Polyoxometalates (POMs), as carbon-free metal-oxo-clusters with unique structural properties, are emerging water-splitting electrocatalysts. Herein, we explore the development of cobalt-containing polyoxometalate immobilized over the carbon nanotube fiber (CNTF) (Co4POM@CNTF) towards efficient electrochemical oxygen evolution reaction (OER). CNTF serves as an excellent electron mediator and highly conductive support, while the self-activation of the part of Co4POM through restructuring in basic media generates cobalt oxides and/or hydroxides that serve as catalytic sites for OER. A modified electrode fabricated through the drop-casting method followed by thermal treatment showed higher OER activity and enhanced stability in alkaline media. Furthermore, advanced physical characterization and electrochemical results demonstrate efficient charge transfer kinetics and high OER performance in terms of low overpotential, small Tafel slope, and good stability over an extended reaction time. The significantly high activity and stability achieved can be ascribed to the efficient electron transfer and highly electrochemically active surface area (ECSA) of the self-activated electrocatalyst immobilized over the highly conductive CNTF. This research is expected to pave the way for developing POM-based electrocatalysts for oxygen electrocatalysis.

Two new effective corrosion inhibitors, namely N-(n-octyl)-3-methylpyridinium bromide (Py8) and N-(n-dodecyl)-3-methylpyridinium bromide (Py12), have been presented. The cationic pyridinium-based surfactants were analyzed for the corrosion protection of general purpose steel (EN3B) against a strong corrosive media (3.5% NaCl, pH 1.5). The results of the electrochemical measurements, i.e., Tafel polarization, linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) revealed a mixed-type behavior of both inhibitors, and the maximum inhibition efficiency (IE) achieved with Py8 and Py12 was 85% and 82%, respectively. The process of adsorption of synthesized inhibitors followed the Langmuir adsorption isotherm, and a higher value of Kads highlighted the existence of strong interaction between inhibitors and the EN3B mild steel surface. Furthermore, the values of ΔG°ads were calculated to be –32 kJ mol−1 for Py8 and –33 kJ mol−1 for Py12, indicating the coexistence of both physisorbed and chemisorbed molecules. The surface morphology of EN3B mild steel samples was observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM), where the reduced surface roughness in the presence of Py8 and Py12 in chloride media further supported the evidence of an efficient inhibition process. Density functional theory (DFT) calculations reveal excellent correlation with the experimental results, with Py8 showing superior corrosion inhibition potential, signifying that the alkyl chain length and intramolecular charge transfer are crucial factors in deciding the inhibition performance of the synthesized cationic surfactants. Furthermore, this study proposes the mechanism for the adsorption of the surfactant-based inhibitors over the EN3B mild steel surface, which leads to the formation of an effective and protective anticorrosive film.

This work presents a comparative experimental and theoretical study on the use of polyaniline and its derivative, poly o‐toluidine, as effective electrochemical sensor for the detection of hydrazine. Hydrazine is a toxic analytic with numerous adverse health effects on the human brain, liver and nervous system. The conducting polymers polyaniline (PANI) and poly o‐toluidine (POT) were synthesized by oxidative polymerization and characterized through x‐ray Diffraction, FT‐IR, and UV–Visible Spectroscopy. Electrochemical studies performed on the polymer modified glassy carbon electrode (GCE) using cyclic voltammetry and differential pulse voltammetry reveal strong interaction between hydrazine and the polymer through irreversible charge transfer. The oxidation current was seen to increase with increasing hydrazine concentration. The diffusion coefficients were found to be 1.89 × 10−5 cm2/s and 2.89 × 10−6 cm2/s for PANI and POT, respectively. PANI and POT based sensors show a limit of detection of 1 μM and 5.13 mM, respectively in the linear concentration range of 1–9 mM. Density functional studies on the PANI‐hydrazine and POT‐hydrazine complexes show enhanced intermolecular charge transfer from nitrogen lone pairs in hydrazine to the polymer backbone clearly identifying the donor and acceptor moieties. PANI based electrochemical sensor is shown to have a higher sensitivity for hydrazine compared to POT, where the sensing interaction is hindered by the bulky methyl group in ortho position.