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For the advancement of electrochemical energy conversion and storage technologies, bifunctional electrocatalysts are crucial for efficiently driving both the oxygen evolution (OER) and reduction reactions (ORR). Cobalt‐based spinel oxides are a class of promising bifunctional electrocatalysts. However their low electrical conductivity and stability may hinder further improvement. A novel composite material composed of NiCo2O4 nanoparticles integrated with emerging two dimensional MXene nanosheets (NiCo2O4/MXene) was developed. The successful integration of NiCo2O4 with MXene brings about a number of attractive structural features. This includes synergistic effects between NiCo2O4 and MXene, highly accessible surface areas, complete exposure of numerous active sites, and excellent electronic conductivity, all of which collectively contribute to the desirability of composite material for OER and ORR. The synthesized NiCo2O4/MXene composite showed extraordinary OER electrocatalytic activity with a lower overpotential of 360 mV at a current density of 10 mA/cm2, and a small Tafel slope of 64 mV/dec compared to NiCo2O4, MXene and NiCo2O4+MXene (physically mixed). Additionally, NiCo2O4/MXene displays an ORR limiting current density of −4 mA/cm2 and exhibited highest onset potential and half wave potential of 0.92 V and 0.72 V vs. RHE, respectively, for the ORR in alkaline media compared to NiCo2O4, MXene and NiCo2O4+MXene (physically mixed). [ABSTRACT FROM AUTHOR]

TiO2/RGO nanocomposites were synthesised via a simple one-pot hydrothermal method. The influence of different reducing agents on the composite preparation was systematically studied. Electrochemical sensors were developed using the synthesised TiO2/RGO nanocomposites as modifiers in a carbon paste electrode. The nanocomposite formed using sodium borohydride as the reducing agent exhibited superior electrochemical properties compared to other modified electrodes. The electrochemical sensing properties of the modified electrodes were studied using different electrochemical techniques, namely, cyclic voltammetry, differential pulse voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The electrochemical surface areas of all the modified electrodes were significantly improved, and their charge transfer resistance was substantially reduced by modification. Cyclic voltammetry studies revealed the quasi-reversible nature of dopamine and irreversible nature of serotonin (SER) and tryptophan (TRP) at neutral pH. Differential pulse voltammetric studies using the modified electrodes were utilised for ultra-trace level sensing of neurotransmitters. Detection limits as low as 0.18 nM, 0.32 nM and 0.4 nM for serotonin (SER), dopamine (DP) and tryptophan (TRP) were achieved. The modified electrodes exhibited a wide linear dynamic range, which allowed the simultaneous determination of the biomolecules SER, DP and TRP. Real sample analysis, stability measurements and reproducibility tests further demonstrated the practical applicability of the developed electrochemical sensor. [ABSTRACT FROM AUTHOR]

A novel electrochemical sensor for dopamine (DA) in the presence of serotonin (ST) was fabricated by modifying a glassy carbon electrode with BaMnO3 and super P carbon black. The modifier, BaMnO3 was synthesized by a co-precipitation method and subsequent calcination. The formation of a pure crystalline form of BaMnO3 was ensured during synthesis and verified by characterization techniques such as powder X-ray diffraction, infrared spectroscopy, Raman, thermogravimetry, Ultraviolet-visible spectroscopy, scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray analysis. 5 mg of BaMnO3 was sufficient to allow sensor development. The sensor was characterized by electrochemical impedance spectra and cyclic voltammetry studies. The mechanism of oxidation of DA and ST at the sensor is proposed based on experimental findings. Trace level determination of DA and ST was successfully carried out using the sensor. The electrochemical oxidation of DA and ST are completely independent. The limit of detection of DA and ST are 50 pM and 5 nM respectively. The DA has a linear dynamic range (LDR) of 0.1 to 300 nM and ST has a LDR of 10 to 2300 nM. The practical utility of the sensor was demonstrated by calculating the recovery of DA in human blood serum and urine. [ABSTRACT FROM AUTHOR]