Characteristics of Dye-Sensitized Solar Cells Using TiO2 Nanotube Arrays with Large Surface Area by Spin-Coating Nanoparticle

Highly ordered TiO₂ nanotube arrays (TNAs) fabricated by anodization are very attractive for use in dye-sensitized solar cells (DSSCs), because of their superior charge percolation and slow charge recombination. Highly ordered, vertically aligned TNAs have been prepared by three-step anodic oxidation. In this work, we investigated such strategies for improving the efficiency of DSSCs. Based on one of these approaches, oxide semiconductors in the form of a TNA were used as a novel method for improving electron transport through a film. A solution containing an appropriate amount of TiO₂ nanoparticles was prepared, and the mixed slurry was spin-coated on a TNA film. The coated film provided a large surface area for dye adsorption. The DSSCs achieved a light-to-electric energy conversion efficiency of 5.91% under simulated solar irradiation at 100 mW/cm² (AM 1.5).     

One-step fabrication of Fe2O3/Ag core-shell composite nanoparticles at low temperature

The Fe₂O₃/Ag core-shell composite nanoparticles were successfully prepared via a simple method at low temperature. X-ray diffraction data revealed the formation of core-shell composite nanoparticles, with Fe₂O₃ as the core and silver as the shell. The results from the transmission electron microscopy and scan electron microscopy further indicated that the composite nanoparticles were spherical with a core diameter and shell thickness of 26.0 nm and 13.5 nm, respectively. Magnetic measurements showed that the composite nanoparticles exhibited a typical ferromagnetic behavior, a specific saturation magnetization of 0.95 emu/g and an intrinsic coercivity of 104.0 Oe at room temperature. For a standard two-probe analysis at room temperature, the composite nanoparticles showed a typical conductive behavior and its conductivity was about 3.41 S/m. Moreover, this present synthesis method of Fe₂O₃/Ag core-shell composite nanoparticles shows an easy processing and does not need high-temperature calcining to attain the final product, which can be applied in a variety of areas, including catalysis, medicine, photonics, and new functional device assemblies.     

A ZnO/TiO2 composite nanorods photoanode with improved performance for dye‐sensitized solar cells

A dye‐sensitized solar cell (DSSC) based on ZnO/TiO₂ composite nanorods (NRs) photoanode is fabricated. The power conversion efficiency (PCE) of the ZnO/TiO₂ composite NRs film DSSC is 4.36%, which is obviously higher than that of DSSCs based on pure TiO₂ NRs (0.6%) and ZnO NRs (3.10%). The enhanced performance of ZnO/TiO₂ composite NRs film DSSC can be attributed to the combined effects of ZnO and TiO₂ NRs. In this architecture, the thick ZnO NRs overlayer offers a large surface area for enough dye absorption, while the thin TiO₂ NRs underlayer not only offers a direct and quick pathway for photoinjected electron transfer along the photoanode but also acts as a blocking layer, which effectively hinders the direct contact between the substrate and the electrolyte resulting in lower carrier recombination.     

Synthesis and Photocatalytic Properties of TiO2 Intercalated H4Nb6O17

Abstract

TiO₂ intercalated H₄Nb₆O₁₇ has been synthesized by the reactions of H₄Nb₆O₁₇ with a titanyl acylate complex followed by UV irradiation. The gallery height, specific surface area and Ti content of the sample synthesized by using titanyl acylate complex were larger than that using TiO₂ sol solution. Furthermore, the photocatalytic activity of the TiO₂ pillared H₄Nb₆O₁₇ prepared using a titanyl acylate precursor was twice larger than that fabricated using a TiO₂ sol solution.     

α‐Fe2O3 nanospindles loaded with ZnO nanocrystals: Synthesis and improved gas sensing performance

ZnO/α‐Fe₂O₃ nanocomposites were fabricated through a two‐step hydrothermal method. The morphology and composition of the as‐synthesized products were characterized by X‐ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), energy‐dispersive X‐ray spectroscopy (EDS), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The gas sensing properties of the fabricated products were investigated towards ethanol, acetone, propanol, isopropanol, formaldehyde, chloroform and so on. The results demonstrated that the ZnO/α‐Fe₂O₃ nanocomposites exhibited excellent sensing properties and showed remarkably higher sensing responses and much lower optimum operating temperature compared to individual ZnO and α‐Fe₂O₃. In addition, the ZnO/α‐Fe₂O₃ nanocomposites have some selectivity for ethanol, propanol and isopropanol. The possible gas sensing mechanism was also proposed. Our studies demonstrate that our fabricated materials could be widely used in the future.     

Transport and Electrochemical Properties of Bi2Sr2CaCu2O8 Superconductors

Abstract

Electrical conductivity and thermoelectric power measurements (77–300K) of both the pure and electrochemically doped with lithium Bi₂Sr₂CaCu₂O₈ system, are presented. Clear correlation between transport and electrochemical properties of Li_xBi₂Sr₂CaCu₂O₈ was shown.     

The preparation and structural characterization of ambient-dried porous methylsilicone matrix doped with SiO2 powder

Porous methylsilicone monoliths doped with SiO₂ powder were prepared by dispersion of SiO₂ nanoparticles in methylsilicone oligomer solution followed by ammonia-catalyzed gelation and ambient drying. The microstructure of the porous composite monoliths was investigated by FTIR, SEM, and N₂ adsorption. The results indicated that SiO₂ evenly dispersed in methylsilicone matrix. The thermal stability of SiO₂-doped methylsilicone monoliths had been enhanced. The structure stability and hydrophobic property of the composite monoliths were maintained until 400 °C.     

Structural and electrical properties of lead-free perovskite ceramic: Ba(In1/2Nb1/2)O3

Lead-free perovskite Ba(In_1/2Nb_1/2)O₃ was prepared by conventional ceramic fabrication technique at 1350 °C/5 h in air atmosphere. The crystal symmetry, space group and unit cell dimensions were determined from Rietveld analysis using FullProf software whereas crystallite size and lattice strain were estimated from Williamson-Hall approach. XRD analysis of the compound indicated the formation of a single-phase cubic structure with the space group Pm3m. EDAX and SEM studies were carried out in order to evaluate the quality and purity of the compound. Complex impedance as well as electric modulus analyses suggested the dielectric relaxation to be of non-Debye type. The correlated barrier hopping (CBH) model was employed to successfully explain the mechanism of charge transport in Ba(In_1/2Nb_1/2)O₃.     

Studies on the fabrication and characteristics of photoelectrochemical cells using IrO2-coated TiO2 photoanode for Z-scheme water splitting and perovskite solar cell bias

ABSTRACT

In the present work, to build a water splitting system using only a neutral electrolyte solution and light source, we investigated the photoelectrochemical properties and interface resistances of an IrO₂-coated TiO₂ photoanode in Z-scheme configuration. The photoelectrochemical cell was connected to the perovskite solar cell with to realize the system with no need for an external electrical bias. Photoanodes with IrO₂ were found to support hole transport and to reduce the overpotential, therefore increasing the current density of the system consisting of photoelectrochemical cells. A maximum solar-to-hydrogen efficiency of 8.2% was achieved in a neutral electrolyte.     

The effect of Zn-acetate molar variation on phase formation and photocatalytic degradation activity of Fe3O4/ZnO core-shell nanocomposite

Abstract

The aim of this research is to investigate the photodegradation of Methylene Blue with Fe₃O₄/ZnO core-shells. Fe₃O₄/ZnO core-shells were synthesized by a simple two-step chemical method (co-precipitation and precipitation) using a molar variation of Zn-acetate precursor. We found that the presence of Fe₂O₃ plays an important role in enhancement of photocatalytic activity due to the existence of higher concentration of surface oxygen vacancies and the suppressing effect of the Fe²⁺ ions on the recombination of photoinduced electron-hole pairs. The core-shell photocatalyst can be easily separated by using a commercial magnet without reduces photocatalytic efficiency within three times of recycling process.     

Highly Luminescent Red Phosphorescent OLED with Interfacial Layers for Hole Transport and Electron Injection

Four kinds of red phosphorescent organic light-emitting devices were fabricated and compared to investigate the effect of interfacial layers for hole transport and electron injection. 1 nm-thick LiF in the device A and C and 1 nm-thick Cs₂CO₃ in the device B and D were deposited as an electron injection layer between the anode and the electron transport layer, and 5 nm-thick layer of dipyrazion[2,3-f:2′,2′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile[HATCN] was inserted as a hole transport interfacial layer between the hole injection layer and the hole transport layer only in the device C and D. Under a luminance of 1000 cd/m², the power efficiencies were 7.6 lm/W and 8.5 lm/W in the device A and B, and 8.6 lm/W and 13.4 lm/W in the device C and D. The quantum efficiency of the device D was 15.8% under 1000 cd/m² which was somewhat lower than those of the device A and C, but a little higher than that of the device B. The luminance of the device D was much higher than those of the other devices at a given votage. The luminance of the device D at 7 V was 23,710 cd/m², which was 13.0, 3.4, and 4.0 times higher than those of the device A, B, and C at the same voltage, respectively.     

Photocatalytic properties of TiO2/ZnO thin film

ABSTRACT

TiO₂, ZnO and ZnO/TiO₂ thin films have been prepared by radio frequency magnetron sputtering method under different temperatures. Their photo catalytic activities have been investigated. The structural of the thin films were characterized by X-ray diffraction and Raman spectroscopy. The photo catalytic activities of TiO₂ and ZnO/TiO₂ samples were evaluated by the photo decomposition of methylene blue. We note that the structural proprieties of the thin films showed a perfect crystallization along the (002) for ZnO, Rutile (110) for TiO₂ and Anatase (101) for TiO₂. The experimental results show that the bilayer ZnO/TiO₂ were the most efficient photo catalysts compared to the layer of TiO₂. This increased catalytic effect can attributed to the interface between the ZnO layer and the TiO₂ one, which modify significantly the chemical potential of the bilayer.     

Identification of a new family of diphosphate compounds, AI2BII3(P2O7)2: Structures of Ag2Co3(P2O7)2, Ag2Mn3(P2O7)2, and Na2Cd3(P2O7)2

Syntheses and single-crystal X-ray structural results are reported for three new mixed diphosphates of the family A^I ₂B^II ₃(P₂O₇)₂; Ag₂Co₃(P₂O₇)₂ (I), Ag₂Mn₃(P₂O₇)₂ (II), and Na₂Cd₃(P₂O₇)₂ (III). All crystallize in the triclinic system, space group P1 bar: (I) a = 5.351(4), b = 6.375(4), c = 16.532(4) Å, = 80.83(6) = 81.45(4), = 72.87(5)°, V = 528.9(6) ų, Z = 2, D _calc = 4.649 mg/m³, R/Rw = 0.0428/0.0548 for 3949 obs. reflns; (II) a = 5.432(7), b = 6.619(6), c = 16.51(3) Å, = 80.78(8) = 82.43(9), = 72.82(7)°, V = 557.7(13) ų, Z = 2, D _calc = 4.338 mg/m³, R/Rw = 0.0679/0.1303 for 2100 obs. reflns and (III) a = 5.67(3), b = 7.08(4), c = 7.90(4) Å, = 77.0(2), = 82.5(2), = 67.8(2)°, V = 286(3) ų, Z = 2, D _calc = 4.249 mg/m³, R/Rw = 0.0307/0.0342 for 1945 obs. reflns. (I) and (II) are isostructural but (III) is of a different type. All three structures are characterized by layers of P₂O₇ groups alternating with layers of mixed metal atoms. Differences are seen in the conglomerate bonding patterns of B atoms and in the irregular geometry of Ag in (I) and (II) compared to the octahedral bonding seen for Na in (III). The differences in structure may be understood in terms of the ratios of the ionic radii of A and B atoms.     

Investigation of the structure evolution process in sol-gel derived CaO-B2O3-SiO2 glass ceramics

A sol-gel method was used to prepare CaO-B₂O₃-SiO₂ (CBS) glass powder for making low-temperature cofired ceramics. This paper was focused on the mechanism of hydrolysis and polymerization and also on the structural evolution of xerogel at various temperatures. The xerogel was transformed into glass ceramics containing CaSiO₃ and CaB₂O₄ crystalline phases through nucleation and crystallization processes. The results indicated that the xerogel exhibits [BO₄] or [SiO₄] based three-dimensional network structure whose interstices Ca ions fill in, which becomes more orderly and stable after heat treatments. The CBS glass ceramics through controlled crystallization have a potential as electronic packaging materials.     

Considerations on the structure and physical properties of B2O3-SiO2 and GeO2-SiO2 glasses

Data of density, refractive index and thermal expansion coefficient for B₂O₃-SiO₂ and GeO_2-SiO₂ glasses have been analyzed. The volumes of the structural units are the same found for the vitreous B₂O₃, GeO₂ and SiO₂. The volume of any structural unit is constant over the entire composition region of the glass system. The same has been found for the differential refraction and unit refraction of the structural units in these glasses. Different features are observed for the differential expansion of the structural units. There is a considerable change with composition in the differential expansion of BO₃, GeO₄ and SiO₄ units. The effect is attributed to a change in the asymmetry of vibrations with the number of Si-O-B or Si-O-Ge linkages in the matrix. The thermal expansion coefficient is mainly determined by the contribution of B₂O₃ or GeO₂ in the concerned glasses.     

Advanced nanostructure Ti0.7In0.3O2 support enhances electron transfer to Pt: Used as high performance catalyst for oxygen reduction reaction

ABSTRACT

The slow rate of the oxygen reduction reaction (ORR) and the instability of Pt based catalysts are two of the most important issues which must be solved in order to make proton exchange membrane fuel cells (PEMFCs) a reality. Here, we present a new approach by exploring robust non-carbon Ti_0.7In_0.3O₂ used as a novel functionalised co-catalytic support for Pt. This approach is based on the novel nanostructure Ti_0.7In_0.3O₂ support with “electronic transfer mechanism” from Ti_0.7In_0.3O₂ to Pt that can modify surface electronic structure of Pt, owing to a shift in the d-band centre of the surface Pt atoms. The 20 wt% Pt/Ti_0.7In_0.3O₂ catalyst shows high activity than that of that of the commercial 20 wt% Pt/C (E-TEK). Our data suggest this enhancement is a result of both the electronic structure change of Pt upon its synergistic interaction with Ti_0.7In_0.3O₂ and the inherent structural and chemical stability and the corrosion-resistance of the Ti_0.7In_0.3O₂ in acidic and oxidative environments.     

Thermal, chemical, optical properties and structure of Er-doped and Er/Yb-codoped P2O5-Al2O3-ZnO glasses

This study was explored in series of the optical, thermal, and structure properties based on 60P₂O₅-10Al₂O₃-30ZnO (PAZ) glasses system that doped with varied rare-earth (RE) elements Yb₂O₃/Er₂O₃. The glass transition temperature, softening temperature and chemical durability were increased with RE-doping concentrations increasing, whereas thermal expansion coefficient was decreased. In the optical properties, the absorption and emission intensities also increase with RE-doping concentrations increasing, When Er₂O₃ and Yb₂O₃ concentrations are over than 3 mol% in the Er³⁺-doped PAZ system and Yb³⁺-doped concentration is over than 3 mol% for Er³⁺/Yb³⁺-codoped PAZ system, the emission intensity significantly decreases presumably due to concentration quenching, formation of the ions clustering, and OH⁻ groups in the glasses network. It is suggested that the maximum emission cross-section (σ_e) is 7.64 × 10^− 21 cm² at 1535 nm is observed for 3 mol% Er³⁺-doped PAZ glasses. Moreover, the maximum σ_e × full-width-at-half-maximum is 327.8 for 5 mol% Er³⁺-doped PAZ glasses.     

Synthetic nanodiamonds (SNDs) containing bimetallic Ni(Co)–Fe composites: preparation,characterization and catalytic performance in the reaction of CO2 methanation

Abstract

In this article, we present the preparation, characterization, and catalytic performance of bimetallic Co₉₃Fe₀₇ and Ni₈₀Fe₂₀ active mass loaded on synthetic nanodiamonds (SNDs) in the carbon dioxide (CO₂) methanation. The pristine SNDs possessing a developed specific surface are thermally stable and inert to the reaction mixture of CO₂ and dihydrogen. However, it is shown that 100% conversion of CO₂ into methane can be reached at the lower temperature than that for a massive Co₉₃Fe₀₇ or Ni₈₀Fe₂₀ catalyst when 20?wt.% of the catalyst mass was loaded on the surface of SNDs. The catalytic activity of the prepared bimetallic/SNDs composites is estimated as the minimum temperature at the maximum conversion of CO₂ at atmospheric pressure: it is 325 and 290?°C for Co₉₃Fe₀₇/SNDs and Ni₈₀Fe₂₀/SNDs, respectively. Thermal desorption studies showed that the methanation over Co-Fe/SNDs and Ni-Fe/SNDs catalysts run through the stage of CO₂ dissociation into carbon and oxygen atoms and their subsequent interaction with hydrogen to form methane and water molecules. Scanning electron microscopy studies have shown that the presence of transition metal-rich sites on the surface of the carrier contributes to the improvement of efficiency of the Ni₈₀Fe₂₀ catalyst action.     

Tunable synthesis of hierarchical TiO2 spheres consisting of rutile nanowires for dye‐sensitized solar cells and photocatalysis

Hierarchical TiO₂ spheres consisting of rutile nanowires (HTS) are successfully prepared in the bulk solution via a non‐polar solvent/polar solution interfacial syntheses strategy. The effect of reaction temperature on the morphology, size, BET surface area and monodispersion of HTS is studied systematically. Increasing reaction temperature decreases the diameter of spheres in micro‐scale whereas increases the diameter of nanowires in nano‐scale for these HTS. Monodisperse HTS are formed at 230 °C for 20 h, which can suitably be served as light scattering structure for dye‐sensitized solar cell with the additional advantage of rapid electron transport rate. A high efficiency of 8.54% was achieved for the composite DSSC consisting of nanoparticles and monodispersed HTS (synthesized at 230 °C), showing 31.38% improvement compared with that (6.5%) of the DSSCs made from pure P25 nanoparticles at the similar thickness. Furthermore, the photocatalytic performances of HTS for the degradation of methyl orange were also investigated. Contrary to the effect on the performance of DSSC, the HTS synthesized at 150 °C show higher photocatalytic degradation efficiency due to larger BET surface area.     

Fabrication of Al2O3 Coatings on Metal Substrates by Electrophoretic Deposition by the Addition of Polydimethylsiloxane-Based Organic-Inorganic Hybrid Materials as Binders

Polydimethylsiloxane (PDMS)-based organic-inorganic hybrids have been studied because of their high dielectric strength, heat resistivity, and flexibility. In this study, we fabricated Al₂O₃ coatings on metal substrates with sufficient electrical insulation, heat conductivity, and thermal stability by electrophoretic deposition (EPD) using PDMS-based hybrid binders. The scratch hardness, thermal conductivity, and electrical breakdown strength of the Al₂O₃ coating before and after heat treatment at 300 °C for 500 h were 2.0 N, 3.1 W/mK, and 60 kV/mm, respectively. These results demonstrate the usefulness of EPD using PDMS-based hybrid binders for fabricating flexible heat dissipative substrates used in high-temperature environments.