Barium chromate nanocomposite material using nitrogen-doped graphene oxide intercalation, preparation method and application thereof

Abstract

The present invention relates to the technical field of nanocomposite material preparation, and discloses a barium chromate (BaCr2O4) nanocomposite material using nitrogen-doped graphene oxide intercalation, a preparation method, and its application. The preparation method comprises the following steps: (1) synthesizing barium chromate; and (2) synthesizing a BaCr2O4@GO nanostructured composite material. The BaCr2O4@GO nanocomposite material has a high storage capacity and is suitable for use as a supercapacitor electrode material.

Description

Technical Field

[0001] The present invention relates to the technical field of nanocomposite material preparation, and in particular to a barium chromate (BaCr2O4) nanocomposite material using nitrogen-doped graphene oxide intercalation, a preparation method and applications thereof. Background Art

[0002] In recent decades, carbon nanotubes, fullerenes, and graphene oxide have garnered significant interest among researchers, primarily for structural and morphological characterization, particularly for applications in sensors and supercapacitors. Supercapacitors are categorized into three main types based on their electrochemical reaction mechanism: electric double-layer capacitors (EDLCs), pseudocapacitors, and hybrid capacitors. Transition metal chromates, particularly MCr2O4, have demonstrated exceptional conductivity and electrochemical properties, making them highly favored for supercapacitor applications due to their excellent rate capability and electron transport capacity. Graphene / Cr2O4, activated carbon / Cr3O4, and CuO / graphene oxide are examples of three-dimensional nanostructured materials that have recently garnered attention as promising electrode materials for glucose sensors and supercapacitors. This preference is likely due to their improved electrochemical properties, robust electrocatalytic activity, and enhanced chemical stability. However, the relatively low specific capacitance and energy density of these carbon-based electrodes have thus far hindered their widespread application in real-world devices (https: / / doi.org / 10.1021 / nn3057388). Pseudocapacitors fabricated from various metal oxides, metal hydroxides, or conductive polymers exhibit higher specific capacitance than EDLCs. However, the realization of commercially viable redox capacitors remains hampered by their insufficient electrical conductivity. Poor electron transport and severe damage to electrode materials during redox reactions in pseudocapacitors remain challenging (https: / / doi.org / 10.1016 / j.electacta.2010.10.070).

[0003] The current study focuses on the synthesis of nanosheet-structured graphene oxide (BaCr2O4@GO) composites via hydrothermal method assisted by sonication, aimed at supercapacitor applications. The nanostructured composites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and morphological analysis. XRD and FTIR results showed that the graphene oxide nanoparticles were arranged in a honeycomb pattern, indicating that the nanosheets were composed of nitrogen-doped graphene oxide. In addition, transmission electron microscopy images showed the presence of cauliflower-like structures in the composite morphology, which was attributed to the effective intercalation of graphene oxide during the thermal reduction process. The electrochemical performance of the nanocomposites was compared with previous studies on metal chromate materials aimed at improving supercapacitor applications. Analysis of gammavoltammetric constant-current charge-discharge (GCD) data showed that the power density values of the nanocomposites ranged from 292 W kg -1 Increased to 495.5Wkg -1 . The ability to strike a balance between increased power density and efficient ion transport makes the nanocomposite a valuable candidate for advancing supercapacitor performance. The significant increase in power density highlights the ability of the BaCr2O4@GO nanocomposite to provide more energy yield during charge and discharge cycles. Due to its low energy density, the nanocomposite can release this energy quickly and efficiently, making it an attractive candidate for high-performance electrodes. The efficient intercalation of nitrogen-doped graphene oxide during the thermal reduction process leads to the enhanced morphology and electrochemical properties of the BaCr2O4@GO composite. Summary of the Invention

[0004] This study employs BaCr2O4 electrodes with different nanostructured morphologies to enhance their electrochemical properties for catalytic and supercapacitor applications. Excellent supercapacitor performance has been demonstrated using three electrode configurations: mixed metal oxides such as Cr2O4 / Ni(OH)2, 3D graphene / Cr3O4, CoMoO4, CrO / GO, activated carbon / Cr3O4, and Cu@Cu2O composites. This discovery investigates the electrochemical, morphological, and structural properties of BaCr2O4 composite electrode materials for symmetric supercapacitor applications using a 1M KOH electrolyte.

[0005] In order to achieve the above technical objectives, the technical solutions of the present invention are as follows:

[0006] A method for preparing a BaCr2O4 nanocomposite material using nitrogen-doped graphene oxide intercalation comprises the following steps:

[0007] (1) Synthesis of barium chromate

[0008] In a beaker containing water, barium nitrate and chromium nitrate are mixed. The solution is continuously stirred and heated on a hot plate. After the mixture becomes homogeneous, ethanol is added. The temperature is then raised while stirring continuously to evaporate the solution. The gel is dried in an oven to obtain a powder after complete drying. The powder is then sintered in a furnace. Finally, a fine powder is obtained by grinding.

[0009] (2) Synthesis of BaCr2O4@GO nanostructured composites

[0010] GO was ultrasonically treated in water while being heated and continuously stirred. Solutions of barium nitrate and chromium nitrate were mixed. Polyvinyl pyrrolidone and ammonia were added to the GO solution, followed by the resulting solution. The reaction mixture was heated and stirred continuously. After the reaction mixture was washed several times with an ethanol / water mixture, the sample was purified. Finally, the material was calcined to obtain a BaCr2O4 nanocomposite material intercalated with nitrogen-doped graphene oxide.

[0011] Furthermore, in step (1), the solution was continuously stirred and heated on a hot plate for 20 minutes until the temperature reached 40-50°C.

[0012] Furthermore, ethanol is added in step (1), and then the temperature is raised to 60-70°C.

[0013] Furthermore, in step (1), the gel was dried using a DHG-9202 oven at 105° C. for two hours.

[0014] Furthermore, in step (1), the powdered BaCr2O4 was sintered in a VULCAN-D550 furnace at a temperature of 800°C for three hours.

[0015] Furthermore, in step (2), GO is ultrasonically treated in water for 1 hour.

[0016] Furthermore, in step (2), the reaction mixture is heated to 95° C. and stirred continuously for 10 hours.

[0017] Furthermore, in step (2), the sample was purified at 95°C, and finally, the material was calcined at 450°C for 12 hours.

[0018] The present invention also provides an application of a BaCr2O4 nanocomposite material intercalated with nitrogen-doped graphene oxide in a three-electrode device for use in a supercapacitor.

[0019] Compared with the prior art, the advantages of the present invention are:

[0020] 1. This invention relates to the preparation of cost-effective electrodes using barium chromate (BaCr2O4) with different nanostructures, aiming to improve their electrochemical properties for use in catalysis and supercapacitors. Nanosheet-shaped graphene oxide (BaCr2O4@GO) composites designed for supercapacitor applications have been successfully synthesized via a hydrothermal process assisted by sonication. The advantages of the testing technology are as follows:

[0021] (1) The main advantage of the present invention is that nanosheet graphene oxide (BaCr2O4@GO) composites are prepared by a very simple, cost-effective and environmentally friendly method.

[0022] (2) The nanocomposite materials of the present invention show the potential to improve the performance of supercapacitors, increasing power density while maintaining efficient ion movement.

[0023] (3) The significantly improved power density of the present invention highlights the ability of BaCr2O4@GO nanocomposites to produce more energy per unit mass during charge and discharge cycles.

[0024] (4) Due to their low energy density, the nanocomposites of the present invention are able to release stored energy quickly and efficiently, making them attractive options for high-performance electrode applications.

[0025] (5) The BaCr2O4@GO nanocomposite material of the present invention has a high storage capacity and is suitable for use as a supercapacitor electrode material.

[0026] 2. Common technical issues in previous technologies include limitations in achieving optimal ion transport efficiency, challenges associated with the scalability and cost-effectiveness of synthetic methods, stability and cycling performance issues, and concerns about industrial applications.

[0027] The present invention addresses these challenges by providing a novel synthesis method that combines sonication and hydrothermal processes. Due to this synthesis method, the resulting composite material exhibits a honeycomb configuration composed of nitrogen-doped graphene oxide nanosheets, which facilitates efficient ion transport. The cauliflower-like structure observed in the morphology further enhances the intercalation of graphene oxide during the thermal reduction process, thereby significantly improving the power density. Therefore, the present invention represents a significant advancement in the field of supercapacitors, providing a balance between performance improvement and practical feasibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 .(a)&(b) show the XRD results and Raman spectra of GO and BaCr2O4@GO composites, respectively, as shown in (c) and (d).

[0029] Figure 2 .SEM morphology of (a) GO and (b) BaCr2O4@GO composites.

[0030] Figure 3 .SEM-EDS morphology of BaCr2O4@GO composite material.

[0031] Figure 4 .TEM examination of BaCr2O4@GO composite material, where (a) is GO and (b) is SAED pattern.

[0032] Figure 5 .(a) Graphene oxide (b) Photoluminescence of BaCr2O4@GO composite material in the visible range.

[0033] Figure 6 Band gap energy of (a) graphene oxide (GO) (b) BaCr2O4@GO nanocomposites.

[0034] Figure 7 Electrochemical characteristics of the BaCr2O4@GO electrode, including (a) current density, (b) GCD, (c) current density change vs. capacitance behavior, (d) GCD cycle number vs. capacitance retention, and (e) EIS data. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] a. Synthetic barium chromate

[0037] In a 50-ml beaker containing deionized water, first mix barium nitrate and chromium nitrate. Heat the solution on a hot plate for 20 minutes while stirring continuously, until the temperature reaches 40-50°C. After the mixture becomes homogeneous, gradually add 20 ml of ethanol as a chelating agent. To achieve the desired brown gel, increase the temperature to 60-70°C while stirring continuously to evaporate the solution. Dry the gel at 105°C for two hours using a DHG-9202 oven. A brown powder is obtained after complete drying. The powdered BaCr2O4 is then sintered in a VULCAN-D550 furnace at 800°C for three hours. Finally, grind the sample using an agate motor to obtain a fine powder.

[0038] b. Synthesis of BaCr2O4@GO nanostructured composites

[0039] To prepare the BaCr2O4@GO composite material, the present invention is carried out according to the following steps: First, 0.85 g of pure GO is ultrasonically treated in 250 ml of distilled water for 1 hour to obtain proper dispersion. In 250 ml of double distilled water (DI), a 0.1 M solution of barium nitrate (Ba(NO3)2·5H2O) and chromium nitrate is mixed while heating and continuously rotating. 1 g of polyvinyl pyrrolidone (PVP) and 40 ml of ammonia are added to the GO solution, followed by the resulting solution. The reaction mixture is heated to 95°C and stirred continuously for 10 hours. After the reaction mixture is washed several times with an ethanol / water mixture, the sample is purified at 95°C. Finally, the material is calcined at 450°C for 12 hours. Figure 1 As shown, the dried BaCr2O4@GO composite samples were collected and characterized to evaluate their potential use as supercapacitors.

[0040] c. Construction of electrodes for supercapacitor research using a three-electrode setup

[0041] Carbon black, 80% active composite material, and 10% polyvinylidene fluoride (PVDF) are the three components used to make the active electrode. A nickel wire electrode material was coated with the resulting mixture and then dried in an oven set at 95°C for one hour. This established the electrode arrangement. Symmetrical supercapacitors were electrochemically studied using a CHI 660C instrument and 1 M potassium hydroxide (KOH) electrolyte. This arrangement may make it easier to analyze the electrochemical performance of the supercapacitor device.

[0042] d. Material characterization

[0043] The present invention uses Cu-Kα radiation (Riken D / max) for X-ray diffraction analysis to confirm the structure of the composite material. Raman spectra of the composite samples can be obtained using a Horiba Scientific (Spex Industries) Raman instrument. Morphological characterization is performed using a JEOL JEM-2100F transmission electron microscope (TEM). A Hitachi S-4300 field emission scanning electron microscope (FE-SEM) is also used. This extensive range of investigations reveals the elemental composition, structure, vibrational, and morphological characteristics of the composite material.

[0044] Structural properties of BaCr2O4@GO composites

[0045] The development of sonochemical combined with hydrothermal techniques is crucial for the successful synthesis of composite materials for application in supercapacitors. Figure 2a shows the X-ray diffraction analysis of graphene oxide, 2θ = 11.60, 38.30 and 44.30 corresponding to the (001), (100) and (101) hkl values of JCPDS card number 75-2078, clearly indicating a hexagonal symmetric structure

[22] . Due to the presence of oxygen between the layered structures, the d spacing value changes from 3.3°A of graphite to 7.6°A of graphene oxide, indicating a nanoscale crystalline structure, calculated using the Debye-Scherr formula D = Kλ / βcosθ [23-25]. Figure 2 In b, the structural confirmation of X-ray diffraction (XRD) results is shown. The red color represents the 2θ peaks at the (110), (002), (111), (202), (020), (202), (113), (311), (220), (311) and (222) planes of BaCr2O4@GO material, confirming their presence on the GO surface (JCPDS, Card No. 98-005-2230). Similarly, in Figure 2 In b, the black color represents the GO results. It is observed that with reduction, both the average number of graphene layers and the average sp2 crystal size (L) decrease from 17 to 3 and from 16.86 nm to 14.50 nm, respectively. In comparison, the crystal size of BaCr2O4@GO is measured to be 12 nm.

[0046] The morphological characteristics of the merged results are as follows Figure 2 As shown. The results showed that FE-SEM images taken at lower and higher magnifications showed a uniform distribution of nanosheets with nanostructured topology. These nanosheets contained GO and BaCr2O4@GO nanoparticles embedded in a cauliflower-like structure. GO-N had the narrowest particle size distribution, ranging from 2.6 to 10.8 μm. On the other hand, the grain size of BaCr2O4@GO was found to be 2.9 nm using Image J software analysis. The nanosheets in both composites showed connections with the nanoparticles, and the diameter of the particles was about (20-30) nm. This is because there are more connected sheets, which means there are more active edges and surface features. These factors help improve the performance of supercapacitors. In addition, Figure 3 The SEM-EDX results of the composites are shown, confirming the elements and composition of the two composites. We compared the structural and morphological characteristics of the nanostructured BaCr2O4@GO composites with earlier reported metal chromate materials with the aim of improving supercapacitor applications.

[0047] In order to better understand the morphological properties of BaCr2O4@GO nanosheet composites, high-resolution transmission electron microscopy (HR-TEM) images and selected area electron diffraction (SAED) patterns were analyzed, respectively. Figure 4(a) and 4(b). Based on the TEM results, the obtained nanoparticles and nanosheets were confirmed to have nanostructures, in which BaCr2O4@GO dominated the nanosheets. When subjected to a controlled nanoscale hydrothermal reaction, the nanoparticles of GO and BaCr2O4@GO were uniformly distributed on the nanosheet structure. These BaCr2O4@GO nanoparticles showed a highly structured SAED pattern ( Figure 4 ), which confirms their polycrystalline structure and is in good agreement with the X-ray diffraction (XRD) results.

[0048] PL spectrum (photoluminescence spectrum)

[0049] The study of photoluminescence spectroscopy aims to analyze the electron-hole recombination process and calculate the band gap at a specific energy state. The optical properties of the nanoparticles are faithfully reflected in the formation of nanocomposites, e.g. Figure 5 As shown in Figure 2, spectra of GO and its BaCr2O4@GO nanocomposite were acquired at room temperature using a 40 MW He-Cd laser at a wavelength of 325 nm. Applying the formula Eg = 1240 / λ, the band gap of GO was calculated to be approximately 2.09 eV. Furthermore, the estimated optical band gap of the BaCr2O4@GO nanocomposite in the visible region is approximately 2.21 eV, a reliable indicator of nanoparticle distribution, primarily attributed to the recombination of electron-hole pairs involving sp2-hybridized carbon atoms. The close proximity of the ground state to the valence band (VB) and conduction band (CB) leads to the generation of negative charges through a complex photoluminescence mechanism. This, in turn, accelerates the charge motion of the BaCr2O4@GO nanocomposite upon light irradiation. The interaction between negative and positive charges in aqueous media generates free radicals on the surface of the illuminated BaCr2O4@GO nanocomposite.

[0050] UV-Vis spectrophotometry is a technique related to the absorption of ultraviolet (UV) and visible light by nanomaterials. Figure 6The absorption spectra of graphene oxide (GO) BaCr2O4@GO nanocomposites in the UV-visible range (200-600 nm) are presented. For GO, the UV absorption spectrum shows a smooth distribution of nanoparticles at 325 nm. In contrast, for the BaCr2O4@GO nanocomposites, the absorption edge shifts significantly to 330 nm [45,46]. For GO, the band gap calculated from the Tauc plot is 2.09 eV. In contrast, the band gap of the aluminum-BaCr2O4@GO nanocomposites has decreased to 2.21 eV. This decrease can be attributed to quantum size effects, which lead to a narrowing of the band gap. The results of UV-Vis spectrophotometry provide valuable insights into the optical properties and electronic transitions of individual nanomaterials and their composite structures, providing essential information for applications in sensors, catalysis, and other optoelectronic devices.

[0051] The cyclic voltammetry (CV) results of BaCr2O4@GO composite electrode are shown in Figure 2. Figure 7 As shown, cyclic voltammetry (CV) curves were performed in 1 M KOH solution at different scan rates (5, 10, 20, 30 and 50 mV s-1) with a fixed potential window ranging from -0.30 to 0.56 V. Figure 7 a shows the results of electrochemical impedance spectroscopy (EIS), Figure 7 b shows the changing behavior of current density and capacitance, Figure 7 d shows the relationship between the number of GCD cycles and the capacitance retention rate, Figure 7 e shows the GCD itself. At constant voltage, the results indicate that the electrode exhibits electric double layer capacitance (EDLC) behavior. If the material exhibits capacitive behavior, as the scan rate increases, we can see the corresponding Ba in the composite 2+ ion changes, which indicates excellent electric double layer capacitance. Due to the transformation of GO nanoparticles between various chromium oxidation states, the BaCr2O4@GO electrode shows pseudo-capacitor behavior of GO in addition to EDLC (GO). Previous studies have confirmed the role of graphene oxide in electrochemical reactions or redox behavior transformations. To find the capacitance value, we add the charge in the CV curve, which shows the change in specific capacitance at different rates. The diverse morphology and structural topology of the composite material improves the specific capacitance of the electrochemical reaction and provides excellent cycling stability.

[0052] The above description is only used to understand the method and core idea of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made to the present invention without departing from the principles of the present invention. These improvements and modifications also fall within the scope of protection of the rights of the present invention.

Claims

1. A method for preparing a BaCr2O4 nanocomposite material using nitrogen-doped graphene oxide intercalation, characterized in that: The following steps are involved: GO was ultrasonically treated in water while being heated and continuously stirred. Solutions of barium nitrate and chromium nitrate were mixed. Polyvinyl pyrrolidone and ammonia were added to the GO solution, followed by the resulting solution. The reaction mixture was heated and stirred continuously. After the reaction mixture was washed several times with an ethanol / water mixture, the sample was purified. Finally, the material was calcined to obtain a BaCr2O4 nanocomposite material intercalated with nitrogen-doped graphene oxide.

2. The method for preparing a BaCr2O4 nanocomposite material using nitrogen-doped graphene oxide intercalation according to claim 1, wherein: GO was sonicated in water for 1 h.

3. The method for preparing a BaCr2O4 nanocomposite material using nitrogen-doped graphene oxide intercalation according to claim 1, characterized in that: The reaction mixture was heated to 95°C and stirred continuously for 10 hours.

4. The method for preparing a BaCr2O4 nanocomposite material using nitrogen-doped graphene oxide intercalation according to claim 1, wherein: The sample was purified at 95 °C and finally, the material was calcined at 450 °C for 12 h.

5. A BaCr2O4 nanocomposite material prepared by the method according to any one of claims 1 to 4 using nitrogen-doped graphene oxide intercalation.

6. Use of the BaCr2O4 nanocomposite material with nitrogen-doped graphene oxide intercalation according to claim 5 in a three-electrode device for supercapacitor construction.

Images