Nickel vanadate nitrogen-doped carbon nanocomposites for high-performance supercapacitor electrode

A nickel-vanadium-based bimetallic precursor was produced using the polymerization process by urea-formaldehyde copolymers. The precursor was then calcined at 800 °C in an argon ambiance to form a Ni3V2O8-NC magnetic nanocomposite. Powerful techniques were used to study the physical characteristics and chemical composition of the fabricated Ni3V2O8-NC electrode. PXRD, Raman, and FTIR analyses proved that the crystal structure of Ni3V2O8-NC included N-doped graphitic carbon. FESEM and TEM analyses imaging showed the distribution of the Ni3V2O8 nanoparticles on the layered graphitic carbon structure. TEM images showed the prepared sample has a particle size of around 10-15 nm with an enhanced active site area of 146 m2/g, as demonstrated by BET analysis. Ni3V2O8-NC nanocomposite exhibits magnetic behaviors and a magnetization saturation value of 35.99 emu/g. The electrochemical (EC) studies of the synthesized Ni3V2O8-NC electrode proceeded in an EC workstation of three-electrode. In a 5 M potassium hydroxide as an electrolyte, the cyclic voltmeter exhibited an enhanced capacitance (CS) of 915 F/g at 50 mV/s. Galvanic charge-discharge (GCD) study also exhibited a superior capacitive improvement of 1045 F/g at a current density (It) of 10 A/g. Moreover, the fabricated Ni3V2O8-NC nanocomposite displays a good power density (Pt) of 356.67 W/kg, improved ion accessibility, and substantial charge storage. At the high energy density (Et) of 67.34 W h/kg, the obtained Pt was 285.17 W/kg. The enhanced GCD rate, cycle stability, and Et of the Ni3V2O8-NC magnetic nanocomposite nominate the sample as an excellent supercapacitor electrode. This study paves the way for developing effective, efficient, affordable, and ecologically friendly electrode materials.

Ultrasonic assisted synthesis of Ni3(VO4)2-reduced graphene oxide nanocomposite for potential use in electrochemical energy storage

In the present study, Ni₃(VO₄)₂-reduced graphene oxide (NV/RGO) nanocomposite was synthesized for energy storage purpose. To this end, a mixture containing RGO nanosheets, Ni (CH₃COOH)₂ and Na₃VO₄ mixture was prepared under probe-type ultrasonic irradiation with frequency of 20 KHz and the optimized power of 100 W. The Raman and energy-dispersive X-ray spectroscopies confirmed the presence of RGO nanosheets, nickel and vanadium elements in the NV/RGO, respectively. In addition, field emission-scanning electron microscopy (FESEM) data showed the formation of the NV nanoparticles on the RGO nanosheets. NV/RGO nanocomposite was pasted on nickel foam (NF) and its performance was investigated in energy storage using a three-electrode cell containing 6 M KOH. In cyclic voltammogram of NV/RGO/NF, redox peaks for Ni (II)/Ni (III) with intensities higher than that for NV/NF were observed which confirms the synergistic effect of RGO on the performance of NV. Chronopotentiometry data revealed that the NV/RGO/NF electrode exhibits high capacity of 117.22 mA h g^-1 at 2 A g^-1. Electrochemical impedance spectroscopy also demonstrated an improvement in the electrical conductivity and electrochemical behavior of NV/RGO/NF nanocomposite compared to the RGO/NF and NV/NF. Furthermore, NV/RGO/NF electrode reserved about 88% of its initial capacity after 1000th potential cycle at 50 mV s^-1. Overall, the results of our study suggest that the NV/RGO nanocomposite prepared in the presence of ultrasonic irradiation might be regarded as a suitable active material for energy storage systems.

A hollow-nanosphere-based microfluidic biosensor for biomonitoring of cardiac troponin I

Cardiovascular diseases (CVDs) are the leading causes of death worldwide.