Using Thermally Crosslinkable Hole Transporting Layer to Improve Interface Characteristics for Perovskite CsPbBr3 Quantum-Dot Light-Emitting Diodes

In this paper, a thermally crosslinkable 9,9-Bis[4-[(4-ethenylphenyl)methoxy]phenyl]-N2,N7-di-1-naphthalenyl-N2,N7-diphenyl-9H-fluorene-2,7-diamine (VB-FNPD) film served as the hole transporting layer (HTL) of perovskite CsPbBr3 quantum-dot light-emitting diodes (QD-LEDs) was investigated and reported. The VB-FNPD film crosslinked at various temperatures in the range of 100~230 °C followed by a spin-coating process to improve their chemical bonds in an attempt to resist the erosion from the organic solvent in the remaining fabrication process. It is shown that the device with VB-FNPD HTL crosslinking at 170 °C has the highest luminance of 7702 cd/m2, the maximum current density (J) of 41.98 mA/cm2, the maximum current efficiency (CE) of 5.45 Cd/A, and the maximum external quantum efficiency (EQE) of 1.64%. Our results confirm that the proposed thermally crosslinkable VB-FNPD is a candidate for the HTL of QD-LEDs.

Pt-Amorphous Barium Aluminum Oxide/Carbon Catalysts for an Enhanced Methanol Electrooxidation Reaction

A new type of amorphous barium aluminum oxide was synthesized using a polyol thermal method involving a mixture with Vulcan XC-72 carbon and supported with 20%Pt catalysts to enhance the activity of a methanol electrooxidation reaction (MOR). The maximum current density, electrochemically active surface area (ECSA), and electrochemical impedance spectra (EIS) of the obtained catalysts for MOR were determined. The MORs of barium aluminum oxide with different calcination temperatures and Ba and Al contact ratios were studied. The MOR of the uncalcined amorphous Ba0.5AlOx catalysts prepared with a mole ratio of 2/1 Ba/Al mixed with Vulcan XC-72 carbon and supported with 20%Pt catalyst (Pt-Ba0.5AlOx/C) was enhanced compared with that of 20%Pt-Al2O3/C and 20%Pt/C catalysts due to its obtained largest maximum current density of 3.89 mA/cm2 and the largest ECSA of 49.83 m2/g. Therefore, Pt-Ba0.5AlOx/C could provide a new pathway to achieve a sufficient electrical conductivity, and possible synergistic effects with other active components improved the catalytic activity and stability of the prepared catalyst in MOR.

Preparation of nickel manganese oxide modified ni foam for anode catalyst direct urea fuel cell

Renewable energy is known as environmentally friendly, such as fuel cells. Nickel is regarded as one of the most promising transition metals to be applied as an electrocatalyst in fuel cell application due to its high catalytic activity. However, the modification of nickel is required to decrease its overpotential. In the present study, the NiMn2O4/Ni-foam was prepared for an anode catalyst in the direct urea fuel cell. The NiMn2O4/Nifoam was synthesized through the hydrothermal method at 180°C for 24 h using Mn(NO3)2.6H2O and Ni(NO3)2.6H2O solutions as the precursors in the presence of urea. During the reaction, Ni foam was placed in the solution to undergo the reaction inside the porous of the Ni-foam. Cyclic voltammetry of the prepared NiMn2O4/Ni-foam electrode in a 2 M KOH solution and 0.33 M urea showed good maximum current density at 206 mA cm-2. Furthermore, the prepared electrode was examined in a direct urea fuel cell with a solution containing 2 M KOH and 0.33 M urea in the anode chamber and a solution containing 2 M H2O2 and 2 M H2SO4 in the anode chamber. A power density of 0.304 mW cm-2 was achieved, indicating the prepared electrode is promising to be developed for a catalyst in a direct urea fuel cell.

Aplicación de nanopartículas de IrO2-WO3 como material anódico para la Reacción de Evolución de Oxígeno en un medio ácido

The hydrogen is an attractive energy carrier and electrolysis of water is the most efficient to H2 production process. The OER in the anode is the limiting reaction being the case of study. In the present work materials based on IrO2 and WO3 were developed in different mechanical mixing 100, 70:30, 50:50, 30:70, respectively, by means of a mechanical mixture from two chemical reduction syntheses. The IrO2 was obtained by 6.25 mM of IrCl3 dissolved in isopropyl alcohol by adjusting the pH with 1M NaOH and a 0.5 mol NH4OH reductant was applied by adjusting a basic pH of 13. The obtained precursor was filtered and calcined at 400 ° C for 1hr. WO3 was obtained from 10mM WCl6 dissolved in isopropyl alcohol and polyethylene glycol, generating a precursor of W (OH)x followed by a calcination process at 500 ° C for 1hr. The material was characterized by electrochemical techniques of CV, LV and EIS. The IrO2-WO3 (50:50) material has lower activation energy of overpotential at room temperature, and a maximum current density close to 20 mA /cm2 at 1.8V vs Hg/Hg2SO4.

Bright Alloy CdZnSe/ZnSe QDs with Nonquenching Photoluminescence at High Temperature and Their Application to Light-Emitting Diodes

Stable luminance properties are essential for light-emitting devices with excellent performance. Thermal photoluminescence (PL) quenching of quantum dots (QDs) under a high temperature resulting from a surface hole or electron traps will lead to unstable and dim brightness. After treating CdZnSe/ZnSe QDs with TBP, which is a well-known passivation reagent of the anions, the excess Se sites on the surface of the QDs were removed and their PL quantum yields (QYs) was improved remarkable. Furthermore, after TBP treatment, the CdZnSe/ZnSe QDs exhibit no quenching phenomena even at a high temperature of 310°C. The electroluminescent light-mitting diodes based on the QDs with TBP treatment also demonstrated satisfied performance with a maximum current density of 1679.6 mA/cm2, a peak luminance of 89500 cd/m2, and the maximum values of EQE and luminescence efficiency are 15% and 14.9 cd/A, respectively. The performance of the fabricated devices can be further improved providing much more in-depth studies on the CdZnSe/ZnSe QDs.

Electrochemical Behaviour of Chalcopyrite in Chloride Solutions

Due to the depletion of oxidized copper ores, it necessitates the need to focus on metallurgical studies regarding sulphide copper ores, such as chalcopyrite. In this research, the electrochemical behaviour of chalcopyrite has been analysed under different conditions in order to identify the parameters necessary to increase the leaching rates. This was carried out through cyclic voltammetry tests at 1 mV/s using a pure chalcopyrite macro-electrode to evaluate the effect of scan rate, temperature, and the addition of chloride, cupric, and ferrous ions. Lastly, the feasibility of using seawater for chalcopyrite dissolution was investigated. An increase in the sweep rate and temperature proved to be beneficial in obtaining highest current densities at 10 mV/s and 50 °C. Further, an increase of chloride ions enhanced the current density values. The maximum current density obtained was 0.05 A/m2 at concentrations of 150 g/L of chloride. An increase in the concentration of cupric ions favoured the oxidation reaction of Fe (II) to Fe (III). Finally, the concentration of chloride ions present in seawater has been identified as favourable for chalcopyrite leaching.

Effect of the Reduction Temperature of PdAg Nanoparticles during the Polyol Process in the Ethanol Electrooxidation Reaction

This work reports the effect of reduction temperature during the synthesis of PdAg catalysts through the polyol process and their evaluation in the ethanol electrooxidation reaction (EOR). The characterization was performed using Transmission Electron Microscopy (TEM) and X-Ray Diffraction (XRD). The electrochemical evaluation for the ethanol electrooxidation reaction was implemented in alkaline medium using chronoamperometry (CA) and cyclic voltammetry (CV). An important effect of the reduction temperature on electroactivity and catalytic stability was observed: both the maximum current density and the catalytic stability were higher in the catalyst synthesized at the highest temperature (135°C). This performance was associated with the extent of the interaction between Pd and Ag which was measured in terms of the structural expansion of Pd.