Anode porous copper-based catalyst, preparation method of anode porous copper-based catalyst and method for producing lithium carbonate under assistance of electro-catalysis formate oxidation

Abstract

The invention relates to an anode porous copper-based catalyst, a preparation method of the anode porous copper-based catalyst and a method for producing lithium carbonate under the assistance of electro-catalysis formate oxidation. The preparation method of the anode porous copper-based catalyst comprises the steps of synthesis, vulcanization and controllable electro-oxidation of supported copper hydroxide. And then the formate is subjected to electrocatalytic oxidation by using an anode to generate carbonate ions in situ, and high-quality lithium carbonate is produced by coupling lithium ions in the electrolyte. The novel electrocatalytic formate oxidation assisted high-quality lithium carbonate output method is simple in process, high-quality lithium carbonate output can be achieved without consumption of a large amount of chemicals and purified water, and compared with a traditional sodium carbonate solution assisted high-quality lithium carbonate output method, economic and ecological benefits are effectively improved; the goals of green development and circular economy are met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrocatalytic oxidation, in particular to an anode porous copper-based catalyst, a preparation method thereof and a method for producing lithium carbonate assisted by electrocatalytic oxidation of formate. BACKGROUND

[0002] Lithium-ion battery (LIB) has the advantages of high energy density, long cycle life and green environmental protection, and is widely used as a new generation of energy storage device in new energy vehicles, mobile phones and other power sources. The global transition to a low-carbon energy system has stimulated the annual growth rate of LIB demand to 20%, and it is expected to grow by 10 times by 2030. As the main precursor of LIB cathode (such as LiCoO2, LiFePO4), high-purity Li2CO3 (≥99.5%) is essential, but its production faces double challenges: limited lithium resources and high-pollution and high-cost production processes.

[0003] The traditional high-purity Li2CO3 production method, such as the sodium carbonate solution assisted Li2CO3 production strategy, requires a large amount of fresh water and chemicals for each ton of Li2CO3 produced, and generates a large amount of chemical waste, resulting in a carbon footprint that is 5-8 times higher than that of lithium-ion battery production itself. At the same time, the temperature needs to be maintained at 80 ℃ or above throughout the process to ensure the precipitation of Li2CO3, which requires a large amount of energy, increasing production costs. At the same time, the large amount of chemicals and fresh water input in the production process of high-quality Li2CO3 weakens the environmental characteristics of the LIB life cycle. Therefore, developing a new type of green and economic high-quality Li2CO3 production strategy is crucial to improving the economic and ecological benefits of the LIB life cycle. SUMMARY

[0004] In view of the deficiencies in the prior art, the present application provides a new type of anode porous copper-based catalyst, and uses it to produce high-quality lithium carbonate assisted by electrocatalytic oxidation of formate, to solve the cost and environmental technical problems existing in the prior art.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solutions: The first purpose of the present application provides a preparation method of an anode porous copper-based catalyst with high formate electro-oxidation performance, comprising the following steps: 1) Clean the foam copper with ethanol, hydrochloric acid and deionized water in sequence, and dry to obtain a clean foam copper substrate; 2) Immersing the clean foam copper substrate in a clear solution composed of potassium hydroxide and ammonium persulfate, taking out the foam copper, washing and drying to obtain a copper hydroxide precursor; 3) Put the supported copper hydroxide precursor into the sulfur salt solution for sulfurization, take out, clean, and dry; then, under a nitrogen atmosphere, prepare the supported copper sulfide pre-catalyst by a two-step calcination method; 4) Put the supported copper sulfide pre-catalyst into the basic electrolyte containing formate salt for electro-oxidation treatment, take out, clean, and dry to obtain the anode porous copper-based catalyst.

[0006] Further, the thickness of the copper foam is in the range of 0.1-50 mm, and the pore size is between 5-130 ppi.

[0007] Further, the sulfur salt is sodium sulfide or potassium sulfide.

[0008] Further, the basic electrolyte containing formate salt is composed of sodium hydroxide or potassium hydroxide, sodium formate or potassium formate, and deionized water.

[0009] Further, the current density of the electro-oxidation treatment is 50-300 mA cm −2 , and the electro-oxidation time is 1-24 h.

[0010] Further, the two-step calcination method is to increase the temperature to 150 °C at a heating rate of 2 °C min −1 for 1 h, then further increase the temperature to 200 °C and maintain for 2 h, and then cool to room temperature.

[0011] The present application further provides an anode porous copper-based catalyst with high formate salt electro-oxidation performance prepared by the preparation method as described above.

[0012] The second object of the present application provides a method for producing high-quality lithium carbonate assisted by electro-catalytic oxidation of formate salt, which uses the anode porous copper-based catalyst as described above to catalyze the in-situ generation of carbonate ions from the oxidation of formate, and couples the lithium ions in the electrolyte to produce high-quality lithium carbonate, while the cathode catalytic electrode produces cathode products.

[0013] Further, the electrolyte is a basic lithium-containing solution derived from one of a lithium ore dissolution solution, a salt lake, a recycled solution from retired lithium batteries, and a crude lithium carbonate refining solution.

[0014] Further, the cathode catalytic electrode is a porous electrode with high reduction reaction electro-catalytic performance, wherein the reduction reaction includes one of hydrogen evolution reaction, carbon dioxide reduction reaction, carbon monoxide reduction reaction, nitrate reduction reaction, nitrogen reduction reaction, oxygen reduction reaction, high-valence noble metal and heavy metal reduction reaction; and the cathode product is one of hydrogen, single-carbon or multi-carbon product, urea, ammonia, hydrogen peroxide, and noble metal.

[0015] The beneficial effects of this invention are: the novel electrocatalytic formate oxidation-assisted method for producing high-quality lithium carbonate is simple and can produce high-quality lithium carbonate products with a purity of up to 99.56% without the need for continuous input of large amounts of chemicals and pure water; compared with the traditional sodium carbonate solution-assisted method for producing high-quality lithium carbonate, it effectively improves economic and ecological benefits and is in line with the goals of green development and circular economy. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 The porous copper-based catalyst (CuO@SO) of the present invention is an anode. x A simplified process flow diagram of the preparation method of -CF; Figure 2 The porous copper-based catalyst and precursor (CuS) of the present invention are x XRD pattern of -CF); Figure 3 This is a SEM image of the porous copper-based catalyst of the present invention. Figure 4 This is a TEM image of the porous copper-based catalyst of the present invention. Figure 5 This is a high-resolution Cu 2p XPS image of the porous copper-based catalyst and precursor of the present invention. Figure 6 The Raman spectrum of the porous copper-based catalyst and precursor of the present invention is shown below. Figure 7 K-edge XANES spectra of the porous copper-based anodic catalyst, precursor, copper foil, cuprous oxide and copper oxide of the present invention. Figure 8 The K-edge EXAFS spectra of the anodic porous copper-based catalyst, precursor, copper foil, cuprous oxide, and copper oxide of the present invention are shown. Figure 9 The LSV curves of the porous copper-based catalyst and precursor prepared in Example 1 of this invention in an alkaline environment for oxygen evolution and formate oxidation reactions are shown. Figure 10 The LSV curve of the system for the complete hydrolysis and high-quality lithium carbonate production of the anode porous copper-based catalyst coupled with the cathode NiMoN catalyst prepared in Example 1 of this invention in an alkaline environment is shown. Figure 11 This is a galvanostatic curve of the porous copper-based anode catalyst coupled with the NiMoN cathode catalyst prepared in Example 1 of the present invention in an alkaline environment. Figure 12 The XRD pattern of the white solid produced by the electrocatalytic formate oxidation-assisted high-quality lithium carbonate production system of the present invention (the inner part is an optical photograph of the white solid produced). Figure 13 This is a comparison chart showing the purity of lithium carbonate products from the novel electrocatalytic formate oxidation-assisted high-quality lithium carbonate production method of the present invention, compared with the purity of lithium carbonate products from the traditional saturated sodium carbonate solution-assisted lithium carbonate production method. Detailed Implementation

[0018] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0020] Example 1: As Figure 1 The flowchart shows the preparation process of the porous copper-based catalyst, which involves sequential sulfidation and electro-oxidation reconstruction treatments. The specific preparation process is as follows: 1) The foamed copper was successively cleaned with ethanol, hydrochloric acid and deionized water and dried to obtain the foamed copper substrate; 2) Dissolve 4.125 g KOH and 0.728 g (NH4)2S2O8 in 50 mL of deionized water to form a clear solution; then immerse the copper foam substrate in the clear solution for 30 min. Subsequently, remove the copper foam, wash it with deionized water and ethanol, and dry it.

[0021] 3) Immerse the treated copper foam in 50 mL of 5 mM Na₂S solution for 60 min, then wash and dry. Subsequently, place the copper foam in a tube furnace under a nitrogen atmosphere and heat at 2°C for [time missing]. −1 The heating rate was increased to 150°C and held for 1 hour. The temperature was then further increased to 200°C and held for 2 hours, followed by cooling to room temperature to obtain the pre-catalyst CuS. x -CF; 4) Place CuS x - CF was cut into 1 cm × 1 cm pieces, then immersed in a solution containing 1 M KOH and 1 M HCOOK, and then heated at 100 mA cm⁻¹. −2The catalyst was subjected to constant current treatment at a current density of 50,000 s. Afterwards, the catalyst was washed and dried to obtain the porous copper-based anode catalyst, denoted as CuO@SO₄. x -CF.; Figure 2 The images shown are XRD patterns of the porous copper-based catalyst and precursor prepared in Example 1 of this application, CuS. x The XRD diffraction pattern of -CF revealed characteristic peaks of Cu7S4 (JCPDS No. 23-0958), confirming the success of S doping. After in-situ reconstruction by electro-oxidation, Cu was transformed into a high-valence state, in which the Cu7S4 phase decreased and CuO appeared (JCPDS No. 48-1548).

[0022] Figure 3 , 4 The images shown are SEM and TEM images of the porous copper-based catalyst prepared in Example 1 of this application. The SEM image shows that the porous copper-based catalyst exhibits a nanowire structure with grown sheets. The high-resolution TEM image shows lattice stripes spaced at 0.23 nm, corresponding to the (1 1 1) crystal plane of CuO.

[0023] High-resolution Cu 2p XPS spectra ( Figure 5 At 933.7 eV (Cu 2p) 3 / 2 ) and 953.6 eV (Cu 2p 1 / 2 The peak value is shown at (). This indicates that the increase in satellite peak area after electro-oxidation confirms the formation of high-valence Cu-O species.

[0024] Figure 6 The Raman spectrum of the porous copper-based catalyst and precursor prepared in Example 1 of this application is shown at 295 cm⁻¹. −1 342cm −1 and 629cm −1 The characteristic peak observed at 982 cm⁻¹ corresponds to CuO species produced after electro-oxidation treatment. Notably, at 982 cm⁻¹... −1 A new peak appeared, which is attributed to sulfate (SO4). 2− The SO stretching vibration of SO confirmed the existence of SO. x Speciation. Figure 7 The fine structure X-ray absorption spectra of Cu K-edge show that the porous copper-based catalyst shifts to the right compared to the precursor, indicating that the valence state of Cu increases significantly after electro-oxidation treatment. Figure 8The FT-EXAFS spectra of the porous copper-based catalyst show two peaks at 1.5 Å and 2.2 Å, corresponding to Cu-O and Cu-Cu bonds. In contrast, the FT-EXAFS spectra of the precursor show characteristic peaks of Cu-S and Cu-Cu bonds, indicating the formation of CuO species after electro-oxidation treatment.

[0025] The above test results all confirm that the final product obtained is CuO@SO₄. x -CF anode porous copper-based catalyst.

[0026] Example 2: CuO@SO x - CF catalytic performance test A three-electrode system was used, with a porous copper-based catalyst or precursor as the working electrode, an Hg / HgO electrode as the reference electrode, and a carbon rod as the counter electrode. An electrochemical workstation (Gamry) was used, and the tests were conducted in a 1M KOH solution containing 1M HCOOK.

[0027] from Figure 9 Medium CuO@SO x The linear sweep voltammetry curves for -CF indicate that 100 / 500 mA cm⁻¹ can be achieved when a potential of only 1.421 / 1.464 V is applied. −2 The oxidation current density of the formate oxidation reaction (FOR) is superior to that of CuS before electro-oxidation treatment. x -CF catalyst.

[0028] Example 3: Production of high-quality lithium carbonate from alkaline lithium-containing solutions CuO@SO prepared in Example 1 x -CF was used as the anode electrode, and NiMoN was used as the cathode electrode, with 1M alkaline lithium-containing raffinate (ionic composition: Na) as the cathode electrode. + Li + OH − HCOO − Using 1000 ions as the electrolyte, a novel electrocatalytic formate oxidation-assisted high-quality lithium carbonate production system was assembled.

[0029] from Figure 10 As can be seen from the LSV curve, a voltage of only 1.504V is required to achieve a 100mA cm-wave amplitude. −2 High-quality lithium carbonate exhibits excellent current density performance.

[0030] Figure 11 It can be seen that the electrocatalytic formate oxidation-assisted high-quality lithium carbonate production system can stably produce lithium carbonate for more than 100 hours.

[0031] Figure 12XRD patterns and optical images of the white solid produced during the operation of the electrocatalytic formate oxidation-assisted high-quality lithium carbonate production system confirm that the produced white solid product is lithium carbonate.

[0032] Figure 13 The graph shows a comparison of the purity of lithium carbonate produced by the electrocatalytic formate oxidation-assisted high-quality lithium carbonate production method (EFAP) and the conventional saturated sodium carbonate solution-assisted lithium carbonate production method (SCSP). It can be seen that the purity of lithium carbonate produced by this application before additional washing and impurity removal steps is 99.56%, which is significantly higher than the 97.61% purity of lithium carbonate produced by the conventional production method.

[0033] In summary, in a FOR-assisted high-quality Li₂CO₃ production system, the electric fields formed at the cathode and anode will induce concentration gradients of anions and cations in the anode and cathode regions, respectively. At the anode surface, HCOO… − In-situ oxidation to produce CO3 2− Then with Li + The Li₂CO₃ product is formed through this process. Due to the presence of an electric field and the occurrence of FOR (Formula for Orthogonalization), the impurity concentration in the Li₂CO₃ nucleation and growth regions is effectively reduced, thereby minimizing impurity doping and producing a high-quality Li₂CO₃ product (purity: 99.56%). This strategy makes the production of high-quality Li₂CO₃ more environmentally friendly and economically feasible, showing great potential in Li₂CO₃ refining and lithium resource recovery.

[0034] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing a porous copper-based anolyte catalyst with high formate electro-oxidation performance, characterized in that, Includes the following steps: 1) The foamed copper was washed sequentially with ethanol, hydrochloric acid and deionized water, and dried to obtain a clean foamed copper substrate. 2) Immerse the clean copper foam substrate in a clear solution composed of potassium hydroxide and ammonium persulfate, remove the copper foam, wash and dry it to obtain the supported copper hydroxide precursor. 3) The supported copper hydroxide precursor was sulfided in a sulfur salt solution, removed, cleaned, and dried; then, under a nitrogen atmosphere, a two-step calcination method was used to prepare the supported copper sulfide precatalyst. 4) The supported copper sulfide precatalyst is placed in an alkaline electrolyte containing formate for electro-oxidation treatment, then removed, cleaned, and dried to obtain the porous copper-based anode catalyst.

2. The method for preparing the porous copper-based anolyte catalyst with high formate electro-oxidation performance according to claim 1, characterized in that, The thickness of the copper foam is in the range of 0.1-50 mm, and the pore size is between 5-130 ppi.

3. The method for preparing the porous copper-based anolyte catalyst with high formate electro-oxidation performance according to claim 1, characterized in that, The sulfur salt is sodium sulfide or potassium sulfide.

4. The method for preparing the porous copper-based anolyte catalyst with high formate electro-oxidation performance according to claim 1, characterized in that, The alkaline electrolyte containing formate is composed of sodium hydroxide or potassium hydroxide, sodium formate or potassium formate, and deionized water.

5. The method for preparing the porous copper-based anolyte catalyst with high formate electro-oxidation performance according to claim 1, characterized in that, The current density for electro-oxidation treatment is 50~300 mA cm⁻¹ −2 The electro-oxidation time is 1~24 h.

6. The method for preparing the porous copper-based anolyte catalyst with high formate electro-oxidation performance according to claim 1, characterized in that, The two-step calcination method is performed at 2 °C min. −1 The heating rate was increased to 150°C and held for 1 hour, then the temperature was further increased to 200°C and held for 2 hours, and then cooled to room temperature.

7. A porous copper-based anolyte catalyst with high formate electro-oxidation performance prepared by the method according to any one of claims 1-6.

8. A method for producing high-quality lithium carbonate assisted by electrocatalytic formate oxidation, characterized in that, The porous copper-based catalyst of the anode as described in claim 7 is used to catalyze the in-situ oxidation of formate to generate carbonate ions, coupled with lithium ions in the electrolyte to produce high-quality lithium carbonate, while the cathode catalytic electrode produces cathode products.

9. The method for producing high-quality lithium carbonate assisted by electrocatalytic formate oxidation according to claim 8, characterized in that, The electrolyte is an alkaline lithium-containing solution, derived from one of the following: lithium ore dissolution solution, salt lake, recycled lithium battery solution, or crude lithium carbonate refining solution.

10. The method for producing high-quality lithium carbonate assisted by electrocatalytic formate oxidation according to claim 8, characterized in that, The cathode catalytic electrode is a porous electrode with high electrocatalytic performance for reduction reactions, wherein the reduction reaction includes one of the following: hydrogen evolution reaction, carbon dioxide reduction reaction, carbon monoxide reduction reaction, nitrate reduction reaction, nitrogen reduction reaction, oxygen reduction reaction, and reduction reaction of high-valence precious metals and heavy metals; the cathode product is one of the following: hydrogen, single-carbon or multi-carbon products, urea, ammonia, hydrogen peroxide, and precious metals.

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