•Sc-doped titanate cathode shows high performance for CO2 electrolysis.•Improved ionic conductivity is achieved with Sc doping in titanate.•Promising electrode polarizations and Faradic efficiencies are obtained.Perovskite oxide (La,Sr)TiO3+δ (LSTO) cathode has demonstrated promising performance for direct CO2 electrolysis due to its unique redox-stable properties. However, insufficient electro-catalytic activity of titanate remains a major drawback that limits electrode performance. In this paper, catalytically active scandium is doped to LSTO to enhance cathode performances. The structure, electronic conductivity and ionic conductivity of La0.2Sr0.8Ti1−xScxO3+δ (LSTSxO) (x = 0, 0.05 and 0.1) are investigated and further correlated with electrode performances. XRD, TEM, TGA and XPS indicate the successful partial replacement of Ti by Sc in the B site of titanate. The improved electrode performances are strongly dependent on scandium doping contents. Promising direct CO2 electrolysis performance is demonstrated with near 100% current efficiency based on La0.2Sr0.8Ti0.9Sc0.1O3+δ at 1.7 V and 800 °C.

A new dynamics model describing the time-dependent change of solid–liquid interfacial tension is first established to explain the driving force and physical essence of the spreading process of reaction-limited wetting. The model has been successfully verified through the wetting experiments of Al–Si/SiC systems (Si content = 0, 7, 12 wt%, respectively) at different temperatures, in which the logarithmic plots of driving force versus time present a linear relationship in the reaction-limited spreading stage. Furthermore, the mechanisms of reactive spreading are discussed in detail.

A new dynamics model describing the time-dependent change of solid–liquid interfacial tension is first established to explain the driving force and physical essence of the spreading process of reaction-limited wetting. The model has been successfully verified through the wetting experiments of Al–Si/SiC systems (Si content = 0, 7, 12 wt%, respectively) at different temperatures, in which the logarithmic plots of driving force versus time present a linear relationship in the reaction-limited spreading stage. Furthermore, the mechanisms of reactive spreading are discussed in detail.

In this study, hydrothermal carbonization (HTC) was applied for surface functionalization of carbon nanotubes (CNTs) in the presence of glucose and urea. The HTC process allowed the deposition of thin nitrogen-doped carbon layers on the surface of the CNTs. By controlling the ratio of glucose to urea, nitrogen contents of up to 1.7 wt% were achieved. The nitrogen-doped carbon nanotube-supported Pd catalysts exhibited superior electrochemical activity for ethanol oxidation relative to the pristine CNTs. Importantly, a 1.5-fold increase in the specific activity was observed for the Pd/HTC-N1.67%CNTs relative to the catalyst without nitrogen doping (Pd/HTC-CNTs). Further experiments indicated that the introduction of nitrogen species on the surface of the CNTs improved the Pd(0) loading and increased the binding energy.

Bismuth based oxides have excellent ionic conductivity and fast oxygen surface kinetics and show promising potential as highly active electrode materials in solid oxide cells (SOCs) such as solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs). However, the low melting temperature and high activity of bismuth based oxides severely limit their wide applications in SOCs. Herein, we successfully synthesized a 40 wt% Er0.4Bi1.6O3 decorated La0.76Sr0.19MnO3+δ (ESB–LSM) electrode via a new gelation method and directly assembled it on a Ni–yttria-stabilized zirconia (Ni–YSZ) cermet supported YSZ electrolyte cell without the conventional high temperature pre-sintering step. ESB decoration substantially enhances the electrocatalytic activity of the LSM electrode for the oxygen reduction/evolution reactions (ORR/OER). A YSZ electrolyte cell with the directly assembled ESB–LSM electrode exhibits a peak power density of 1.62 W cm−2 at 750 °C, significantly higher than 0.48 and 0.88 W cm−2 obtained on cells with a directly assembled pristine LSM and LSM–YSZ composite electrode, respectively. Most importantly the cells with the directly assembled ESB–LSM oxygen electrodes show excellent stability in SOFC, SOEC and reversible SOC operating modes for over 200 h. The present study demonstrates a significant advancement in the development of bismuth based oxide decorated high performance and stable oxygen electrodes for reversible SOCs.

•Boron poisoning of La-containing cathode can be reduced by Niobium dopant.•Nb2O5 condenses the [SiO4] units and promotes [BO3] → [BO4] transition.•Nb2O5 enhances the formation of boron-containing phases, Ca3B2O6 and CaB2Si2O8.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 Nb2O5 not only condenses the [SiO4] structural units in the glass network, but also promotes the conversion of [BO3] to [BO4]. Moreover, the Nb2O5 dopant enhances the formation of boron-containing phases (Ca3B2O6 and CaB2Si2O8), which significantly reduces the volatility of boron compounds in the sealing glass, suppressing the formation of LaBO3 in the reaction couple between the glass and the cathode. The reported results provide a new approach to solve the problem of boron poisoning.The detrimental reaction between volatile boron species from sealing glass and LSCF cathode can be significantly reduced by Nb2O5 dopant.

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, CeO2-containing glass–ceramics often lack in sufficient electrical resistance, due to the formation of CeO2 as a conductive phase. Here we report for the first time that the electrical conductivity of CeO2-containing glass–ceramics can be reduced by an order of magnitude with HfO2 dopant. A mechanism on the improved electrical property has also been proposed in terms of the structural change in HfO2-doped glass–ceramics. In addition, the relationship between phase evolution of HfO2-doped glass–ceramics and the change in conductivity with operational time has been systematically investigated. Moreover, HfO2-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.

In spite of the fact that rare earth oxides can improve the sealing properties of glass–ceramics, the electrical stability of these glass–ceramics under Solid Oxide Fuel Cell (SOFC) operational conditions still remains ambiguous. In this work, the electrical stability of glass–ceramics doped with La2O3 or CeO2 under SOFC operational conditions has been systematically investigated. The glass–ceramic material with La2O3 dopant exhibits good electrical stability under SOFC operational conditions; whereas, a decrease in the conductivity of the CeO2-containing glass–ceramic material can be related to the formation of a conductive phase, i.e., CeO2. In particular, the relationship between the phase evolution and the change in conductivity of glass–ceramics has been clearly demonstrated. Moreover, the sealing glass–ceramics show good chemical compatibility with 8 mol% yttria-stabilized zirconia (8YSZ) electrolyte, after being held at 750 °C for 1000 hours. The reported results support the suitability of La2O3-containing glass–ceramic as a sealing material for SOFC applications.

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 La2O3 can significantly reduce the boron volatility from sealing glass-ceramics and consequently the formation of LaBO3 in reaction couple between glass and (La,Sr)(Co,Fe)O3 (LSCF) cathode. In particular, the boron volatility can be reduced by about 6 times with the addition of 4 mol.% La2O3 (3.7 × 10−3 vs. 0.6 × 10−3%). The addition of La2O3 condenses the structure of glasses and glass-ceramics, contributing to the decrease in boron volatility from glass-ceramics. In addition, La2O3 dopant favors the formation of boron-containing phase (La5SiBO13) in glass-ceramics, which dramatically reduces the boron volatility. The reported results provide an effective approach for solving the sealing challenge.

•Hydrothermal-prepared RuO2-SnO2 was added to XC-72 carbon black as composite support.•(Ru,Sn)O2 solid solution increases the EAS and specific activity of Pd.•(Ru,Sn)O2 changes the electron structure of Pd 3d and reduces CO coverage on Pd.•(Ru,Sn)O2 solid solution also enhances the OHads adsorption on Pd surface.•Pd/RuO2-SnO2/C catalyst shows highest activity and stability for EG oxidation.In this paper, RuO2-SnO2 binary oxides were prepared using a hydrothermal approach and added to Vulcan XC-72 carbon black as new support material for Pd. The X-ray diffraction, Transmission electron microscopy and X-ray photoelectronic spectra results show that the addition of binary oxides leads to the formation of (Ru,Sn)O2 solid solution in Pd/C catalyst and reduces the particle size of Pd particles due to the anchoring effect. In addition, the electrochemical CO-striping measurement reveals that the Pd/RuO2-SnO2/C catalyst exhibits the largest electrochemical active surface and the best CO tolerance. Moreover, cyclic voltammetry and chronoamperometry tests demonstrate that the Pd/RuO2-SnO2/C catalyst possesses a much higher specific activity (4.4 mA cm−2) than that of the Pd/C catalyst (3.2 mA cm−2) towards ethylene glycol electrooxidation in alkaline media, and better stability as well. These results support the suitability of Pd/RuO2-SnO2/C catalyst developed in this work as a promising candidate for direct alcohol fuel cells (DAFCs) application.

•Thermal-decomposed CaSiO3 was added to XC-72 carbon black as composite support.•Modified electronic structure of Pd facilitates the detachment of CO from Pd surface.•CaSiO3 enhances proton transfer process and improves dehydrogenation process.•CaSiO3 promotes oxidation removal of CO due to easier OH adsorption on electrode.•Pd/50CaSiO3/C catalyst shows highest activity and stability for ethanol oxidation.In this paper, CaSiO3 was prepared using a thermal decomposition approach and added to Vulcan XC-72 carbon black as support material. The X-ray diffraction and Transmission electron microscopy results show that the addition of CaSiO3 does not significantly change the particle size and distribution of Pd nanoparticles. The X-ray photoelectron spectroscopy reveals the interaction between Pd and CaSiO3. In addition, the electrochemical CO-striping measurement reveals that the Pd/50CaSiO3/C catalyst exhibits the largest electrochemical active surface and best CO tolerance. Moreover, cyclic voltammetry and chronoamperometry tests demonstrate that the Pd supported by CaSiO3 and C (50:50 in wt.%) possesses a much higher current density (1408 mA mg−1) than that of the Pd/C catalyst (743 mA mg−1) towards ethanol oxidation in alkaline media, and better stability as well. These results support the suitability of Pd/50CaSiO3/C catalyst developed in this work as a promising candidate for direct ethanol fuel cells application

The interfacial reaction between sealing glasses and Cr-containing interconnects presents a challenge for the development of Solid Oxide Fuel Cells (SOFCs). In this paper, attention was focused on the relationship between the glass structure of HfO2-containing borosilicate glasses and interfacial reaction between glasses and Crofer 22 APU. The results show that HfO2 dissolves in the glass network with the form of Q2 species and condenses the glass structure of borosilicate glasses. In addition, the fraction of Cr6+ in reaction couples between Cr2O3 and glass powders decreases with increasing HfO2 content from 2 to 8 mol%. Moreover, the thickness of reaction zone is about 1 μm for glass with 2 mol% HfO2/Crofer 22 APU, while no obvious reaction zone can be observed in glass with 8 mol% HfO2/Crofer 22 APU. The reported results support the suitability of the prepared glass-ceramics as sealing materials for SOFCs applications.

In this study, the structure–property correlation in the CaO–SrO–ZrO2–B2O3–SiO2 sealing system is systematically investigated. In particular, the effect of ZrO2 on the structure and chemical compatibility of the glasses is clearly demonstrated. The increases in the glass transition temperature and softening temperature of the glasses indicate that the glass structure is condensed by the ZrO2 dopant, which is further confirmed by the 11B and 29Si NMR spectra. Furthermore, the addition of ZrO2 reduces the crystallization tendency of the glasses. The fraction of Cr6+ in the glass/Cr2O3 reaction couple decreases significantly with increasing ZrO2 content at 700 °C because of the condensed glass structure, whereas the fraction of Cr6+ increases with increasing ZrO2 content at 750 and 800 °C. This behavior is related to the increase in residual glass content in the glass–ceramics. Good bondage can be observed at the interfaces between glasses and Crofer 22APU after being held at 800 °C for 500 hours. These results demonstrate the suitability of the Zr-containing glass–ceramics as sealing materials for SOFC applications.

In recent years, the reactive wetting of Ni–Si on graphite has attracted increasing attention. However, most attention has been focused on the effect of Si on the wetting behavior of Ni–Si/C systems. In this work, the wetting process of Ni–Si alloys with different Si content (20, 28, 35, 45 and 55 wt%) on graphite substrates has been investigated at 1523 K in a high vacuum using a modified sessile drop method. The threshold activity of Si in liquid to form SiC at 1523 K can be calculated to be 0.0173, corresponding to a Si content of 33 at% (19 wt%). In addition, a minimum equilibrium contact angle of 20° can be observed in the Ni–45 wt% Si/C system. The adsorption energies of Si at the interface and at the surface of the Ni metal are 5.36 kJ mol−1 and −20.9 kJ mol−1, respectively; whereas, the adsorption energies of Ni at the interface and at the surface of the Si metal are −5.38 kJ mol−1 and 68.9 kJ mol−1, respectively. Moreover, the effects of Si and Ni on the change in the equilibrium contact angle have been evaluated in terms of the solid–liquid interfacial energy and the surface energy of the liquid alloy.

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, (Ca0.9Zn0.03)2(Al0.63Zn0.37)(Si0.69Al0.31)2O7 and Ca2ZnSi2O7, 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, (Ca0.9Zn0.03)2(Al0.63Zn0.37)(Si0.69Al0.31)2O7 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.

Interfacial reactions between a sealing glass–ceramic and electrolyte present a challenge for the development of sealing materials. In this paper, we report for the first time, the interfacial reaction between Hf-containing borosilicate glass–ceramics and 8 mol.% yttria-stabilized zirconia (8YSZ) electrolyte. The results show that the interdiffusion between the glass–ceramics and the 8YSZ can be confined to a ∼2 μm zone at the interface. Additionally, the HfO2 dopant can inhibit the formation of monoclinic ZrO2 and zirconates in the reaction couples of glass–ceramics and 8YSZ, which can be attributed to the Hf-containing phase formation, e.g., Ca6Hf19O44 and Ca3HfSi2O9. Moreover, the formation of the Hf-containing phases contributes to a low conductivity of the glass–ceramics, e.g., 1.9 × 10−7 to 1.6 × 10−6 S cm−1 at 700 °C. These results demonstrate the suitability of the Hf-containing glass–ceramics as sealing materials for SOFC applications.

Borosilicate-based glasses are the most common sealant materials for solid oxide fuel cells (SOFCs). However, boron species vaporizing from glass sealants poison and degrade the electrocatalytic activity of cathodes of SOFCs. In this study, we report the development of a new class of glass sealants based on bismuth and zinc doped borosilicates with significantly suppressed boron volatility. Doping Bi induces the [BO3] → [BO4] transition with an increased binding energy of boron, while addition of Zn leads to the formation of a boron-containing compound, Sr3B2SiO8, with significantly increased stability of boron in the glass matrix. Using La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) perovskite oxide as the cathode to assess the boron deposition and poisoning, the results indicate that the polarization performance of the LSCF cathode for the O2 reduction reaction in the presence of Bi and Zn doped glass is very stable with a negligible change in the microstructure of the electrodes. In contrast, in the case of conventional borosilicate glass, boron preferentially deposits in the electrode/electrolyte region under cathodic polarization, forming primarily LaBO3, disintegrating the perovskite structure and significantly degrading the electrochemical activity of the LSCF cathodes. Doping Bi or Zn remarkably reduces the boron volatility of the glass, thus effectively inhibiting the poisoning of boron species on the microstructure and electrocatalytic activity of SOFC cathodes such as LSCF. The present results demonstrate for the first time that the Bi and Zn doping is the most effective strategy to minimize the boron poisoning from the source by suppressing the boron vaporization of borosilicate-based glass sealant materials.

•The competitive reaction reduces the glass/metal interfacial reaction.•The reaction also results in a stable Mn–Cr oxide scale at the interface.•The Mn–Cr oxide scale acts as diffusion barrier at the glass/metal interface.In this paper, MnO2 is added to CaO–SrO–B2O3–SiO2 sealing system to control the redox glass/metal interfacial reaction in Solid Oxide Fuel Cells. The effect of MnO2 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 Mn2+ ion only; whereas, the Mn3+ content in glasses, held at 600 °C for 9 h, increases with increasing MnO2 dopant. The good bondage can be observed at the interfaces between Crofer 22APU and glass containing 6 mol % MnO2, 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.

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 6 mole% Al2O3 at 700 °C. In addition, the good bonding can be observed at the interface between Cr-containing interconnect (Crofer 22APU) and glass containing 4 mole% Al2O3, held at 700 °C for 100 h. The reported results support the suitability of the prepared glass–ceramics as sealing materials for SOFC applications.

The volatile boron from boron-containing sealing materials often reacts with lanthanum-containing cathode, leading to the formation of LaBO3 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 Bi2O3 dopant in sealing glass-ceramics. In particular, the formation of LaBO3 can be prohibited in reaction couple between glass containing 9 mol.% Bi2O3 and lanthanum strontium cobalt ferrite (LSCF) cathode. The addition of Bi2O3 enhances the [BO3] → [BO4] transition in glass structure and therefore improves the thermal stability of boron species in glass matrix. In addition, Bi2O3 dopant also favors the formation of BiBO3, which dramatically reduces boron volatility from sealing glass-ceramics. The reported results provide an effective approach for solving the sealing challenge.

•The addition of citric acid contributes to the formation of FeNi3 phase.•Phase structure, grain size and surface energy of FeNi3 depend on CA content.•CA1.5 catalyst has the minimum surface energy and thus best coking resistance.•The cell with CA1.5 catalyst layer exhibits good stability in methane.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%).

•An intermediate FeNi3 phase forms in all Ni0.75Fe0.25 catalysts in present work.•The catalyst annealed at 705 °C has smallest calculated surface energy.•The catalyst annealed at 705 °C also exhibits the best coke resistance in methane.•The cell with catalyst layer annealed at 705 °C has the best stability in methane.In this paper, the effect on coke formation of adding a Ni0.75Fe0.25 catalyst layer to the anode side of a fuel cell running on methane is investigated. The formation of an intermediate FeNi3 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 O2-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%).

•The addition of TiO2 accelerates the crystallization of sealing glasses.•Sealing properties of glasses changes with TiO2 dopant due to structural change.•Glass containing 4 mole % TiO2 exhibits best sealing properties.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 (ΔTxg = Tx − Tg) 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.

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.Highlights► Interfacial reaction can be reduced by controlled crystallization of sealing glass. ► Sr-containing crystalline is critical for the chemical stability of sealing glass. ► The improved chemical stability can be explained by thermodynamic models.

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.Highlights► The formation of SrCrO4 was observed in mixtures of SrO-containing sealing glass and Cr2O3 powders. ► Cr2O3 transports from the 430SS to the glass interface, or surface and reacts with O2 to form SrCrO4. ► The effect of the partial pressure of oxygen is modeled by thermochemical calculations. ► The calculations are consistent with the formation of SrCrO4 at interfaces with access to air.

In planar Solid Oxide Fuel Cells (SOFCs), the boron species volatilize from glass seals, and react with lanthanum-containing cathodes (i.e., La0.6Sr0.4Co0.2Fe0.8O3 − δ, LSCF) to form LaBO3 under cathodic polarization, which decomposes the perovskite structure and consequently decreases the electrochemical activity of cathode. In this study, Nb2O5 and Gd2O3 are added to an aluminoborosilicate glass to reduce the boron volatility from glass and the reaction between sealing glass and LSCF cathode. Both Nb2O5 and Gd2O3 doping increases the network connectivity, but Nb2O5 doping enhances the [BO3] → [BO4] 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 Gd2O3-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.

Bismuth based oxides have excellent ionic conductivity and fast oxygen surface kinetics and show promising potential as highly active electrode materials in solid oxide cells (SOCs) such as solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs). However, the low melting temperature and high activity of bismuth based oxides severely limit their wide applications in SOCs. Herein, we successfully synthesized a 40 wt% Er0.4Bi1.6O3 decorated La0.76Sr0.19MnO3+δ (ESB–LSM) electrode via a new gelation method and directly assembled it on a Ni–yttria-stabilized zirconia (Ni–YSZ) cermet supported YSZ electrolyte cell without the conventional high temperature pre-sintering step. ESB decoration substantially enhances the electrocatalytic activity of the LSM electrode for the oxygen reduction/evolution reactions (ORR/OER). A YSZ electrolyte cell with the directly assembled ESB–LSM electrode exhibits a peak power density of 1.62 W cm−2 at 750 °C, significantly higher than 0.48 and 0.88 W cm−2 obtained on cells with a directly assembled pristine LSM and LSM–YSZ composite electrode, respectively. Most importantly the cells with the directly assembled ESB–LSM oxygen electrodes show excellent stability in SOFC, SOEC and reversible SOC operating modes for over 200 h. The present study demonstrates a significant advancement in the development of bismuth based oxide decorated high performance and stable oxygen electrodes for reversible SOCs.

Borosilicate-based glasses are the most common sealant materials for solid oxide fuel cells (SOFCs). However, boron species vaporizing from glass sealants poison and degrade the electrocatalytic activity of cathodes of SOFCs. In this study, we report the development of a new class of glass sealants based on bismuth and zinc doped borosilicates with significantly suppressed boron volatility. Doping Bi induces the [BO3] → [BO4] transition with an increased binding energy of boron, while addition of Zn leads to the formation of a boron-containing compound, Sr3B2SiO8, with significantly increased stability of boron in the glass matrix. Using La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) perovskite oxide as the cathode to assess the boron deposition and poisoning, the results indicate that the polarization performance of the LSCF cathode for the O2 reduction reaction in the presence of Bi and Zn doped glass is very stable with a negligible change in the microstructure of the electrodes. In contrast, in the case of conventional borosilicate glass, boron preferentially deposits in the electrode/electrolyte region under cathodic polarization, forming primarily LaBO3, disintegrating the perovskite structure and significantly degrading the electrochemical activity of the LSCF cathodes. Doping Bi or Zn remarkably reduces the boron volatility of the glass, thus effectively inhibiting the poisoning of boron species on the microstructure and electrocatalytic activity of SOFC cathodes such as LSCF. The present results demonstrate for the first time that the Bi and Zn doping is the most effective strategy to minimize the boron poisoning from the source by suppressing the boron vaporization of borosilicate-based glass sealant materials.