Nanocomposite supercapacitors for energy storage

Abstract

A method of storing electrical charge may include charging a capacitor, including an anode and/or a cathode layer further including a nanocomposite including graphitic C.sub.3N.sub.4, MnO.sub.2, and MgAl.sub.2O.sub.4 in a mass relationship to each other in a range of from 5 to 15:2 to 7:75 to 95, with alternating current at a frequency in a range of from 1 megahertz (MHz) to 12 MHz.

Claims

1. A method of storing electrical charge, the method comprising: charging a capacitor, comprising an anode and/or a cathode layer comprising a nanocomposite comprising graphitic C.sub.3N.sub.4, MnO.sub.2, and MgAl.sub.2O.sub.4 in a mass relationship to each other in a range of from 5 to 15:2 to 7:75 to 95, with alternating current at a frequency in a range of from 1 to 12 MHz.

2. The method of claim 1, wherein the average pore distribution of the nanocomposite is unimodal, and wherein a BET specific surface area of the nanocomposite is in a range of from 16.2 to 20.2 m.sup.2/g, and/or wherein an average pore diameter of the nanocomposite, according to BJH measurement method, is in a range of from 5 to 15 nm, and/or wherein an average pore volume of the nanocomposite, according to the BJH measurement method, is in a range of from 0.025 to 0.075 cm.sup.3/g.

3. The method of claim 1, wherein the nanocomposite has a (220) spinel interplanar spacing in a range of from 0.258 to 0.338 nm, (400) spinel interplanar spacing in a range of from 0.165 to 0.245 nm, (002) MnO.sub.2 interplanar spacing in a range of from 0.106 to 0.186 nm, and (211) Al.sub.2O.sub.3 interplanar spacing in a range of from 0.093 to 0.173 nm, according to selected area diffraction.

4. The method of claim 1, wherein the mass relationship of the nanocomposite is in a range of from 9 to 11:4 to 6:84 to 86, wherein the nanocomposite has a (220) spinel interplanar spacing of 0.2982% nm, (400) spinel interplanar spacing of 0.2052% nm, (002) MnO.sub.2 interplanar spacing of 0.1462% nm, and (211) Al.sub.2O.sub.3 interplanar spacing of 0.1332% nm, according to selected area diffraction, wherein an XRD spectrum of the nanocomposite under Cu-filtered Cu-K radiation (1.5418 ) powered at 45 kV and 10 mA has 2 peaks of an MnO.sub.2 pyrolusite phase at 28.41, 40.51, 44.91, 56.01, 66.41, and 79.11, an MgAl.sub.2O.sub.4 spinel phase at 19.11, 31.31, 44.81, 56.11, 59.51, 74.091, 78.11, an MgO cubic phase at 42.81, 62.21, and 74.61, an Al.sub.2O.sub.3 phase at 31.31, 34.31, and 61.61, g-C.sub.3N.sub.4-related diffractions at 18.81, 28.21, 35.51, 40.71, 44.61, and 73.71, and wherein no more than 5% relative intensity of any other phase is detected in the XRD spectrum.

5. The method of claim 1, wherein the charging is at a frequency in a range of from 3 to 12 MHZ, wherein the anode and/or a cathode layer comprising the nanocomposite, in operation, becomes an electric double-layer of conductor-rich grains separated by conductor-poor grain boundaries, and wherein the anode and/or a cathode layer comprising the nanocomposite forms an array of homogeneous spherical metal oxides nanoparticles having an average largest diameter in a range of from 6.4 to 9.4 nm on a porous structured layer comprising curled and/or wrinkled nanosheets and platelets of the g-C.sub.3N.sub.4.

6. The method of claim 1, wherein the nanocomposite has no more than 0.1 parts, individually, of thiol, amine, carboxylate, and hydroxyl functionalization per 100 MnO.sub.2 units, relative to a total metal oxide weight.

7. The method of claim 1, wherein the nanocomposite comprises no more than 1 wt. %, individually, of TiO.sub.2, Ti.sub.2AlN, Fe.sub.3O.sub.4, AlN, ZnO, and SiO.sub.2, relative to a total metal oxide weight.

8. The method of claim 1, wherein the nanocomposite comprises no more than 1 atoms of Ce, relative to 100 atoms of Mn.

9. The method of claim 1, wherein carbon materials in the nanocomposite comprise no more than 1 wt. %, individually, carbon nanotubes and carbon dots, relative to total nanocomposite weight.

10. The method of claim 1, wherein the nanocomposite no more than 1 wt. % AgBr, relative to a total metal oxide weight, and wherein the nanocomposite no more than 1 wt. % tungsten oxide, relative to a total nanocomposite weight.

11. The method of claim 1, wherein the nanocomposite comprises no more than 1 wt. %, individually, of a sulfide, phosphide, and boride, relative to total nanocomposite weight.

12. The method of claim 1, wherein the nanocomposite comprises no more than 1 wt. %, individually, CuO, aluminosilicate, and WO.sub.3, relative to total nanocomposite weight.

13. The method of claim 1, wherein the nanocomposite comprises no more than 1 wt. %, individually, elemental state Co and Fe, relative to total nanocomposite weight.

14. The method of claim 1, wherein the nanocomposite comprises no more than 0.1 wt. % of any noble metal, relative to total nanocomposite weight, and wherein the nanocomposite comprises no conductive polymer selected from polyaniline, polythiophene, and polypyrrole.

15. The method of claim 1, wherein the nanocomposite comprises no more than 10 wt. % MgO, relative to a total metal oxide weight, and wherein the nanocomposite comprises no clay.

16. The method of claim 1, wherein the nanocomposite obtained comprises no more than 1 wt. % carbonaceous material besides the graphitic carbon nitride, wherein the graphitic C.sub.3N.sub.4 is not nitrogen deficient, and wherein carbon materials in the nanocomposite comprise no more than 0.01 wt. % nanotubes and no nanorods, relative to total nanocomposite weight.

17. The method of claim 1, wherein the nanocomposite comprises no more than 10 wt. % Mn.sub.3O.sub.4, relative to total manganese oxide weight, or wherein the nanocomposite comprises manganese oxide in only one oxidation state.

18. The method of claim 1, wherein the graphitic C.sub.3N.sub.4 in the nanocomposite consists essentially of sheet morphologies, wherein the graphitic C.sub.3N.sub.4 in the nanocomposite comprises no more than inevitable traces of boron, and wherein the nanocomposite comprises no more than 1 wt. % of graphene (nitrogen-doped graphene), relative to total carbonaceous weight in the nanocomposite.

19. The method of claim 1, wherein the nanocomposite comprises no more than 10 wt. %, individually, relative to total metal content, of any of Zn, Ce, Gd, La, Ba, Ti, Ca, Sr, Zr, Pb, Ni, Ag, Au, Pt, Pd, Co, Cu, Mn, Cd, W, Ta, Nb, Pr, and Bi, and wherein the nanocomposite comprises no more than 1 wt. %, individually, relative to total carrier weight, of SiO.sub.2, TiO.sub.2, ZnO, NiB, and ZnS.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) A more complete appreciation of this disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

(2) FIG. 1 is a graph depicting X-ray diffraction (XRD) patterns of 10% g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanocomposite, according to certain embodiments.

(3) FIG. 2A is a transmission electron microscopy (TEM) image of the 10% g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanocomposite, according to certain embodiments.

(4) FIG. 2B is a selected area electron diffraction (SAED) pattern of the 10 g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanocomposite, according to certain embodiments.

(5) FIG. 2C is a high-resolution transmission electron microscopy (HRTEM) image of the 10% g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanocomposite, according to certain embodiments.

(6) FIG. 2D is a fast Fourier transform (FFT) spectra of the 10% g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanocomposite, according to certain embodiments.

(7) FIG. 2E is an inverse fast Fourier transform (IFFT) spectra of the 10% g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanocomposite, according to certain embodiments.

(8) FIG. 3 is a graph depicting influence of frequency on the AC conductivity of the 10% g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanocomposite, according to certain embodiments.

(9) FIG. 4 is a graph depicting frequency dependence of AC conductivity for the 10% g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanocomposite, according to certain embodiments.

(10) FIG. 5 is a graph depicting frequency dependence of dielectric constant of the g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanocomposite, according to certain embodiments.

(11) FIG. 6 is a graph depicting frequency-dielectric loss () correlation for the g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanocomposite, according to certain embodiments.

(12) FIG. 7 are Nyquist (Z-Z) plots of the g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanocomposite, at room temperature, according to certain embodiments.

DETAILED DESCRIPTION

(13) When describing the present disclosure, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise.

(14) Embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings wherever applicable, in that some, but not all, embodiments of the disclosure are shown.

(15) In the drawings, like reference numerals designate identical or corresponding parts throughout the several views. Further, as used herein, the words a, an and the like generally carry a meaning of one or more, unless stated otherwise.

(16) Furthermore, the terms approximately, approximate, about, and similar terms generally refer to ranges that include the identified value within a margin of 20%, 10%, or preferably 5%, and any values therebetween.

(17) The present disclosure is related to nanotechnology. As used herein, the term nanotechnology refers to a field of science and technology involving the manipulation, design, and application of materials, structures, and devices at the nanometer scale, typically between 1 and 100 nanometers. The properties and behaviors of the materials may differ significantly from those at the macro scale, thereby enabling enhanced functionality and performance in various applications.

(18) The present disclosure includes electrical applications. As used herein, the term electrical applications refers to the use of electrical principles, devices, and systems in the transmission, distribution, control, or conversion of electrical energy or signals, including but not limited to power generation, storage, processing, and communication, such applications are designed to enhance efficiency, functionality, or performance in electronic, electrical, or energy-related systems.

(19) As used herein, the term supercapacitor refers to an energy storage device that stores electrical energy through the electrostatic separation of charge, employing high surface area electrodes and an electrolyte. The device is capable of rapid charge and discharge cycles, providing high power density compared to conventional capacitors, and exhibiting greater charge retention than typical batteries.

(20) As used herein, the term energy storage refers to the process or technology of capturing and storing energy for later use, typically involving the conversion of electrical energy into a form that can be retained and subsequently retrieved as needed. Such energy storage systems may include batteries, supercapacitors, and other devices that store energy in chemical, electrostatic, or other forms for efficient delivery on demand.

(21) As used herein, the term anode refers to the electrode in an electrical device, such as a battery, capacitor, or electrochemical cell, where oxidation occurs. It is the terminal through which current flows into the device from an external circuit in the case of discharging. For a battery, during discharge, the anode releases electrons that flow through the external circuit, while ions move within the device to balance the charge. In a capacitor, the anode is one of the two electrodes where charge is stored, typically paired with a cathode. The specific function of the anode depends on the device, but its primary role is always related to facilitating electron flow and maintaining charge balance during the electrochemical reaction.

(22) As used herein, the term cathode refers to the electrode in an electrical device, such as a battery, capacitor, or electrochemical cell, where reduction occurs. The cathode is the terminal through which current flows out of the device when it is discharging. During the discharge process in a battery, the cathode accepts electrons that flow through the external circuit from the anode, and the ions move within the device to balance the charge. In a capacitor, the cathode is one of the two electrodes where charge is stored, working in conjunction with the anode. The cathode is where the electrochemical reaction results in the gain of electrons, completing the electrical circuit and enabling energy storage or release.

(23) As used herein, the term electric double-layer (EDL) refers to a charge structure formed at the interface between a conductive electrode and an electrolyte. It consists of two layers: the inner layer, where ions are tightly adsorbed to the electrode surface with opposite charge, and the outer diffuse layer, where ions are loosely associated with the electrode. This double-layer configuration enables energy storage by separating charges at the electrode-electrolyte interface, which is fundamental to the operation of electrochemical devices like capacitors and supercapacitors.

(24) As used herein, the term conductor-rich grains refer to regions within a material where there is a high concentration of conductive elements or phases, typically metals or conductive compounds. These grains have enhanced electrical conductivity due to the abundance of charge carriers such as electrons. In the context of nanocomposites or electrode materials, conductor-rich grains are essential for facilitating efficient electron transport and improving the overall conductivity of the material.

(25) As used herein, the term conductor-poor grain boundaries refer to the regions between conductive grains where the concentration of conductive elements is significantly lower, resulting in reduced electrical conductivity. These boundaries can act as barriers to electron flow, limiting the overall conductivity of the material. In certain materials, conductor-poor grain boundaries are used strategically to influence charge storage and distribution, enhancing specific properties like capacitance or stability.

(26) As used herein, the term noble metal refers to a group of metals that are resistant to corrosion and oxidation in moist air. These metals are typically chemically inert and maintain their luster and appearance over time. Some common noble metals include gold, silver, platinum, and palladium. They are generally used in electronics processes due to their durability and resistance to chemical reactions.

(27) As used herein, the term conductive polymer refers to a type of polymer material that can conduct electricity. Conductive polymers have been chemically modified or doped with specific materials to allow the flow of electrical charge. These materials have a structure that allows electrons to move through them, making them useful in a variety of electronic applications such as flexible electronics, sensors, and conductive inks. Examples of conductive polymers include polyaniline, polypyrrole, and polyacetylene.

(28) As used herein, the term nanoparticles (NPs) refers to particles having a particle size of 1 nanometer (nm) to 500 nm within the scope of the present disclosure.

(29) As used herein, the term nanocomposite is a material that is made by combining a matrix (often a polymer, metal, or ceramic) with NPs or nanocomposites to enhance its properties. The NPs are typically on the scale of nm (1 to 100 nm), and their small size and high surface area can significantly improve the composite material's strength, thermal stability, electrical conductivity, optical properties, and other characteristics.

(30) As used herein, the term unimodal refers to a distribution or pattern that has a single peak or mode. In the context of particle size or material properties, it indicates that the sample consists of particles or components that are primarily of one size or characteristic, rather than varying widely in size or composition.

(31) As used herein, the term pore volume refers to the total volume of void spaces (pores) within a material that are capable of being filled by a gas or liquid. It is typically expressed in cubic centimeters per gram (cm.sup.3/g) and is an important parameter in characterizing the porous structure of materials, such as adsorbents or catalysts. As used herein, the term pore diameter refers to the average width or size of the pores (void spaces) within a material, typically measured in nm or angstroms (). It is a key parameter in characterizing the texture and permeability of porous materials, influencing their adsorption, filtration, or catalytic properties. Pore diameter is often determined using methods such as nitrogen adsorption or mercury intrusion, which provide insights into the material's ability to absorb or interact with molecules of specific sizes. As used herein, the term spinel interplanar spacing refers to the distance between parallel planes of atoms in the crystal structure of a spinel material. Spinel is a type of mineral with a specific crystalline arrangement, represented by the general formula AB.sub.2O.sub.4, where A and B are metal ions. The interplanar spacing is crucial for understanding the material's structural properties and is typically measured using X-ray diffraction (XRD) techniques.

(32) As used herein, the term Knop's phenomenological theory describes the frequency-dependent behavior of dielectric properties, such as dielectric constant () and dielectric loss (), in materials. The theory postulates that charge carriers, including electrons and holes, contribute to the polarization of the material. At lower frequencies, charge carriers align more easily with the electric field, leading to higher dielectric constants. As the frequency increases, charge carriers cannot keep up with the oscillating field, resulting in decreased dielectric constant and increased dielectric loss. Electrical conduction is attributed to the hopping mechanism, where electrons and holes move between localized sites. This theory explains the observed frequency dependence of dielectric properties and conductivity in materials.

(33) A weight percent of a component, unless specifically stated to the contrary, is based on the total weight of the formulation or composition in which the component is included. For example, if a particular element or component in a composition or article is said to have 5 wt. %, it is understood that this percentage is in relation to a total compositional percentage of 100%.

(34) The present disclosure is intended to include all hydration states of a given compound or formula, unless otherwise noted or when heating a material.

(35) In addition, the present disclosure is intended to include all isotopes of atoms occurring in the present compounds and complexes. Isotopes include those atoms having the same atomic number but different mass numbers. By way of general example, and without limitation, isotopes of hydrogen include deuterium and tritium, and isotopes of carbon include .sup.13C and .sup.14C. Isotopes of oxygen include .sup.16O, .sup.17O, and .sup.18O. Isotopically-labeled compounds of the disclosure may generally be prepared by conventional techniques known to those skilled in the art or by processes analogous to those described herein, using an appropriate isotopically-labeled reagent in place of the non-labeled reagent otherwise employed.

(36) Aspects of the present disclosure are directed toward g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanocomposites, which have been synthesized using simple methods. As used herein, the term g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanocomposites refers to a composite material consisting of graphitic carbon nitride (g-C.sub.3N.sub.4) functionalized with manganese dioxide (MnO.sub.2) and magnesium aluminate (MgAl.sub.2O.sub.4). The g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanomaterial may be investigated for its electrical and dielectric properties, with potential applications in energy storage and other electronic devices. The electrical conductivity values for the sample increased with frequency, indicating semiconducting behavior. The variation of dielectric constant (), dielectric loss (), and AC conductivity with frequency has been studied. Both dielectric constant () and dielectric loss () decrease with the increase in frequency, while AC conductivity increases. The frequency-dependent behavior of and is explained using Knop's phenomenological theory, with the electrical conduction mechanism attributed to the hopping of electrons and holes.

(37) A nanocomposite (g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4) including g-C.sub.3N.sub.4, MnO.sub.2, and MgAl.sub.2O.sub.4 is described. The g-C.sub.3N.sub.4, MnO.sub.2, and MgAl.sub.2O.sub.4 are present in the nanocomposite in a mass relationship to each other in a range of from 5 to 15:2 to 7:75 to 95, preferably 7 to 13:3 to 6:80 to 90, preferably 9 to 11:4 to 5:84 to 86, and yet more preferably 10:5:85, while tolerable variations of any of these values may be 2.5, 2, 1.5, 1, 0.75, 0.5, 0.25, 0.1, 0.5, or 0.1.

(38) The nanocomposite may be porous. A porous material is the one that forms a porous bulk solid. Pores may be micropores, mesopores, macropores, and/or a combination thereof. The pores exist in the bulk material, not necessarily in the molecular structure of the material. The term microporous means that nanocomposite have pores with an average pore width (i.e. diameter) of less than 2 nm, e.g., in a range with an upper limit of 2, 1, 0.9, 0.75, 0.5, 0.25, 0.1, 0.05, or 0.01 nm, and/or a lower limit of 0.00001, 0.0001, 0.001, 0.01, 0.1, 0.25, 0.5, 0.75, or 1 nm. The term mesoporous means the pores of the nanocomposite have an average pore width of 2 to 50 nm, though this may include subranges within this general range, e.g., a minimum diameter of 2, 3, 5, 10, 15, 20, 25, or 35 nm, and/or a maximum diameter of 50, 45, 40, 35, 30, 25, 20, 15, or 10 nm. The term macroporous means the pores of nanocomposite have an average pore width larger than 50 nm, e.g., at least 55, 75, 100, 250, 500, 750, or 1000 nm. Pore size may be determined by methods including, but not limited to, gas adsorption (e.g. N.sub.2 adsorption), mercury intrusion porosimetry, and imaging techniques such as scanning electron microscopy (SEM), and X-ray computed tomography (XRCT).

(39) A Brunauer-Emmett-Teller (BET) specific surface area of the nanocomposite may be in a range of from 16.2 to 20.2 square meters per gram (m.sup.2/g), preferably 16.4 to 20.0 m.sup.2/g, preferably 16.6 to 19.8 m.sup.2/g, preferably 16.8 to 19.6 m.sup.2/g, preferably 17.0 to 19.4 m.sup.2/g, preferably 17.2 to 19.2 m.sup.2/g, preferably 17.4 to 19.0 m.sup.2/g, preferably 17.6 to 18.8 m.sup.2/g, preferably 17.8 to 18.6 m.sup.2/g, and preferably 18.0 to 18.4 m.sup.2/g. The surface area of the nanocomposite may be 18.73, 2.5, 2, 1.5, 1, 0.75, 0.5, 0.25, 0.2, or 0.1 m.sup.2/g. The BET hypothesis is the foundation for a significant analysis method for determining the specific surface area of a material. It attempts to explain the physical adsorption of gas molecules on a solid surface. Specific surface area is a property of solids, which is the total surface area of a material per unit of mass, solid or bulk volume, or cross-sectional area. The pore diameter, pore volume, and BET surface area are measured by gas adsorption analysis, preferably N.sub.2 adsorption analysis (e.g., N.sub.2 adsorption isotherms).

(40) An average pore diameter of the nanocomposite, according to Barrett-Joyner-Halenda (BJH) measurement method, may be in a range of from 5 to 15 nm, preferably 6 to 14 nm, preferably 7 to 13 nm, preferably 8 to 12 nm, and preferably 9 to 11 nm. The nanocomposite may have an average pore diameter of 8.341.5, 1, 0.75, 0.5, 0.25, 0.2, or 0.1 nm. An average pore volume of the nanocomposite, according to the BJH measurement method, may be in a range of from 0.025 to 0.075 cm.sup.3/g, preferably 0.030 to 0.070 cm.sup.3/g, preferably 0.035 to 0.065 cm.sup.3/g, preferably 0.040 to 0.060 cm.sup.3/g, and preferably 0.045 to 0.055 cm.sup.3/g. The average pore volume of the nanocomposite, according to the BJH measurement method, may be 0.050.02, 0.01, 0.0075, 0.005, 0.0025, or 0.001 cm.sup.3/g.

(41) The average pore distribution of the nanocomposite may include, but is not limited to, crystalline average pore distribution, bimodal, trimodal, multimodal, narrow, broad, and Gaussian. The average pore distribution of the nanocomposite may be unimodal. indicating a single dominant pore size within the material. This unimodal distribution suggests that the nanocomposites possess a relatively narrow pore size range, resulting in more uniform pore structures and enhancing specific properties such as adsorption capacity, catalytic activity, or surface reactivity.

(42) The nanocomposite may have a (220) spinel interplanar spacing in a range of from 0.258 to 0.338 nm, preferably 0.263 to 0.333 nm, preferably 0.268 to 0.328 nm, preferably 0.273 to 0.323 nm, preferably 0.278 to 0.318 nm, preferably 0.283 to 0.313 nm, preferably 0.288 to 0.308 nm, and preferably 0.293 to 0.303 nm, according to selected area diffraction (SAED). The nanocomposite may have a (400) spinel interplanar spacing in a range of from 0.165 to 0.245 nm, preferably 0.170 to 0.240 nm, preferably 0.175 to 0.235 nm, preferably 0.180 to 0.230 nm, preferably 0.185 to 0.225 nm, preferably 0.190 to 0.220 nm, preferably 0.195 to 0.215 nm, and preferably 0.200 to 0.210 nm, according to SAED. The nanocomposite may include a (002) MnO.sub.2 interplanar spacing in a range of from 0.106 to 0.186 nm, preferably 0.116 to 0.176 nm, preferably 0.126 to 0.166 nm, preferably 0.136 to 0.156 nm preferably, according to SAED. The nanocomposite may include a (211) Al.sub.2O.sub.3 interplanar spacing in a range of from 0.093 to 0.173 nm, 0.093 to 0.173 nm, preferably 0.103 to 0.163 nm, preferably 0.113 to 0.153 nm, preferably 0.123 to 0.143 nm, according to SAED.

(43) The nanocomposite may have a (220) spinel interplanar spacing may be 0.2982% nm, (400) spinel interplanar spacing may be 0.2052% nm, (002) MnO.sub.2 interplanar spacing may be 0.1462% nm, and/or (211) Al.sub.2O.sub.3 interplanar spacing may be 0.1332% nm, according to SAED.

(44) An XRD spectrum of the nanocomposite under Cu-filtered Cu K radiation (1.5418 ) powered at 45 kilovolt (kV) and 10 milliamperes (mA) may have 2 peaks of a MnO.sub.2 pyrolusite phase at 28.41, 40.51, 44.91, 56.01, 66.41, and/or 79.11, a MgAl.sub.2O.sub.4 spinel phase at 19.11, 31.31, 44.81, 56.11, 59.51, 74.091, and/or 78.11, an MgO cubic phase at 42.81, 62.21, and/or 74.61, an Al.sub.2O.sub.3 phase at 31.31, 34.31, and/or 61.61, and/or g-C.sub.3N.sub.4-related diffractions at 18.81, 28.21, 35.51, 40.71, 44.61, and/or 73.71.

(45) No more than 5%, preferably no more than 4 wt. %, preferably no more than 3 wt. %, preferably no more than 2 wt. %, preferably no more than 1 wt. %, preferably no more than 0.5 wt. %, preferably no more than 0.4 wt. %, preferably no more than 0.3 wt. %, preferably no more than 0.2 wt. %, preferably no more than 0.1 wt. %, preferably no more than 0.05 wt. %, and preferably no more than 0.01 wt. % relative intensity of any other phase may be detected in the XRD spectrum.

(46) The MgO may have a cubic crystal structure. Alternatively or additionally, the MgO may exist in other crystal phases, including hexagonal, monoclinic, tetragonal, rhombohedral, and orthorhombic phases.

(47) MgAl.sub.2O.sub.4 may have a spinel phase. The spinel phase is a mixed oxide with the general formula AB.sub.2O.sub.4, including one divalent cation (A.sup.2+) and two trivalent cations (B.sup.3+). The unit cell consists of a face-centered cubic arrangement of oxygen ions, containing 32 O.sup.2 ions, with 64 tetrahedral and 32 octahedral sites occupied by A.sup.2+ and B.sup.3+ cations. When one-half of the octahedral interstices are occupied by B.sup.3+ cations and one-eighth of the tetrahedral sites are occupied by A.sup.2+ cations, the spinel phase is termed normal. Conversely, when tetrahedral sites are occupied by half of the B.sup.3+ and octahedral sites by the other half along with A.sup.2+, the spinel phase is termed inverse.

(48) MgAl.sub.2O.sub.4 may be used in various applications, such as in metallurgical, electrochemical, radio-technical, and chemical industrial fields owing to its high thermal stability (melting point at 2135 degrees Celsius ( C.), high hardness (16 gigapascal (GPa)), high mechanical resistance, high resistance against chemical attack, wide band gap energy, high electrical resistivity, relatively low thermal expansion coefficient (9.10.sup.6 l/ C.) between 3 and 1400 C., low dielectric constant, low density (3.58 gram per cubic centimeter (g/cm.sup.3)), high thermal shock resistance, hydrophobicity, and low surface acidity.

(49) The nanocomposite may have no more than 0.1, 0.075, 0.05, 0.025, 0.01, 0.005, 0.001, 0.0001, or 0.00001 parts, individually or in any combination, of thiol, amine, carboxylate, and/or hydroxyl functionalization per 100 MnO.sub.2 units (or per 1 MnO.sub.2 unit), relative to a total metal oxide weight.

(50) The nanocomposite may include no more than 1, 0.75, 0.5, 0.25, 0.1, 0.01, 0.001, 0.0001, or 0.00001 wt. %, individually or in any combination, of titanium dioxide (TiO.sub.2), titanium aluminum nitride (Ti.sub.2AlN), iron (III) oxide (Fe.sub.3O.sub.4), aluminum nitride (AlN), zinc oxide (ZnO), and/or silicon dioxide (SiO.sub.2), relative to a total metal oxide weight.

(51) The nanocomposite may include no more than 1, 0.75, 0.5, 0.25, 0.1, 0.01, 0.001, 0.0001, or 0.00001 atom of cerium (Ce), relative to 100 atoms of manganese (Mn).

(52) The carbon materials in the nanocomposite may have no more than 1, 0.75, 0.5, 0.25, 0.1, 0.01, 0.001, 0.0001, or 0.00001 wt. %, preferably less than 0.9 wt. %, preferably less than 0.8 wt. %, preferably less than 0.7 wt. %, preferably less than 0.6 wt. %, preferably less than 0.5 wt. %, preferably less than 0.4 wt. %, preferably less than 0.3 wt. %, preferably less than 0.2 wt. %, preferably less than 0.1 wt. %, individually or in combination, carbon nanotubes (CNTs) and/or carbon dots, relative to total nanocomposite weight.

(53) The nanocomposite may have no more than 1, 0.75, 0.5, 0.25, 0.1, 0.01, 0.001, 0.0001, or 0.00001 wt. %, preferably less than 0.9 wt. %, preferably less than 0.8 wt. %, preferably less than 0.7 wt. %, preferably less than 0.6 wt. %, preferably less than 0.5 wt. %, preferably less than 0.4 wt. %, preferably less than 0.3 wt. %, preferably less than 0.2 wt. %, preferably less than 0.1 wt. %, silver bromide (AgBr), relative to a total metal oxide weight.

(54) The nanocomposite may have no more than 1, 0.75, 0.5, 0.25, 0.1, 0.01, 0.001, 0.0001, or 0.00001 wt. %, preferably less than 0.9 wt. %, preferably less than 0.8 wt. %, preferably less than 0.7 wt. %, preferably less than 0.6 wt. %, preferably less than 0.5 wt. %, preferably less than 0.4 wt. %, preferably less than 0.3 wt. %, preferably less than 0.2 wt. %, preferably less than 0.1 wt. % tungsten oxide (WO.sub.3), relative to a total nanocomposite weight.

(55) The nanocomposite may have no more than 1, 0.75, 0.5, 0.25, 0.1, 0.01, 0.001, 0.0001, or 0.00001 wt. %, preferably less than 0.9 wt. %, preferably less than 0.8 wt. %, preferably less than 0.7 wt. %, preferably less than 0.6 wt. %, preferably less than 0.5 wt. %, preferably less than 0.4 wt. %, preferably less than 0.3 wt. %, preferably less than 0.2 wt. %, preferably less than 0.1 wt. % individually or in any combination, of a sulfide, phosphide, and/or boride, relative to total nanocomposite weight.

(56) The nanocomposite may have no more than 1, 0.75, 0.5, 0.25, 0.1, 0.01, 0.001, 0.0001, or 0.00001 wt. %, preferably less than 0.9 wt. %, preferably less than 0.8 wt. %, preferably less than 0.7 wt. %, preferably less than 0.6 wt. %, preferably less than 0.5 wt. %, preferably less than 0.4 wt. %, preferably less than 0.3 wt. %, preferably less than 0.2 wt. %, preferably less than 0.1 wt. %, individually or in any combination, of copper oxide (CuO), aluminosilicate, and/or WO.sub.3, relative to total nanocomposite weight.

(57) The nanocomposite may have no more than 1, 0.75, 0.5, 0.25, 0.1, 0.01, 0.001, 0.0001, or 0.00001 wt. %, preferably less than 0.9 wt. %, preferably less than 0.8 wt. %, preferably less than 0.7 wt. %, preferably less than 0.6 wt. %, preferably less than 0.5 wt. %, preferably less than 0.4 wt. %, preferably less than 0.3 wt. %, preferably less than 0.2 wt. %, preferably less than 0.1 wt. %, individually or together, elemental state Co and/or Fe, relative to total nanocomposite weight.

(58) The nanocomposite may include no more than 0.1, 0.075, 0.05, 0.025, 0.01, 0.005, 0.001, 0.0001, or 0.00001 wt. % of any noble metal, relative to total nanocomposite weight. The nanocomposite comprises no conductive polymer selected from polyaniline, polythiophene, and/or polypyrrole, e.g., no more than 5, 4, 3, 2.5, 2, 1, 0.5, 0.1, 0.01, 0.001, 0.0001, or 0.00001 wt. %, relative to total nanocomposite weight or total layer weight in which the nanocomposite is present, of polyaniline, polythiophene, and/or polypyrrole.

(59) The nanocomposite includes no more than 10, 7.5, 5, 4, 3, 2, 1, 0.5, 0.1, 0.01, 0.001, 0.0001, or 0.00001 wt. %, preferably less than 9 wt. %, preferably less than 8 wt. %, preferably less than 7 wt. %, preferably less than 6 wt. %, preferably less than 5 wt. %, preferably less than 4 wt. %, preferably less than 3 wt. %, preferably less than 2 wt. %, preferably less than 1 wt. %, preferably less than 0.9 wt. %, preferably less than 0.8 wt. %, preferably less than 0.7 wt. %, preferably less than 0.6 wt. %, preferably less than 0.5 wt. %, preferably less than 0.4 wt. %, preferably less than 0.3 wt. %, preferably less than 0.2 wt. %, preferably less than 0.1 wt. % magnesium oxide (MgO), relative to a total metal oxide weight. The nanocomposite may include no clay, e.g., no more than 5, 4, 3, 2.5, 2, 1, 0.5, 0.1, 0.01, 0.001, 0.0001, or 0.00001 wt. %, relative to total nanocomposite weight, of clay.

(60) The nanocomposite may include no more than 1, 0.75, 0.5, 0.25, 0.1, 0.01, 0.001, 0.0001, or 0.00001 wt. % of carbonaceous material, preferably less than 0.9 wt. %, preferably less than 0.8 wt. %, preferably less than 0.7 wt. %, preferably less than 0.6 wt. %, preferably less than 0.5 wt. %, preferably less than 0.4 wt. %, preferably less than 0.3 wt. %, preferably less than 0.2 wt. %, preferably less than 0.1 wt. %, preferably less than 0.05 wt. %, and preferably less than 0.01 wt. % of carbonaceous material besides the graphitic carbon nitride. The g-C.sub.3N.sub.4 may not be nitrogen deficient. The g-C.sub.3N.sub.4 in the nanocomposite includes no more than inevitable traces of boron e.g., no more than 5, 4, 3, 2.5, 2, 1, 0.5, 0.1, 0.01, 0.001, 0.0001, or 0.00001 wt. %, relative to total nanocomposite weight, of boron. The carbon materials in the nanocomposite may include no more than 0.01, 0.0075, 0.005, 0.0025, 0.001, 0.0005, or 0.0001 wt. % nanotubes and/or nanorods, or none of either or both, relative to total nanocomposite weight.

(61) The nanocomposite may include no more than 1, 0.75, 0.5, 0.25, 0.1, 0.01, 0.001, 0.0001, or 0.00001 wt. % of carbonaceous material, preferably less than 0.9 wt. %, preferably less than 0.8 wt. %, preferably less than 0.7 wt. %, preferably less than 0.6 wt. %, preferably less than 0.5 wt. %, preferably less than 0.4 wt. %, preferably less than 0.3 wt. %, preferably less than 0.2 wt. %, preferably less than 0.1 wt. %, preferably less than 0.05 wt. %, and preferably less than 0.01 wt. % of graphene (e.g., nitrogen-doped graphene), relative to total carbonaceous weight in the nanocomposite

(62) The morphology of the g-C.sub.3N.sub.4 may be nanowires, nanospheres, nanocrystals, nanorectangles, nanotriangles, nanopentagons, nanohexagons, nanoprisms, nanodisks, nanocubes, nanoribbons, nanoblocks, nanotoroids, nanodiscs, nanobarrels, nanogranules, nanowhiskers, nanoflakes, nanofoils, nanopowders, nanoboxes, nanobeads, nanobelts, nano-urchins, nanoflowers, nanostars, tetrapods, etc., and mixtures thereof. The g-C.sub.3N.sub.4 in the nanocomposite may have a sheet morphology.

(63) The nanocomposite may include no more than 10, 7.5, 5, 4, 3, 2, 1, 0.5, 0.1, 0.01, 0.001, 0.0001, or 0.00001 wt. %, preferably 9 wt. %, preferably 8 wt. %, preferably 7 wt. %, preferably 6 wt. %, preferably 5 wt. %, preferably 4 wt. %, preferably 3 wt. %, preferably 2 wt. %, preferably 1 wt. %, preferably 0.5 wt. % Mn.sub.3O.sub.4, relative to total manganese oxide weight. The nanocomposite comprises manganese oxide in only one oxidation state.

(64) The nanocomposite may include no more than 1, 0.75, 0.5, 0.25, 0.1, 0.01, 0.001, 0.0001, or 0.00001 wt. %, preferably less than 0.9 wt. %, preferably less than 0.8 wt. %, preferably less than 0.7 wt. %, preferably less than 0.6 wt. %, preferably less than 0.5 wt. %, preferably less than 0.4 wt. %, preferably less than 0.3 wt. %, preferably less than 0.2 wt. %, preferably less than 0.1 wt. %, individually or in any combination, of K.sub.2Ti.sub.8O.sub.17, Al.sub.2O.sub.3, ZnO, Fe.sub.3O.sub.4, CeFeO.sub.3, GdFeO.sub.3, LaFeO.sub.3, BaTiO.sub.3, CaTiO.sub.3, SrTiO.sub.3, CaZrO.sub.3, PbTiO.sub.3, Mg.sub.1-xNi.sub.xFe.sub.2O.sub.4 (x=0.0, 0.6, 1.0), Ag, CoFe.sub.2O.sub.4, CuFe.sub.2O.sub.4, MnFe.sub.2O.sub.4, NiFe.sub.2O.sub.4, ZnFe.sub.2O.sub.4, Cu.sub.1-xCd.sub.xFe.sub.2O.sub.4, Zn.sub.0.7Ni.sub.0.15Cu.sub.0.15Fe.sub.2O.sub.4, Zn.sub.0.3Ni.sub.0.7-xCo.sub.xFe.sub.2O.sub.4 (0x0.7), Mn.sub.0.1Mg.sub.0.2(Co, Ni, Zn).sub.0.7Fe.sub.2O.sub.4, LaCo.sub.0.5Fe.sub.0.5O.sub.3, Mg.sub.0.1Co.sub.0.9Fe.sub.2O.sub.4, La.sub.1-xGd.sub.xCr.sub.1-yNi.sub.yO.sub.3, Gd.sub.2FeCrO.sub.6, KTaO.sub.3, NaTaO.sub.3, NaNbO.sub.3, KNbO.sub.3, Mg.sub.1-xNi.sub.xFe.sub.2O.sub.4, Cu.sub.0.5Cd.sub.0.25Co.sub.0.25Fe.sub.2-xO.sub.4, Zn.sub.0.5Co.sub.0.5La.sub.xFe.sub.2-xO.sub.4, Pr.sub.2Ti.sub.2O.sub.7, SiO.sub.2, TiO.sub.2, ZnS, Bi.sub.4O.sub.5I.sub.2, SrFe.sub.0.5 Ta.sub.0.5O.sub.3, La.sub.0.8Ba.sub.0.2TiO.sub.3.5-, LaTiO.sub.3.5-, NaNbO.sub.3, and/or LaFeO.sub.3, relative to a total metal oxide weight

(65) The nanocomposite includes no more than 10, 7.5, 5, 4, 3, 2, 1, 0.5, 0.1, 0.01, 0.001, 0.0001, or 0.00001 wt. %, preferably less than 9 wt. %, preferably less than 8 wt. %, preferably less than 7 wt. %, preferably less than 6 wt. %, preferably less than 5 wt. %, preferably less than 4 wt. %, preferably less than 3 wt. %, preferably less than 2 wt. %, preferably less than 1 wt. %, preferably less than 0.9 wt. %, preferably less than 0.8 wt. %, preferably less than 0.7 wt. %, preferably less than 0.6 wt. %, preferably less than 0.5 wt. %, preferably less than 0.4 wt. %, preferably less than 0.3 wt. %, preferably less than 0.2 wt. %, preferably less than 0.1 wt. %, individually or in any combination, relative to total metal content, of any of zinc (Zn), cerium (Ce), gadolinium (Gd), lanthanum (La), barium (Ba), titanium (Ti), calcium (Ca), strontium (Sr), zirconium (Zr), lead (Pb), nickel (Ni), silver (Ag), gold (Au), cobalt (Co), copper (Cu), manganese (Mn), cadmium (Cd), tungsten (W), tantalum (Ta), niobium (Nb), praseodymium (Pr), and/or bismuth (Bi).

(66) The nanocomposite may include no more than 1, 0.75, 0.5, 0.25, 0.1, 0.01, 0.001, 0.0001, or 0.00001 wt. %, preferably less than 0.9 wt. %, preferably less than 0.8 wt. %, preferably less than 0.7 wt. %, preferably less than 0.6 wt. %, preferably less than 0.5 wt. %, preferably less than 0.4 wt. %, preferably less than 0.3 wt. %, preferably less than 0.2 wt. %, preferably less than 0.1 wt. %, individually or in any combination, relative to total carrier weight, of SiO.sub.2, TiO.sub.2, ZnO, and/or ZnS.

(67) The purpose of the g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanocomposite described may be to provide a highly specific and controlled formulation of the composite for anticancer applications, where the presence of various materials may be carefully limited to ensure the desired properties. The nanocomposite may include no more than 0.1, 0.075, 0.05, 0.025, 0.01, 0.001, 0.0001, or 0.00001 parts of thiol, amine, carboxylate, and/or hydroxyl functional groups per 100 MnO.sub.2 units (or 10 or 1 MnO.sub.2 unit), and may restrict the content of various other materials (e.g., TiO.sub.2, ZnO, Fe.sub.3O.sub.4, CNTs, noble metals, etc.) to ensure a defined composition. The nanocomposite may also limit specific metal oxide and carbon material content, as well as certain doping and alloying elements, to maintain the efficacy and safety of the material. These restrictions aim to enhance the performance of the nanocomposite as an anticancer agent while minimizing undesired side effects or interactions with biological systems.

(68) The method may include charging a capacitor, including an anode and/or a cathode layer including the nanocomposite, with alternating current at a frequency in a range of from 1 to 12 megahertz (MHz), preferably 1.5 to 12 MHz, preferably 2 to 12 MHz, preferably 2.5 to 12 MHz, and yet more preferably 3 to 12 MHz. The anode and/or a cathode layer including the nanocomposite, in operation, becomes an electric double-layer of conductor-rich grains separated by conductor-poor grain boundaries. This configuration enhances charge storage efficiency. The anode and/or a cathode layer including the nanocomposite forms an array of homogeneous spherical metal oxides nanoparticles having an average largest diameter in a range of from 6.4 to 9.4 nm, preferably 7 to 9.2 nm, preferably 7.1 to 9.1 nm, preferably 7.5 to 9.0 nm, and yet more preferably 7.9 nm on a porous structured layer including curled and/or wrinkled nanosheets and platelets of the g-C.sub.3N.sub.4, enhancing the capacitive performance and enhancing the charge storage capacity of the capacitor. The purpose of forming spherical metal oxide nanoparticles in the anode and/or cathode layer of the nanocomposite may be to enhance the capacitive performance and increase the charge storage capacity of the capacitor. The spherical shape of the nanoparticles enhances the material's surface area and facilitates efficient charge distribution and storage.

(69) Inventive supercapacitors may be charged to any potential within their rated voltage range and can be fully discharged (discharged to 0V), then recharged to full capacity, while batteries are limited by their own chemical reactions to operate in a narrow voltage range (VV), and over-discharge may cause permanent damage. Such supercapacitors could have inventive nanocomposites in the electrodes or in an electrolyte between them, which may be solid or liquid.

EXAMPLES

(70) The following examples demonstrate a method of storing electrical charge via a nanocomposite. The examples are provided solely for illustration and are not to be construed as limitations of the present disclosure, as many variations thereof are possible without departing from the spirit and scope of the present disclosure.

Example 1: Fabrication of g-C.SUB.3.N.SUB.4.@MnO.SUB.2./MgAl.SUB.2.O.SUB.4 .(10:5:85, wt. %) Nanocomposite

(71) According to the present disclosure, magnesium nitrate, and aluminum nitrate were added together in one beaker with manganese chloride, in a predetermined amount (here, stoichiometric), to produce a 10% MnO.sub.2@MgAl.sub.2O.sub.4 nanocomposite. Further, about 10 grams (g) of methanol, as a fuel, was added to the beaker, followed by 30 milliliters (mL) of distilled water. The beaker was heated till a clear solution was obtained, and heated further till dryness. The obtained product was ground in a mortar, transferred to a 150 mL porcelain dish, and calcined at 700 C. for 3.0 hours. Furthermore, the 10% MnO.sub.2@MgAl.sub.2O.sub.4 product was cooled down to room temperature and weighed, ground with urea in an amount suitable (here, 2 g urea to 20 g of the 10% MnO.sub.2/MgAl.sub.2O.sub.4 product, but depending upon the reaction conditions, this may be 5, 10, 15, 20, 25, 33, 50, 100, 150, 250, 500, or 1000 parts by weight of urea to 100 parts by weight of 10% MnO.sub.2/MgAl.sub.2O.sub.4, and optionally no more than 100,000, 50,000, 25,000, 10,000, 5,000, 1,000, 750, 500, 400, 333, 250, 125, 100, 75, 50, 25, 20, 15, or 10 parts by weight urea to 100 parts) to produce g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 (10:5:85, wt. %) nanocomposite. The quadruple mixture was returned and heated to 600 C. for 60 minutes in a covered porcelain crucible, and subsequently, the g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 (10:5:85, wt. %) nanocomposite was collected.

Example 2: Characterization

(72) X-ray diffraction (XRD) was used to identify the crystalline states in each specimen, employing the JDX-8030 X-ray, JEOL, made in Japan. Cu-filtered Cu-K radiation (1.5418 ) powered at 45 kV and 10 mA was used to run the patterns. The specimens were tested at ambient temperatures in a range of 2=5 to 80. The surface morphologies of the obtained samples were analyzed using images of transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM), obtained by a Tecnai-G20 (USA) transmission electron microscope with a 200 kV speed voltage.

Example 3: Electrical Measurements

(73) In certain aspects of the present disclosure, a two-probe method to measure an electrical conductivity (EC) of tablets having a diameter of about 10 millimeters (mm) and a thickness of about 1 mm. The tablets were manufactured by pressing powder under a 210.sup.3 kg/cm.sup.2 pressure. Silver paste was placed on both surfaces of each tablet. The tablets were placed in an oven to remove any moisture. The electrical conductivity, dielectric constant, dielectric loss, and impedance were measured, under typical room conditions, using a programmable automatic LCR bridge (model HIOKI IM 3536, Nagano, Japan) at a fixed voltage of about 1.0 V and frequencies between 1000 Hz and 2 MHz. The frequency dependent complex dielectric function may be expressed via Equation 1, as provided hereinafter:
**()=()j()(1)
where, j=1, the imaginary part of the permittivity is represented by , while the real part is represented by . Further, equation 2 and equation 3 were used to approximate the values for and , as provided below:
=Cd/ As(2)
()=c()tan (3)
where is the free space permittivity about and is equal to 8.8610.sup.12 F/m, d is the thickness, As is the cross-section area, Tan is the dissipative factor, (2f) is the electric field frequency.

Results and Discussion

(74) As mentioned above, XRD was used to examine the crystallinity and phase identification of the g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 catalyst, the results are depicted in FIG. 1. The high crystalline nature of the nanocomposite was indicated by sharp peaks and high-intensity values, as shown in FIG. 2. The diffraction patterns are compared to the standard COD cards to demonstrate the presence of MnO.sub.2, MgO, MgAl.sub.2O.sub.4, Al.sub.2O.sub.3, and g-C.sub.3N.sub.4 phases. The spinel diffraction of MgAl.sub.2O.sub.4 were recorded at 2 values of 44.8, 56.1, 59.5, 74.09, 78.1, 19.1, and 31.3. The standard COD card number 9001364 states that the above diffractions originated from the (111), (220), (400), (422), (511) (620), and (622) planes, respectively. MgO (COD card, No. 9000499) showed a cubic phase at 2 values of 42.8, 62.2, and 74.6. The (200), (220), and (311) are represented by the above-described lines, respectively. It was previously reported that MgO is present together with the MgAl.sub.2O.sub.4 spinel phase. The pyrolusite phase of MnO.sub.2 (COD No. 2105790) is closely matched with the diffraction lines seen at 28.4, 40.5, 44.9, 56.0, 66.4, and 79.1. According to COD No. 1534042, the g-C.sub.3N.sub.4 diffractions were detected at 18.8, 28.2, 35.5, 40.7, 44.6, and 73.7. Further, at 31.3, 34.3, and 61.6, Al.sub.2O.sub.3 traces were detected (COD No. 4002418). There were no further phases found, suggesting that g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 was successfully fabricated.

(75) Further, TEM images of g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanocomposite are shown in FIG. 2A. The TEM images show the well dispersion of homogeneous spherical metal oxides nanoparticles with a size of about 7.9 nm on two-dimensional porous structure constructed with curled and wrinkled nanosheets and platelets of the g-C.sub.3N.sub.4. The corresponding SAED pattern, shown in FIG. 2B, reveals diffraction spots with interplanar spacing of 0.298 nm, 0.205 nm, 0.146 nm, 0.133 nm due to (220, spinel), (400, spinel), (002, MnO.sub.2) and (211, Al.sub.2O.sub.3) diffraction planes, respectively. The corresponding HRTEM of the nanocomposite, depicted in FIG. 2C, shows a plane spacing of 0.242 nm and 0.20 nm related to (311), and (400) planes of spinel, and 0.22 nm related to (200) plane of MnO.sub.2, characterizing the heterostructure formation. The fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) measurements, as depicted in FIG. 2D and FIG. 2E, show a d value of about 0.34 nm given to g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanocomposite, signifying the lattice spacing of (002), indicating the development of spinel structure.

(76) Further, in general, the AC method distinguishes between several mechanisms, such as electrode response, grain boundary conduction, and grain conduction, that contribute to an overall conductivity of a material. The AC conductivity frequency dependence for the g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanocomposite, at room temperature, is shown in FIG. 3. Furthermore, equation 4 is utilized to determine the ac conductivity of every sample:
.sub.AC=.sup.0 tan (4)
where .sup.0 is the vacuum permittivity, is the dielectric constant, and tan depicts the loss tangent. As can be seen from FIG. 3, the AC conductivity increases with frequency, specifically at higher frequencies, since high frequency delivers a bigger pumping power to charge carriers, subsequently, the AC conductivity is highest at higher frequencies, as described by Rao and colleagues in J. Mater. Sci. 1997, 32, 6049e54, which is incorporated by reference herein. An increase in the hopping rate of charge between the charge carriers is sufficient to improve conductivity without increasing the number of charge carriers.

(77) According to present disclosure, the behavior of the nanocomposite as a multilayer capacitor of grains and grain boundaries, as predicted by the Koops model may be able to explain the increase in AC conductivity with temperature and frequency, as described by Sivakumar and coworkers in J. Korean Ceram. Soc. 2018, 55, 230e8, which is incorporated by reference herein. A practically continuous plateau area was seen at lower frequencies where the resistive grain boundaries were more active and prevent electronic charge carriers from hopping between such boundaries. However, the conductive grains were more active at higher frequencies, allowing charge carriers to hop between neighboring ions.

(78) The release of charge carriers trapped in small areas may lead to a rise in high-frequency conductivity, an increase in the force of the applied field, and increased migration and movement of the released charge carriers in different directions. Significant elements in the conduction of material behavior include liberated charge carriers and electron mobility among many metal ions, as described by Ahmed and colleagues in Mater. Lett. 2003, 57, 4256-4266, which is incorporated by reference herein. Materials used in semiconductors have the following frequency-dependent relationship, as depicted by equation 5:
.sub.AC()=A.sup.s(5)
where A and s are constants.

(79) A sudden hopping of the charge carriers results in translational motion if s less than 1, while a localized hopping of the species is indicated when s is more than 1, as described by Sen and colleagues in Mater. Chem. Phys. 2004, 87, 256-263, which is incorporated by reference herein. The effect is caused by the relaxation resulting from the movement of electrons or atoms by tunneling or hopping between equilibrium locations. The exponent s is determined by graphing the natural logarithm of .sub.AC () against the natural logarithm of (), as depicted in FIG. 4. The value of s was found to be around 0.6405, indicating that correlated barrier hopping (CBH) is the most likely mechanism in the g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanocomposite. In general, the relation between the conduction mechanism and s(f) behavior might suggest a suitable model of the conduction mechanism.

(80) The frequency dependence of the for the g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanocomposite at room temperature, is depicted in FIG. 5. In particular, FIG. 5 shows a dispersion in values as the frequency increases. At lower frequencies, the decline in value occurs very quickly, whereas at higher frequencies, approaching a constant value takes longer. In general, charge polarization is the storage of some energy in a substance when it is exposed to an external electric field. The stored energy is represented by the real component () of the dielectric constant. As mentioned above, FIG. 5 illustrates the effect of frequency on the dielectric constant of the examined materials at specific temperatures. The graph, as depicted in FIG. 5, indicates that for the nanocomposite, drops with increasing frequency. At lower frequencies, the decline was swift, while at higher frequencies, the decline was more gradual. The observed dielectric behavior may be explained by the hopping process and the idea of polarization, as described by Kambale and colleagues in Smart Mater. Struct. 2009, 18, 085014, which is incorporated by reference herein.

(81) The nanocomposite was presumed to be arranged of distinctive structures or regions (grain and grain boundaries) and the conductivity of the grain was higher than the grain boundary. Therefore, it is appropriate to say that the higher dielectric constant values were obtained from the charge accumulation at the grain boundaries.

(82) In general, according to the Koops theory, the interfacial polarization of the Maxwell-Wagner type may be used to analyze the dielectric dispersion curves, as described by Melagiriyappa et al. in Mater. Chem. Phys. 2008, 112, 68e73, which is incorporated by reference herein. The aforementioned models predict that the nanocomposite includes conductor rich grains separated by conductor-poor grain boundaries. The grain boundaries are more effective at low frequencies, whereas grains are more effective at higher frequencies.

(83) Further, the dielectric loss factor () specifies the quantity of energy lost due to charge carrier movement. The fluctuation of as a function of frequency for g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanocomposite at room temperature is shown in FIG. 6. The behavior obtained is comparable to that of the real part of the dielectric constant, as such, it decreases as the frequency increases. The value rapidly drops in the low-frequency region while remaining low in the high-frequency region. The observed trend may be elucidated by the fact that in the low-frequency region where the samples possess higher resistivity (because of the grain boundary), additional energy is needed to hop the charges between the cations, and thus, the loss is high. In the high-frequency region, where the samples have low resistivity (due to grains), less energy is involved in hopping the charges between the cations at the octahedral sites. The polarization of space charges may potentially cause a decrease in dielectric loss as the frequency increases.

(84) In general, impedance spectroscopy is a practical and effective method for establishing the relationship between the electrical characteristics and microstructures of substrates. Generally, the electrochemical impedance spectroscopy (EIS) spectra show distinct semicircles in complex impedance planes as they possess diverse relaxation times. The impedance responses caused by the grain border and the grain itself may overlap if the variation in time constants among the processes is less than one hundred. FIG. 7 depicts the complex impedance spectra for the g-C.sub.3N.sub.4@MnO.sub.2/MgAl.sub.2O.sub.4 nanocomposite, from which it can be observed that the complex impedance spectrum shows single depressed semicircle in the complex impedance plots at 303 Kelvin (K), as described by Mogu-Milankovi and coworkers in J. Phys. Chem. B 2016, 120, 3978-3987, which is incorporated by reference herein.

(85) The aspects of the present disclosure provide the method of storing electrical charge using the nanocomposite as synthesized herein. A plurality of examinations were conducted on the synthesized nanocomposite. In particular, the electrical conductivity values for the nanocomposite increased with increasing frequency indicating the semiconducting behavior of the nanocomposite. The variation of dielectric constant (), dielectric loss (), and ac conductivity for the investigated samples at different frequencies has been evaluated. Both dielectric constant () and dielectric loss () were decreased with the increase of frequency while AC conductivity increased. Knop's phenomenological theory explains the frequency variation of ( and ). The hopping of electrons and holes is suggested to be the electrical conduction mechanism.

(86) Numerous modifications and variations of the present disclosure are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.