Herein, pure α-Fe2O3, binary α-Fe2O3/NiO, and ternary α-Fe2O3/NiO/rGO composites were prepared by a hydrothermal method. The properties of the prepared materials were studied by powder X-ray diffraction, scanning electron microscopy, TEM, XPS, and Brunauer-Emmett-Teller techniques. The clusters of smaller α-Fe2O3 nanoparticles (∼30 nm) along with conducting NiO was freely covered by the rGO layer sheet, which offer a higher electrode-electrolyte interface for improved electrochemical performance. The ternary composite has shown a higher specific capacitance of 747 F g-1@ a current density of 1 A g-1 in a 6 M KOH solution, when compared with that of α-Fe2O3/rGO (610 F g-1@1 A g-1) and α-Fe2O3 (440 F g-1@1 A g-1) and the nanocomposite. Moreover, the ternary α-Fe2O3/NiO/rGO composite exhibited a 98% rate capability @ 10 A g-1. The exceptional electrochemical performance of ternary composites has been recognized as a result of their well-designed unique architecture, which provides a large surface area and synergistic effects among all three constituents. The asymmetric supercapacitor (ASC) device was assembled using the ternary α-Fe2O3/NiO/rGO composite as the anode electrode (positive) material and activated carbon as the cathode (negative) material. The ASC device has an energy density of 35.38 W h kg-1 at a power density of 558.6 W kg-1 and retains a 94.52% capacitance after 5000 cycles at a 1 A g-1 current density.
Herein, we report the synthesis of α-MnO2 nanoflower-incorporated zinc-terephthalate MOFs (MnO2@Zn-MOFs) via the conventional solution phase synthesis technique as an electrode material for supercapacitor applications. The material was characterized by powder-X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy techniques. The prepared electrode material exhibited a specific capacitance of 880.58 F g-1 at 5 A g-1, which is higher than the pure Zn-BDC (610.83 F g-1) and pure α-MnO2 (541.69 F g-1). Also, it showed a 94% capacitance retention of its initial value after 10,000 cycles at 10 A g-1. The improved performance is attributed to the increased number of reactive sites and improved redox activity due to MnO2 inclusion. Moreover, an asymmetric supercapacitor assembled using MnO2@Zn-MOF as the anode and carbon black as the cathode delivered a specific capacitance of 160 F g-1 at 3 A g-1 with a high energy density of 40.68 W h kg-1 at a power density of 20.24 kW kg-1 with an operating potential of 0-1.35 V. The ASC also exhibited a good cycle stability of 90% of its initial capacitance.
The conversion of diverse non-petroleum carbon elements, such as coal, biomass, natural/shale gas, and even CO2, into cleaner hydrocarbon fuels and useful chemicals relies heavily on syngas, which is a combination of CO and H2. Syngas conversions, which have been around for almost a century, will probably become even more important in the production of energy and chemicals due to the rising need for liquid fuels and chemical components derived from sources of carbon other than crude oil. Although a number of syngas-based technologies, including the production of methanol, Fischer–Tropsch (FT) synthesis, and carbonylation, have been industrialized, there is still a great need for new catalysts with enhanced activity and adjustable product selectivity. New novel materials or different combinations of materials have been investigated to utilize the synergistic effect of these materials in an effective way. Magnetic materials are among the materials with magnetic properties, which provide them with extra physical characteristics compared to other carbon-based or conventional materials. Moreover, the separation of magnetic materials after the completion of a specific application could be easily performed with a magnetic separation process. In this review, we discuss the synthesis processes of various magnetic nanomaterials and their composites, which could be utilized as catalysts for syngas production and conversion. It is reported that applying an external magnetic field could influence the outcomes of any applications of magnetic nanomaterials. Here, the possible influence of the magnetic characteristics of magnetic nanomaterials with an external magnetic field is also discussed.