Preparation method of nitrogen-sulfur-doped carbon quantum dots, prepared nitrogen-sulfur-doped carbon quantum dots and application of nitrogen-sulfur-doped carbon quantum dots

Abstract

The invention relates to the field of corrosion inhibitors, and discloses a preparation method of nitrogen-sulfur-doped carbon quantum dots, the prepared nitrogen-sulfur-doped carbon quantum dots and application of the nitrogen-sulfur-doped carbon quantum dots, the preparation method comprises the steps that pretreated peanut cake residue powder and thiosemicarbazide are dissolved in a solvent to form electrolyte, an anode and a cathode are inserted into the electrolyte, and the nitrogen-sulfur-doped carbon quantum dots are obtained. According to the preparation method, peanut cake residues are used as raw materials, the raw materials are wide in source, available, low in price, non-toxic, good in biocompatibility and rich in carbon atoms and heteroatoms, and the nitrogen-sulfur-doped carbon quantum dots are obtained. The prepared nitrogen-sulfur-doped carbon quantum dots contain rich N and S functional groups, and have a good corrosion inhibition effect on acid pickling of copper-nickel alloy at different temperatures.

Description

Technical Field

[0001] The present invention relates to the field of corrosion inhibitors, and particularly to a preparation method of nitrogen and sulfur co-doped carbon quantum dots, the prepared nitrogen and sulfur co-doped carbon quantum dots, and their applications. Background Art

[0002] Copper-nickel alloy materials are widely used in the cooling water pipes of the main and auxiliary engines of ships, the fire pipelines of offshore oil production platforms, the heat exchangers of power plants, the condensers of coastal nuclear power plants, and the brine heaters of multi-stage flash evaporation devices for seawater desalination due to their excellent properties. During operation, inorganic deposits mixed with corrosion products usually form on the surfaces of these alloy pipes. These deposits reduce the heat transfer efficiency and the quality of fluid flow. In addition, these deposits can also cause deposition-induced corrosion, ultimately endangering the service life of the equipment. In the past, pickling was often used to clean these deposits, and the acids used in pickling included hydrochloric acid, sulfuric acid, citric acid, carbamic acid, etc., and even included complexing agents such as ethylenediaminetetraacetic acid. Although the pickling method can remove the deposits, it will inevitably cause certain corrosion to the metal during the pickling process.

[0003] Corrosion inhibitors can effectively reduce the corrosion rate. Adding corrosion inhibitors to the pickling solution can effectively inhibit the corrosion behavior of copper-nickel alloys. Corrosion inhibitors can generally be divided into two categories: inorganic corrosion inhibitors and organic corrosion inhibitors. However, most of the existing inorganic and organic corrosion inhibitors are toxic and harmful to the environment. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problems that the corrosion inhibitors in the prior art are toxic and harmful to the environment, and to provide a preparation method of nitrogen and sulfur co-doped carbon quantum dots, the prepared nitrogen and sulfur co-doped carbon quantum dots, and their applications. The nitrogen and sulfur co-doped carbon quantum dots prepared by the present invention have wide and accessible raw material sources, are non-toxic, have good biocompatibility, and are rich in carbon atoms and heteroatoms. Therefore, the prepared nitrogen and sulfur co-doped carbon quantum dots have good corrosion inhibition efficiency.

[0005] To achieve the above purpose, in the first aspect of the present invention, a preparation method of nitrogen and sulfur co-doped carbon quantum dots is provided. The preparation method includes: dissolving pretreated peanut cake residue powder and thiosemicarbazide in a solvent to form an electrolyte solution, inserting an anode and a cathode into the electrolyte solution, applying a voltage to carry out a reaction, then filtering the electrolyte solution, and dialyzing the obtained filtrate to obtain nitrogen and sulfur co-doped carbon quantum dots.

[0006] In the second aspect of the present invention, a nitrogen and sulfur co-doped carbon quantum dot prepared by the preparation method described in the first aspect of the present invention is provided.

[0007] In the third aspect of the present invention, an application of the nitrogen and sulfur co-doped carbon quantum dot described in the second aspect of the present invention in the pickling process of copper-nickel alloys is provided.

[0008] The raw material of the present invention is peanut cake residue, which is widely available, low in price, non-toxic, good in biocompatibility, and rich in carbon atoms and heteroatoms. The prepared nitrogen and sulfur co-doped carbon quantum dots contain abundant N and S functional groups and are an excellent cathodic corrosion inhibitor, which has a good corrosion inhibition effect on the pickling of copper-nickel alloy at different temperatures. It adsorbs on the surface of copper-nickel alloy through chemical adsorption and physical adsorption, reduces the contact area between the pickling solution and the metal, and delays corrosion. Description of the Drawings

[0009] Figure 1 is the TEM image of the prepared N,S-CDs;

[0010] Figure 2 is the open circuit voltage E in the electrochemical test ocp curve graph;

[0011] Figure 3 is the potentiodynamic polarization curve of copper-nickel alloy in 0.5M H 2 SO 4 solution with different concentrations of N,S-CDs at different temperatures;

[0012] Figure 4 is the equivalent circuit diagram in the electrochemical test;

[0013] Figure 5 is the SEM image of Cu90Ni10 alloy after being immersed in 0.5M H 2 SO 4 solution with and without 100mg / L N,S-CDs for 20 hours;

[0014] Figure 6 is the AFM image of Cu90Ni10 alloy after being immersed in 0.5M H 2 SO 4 solution with and without 100mg / L N,S-CDs for 20 hours;

[0015] Figure 7 is the contour map of Cu90Ni10 alloy after being immersed in 0.5M H 2 SO 4 solution with and without 100mg / L N,S-CDs for 20 hours;

[0016] Figure 8 is the corrosion inhibition mechanism diagram of N,S-CDs. Detailed Embodiments

[0017] The following further describes the detailed embodiments of the present invention with reference to the drawings. It should be understood that the detailed embodiments described herein are only for the purpose of illustration and explanation of the present invention, and are not intended to limit the present invention.

[0018] In the description of this specification, the descriptions with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of this application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0019] The endpoints and any values disclosed herein for a range are not limited to the exact range or value, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and a single point value, and between single point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0020] In addition, the term "and / or" in the specification and claims is used to describe the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. The character " / " generally represents an "or" relationship between the associated objects before and after.

[0021] In the first aspect of the present invention, a preparation method of nitrogen and sulfur co-doped carbon quantum dots is provided, wherein the preparation method includes: dissolving pretreated peanut cake residue powder and thiosemicarbazide in a solvent to form an electrolyte, inserting an anode and a cathode into the electrolyte, applying a voltage for reaction, then filtering the electrolyte, and dialyzing the obtained filtrate to obtain nitrogen and sulfur co-doped carbon quantum dots.

[0022] The present invention prepares carbon quantum dots by means of electrification. Compared with traditional high-temperature reactions, it can control the size of the product and is beneficial to improving the purity of the product, thereby improving its corrosion inhibition performance.

[0023] Preferably, the mass ratio of the peanut cake residue powder to thiosemicarbazide is 1-2:1. The mass ratio of the peanut cake residue powder to thiosemicarbazide can be any value between any two of 1:1, 1.5:1, and 2:1.

[0024] Preferably, the solvent is absolute ethanol, and the mass-volume ratio of the total amount of peanut cake residue and thiosemicarbazide to the absolute ethanol is 5-10:200. The mass-volume ratio of the total amount of peanut cake residue and thiosemicarbazide to the absolute ethanol can be any value between any two values among 5:200, 6:200, 7:200, 8:200, 9:200, and 10:200.

[0025] Preferably, the step of applying a voltage for reaction includes: making the distance between the anode and the cathode be 0.5-2 cm, and then applying a DC voltage of 15-25 V for 12-20 h.

[0026] Preferably, the step of pretreatment includes: after crushing and sieving the peanut cake residue, treating it at 180-250 °C for 25-35 min to obtain the pretreated peanut cake residue powder.

[0027] There is no particular limitation on the mesh number requirements for sieving, such as it can be a 70-100 mesh sieve.

[0028] Preferably, the anode is a platinum sheet and the cathode is graphite.

[0029] Preferably, the step of filtration includes: first performing rough filtration with filter paper, and then performing secondary filtration with a 0.2-0.25 μm filter. The rough filtration is used to filter out large particles, and the secondary filtration is used to further remove unwanted impurities.

[0030] Preferably, the molecular cut-off of dialysis is 500-1500 Da, and the dialysis time is 20-25 h. The molecular cut-off of dialysis is preferably 1000 Da, and the dialysis time is preferably 25 h. During this period, the dialysis fluid is changed every 6 h, and the dialysis fluid generally uses ultrapure water.

[0031] Preferably, the method further includes: after the dialysis is completed, freeze-drying the retentate.

[0032] The second aspect of the present invention provides a nitrogen and sulfur co-doped carbon quantum dot prepared by the preparation method described in the first aspect of the present invention.

[0033] Preferably, the diameter of the nitrogen and sulfur co-doped carbon quantum dot does not exceed 10 nm.

[0034] The third aspect of the present invention provides an application of the nitrogen and sulfur co-doped carbon quantum dot described in the second aspect of the present invention in the pickling process of copper-nickel alloy.

[0035] Preferably, the concentration of the nitrogen and sulfur co-doped carbon quantum dot is 90-110 mg / L, and the pickling temperature is 298 K-318 K.

[0036] Preferably, the temperature of the pickling is 298K. The present invention discovers that when a certain concentration of nitrogen and sulfur co-doped carbon quantum dots is added to the pickling solution and combined with a specific pickling temperature, an unexpectedly good corrosion inhibition rate can be obtained, and the corrosion inhibition rate can be as high as over 98%.

[0037] Preferably, the solution used for pickling is a sulfuric acid solution.

[0038] Preferably, the sulfuric acid solution is a 0.5M sulfuric acid solution.

[0039] Preferably, based on the total amount of the copper-nickel alloy, the amount of copper is 85 - 95wt%, and the amount of nickel is 5 - 15wt%.

[0040] In the following examples and comparative examples, unless otherwise specified, reagents or instruments without indicating the manufacturer can be obtained as conventional products through commercial purchase. For those not specifying specific conditions in the examples, they are carried out according to conventional conditions or the conditions recommended by the manufacturer.

[0041] I. Preparation of nitrogen and sulfur co-doped carbon quantum dots

[0042] S1, Crush the peanut cake residue through an 80-mesh sieve and treat it at 200°C for 30 min to obtain the pretreated peanut cake residue powder.

[0043] S2, Weigh 3.0 g of the pretreated peanut cake residue powder and 3.0 g of thiosemicarbazide with an analytical balance, dissolve them in 200 mL of absolute ethanol, and perform ultrasonic treatment for 10 min to ensure the full dissolution of thiosemicarbazide, obtaining the electrolyte solution.

[0044] S3, Use a 1×1 cm 2 platinum sheet electrode as the anode and a graphite electrode (diameter 1 cm, length 5 cm) as the cathode. Place the above electrodes into the electrolyte solution with a distance of 1 cm between the two electrodes. Apply a 20V voltage between the two electrodes using a DC power supply for reaction for 18 h.

[0045] S4, After the reaction, filter out large particles with a funnel, then filter the liquid through a 0.22μm needle filter for a second time. Finally, transfer the remaining filtrate to a dialysis bag with a molecular cut-off of 1000 Da (pre-boiled in boiling water for 10 min) and perform dialysis for 12 h, changing the ultrapure water every 6 h. After dialysis, transfer all the liquid in the dialysis bag to the refrigerator, and finally freeze-dry the frozen liquid into a powder in a freeze dryer to obtain the nitrogen and sulfur co-doped carbon quantum dots, denoted as N,S-CDs.

[0046] II. Performance testing

[0047] The specific composition of Cu90Ni10 involved in the following tests is: Cu 90 ± 1 wt%, Ni 10 ± 1 wt%, Fe ≤ 1 wt%, Mn ≤ 1 wt%, named Cu90Ni10.

[0048] Blank solution: 0.5 M H2SO4 solution (concentration of N, S-CDs is 0)

[0049] Experimental solutions: A series of experimental solutions are formed by adding a certain amount of N, S-CDs to 0.5 M H2SO4 solution. The concentrations of N, S-CDs in this series of experimental solutions are: 10 mg / L, 25 mg / L, 50 mg / L, 100 mg / L.

[0050] TEM (FEI Tecnai G2 F20);

[0051] Infrared spectroscopy (Colet-iS50);

[0052] AFM (MFP-3D-BIO);

[0053] SEM (TM-1000);

[0054] Electrochemical tests: Use a CHI760E electrochemical workstation to study the anti-corrosion effect of N / S-CDs on the Cu90Ni10 alloy in 0.5 M H 2 SO 4 solution.

[0055] 1. Electrochemical test method

[0056] Adopt a three-electrode device, and retain 1 cm 2 working area of the Cu90Ni10 as the working electrode, saturated calomel as the reference electrode, and platinum sheet as the counter electrode. Before each test, the working electrode is polished with 400, 800, 1200, and 2000 mesh sandpapers. All electrodes are cleaned with absolute ethanol and then dried with cold air. The samples are immersed in the blank solution and each experimental solution at 298 K, 308 K, and 318 K respectively, and electrochemical data are tested, including the open-circuit potential curve. The open-circuit potential (E ocp ) is tested for 1800 s, and then an electrochemical impedance spectrum (EIS) is tested using a 10 -2 V sinusoidal potential signal, and the signal range is 10 5 Hz to 10 -2 Hz. Finally, the Tafel polarization curve is scanned at a speed of 10 -3 V / s, and the potential range is E ocp ±250 mV. To ensure good repeatability, each test is repeated three times in a constant temperature water bath under the same conditions.

[0057] 2. Surface Topography Analysis Method

[0058] Cu90Ni10 was polished with 400, 800, 1200, 2000, 3000, 5000, and 7000 - mesh sandpapers by water grinding until the surface was smooth and bright, and then cut into the required number of pieces. The cut Cu90Ni10 samples included two specifications, with sizes of 1×1×1 cm 3 and 0.5×0.5×0.5 cm 3 . Before use, the polished Cu90Ni10 samples were cleaned with absolute ethanol and dried with cold air.

[0059] The pretreated samples were immersed in the blank solution or the experimental solution at 298K, 308K, and 318K for a certain period of time. The 1×1×1 cm 3 Cu90Ni10 samples were used for atomic force microscopy (AFM) analysis. The 0.5×0.5×0.5 cm 3 Cu90Ni10 samples were used for scanning electron microscopy (SEM) analysis.

[0060] 3. Analysis of Test Results

[0061] (1) Analysis of N,S - CDs

[0062] The samples were dispersed by ultrasonic waves for 5 minutes and then distributed on the carbon film. Then, the size and shape of N,S - CDs were analyzed by transmission electron microscopy (TEM). The results are shown in Figure 1 (a) and (b).

[0063] It can be seen from the figure that the synthesized N,S - CDs are evenly dispersed on the carbon film and the diameter is less than 10 nanometers.

[0064] Figure 1 (c) is the infrared spectrum of the prepared N,S - CDs. It can be clearly seen the peaks of various functional groups in N,S - CDs. The broad peak at 3400 cm -1 is the peak of the stretching vibration of the O - H bond; the peak at 2363 cm -1 is the peak of the stretching vibration of C=O; the peak at 2064 cm -1 is the peak generated by the double - bond combination of O=C and S=C; the peak at 1610 cm -1 is the peak of C - N or C - C stretching vibration; the peak at 1350 cm -1 is the peak of - COO; the peak at 1290 cm -1 is the peak of the in - plane bending vibration of O - H; and the peak at 1030 cm -1 may be caused by C - SO 3 ; the peak at 1000 cm -1 or less is the peak of the aromatic or aliphatic C - H bending vibration.

[0065] (2) Analysis of the open-circuit voltage E ocp Analysis

[0066] The open-circuit voltage E of the blank solution and each experimental solution ocp The curve graph is as Figure 2 shown Figure 2 (a), Figure 2 (b) and Figure 2 (c) are the E 2 SO 4 curves of the 0.5M H ocp solution containing different concentrations of N,S-CD at 298K, 308K and 318K respectively

[0067] It can be seen from the figure that at the same temperature, as the concentration of N,S-CDs increases, the E ocp curve obviously shifts towards the negative direction. This may be due to the formation of N,S-CDs on the surface of the adsorption film of the alloy sample, which changes the dissolved oxygen content in the solution. Each E ocp curve tends to be stable at 1800s, indicating that the adsorption-desorption on the surface of the copper-nickel alloy has reached a dynamic equilibrium state

[0068] (3) Analysis of the Tafel polarization curve

[0069] Figure 3 are the potentiodynamic polarization curves (from the Tafel polarization curve) of copper-nickel alloy in 0.5M H 2 SO 4 solution with different concentrations of N,S-CDs at different temperatures. Among them, Figure 3 (a) is the potentiodynamic polarization curve of Cu90Ni10 alloy in 0.5M H 2 SO 4 solution (without N,S-CDs) at different temperatures, Figure 3 (b) is the potentiodynamic polarization curve of Cu90Ni10 alloy in 0.5M H solution containing 100mg / L N,S-CDs at different temperatures, 2 SO 4 solution, Figure 3 (c), (d) and (e) are the potentiodynamic polarization curves of Cu90Ni10 alloy in 0.5M H 2 SO 4 solution containing different concentrations of N,S-CDs at 298K, 308K and 318K respectively. In the figure, the anodic polarization curve represents the anodic oxidation of Cu90Ni10, while the cathodic curve represents the hydrogen evolution reaction by cathodic reduction of water

[0070] As can be seen from the figure, N,S-CDs have an inhibitory effect on both the cathodic and anodic branches. Compared with the blank solution, the corrosion current density of all cathodic and anodic branches decreases. At the same time, the corrosion current density also decreases significantly, indicating that the addition of N,S-CDs may greatly reduce the corrosion rate. In addition, the cathodic branch curves of all potentiodynamic polarization curves remain roughly unchanged, while a plateau appears in the anodic branch. As the concentration of carbon quantum dots increases, the plateau continues to lengthen. This may be due to the adhesion of N,S-CDs on the surface of the copper-nickel alloy electrode and the formation of a substantial protective layer, resulting in the passivation of the anodic branch.

[0071] The potentiodynamic polarization curves were fitted using the classical extrapolation method to obtain the corrosion current density (i corr ), corrosion potential (E corr ), anodic and cathodic slopes (β a , β c ), and the corrosion rate (R corr ) and inhibition efficiency (η) were further calculated using the following formulas:

[0072]

[0073] where i corr , i corr,0 represent the corrosion current densities corresponding to the experimental solution and the blank solution, respectively, r is the relative molecular weight of the copper-nickel alloy, and d is the density of the copper-nickel alloy.

[0074] The results are shown in Table 1.

[0075] Table 1

[0076]

[0077] As can be seen from Table 1, under the condition of the same concentration of N,S-CDs, as the temperature increases, i corr and R corr increase, so the increase in temperature will accelerate the corrosion of the copper-nickel alloy. Even at a temperature of 318 K, when N,S-CDs with a concentration of 100 mg / L are added, the inhibition efficiency can still reach 92.60%. It can also be seen from Table 1 that the E corr of the experimental solution with a concentration of 100 mg / L of N,S-CDs deviates by more than 85 mV compared with the blank solution, indicating that N,S-CDs are cathodic inhibitors.

[0078] (4) Analysis of EIS test data

[0079] The EIS data was fitted using the equivalent circuit diagram shown in Figure 4 . Figure 4 (a) is the equivalent circuit diagram of the model without N,S-CDs, Figure 4(b) is the equivalent circuit diagram of the model containing N, S-CDs, and the film resistance (R f ), charge transfer resistance (R ct ), and other parameters (such as impedance W, total impedance R p , etc.) are obtained. C dl is the double-layer capacitor related to the constant phase angle element and is calculated by the following formula:

[0080]

[0081] C dl = Y 0 ω n-1 = Y 0 (2πf Zim-Max ) n-1

[0082] where f Zim-Max represents the frequency corresponding to the maximum imaginary part of the impedance, j represents the imaginary unit, ω represents the angular frequency, and jω is 2πf Zim-Max .

[0083] Then, the corrosion inhibition rate η is further calculated using the following formula:

[0084] R p = R f + R ct

[0085]

[0086] where R p and R p，0 respectively represent the total impedance of the copper-nickel electrode in the experimental solution and the blank solution.

[0087] The fitting results are shown in Table 2.

[0088] Table 2

[0089]

[0090] It can be seen from Table 2 that when the concentration of N, S-CDs is 100 mg / L at 298 K, η is 98.77%, and η still remains at about 97% at 318 K, indicating that N, S-CDs is an excellent corrosion inhibitor and can maintain good corrosion resistance within a certain temperature range.

[0091] The corrosion inhibition efficiency is evaluated from two different dimensions in Table 1 and Table 2, and both dimensions prove that the nitrogen and sulfur-doped carbon quantum dots prepared by the present invention have good corrosion inhibition performance for copper-nickel alloys.

[0092] (5) SEM images of the Cu90Ni10 alloy after immersion test

[0093] After the Cu90Ni10 alloy was immersed in 0.5 M H 2 SO 4 solution without and with 100 mg / L N,S-CDs for 20 hours, its SEM images are as shown in Figure 5 the following. Figure 5 (a), (b), and (c) are SEM images of the Cu90Ni10 alloy immersed in 0.5 M H 2 SO 4 solution without N,S-CDs for 20 hours at 298 K, 308 K, and 318 K respectively. It can be seen that the surface of the Cu90Ni10 alloy immersed in 0.5 M H 2 SO 4 solution without N,S-CDs is severely corroded, with obvious corrosion marks and pits. Moreover, as the temperature increases, the corrosion marks become more obvious and dense. Figure 5 (d), (e), and (f) are SEM images of the Cu90Ni10 alloy immersed in 0.5 M H 2 SO 4 solution with 100 mg / L N,S-CDs for 20 hours at 298 K, 308 K, and 318 K respectively. As can be seen from the figure, Figure 5 the particulate matter in (e) indicates that individual carbon quantum dots have aggregated, Figure 5 and the particulate matter in (f) indicates that a large number of carbon quantum dots have aggregated. The surface of the Cu90Ni10 alloy immersed in 0.5 M H 2 SO 4 solution with 100 mg / L N,S-CDs has no obvious corrosion marks. Especially at 298 K, the nitrogen and sulfur doped carbon quantum dots do not aggregate at all, and the scratches of the sandpaper are still clearly visible. This shows that the surface of the Cu90Ni10 alloy is hardly corroded. However, corrosion marks begin to appear as the temperature rises, but it is still much smoother compared to the Cu90Ni10 alloy immersed in 0.5 M H 2 SO 4 solution without N,S-CDs. This indicates that N,S-CDs can effectively reduce the corrosion of the Cu90Ni10 alloy in sulfuric acid and help prevent the aggregation of carbon quantum dots at specific temperatures and concentrations.

[0094] (6) AFM images of the Cu90Ni10 alloy after immersion test

[0095] After the Cu90Ni10 alloy was immersed in 0.5 M H 2 SO 4 solution without and with 100 mg / L N,S-CDs for 20 hours, its AFM images are as shown in Figure 6 the following, and the contour lines of this figure are as shown in Figure 7 the following.

[0096] Figure 6 (a), (b), and (c) are AFM images after soaking in 0.5 M H 2 SO 4 solution without N, S-CDs for 20 hours at 298 K, 308 K, and 318 K, respectively. Figure 6 (d), (e), and (f) are AFM images after soaking in 0.5 M H 2 SO 4 solution containing 100 mg / L N, S-CDs for 20 hours at 298 K, 308 K, and 318 K, respectively. Figure 7 (a), (b), and (c) are contour maps after soaking the Cu90Ni10 alloy in 0.5 M H 2 SO 4 solution with and without 100 mg / L N, S-CDs for 20 hours at 298 K, 308 K, and 318 K, respectively.

[0097] As can be seen from the figure, the surface of the Cu90Ni10 alloy soaked in 0.5 M H 2 SO 4 solution containing 100 mg / L N, S-CDs is relatively flat and not severely corroded. However, with the increase in temperature, the average roughness increases from 39.023 nm to 76.855 nm, indicating an increase in the degree of corrosion. At the same temperature, when N, S-CDs are added, the roughness of the Cu90Ni10 alloy decreases by 23.592 nm (298 K), 39.784 nm (308 K), and 38.594 nm (318 K) compared with that without N, S-CDs. This shows that N, S-CDs can slow down the corrosion of the Cu90Ni10 alloy in 0.5 M H 2 SO 4 solution.

[0098] The corrosion inhibition mechanism of the N, S-CDs prepared in this invention is as Figure 8 shown. There are both physical adsorption and chemical adsorption between the N, S-CDs molecules and the surface of the copper-nickel alloy. The N, S-CDs molecules contain N, S, and other heteroatoms with electron-withdrawing ability, and the copper atoms have empty orbitals that can provide electrons. Therefore, the N, S-CDs molecules can combine with copper ions and cuprous ions to form stable coordination bonds, that is:

[0099] n N, S CDs + Cu + → [Cu n(N, S CDs)] + ads

[0100] n N, S CDs + Cu 2+→[Cu n(N, S CDs)] 2+

[0101] It is precisely through the dual actions of physical and chemical adsorption that N, S-CDs can form a protective layer on the surface of the copper-nickel alloy to further reduce the contact area between the substrate and the corrosive solution, thereby delaying corrosion.

[0102] The preferred embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including the combination of each specific technical feature in any suitable manner. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods. However, these simple modifications and combinations should also be regarded as the content disclosed by the present invention and all fall within the protection scope of the present invention.

Claims

1. A method for preparing nitrogen-sulfur doped carbon quantum dots, characterized in that: The preparation method comprises: dissolving pretreated peanut cake residue powder and thiosemicarbazide in a solvent to form an electrolyte, inserting an anode and a cathode into the electrolyte, applying voltage to react, filtering the electrolyte, and dialyzing the obtained filtrate to obtain nitrogen-sulfur doped carbon quantum dots.

2. The preparation method according to claim 1, wherein The mass ratio of the peanut cake residue powder to thiosemicarbazide is 1-2:

1.

3. The preparation method according to claim 1 or 2, wherein The solvent is anhydrous ethanol, and the mass volume ratio of the total amount of the peanut cake residue and thiosemicarbazide to the anhydrous ethanol is 5-10:

200.

4. The preparation method according to claim 3, wherein The step of applying voltage to react comprises: making the distance between the anode and the cathode 0.5-2 cm, and then applying a DC voltage of 15-25 V for 15-20 h.

5. The preparation method according to claim 4, wherein The pretreatment step includes: crushing and sieving the peanut cake residue, and then treating it at 180-250° C. for 25-35 minutes to obtain the pretreated peanut cake residue powder.

6. The preparation method according to claim 4 or 5, wherein: The filtering step comprises: firstly coarse filtering with filter paper, and then secondary filtering with a 0.2-0.25 μm filter; And / or, the molecular cutoff of the dialysis is 500-1500Da, and the dialysis time is 20-25h.

7. Nitrogen-sulfur doped carbon quantum dots prepared according to the preparation method according to any one of claims 1 to 6.

8. The nitrogen-sulfur doped carbon quantum dots according to claim 7, wherein: The diameter of the nitrogen-sulfur doped carbon quantum dots does not exceed 10 nm.

9. Use of the nitrogen-sulfur doped carbon quantum dots according to claim 7 or 8 in a copper-nickel alloy pickling process.

10. The use according to claim 9, based on the total amount of pickling solution, the concentration of the nitrogen-sulfur doped carbon quantum dots is 90-110 mg / L, and the pickling temperature is 298K-318K, preferably 298K.

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