Search

Sr(Ti0·3Fe0.7)O3-δ (STF) materials with satisfactory stability and no rare-metal elements have attracted increasing research interest as oxygen electrodes of solid oxide electrochemical cells. However, STF-based electrodes are still limited by their modest catalytic activities at low temperatures. This can be improved by A-site deficiency of STF-based materials; however, data related to the influence of A-site deficiency of perovskite-oxide-based materials on sintering behavior and electrochemical performance are still lacking. Herein, porous electrodes with different Srx (Ti0·3Fe0.7)O3-δ compositions (x = 0.85–1) were prepared. The effects of A-site cation deficiency ratios and sintering temperatures on the microstructures and electrochemical performance of the as-obtained STF electrodes were investigated. Electrochemical performance was improved for A-site deficient Srx (Ti0·3Fe0.7)O3-δ. For Sr0·9(Ti0·3Fe0.7)3-δ electrode material sintered at 1050 °C, the lowest polarization resistance measured at 700 °C was ~0.14 Ω⸳cm2 but increased at higher x values. At sintering temperatures above 1050 °C, the sintering diffusion occurred, where the electrolyte diffused through the deficient electrodes to form a dense layer at the electrode/electrolyte interface. On the other hand, although the presence of such diffused dense layer did not have significant effect on the electrochemical performance of the cells, it could be prevented by using lower sintering temperatures (≤1000 °C) to avoid possible negative effects on comprehensive performance. For the electrode obtained at x = 0.9 and sintered at 1000 °C, the overall polarization resistance was recorded as 0.099 Ω⸳cm2 at 700 °C. In sum, these findings look promising for future research.

The modified Pechini method was applied to prepare a highly active and novel cathode material La0.7Sr0.3Ti0.15Fe0.65Ni0.2O3-δ (LSTFN). This material was coated on the LGSM electrolyte through a screen-printing technique with variable thicknesses of 28 ± 8, 41 ± 8, and 62 ± 8 μm, respectively. Different fabrication parameters, including sintering temperature, time, coating thickness, and variations in ball-milling, which affect the electrochemical performance of the cathode material, were investigated. X-ray diffraction analysis of the cathode material suggested that it exhibits a cubic crystal structure with a LSTFN single phase. The morphological studies were conducted using scanning electron microscopy (SEM), which confirmed that the electrode material had a highly porous structure. Meanwhile, the electrochemical properties of the material were studied by electrochemical impedance spectroscopy (EIS), which revealed that by varying different parameters, the electrochemical performance of the electrode material was enhanced. The coated cathode materials with variable thicknesses were analyzed at different sintering temperatures and times. Experimental results suggest that the optimum sintering temperature and time were 950 °C and 3 h, respectively, at which LSTFN exhibits the minimum polarization resistance (RP) of 0.046 Ωcm2 when sintered at 800 °C for 3 h.

Funding Information: This work was supported by the National Natural Science Foundation of China (52105582), the Natural Science Foundation of Guangdong Province (grant no. 2020A1515011555), the High-Talent Research Funding (827-000451), the Fundamental Research Foundation of Shenzhen (JCYJ20210324095210030), the Open Foundation of the State Key Laboratory of Digital Manufacturing Equipment and Technology (DMETKF2021016), and the National Natural Science Foundation of China (11674085 and 51772080). M.I. Asghar thanks the Hubei overseas Talent 100 programme (as a distinguished Professor at Hubei University) and the Academy of Finland (grant nos. 13329016 and 13322738) for its support. We are thankful to Dr. Ghulam Yasin for proofreading and suggestions. We are really thankful to Dr. Xiuan Xi and Prof. Dr. Xian-Zhu Fu for initially using their GC characterization facilities and their discussion at the College of Materials Science and Engineering, Shenzhen University and then utilizing another GC–MS characterization for further analysis. F Achieving fast ionic conductivity in the electrolyte at low operating temperatures while maintaining the stable and high electrochemical performance of solid oxide fuel cells (SOFCs) is challenging. Herein, we propose a new type of electrolyte based on perovskite Sr0.5Pr0.5Fe0.4Ti0.6O3-δ for low-temperature SOFCs. The ionic conducting behavior of the electrolyte is modulated using Mg doping, and three different Sr0.5Pr0.5Fe0.4-xMgxTi0.6O3-δ (x = 0, 0.1, and 0.2) samples are prepared. The synthesized Sr0.5Pr0.5Fe0.2Mg0.2Ti0.6O3-δ (SPFMg0.2T) proved to be an optimal electrolyte material, exhibiting a high ionic conductivity of 0.133 S cm-1 along with an attractive fuel cell performance of 0.83 W cm-2 at 520 °C. We proved that a proper amount of Mg doping (20%) contributes to the creation of an adequate number of oxygen vacancies, which facilitates the fast transport of the oxide ions. Considering its rapid oxide ion transport, the prepared SPFMg0.2T presented heterostructure characteristics in the form of an insulating core and superionic conduction via surface layers. In addition, the effect of Mg doping is intensively investigated to tune the band structure for the transport of charged species. Meanwhile, the concept of energy band alignment is employed to interpret the working principle of the proposed electrolyte. Moreover, the density functional theory is utilized to determine the perovskite structures of SrTiO3-δ and Sr0.5Pr0.5Fe0.4-xMgxTi0.6O3-δ (x = 0, 0.1, and 0.2) and their electronic states. Further, the SPFMg0.2T with 20% Mg doping exhibited low dissociation energy, which ensures the fast and high ionic conduction in the electrolyte. Inclusively, Sr0.5Pr0.5Fe0.4Ti0.6O3-δ is a promising electrolyte for SOFCs, and its performance can be efficiently boosted via Mg doping to modulate the energy band structure.

Herein, the preparation of nanotubular and porous TiO2 structures (TNS) is presented for photocatalytic applications. Different TNS were prepared in three different types of glycerol- and ethylene glycol-based electrolytes on a large area (approx. 20 cm2) via anodization using different conditions (applied potential, fluoride concentration). Morphology, structure, and optical properties of TNS were characterized by Scanning Electron Microscopy (SEM), X-ray Diffractometry (XRD), and Diffuse Reflectance Spectroscopy (DRS), respectively. All TNS possess optical band-gap energy (EBG) in the range from 3.1 eV to 3.2 eV. Photocatalytic degradation of caffeine was conducted to evaluate the efficiency of TNS. Overall, nanotubular TiO2 possessed enhanced degradation efficiencies (up to 50% degradation) compared to those of porous TiO2 (up to 30% degradation). This is due to the unique properties of nanotubular TiO2, e.g., improved incident light utilization. As the anodization of large areas is, nowadays, becoming a trend, we show that both nanotubular and porous TiO2 are promising for their use in photocatalysis and could be potentially applicable in photoreactors for wastewater treatment. We believe this present work can be the foundation for future development of efficient TiO2 nanostructures for industrial applications.

The efficient performance of Solid Oxide Fuel Cell (SOFC) by utilizing safe and cost effective hydrocarbon fuels at low temperature is really a challenging task due to C–H activation and sluggish oxidation/reduction kinetics. In this study a novel [Sr0.4La0.6(Fe0.75Ti0.25)0.6Ni0.4O3-δ] (SLFTNO) nanocomposite was synthesized via solid state reaction route and was evaluated electrochemically in presence of multifuels such as hydrogen, ammonia, methane and ethanol. Phase purity and structural analysis was carried out through X-Ray Diffractometer (XRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM). The average crystallite size calculated was ranged from 60-100 nm. The electrical conductivity and power density was measured between (89–226) S/cm and (147–318) mW/cm2 respectively among different fuels. This study indicated the synthesized SLFTNO nanocomposite as stable and efficient multifuels candidate for SOFCs.

Nanocomposite multi-layer TiO2/V2O5/TiO2 thin films were prepared via electron-beam evaporation using high-purity targets (TiO2 and V2O5 purity > 99.9%) at substrate temperatures of 270 °C (TiO2) and 25 °C (V2O5) under a partial pressure of oxygen of 2 × 10−4 mbar to maintain the stoichiometry. Rutherford backscattering spectrometry was used to confirm the layer structure and the optimal stoichiometry of the thin films, with a particle size of 20 to 40 nm. The thin films showed an optical transmittance of ~78% in the visible region and a reflectance of ~90% in the infrared. A decrease in transmittance was observed due to the greater cumulative thickness of the three layers and multiple reflections at the interface of the layers. The optical bandgap of the TiO2 mono-layer was ~3.49 eV, whereas that of the multi-layer TiO2/V2O5/TiO2 reached ~3.51 eV. The increase in the optical bandgap was due to the inter-diffusion of the layers at an elevated substrate temperature during the deposition. The intrinsic, structural, and morphological features of the TiO2/V2O5/TiO2 thin films suggest their efficient use as a solar water heater system.

Enhanced non-linearity and asymmetric behavior of the Cr/metal oxide diode is reported, with the addition of two insulator layers of SnO2 and NiO to form the metal-insulator-insulator-metal (MIIM) configuration. Such an MIIM diode shows potential for various applications (rectifiers and electronic equipment) which enable the femtosecond fast intoxication in MIIM diodes. In this work, nanostructured multi-layer Cr/SnO2/NiO/Cr coatings were fabricated via e-beam evaporation with the following thicknesses: 150 nm/20 nm/10 nm/150 nm. Coatings were characterized via Rutherford backscattering (RBS), scanning electron microscopy (SEM), and two-probe conductivity testing. RBS confirmed the layered structure and optimal stoichiometry of the coatings. A non-linear and asymmetric behavior at

Thin films of lead sulfide (PbS) are being extensively used for the fabrication of optoelectronic devices for commercial and military applications. In the present work, PbS films were fabricated onto a soda lime glass substrate by using an electron beam (e-beam) evaporation technique at a substrate temperature of 300 °C. Samples were annealed in an open atmosphere at a temperature range of 200–450 °C for 2 h. The deposited films were characterized for structural, optical, and electrical properties. Structural properties of PbS have been studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and Rutherford backscattering spectrometry (RBS). The results of XRD showed that the PbS thin film was crystalline in nature at room temperature with cubic crystal structure (galena) and preferential (111) and orientation (022). The morphology of the thin films was studied by FESEM, which also showed uniform and continuous deposition without any peel-off and patches. EDS analysis was performed to confirm the presence of lead and sulfur in as-deposited and annealed films. The thickness of the PbS film was found to be 172 nm, which is slightly greater than the intended thickness of 150 nm, determined by RBS. Ultraviolet-Visible-Near-Infrared (UV-Vis-NIR) spectroscopy revealed the maximum transmittance of ~25% for as-deposited films, with an increase of 74% in annealed films. The band gap of PbS was found in the range of 2.12–2.78 eV for as-deposited and annealed films. Hall measurement confirmed the carriers are p-type in nature. Carrier concentration, mobility of the carriers, conductivity, and sheet resistance are directly determined by Hall-effect measurement. The as-deposited sample showed a conductivity of 5.45 × 10−4 S/m, which gradually reduced to 1.21 × 10−5 S/m due to the composite nature of films (lead sulfide along with lead oxide). Furthermore, the present work also reflects the control of properties by controlling the amount of PbO present in the PbS films which are suitable for various applications (such as IR sensors).

Funding Information: This work was supported by the National Natural Science Foundation of China (NSFC, Grant Nos. 51774259, 51772080, and 51675496) and the Engineering Research Center of Nano-Geo Materials of Ministry of Education (NGM2017KF004, NGM2017KF012, and NGM2018KF016). Dr. Asghar acknowledges the support from the Hubei overseas Talent 100 program (as a distinguished professor at Hubei University) and the Academy of Finland (Grant No. 13329016, 13322738) for their support. Publisher Copyright: © Introducing triple-charge (H+/O2-/e-) conducting materials is a promising alternative to modify a cathode as an electrolyte in advanced ceramic fuel cells (CFC). Herein, we designed a novel triple-charge conducting perovskite-structured semiconductor Co0.2/Fe0.2-codoped La0.5Ba0.5Zr0.3Y0.3O3-δ (CF-LBZY) and used as an electrolyte and an electrode. CF-LBZY perovskite as an electrolyte exhibited high ionic (O2-/H+) conductivity of 0.23 S/cm and achieved a remarkable power density of 656 mW/cm2 550 °C. X-ray photoelectron spectroscopy (XPS) analysis revealed that the Co/Fe codoping supports the formation of oxygen vacancies at the B-site of a perovskite structure. Besides, using CF-LBZY as a cathode, the fuel cell delivered 150 and 177 mW/cm2 at 550 °C, respectively, where Y-doped BaZrO3 and Sm-doped ceria (SDC) were used as electrolytes. During the fuel-cell operation, H+ injection into the CF-LBZY electrolyte may suppress electronic conduction. Furthermore, the metal-semiconductor junction (Schottky junction) has been proposed by considering the work function and electron affinity to interpret short-circuiting avoidance in our device. The current systematic study indicates that triple-charge conduction in CF-LBZYO3-δ has potential to boost the electrochemical performance in advanced low-temperature fuel-cell technology.

A flood is an overflow of water that swamps dry land. The gravest effects of flooding are the loss of human life and economic losses. An early warning of these events can be very effective in minimizing the losses. Social media websites such as Twitter and Facebook are quite effective in the efficient dissemination of information pertinent to any emergency. Users on these social networking sites share both textual and rich content images and videos. The Multimedia Evaluation Benchmark (MediaEval) offers challenges in the form of shared tasks to develop and evaluate new algorithms, approaches and technologies for explorations and exploitations of multimedia in decision making for real time problems. Since 2015, the MediaEval has been running a shared task of predicting several aspects of flooding and through these shared tasks, many improvements have been observed. In this paper, the classification framework VRBagged-Net is proposed and implemented for flood classification. The framework utilizes the deep learning models Visual Geometry Group (VGG) and Residual Network (ResNet), along with the technique of Bootstrap aggregating (Bagging). Various disaster-based datasets were selected for the validation of the VRBagged-Net framework. All the datasets belong to the MediaEval Benchmark Workshop, this includes Disaster Image Retrieval from Social Media (DIRSM), Flood Classification for Social Multimedia (FCSM) and Image based News Topic Disambiguation (INTD). VRBagged-Net performed encouraging well in all these datasets with slightly different but relevant tasks. It produces Mean Average Precision at different levels of 98.12, and Average Precision at 480 of 93.64 on DIRSM. On the FCSM dataset, it produces an F1 score of 90.58. Moreover, the framework has been applied on the dataset of Image-Based News Topic Disambiguation (INTD), and exceeds the previous best result by producing an F1 evaluation of 93.76. The VRBagged-Net with a slight modification also ranked first in the flood-related Multimedia Task at the MediaEval Workshop 2020.

HfO2 and V2O5 as multi-layer thin films are discussed for their potential use as transparent heat mirrors. Multi-layered HfO2/V2O5/HfO2 thin films with a thickness of 100/60/100 nm were prepared via e-beam evaporation on a soda–lime glass substrate. Rutherford backscattering confirmed the multi-layer structure with uniform surface. The as-deposited thin films were annealed at 300 °C and 400 °C, respectively, for 1 h in air. The transmittance of approximately 90% was obtained for all thin films. Due to the relatively low thickness and non-stoichiometry of HfO2, a band gap of approximately 3.25 eV was determined (instead of the theoretical 5.3–5.7 eV). The as-deposited thin films possessed conductivity of approximately 0.2 Ω−1cm−1 and increased to 1 Ω−1cm−1 and 2 Ω−1cm−1 for thin films annealed at 300 and 400 °C, respectively. Due to the unique intrinsic properties of HfO2/V2O5/HfO2 thin films, the results obtained are promising for application as a transparent heat mirror.

Solid oxide fuel cells (SOFCs) have the potential to be used in energy conversion technology. Most of the studies aimed at modifications of anode concerning various issues such as component degradation, sulfur poisoning, and carbon deposition at high temperatures, hindering its applications at the industrial level. Different perovskite structure-related compounds are discussed in this article, which could be possible electrode materials in SOFCs. Literature also revealed the successful utilization of various cathode materials in a wide range of temperature in which cobalt-based materials exhibits higher conductivity than cobalt-free once. The selection of initial composition, dopants addition in different electrodes with critical challenges inherent to this material family have been assessed herein which play a vital role in enhanced electrochemical performance. The other aim of this review article is to provide some useful recommendations and prospective directions for designing future electrode materials of SOFCs. The review analysis is done based on different processing parameters and their effect on thermal expansion coefficient, electrical conductivity, mechanical and electrochemical properties, etc. In a nutshell, a detailed overview is critically analyzed for energy conversion and storage applications, which can open many gateways towards the advancement of SOFCs.

In comparison to various power generating devices/energy conversion systems, solid oxide fuel cell (SOFC) has received much attention due to its remarkable efficiency, reliability and low pollution. Modified pechini method is used to synthesize La0.7Sr0.3Ti0.1Fe0.6Ni0.3O3-δ (LSTFN) perovskite material and is utilized as cathode and anode for intermediate-temperature symmetrical solid oxide fuel cell (IT-SSOFC). The X-ray diffractometer (XRD) patterns reveals perovskite cubic structure with single phase for LSTFN. The maximum conductivity ~318 Scm−1 is obtained for LSTFN in air at a temperature of 700 °C, but is decreased with further increase in temperature due to small polaron mechanism. However, the conductivity is enhanced up to ~1.1 Scm−1 at the same temperature in the presence of dry H2, being capable to be utilized both as anode and cathode. Low polarization resistance (Rp) ~0.047 (with air) and 0.201Ωcm2 (with dry H2) is exhibited by as prepared perovskite material at a temperature of 800 °C. The fabricated symmetrical cell maintains good stability with no apparent degradation during the tested hours ~300 in air and ~100 with dry H2.