Preparation methods of nitrogen-doped carbon quantum dots and their application in aluminum-air batteries

Abstract

This invention relates to the field of electrochemical technology, specifically to a method for preparing nitrogen-doped carbon quantum dots and their application in aluminum-air batteries. Using L-tryptophan and tannic acid as raw materials, a hydrothermal polymerization reaction is carried out, followed by filtration, dialysis, distillation, and freeze-drying to prepare carbon quantum dots. Different concentrations of carbon quantum dot corrosion inhibitors are added to the alkaline electrolyte of the aluminum-air battery. Electrochemical testing, hydrogen evolution analysis, and surface analysis reveal that this corrosion inhibitor can improve the anode utilization rate, capacity density, and energy density of the aluminum-air battery, while reducing the self-corrosion rate of the aluminum anode, meeting the requirements of metal-air batteries. The preparation process is simple, low-cost, and uses widely available, inexpensive, low-toxicity, and environmentally friendly raw materials, making it widely applicable in practical production.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, and in particular to a method for preparing nitrogen-doped carbon quantum dots and their application in aluminum-air batteries. Background Technology

[0002] Aluminum-air batteries use air and metallic aluminum as the positive and negative electrodes, offering advantages such as low cost, wide availability, and non-toxicity. The electrolyte in aluminum-air batteries is typically a neutral or alkaline solution. However, research indicates that metallic aluminum cannot be fully utilized in neutral electrolytes, limiting the specific energy density of aluminum-air batteries. While it can reach its full potential in alkaline solutions, minimizing raw material loss, the aluminum anode undergoes severe self-corrosion in alkaline solutions, releasing large amounts of hydrogen gas and affecting the stability of the aluminum-air battery and the utilization rate of the aluminum anode.

[0003] Studies have shown that adding a specified amount of corrosion inhibitor to the electrolyte can slow down or solve this problem. The corrosion inhibitor forms a thick protective coating on the aluminum surface through intermolecular bonding or the interaction between heteroatoms and aluminum atoms, thus protecting the metallic aluminum. In recent years, much research has been conducted on electrolyte additives for aluminum-air batteries, with green corrosion inhibitors such as plant extracts, ionic liquids, and pharmaceuticals being added to aluminum-air battery systems for investigation.

[0004] However, these corrosion inhibitors are still limited in practical applications due to their high cost, long processing time, complicated synthesis steps, or limited shelf life. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing nitrogen-doped carbon quantum dots and their application in aluminum-air batteries, which solves the problem that the above-mentioned corrosion inhibitors are still limited in practical applications due to their high cost, long time consumption, complicated synthesis steps, or limited shelf life.

[0006] To achieve the above objectives, the present invention provides a method for preparing nitrogen-doped carbon quantum dots, comprising the following steps:

[0007] L-tryptophan and tannic acid were dissolved and mixed to obtain a mixed solution;

[0008] The mixed solution is placed in a reaction vessel for hydrothermal reaction;

[0009] The solution after the hydrothermal reaction is filtered;

[0010] The filtered solution was purified to obtain a carbon quantum dot corrosion inhibitor.

[0011] The method further includes purifying the filtered solution to obtain a carbon quantum dot corrosion inhibitor.

[0012] The filtered solution is placed in a dialysis bag for dialysis.

[0013] The dialyzed solution is then distilled.

[0014] The distilled solution was freeze-dried in a freeze dryer to obtain carbon quantum dot corrosion inhibitor.

[0015] The method further includes dissolving and mixing L-tryptophan and tannic acid to obtain a mixed solution.

[0016] The concentration of tannic acid is 2-5 mmol, and the concentration of L-tryptophan is 85-90 mmol.

[0017] The method further includes placing the mixed solution into a reaction vessel for hydrothermal reaction.

[0018] The mixed solution is placed in a reaction vessel and subjected to a hydrothermal reaction at 150℃-200℃ for 8-15 hours.

[0019] The method further includes filtering the solution after the hydrothermal reaction.

[0020] The solutions after the hydrothermal reaction were filtered using 0.45 μm and 0.22 μm filter needles, respectively.

[0021] The method further includes placing the filtered solution into a dialysis bag for dialysis.

[0022] The filtered solution was semi-osmotically processed through a 500-1000MW dialysis bag, with distilled water being changed every 2 hours, for a total of 72 hours of continuous dialysis.

[0023] An application of nitrogen-doped carbon quantum dots in an aluminum-air battery involves adding the prepared carbon quantum dot corrosion inhibitor to the electrolyte of an alkaline aluminum-air battery.

[0024] The concentration of the carbon quantum dot corrosion inhibitor is 10-150 mg.

[0025] This invention discloses a method for preparing nitrogen-doped carbon quantum dots and their application in aluminum-air batteries. Using L-tryptophan and tannic acid as raw materials, a hydrothermal polymerization reaction is carried out. Carbon quantum dots are prepared through filtration, dialysis, distillation, and freeze-drying. Different concentrations of carbon quantum dot corrosion inhibitors are added to the alkaline electrolyte of the aluminum-air battery. Electrochemical testing, hydrogen evolution analysis, and surface analysis reveal that this corrosion inhibitor can improve the anode utilization rate, capacity density, and energy density of the aluminum-air battery, while reducing the self-corrosion rate of the aluminum anode, meeting the requirements of metal-air batteries. The preparation process is simple, low-cost, and uses widely available and inexpensive raw materials. Furthermore, as an amino acid derivative, it possesses certain environmental friendliness. It is a green and highly efficient corrosion inhibitor, low in toxicity and environmentally friendly. It exhibits good inhibition of the self-corrosion of metallic aluminum in alkaline solutions and is a pale yellow granule at room temperature, easily soluble in alkaline solutions and ethanol. The synthesis process of this invention is simple, the operation is straightforward, the raw materials are inexpensive, and the temperature is suitable, making it widely applicable in practical production. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0027] Figure 1 The Nyquist plots are of metallic aluminum in alkaline solutions containing different concentrations of amino acid carbon quantum dot corrosion inhibitors.

[0028] Figure 2 These are the electrochemical Bode fitting spectra of implementation cases 1-4, including impedance-frequency and phase angle-frequency plots.

[0029] Figure 3 This is a polarization curve of metallic aluminum in 4M NaOH solution with different formulations of amino acid carbon quantum dot corrosion inhibitors.

[0030] Figure 4 These are the polarization curves of metallic aluminum in 4M NaOH solution and in Example 4.

[0031] Figure 5 These are voltage curves of metallic aluminum in 4M NaOH solution and those obtained in Example 4 at different current densities.

[0032] Figure 6 This is a SEM image of metallic aluminum obtained from a test in 4M NaOH solution.

[0033] Figure 7 This is a SEM image of metallic aluminum obtained in Example 4.

[0034] Figure 8 This is the equivalent circuit diagram of embodiments 1-4 of the present invention.

[0035] Figure 9 This is a flowchart illustrating the steps of the method for preparing nitrogen-doped carbon quantum dots according to the present invention.

[0036] Figure 10 This is a flowchart illustrating the steps of purifying the filtered solution to obtain a carbon quantum dot corrosion inhibitor according to the present invention. Detailed Implementation

[0037] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, but should not be construed as limiting the present invention.

[0038] The first embodiment of this application is as follows:

[0039] Please see Figure 9 and Figure 10 ,in, Figure 9 This is a flowchart illustrating the steps of the method for preparing nitrogen-doped carbon quantum dots according to the present invention. Figure 10 This invention provides a method for preparing nitrogen-doped carbon quantum dots, comprising the following steps: [The diagram shows the steps of purifying the filtered solution to obtain a carbon quantum dot corrosion inhibitor.]

[0040] S101: Dissolve and mix L-tryptophan and tannic acid to obtain a mixed solution.

[0041] Specifically, 2-5 mmol, preferably 3 mmol, of tannic acid and 85-90 mmol, preferably 88 mmol, of L-tryptophan are dissolved in 30-40 ml of deionized water or distilled water and mixed evenly, wherein the molar mass ratio of tannic acid to L-tryptophan is 3-88 mmol / L: 5-18 g.

[0042] S102: The mixed solution is placed in a reaction vessel for hydrothermal reaction.

[0043] Specifically, the mixed solution is placed in a 50ml reaction vessel for hydrothermal reaction at a temperature of 150-200℃, preferably 180℃, for a reaction time of 8-15h, preferably 12h.

[0044] S103: Filter the solution after the hydrothermal reaction.

[0045] Specifically, after heating to carry out the synthesis reaction, the mixture is filtered using 0.45μm and 0.22μm filter needles.

[0046] S104: The filtered solution is purified to obtain carbon quantum dot corrosion inhibitor.

[0047] S1041: Place the filtered solution into a dialysis bag for dialysis;

[0048] S1042: Distill the dialyzed solution;

[0049] S1044: The distilled solution is placed in a freeze dryer for freeze drying to obtain carbon quantum dot corrosion inhibitor.

[0050] Specifically, the filtered solution is dialyzed in a dialysis bag of 500-1000MW, preferably 500MW, with distilled water changed every 2 hours, and the continuous dialyzing time is 48-72 hours, preferably 72 hours. The solution is then filtered under reduced pressure, heated to 70-90℃, preferably 85℃, for evaporation and concentration, and freeze-dried for 72 hours to obtain the purified amino acid carbon quantum dot corrosion inhibitor.

[0051] Using L-tryptophan and tannic acid as raw materials, an amino acid carbon quantum dot corrosion inhibitor with a network structure is formed through a hydrothermal method. This inhibitor forms a barrier film on the metal surface through molecular adsorption, protecting the metal surface and slowing down the self-corrosion rate of aluminum without damaging the original performance of the aluminum-air battery. This allows the anode utilization rate of the battery to reach over 80%, meeting the requirements of metal-air batteries. The preparation process is simple, low-cost, and uses widely available and inexpensive raw materials. Furthermore, as an amino acid derivative, it possesses certain environmental benefits. This amino acid carbon quantum dot corrosion inhibitor is a green, highly efficient, low-toxicity, and environmentally friendly agent. It exhibits good inhibition of aluminum self-corrosion in alkaline solutions and is a pale yellow granule at room temperature, easily soluble in alkaline solutions and ethanol. The synthesis process is simple, the operation is straightforward, the raw materials are inexpensive, and the temperature is suitable, making it widely applicable in practical production.

[0052] The second embodiment of this application is as follows:

[0053] Based on the first embodiment, this embodiment describes the application of nitrogen-doped carbon quantum dots in an aluminum-air battery by adding the prepared carbon quantum dot corrosion inhibitor to the electrolyte of an alkaline aluminum-air battery.

[0054] The concentration of the carbon quantum dot corrosion inhibitor is 10-150 mg.

[0055] Specifically, different concentrations of carbon quantum dot corrosion inhibitors were added to alkaline electrolytes, and tests were conducted using electrochemical methods, hydrogen evolution tests, and surface analysis. The results showed that this corrosion inhibitor can improve the anode utilization rate, capacity density, and energy density of aluminum-air batteries, while simultaneously reducing the self-corrosion rate of the aluminum anode.

[0056] Example 1:

[0057] The effect of amino acid carbon quantum dot corrosion inhibitor concentration on the performance of aluminum-air batteries:

[0058] Weigh 10 mg of amino acid carbon quantum dot corrosion inhibitor and add it to a prepared 4M NaOH solution at room temperature (25℃). Using 4M NaOH as the solvent, add the amino acid carbon quantum dot corrosion inhibitor, stir well, and then bring the volume to 250 mL. Shake the volumetric flask to disperse the quantum dots evenly in the alkaline solution. Perform electrochemical testing on the prepared solution, then under constant circulation conditions (controlling the flow rate at a constant 5 mL / min).

[0059] Example 2:

[0060] The effect of amino acid carbon quantum dot corrosion inhibitor concentration on the performance of aluminum-air batteries:

[0061] Weigh 50 mg of amino acid carbon quantum dot corrosion inhibitor and add it to a prepared 4M NaOH solution at room temperature (25℃). Using 4M NaOH as the solvent, add the amino acid carbon quantum dot corrosion inhibitor, stir well, and then bring the volume to 250 mL. Shake the volumetric flask to disperse the quantum dots evenly in the alkaline solution. Perform electrochemical testing on the prepared solution, then under constant circulation conditions (controlling the flow rate at a constant 5 mL / min).

[0062] Example 3:

[0063] The effect of amino acid carbon quantum dot corrosion inhibitor concentration on the performance of aluminum-air batteries:

[0064] Weigh 100 mg of amino acid carbon quantum dot corrosion inhibitor and add it to a prepared 4M NaOH solution at room temperature (25℃). Using 4M NaOH as the solvent, add the amino acid carbon quantum dot corrosion inhibitor, stir well, and then bring the volume to 250 mL. Shake the volumetric flask to disperse the quantum dots evenly in the alkaline solution. Perform electrochemical testing on the prepared solution, then under constant circulation conditions (controlling the same flow rate, 5 mL min⁻¹).

[0065] Example 4:

[0066] The effect of amino acid carbon quantum dot corrosion inhibitor concentration on the performance of aluminum-air batteries:

[0067] Weigh 150 mg of amino acid carbon quantum dot corrosion inhibitor and add it to a prepared 4M NaOH solution at room temperature (25℃). Using 4M NaOH as the solvent, add the amino acid carbon quantum dot corrosion inhibitor, stir well, and then bring the volume to 250 mL. Shake the volumetric flask to disperse the quantum dots evenly in the alkaline solution. Perform electrochemical testing on the prepared solution, then under constant circulation conditions (controlling the flow rate at a constant 5 mL / min).

[0068] Table 1 shows the fitting results of the impedance spectra of Al-1060 in the electrolytes prepared in Examples 1-4.

[0069]

[0070] Table 2 shows the Tafel data results for the electrolytes prepared with Al-1060 in Examples 1-4.

[0071]

[0072] Optimal performance test of aluminum-air battery: The amino acid carbon quantum dot corrosion inhibitor prepared in (Case 1) was added to the electrolyte, and 10mg, 50mg, 100mg and 150mg of amino acid carbon quantum dot additives were added respectively.

[0073] Table 1-2 and Figure 1-3 The test results of implementation cases 1-4 are shown. The increase in corrosion inhibition efficiency can be seen from the change in electrochemical potential, the gradual increase in the radius of the impedance spectrum, and the decrease in the corrosion current density (icoor). It can also be seen that implementation case 4 is the best choice, with a corrosion inhibition efficiency of 68.37%. Figure 4 , Figure 5 Data for aluminum-air batteries tested in 4M NaOH solution and in Example 4 are presented. In Example 4, the power density of metallic aluminum reached 78.64 mW cm⁻², and the anode utilization rate reached 85%. Compared with the anode utilization rate (41.4%) and power density (53.63 mW cm⁻²) measured in 4M NaOH solution, the battery performance was significantly improved after the addition of amino acid carbon quantum dot corrosion inhibitor, and the voltage remained stable under different current densities. Figure 6 , Figure 7 This indicates that quantum dots form a protective film on the aluminum surface, slowing down the self-corrosion of the aluminum and protecting the aluminum surface. Figure 8 To fit the circuit diagram.

[0074] The above-disclosed embodiments are merely one or more preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art can understand that all or part of the processes for implementing the above embodiments and equivalent changes made in accordance with the claims of this application still fall within the scope of this application.

Claims

1. A method for preparing nitrogen-doped carbon quantum dots, characterized in that, Includes the following steps: L-tryptophan and tannic acid are dissolved and mixed to obtain a mixed solution, wherein the concentration of tannic acid is 2-5 mmol and the concentration of L-tryptophan is 85-90 mmol. The mixed solution is placed in a reaction vessel for hydrothermal reaction, wherein the hydrothermal reaction is carried out at 150℃-200℃ for 8-15 hours. The solution after the hydrothermal reaction was filtered, using 0.45μm and 0.22μm filter needles, respectively. The filtered solution was purified to obtain a carbon quantum dot corrosion inhibitor. The filtered solution was placed in a 500-1000MW dialysis bag for dialysis, with distilled water replaced every 2 hours for a total of 72 hours. The solution was then filtered under reduced pressure and heated to 70-90℃. The dialyzed solution was then distilled. The distilled solution was then freeze-dried in a freeze dryer for 72 hours to obtain the carbon quantum dot corrosion inhibitor.

2. An application of nitrogen-doped carbon quantum dots in aluminum-air batteries, comprising a carbon quantum dot corrosion inhibitor prepared using the method for preparing nitrogen-doped carbon quantum dots as described in claim 1, characterized in that... The prepared carbon quantum dot corrosion inhibitor was added to the electrolyte of an alkaline aluminum-air battery.

3. The application of nitrogen-doped carbon quantum dots in aluminum-air batteries as described in claim 2, characterized in that, The concentration of the carbon quantum dot corrosion inhibitor is 10-150 mg.

Images