Journal of Applied Electrochemistry

In this study, TiO2 and WO3 nano-sized particles were chosen as metal oxides to generate anticorrosive Zn composite coatings. The effects of type and amount of oxide particles on the microstructure and corrosion behavior of composite coatings on St 37 steel were investigated. In the first stage of study, electrochemical measurements were carried out in 3.5 % NaCl solution to determine the corrosion behavior of uncoated, Zn-coated, Zn–TiO2, and Zn–WO3 nanocomposite-coated steel samples. In the second stage, the time-dependent surface degradations of all samples immersed into NaCl solution were characterized using scanning electron microscope to observe the protective effect of nanoparticles. It was found that WO3 oxide-dispersed composite coating exhibited superior corrosion resistance.

Impedance spectroscopy, unlike large signal methods, allows the diffusion coefficient of an inserted species to be determined as a function of the electrode potential. The expression for the restricted linear diffusion impedance may be modified to empirically account for the difference of the electrochemical system behaviour from the ideal. It is then possible to estimate the diffusion coefficient of the inserted species from characteristic frequencies on the Nyquist diagrams and/or from the frequencies corresponding to the intersection of the asymptotes of the log (−Im Z), log f graphs. These estimations are independent of assumptions concerning the active area of the electrode. The method has been applied to the study of hydrogen insertion in H x Nb2O5.

In this article, we report the synthesis of 1,2-dimethyl-3-(3-hydroxypropyl) imidazolium dicyanamide ionic liquid and its used as a reaction medium for low-temperature synthesis of triclinic LiVPO4F electrode material. Structural and morphological features of LiVPO4F were characterized using X-ray diffraction and scanning electron microscopy techniques. The electrochemical studies have been investigated using cyclic voltammetry, galvanostatic charge/discharge studies, and electrochemical impedance spectroscopic techniques. The ionothermally obtained LiVPO4F is modified to LiVPO4F/f-graphene composite electrode to obtain high specific capacity, better rate performance, and longer cycle life. Even after 250 cycles, the LiVPO4F/f-graphene composite electrode exhibited a specific capacity more than 84 % with good reversible de-intercalation/intercalation of Li-ions. This article also provides the comparative electrochemical performances of LiVPO4F/f-graphene composite, LiVPO4F/carbon, and LiVPO4F/graphene composite electrodes in a nonaqueous rechargeable Li-ion battery system.

The solution of the Nernst-Planck equation for the electropolishing of metals is presented. The migration and diffusion equations are solved for the cases where the metal ion is transported independently of the anion of the electrolyte and when ion pairing occurs. It is concluded that under polishing conditions, the surface concentration of acid is decreased by the salt solubility. It is shown that this has important practical consequences for defining the conditions required for electropolishing and in the selection of the acid used.

Three types of iron–nitrogen-containing non-noble metal catalysts, supported on an ultrasonic spray pyrolysis mesoporous carbon (USPMC), a hollow core mesoporous shell carbon (HCMSC), and a standard carbon (Ketjen Black CJ600, KB), respectively, are synthesized using a wet-impregnation method. The morphologies and structure as well as composition of the synthesized carbon supports and their corresponding supported Fe–N X catalysts (namely Fe–N X /USPMC, Fe–N X /HCMSC, and Fe–N X /KB, respectively) are physically characterized using EDX, SEM, FESEM, and BET analysis, respectively. The catalytic activities of these three electrocatalysts toward oxygen reduction reaction (ORR) are measured using rotating disk electrode technique in O2-saturated 0.5 M H2SO4 solution. The catalyzed ORR exchange current densities are also obtained using the Tafel method based on the measured data. Among these three electrocatalysts, Fe–N X /HCMSC can give the best ORR performance, which is correlated to its higher nitrogen, mesopore, and micropore contents, compared to the other electrocatalysts. It is rationalized that the performance improvement of these electrocatalysts may be achieved as long as an optimal relationship among mesopores, micropores, and even macropores for increasing both ORR kinetics and reactant gases accessibility to the active sites can be found.

Photocatalytic processes taking place on TiO2 have been widely employed and investigated. However, nitrogen-containing substances have not received the same attention as other substrates. Mineralization of such compounds is expected to lead to the formation of N2 gas, ammonium and/or nitrate ions through photooxidative and/or photoreductive pathways. Herein, we will focus the attention on how the chemical structure may influence both the ratio and the extent of formation of the inorganic nitrogen. This review will consider heteroaromatic compounds, containing two or three-nitrogen in the ring, and small molecules, that could be formed as intermediate during the degradation of more complex substrates (i.e. pesticides), such as amino-alcohols, and molecules containing amide groups and nitriles. The fate final of the nitrogen in all these structures has been rationalized on the basis of the nature of N–N and C–N bonds in which the organic nitrogen is involved.

An electrochemical device for the reduction of CO2 back to liquid fuels is here presented. The key of this novel electrocatalytic approach is the design and development of the gas diffusion membrane (GDM), which is obtained by assembling (i) a proton selective membrane (Nafion), (ii) a nanocomposite electrocatalyst based on metal-doped conjugated microporous polymer (CMP) and (iii) a C-based support working as the gas diffusion layer. CMP is a very attractive material able to adsorb CO2 selectively with respect to other gases (such as H2, O2, N2, etc.), also in mild conditions (r.t. and atmospheric pressure). Particularly, tetrakis-phenylethene conjugated microporous polymer (TPE-CMP) was synthesized through Yamamoto homo-coupling reaction. TPE-CMP was modified by depositing noble (Pt) and non-noble (Fe) metal nanoparticles to create the active catalytic sites for the process of CO2 reduction directly on the polymer surface where CO2 is adsorbed. The metal-doped TPE-CMP electrocatalysts were fully characterized by infrared spectroscopy (IR), thermo-gravimetric analysis (TGA) and transmission electron microscopy (TEM). Then, the as-assembled GDM was tested in our homemade semi-continuous three-electrode electrochemical cell working in gas phase at 60 °C, coupled with a cold trap for the accumulation of the liquid products. Results showed the better performances of the metal-doped TPE-CMP in terms of total productivity (C1–C8 oxygenates) with respect to other kinds of materials that do not show high CO2 adsorption capacity.

This study investigates the fouling of anion exchange membrane by organic foulants in fresh water, which is one of the causes of performance degradation of reverse electrodialysis (RED). Three organic foulants, namely sodium alginate (SA), humic acid (HA), and sodium dodecylbenzene sulfonate (SDBS) are selected and the behavior of adsorption fouling of the selected organic foulants is monitored, analyzed and identified using physicochemical (ion exchange capacity (IEC), water uptake (WU)) and electrochemical (permselectivity, electrochemical impedance spectroscopy (EIS), j-V and j-P plots) methods. Compared to the pristine membrane, the resistance of anion exchange membrane increases and the selective permeability, IEC, and WU decrease after fouling of the membrane, which in turn affects the RED cell performance. SDBS, an aromatic substance, shows a higher adsorption capacity as compared to the other two foulants, and therefore causes severe degradation. Among the two aliphatic substances, namely, HA and SA, HA exhibited higher adsorption capacity than SA because it has fewer carboxylic groups. To summarize, the degradation behavior of the anion exchange membrane was clearly different based on the characteristics of each organic foulant.