Physicochemical and electrochemical properties of Gd3+-doped ZnSe thin films fabricated by single-step electrochemical deposition process

2021

J. Phys. Chem. Lett.

The temperature dependence of the electrical conductivity of Pt nanotubes (NTs) with different thicknesses synthesized by a wetting method using an Al2O3 membrane was studied. Pt NTs exhibited circular pores with an average diameter of ∼200 nm. From XRD, the prepared Pt NTs displayed a cubic crystal structure. Pt metal was identified based on the binding energy peak at 71 eV via XPS analysis. Pt NTs with thicknesses of 5 and 12 nm behaved like a semimetal, whereas Pt NTs with thicknesses of 25 and 29 nm showed normal metallic electrical conduction characteristics. This metal-to-semimetal transition was induced as the thickness and grain sizes of the Pt NTs were decreased. The critical metal-to-semimetal transition temperature of Pt NTs with average tube wall thicknesses of ∼5 nm was measured at ∼37 °C. However, the critical temperature could not be measured for NTs with a thickness of 12 nm. It is assumed that the critical temperature would be far below 0 °C. This transition behavior resulted from both a discontinuity in the density of states due to the quantum confinement effect and the increased energy barrier for conduction of electrons accompanied by the increased density of grain boundaries. These results presented here signify a vital step in the direction of realizing high-performance nanoelectronic devices.

mentioning

confidence: 99%

Metal-to-Semimetal Transition in Platinum Nanotubes: Dependence on Thickness

2021

J. Phys. Chem. Lett.

“…7 (a & b) showed that the cathodic peak current of hydrogen adsorption and the anodic peak current of hydrogen oxidation were proportional to the sweep rate. This proved that the hydrogen adsorption and hydrogen oxidation controlled the whole reaction [26][27][28].…”

Section: Hydrogen Storage Of Carbon Nanotubes By Electrochemical Measmentioning

confidence: 66%

Solvothermal/Hydrothermal Manufacturing of Carbon Nanotubes for Hydrogen storage: A Comparative Study

Namitha

Radhika

et al. 2020

Phys. Chem. Solid St.

Investigation on the manufacturing of multi-walled carbon nanotubes (MWNTs) by solvothermal and hydrothermal procedure and the electrochemical behavior of these nanostructured electrode materials for hydrogen storage has been presented. The physical and morphological properties of prepared carbon nanotubes were studied by X-ray diffraction (XRD), Scanning, and Transmission electron microscopy (SEM and TEM). Furthermore, the electrochemical properties of MWCNTs were revealed by galvanostatic charge-discharge and measurement of cyclic voltammetry and the results revealed that both MWNTs exhibited higher electrochemical capacitance and stable cycling performance. Interestingly, MWNTs synthesized from hydrothermal procedure shows an extreme discharge capacity of 423 mAh/g, concerning hydrogen storage of ∼ 1.5 wt%, and MWNTs synthesized from solvothermal procedure shows a capacity of discharge 394.8 mAh/g. corresponds to ∼ 1.4 wt%, was attained reproducibly at 25 °C for about 100 mg of MWCNTs. This outcome infers that the MWNTs are extremely assuring electrochemical hydrogen storage materials for PEM fuel cells and rechargeable batteries.

“…The voltammogram suggests that the reduction peaks are due to the reduction of dissolved O2 to HO2and OH -, respectively. This indicates that charge is stored in the 8, the maximum hydrogen adsorption of 800 mAh g -1 was achieved which corresponds to 2.8 wt % of hydrogen [44][45][46]. Для процесу ефективного виробництва вуглецевих нанотрубок (УНТ) за відносно низьких температур припускається, що цікавою є суміш d-елементів, таких як залізо, нікель та кобальт, через високий вихід та низьку температуру синтезу (220 -250°С).…”

Section: Resultsunclassified

Manufacturing and Processing of Carbon Nanotubes for H2 Storage

Namitha

Radhika

et al. 2021

Phys. Chem. Solid St.

In pursuit of manufacturing of carbon nanotubes (CNTs) in good yield at lower temperatures, a mixture of d-block elements such as Iron, Nickel, and Cobalt was expected to be advantageous because of the high yield and low temperature (at 220 - 250° C) synthesis. The physical state and aggregation of these catalyst particles in the reaction medium have been found to play an interesting role in obtaining CNTs at better yield. Carbon nanotubes have been successfully produced by an uncomplicated two-step solvothermal method between sodium and dichlorobenzene via Ni/Fe/Co as catalyst precursor. The dependence of yield of CNTs on the catalyst system was determined via different ratios of catalysts and at various other experimental conditions such as different heating temperatures, different durations of heating. The X-ray powder diffraction study has indicated the graphite kind of the products. Microscopic characterizations (SEM and TEM) implied us the diameters of carbon nanotubes are 10-14 nm. Raman spectroscopy shows the presence of graphitized carbon in carbon nanotubes. Significant influence by the heating temperature and heating duration has been observed on the product yield.