite approach is also discussed. [ABSTRACT FROM AUTHOR]

Bismuth oxide is as an active promoter in enhancing the ionic conductivity and electrocatalytic activity of manganite oxygen electrodes of solid oxide cells, but there are very limited reports on the formation and evolution of electrode/electrolyte interface of bismuth oxide-manganite composite electrode under the influence of electrochemical polarization. Herein, we report the effect of electrochemical polarization and direction of polarization current on the electrocatalytic performance and electrode/electrolyte interface of a (La 0·8 Sr 0.2 ) 0.95 Mn 0·95 Pt 0·05 O 3+δ -Er 0.4 Bi 1·6 O 3 (LSMPt-ESB) composite oxygen electrode assembled on zirconia electrolyte. The cell with the LSMPt-ESB electrode produces outstanding performance for power generation and steam splitting, and it is stable without noticeable degradation during operation at 600 °C for 350 h in the fuel cell mode. The cathodic polarization induces in operando formation of electrode/electrolyte interface with observation of an Er-deficient LSMPt-ESB dense layer and Er-rich (Er,Bi,Mn)O x particles on the zirconia electrolyte surface. This is different to the case of dwell under open circuit and in particular under anodic polarization conditions. The present study gains insights into the development of high performance, reliable bismuth oxide-manganite composite oxygen electrode for reduced temperature solid oxide cells. [ABSTRACT FROM AUTHOR]

At present, the insufficient thermo-mechanical stability of sealing glass presents a challenge for solid oxide fuel cells (SOFCs). In this work, we report for the first time that a rigid-resilient transition occurs in a calcium borosilicate sealing glass upon heating at 700 °C for different durations. The elastic modulus increases from 28.1–40.0 GPa for 24 h to 92.3–105.1 GPa for 100 h, while the corresponding hardness increases from 2.5–3.1 GPa to 8.1–9.2 GPa. In addition, a possible mechanism for the rigid-resilient transition has been proposed. The reported results provide a new approach to solve the sealing problem of SOFCs. [ABSTRACT FROM AUTHOR]

Active and stable oxygen electrode is probably the most important in the development of solid oxide electrolysis cells (SOECs) technologies. Herein, we report the successful development of mixed ionic and electronic conducting (MIEC) La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) perovskite oxides directly assembled on barrier-layer-free yttria-stabilized zirconia (YSZ) electrolyte as highly active and stable oxygen electrodes of SOECs. Electrolysis polarization effectively induces the formation of electrode/electrolyte interface, similar to that observed under solid oxide fuel cell (SOFC) operation conditions. However, in contrast to the significant performance decay under SOFC operation conditions, the cell with directly assembled LSCF oxygen electrodes shows excellent stability, tested for 300 h at 0.5 A cm −2 and 750 °C under SOEC operation conditions. Detailed microstructure and phase analysis reveal that Sr segregation is inevitable for LSCF electrode, but anodic polarization substantially suppresses Sr segregation and migration to the electrode/electrolyte interface, leading to the formation of stable and efficient electrode/electrolyte interface for water and CO 2 electrolysis under SOECs operation conditions. The present study demonstrates the feasibility of using directly assembled MIEC cobaltite based oxygen electrodes on barrier-layer-free YSZ electrolyte of SOECs. [ABSTRACT FROM AUTHOR]

Boron volatility is one of the most important properties of borosilicate-based glass sealants in solid oxide fuel cells (SOFCs), as boron contaminants react with lanthanum-containing cathodes, forming LaBO 3 and degrading the activity of SOFCs. Here, we report that the reaction between the volatile boron and a La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) cathode during polarization can be significantly reduced by doping aluminoborosilicate glass with Gd 2 O 3 . Specifically, the Gd cations in glass with 2 mol.% Gd 2 O 3 dissolve preferentially in the borate-rich environment to form more Gd-metaborate structures and promote the formation of calcium metaborate (CaB 2 O 4 ); they also condense the B–O network after heat treatment, which suppresses poisoning by boron contaminants on the LSCF cathode. The results provide insights into design and development of a reliable sealing glass for SOFC applications. [ABSTRACT FROM AUTHOR]

Sr doping is a common strategy to enhance the electrocatalytic activity of perovskite cathode materials of solid oxide fuel cells (SOFCs), but the tendency of Sr surface segregation, chemical incompatibility with yttria-stabilized zirconia (YSZ) and interaction with volatile contaminants such as chromium in SOFC stacks lead to a loss of long-term cell performance. Herein, a Sr-free and Pd-doped La 0.95 Co 0.19 Fe 0.76 Pd 0.05 O 3-δ (LCFPd) cathode is directly assembled on a barrier-layer-free YSZ electrolyte cell without conventional high temperature pre-sintering. The cell with the directly assembled LCFPd-GDC (gadolinium-doped ceria) composite cathode exhibits a peak power density of 1035 mW cm − 2 and excellent operation stability at 750 °C for 200 h. Cathodic polarization significantly enhances the electrode/electrolyte interface contact, indicated by the substantial decrease of cell ohmic resistance from 0.28 Ω cm 2 to 0.14 Ω cm 2 after polarization at 500 mA cm − 2 and 750 °C for 120 h. Detailed elemental analysis indicates that doped Pd could be segregated on the electrode surface under fuel cell operation conditions, which significantly enhances the electrocatalytic activity for the O 2 reduction reaction. This study provides new strategy to develop cobaltite based perovskite materials directly on YSZ electrolyte. [ABSTRACT FROM AUTHOR]

In planar Solid Oxide Fuel Cells (SOFCs), the boron species volatilize from glass seals, and react with lanthanum-containing cathodes (i.e., La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 − δ , LSCF) to form LaBO 3 under cathodic polarization, which decomposes the perovskite structure and consequently decreases the electrochemical activity of cathode. In this study, Nb 2 O 5 and Gd 2 O 3 are added to an aluminoborosilicate glass to reduce the boron volatility from glass and the reaction between sealing glass and LSCF cathode. Both Nb 2 O 5 and Gd 2 O 3 doping increases the network connectivity, but Nb 2 O 5 doping enhances the [BO 3 ] → [BO 4 ] transition and reduces the boron volatility from glass seals, thus effectively suppressing the deposition and poisoning of boron contaminants on the LSCF cathode. However, an obvious degradation of the electrocatalytic activity of LSCF occurs in the presence of Gd 2 O 3 -doped glass. The relationship between glass structure and glass/cathode interaction has been established to provide useful information for designing stable sealing materials for SOFC applications. [ABSTRACT FROM AUTHOR]

In solid oxide fuel cell (SOFC) stacks, the volatile boron species present in the sealing glass often react with the lanthanum-containing cathode, degrading the activity of the cathode (this phenomenon is known as boron poisoning). In this work, we report that this detrimental reaction can be effectively reduced by doping bismuth-containing borosilicate sealing glass-ceramic with a niobium dopant. The addition of Nb 2 O 5 not only condenses the [SiO 4 ] structural units in the glass network, but also promotes the conversion of [BO 3 ] to [BO 4 ]. Moreover, the Nb 2 O 5 dopant enhances the formation of boron-containing phases (Ca 3 B 2 O 6 and CaB 2 Si 2 O 8 ), which significantly reduces the volatility of boron compounds in the sealing glass, suppressing the formation of LaBO 3 in the reaction couple between the glass and the cathode. The reported results provide a new approach to solve the problem of boron poisoning. [ABSTRACT FROM AUTHOR]

The volatile boron species from sealing glass-ceramics have a significant poisoning effect on the electrochemical activity of Solid Oxide Fuel Cell (SOFC) cathodes. The reaction between boron-containing sealing glass-ceramics and cathodes thus presents a challenge for the development of SOFC. Here we report for the first time that the addition of La 2 O 3 can significantly reduce the boron volatility from sealing glass-ceramics and consequently the formation of LaBO 3 in reaction couple between glass and (La,Sr)(Co,Fe)O 3 (LSCF) cathode. In particular, the boron volatility can be reduced by about 6 times with the addition of 4 mol.% La 2 O 3 (3.7 × 10 −3 vs. 0.6 × 10 −3 %). The addition of La 2 O 3 condenses the structure of glasses and glass-ceramics, contributing to the decrease in boron volatility from glass-ceramics. In addition, La 2 O 3 dopant favors the formation of boron-containing phase (La 5 SiBO 13 ) in glass-ceramics, which dramatically reduces the boron volatility. The reported results provide an effective approach for solving the sealing challenge. [ABSTRACT FROM AUTHOR]

The electrical property of sealing glass–ceramics is of great importance for Solid Oxide Fuel Cell (SOFC) applications. In spite of their good sintering property, CeO 2 -containing glass–ceramics often lack in sufficient electrical resistance, due to the formation of CeO 2 as a conductive phase. Here we report for the first time that the electrical conductivity of CeO 2 -containing glass–ceramics can be reduced by an order of magnitude with HfO 2 dopant. A mechanism on the improved electrical property has also been proposed in terms of the structural change in HfO 2 -doped glass–ceramics. In addition, the relationship between phase evolution of HfO 2 -doped glass–ceramics and the change in conductivity with operational time has been systematically investigated. Moreover, HfO 2 -doped glass–ceramics show good chemical compatibility with 8 mol.% yttria-stabilized zirconia (8YSZ) electrolyte, after held at 750 °C for 500 h. The reported results support the suitability of prepared glass–ceramics as sealing materials for SOFC applications. [ABSTRACT FROM AUTHOR]

The insufficient thermal–mechanical stability of sealing interface presents a challenge for the development of solid oxide fuel cells (SOFCs). Here we report for the first time that the presence of gadolinia-doped ceria (GDC) electrolyte leads to the formation of two hardystonite phases, (Ca 0.9 Zn 0.03 ) 2 (Al 0.63 Zn 0.37 )(Si 0.69 Al 0.31 ) 2 O 7 and Ca 2 ZnSi 2 O 7 , in the reaction couples between boroaluminosilicate sealing glass–ceramics and GDC powders held at 700 °C for 30 days. Similarly, the aggregation of these two hardystonite phases also occurs at the interface between GDC and sealing glass–ceramics under identical heat-treatment. In particular, (Ca 0.9 Zn 0.03 ) 2 (Al 0.63 Zn 0.37 )(Si 0.69 Al 0.31 ) 2 O 7 becomes the dominant phase at the sealing interface when the heat-treatment time increases from 7 days to 30 days. Moreover, the sealing interface remains intact after thermal cycles for 100 times, indicating the excellent thermal–mechanical stability of hardystonite phases. Finally, the possible mechanism on the phase evolution of glass–ceramic at the sealing interface has been proposed. [ABSTRACT FROM AUTHOR]

In this paper, MnO 2 is added to CaO–SrO–B 2 O 3 –SiO 2 sealing system to control the redox glass/metal interfacial reaction in Solid Oxide Fuel Cells. The effect of MnO 2 dopant on the valance states of Mn ions in glasses, the glass structure and glass/metal interfacial reaction is systematically investigated. The quenched glasses contain Mn 2+ ion only; whereas, the Mn 3+ content in glasses, held at 600 °C for 9 h, increases with increasing MnO 2 dopant. The good bondage can be observed at the interfaces between Crofer 22APU and glass containing 6 mol % MnO 2 , held at 700 °C for 500 h. The competitive reaction reduces the redox chromate formation by consuming the oxygen at the glass/metal interface. In addition, the competitive reaction results in the formation of a continuous Mn–Cr oxide scale at the glass/metal interface, which is helpful for reducing the further diffusion of Cr from metallic interconnect to glass. [ABSTRACT FROM AUTHOR]

The volatile boron from boron-containing sealing materials often reacts with lanthanum-containing cathode, leading to the formation of LaBO 3 and consequently significant degradation of cathode. The reaction between boron-containing sealing glass-ceramics and lanthanum-containing cathode thus presents a challenge for the development of solid oxide fuel cell (SOFC). Here we report for the first time that such a reaction can be significantly reduced by Bi 2 O 3 dopant in sealing glass-ceramics. In particular, the formation of LaBO 3 can be prohibited in reaction couple between glass containing 9 mol.% Bi 2 O 3 and lanthanum strontium cobalt ferrite (LSCF) cathode. The addition of Bi 2 O 3 enhances the [BO 3 ] → [BO 4 ] transition in glass structure and therefore improves the thermal stability of boron species in glass matrix. In addition, Bi 2 O 3 dopant also favors the formation of BiBO 3 , which dramatically reduces boron volatility from sealing glass-ceramics. The reported results provide an effective approach for solving the sealing challenge. [ABSTRACT FROM AUTHOR]

In this paper, the effect on coke formation of adding a Ni 0.75 Fe 0.25 catalyst layer to the anode side of a fuel cell running on methane is investigated. The formation of an intermediate FeNi 3 phase can be observed in catalysts annealed at different temperatures. The catalyst annealed at 705 °C has the smallest calculated surface energy and grain size among all catalysts annealed at different temperatures. In addition, the O 2 -TPO profiles and Raman spectra of spent anode material reveal that the catalyst annealed at 705 °C has the best coke resistance among all catalysts. Moreover, the cell with catalyst layer annealed at 705 °C, under a current density of 600 mA cm −2 at 650 °C, experiences a decrease of 10% after operating in methane for 260 min, which is much more stable than that without catalyst layer (a decrease of 50%). [ABSTRACT FROM AUTHOR]

Abstract: In this paper, Al2O3 was added to CaO–SrO–B2O3–SiO2 sealing system to tailor the structure of sealing glass–ceramics and glass–ceramics/metal interfacial reaction. The addition of alumina in glasses contributes to increasing fraction of bridging oxygen in silica tetrahedral as well as the change in boron environment from three-fold to four-fold (BO4 →BO3). The devitrification tendency of glasses also decreases with increasing Al2O3 content. The condensed glass structure and increasing residual glass content play opposite roles on the interfacial reaction, consequently resulting in a maximum fraction of Cr6+ in reaction couples between Cr2O3 and glass containing 6mole% Al2O3 at 700°C. In addition, the good bonding can be observed at the interface between Cr-containing interconnect (Crofer 22APU) and glass containing 4mole% Al2O3, held at 700°C for 100h. The reported results support the suitability of the prepared glass–ceramics as sealing materials for SOFC applications. [Copyright &y& Elsevier]

In this paper, Ni0.75Fe0.25 catalyst layers with different citric acid contents (molar ratio of CA to metal ions ranges from 0.1 to 1.5) were prepared using thermal decomposition method. Attention was focused on the effect of citric acid on the phase structure, surface energy and coking resistance of Ni0.75Fe0.25 catalyst for solid oxide fuel cells (SOFCs). The FeNi3 phase can be observed in all reduced catalysts, while the grain size of catalysts increases with increasing CA content. The O2-TPO profiles and Raman spectra reveal that the CA1.5 catalyst has the best coking resistance among all catalysts. In addition, the cell with the CA1.5 catalyst layer has a maximum peak power density 271 mW cm−2, when operating at 650 °C in methane. Moreover, the voltage of cell with the CA1.5 catalyst layer still remains 74% of the initial value, after operating in methane for 9 h under a current density of 600 mA cm−2 at 650 °C, which is much more stable than that of the CA-free catalyst layer (53%). [ABSTRACT FROM AUTHOR]

In this paper, TiO2 is added to CaO–SrO–B2O3–SiO2 sealing system to tailor the sealing properties of glass-ceramic seals. The coefficient of thermal expansion (CTE) of quenched glasses and glass-ceramics (held at 750 °C for 100 h) does not change significantly with the addition of TiO2; whereas, the glass stability (ΔT xg = T x − T g) decreases systematically with increasing TiO2. The addition of TiO2 accelerates the crystallization of sealing glasses. The formation of Sr-containing phase, e.g., Sr(TiO3), contributes to the improved chemical compatibility as well as the increase in conductivity of sealing glasses (e.g., from 7.9 × 10− 8 S cm− 1 to 6.9 × 10− 5 S cm− 1 at 800 °C). In addition, the good bonding is observed at the interface between Cr-containing interconnect (430SS) and glasses containing 4–8 mole % TiO2, held at 750 °C for 100 h. [ABSTRACT FROM AUTHOR]