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Considerable interest in urea electrooxidation reaction has developed recently because of possible generation of hydrogen and in direct urea fuel cell applications. Nickel and nickel-containing catalysts are the preferred electrode materials because of their efficient activity for this reaction. This work investigates a novel platform composed of a conducting poly(aniline) modified with lanthanumnickel-based oxides/reduced graphene oxide as an electrocatalyst for urea electrooxidation in alkaline medium. The catalyst was prepared using a one-step and energy-saving procedure with graphene oxide as a substrate. The glassy carbon electrode modified with this catalyst exhibits an exceptional high specific current activity of 342 mA mg −1 cm −2 in 0.33 M urea/1.0 M KOH and reaches 615 mA mg −1 cm −2 in 0.33 M urea/3.0 M KOH. The catalyst was studied using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy showing long term stability and resistance against fouling. The structure and morphology of the resulting material was characterized with XRD, SEM and EDAX analyses.

A self-assembly Pd-Schiff base complex was synthesized and used as an electrochemical sensor in phosphate buffer solution, where it enhanced the electrocatalytic activity toward the paracetamol detection. The Schiff base {(HL) = (4-(((Z)-3-(hydroxyimino) butan-2-ylidene) amino)-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one)} was selected to prepare Pd-based complexes due to its high antimicrobial activity. A linear calibration curve was constructed using GC/Pd-SB in paracetamol concentration range of 1–50 μM and its detection limit was calculated as 0.067 μM. The modified electrode, GC/Pd-SB, could successfully determine the paracetamol concentration in human blood serum and commercial drug tablets with high sensitivity. The prepared metal complex was characterized using techniques, namely, X-ray diffraction (XRD) and scanning electron microscope (SEM). In addition, electrochemical studies were performed using different electrochemical techniques like cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). DFT calculations were used to estimate the equilibrium geometry, molecular orbital, ground-state properties, and interaction energy between paracetamol and palladium. Graphical Abstract

In this work, we are enhancing the catalytic activity of the urea electrooxidation (UEO) process by using the composite of polyaniline (Pani), nickel oxide (NiO), and polymorphs of manganese oxide (MnOx) based on a graphite electrode. The hydro‐gel method was used to prepare catalyst suspension with different ratios from NiO and MnOx. The chemical structures and surface morphology were characterized by employing the IR, XRD, and SEM/EDEX techniques. The catalytic activity of four modified electrocatalysts G/Pani/NiMn1, G/Pani/NiMn2, G/Pani/NiMn3, G/Pani/NiMn4 was investigated using cyclic voltammetry, chronoamperometry, and electrochemical impedance. The kinetic parameters such as diffusion coefficient, Tafel slope, charge transfer coefficient, and surface coverage were calculated to choose the best electrocatalysts toward UEO in alkaline solution. The anodic current of new electrodes achieved about 16 mA.cm−2 at potential of 550 mV (vs. Ag/AgCl). Density functional theory studies (DFT) have been carried out to assess the adsorption energy between polyaniline (Pani) and the metal oxides.

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