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Nb modified SrFeNiMoNbO (SFNiMNb, x = 0, 0.05, 0.1, and 0.15) materials are synthesized by the one-step combustion method, and their characteristics are investigated. According to the X-ray diffraction (XRD), all samples present single perovskite structures and scanning electron microscope (SEM) results indicate that all samples possess uniform porous structures. Additionally, the electrode conductivity is improved by doping Nb on the B′ site of SFNiM. From the X-ray photoelectron spectroscopy (XPS) results, the ratios of Fe/Fe and Mo/Mo vary with the Nb content, which leads to the conductivity change of SFNiMNb materials. For all the samples, SFNiMNb exhibits the best electrochemical performance with the lowest polarization resistance of 0.11 Ω cm and the highest power density of 1260 mW cm 800 °C in humidified H. The results indicate that SFNiMNb is a promising type of candidate cathode for solid oxide fuel cells. [ABSTRACT FROM AUTHOR]

Flash sintering is novel, innovative, and promising technique for achieving highly dense ceramic materials at low furnace temperature and short sintering time. Herein, flash sintering process was studied by reducing furnace temperature while the electric field applied to samples was kept constant. Further, 8 mol% yttria-stabilized zirconia (8YSZ) samples were sintered by current-limiting flash sintering mode during the occurrence of this flash sintering process. Results showed that the lower the furnace temperature, the longer the time for the onset of flash sintering. However, temperature threshold was observed under certain electric field. Resulting flash sintered 8YSZ samples were characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). SEM images exhibited well-dense microstructures with small grain size. EIS results indicated that the values of conductivity of all 8YSZ samples flash sintered at different furnace temperatures were almost similar, and the conductivity of 8YSZ flash sintered at 565 °C reached 0.056 S cm −1 at 850 °C under the electric field of 300 V cm −1 , which is adequate for solid oxide fuel cells application. [ABSTRACT FROM AUTHOR]

A novel electrical current applied technique known as flash sintering has been applied to rapidly (within 10 min) densify electrolytes including Ce0.8Gd0.2O1.9 ( GDC20), Ce0.9Gd0.1O1.95 ( GDC10), and Ce0.8Sm0.2O1.9 ( SDC20) for application in Solid Oxide Fuel Cells ( SOFCs). The densification temperature for the three electrolytes was 554°C, 635°C, and 667°C, respectively, which is far below conventional sintering temperatures. All specimens after flash sintering maintained the pure fluorite structure and exhibited a well-densified microstructure. To investigate the flash-sintering mechanism, we have applied Joule heating effect with blackbody radiation theory, and found that this theory could reasonably interpret the flash-sintering phenomenon by matching theoretically calculated temperature with the real temperature. More importantly, one of the materials inherent properties, the electronic conductivity, has been found correlated with the onset of flash sintering, which indicates that the electrons and holes are the primary current carriers during the start of flash-sintering process. As a result, potential densification mechanisms have been discussed in terms of spark plasma discharge. [ABSTRACT FROM AUTHOR]

Uniform submicron LaNiO (sm-LNO) powders have been synthesized by a facile polyvinylpyrrolidone (PVP)-assisted hydrothermal route. In the presence of PVP, sm-LNO of pure phase has been obtained by calcination at the relatively low temperature of 900 °C for 8 h. Compared micron-sized LNO (m-LNO) particles obtained at 1,000 °C by hydrothermal synthesis route without PVP assisted, the sm-LNO-PVP displays regularly shaped and well-distributed particles in the range of 0.3-0.5 μm. The scanning electron microscopy (SEM) results showed that the sm-LNO sample is submicronic and that the m-LNO sample shows agglomerates with a broad size distribution. The electrochemical performance of m-LNO and sm-LNO-PVP has been investigated by electrochemical impedance spectroscopy. The polarization resistance of the sm-LNO-PVP cathode reaches a value of 0.40 Ω cm at 750 °C, which is lower than that of m-LNO (0.62 Ω cm). This result indicates that a fine electrode microstructure with submicron particles can help to increase the active sites, accelerate oxygen diffusion, and reduce polarization resistance. An anode-supported single cell with sm-LNO cathode has been fabricated and tested over a temperature range from 650 to 800 °C. The maximum power density of the cell has achieved 834 mW cm at 750 °C. These results therefore show that this PVP-assisted hydrothermal method is an effective approach to construct submicron-structured cathode and enhance the performance of intermediate temperature solid oxide fuel cell. [ABSTRACT FROM AUTHOR]

Compositionally continuously graded cathode layers (CGCLs) of (Ba0.5Sr0.5)(Fe0.91Al0.09)O3−δ –Gd0.1Ce0.9O2 (BSFA–GDC) have been constructed by a handy and effective technique called wet powder spraying (WPS). CGCLs exhibit similar thermal expansion coefficient (TEC) value between adjacent thin layers. The continuously graded structure and the well-distributed components of BSFA–GDC cathode are confirmed by morphological characterization with scanning electron microscopy (SEM), and by compositional analysis with energy dispersion X-ray spectrometer (EDS), respectively. The polarization resistance (R p) of CGCLs with three different thicknesses is investigated by electrochemical impedance spectra (EIS). The EIS results show that CGCLs with a moderate thickness of 20 μm achieve the lowest R p of 0.301 Ω cm2 at 800 °C. In addition, anode-supported single cells with the configuration of NiO–YSZ/YSZ/GDC/BSFA–GDC have been fabricated and tested. The cell with the CGCLs thickness of 20 μm reaches the highest output power density of 848 mW cm−2 at 800 °C. [ABSTRACT FROM AUTHOR]

Abstract: Herein a chemical reduction method is proposed in order to modify the solid oxide fuel cells (SOFC) traditional cathode material La0.8Sr0.2MnO3−x (LSM). Silver nanoparticles were prepared by the reduction of ammoniacal silver nitrate with ascorbic acid in dilute aqueous solutions containing PVP. The obtained LSM–Ag composite powders were characterized by XRD, SEM, EDX, and STEM. The results showed that the LSM–Ag composite powder possess an elaborated fine structure with a homogeneous distribution of Ag and LSM, which effectively shortens the diffusion pathway for electrons and adsorbed oxygen. The electrochemical performance of the LSM–Ag cathode with different Ag loadings was investigated. A cathode loading with 1 wt.% Ag exhibited an area specific resistance as low as 0.45 Ω cm2 at 750 °C, compared to around 1.1 Ω cm2 for a pure LSM electrode. Similarly an anode-supported SOFC with 1 wt.% Ag in the cathode shows a peak power density of 1199 mW cm−1, higher than the value of 717 mW cm−1 achieved for a similar cell with a LSM cathode. Increasing the Ag loading is shown to have an insignificant effect on improving electrocatalytic performance at 750 °C, however it can increase output power at 650 °C. [Copyright &y& Elsevier]

Abstract: A Sr2Fe1.5Mo0.5O6–Sm0.2Ce0.8O1.9 (SFMO–SDC) nanocomposite material has been prepared by the self-combustion method. The phase structure and morphology of the material have been characterized by means of X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). These results show the coexistence of perovskite and fluorite structures within the porous microstructure which are uniformly distributed throughout the prepared samples. The electrochemical performance of the material has been investigated by electrochemical impedance spectroscopy (EIS) measurements. Using an SDC interlayer SFMO–SDC composite cathode is prepared and applied onto a standard YSZ (8% Y2O3-stabilized ZrO2) electrolyte. A low polarization resistance of the prepared sample is obtained and remarkable performance of the SFMO–SDC based IT-SOFCs is achieved. It is demonstrated that the SFMO–SDC/SDC/YSZ/NiO–YSZ fuel cell reached power densities of 2.21, 1.66, 1.16 and 0.71 W cm−2 at 800, 750, 700 and 650 °C, respectively, in humidified H2 (3 vol% H2O). [Copyright &y& Elsevier]

Abstract: Continuously graded anode functional layers (CG-AFLs) were fabricated on the Ni–YSZ anode substrates by electrophoretic co-deposition (EPD) technique. The microstructure and composition of the CG-AFLs were investigated. The result showed that uniform and graded structure in AFL was obtained. The single cells were constructed on the basis of CG-AFLs, with a maximum output power density greater than 1.10Wcm−2 obtained at 800°C for the cell with 9.8μm-thick CG-AFL. Electrochemical impedance spectroscopy (EIS) indicated that the excellent cell performance was contributed to the enlargement of triple phase boundary (TPB) by adding the CG-AFL. [Copyright &y& Elsevier]

The electrocatalytic conversion of ethane to ethylene is an important industrial process since ethylene is useful for the production of various chemical intermediates and polymers. However, this process often requires high temperatures. Metal-oxide heterogeneous interfaces constructed by in-situ exsolved process under reducing conditions would be favorable for promoting the catalyst activity, selectivity, and stability of ethane conversion to ethylene. Herein, Sr 1.95 Fe 1.4 Co 0.1 Mo 0.5 O 6-δ (abbreviated as SFCoM) was prepared as a novel anode material of solid oxide electrolysis cells (SOECs) for green ethylene production by electrochemical oxidative dehydrogenation of ethane. After reduction, nano CoFe particles were in-situ exsolved on SFCoM oxides to form a nano alloy-oxide heterostructure (CoFe@SFCoM) with large numbers of reactive sites, relevant for improving the conversion rate of ethane and the yield of ethylene. At 800 °C, the single cell based on CoFe@SFCoM anode exhibited a current density of 1.89 A cm−2 at 1.6 V with an ethane conversion rate of 36.4% and corresponding ethylene selectivity of 94.5%. After 50 h of testing, the electrolysis current density(∼0.5 A cm−2) and ethylene yield(∼18.43%) of the single cell did not change significantly, showing good stability. In sum, CoFe@SFCoM looks very promising for future use as a SOECs anode for the electro-catalytic conversion of ethane to ethylene. [ABSTRACT FROM AUTHOR]

The performance and stability of direct carbon solid oxide fuel cells (DCSOFCs) are severely affected by the electrocatalytic activity of their anode materials. In this work, a cobalt doped layered perovskite, (PrBa) 0.95 Fe 1.8−x Co x Nb 0.2 O 5+δ (PBFCo x N, x = 0, 0.1, 0.2, 0.3), is investigated as the anode material for a DCSOFC. Co 3 Fe 7 alloy particles are exsolved on the perovskite substrate under the reduction of carbon, which improves CO chemisorption and electrochemical oxidation. This enhances the electrochemical performance of the anode. The electrolyte-supported cell with a (PrBa) 0.95 Fe 1.6 Co 0.2 Nb 0.2 O 5+δ (PBFCo 0.2 N) anode achieves a peak power density of 525.6 mW cm−2 at 800 °C, fueled by activated carbon. The performance of this anode material is comparable to or exceeds that of previously reported anodes, indicating that the PBFCo 0.2 N anode is a promising option for DCSOFCs. • Co 3 Fe 7 nanoparticles can exsolve on the anode in a carbon fuel atmosphere. • Low-valence Co2+ dopant improve the conductivity. • The doping of Co ions can effectively improve the chemical adsorption activity of CO. • High power densities are achieved at 800 ℃ in carbon fuel. [ABSTRACT FROM AUTHOR]

Protonic ceramic fuel cells (PCFCs) have generated significant interest due to their weak temperature dependence and efficient energy conversion. However, traditional cathode materials show poor electrocatalytic activity at a low operating temperature due to their intrinsically slow proton diffusion, which is a long-standing issue that limits the output performance of PCFCs. Herein, the strategy of fluorinating a perovskite cathode is proposed for promoting proton transfer within the bulk of the cathode. This strategy is demonstrated in a fluorinated BaCo 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3−δ (BCFZY) perovskite, which reveals a reduced polarization resistance and enhanced PCFC output performance, superior to those of newly reported PCFCs. Combing the experimental characterization and theoretical calculations, we found that the performance improvement was ascribed to the strong inductive effect of F−, which can increase the polarity the M−O bonding and decrease the O···H interaction, thus boosting the production of protonic defects and increasing the protonic diffusion coefficient. [Display omitted] • Fluorinated BaCo 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3−δ (BCFZY) perovskite is firstly synthesized as PCFC cathode. • Fluorination enhances the hydration properties and proton mobility of BCFZY perovskite. • Fluorination inductive effect has been proposed to reveal the origin of improved proton mobility. • Peak power density of 0.782 W cm−2 is obtained at 600 °C for a single PCFC using fluorinated BCFZY as cathode. [ABSTRACT FROM AUTHOR]

Abstract: BaZr0.1Ce0.7Y0.1Yb0.1O3 (BZCYYb), a promising proton conductor of poor sinterability used in Solid Oxide Fuel Cells (SOFCs), has been densified in one hour at 850 °C by applying direct current sintering technique (DC-sintering). Under a constant electrical field, the current density through the specimen of BZCYYb rises rapidly when the temperature increases to a certain value. In DC-sintering process, we restrict the current density when the sharp increase occurs. By limiting current density to different values for one hour, we find that current density is the most important factor in DC-sintering process. The conductivity and the grain size of BZCYYb electrolyte increase significantly with the enhanced current density, while the different initial applied electrical fields have negligible effect. The stable stage of DC-sintering process can be explained by Joule heating. Corresponding real temperature of specimens is estimated by applying black body radiation theory. [Copyright &y& Elsevier]

Abstract: Nanoporous composite oxides Sr2Fe1.5Mo0.5O6–Sm0.2Ce0.8O1.9 (SFM–SDC) have been prepared by a facile one-step method as cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The SFM–SDC composite materials have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and electrochemical impedance spectroscopy (EIS). The EIS results exhibit that SFM–SDC40 (wt% 60:40) cathode has encouraging electrochemical performance with low polarization resistance (R p) on YSZ (Y2O3-stabilized ZrO2) electrolyte. Subsequently, bi-layer cathodes SDC/SFM–SDC are fabricated, and excellent electrochemical performance of such composite cathodes are observed. We demonstrate that the SDC interlayer significantly decreases the R p of cathode and accelerates the charge transfer process. As a result, the R p of the SDC/SFM–SDC40 bi-layer cathodes is almost 50% less than that of SFM–SDC40 cathode on YSZ electrolyte at 800 °C, and R p is only 0.11 Ω cm2. Compared with single cells without an interlayer, the anode-supported single cells with SDC interlayer exhibit enhancement in overall power performance. [Copyright &y& Elsevier]

Abstract: In order to lower the sintering temperature and shorten firing time, a novel, effective and facile technique has been developed for sintering Yttria-stabilized zirconia (YSZ) electrolyte thin film. Herein this technique, which employs a weak direct current (DC), is used for the first time in the manufacture of the anode-supported solid oxide fuel cell (SOFC). A single cell is directly assembled using a pre-sintered anode/electrolyte and screen printed cathode and subsequently sintered under electric assistance from room temperature to 800 °C at a heating rate of 5 °C min−1. A fully dense YSZ electrolyte film can be observed by scanning electron microscopy (SEM) and the open circuit voltages (OCVs) are in accordance with theoretical values, confirming that the cell possesses a dense YSZ film. Using hydrogen fuel, the maximum power density of this cell was 0.8, 1.1 and 1.4 W cm−2 at 650, 700 and 750 °C, respectively. We believe this DC assisted sintering technique (DC-AST) may not only reduce the cost, but also maintain the anode nanostructure, thus offering a potentially useful manufacturing technique for SOFCs. [Copyright &y& Elsevier]

Abstract: A fully dense Ce0.8Gd0.2O1.9 (gadolinia doped ceria, GDC) is obtained by a novel using a sintering technique for several seconds at 545°C by applying a direct current (DC) electrical field of 70Vcm−1. The onset applied field value of this phenomenon is 20Vcm−1, and the volume specific power dissipation for the onset of flash sintering is about ∼10mWmm−3. Through contrast with the shrinkage strain of the conventional sintering as well as scanning electron microscopy (SEM) analysis, we conclude that GDC specimens are sintered to fully density under various applied fields. In addition, we demonstrate that the grain size of GDC is decreasing with the increase of applied field and the decrease of sintering temperature. Through calculation, we find that sintering of GDC can be explained by the Joule heating from the applied electrical field. [Copyright &y& Elsevier]

A step-wise current-limiting flash sintering process (SCFS process) was proposed to densify La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3-δ (LSGM) electrolyte. Well-densified microstructures of LSGM samples were obtained at 690 °C under an electric field of 100 V cm−1. Compared with the current-limiting flash sintering process, the spike in power dissipation was avoided, the shrinkage rate of LSGM samples was moderate, and the microstructures of LSGM samples were uniform. The conductivity of LSGM samples sintered via SCFS process at 0.9 A for 30 min reached 0.072 S cm−1 at 850 °C, and this was approximately the same as the value of conventionally sintered LSGM samples at 1400 °C for 10 h. These results proved that SCFS process achieved easy controllability, and it is expected that SCFS process can be applied in industry. • SCFS process was proposed for LSGM electrolyte densification. • The well-densified and uniform microstructures of LSGM were obtained. • The spike in power dissipation was avoided in SCFS process. • SCFS process is expected to be applied in industry. [ABSTRACT FROM AUTHOR]

Proton conducting solid oxide fuel cells (H–SOFCs) with BaZr 0·1 Ce 0·7 Y 0·2 O 3-δ as electrolyte were fabricated to couple the removal of nitrogen oxides in power generation technology. Specially, a deliberately designed cathode with the composition of La 0·3 Sr 0·7 Mn 0·8 Mg 0·2 O 3−δ was prepared to realize this dual function. The results indicated that the incorporation of Mg ions in La 0·3 Sr 0·7 MnO 3−δ can improve its ability to adsorb NO and the cathode activity. At 800 °C, when using the NO as oxidant, single cell with La 0·3 Sr 0·7 Mn 0·8 Mg 0·2 O 3−δ cathode was able to obtain peak power density of 48 mW cm−2 and achieve the conversion of NO to N 2 more than 48%. These findings suggested that power generation coupling deNO via H–SOFC is possible and La 0·3 Sr 0·7 Mn 0·8 Mg 0·2 O 3−δ was a promising cathode for this application. [ABSTRACT FROM AUTHOR]

In this study, Nb doped double perovskite oxide (Sr 2 Fe 1.4 Nb 0.1 Mo 0.5 O 6-δ) is prepared and tested as symmetrical electrodes for intermediate temperature solid oxide fuel cells. X-ray diffraction demonstrates that Sr 2 Fe 1.4 Nb 0.1 Mo 0.5 O 6-δ maintains more stable cubic perovskite phase structure than its raw material (Sr 2 Fe 1.5 Mo 0.5 O 6-δ) under reducing atmosphere. X-ray photoelectron spectrometry shows that Nb doping significantly enhances bond strength of Fe O Fe(Nb) so that Fe ion maintains more stable oxidation states after reducing. At 600 °C, Nb doping also increases the conductivity from 17.62 to 27.61 cm−1 in air and from 11.11 S cm−1 to 15.86 S cm−1 in wet hydrogen (∼3% H 2 O). Furthermore, Sr 2 Fe 1.4 Nb 0.1 Mo 0.5 O 6-δ exhibits enhanced electrochemical performances in terms of lower polarization resistance under both oxidizing and reducing atmospheres. Peak power densities of 364.93 and 531.49 mW cm−2 at 750 and 800 °C are obtained based on a single symmetrical cell with Sr 2 Fe 1.4 Nb 0.1 Mo 0.5 O 6-δ electrode, which also shows excellent redox stabilities. All of these results confirm that Sr 2 Fe 1.4 Nb 0.1 Mo 0.5 O 6-δ electrode has promising prospects for the symmetrical intermediate temperature solid oxide fuel cells. [ABSTRACT FROM AUTHOR]

Solid oxide electrolysis cell (SOEC) has great application prospects in the fields of renewable energy storage, CO 2 capture and utilization. One of the key factors hindering the development of SOEC is the lack of suitable cathode materials. In this study, we designed and developed a kind of new micro-nano heterostructure materials Co@Sr 1.95 Fe 1.4 Co 0.1 Mo 0.4 Ti 0.1 O 6-δ (Co@SFCMT), Co nanoparticles uniformly distributed on the SFCMT matrix and provided rich electric catalytic active sites, SFCMT showed excellent oxygen ion transport performance. The synergistic effect of Co nanoparticles and Sr 1.95 Fe 1.4 Co 0.1 Mo 0.4 Ti 0.1 O 6-δ (SFCMT) increased the rate of CO 2 reduction reaction (CO 2 RR). At 1.8 V and 800 °C, the maximum electrolytic current density of the cell with Co@SFCMT as the cathode reached 2.57 A cm−2. In addition, Co@SFCMT showed good stability at 1.5 V and 750 °C, with no performance decay even after 200 h of continuous operation. The micro-nano heterostructure design strategy of perovskite oxides will not only open new avenues for designing SOEC electrodes, but also be expected to promote the development of other energy storage and conversion systems. • A novel heterostructure cathode material for solid oxide electrolysis cell was prepared. • The Co@Sr 1.95 Fe 1.4 Co 0.1 Mo 0.4 Ti 0.1 O 6-δ material exhibited high activity and stability. • Structural stability of the material was regulated by introducing Ti. • No performance decay was observed after 200 h of operation. [ABSTRACT FROM AUTHOR]

In this work we show that the performance of a Sr 2 Fe 1.5 Mo 0.5 O 6 cathode can be improved by scandium substitutional doping. Herein Sr 2 Fe 1.5-x Sc x Mo 0.5 O 6 (SFSc x M) compounds are synthesized with a doping value (x) varying from 0 to 0.2, using a glycine-nitrate combustion progress. The phase structure and morphology are characterized by X-ray powder diffraction and scanning electron microscopy showing a perovskite structure and a porous microstructure when doping between 0 and 0.1. X-ray photoelectron spectroscopy results indicate that the Sc-doping has a clear effect on Fe 2+ /Fe 3+ and Mo 6+ /Mo 5+ ratios. On cells consisting of SFSc x M electrodes and La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3 electrolytes, Sc doping is found to be very effective in reducing the interfacial polarization resistance. Impedance data analysis of SFSc 0.05 M cathode at a variety of oxygen partial pressures indicates that the rate limiting steps are the dissociation of adsorbed molecular oxygen for the high-frequency arc and the migration of oxygen ions to the triple phase boundary for the low-frequency arc, respectively. The highest single cell peak power density is obtained with the SFSc 0.05 M cathode reaching 1.23 W cm −2 at 800 °C. The results suggest that Sc-doping of SFSc x M can substantially improve the electrochemical performance. [ABSTRACT FROM AUTHOR]

Efficient and direct utilization of coal-based fuels is the developmental direction of direct carbon solid oxide fuel cells (DCSOFCs), but their performance is hindered by poor catalytic activity and contaminant poisoning of anode materials. Herein, a Ti-doped double perovskite oxide Sr 2 Fe 1.5 Mo 0.4 Ti 0.1 O 6-δ (SFMT) was developed as the coal-based DCSOFC anode to improve its catalytic activity and resistance to sulfur poisoning. X-ray photoelectron spectroscopy confirms that SFMT shows abundant oxygen vacancy concentration under reducing atmosphere. The as-fabricated DCSOFC with the SFMT anode delivers a maximum power density of 506.5 mW cm−2 at 800 °C when using bituminous coal as the fuel. Electrochemical impedance spectroscopy reveals that Ti doping can effectively promote electrochemical processes on the anode side. Both thermogravimetric analysis and CO temperature-programmed desorption demonstrate that the performance improvement of SFMT is ascribed to its promoted catalytic activity in coal gasification and its increased CO adsorption capacity. The operational period of this coal-based DCSOFC increases from 2 to 10 h after Ti doping, which can be explained by the enhanced structural stability of SFMT under a sulfur-containing environment. Our work may provide some new insight on the design of high-activity anode materials and the understanding of anode reaction mechanisms for coal-based DCSOFCs. [Display omitted] • Sr 2 Fe 1.5 Mo 0.4 Ti 0.1 O 6-δ (SFMT) was designed for a high-efficiency DCSOFC anode. • SFMT shows a stable phase structure under a sulfur-containing atmosphere. • Ti-doping promotes the electrochemical oxidation of C/CO and the adsorption of CO. • SFMT-based DCSOFC reaches a power density of 506.5 mW cm−2 with coal as fuel. [ABSTRACT FROM AUTHOR]

Solid oxide electrolytic cells (SOEC) have great potential in CO 2 conversion and energy storage. However, commercial application of SOEC is still challenging due to the sluggish rate of CO 2 electrochemical reduction caused by the arduous activation and limited CO 2 adsorption on cathode surface. In this study, synergetic regulation strategy on intrinsic catalysis activity and surface amelioration is proposed to improve the CO 2 adsorption capacity and increase the adsorption sites. This strategy is demonstrated in a Cu-doped three-dimensional (3D) porous Sr 2 Fe 1 · 3 Cu 0 · 2 Mo 0 · 5 O 6−δ (SFCuM) nanotube cathode. The results indicate that SFCuM nanotube shows more oxygen vacancies and excellent oxygen ion conduction. At the same time, the nanostructure provides a larger three-phase reaction interface and more reaction sites for CO 2 reduction reaction (CO 2 RR). Benefiting from these merits, the maximum electrolytic current density of the designed SFCuM electrode can be improved to 1.68 A cm−2 at 750 °C and the related polarization resistance can be lowered to 0.59 Ω cm2. In addition, the porous SFCuM nanotube electrode also showed good stability at a constant electrolytic voltage of 1.5 V, with no performance decay during continuous 200-h operation. Such a synergetic regulation strategy may provide some new insight on catalyst design and modification for high-activity CO 2 RR electrode. [Display omitted] • 3D porous SFCuM nanotube cathode has been constructed for efficient CO 2 RR. • SFCuM exhibits more oxygen vacancies and excellent oxygen ion conduction. • SFCuM nanotube provides more reaction sites for the CO 2 adsorption. • The maximum electrolytic current density can be improved to 1.68 A cm−2 at 750 °C. [ABSTRACT FROM AUTHOR]

In this paper, the partial substitution of atomic elements from the A site of a perovskite is investigated in order to develop cathode materials for solid oxide fuel cell (SOFC) applications. Herein, Sr 2−x Ca x Fe 1.5 Mo 0.5 O 6−δ (SCFM), compounds were investigated by characterizing structural properties, chemical compatibility, electrical properties, electrochemical performance and stability. Thermal expansion coefficients were found to decrease when increasing the Ca content. X-ray photoelectron spectroscopy analysis suggests that Ca doping significantly affects the Fe 2+ /Fe 3+ and Mo 6+ /Mo 5+ ratios. For a doping level of x = 0.4, the sample showed the lowest interface polarization ( R p ), the highest conductivity and a maximum power density of 1.26 W cm −2 at 800 °C. These results suggest that SCFM cathode materials are excellent candidates for intermediate temperature solid oxide fuel cells applications. [ABSTRACT FROM AUTHOR]

Engineering of A-site deficiency in perovskites can be critical for designing new materials with required functional properties. In this article, A-site deficient Sr 2-x Fe 1.4 Ni 0.1 Mo 0.5 O 6-δ (x = 0-0.1, Sr 2-x FNM) perovskites have been synthesized and characterized as anode materials for solid oxide fuel cells. X-ray photoelectron spectroscopy data indicate that Sr deficiency changes valence states of B-site cations. The introduction of A-site deficiency has shown to improve the chemical stability of the as-prepared materials under reducing conditions. With increasing of Sr deficiency, the conductivity in 5% H 2 /Ar increases markedly, reaching a peak value of 26.6 S cm −1 at x = 0.05. While further increasing of x reduces the conductivity by affecting the mobility of electronic charge carriers. The La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3 electrolyte-supported cell with La 0.6 Sr 0.4 Fe 0.8 Co 0.2 O 3 cathode and Sr 1.95 Fe 1.4 Ni 0.1 Mo 0.5 O 6-δ anode demonstrates a maximum power density of 606 mW cm −2 at 800 °C operating in H 2 . Such designed A-site deficiency perovskite has the potential to be applied as SOFC anode materials. [ABSTRACT FROM AUTHOR]

La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3-δ (LSGM), a promising electrolyte material for intermediate temperature solid oxide fuel cells, can be sintered to a fully dense state by a flash-sintering technique. In this work, LSGM is sintered by the current-limiting flash-sintering process at 690 °C under an electric field of 100 V cm −1 , in comparison with up to 1400 °C or even higher temperature in conventional furnace sintering. The resultant LSGM samples are investigated by scanning electron microscopy, X-ray diffraction, and electrochemical impedance spectroscopy. The SEM images exhibit well-densified microstructures while XRD results show that the perovskite structure after flash-sintering does not changed. EIS results show that the conductivity of LSGM sintered by the current-limiting flash-sintering process increases with sintering current density value. The conductivity of samples sintered at 120 mA mm −2 reaches 0.049 σ cm −1 at 800 °C, which is approximate to the value of conventional sintered LSGM samples at 1400 °C. Additionally, the flash-sintering process is interpreted by Joule heating theory. Therefore, the current-limiting flash-sintering technique is proved to be an energy-efficient and eligible approach for the densification of LSGM and other materials requiring high sintering temperature. [ABSTRACT FROM AUTHOR]

In this paper, Sr 2 Fe 1.5 Mo 0.4 Nb 0.1 O 6−δ (SFMNb)−xSm 0.2 Ce 0.8 O 2−δ (SDC) (x = 0, 20, 30, 40, 50 wt%) composite cathode materials were synthesized by a one-pot combustion method to improve the electrochemical performance of SFMNb cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). The fabrication of composite cathodes by adding SDC to SFMNb is conducive to providing extended electrochemical reaction zones for oxygen reduction reactions (ORR). X-ray diffraction (XRD) demonstrates that SFMNb is chemically compatible with SDC electrolytes at temperature up to 1100 °C. Scanning electron microscope (SEM) indicates that the SFMNb-SDC composite cathodes have a porous network nanostructure as well as the single phase SFMNb. The conductivity and thermal expansion coefficient of the composite cathodes decrease with the increased content of SDC, while the electrochemical impedance spectra (EIS) exhibits that SFMNb-40SDC composite cathode has optimal electrochemical performance with low polarization resistance ( R p ) on the La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3 electrolyte. The R p of the SFMNb-40SDC composite cathode is about 0.047 Ω cm 2 at 800 °C in air. A single cell with SFMNb-40SDC cathode also displays favorable discharge performance, whose maximum power density is 1.22 W cm −2 at 800 °C. All results indicate that SFMNb-40SDC composite material is a promising cathode candidate for IT-SOFCs. [ABSTRACT FROM AUTHOR]

Nanoscale oxide Ce 0.5 Zr 0.5 O 2 powder has been prepared by a microwave combustion method as the anode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The Ce 0.5 Zr 0.5 O 2 material has been characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) and the BET method. The NiO–Ce 0.5 Zr 0.5 O 2 anode-supported cells are prepared by phase inversion technique and YSZ electrolyte thin film is obtained by dip-coating. The dual-pore structure anode and dense electrolyte are observed by SEM after co-firing process. Excellent electrochemical performance of single cell is demonstrated operating on hydrogen (3% H 2 O), exhibiting the maximum power densities of 218, 342 and 508 mW cm −2 at 700, 750 and 800 °C, respectively. In addition, NiO–Ce 0.5 Zr 0.5 O 2 anode possess high resistance to carbon deposition, indicating which could be promising candidate anodes for direct hydrocarbon SOFCs. [ABSTRACT FROM AUTHOR]

The ability to directly utilize hydrocarbons and other renewable liquid fuels is one of the most important issues affecting the large scale deployment of solid oxide fuel cells (SOFCs). Herein we designed La 0.2 Sr 0.7 TiO 3 –Ni/YSZ functional gradient anode (FGA) supported SOFCs, prepared with a co-tape casting method and sintered using the field assisted sintering technique (FAST). Through SEM observations, it was confirmed that the FGA structure was achieved and well maintained after the FAST process. Distortion and delamination which usually results after conventional sintering was successfully avoided. The La 0.2 Sr 0.7 TiO 3 –Ni/YSZ FGA supported SOFCs showed a maximum power density of 600 mW cm −2 at 750 °C, and was stable for 70 h in CH 4 . No carbon deposition was detected using Raman spectroscopy. These results confirm the potential coke resistance of La 0.2 Sr 0.7 TiO 3 –Ni/YSZ FGA supported SOFCs. [ABSTRACT FROM AUTHOR]

In this paper, niobium doping is evaluated as a means of enhancing the electrochemical performance of a Sr 2 Fe 1.5 Mo 0.5 O 6− δ (SFM) perovskite structure cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs) applications. As the radius of Nb approximates that of Mo and exhibits +4/+5 mixed valences, its substitution is expected to improve material performance. A series of Sr 2 Fe 1.5 Mo 0.5− x Nb x O 6− δ ( x = 0.05, 0.10, 0.15, 0.20) cathode materials are prepared and the phase structure, chemical compatibility, microstructure, electrical conductivity, polarization resistance and power generation are systematically characterized. Among the series of samples, Sr 2 Fe 1.5 Mo 0.4 Nb 0.10 O 6− δ (SFMNb 0.10 ) exhibits the highest conductivity value of 30 S cm −1 at 550 °C, and the lowest area specific resistance of 0.068 Ω cm 2 at 800 °C. Furthermore, an anode-supported single cell incorporating a SFMNb 0.10 cathode presents a maximum power density of 1102 mW cm −2 at 800 °C. Furthermore no obvious performance degradation is observed over 15 h at 750 °C with wet H 2 (3% H 2 O) as fuel and ambient air as the oxidant. These results demonstrate that SFMNb shows great promise as a novel cathode material for IT-SOFCs. [ABSTRACT FROM AUTHOR]

Hybrid direct carbon fuel cells (HDCFCs) present its inherent and unparalleled advantages in converting chemical energy from organic waste, biomass, and coal directly into clean energy with high efficiency. However, the progress of HDCFC technology continues to be hampered by the sluggish anode reaction kinetics. Herein, an effective design strategy for HDCFC anode is proposed, a Cu-modified Sr 2 Fe 1.3 Cu 0.2 Mo 0.5 O 6-δ (SFCM) perovskite oxide is developed to meet the requirements of intermediate-temperature HDCFC anode. The Cu-doping SFCM anode demonstrates excellent redox structural stability and catalytic activity. In addition, the electrolyte-supported single cell with Cu-doping SFCM anode has improved the peak power density from 285.5 mW cm−2 to 489.3 mW cm−2 at 800 °C with activated carbon as the fuel. The significantly enhanced anode catalytic activity is primarily due to the improved interfacial activity and chemical adsorption of CO. Therefore, the present work shows an effective strategy for designing and developing novel high-performance HDCFCs anode materials. • The anode exhibits strong chemical stability under fuel cell operating conditions. • Low-valence Cu2+ dopant increase the conductivity by 1.7 times. • The doping of Cu ions can effectively improve the chemical adsorption activity of CO. • High power densities are achieved at 800 °C in solid-state carbon fuel. [ABSTRACT FROM AUTHOR]

Abstract: La3Ni2O7 oxide has been synthesized by a facile sol–gel method using a nonionic surfactant (EO)106(PO)70(EO)106 tri-block copolymer (Pluronic F127) as the chelating agent. The pure phase of La3Ni2O7 has been obtained by sintering at temperatures of 1100°C for 12h. La3Ni2O7 oxide as a cathode presents no visible reaction with an Y2O3-stabilized ZrO2 (YSZ) electrolyte. The electrochemical performance of the prepared oxide as a cathode has been investigated. Area specific resistance of La3Ni2O7 material on YSZ electrolyte is as low as 0.39Ωcm2 at 750°C. Furthermore, an anode-supported single-cell configuration of NiO–YSZ/YSZ/La3Ni2O7 has been achieved a maximum power density of 848mWcm−2 at 750°C. The cell performance was stable under a constant current of 0.6Acm−2 for over 30h at 750°C. These results therefore suggest that La3Ni2O7 synthesized by this sol–gel method is a highly promising cathode material for applications in IT-SOFCs. [Copyright &y& Elsevier]

• Sr 1.95 Fe 1.4 Co 0.1 Mo 0.5 O 6- δ (SFCoM) is firstly evaluated as SOFC anode. • The electrocatalytic oxidation activity is greatly enhanced by the in situ exsolved Co nanoparticle. • Co@SFCoM anode exhibits excellent catalytic activity and carbon-deposition resistance. • Co@SFCoM is a promising anode material for SOFC. The development of high-catalytic-activity anode materials with carbon tolerance is an important research undertaking for the successful application of intermediate-temperature solid oxide fuel cells (IT-SOFCs). Herein, a novel anode material capable of in-situ exsolution of nanoparticles, Sr 1.95 Fe 1.4 Co 0.1 Mo 0.5 O 6- δ (SFCoM), is designed and prepared from perovskite by a strategy combining A-site defect regulation and B-site doping. The electrocatalytic activity is greatly enhanced by the in-situ exsolved Co nanoparticle. The maximum power densities of a single cell with Co@SFCoM as the anode are 1.01 and 0.79 W cm−2 when H 2 and C 3 H 8 , respectively, are used as the fuel at 750 °C. In addition, the Co@SFCoM anode exhibits excellent carbon-deposition resistance due to the synergistic effect of the Co nanoparticles and perovskite backbone. When C 3 H 8 is used as the fuel, the anode material long-term operational stability over 200 h without performance degradation. Thus, our methodology represents a promising material design strategy for developing high-performance IT-SOFC anodes. [ABSTRACT FROM AUTHOR]

Tubular Solid Oxide Fuel Cells (TSOFCs) owns plenty of merits not only these of common SOFCs but also some merits including rapid start-up, less sealing requirements which stimulate more and more attempts at the commercialization. This review presents the current status of TSOFCs technology including materials, manufacturing, cell design and system integration. Particularly the route of cell design and diversified applications in the last decades are mainly discussed with the purpose of providing a broad overview of this technology for the new to this field. Moreover, a mini summery displays several power generation devices based on TSOFCs manufactured and demonstrated by research institutes and companies around the world. Image 1 • Recent progress of tubular solid oxide fuel cells is reviewed. • The system integration is emphatically introduced. • First time the current commercialization is traced and summarized. • Urgent problems for the development of tubular solid oxide fuel cells. [ABSTRACT FROM AUTHOR]

The development of cathode materials, with high catalytic activity toward oxygen reduction reaction (ORR), structural stability and CO 2 tolerance, is an important research direction for the successful realization of intermediate-temperature solid oxide fuel cells (IT-SOFCs). Herein, a novel double perovskite mixed ionic conductor, i.e., Sr 2 Fe 1.3 Ga 0.2 Mo 0.5 O 6-δ (SFGM), is developed by Ga-doping at Fe-sites of Sr 2 Fe 1.5 Mo 0.5 O 6-δ (SFM) and evaluated as a cathode material in IT-SOFCs. At 750 °C, the area specific resistance (ASR) of SFGM cathode is found to be 0.099 Ω cm2, which is ~50% lower than SFM cathode (0.224 Ω cm2) in 20% O 2 /N 2 atmosphere. Moreover, SFGM exhibits outstanding CO 2 tolerance due to its excellent CO 2 adsorption resistance compared with SFM. The ASR of SFGM remains stable at ~0.13 Ω cm2 during 100 h of continuous operation in 5% CO 2 -containing air. In addition, a large-sized SFGM cathode (30 cm2) is utilized in anode-supported flat-tube SOFCs to demonstrate the potential of SFGM in practical applications. At 750 °C, the as-prepared SFGM-based single-cell provides a stable power of 12 W for 291 h in 5% CO 2 -containing air. The superior electrochemical performance and outstanding CO 2 tolerance of SFGM are promising features for the rapid development of IT-SOFCs. Image 1 • SFGM are firstly evaluated as the cathode for flat tubular solid oxide fuel cell. • Ga-doping enhanced the oxygen-ion transport capability of SFM-based materials. • A low polarization resistance of 0.099 Ω cm2 at 750 °C for SFGM cathode. • SFGM exhibits outstanding CO 2 tolerance. [ABSTRACT FROM AUTHOR]