Zirconium-assisted reaction in low temperature atomic layer deposition using Bis(ethyl-methyl-amino)silane and water

The reaction of Bis(ethyl-methyl-amino)silane (BEMAS) and water in atomic layer deposition (ALD) became possible when Zr-containing species were adsorbed on the vacant sites of the surface after a pulse and purge of BEMAS. The growth rates of the Si(Zr)O_x films were 0.8-0.9 nm/cycle in the temperature range of 185-325 °C. This phenomenon probably originates from the highly reactive hydroxyl species generated by Zr atoms. From this point of view, transition metals make reactant gas molecules to be highly activated in the ALD processes of transition metal oxides and nitrides, which might be an important factor that determines the ALD characteristics.     

Long-term stability of sulfated hydrous titania-based electrolyte for water electrolysis

Journal of Solid State Electrochemistry - The long-term stability in water was investigated for an inorganic proton conductor based on sulfated hydrous titania electrolyte in water electrolysis....     

Proton conduction properties of nano-titania modified by sulfuric acid impregnation

The proton conduction properties of sulfuric acid-modified nano-titania prepared by impregnation method were investigated. The proton conductivity of sulfuric acid-modified nano-titania was almost the same as that of hydrous sulfated nano-titania investigated in our previous work when the amount of adsorbed sulfate groups was almost the same. The highest conductivity was obtained at an adsorbed sulfate group amount of 0.42?mmol/g, not 0.97?mmol/g. This result indicates that the enhancement of conductivity with increasing amount of adsorbed sulfate groups is limited. This might be attributable to insufficient water molecule adsorption on the Ti⁴⁺ site coordinated with a bidentate sulfate group due to the prevention by excess sulfuric acid.     

In situ polymerization: A novel route for thermally stable proton-conductive membranes

In this paper, a new solvent-free route for preparing proton-conductive membranes is proposed. Flexible and fiber-supported polymer electrolyte membranes, as potential proton exchange membranes, were readily obtained by in situ polymerization of a homogenous solution that consisted of bromomethylated poly(2,6-dimethyl-1,4-phenylene oxide) (BPPO, polymer)–monomer mixtures of styrene (ST) and divinylbenzene (DVB), which was pre-cast onto SEFAR PETEX fibers. Factors such as the components of the casting solution and the sulfonation time, were fully investigated. The membrane structure and components were confirmed by FTIR-ATR spectra and SEM-EDXA images, and the thermal stability was examined via TGA and DrTGA. The membrane exhibited a proton conductivity of about 0.07 S/cm at 100% humidity and at room temperature, which is close to that of Nafion 117 at identical conditions (around 0.08 S/cm), whereas its thickness (about 120 μm) was less than that of Nafion 117. The tensile strength and the elongation at the break of the membrane were 31.2 MPa and 71%, respectively, which are several times higher than those of Nafion (about 6.16 MPa tensile strength and 36% elongation ratio). The dimensional change ratio of the membrane between the wet and dry states was below 3%, which is much lower than that of Nafion 117. The membrane showed a high thermal stability up to 400 °C. The method can be applied to other compatible systems of (aromatic) polymers and (aromatic) monomers.     

Fabrication and characterization of a Cu seed layer on a 60-nm trench-patterned SiO2 substrate by a self-assembled-monolayer (SAM) process

Continuous electroless deposition of a 10-nm thick layer of Cu was successfully performed on a SiO₂/Si substrate coated with a 3-nm Au catalytic layer. The Au catalytic layer was formed by a self-assembled monolayer (SAM) process terminated with NH₂ headgroups, upon which negatively charged Au particles were deposited via electrostatic interaction with the positively charged NH₂-SAM. The Au and NH₂-SAM layers were analyzed by X-ray photoelectron spectroscopy (XPS) and contact angle analysis. Atomic force microscopy, field emission scanning electron microscopy, and XPS revealed that the Cu layer formed by this electroless processes had good step-coverage, small grain size, and excellent adhesion to the substrate. The proposed process is a very promising method for fabrication of a conductive Cu seed layer in a 60-nm trench-pattern.     

Asymmetric polymer electrolyte membranes for water management of fuel cells

Water management is one of the critical issues of polymer electrolyte membrane fuel cells because dehydration of a membrane increases membrane-resistance whereas excessive water flooding at the cathode impedes the gaseous diffusion of oxygen to reaction sites at the wetted catalyst surface. In this study, we have developed an asymmetric polymer electrolyte membrane that facilitates water management. The structural modification of the membrane strongly affected water management, due primarily to the fact that water must move through the membrane during fuel cell operation. The asymmetric membrane improved transport of water from the cathode to the anode when the hydrophilic side of the membrane located to the cathode, thereby enhancing overall fuel cell performance under both fully humidified and non-humidified conditions.     

Analyses of interfacial resistances in a membrane-electrode assembly for a proton exchange membrane fuel cell using symmetrical impedance spectroscopy

Interfacial resistances between the polymer electrolyte membrane (PEM) and catalyst layer (CL) in membrane-electrode assemblies (MEAs) have yet to be systematically examined in spite of its great importance on the fuel cell performance. In order to investigate ionic transport through the PEM/CL interface, the symmetrical impedance mode (SIM) was employed in which the same type of gas was injected (H(2)/H(2)). In this study, the ionic transport resistance at the interface was controlled by the additionally sprayed outer ionomer on the surface of each CL. Effectiveness of the outer ionomer on ionic transport at the interface was quantitatively explained by the reduced contact, proton hydration, and charge transport resistances in the SIM. To characterize the ionic transport resistance, the concept of total resistance (R(tot)) in the SIM was introduced, representing the overall ohmic loss due to proton transport in an MEA. This concept was successfully supported via an agreement of the interpretation and the linear correlation that was obtained between the admittance (1/R(tot)) and the performance of a fuel cell in the ohmic loss region. This correlation will enable researchers to predict the performance of a fuel cell under the influence of proton transport by examining the R(tot) in the SIM.     

Determination of trace amounts of lead and cadmium using a bismuth/glassy carbon composite electrode

We examined the use of a bismuth-glassy carbon (Bi/C) composite electrode for the determination of trace amounts of lead and cadmium. Incorporated bismuth powder in the composite electrode was electrochemically dissolved in 0.1 M acetate buffer (pH 4.5) where nanosized bismuth particles were deposited on the glassy carbon at the reduction potential. The anodic stripping voltammetry on the Bi/C composite electrode exhibited well-defined, sharp and undistorted peaks with a favorable resolution for lead and cadmium. Comparing a non-oxidized Bi/C composite electrode with an in-situ plated bismuth film electrode, the Bi/C composite electrode exhibited superior performance due to its much larger surface area. The limit of detection was 0.41 μg/L for lead and 0.49 μg/L for cadmium. Based on this study, we are able to conclude that various types of composite electrodes for electroanalytical applications can be developed with a prudent combination of electrode materials.     

Synthesis and luminescence properties of mesophase silica thin films doped with in-situ formed europium complex

Mesophase silica thin film doped with in-situ formed ternary Eu complex was synthesized by adding ligands (DBM=dibenzoylmethane, phen=1,10-phenanthroline), Eu ions (EuCl₃·6H₂O), and Pluronic P123 triblock copolymer into hydrolyzed tetramethoxy-silane (TMOS). The structure of this inorganic/organic film was characterized as a 2d-hexagonal structure by X-ray diffraction (XRD) and TEM analysis. The excitation spectra (λ_em=612 nm) and emission spectra (λ_ex=325 nm) indicated that the ternary complex, Eu-DBM-phen, was formed in-situ during the formation of the film. The mesophase silica thin film doped with the in-situ formed Eu complex showed a higher quantum efficiency compared to a pure Eu(DBM)₃phen complex and a mesophase silica thin film doped with in-situ formed binary Eu-phen complex.