Low temperature deposited (Ce,Gd)O2−x interlayer for La0.6Sr0.4Co0.2Fe0.8O3 cathode based solid oxide fuel cell

Application of La_0.6Sr_0.4Co_0.2Fe_0.8O₃ perovskites cathode in solid oxide fuel cell (SOFC) can benefit from its high electrocatalytic activity at 600-800 °C. However, due to the chemical and mechanical incompatibility between the LSCF cathode and state-of-the-art yttria stabilized zirconia (YSZ) electrolyte, a ceria-based oxide barrier interlayer is usually introduced. In this work, gadolinia doped ceria (GDC) interlayers are prepared by screen printing (SP), electron beam evaporation (EB) and ion assisted deposition (IAD) methods. The microstructures of the GDC interlayers show great dependence on the deposition methods. The 1250 °C-sintered SP interlayer exhibits a porous microstructure. The EB method generates a thin and compact interlayer at a low substrate temperature of 250 °C. With the help of additional energetic argon and oxygen ions bombardment on the deposited species, the IAD method yields the densest GDC interlayer at the same substrate temperature, which leads to the best electrochemical performance of LSFC-based SOFC.     

Investigation on the existence of optimum interlayer distance for H2 uptake using pillared-graphene oxide

In order to prove the existence of an optimum interlayer distance for H₂ uptake, we have obtained H₂ isotherms with respect to the interlayer distance of pillared-graphene oxide (GO) at 1.0 bar and 77 K. Interlayer distances of GO were changed by intercalation of three kinds of diaminoalkanes with a different number of carbon atoms (NH₂(CH₂)_nNH₂, n = 2, 6, 10) as pillars and changing the subsequent thermal annealing conditions. We found an optimum GO interlayer distance for maximum H₂ uptake at 6.3 Å similar to the predicted distance from first-principles calculations for graphitic materials, and the value obtained from thermally modulated GO. Our results experimentally corroborate the existence of an optimum interlayer distance and demonstrate the importance of an interlayer distance for the design of materials for H₂ storage.     

Plasma spray synthesis of La10(SiO4)6O3 as a new electrolyte for intermediate temperature solid oxide fuel cells

The apatite-type lanthanum silicate films were successfully synthesized by modified atmosphere plasma spraying using lanthanum oxide and silicon oxide mixed powders and precalcined hypereutectic powders in the size range 1–3 μm and 5–8 μm, respectively, as starting feedstock materials. The films differed not only in microstructural scale, but also in the characteristic of the degree of film densification. A detail describing the evolution of microstructure has been discussed. A considerable improvement in densification of the La₁₀(SiO₄)₆O₃ electrolyte films has been observed.     

Vertically aligned nanocomposite La0.8Sr0.2MnO3−δ/Zr0.92Y0.08O1.96 thin films as electrode/electrolyte interfacial layer for solid oxide reversible fuel cells

A thin layer with a vertically aligned nanocomposite (VAN) structure of La_0.8Sr_0.2MnO_3−δ (LSM) and Zr_0.92Y_0.08O_1.96 (YSZ) between the oxygen electrode and the electrolyte has been fabricated by a pulsed laser deposition (PLD) technique for solid oxide reversible fuel cells (SORFCs). The high quality epitaxial growth of VAN structured LSM/YSZ has been achieved on single crystal SrTiO₃ substrate at high-deposition temperatures. The symmetric cells with the VAN interlayer are found to have a lower area specific resistance compared to that without the interlayer. The enhancement in performance has been demonstrated by increased oxygen electrode catalytic properties and porous oxygen electrode microstructure. The cell with the VAN interlayer shows an open circuit voltage (OCV) of 1.00 V at 650 °C and maximum power densities of 0.22, 0.32, 0.43 and 0.55 W cm⁻² at 650, 700, 750 and 800 °C, respectively. Compared with the cell without an interlayer, the cells with the interlayer have ∼2 times of the overall maximum power density at the measured temperature range, demonstrating that the VAN interlayer significantly enhances the oxygen electrode performance.     

Reactivity between La(Sr)FeO3 cathode,doped CeO2 interlayer and yttria-stabilized zirconia electrolyte for solid oxide fuel cell applications

Detailed X-ray diffraction (XRD) analysis of two different Sr-doped LaFeO₃ cathodes, YSZ electrolyte and two Sm/Gd-doped CeO₂ interlayer and their mixtures were used to evaluate the formation of undesired secondary reaction compounds. The analysis of room temperature X-ray diffraction data of the mixtures indicates the crystallization of strontium and/or lanthanum zirconates between the cathode and the electrolyte materials and no detected reaction between the cathode and the interlayer materials.     

(Photo) electrochemical investigations on spray deposited n-CdIn 2Se4 thin film/polysulphide/c photoelectrochemical solar cell1

Cadmium indium selenide (n-CdIn ₂Se₄) thin films have been synthesized by spraying the mixture of an equimolar solutions of cadmium chloride [CdCl₂], indium trichloride [InCl₃] and selenourea [(NH₂)₂CSe] in aqueous media onto preheated fluorine doped tin oxide (FTO) coated glass substrates at optimized parameters of substrate temperature and solution concentration. The photoelectrochemical (PEC) cell configuration of n-CdIn₂Se/(l MNaOH + 1 MNa₂S + 1 M S)/C has been used for investigating the current—voltage (I–V) characteristics under dark and white light illumination, photovoltaic output, spectral response, photovoltaic rise and decay characteristics. The PEC study reveals the thin film of CdIn₂Se₄ exhibits n-type conductivity. The junction quality factor in dark (n _d) and light (n _l), series and shunt resistance (R _s and R _sh), fill factor (FF) and efficiency (η) for the cell have been estimated. The observed efficiency and FF of PEC solar cell is found to be 1.95 and 0.37% respectively. Mott-Schottky plot shows the flat-band potential (V _fb) of n-CdIn₂Se₄/(l M NaOH + 1 M Na₂S + 1 M S)/C cell to be—0.655 V/SCE.     

High performance cathode-unsintered solid oxide fuel cell enhanced by porous Bi1.6Er0.4O3 (ESB) interlayer

Dense bismuth oxides stabilized with lanthanide dopants (δ-Bi₂O₃) are always used as interlayer for thin layer GDC (gadolinia-doped ceria) or YSZ (yttria-stabilized zirconia) electrolyte solid oxide fuel cell to improve the cell performance. Dense ESB (Bi_1.6Er_0.4O₃) layer preparation needs special equipment or well synthesized nano-sized powders, which is not friendly for large scale and commercial application. In this paper, anode support unsintered cathode cell with porous ESB interlayer is prepared through simple screen print and its electrochemical performance is tested. No matter sintered or not, porous ESB interlayer lowers both the polarization resistance and ohmic resistance, and enhances cell performance, especially for the ohmic resistance of unsintered cells. The cell with ESB porous interlayer and SSC (Sm_0.5Sr_0.5CoO_3-δ)-ESB unsintered cathode achieves a peak power density of 1.329 W cm^?2 at 700 °C, which is 1.61 times higher than that of the cell without ESB interlayer and 0.93 times higher than that of the sintered cell. However, the durability of porous ESB interlayer enhanced cells is not ideal and it should be improved in further works.     

Photoelectrochemical properties of spray deposited n-ZnIn2Se4 thin films

Zinc indium selenide (ZnIn₂Se₄) thin films have been prepared by spraying a mixture of an equimolar aqueous solution of zinc sulphate (ZnSO₄), indium trichloride (InCl₃), and selenourea (CH₄N₂Se), onto preheated fluorine-doped tin oxide (FTO)-coated glass substrates at optimized conditions of substrate temperature and a solution concentration. The photoelectrochemical (PEC) cell configuration of n-ZnIn₂Se₄/1 M (NaOH+Na₂S+S)/C has been used for studying the current voltage (I–V), spectral response, and capacitance voltage (C–V) characteristics of the films. The PEC study shows that the ZnIn₂Se₄ thin films exhibited n-type conductivity. The junction quality factor in dark (n_d) and light (n_l), series and shunt resistance (R_s and R_sh), fill factor (FF) and efficiency (η) for the cell have been estimated. The measured (FF) and η of the cell are, respectively, found to be 0.435% and 1.47%.     

Properties of bias-assisted sputtered gadolinia-doped ceria interlayers for solid oxide fuel cells

The growth and electrochemical properties of gadolinia-doped ceria (GDC) interlayers deposited by bias-assisted magnetron sputtering in solid oxide fuel cells have been investigated. Such interlayers act as diffusion barriers to protect the yttria-stabilized zirconia electrolyte, preventing possible degradation when mixed ionic-electronic conductor (La,Sr)(Co,Fe)O_3−δ is used as the cathode. The dependence of the applied bias during the sputtering deposition on both the interlayer microstructure and fuel cell performance has been studied in anode-supported single cells. The main experimental results showed that bias-assisted sputtering of GDC interlayers produced microstructures denser than those of unbiased depositions, which resulted in increased electrochemical properties of fuel cells.     

SnPc:C60 bulk heterojunction organic photovoltaic cells with MoO3 interlayer

Infrared sensitive small molecule organic photovoltaic cells were fabricated using a tin (II) phthalocyanine (SnPc) and C₆₀ bulk heterojunction layer. Molybdenum oxide (MoO₃) was used as an interlayer between the ITO anode and light absorbing layers. We found that the short-circuit current of the photovoltaic cells with MoO₃ interlayer was substantially enhanced, resulting in a 45% enhancement in power conversion efficiency. The maximum power conversion efficiency is 1.31% under 1 sun standard AM1.5G solar illumination of 100 mW/cm².     

A note on fast protonic solid state electrochromic device: NiOx/Ta2O5/WO3−x

In the present investigation, the electrochromic properties of a fast protonic solid state device: NiO_x/Ta₂O₅/WO_3−x prepared at room temperature (300 K) is reported. The non-stoichiometric tungsten oxide thin film is prepared by reactive DC magnetron sputtering technique on ITO coated glass; the oxides of tantalum (300 nm) and nickel (100 nm) are prepared by electron beam evaporation. This proton device has a coloration efficiency of 82.4 cm²/C and coloration and bleaching time of 6 and 5 s, respectively, and a transmittance variation of 60%. The work function of WO_3−x thin films by Kelvin probe in uncolored and colored states are 4.73 and 4.30 eV, respectively.     

Surface passivation at a SiO2/n-layer interface

Effects of surface passivation at a SiO₂/phosphorus-doped layer (n⁺-layer) front interface were investigated. Two kinds of cells with different surface concentration were fabricated. Surface potential at the interface was changed by applying bias voltage (V_F). Both open-circuit voltage and short-circuit current of the cell with n⁺-layer concentration of 3 × 10¹⁸ cm⁻³ depended on V_F. Internal quantum efficiency of this cell in short- and medium-wavelength range was changed by applying V_F. It was shown that cell performance was improved by the accumulation of electrons at the interface. To consider the work function difference between a material on the SiO₂ film and the n⁺-layer is important, and cell performance can be further improved by applying V_F to passivate the SiO₂/n⁺-layer interface.     

A highly activated and integrated nanoscale interlayer of cathodes in low-temperature solid oxide fuel cells via precursor-solution electrospray method

This study demonstrates the fabrication of a highly activated and integrated nanoscale interlayer of cathodes in low-temperature solid oxide fuel cells (SOFCs) using the precursor-solution electrospray method. Uniform, crack-free La_0.6Sr_0.4CoO_3−δ (LSC) and LSC-CeO₂ thin-film layers are fabricated by using optimized precursor-solution electrospray and sintering conditions. The LSC–CeO₂ composite layer served as a nanoscale-cathode-functional layer (nCFL) by suppressing grain growth and increasing the number of triple-phase boundaries. The LSC nanoscale-adhesive layer (nAL) played a limited role as an adhesive layer due to a large amount of grain growth and limited triple-phase boundaries. Low-temperature SOFCs with the nAL and nCFL nanoscale interlayers showed maximum power densities of ∼1.108 and 1.150 W cm⁻² at 650 °C, which were ∼13% and 18% higher, respectively, than those of a reference cell without nanoscale interlayers.     

Composition and porosity graded La2−xNiO4+δ (x ≥ 0) interlayers for SOFC: Control of the microstructure via a sol–gel process

We have developed composition and porosity graded La_2−xNiO_4+δ (x ≥ 0) cathode interlayers for low-temperature solid oxide fuel cell that exhibit good adhesion with the electrolyte, controlled porosity and grain size and good electrochemical behaviour. La_2−xNiO_4+δ (x ≥ 0) monolayers are elaborated from a derived sol–gel method using nitrate salts, acetylacetone and hexamethylenetetramine in acetic acid. As a function of the organic concentration and the molar ratio of lanthanum to nickel, these layers present platelets or spherical shape grains with a size distribution ranging from 50 to 200 nm, as verified by SEM-FEG. On the basis of this processing protocol, we prepared porosity and composition graded lanthanum nickelates interlayers with effective control of the pore distribution, the nanocrystalline phase, the thickness and the subsequent electrochemical properties.     

Nonpremixed ignition of C7–C16 normal alkanes in stagnating liquid pool

The nonpremixed ignition temperatures of n-decane, n-dodecane, and n-hexadecane were measured in a liquid pool by heated stagnating oxidizing flow at atmospheric pressure. Together with previous results on n-heptane, it is shown that, for the C₇–C₁₆n-alkanes, the nonpremixed ignition temperature increases monotonically with increasing carbon number, and as such is contrary to the behavior of homogeneous ignition delays. Numerical simulation of the ignition events for n-heptane, n-decane and n-dodecane, employing a recently developed high temperature kinetic model, showed good agreement with the experimental results both qualitatively and quantitatively. Sensitivity and computational analyses indicate that the reason for the higher ignition temperature with increasing fuel molecular size is mostly due to their progressively reduced diffusivity, which leads to correspondingly reduced fuel concentration in the ignition kernel.     

Optical properties of sol–gel deposited Al2O3 films

Highly transparent, uniform and corrosion resistant Al₂O₃ films were prepared on stainless-steel and quartz substrates by the sol–gel process from stable coating solutions using aluminum-sec-butoxide, Al(OBu^s)₃ as precursor, acetylacetone, AcAcH as chelating agent and nitric acid, HNO₃, as catalyzer. Films up to 1000 nm thick were prepared by multiple spin coating deposition, and were characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), optical spectroscopy and micro Vickers hardness test. XRD of the film heat treated at 400°C showed that they had an amorphous structure. XPS confirmed that they were stoichiometric Al₂O₃. The refractive index (n) and extinction coefficient (k) were found to be n=1.56±0.01 and k=0.003±0.0002 at 600 nm, respectively. The surface microhardness and corrosion resistance investigations showed that Al₂O₃ films improved the surface properties of stainless-steel substrates.     

LaNbO4 toughened NiO–Y2O3 stabilized ZrO2 composite for the anode support of planar solid oxide fuel cells

NiO–Y₂O₃ stabilized ZrO₂ (YSZ) composite is the state-of-the-art material for the anode support of planar solid oxide fuel cells (SOFCs). To improve its fracture toughness (K_C), lanthanum orthoniobate LaNbO₄ is synthesized by the method of solid state reaction and added to the mixture of YSZ and NiO at the weight ratio of 47:53. The content of LaNbO₄ in the composite is in the range between 5 and 30 wt%. The microstructure of the composites is examined by scanning electron microscopy (SEM); and the chemical compatibility among the components is evaluated by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS). Vickers hardness test is performed for estimating the K_C of the composites. The results indicate that the K_C increases with the addition of LaNbO₄ in the composites; and the toughening effect is associated with the grain-refinement in the composite and the domain switch in the monoclinic LaNbO₄.     

Combustion synthesis and properties of highly phase-pure perovskite electrolyte Co-doped La0.9Sr0.1Ga0.8Mg0.2O2.85 for IT-SOFCs

The highly phase-pure perovskite electrolyte, La_0.9Sr_0.1Ga_0.8Mg_0.115Co_0.085O_2.85 (LSGMCO), was prepared by means of glycine–nitrate process (GNP) for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The perovskite phase evolution, sintering, electrical conductivity and electrochemical performance of LSGMCO were investigated. The results show that the highly phase-pure perovskite electrolyte LSGMCO can be obtained after calcining at 1150 °C. The sample sintered at 1450 °C for 20 h in air exhibited a better sinterability, and the relative density of LSGMCO was higher than 95%. The stoichiometric indexes of the elements in the sintered sample LSGMCO determined experimentally by EDS were in good agreement with the nominal composition. The electrical conductivities of the sample were 0.094 and 0.124 S· cm⁻¹ at 800 °C and 850 °C in air, respectively. The ionic conduction of the sample was dominant at high temperature with the higher activation energies. While at lower temperature the electron hole conduction was predominated with the lower activation energies. The maximum power densities of the single cell fabricated with LSGMCO electrolyte with Ce_0.8Sm_0.2O_1.9 (SDC) interlayer, SmBaCo₂O_5+x cathode and NiO/SDC anode achieved 643 and 802 mW cm⁻² at 800 °C and 850 °C, respectively.     

Stable, easily sintered BaCe0.5Zr0.3Y0.16Zn0.04O3−δ electrolyte-based protonic ceramic membrane fuel cells with Ba0.5Sr0.5Zn0.2Fe0.8O3−δ perovskite cathode

A stable, easily sintered perovskite oxide BaCe_0.5Zr_0.3Y_0.16Zn_0.04O_3−δ (BCZYZn) as an electrolyte for protonic ceramic membrane fuel cells (PCMFCs) with Ba_0.5Sr_0.5Zn_0.2Fe_0.8O_3−δ (BSZF) perovskite cathode was investigated. The BCZYZn perovskite electrolyte synthesized by a modified Pechini method exhibited higher sinterability and reached 97.4% relative density at 1200 °C for 5 h in air, which is about 200 °C lower than that without Zn dopant. By fabricating thin membrane BCZYZn electrolyte (about 30 μm in thickness) on NiO–BCZYZn anode support, PCMFCs were assembled and tested by selecting stable BSZF perovskite cathode. An open-circuit potential of 1.00 V, a maximum power density of 236 mW cm⁻², and a low polarization resistance of the electrodes of 0.17 Ω cm² were achieved at 700 °C. This investigation indicated that proton conducting electrolyte BCZYZn with BSZF perovskite cathode is a promising material system for the next generation solid oxide fuel cells.     

Stability and performance of infiltrated La0.8Sr0.2CoxFe1−xO3 electrodes with and without Sm0.2Ce0.8O1.9 interlayers

The chemical stability of composite electrodes produced by the infiltration of La_0.8Sr_0.2Co_xFe_1−xO₃ (LSCF) into a porous yttria-stabilized zirconia (YSZ) scaffold were investigated as a function of the Co:Fe ratio in the LSCF and the LSCF calcination temperature. XRD and impedance spectroscopy results indicate that for an LSCF calcination temperature of 1123 K, reactions between the LSCF and YSZ do not occur to a significant extent. Reactions producing La₂Zr₂O₇ and SrZrO₃ at the interface were observed, however, for a calcination temperature of 1373 K and x values greater than 0.2. In addition to determining the conditions for which reactions between LSCF and YSZ occur, the effectiveness of infiltrated SDC interlayers in preventing reactions at the LSCF-YSZ interface and their influence on the overall performance of LSCF/YSZ composite electrodes was studied.