Effect of Surface Composition on Electrochemical Oxidation Reaction of Carbon Monoxide and Ethanol of PtxRh1−x Solid Solution ElectrodesRead the full article
International Journal of Electrochemistry publishes research on all aspects of electrochemistry including fundamental electrochemical processes, new electrochemical techniques and the applications of electrochemistry in analytical determination.
Professor Kenneth Ozoemena, the journal’s Chief Editor, is based at the University of the Witwatersrand in South Africa. His current research activities include materials synthesis and characterisation, electroanalytical chemistry, electrocatalysis and electrochemical energy conversion and storage.
Latest ArticlesMore articles
Development and Characterization of a New Solid Polymer Electrolyte for Supercapacitor Device
In this study, solid polymer electrolytes (SPEs) are based on methylcellulose (MC) used as a polymer host and sodium iodide (NaI) as a dopant. The SPE films are developed using different contents of ethyl carbonate (EC) as a plasticizer to enhance their properties via a solution casting method. The surface morphology of SPE films is shown using polarized optical microscopy (POM), which indicates the existence of amorphous patches due to the plasticizing effect of EC. The creation of a complex between MC, NaI, and EC was confirmed by Fourier transform infrared (FTIR) spectra. A tiny amount of EC applied to the MC-NaI polymer salt matrix increases the number of charge carriers and improves ionic conductivity. The ionic conductivity of the generated polymer electrolytes is examined using electrochemical impedance spectroscopy (EIS). The high-ion conducting PE of 5.06 × 10−3 S·cm−1 was found with the mixture MC + 50 wt% NaI + 10 wt% EC (room temperature). The linear speed voltammetry (LSV) test shows that the optimized polymer electrolyte can withstand decomposition up to 2.5 V. The optimized sample transmission numbers were calculated using a TNM (transference number measurement) approach, and the results show that 99% of the ions contribute to the conductivity, compared to only 1% of the electrons. A solid-state electrical double-layer capacitor (EDLC) was fabricated using the highest ion-conductive polymer electrolyte and graphene oxide (GO)-based electrodes. The galvanostatic charge-discharge (GCD) technique was performed, and the GCD graph shows the behavior of an ideal capacitor with a less Faradic process and a low ESR value. The GO-based cell’s columbic efficiency is 100%, and the system delivers the charge for a long duration. The EDLC cell demonstrates outstanding cyclability. The specific capacitance of the EDLC cell incorporated with MC + 50 wt. % NaI + 10 wt. % EC was found to be 154.66 F/g.
Size-Dependent Chlorinated Nitrogen-Doped Carbon Nanotubes: Their Use as Electrochemical Detectors for Catechol and Resorcinol
In this study, various-sized nitrogen-doped carbon nanotubes (NCNTs) were fabricated by varying the concentration of chlorine in the feed. The diameter of the NCNTs was found to influence the sensing ability of the nanomaterials when coated onto the glassy carbon electrode (GCE) and used for the detection of catechol (CC) and resorcinol (RS). Larger diameter NCNTs (denoted NCNTs (2 : 1)) were produced when a low concentration of chlorine was added into the acetonitrile feed, whereas smaller diameter NCNTs (denoted NCNTs (1 : 2)) were produced when a large concentration of chlorine was added. This investigation revealed that the addition of controllable amounts of chlorine during the fabrication of NCNTs led to the creation of nanostructures with different properties. The greatest current response which was evidenced by an enhanced anodic peak of CC and RS was obtained when GCE was coated with NCNTs (2 : 1), and this was attributed to their large diameter and high graphitic nature which facilitated electron transfer as evidenced by scanning electron microscopy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) analysis. A linear response was obtained when varying the concentration of both CC and RS, with the limits of detection of about 0.059 μM (CC) and 0.034 μM (RS) (3S/M) obtained.
Enabling the Electrochemical Performance of Maricite-NaMnPO4 and Maricite-NaFePO4 Cathode Materials in Sodium-Ion Batteries
NaMnPO4 and NaFePO4, polyanion cathode materials, exist in two different phases maricite/natrophilite and maricite/olivine, respectively. Both natrophilite NaMnPO4 and olivine NaFePO4 are electrochemically active and possess a one-dimensional tunnel for sodium-ion migration; however, these two phases are thermodynamically unstable. Therefore, they can be synthesized through an electrochemical route. On the contrary, maricite (m)-NaMnPO4 and maricite (m)-NaFePO4 are thermodynamically stable forms but have a huge activation energy of their diffusion pathways for sodium extraction and insertion in the crystal structure, which hinders electrochemical reactions. Therefore, the electrochemical behaviour of commercial m-NaMnPO4 and m-NaFePO4 has been studied to find a way for enabling them electrochemically. Ball milling and thermal/mechanical carbon coating are employed to reduce the particle size to enhance the electrochemical performance and shorten the diffusion pathway. Moreover, ball milling leads to defects and partial phase transformation. The electrochemical performance of milled-coated NaMnPO4 and NaFePO4 has been thoroughly investigated and compared. The phase transition of NaFePO4 is revealed by a differential scanning calorimeter. As a result, the achievable capacities of both cathode materials are significantly enhanced up to ∼50 mAh.g−1 via the particle size reduction as well as by carbon coating. However, the side reactions and agglomeration problems in such materials need to be minimized and must be considered to enable them for applications.
Electrooxidation and Development of a Highly Sensitive Electrochemical Probe for Trace Determination of the Steroid 11-Desoxycorticosterone Drug Residues in Water
Anabolic-androgenic steroids (AASs), a class of compounds frequently misused by competitors and unfortunately by the general population, have lately attracted international attention. Thus, extraordinary demands for developing low cost, precise, rapid, and facile protocols for detection and/or determination of AAS have arisen. Hence, the current strategy explores for the first time the redox features of 21-hydroxypregn-4-ene-3, 20-dione, namely, 11-desoxycorticosterone (DCS) AA drug steroid at a glassy-carbon electrode (GCE) in a wide pH range (pH 2.0–10.0) by adsorptive differential pulse-anodic stripping voltammetry (DP- ASV) and cyclic voltammetry (CV). At pH 2, DP-ASV and CV at the optimized pH 2–3 displayed an irreversible anodic peak at 0.4 V versus Ag/AgCl electrode. The dependency of the anodic peak current of the CV at 0.4 V at various concentrations and scan rate of the DCS drug was characteristic of an electrode-coupled electron transfer of EE type mechanism. At the optimized parameters, the proposed strategy allowed quantification of DCS in the concentration range 2.5 -13.19 nM (0.83-4.36 ng mL−1) with satisfactory limits of detection (LOD) and quantization (LOQ) of 9.3 × 10−1 nM (3.1 × 10−1 ng mL−1) and 3.1 nM (1.02 ng mL−1), respectively. A relative standard deviation (RSD) of ±3.93% (n = 5) at 4.0 ng mL−1 DCS was achieved. The established probe was fruitfully employed and validated for trace determination of DCS residues in environmental water. The interference of several common diverse species on DCS sensing was insignificant revealing good selectivity. The established probe exhibited good sensitivity, selectivity, precision, and accuracy, short analytical time, and low cost compared with the reported methods, for DCS determination.
A Highly Sensitive Electrochemical Sensor Based on Electrocatalytic Reduction Effect of Cu2+ on Trace Determination of Malathion in Soil and Other Complex Matrices
The current strategy reports a highly sensitive and selective square wave-cathodic stripping voltammetric protocol for malathion determination. The established method was based on the controlled adsorptive accumulation of malathion in the presence of Cu2+ ions in an aqueous solution of pH 2 onto the hanging mercury dropping electrode (HMDE) and measuring the resulting cathodic peak current of the adsorbed species at −0.42 V versus Ag/AgCl electrode. The low limits of detection (LOD) and quantification (LOQ) of malathion of the assay were estimated to be 3.1 × 10−10 and 1.03 × 10−9 M with a linear dynamic range of 1.03×10−9 – 2.0 × 10−7 M, respectively. The method was satisfactorily applied and validated for malathion determination in environmental samples. The experimental Student texp and Fexp values did not exceed the tabulated ttab (2.78) and Ftab (6.39) at 95% (P = 0.05) confidence (n = 5), confirming the precision and independence on the matrix. The developed sensing platform for the detection of malathion shows superior performance to conventional electrochemical methods. The proposed sensor offered simple, economical, reproducible, and applicable approach for the determination of malathion in environmental samples.
Detection of Selenium and Nickel Metal Ion in Water Using Mn3O4-Cn-Modified Electrode
The present study reports the design of the Mn3O4-Cn electrode and its use for simultaneous detection of selenium and nickel in water. The designed electrode can be used as a convenient electrochemical device for on-site testing of Se (IV) and Ni (II) levels in affected regions. The best responses are obtained with 0.1 M phosphate buffer saline (PBS) and 5 mM Fe (CN)6 as supporting electrolyte. The scan rate and the number of cyclic repetitions have a great effect on peak shape and intensity. It is seen from our study that peak intensity is directly proportional to Se (IV) and Ni (II) concentrations in the range of 5 to 250 µg/L (correlation coefficients 0.952 and 0.984) when the optimized parameters are used. The detection limit of 0.533 µg/L Se (IV) and 0.718 µg/L for Ni (VI) with a response time of 18 s for 5–250 µg/L concentration is obtained, respectively. Enhanced analytical results for different water samples establish that the proposed method is appropriate for Se (IV) and Ni (II) detection. FESEM images confirm the Mn3O4-Cn nanocomposite formation on the electrode.