Showing papers by "Zongping Shao published in 2014"
TL;DR: In this paper, a silicon/graphite/amorphous carbon (Si/C) composite with a low silicon content in a core-shell structure has been easily synthesized using a simple method based on spray drying in combination with a subsequent pyrolysis process.
167 citations
TL;DR: In this paper, an ultrathin layer of TiO2 was applied on porous polypropylene (PP) membranes which were used as separators in lithium-ion batteries (LIBs) composed of Li4Ti5O12 (LTO) anode/Li cathode.
116 citations
TL;DR: A facile method for the large-scale synthesis of SnO2 nanocrystal/graphene composites by using coarse metallic Sn particles and cheap graphite oxide (GO) as raw materials is demonstrated.
Abstract: A facile method for the large-scale synthesis of SnO2 nanocrystal/graphene composites by using coarse metallic Sn particles and cheap graphite oxide (GO) as raw materials is demonstrated. This method uses simple ball milling to realize a mechanochemical reaction between Sn particles and GO. After the reaction, the initial coarse Sn particles with sizes of 3-30 μm are converted to SnO2 nanocrystals (approximately 4 nm) while GO is reduced to graphene. Composite with different grinding times (1 h 20 min, 2 h 20 min or 8 h 20 min, abbreviated to 1, 2 or 8 h below) and raw material ratios (Sn:GO, 1:2, 1:1, 2:1, w/w) are investigated by X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy and transmission electron microscopy. The as-prepared SnO2 /graphene composite with a grinding time of 8 h and raw material ratio of 1:1 forms micrometer-sized architected chips composed of composite sheets, and demonstrates a high tap density of 1.53 g cm(-3). By using such composites as anode material for LIBs, a high specific capacity of 891 mA h g(-1) is achieved even after 50 cycles at 100 mA g(-1).
102 citations
TL;DR: This work provides an innovative strategy for the development of new bifunctional electrocatalysts with wide application potentials in high-energy and efficient electrochemical energy storage and conversion.
Abstract: Increasing energy demands have stimulated intense research activities on reversible electrochemical conversion and storage systems with high efficiency, low cost, and environmental benignity. It is highly challenging but desirable to develop efficient bifunctional catalysts for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). A universal and facile method for the development of bifunctional electrocatalysts with outstanding electrocatalytic activity for both the ORR and OER in alkaline medium is reported. A mixture of Pt/C catalyst with superior ORR activity and a perovskite oxide based catalyst with outstanding OER activity was employed in appropriate ratios, and prepared by simple ultrasonic mixing. Nanosized platinum particles with a wide range of platinum to oxide mass ratios was realized easily in this way. The as-formed Pt/C-oxide composites showed better ORR activity than a single Pt/C catalyst and better OER activity than a single oxide to bring about much improved bifunctionality (DE is only approximate to 0.8 V for Pt/C-BSCF; BSCF = Ba0.5Sr0.5Co0.8Fe0.2O3-delta), due to the synergistic effect. The electronic transfer mechanism and the rate-determining step and spillover mechanism were two possible origins of such a synergistic effect. Additionally, the phenomenon was found to be universal, although the best performance could be reached at different platinum to oxide mass ratios for different oxide catalysts. This work thus provides an innovative strategy for the development of new bifunctional electrocatalysts with wide application potentials in high-energy and efficient electrochemical energy storage and conversion.
91 citations
TL;DR: It is demonstrated that a cobalt-free parent oxide BaFeO(3-δ) (BF), which lacks long-range oxygen-ion diffusion paths, has surprisingly high electrocatalytic activity for ORR, and suggests that an undoped BF parent oxide can be used as a high-efficiency catalyst for OrR.
Abstract: The widespread application of solid oxide fuel cell technology requires the development of innovative electrodes with high activity for oxygen reduction reaction (ORR) at intermediate temperatures. Here, we demonstrate that a cobalt-free parent oxide BaFeO3-δ (BF), which lacks long-range oxygen-ion diffusion paths, has surprisingly high electrocatalytic activity for ORR. Both in situ high-temperature X-ray diffraction analysis on room-temperature powder and transmission electron microscopy on quenched powder are applied to investigate the crystal structure of BF. Despite the lack of long oxygen-ion diffusion paths, the easy redox of iron cations as demonstrated by thermal gravimetric analysis (TGA) and oxygen temperature-programmed desorption and the high oxygen vacancy concentration as supported by iodometric titration and TGA benefit the reduction of oxygen to oxygen ions. Moreover, the electrical conductivity relaxation technique in conjunction with a transient thermogravimetric study reveals very high...
90 citations
TL;DR: In this paper, a comprehensive study of oxygen-deficient double perovskites is presented to exploit their potential use as cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs).
Abstract: Here we present a comprehensive study of oxygen-deficient double perovskites PrBa1−xCo2O5+δ (x = 0.00, 0.05, and 0.10) to exploit their potential use as cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Special attention is paid to the structure, oxygen concentration, and oxygen-ion transport properties, which are key factors related to the electrochemical performance. Based on the results obtained from a series of high-resolution structural analysis techniques, such as XRD, SAED, and HR-TEM, these double perovskite oxides possess tetragonal lattice symmetry and a stable crystal structure. According to the information obtained from iodometric titration, TGA, and O2-TPD measurements, an increase in oxygen vacancy concentration in the lattice with an increasing Ba cation deficiency (x value) is demonstrated. Additionally, oxygen permeation flux and electrical conductivity relaxation (ECR) measurements illustrate an improved oxygen ionic conductivity, chemical bulk diffusion coefficient (Dchem) and chemical surface exchange coefficient (Kchem) with the introduction of Ba deficiency, likely due to the increase in the concentration of oxygen vacancies. Tests at 700 °C of the electrochemical performance based on symmetrical cells show area specific resistances (ASRs) of 0.045, 0.041, and 0.036 Ω cm2 for PrBa1−xCo2O5+δ with x = 0.00, 0.05, and 0.10, respectively. These results are extremely promising; consequently, these oxides are worthy of further study and optimization as cathode materials for IT-SOFCs.
87 citations
TL;DR: In this article, a self-assembly mesoporous Zn ferrite microsphere embedded into carbon network has been synthesized by a facile method in the presence of citric acid.
87 citations
TL;DR: In this article, an advanced symmetric solid oxide fuel cells (SOFCs) with a reducible electrode were proposed, where the electrode material La2NiO4 of current cells was reduced under an anode atmosphere to form metallic nickel as a high active catalyst for fuel oxidation.
Abstract: Advanced symmetric solid oxide fuel cells (SOFCs) with a reducible electrode were proposed. Specifically, La2NiO4 + La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) [or Sm0.2Ce0.8O1.9 (SDC)] composite electrodes were successfully fabricated by an infiltration method and tested for power generation. X-ray diffraction (XRD) results demonstrated there was no noticeable phase reaction between infiltrated La2NiO4 and LSGM (or SDC) scaffold, and scanning electron microscopy (SEM) analysis indicated that the La2NiO4 phase formed as nanoparticles that decorated the surface of the scaffold. Different from conventional symmetric SOFCs, the electrode material La2NiO4 of current cells was reduced under an anode atmosphere to form metallic nickel as a high active catalyst for fuel oxidation. After the reduction, the electrode morphology and geometric integrity were maintained for the infiltrated electrode. For thick electrolyte-supported symmetric SOFCs with infiltrated La2NiO4 electrodes, an attractive maximum power density of ∼550 m...
82 citations
TL;DR: In this article, the nano La0.6Ca0.4Fe0.8Ni0.2O3−δ (LCFN) decorated SDC composite oxide, prepared by the solution infiltration method, could function well as a cobalt-free electrode material for “symmetrical” solid oxide fuel cells.
Abstract: Here we report that the nano La0.6Ca0.4Fe0.8Ni0.2O3−δ (LCFN) decorated Sm0.2Ce0.8O1.9 (SDC) composite oxide, prepared by the solution infiltration method, could function well as a cobalt-free electrode material for “symmetrical” solid oxide fuel cells (SOFCs). The structure, morphology, thermal expansion, oxygen reduction reaction activity and catalytic activity for methane oxidation of the as-prepared LCFN-infiltrated SDC electrode was investigated systematically. Under a reducing atmosphere, the partial segregation of metallic nickel from the LCFN perovskite lattice was demonstrated by SEM and STEM-EDX, and the XRD results suggested that the perovskite structure of LCFN still survived. Consequently, the good anode performance was expected due to the high catalytic activity of LCFN for methane oxidation and the excellent electrocatalytic activity of nano nickel for the methane reforming and electro-oxidation of hydrogen. In an air atmosphere, an area specific resistance as low as 0.12 Ω cm2 was achieved at 600 °C. The SDC electrolyte supported “symmetrical” SOFC with the LCFN-infiltrated SDC electrode was then fabricated and tested, which delivered attractive peak power densities of 510 and 350 mW cm−2 at 800 °C, operating on hydrogen and CH4–O2 fuels, respectively.
74 citations
TL;DR: In this article, a hybrid supercapacitor using acti-vated carbon (AC) and mesoporous microspheres is proposed, achieving an energy density of 79.3 Wh kg 1 at a power density of 178.1 W kg 1.
72 citations
TL;DR: The phase structure, surface morphology and roughness of the FeO 3−δ (BLF) thin films are characterized by X-ray diffraction, scanning electron microscopy and atomic force microscopy as discussed by the authors.
TL;DR: In this paper, the authors showed that partial substitution of Co within SrNb0.1Co0.7Fe0.2O3−δ (SNCF0.5) cathode triggers the formation of oxygen non-stoichiometry while preserving the primitive cubic lattice, thus substantially enhancing the ORR performance below 600 °C (relative to the parent compound).
Abstract: Chemical to electrical energy conversion using a solid oxide fuel cell (SOFC) becomes more practical as the operating temperature is lowered to 600 °C and below. Given the thermally activated nature of the oxygen reduction reaction (ORR) at the cathode side, development of cathode catalysts with very low polarisation resistance is essential. Here, we showed that partial substitution of Co within SrNb0.1Co0.9O3−δ by Fe (up to 0.5) triggers the formation of oxygen non-stoichiometry while preserving the primitive cubic lattice, thus substantially enhancing the ORR performance below 600 °C (relative to the parent compound). Close correlation between the oxygen non-stoichiometry and ORR activity trends was found to some extent. SrNb0.1Co0.7Fe0.2O3−δ (SNCF0.2) cathode exhibits a very low area specific resistance value of 0.052 Ω cm2 at 600 °C which translates to superior fuel cell performance, e.g. peak power density of 1587 mW cm−2 at 600 °C. Moreover, the synergistic relationship between ORR activity, thermal expansion coefficient and enhanced CO2 resistance attests to the significance of the SNCF cathode. The last attribute is envisioned as a dominant factor for applications using alternative fuels (e.g. CO which normally contains CO2) and in a portable single-chamber SOFC.
TL;DR: In this article, a new anode catalyst based on a NiFeCu alloy is investigated for use in direct-methane solid oxide fuel cells (SOFCs), and the influence of the conductive copper introduced into the anode catalysts on the performance of the SOFCs is systematically studied.
TL;DR: In this article, mesoporous 3D TiO2/CNT conductive hybrid nanostructures were developed using polyethylene oxide (PEO) to modify the surfaces of carbon nanotubes (CNTs).
TL;DR: Si@C/CNTs&CNFs composites have been successfully synthesized by a serious of high-energy wet ball milling, closed spray drying and subsequently chemical vapor deposition methods.
TL;DR: In this paper, the stability and intrinsic properties of a material are studied combining molecular simulations and experiments on single crystal thin films of barium orthoferrate BaFeO3−δ (BLF).
Abstract: Solid oxide fuel cells (SOFCs) may play a crucial role in solving the energy crisis because they are clean and energy efficient. Finding suitable cathode materials for SOFCs is key to facilitating their widespread use. Besides developing high performance materials, understanding the stability and intrinsic properties of a material is equally important. Herein, Ba0.95La0.05FeO3−δ (BLF) is studied combining molecular simulations and experiments on single crystal thin films. Lattice dynamics simulations are applied to study the stabilization of barium orthoferrate BaFeO3−δ upon doping with La3+. Simulation results reveal the defect energy for substituting one Ba2+ with La3+ in the cubic phase to be lower than that in the monoclinic phase, contributing to its stabilization. Analogous results are also found by doping the Ba site with Sm3+, Gd3+ and Y3+. In addition, the simulation results suggest that the charge compensation mechanism upon doping is filling oxygen vacancies and La3+ tends to trap the mobile oxygen anions. In turn, as the doping level increases the oxygen anion diffusivity decreases, as is also supported by molecular dynamics simulations. In light of this conclusion, single crystal thin films of La3+ slightly doped BaFeO3−δ, BLF, are grown on yttria-stabilized zirconia substrates using pulsed laser deposition. The polarization resistance of the dense film is 0.07 Ω cm2 at 700 °C in an ambient atmosphere, which is comparable to state-of-the-art Co-based materials.
TL;DR: A new class of anode catalyst exemplified by Ni+BaZr0.4Ce0.2O3 with a water storage capability to overcome the persistent problem of carbon deposition is developed, indicating the potential applications of these water storage cermets as catalysts in hydrocarbon reforming and as anodes for SOFCs that operate directly on hydrocarbons.
Abstract: The potential to use ethanol as a fuel places solid oxide fuel cells (SOFCs) as a sustainable technology for clean energy delivery because of the renewable features of ethanol versus hydrogen. In this work, we developed a new class of anode catalyst exemplified by Ni+BaZr0.4Ce0.4Y0.2O3 (Ni+BZCY) with a water storage capability to overcome the persistent problem of carbon deposition. Ni+BZCY performed very well in catalytic efficiency, water storage capability and coking resistance tests. A stable and high power output was well maintained with a peak power density of 750 mW cm(-2) at 750 °C. The SOFC with the new robust anode performed for seven days without any sign of performance decay, whereas SOFCs with conventional anodes failed in less than 2 h because of significant carbon deposition. Our findings indicate the potential applications of these water storage cermets as catalysts in hydrocarbon reforming and as anodes for SOFCs that operate directly on hydrocarbons.
TL;DR: In this article, the authors evaluated BCFSn631 as an oxygen reduction electrode for intermediate-to-low temperature solid oxide fuel cells (SOFCs) and showed that it is in a simple perovskite phase with cubic lattice symmetry.
Abstract: BaCo0.6Fe0.3Sn0.1O3−δ (BCFSn631) is evaluated as an oxygen reduction electrode for intermediate-to-low temperature solid oxide fuel cells (SOFCs). XRD and HR-TEM analysis demonstrate that it is in a simple perovskite phase with cubic lattice symmetry. In situ HT-XRD and ex situ XRD confirm the favorable phase stability of the oxide under a wide range of temperatures and atmospheric oxygen partial pressures. The oxygen nonstoichiometry, electrical conductivity, oxygen reduction activity and electrochemical performance of BCFSn631 are systematically studied through thermogravimetric analysis, electrical conductivity relaxation tests and electrochemical impedance analysis. It has a low thermal expansion coefficient of ∼15.8 × 10−6 K−1 in a temperature range of 25–800 °C and a high oxygen vacancy concentration. Electric conductivity relaxation measurement demonstrates the high oxygen surface exchange and bulk diffusion properties of BCFSn631, comparable to that of the state-of-the-art Ba0.5Sr0.5Co0.8Fe0.2O3−δ electrode. Low area specific resistances are obtained for the BCFSn631 electrode in the intermediate temperature range, determined by electrochemical impedance spectroscopy based on symmetrical cell configuration, suggesting its high activity for oxygen reduction reaction. Peak power densities of 1168, 896, 523 and 273 mW cm−2 are obtained from a fuel cell with BCFSn631 electrode at 600, 550, 500 and 450 °C, respectively. In addition, good long-term performance stability is demonstrated. All these results highly promise BCFSn631 as an excellent oxygen reduction electrode for next generation SOFCs.
TL;DR: In this paper, a tin-doped perovskite oxide, BaCo0.7Fe0.3O3−δ (BCFSn0.1), was used as a promising alternative material for a ceramic oxygen-permeating membrane.
Abstract: In this study, we propose a new tin-doped perovskite oxide, BaCo0.7Fe0.2Sn0.1O3−δ (BCFSn0.1), as a promising alternative material for a ceramic oxygen-permeating membrane. A high energy ball milling-assisted solid-state reaction method is used for the material synthesis. The effect of tin doping on the structure, electrical conductivity, oxygen activity, oxygen bulk diffusivity and surface exchange properties of the materials, sintering behaviour, and oxygen permeability of the related membranes is systematically investigated via transmission electron microscopy (TEM), environmental scanning electron microscopy (E-SEM), thermo-gravimetric analysis (TGA), oxygen temperature-programmed desorption (O2-TPD) and electrical conductivity relaxation (ECR), and oxygen permeation test. The minor substitution of B-site cations in BaCo0.7Fe0.3O3−δ (BCF) with tin is found to be highly effective in improving oxygen flux of the resultant membrane. Under an oxygen gradient created by air/helium, BCFSn0.1 membrane reaches fluxes of 9.62 × 10−7 and 3.55 × 10−7 mol m−2 s−1 Pa−1 [STP], respectively, at 900 and 700 °C, in sharp contrast with the flux values of 4.42 × 10−7 and 2.84 × 10−8 mol m−2 s−1 Pa−1 for BCF membrane with the same thickness of 1 mm. Favorable permeation stability is also demonstrated for the tin-doped membrane, and oxygen bulk diffusion is the main rate-limiting step for oxygen permeation, indicating a further increase in fluxes by reducing the membrane thickness.
TL;DR: In this paper, the phase structure, sinterability, chemical stability and conductivity of BaZr 0.6 M 0.2 O 3− δ (BZMY) compositions with various M cations of Zr 4+, Ce 4+, Pr 3+, Nd 3+, Sm 3+ and Gd 3+ with different ionic radii were comparatively studied.
TL;DR: In this paper, the effects of incorporating Al2O3/SnO2 on the electrical conductivity, morphology, coking resistance and catalytic activity for biogas reforming of the cermet anode are systematically studied.
TL;DR: In this paper, the effects of Nb-doping on the crystal structure, surface morphology, electrical conductivity, chemical bulk diffusion and surface exchange, and oxygen permeability of cobalt-free perovskite-type oxides are systematically investigated using XRD, SEM, and four-probe DC conductivity.
TL;DR: In this paper, the effects of impurity ions on the crystal structure, electrical conductivity, oxygen desorption/permeation behavior, sintering behavior and oxygen reduction activity of BSCF were systematically investigated.
TL;DR: In this article, a 3D core-shell architecture has been fabricated from solution infiltration in combination with high-temperature reactive sintering and evaluated as the oxygen reduction electrode for SOFCs.
Abstract: Solid oxide fuel cells (SOFCs) as alternatives for energy conversion have the capacity to overcome low energy conversion efficiency, highly detrimental emissions from traditional fuel utilization and the limited reserves of fossil fuels crisis. Herein, a 3D core–shell architecture has been fabricated from solution infiltration in combination with high-temperature reactive sintering and evaluated as the oxygen reduction electrode for SOFCs. The resultant electrode is composed of a stable porous Sm0.2Ce0.8O1.9 scaffold as the core for bulk oxygen ion diffusion, and a connective Sm,Ce-doped SrCoO3−δ perovskite film as the shell for efficient oxygen reduction reaction and partial current collection. The significant enhancement in conductivity, chemical and thermal compatibility with such core–shell structured electrodes can deliver promising and stable power outputs. An anode-supported solid oxide fuel cell with such a core–shell structured cathode exhibits a peak power density of 1746 mW cm−2 at 750 °C, which is comparable to the most promising cathodes ever developed. In addition, both a symmetrical cell and a fuel cell demonstrate favourable short-term stability during 200 h operation at 700 °C. The combined strategy involving infiltration and high-temperature reactive sintering (accompanied by ion diffusion) appears to be a promising approach to fabricate cathodes with high electrochemical performance and stability.
TL;DR: In this article, the authors demonstrate that by vacating 2 and 5% of A-site cations from perovskite oxide, a Jahn-Teller distortion with varying extents takes place.
Abstract: The creation of A-site cation defects within a perovskite oxide can substantially alter the structure and properties of its stoichiometric analogue. In this work, we demonstrate that by vacating 2 and 5% of A-site cations from SrNb0.1Co0.9O3−δ (SNC1.00) perovskites (Sr1−sNb0.1Co0.9O3−δ, s = 0.02 and 0.05; denoted as SNC0.98 and SNC0.95, respectively), a Jahn–Teller (JT) distortion with varying extents takes place, leading to the formation of a modified crystal lattice within a the perovskite framework. Electrical conductivity, electrochemical performance, chemical compatibility and microstructure of Sr1−sNb0.1Co0.9O3−δ as cathodes for solid oxide fuel cells were evaluated. Among SNC1.00, SNC0.98 and SNC0.95, SNC0.95 (P4/mmm symmetry (#123)) which exhibits a large JT distortion in conjunction with charge-ordering of cobalt (Co) shows the best oxygen reduction reaction (ORR) activity at low temperature while SNC0.98 (P4mm symmetry (#99)), which displays a local JT distortion, shows the poorest performance.
TL;DR: Amorphous carbon and graphene co-modified LiFePO4 nanocomposite has been synthesized via a facile polyol process in connection with a following thermal treatment.
TL;DR: In this paper, a method to enhance the performance of a yttrium-doped barium cerate proton conductor as an electrolyte for SOFCs through a Pd ingress-egress approach to the development of BaCe0.8Y 0.1Pd0.1O3−δ (BCYP10) was proposed.
TL;DR: In this paper, a freestanding hierarchical SnO2 nanorod/graphene composite film electrode was designed and fabricated by a general route involving electrospinning and film casting processes.
Abstract: A freestanding hierarchical SnO2 nanorod/graphene composite film electrode was designed and fabricated by a general route involving electrospinning and film casting processes. With dual adaptable strategies (hierarchical nanorod structure and graphene “overcoats”), the composite film electrode exhibited enhanced cycling stability.
TL;DR: In this paper, pyridine was used to suppress the coke formation in solid oxide fuel cells (SOFCs) operating on liquid fuels, and the reduction in the CO2 formation rate over the Ni/Al 2 O 3 catalyst is reduced by 64% while a cell power output comparable to that operating on hydrogen is still achieved based on total potential hydrogen available from ethanol.
TL;DR: Porous MgO-CaO-SnOx nanocubes were synthesized to implant firmly and uniformly onto in situ formed carbon paper by a facile route including a template-free growth process and calcining treatment.
Abstract: Porous MgO–CaO–SnOx nanocubes (crystalline SnOx and amorphous MgO/CaO) were synthesized to implant firmly and uniformly onto in situ formed carbon paper by a facile route including a template-free growth process and calcining treatment. Low-cost filter paper was used to realize the part implantation of cubes as well as a source of carbon paper. The mechanistic analysis demonstrates that Mg2+/Ca2+ ions and ammonium hydroxide played important roles in the formation of the cubic phase precursor. This MgO–CaO–SnOx-nanocubes/carbon paper could be directly applied as a binder-free film electrode for lithium-ion batteries eliminating conventional electrode fabrication processes, and an average capacity contribution of ∼719 mA h g−1 for MgO–CaO–SnOx nanocubes through 40 cycles was achieved. The facile synthesis strategy combines the material synthesis, dispersion and electrode fabrication, which further opens a new avenue for the application of nano-architectures in energy storage.