Ionics

“Vertically aligned graphene nanosheets” are a type of graphitic carbon nanostructure with an interconnected network of perpendicularly aligned graphene nanosheets. In this study, the thin films of this material are deposited on stainless steel substrates using electron cyclotron resonance–based plasma-enhanced chemical vapor deposition. The variation of the electrochemical performance of the vertically aligned graphene nanosheets with the change in surface morphology is analyzed. The samples with different surface geometries offer different values of specific capacitances. The sample with nanopores between the graphene nanosheets of largest diameter and of most open nature delivers the highest specific electrode capacitance of 0.98 mF cm−2 (11.09 F cm−3) at a current density 0.88 mA cm−2 while the corresponding value for the sample with the smallest gap between nanosheets is of 0.49 mF cm−2 (6.67 F cm−3). The results point out at a direct correlation between surface morphology and electrochemical performance of the material.

Polyvinyl alcohol (PVA)-based proton conducting polymer electrolytes have been prepared by the solution cast technique. The conductivity is observed to increase from 10−9 to 10−4 S cm−1 as a result of orthophosphoric acid (H3PO4) addition. The plot of conductivity vs temperature shows that a phase transition occurred at 343 K in the sample PVA-33 wt% H3PO4. The β-relaxation peak is observed at 313 K. The glass transition temperature of PVA-33 wt% H3PO4 is 343 K. Orthophosphoric acid seems to play a dual role, i.e., as a proton source and as a plasticizer. The ac conductivity σ ac = Aω s was also calculated in the temperature range from 303 to 353 K. The conduction mechanism was inferred by plotting the graph of s vs T from which the conduction mechanism for sample PVA-17 wt% H3PO4 was inferred to occur by way of the overlapping large polaron tunneling (OLPT) model and the conduction mechanism for the sample PVA-33 wt% H3PO4 by way of the correlated barrier height (CBH) model.

This work is a continuation of previous studies concerning the behaviour of ferrocene in a mixture of two insoluble liquids. In this paper, the system reached partition equilibrium after approximately 175 min. Electroanalytical studies were executed, and a high reproducibility was observed in a range of concentrations from 2 to 14 × 10−5 mol L−1 of ferrocene that escaped from the oil to the aqueous phase. Because ferrocene most likely occurs only in the monomeric form in both the oil and aqueous phases, it was possible to predict a partition coefficient (log P(oil/water)) of ferrocene of approximately 2.4.

In this letter, we demonstrated the growth of different morphologies of silver submicrostructures influenced by ortho-phenylenediamine (oPD) concentrations and pH values. The results indicated that concentration ratios of the oPD to Ag+ colloids in the solution determine the final morphology of the products. oPD is found to act as a stabilizer as well as reduction agent. Particle shape ranges from sheets to spheres, increasing with molar ratio. Meanwhile, morphologies of structures and the time consumption to form particles both depend on pH values. We could obtain plates, polyhedrons, spheres, and dendrites through adjusting pH from 1.3 to 12.3. A mechanism is proposed to interpret the controlled synthesis of silver submicrostructures.

A simple and rapid method was employed for the modification of carbon paste electrode with iron nanoparticle-decorated multiwalled carbon nanotubes (MCPE/Fe-MWCNTs). The synergistic effect of iron nanoparticle and multiwalled carbon nanotubes results in the electrocatalytic oxidation of folic acid (FA). MCPE/Fe-MWCNTs were characterized by FESEM by recording surface morphological images; the elemental analysis of the electrode was carried out by EDX and electrochemical impedance spectroscopy to investigate surface-interface properties between solid electrode surface and the solution. The electronic transitions during the electrochemical oxidation of FA were investigated using spectroelectrochemical data. Cyclic voltammetry and differential pulse voltammetric techniques were used for the qualitative and quantitative analysis of FA respectively at physiological pH. MCPE/Fe-MWCNTs produced a linear response to FA over a wide concentration range with a detection limit of 2.4 ± 0.9 nM (S/N = 3). The fabricated sensor was successfully utilized as an effective tool for the determination of FA in food samples, human blood serum, and pharmaceuticals.

The lithium trivanadate Li1.2V3O8 has been investigated during the past decade as a very promising positive electrode material for lithium batteries due to its high theoretical capacity of 360 mAh/g. However, the experimental capacity remains generally much lower than (about half) the theoretical value. To increase electrode cycling performance in batteries, most researchers generally focus their work on the active material optimisation. Here we show that the polymeric binder of the composite electrode may have an important role on the electrode performance. We describe a new tailored polymeric binder combination with controlled polymer-filler (carbon black) interactions that allows the preparation of new and more efficient electrode architecture. Using this polymeric binder, composite electrodes based on Li1.2V3O8 display a room-temperature cycling capacity of 280 mAh/g (C/5 rate, 3.3-2V) instead of 180 mAh/g using a Bellcore-type composite electrode (PLIonTM technology). We have coupled SEM observations, galvanostatic cycling and electrochemical impedance spectroscopy in order to define and understand the impact of the microstructure of the composite electrode on its electrochemical performance. Derived from these studies, the main key factors that provide efficient charge carrier collection within the composite electrode complex medium will be discussed. Present findings open up new and attractive prospects for electrode performance optimisation.