A method for inhibiting hydrogen evolution during high purity iron electrodeposition

Abstract

The present application relates to a kind of methods for inhibiting hydrogen evolution in high-purity iron electrodeposition process, the method comprises the following steps: mixing ferrous salt solution, acid solution, stabilizer and solvation additive, obtain acidic electrolyte;Cathode and anode are placed in acidic electrolyte, electrodeposition is carried out, and high-purity iron is obtained;The solvation additive is the compound that occurs hydrogen bond interaction, coordination, dipole interaction or solvation with water molecules, hydrated proton or ferrous ion.The present application adjusts the local solvation environment of water molecules, hydrated proton and ferrous ion in acidic ferrous salt electrolyte by introducing solvation additive, thereby inhibiting cathode hydrogen evolution side reaction, improving cathode current efficiency, improving the compactness of deposition layer and the purity of high-purity iron product.The present application has the advantages of simple process, weak hydrogen evolution side reaction, high current efficiency, good deposition layer quality and wide application range, and is suitable for electrochemical preparation of high-purity iron and iron-based functional materials.

Description

Technical Field

[0001] This invention relates to the fields of hydrometallurgy, electrochemical metallurgy, and high-purity metal preparation technology, and particularly to a method for suppressing hydrogen evolution during the electrodeposition of high-purity iron. Background Technology

[0002] High-purity iron is a crucial raw material for high-performance soft magnetic materials, precision electromagnetic devices, iron-based functional alloys, electronic materials, and advanced functional materials. With the development of high-end manufacturing, microelectronics, new energy equipment, and aerospace, higher demands are being placed on the purity, microstructure uniformity, deposition quality, and service performance of iron-based materials.

[0003] Currently, the main methods for preparing high-purity iron include pyrometallurgy, electrochemical metallurgy, and combined methods involving multiple processes. Among these, acidic aqueous solution electrodeposition is considered one of the important technical routes for preparing high-purity iron due to its advantages such as relatively simple process flow, mild operating conditions, low equipment requirements, and ease of continuous production.

[0004] However, in acidic ferrous salt electrolytes, especially acidic ferrous sulfate systems, ferrous ion reduction deposition and hydrogen evolution side reactions usually occur simultaneously. The hydrogen evolution side reaction consumes some of the cathode current, reducing cathode current efficiency. Simultaneously, the covering, growth, and desorption of hydrogen bubbles on the cathode surface disrupt local mass transfer and current distribution, easily leading to problems such as porosity, looseness, dendrites, or surface roughness in the deposited layer. Furthermore, the local pH increase caused by hydrogen evolution may promote the formation of hydroxides or oxygen- and sulfur-containing impurities, thus affecting the purity and deposition quality of the electrodeposited iron.

[0005] In existing technologies, to suppress hydrogen evolution side reactions during ferroelectric deposition, methods such as adjusting electrolyte pH, reducing current density, increasing temperature, optimizing mass transfer conditions, or adding surfactants are commonly used. These methods can improve the electrodeposition process to some extent, but simply optimizing process parameters has limited ability to suppress hydrogen evolution side reactions. While interfacial surfactants or organic additives can improve the cathode interface state and deposition morphology, their effects are mainly concentrated on the adsorption process on the cathode surface, making them susceptible to local current distribution, bubble coverage, and additive consumption. Some additives may also introduce organic residues or non-metallic impurities.

[0006] Therefore, how to adjust the competitive relationship between the hydrogen evolution side reaction and the iron deposition process at the electrolyte structure level without significantly increasing the risk of impurity residue, thereby improving cathode current efficiency and obtaining a dense, high-purity iron deposition layer, is a technical problem that urgently needs to be solved in the preparation of high-purity iron electrodeposition in acidic ferrous salt electrolytes. Summary of the Invention

[0007] To address the aforementioned technical problems, the present invention aims to provide a method for suppressing hydrogen evolution during the electrodeposition of high-purity iron. This method involves introducing a solubilizing additive into an acidic ferrous salt electrolyte, preferably into an acidic sulfate ferrous electrolyte, to adjust the local solubilization environment of water molecules, hydrated protons, and ferrous ions in the electrolyte. This alters the competitive relationship between the cathode hydrogen evolution side reaction and the ferrous ion reduction deposition, thereby improving cathode current efficiency, enhancing the density of the deposited layer, and improving the quality of high-purity electrodeposited iron products.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for suppressing hydrogen evolution during high-purity iron electrodeposition, the method comprising the following steps:

[0010] A ferrous salt solution, an acid solution, a stabilizer, and a solubilizing additive are mixed to obtain an acidic electrolyte.

[0011] High-purity iron is obtained by placing the cathode and anode in an acidic electrolyte and performing electrodeposition.

[0012] The solvating additive is a compound that interacts with water molecules, hydrated protons, or ferrous ions through hydrogen bonding, coordination, dipole interaction, or solvation.

[0013] This invention alters the bulk solvation structure of acidic ferrous salt electrolytes by introducing solubilizing additives, preferably to acidic sulfate ferrous electrolytes. Unlike conventional interfacial additives that primarily rely on cathode surface adsorption, the solubilizing additives of this invention mainly reduce the competitive effect of hydrogen evolution side reactions and promote the stable iron deposition process by adjusting the bulk electrolyte structure and cathode reaction environment.

[0014] In this invention, the solvation additive is not limited to a single compound, but includes compounds that can change the solvation structure of water molecules, hydrated protons and / or ferrous ions in acidic ferrous salt electrolytes through hydrogen bonding, coordination, dipole interaction or solvation competition. Preferably, it is a compound that can change the solvation structure of water molecules, hydrated protons and / or ferrous ions in acidic sulfate ferrous systems.

[0015] The method provided by this invention has the advantages of simple process, weak hydrogen evolution side reaction, high current efficiency, good deposition layer quality and wide applicability, and is suitable for the electrochemical preparation of high-purity iron and iron-based functional materials.

[0016] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0017] In some embodiments, the solvating additive contains any one or at least two polar groups selected from S=O, C=O, COC, -OH, -NH-, -CN, -SO2-, or -CONH-. Typical but non-limiting combinations include combinations of S=O and C=O, combinations of COC, -OH, and -NH-, combinations of -NH- and -CN, combinations of -SO2- and -CONH-, combinations of S=O, C=O, and COC, combinations of -NH-, -CN, -SO2-, and -CONH-, or combinations of S=O, C=O, COC, -OH, and -NH-.

[0018] In this invention, the solvation additive molecules contain polar groups such as S=O, C=O, COC, -OH, -NH-, -CN, -SO2-, or -CONH-. These polar groups can regulate the local solvation environment in the acidic ferrous salt electrolyte through different mechanisms. Specifically, oxygen- or nitrogen-containing polar groups can form hydrogen bonds with water molecules or hydrated protons, weakening the continuity of the original hydrogen bond network between water molecules in the electrolyte and reducing the activity of hydrated proton migration and participation in the cathode hydrogen evolution reaction. Compounds containing S=O, C=O, COC, or nitrogen-containing coordination groups can coordinate with ferrous ions or compete with them for solvation, partially altering the coordination state of water molecules in the first solvation layer of ferrous ions, thereby regulating the reduction and deposition environment of ferrous ions. Simultaneously, the dipole interactions generated by the strongly polar groups can affect the orientation and distribution of water molecules, hydrated protons, and ferrous ions near the cathode, changing the competitive relationship between the hydrogen evolution side reaction and the reduction and deposition of ferrous ions. Therefore, the solvation additive of the present invention can suppress hydrogen evolution side reactions from two levels: the electrolyte bulk structure and the cathode interface reaction environment, promote stable reduction and deposition of ferrous ions, and improve the density of the deposition layer.

[0019] In some embodiments, the solvation additive includes small molecule compounds and / or polymers.

[0020] In this invention, "small molecule compound" refers to a pure substance with a relatively small molecular weight (generally below 1000), a relatively simple structure, and no long-chain polymer structure. "Polymer" refers to a substance with a very large molecular weight (usually above 10,000) that is composed of many identical simple structural units (monomers) repeatedly linked by covalent bonds.

[0021] In some embodiments, when the solvating additive is a small molecule compound, the molar ratio of the solvating additive to ferrous ions in the acidic electrolyte is 0.01-0.50, for example, it can be 0.01, 0.02, 0.05, 0.08, 0.10, 0.12, 0.15, 0.18, 0.20, 0.22, 0.25, 0.28, 0.30, 0.32, 0.35, 0.38, 0.40, 0.42, 0.45, 0.48 or 0.50, preferably 0.05-0.30, more preferably 0.10-0.20, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0022] This invention further controls the molar ratio of small molecule solvation additives to ferrous ions in the acidic electrolyte to be 0.01-0.50. This molar ratio affects the solvation regulation of water molecules, hydrated protons, and ferrous ions in the electrolyte, and further influences the competitive relationship between the cathode hydrogen evolution side reaction and the iron deposition process. If the amount of small molecule solvation additive is too small, its interaction with water molecules, hydrated protons, or ferrous ions is insufficient, making it difficult to effectively change the hydrogen bond network and the local solvation structure of ferrous ions in the electrolyte. This results in limited suppression of the hydrogen evolution side reaction, and no significant improvement in cathode current efficiency and deposition layer density. Conversely, if the amount of small molecule solvation additive is too large, it may excessively alter the electrolyte viscosity, ion migration, and ferrous ion reduction environment, leading to impaired mass transfer of ferrous ions to the cathode surface or decreased stability of the deposition process. It may also increase the risk of residual organic components, which is detrimental to obtaining a high-purity, dense iron deposition layer. Therefore, controlling the molar ratio of small molecule solvation additives to ferrous ions within the range of 0.01-0.50 is more conducive to balancing hydrogen evolution suppression, iron deposition efficiency, and deposition layer quality.

[0023] In some embodiments, when the solvation additive is a polymer, the volume fraction of the solvation additive in the acidic electrolyte is 1%-30%, for example, it can be 1%, 5%, 8%, 10%, 15%, 18%, 20%, 25%, 28% or 30%, preferably 3%-20%, more preferably 5%-10%, but not limited to the listed values, other unlisted values ​​within the range are also applicable.

[0024] This invention further controls the volume fraction of the polymer solvation additive in the acidic electrolyte to be 1%-30%. The volume fraction of the polymer solvation additive affects the electrolyte viscosity, ion migration, cathode interface wetting state, and the mass transfer and reduction deposition process of ferrous ions. If the content of the polymer solvation additive is too low, the interaction between the ether radical groups or other polar groups in its molecular chain and water molecules, hydrated protons, and ferrous ions is insufficient, making it difficult to effectively regulate the solvation structure of the electrolyte and the reaction environment at the cathode interface. This results in limited suppression of hydrogen evolution side reactions and minimal improvement in the density of the deposited layer. Conversely, if the content of the polymer solvation additive is too high, it significantly increases the electrolyte viscosity and the mass transfer resistance of ferrous ions to the cathode surface, leading to a decrease in the iron deposition rate or instability in the deposition process. It may also increase the risk of uneven deposited layer surface or residual organic components. Therefore, controlling the volume fraction of the polymer solvation additive in the acidic electrolyte within the range of 1%-30% is beneficial for achieving a balance between hydrogen evolution suppression, ion transport, and deposited layer quality.

[0025] In some embodiments, the small molecule compound includes any one or a combination of at least two of sulfoxide compounds, sulfone compounds, amide compounds, lactam compounds, ether compounds, alcohol compounds, alcohol ether compounds, nitrile compounds, or urea compounds. Typical but non-limiting combinations include combinations of sulfoxide compounds and sulfone compounds, combinations of amide compounds and lactam compounds, combinations of alcohol compounds and alcohol ether compounds, combinations of nitrile compounds and urea compounds, combinations of sulfone compounds and amide compounds, combinations of ether compounds, alcohol compounds and alcohol ether compounds, or combinations of amide compounds, lactam compounds and ether compounds, preferably sulfoxide compounds.

[0026] In this invention, the solvation additive is a sulfoxide or sulfone compound containing an S=O group. This type of compound can change the local environment of water molecules and hydrated protons through the strongly polar S=O group and affect the solvation state of ferrous ions, thereby increasing the kinetic resistance of the hydrogen evolution side reaction.

[0027] In some embodiments, the polymer comprises a polyether compound.

[0028] In this invention, the ether radical groups in the polyether compounds can interact with water molecules and hydrated protons, regulating the electrolyte environment and the cathode interface reaction process, thereby improving the quality of the deposited layer.

[0029] In some embodiments, the small molecule compound includes any one or a combination of at least two of dimethyl sulfoxide, sulfolane, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerol, ethylene glycol monomethyl ether, or urea. Typical but non-limiting combinations include combinations of dimethyl sulfoxide and sulfolane, combinations of N,N-dimethylformamide and N,N-dimethylacetamide, combinations of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone, combinations of ethylene glycol and glycerol, combinations of ethylene glycol monomethyl ether and urea, combinations of ethylene glycol, glycerol, ethylene glycol monomethyl ether and urea, or combinations of dimethyl sulfoxide, sulfolane, and N,N-dimethylformamide, preferably dimethyl sulfoxide.

[0030] In some embodiments, the polymer comprises any one or a combination of at least two of polyethylene glycol, polypropylene glycol, polyetheramine, or polyethylene ether. Typical but non-limiting combinations include combinations of polyethylene glycol and polypropylene glycol, combinations of polypropylene glycol and polyetheramine, combinations of polyetheramine and polyethylene ether, combinations of polyethylene glycol, polypropylene glycol and polyetheramine, combinations of polypropylene glycol, polyetheramine, and polyethylene ether, combinations of polyethylene glycol, polyetheramine, and polyethylene ether, or combinations of polyethylene glycol and polyethylene ether.

[0031] In some embodiments, the ferrous salt solution comprises any one or a combination of at least two of ferrous sulfate solution, ferrous chloride solution, ferrous methanesulfonate solution, or ferrous aminosulfonate solution. Typical but non-limiting combinations include combinations of ferrous sulfate solution and ferrous chloride solution, combinations of ferrous sulfate solution and ferrous methanesulfonate solution, combinations of ferrous sulfate solution and ferrous aminosulfonate solution, combinations of ferrous chloride solution and ferrous methanesulfonate solution, or combinations of ferrous sulfate solution, ferrous methanesulfonate solution, and ferrous aminosulfonate solution, preferably ferrous sulfate solution.

[0032] In some embodiments, the acid solution includes any one or a combination of at least two of sulfuric acid solution, hydrochloric acid solution, methanesulfonic acid solution, or aminosulfonic acid solution. Typical but non-limiting combinations include combinations of sulfuric acid solution and hydrochloric acid solution, combinations of methanesulfonic acid solution and aminosulfonic acid solution, combinations of hydrochloric acid solution and methanesulfonic acid solution, combinations of sulfuric acid solution, hydrochloric acid solution and methanesulfonic acid solution, or combinations of hydrochloric acid solution, methanesulfonic acid solution and aminosulfonic acid solution, preferably sulfuric acid.

[0033] In some embodiments, the stabilizer comprises any one or a combination of at least two of ascorbic acid, ascorbate, sulfite, hypophosphite, or hydroxylamine compounds. Typical but non-limiting combinations include combinations of ascorbic acid and ascorbate, combinations of sulfite and hypophosphite, combinations of hypophosphite and hydroxylamine compounds, combinations of ascorbate and sulfite, combinations of ascorbic acid, ascorbate, and sulfite, or combinations of sulfite, hypophosphite, and hydroxylamine compounds.

[0034] In some embodiments, the ascorbic acid includes L-ascorbic acid;

[0035] In some embodiments, the ascorbate salt includes any one or a combination of at least two of sodium ascorbate, potassium ascorbate, or calcium ascorbate. Typical but non-limiting combinations include a combination of sodium ascorbate and potassium ascorbate, a combination of potassium ascorbate and calcium ascorbate, a combination of sodium ascorbate and calcium ascorbate, or a combination of sodium ascorbate, potassium ascorbate, and calcium ascorbate.

[0036] In some embodiments, the sulfite includes any one or a combination of at least two of sodium sulfite, potassium sulfite, ammonium sulfite, sodium bisulfite, or sodium metabisulfite. Typical but non-limiting combinations include combinations of sodium sulfite and potassium sulfite, combinations of potassium sulfite and ammonium sulfite, combinations of sodium bisulfite and sodium metabisulfite, combinations of sodium sulfite, potassium sulfite, and ammonium sulfite, combinations of ammonium sulfite, sodium bisulfite, and sodium metabisulfite, or combinations of sodium sulfite and ammonium sulfite.

[0037] In some embodiments, the hypophosphite comprises any one or a combination of at least two of sodium hypophosphite, potassium hypophosphite, ammonium hypophosphite, or calcium hypophosphite. Typical but non-limiting combinations include combinations of sodium hypophosphite and potassium hypophosphite, combinations of potassium hypophosphite and ammonium hypophosphite, combinations of ammonium hypophosphite and calcium hypophosphite, combinations of sodium hypophosphite, ammonium hypophosphite, and calcium hypophosphite, combinations of sodium hypophosphite, potassium hypophosphite, and calcium hypophosphite, or combinations of sodium hypophosphite, potassium hypophosphite, ammonium hypophosphite, and calcium hypophosphite.

[0038] In some embodiments, the hydroxylamine compound includes any one or a combination of at least two of hydroxylamine hydrochloride, hydroxylamine sulfate, hydroxylamine phosphate, or N,N-diethylhydroxylamine. Typical but non-limiting combinations include combinations of hydroxylamine hydrochloride and hydroxylamine sulfate, combinations of hydroxylamine sulfate and hydroxylamine phosphate, combinations of hydroxylamine phosphate and N,N-diethylhydroxylamine, combinations of hydroxylamine hydrochloride, hydroxylamine sulfate, and hydroxylamine phosphate, combinations of hydroxylamine sulfate, hydroxylamine phosphate, and N,N-diethylhydroxylamine, or combinations of hydroxylamine hydrochloride and hydroxylamine phosphate.

[0039] Preferably, the stabilizer comprises L-ascorbic acid.

[0040] In some embodiments, the concentration of ferrous ions in the acidic electrolyte is 50 g / L to 150 g / L, for example, it can be 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L or 150 g / L, preferably 100 g / L to 130 g / L, more preferably 120 g / L to 130 g / L, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0041] In some embodiments, the concentration of the stabilizer in the acidic electrolyte is 0.5 g / L to 5 g / L, for example, it can be 0.5 g / L, 1.0 g / L, 1.5 g / L, 2.0 g / L, 2.5 g / L, 3.0 g / L, 3.5 g / L, 4.0 g / L, 4.5 g / L or 5 g / L, preferably 1 g / L to 3 g / L, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0042] This invention further controls the concentration of the stabilizer in the acidic electrolyte to 0.5 g / L-5 g / L. The concentration of the stabilizer in the acidic electrolyte affects the stability of ferrous ions, the redox environment of the electrolyte, and the quality of the cathode deposition layer. If the stabilizer concentration is too high, it may excessively alter the reducing environment of the electrolyte and increase the risk of residual organic or reducing components, thereby affecting the purity of the electrodeposited iron and the density of the deposition layer; if the stabilizer concentration is too low, it will affect the Fe... 2+ Oxidized to Fe 3+ Insufficient inhibition can easily lead to Fe in the electrolyte. 3+ Increased ferrous ion content can lead to problems such as hydrolysis, impurity inclusions, or uneven deposition layers, which are detrimental to obtaining high current efficiency and high-purity, dense iron deposition layers. Therefore, controlling the stabilizer concentration within the range of 0.5 g / L to 5 g / L is beneficial for maintaining the stability of ferrous ions in the acidic electrolyte, while balancing electrodeposition efficiency and product purity.

[0043] In some embodiments, the pH of the acidic electrolyte is 1.5-3.5, for example, it can be 1.5, 2.0, 2.5, 3.0 or 3.5, preferably 2.0-3.0, more preferably 2.5, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0044] In some embodiments, the stabilizer includes L-ascorbic acid.

[0045] In some embodiments, the electrodeposition temperature is 50°C-80°C, for example, it can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C, preferably 60°C-75°C, more preferably 70°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0046] In some embodiments, the electrodeposition time is 1h-10h, for example, it can be 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h, preferably 2h-8h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0047] In some embodiments, the electrodeposition current density is 50 A / m 2 -250A / m 2 For example, it could be 50A / m 2 80A / m 2 100A / m 2 120A / m 2 150A / m 2 180A / m 2 200A / m 2 220A / m 2 Or 250A / m 2 Preferably 150A / m 2 -220A / m 2 More preferably 190A / m 2 -210A / m 2 However, this does not limit the listed values; other unlisted values ​​within the range are also applicable.

[0048] This invention further controls the electrodeposition current density to 50 A / m²-250 A / m². The electrodeposition current density affects the cathode polarization, the ferrous ion reduction rate, the intensity of the hydrogen evolution side reaction, and the growth state of the deposited layer. If the current density is too high, the cathode polarization is enhanced, the hydrogen evolution side reaction is aggravated, the hydrogen bubble coverage on the cathode surface and the local mass transfer disturbance are enhanced, which can easily lead to problems such as looseness, porosity, dendrites or surface roughness in the deposited layer, and reduce the cathode current efficiency. If the current density is too low, the ferrous ion reduction deposition rate is slow, the deposition driving force is insufficient, the production efficiency is low, and it is difficult to obtain an iron deposited layer with sufficient thickness and good density. Therefore, the current density is controlled at 50 A / m². 2 -250A / m 2 Within this range, it is beneficial to achieve a balance between iron deposition rate, hydrogen evolution inhibition, and deposition layer quality.

[0049] In some embodiments, the cathode electrodeposit is stripped, cleaned, and dried before high-purity iron is obtained after electrodeposition.

[0050] In some embodiments, the cathode comprises any one or a combination of at least two of a titanium plate, a stainless steel plate, a copper plate, a nickel plate, or a surface-treated conductive substrate. Typical but non-limiting combinations include combinations of titanium and stainless steel plates, combinations of copper and nickel plates, combinations of nickel plates and surface-treated conductive substrates, combinations of titanium and copper plates, and combinations of stainless steel and nickel plates.

[0051] In some embodiments, the anode includes any one or a combination of at least two of the following: high-purity iron anode, industrial-pure iron anode, graphite anode, platinum anode, or titanium-based coated anode. Typical but non-limiting combinations include combinations of high-purity iron anode and industrial-pure iron anode, combinations of graphite anode and platinum anode, combinations of platinum anode and titanium-based coated anode, combinations of high-purity iron anode and graphite anode, combinations of high-purity iron anode and platinum anode, and combinations of industrial-pure iron anode and platinum anode.

[0052] The high-purity iron obtained in this invention has a purity of not less than 99.95%, preferably not less than 99.97%, and more preferably not less than 99.98%.

[0053] The high-purity iron obtained in this invention can be used in soft magnetic materials, iron-based functional materials, precision electromagnetic devices, electronic materials, or high-purity iron-based alloy raw materials.

[0054] As a preferred embodiment of the method described in this invention, the method includes the following steps:

[0055] (1) Mix ferrous salt solution, sulfuric acid solution, stabilizer and solvation additive to obtain an acidic electrolyte with ferrous ion concentration of 50 g / L-150 g / L, stabilizer concentration of 0.5 g / L-5 g / L and pH of 1.5-3.5;

[0056] (2) Place the cathode and anode in an acidic electrolyte at 50℃-80℃ and a current density of 50A / m 2 -250A / m 2 Under certain conditions, electrodeposition was carried out for 2-8 hours. The cathode electrodeposit was then stripped, cleaned, and dried to obtain high-purity iron.

[0057] The solvation additive in step (1) is a compound that interacts with water molecules, hydrated protons or ferrous ions through hydrogen bonding, coordination, dipole interaction or solvation.

[0058] Step (1) When the solvation additive is a small molecule compound, the molar ratio of the solvation additive to ferrous ions in the acidic electrolyte is 0.01-0.50. When the solvation additive is a polymer, the volume fraction of the solvation additive in the acidic electrolyte is 1%-30%.

[0059] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0060] Compared with the prior art, the present invention has at least the following beneficial effects:

[0061] (1) This invention changes the bulk structure of acidic sulfate electrolyte by introducing solvation additives, and adjusts the local solvation environment of water molecules, hydrated protons and ferrous ions, thereby reducing the competitive effect of hydrogen evolution side reaction on iron deposition.

[0062] (2) This invention does not rely solely on the adsorption effect of the cathode surface, which can reduce the risk of impurity residue that may be caused by traditional interfacial organic additives, and is conducive to improving the purity of high-purity iron products.

[0063] (3) The present invention can improve the cathode current efficiency, reduce the coverage of bubbles on the cathode surface and the interfacial mass transfer disturbance, and make the deposition layer more uniform and dense.

[0064] (4) The solvation additives used in this invention can be selected according to the electrolyte composition, process conditions and deposition quality requirements. They have a wide range of applications and are easy to connect with existing acidic ferrous salt electrolytes, especially the high-purity iron electrodeposition process of acidic sulfate ferrous system. Attached Figure Description

[0065] Figure 1 This is a schematic diagram of the reaction mechanism of the method for suppressing hydrogen evolution during high-purity iron electrodeposition provided in Embodiment 1 of the present invention;

[0066] Figure 2 This is a schematic diagram of the reaction mechanism of the high-purity iron electrodeposition process provided in Comparative Example 1 of the present invention. Detailed Implementation

[0067] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0068] The scope of this invention can be defined by lower and upper limits. The selected lower and upper limits define the boundaries of a specific range. The range defined in this way can be defined by the inclusion or exclusion of endpoints. Any endpoint can be independently selected for inclusion or exclusion, and all lower and upper limits can be arbitrarily combined to form new ranges. That is, any lower limit can be combined with any upper limit to form an effective range. For example, if the ranges of 60~120 and 80~110 are listed for specific parameters, it should be understood that the ranges of 60~110 and 80~120 also fall within the scope of this invention. In addition, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are also listed, then all ranges of 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5 fall within the scope of this invention. In this invention, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between 0 and 5 have been fully listed in this document, and "0~5" is only a shortened representation of this set of numerical combinations. When a parameter is expressed as an integer ≥2, it is equivalent to listing positive integers that meet the requirements, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. When a parameter is expressed as an integer selected from "2~10", it is equivalent to listing any integer among 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0069] In this invention, "a combination of at least two" refers to a quantity greater than or equal to 2 unless otherwise specified. For example, "any one or a combination of at least two" means that any one of the listed items can be selected, or a combination of at least two of the listed items formed in a manner that does not conflict and enables the implementation of this invention. In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" cover any one of two or more related listed items, as well as any and all combinations of the related listed items. The arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" means a set consisting of A, B, and combinations of A and B, where "containing A and / or B" can be understood, depending on the context of the statement, as containing A, containing B, or simultaneously containing both A and B. In this invention, "optional" means that the corresponding feature, component, step or solution is not necessary, that is, it is selected from either "with" or "without". If there are multiple "optional" limitations in a technical solution, unless otherwise specified and there is no technical conflict or mutual constraint, each "optional" limitation is independent and does not affect the others.

[0070] In this invention, technical features or solutions described using open-ended terms such as "comprising" or "including" do not exclude additional non-conflicting elements beyond the listed elements unless otherwise specified. They are considered to disclose both closed-ended features or solutions consisting solely of the listed elements and open-ended features or solutions that may include additional non-conflicting elements beyond the listed elements. For example, if A includes a1, a2, and a3, unless otherwise specified, this means that A can consist only of a1, a2, and a3, or it can include other non-conflicting elements based on a1, a2, and a3. This corresponds to the disclosure of technical solutions such as "A consists of a1, a2, and a3," "A is selected from a1, a2, and a3," and "A not only includes a1, a2, and a3, but may also include other non-conflicting elements." All embodiments and optional embodiments of this invention, unless otherwise specified and without technical conflict, can be combined to form new technical solutions, and such combinations fall within the scope of this invention. The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various locations throughout the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this invention can be combined with other embodiments that do not conflict with the technology. The ordinal numbers "first," "second," "third," and "fourth," etc., used in the expressions "first aspect," "second aspect," "third aspect," and "fourth aspect" in this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly specifying the importance or quantity of the indicated technical features. They serve only as a non-exhaustive enumeration and do not constitute a closed limitation on quantity.

[0071] In this invention, the order in which the steps are written in the methods described in each embodiment does not imply a strict execution order. The actual execution order of each step should be determined based on its function and possible internal logic. Unless otherwise specified, all steps of this invention can be executed in the order they are written, or in any order without technical conflict. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) executed sequentially, or it may include steps (b) and (a) executed sequentially. If the method also includes step (c), then step (c) can be added to the method in any order without conflict, including but not limited to the execution order of steps (a), (b), and (c), steps (a), (c), and (b), steps (c), (a), and (b), etc.

[0072] Unless otherwise specified, all reagents and consumables used in the following examples and comparative examples were purchased from conventional reagent manufacturers in the art; unless otherwise specified, the experimental methods and techniques used were conventional methods and techniques in the art.

[0073] Example 1

[0074] This embodiment provides a method for suppressing hydrogen evolution during high-purity iron electrodeposition, the method comprising the following steps:

[0075] (1) Mix ferrous sulfate heptahydrate solution, sulfuric acid solution, L-ascorbic acid and dimethyl sulfoxide solvation additive to obtain an acidic electrolyte with a ferrous ion concentration of 125 g / L, an L-ascorbic acid concentration of 2 g / L and a pH of 2.5;

[0076] In step (1), the molar ratio of dimethyl sulfoxide to ferrous ions in the acidic electrolyte is 0.15;

[0077] (2) Using a titanium plate as the cathode and a high-purity iron plate as the anode, the plates are placed in an acidic electrolyte at 70°C and a current density of 200 A / m. 2 Under certain conditions, electrodeposition was carried out for 6 hours. The cathode electrodeposit was then stripped, cleaned, and dried to obtain high-purity iron.

[0078] Example 2

[0079] This embodiment provides a method for suppressing hydrogen evolution during high-purity iron electrodeposition, the method comprising the following steps:

[0080] (1) A mixture of ferrous chloride solution, hydrochloric acid solution, sodium sulfite and polyethylene glycol 400 solubilizing additive was prepared to obtain an acidic electrolyte with a ferrous ion concentration of 100 g / L, a sodium sulfite concentration of 1 g / L and a pH of 3.

[0081] In step (1), the volume fraction of polyethylene glycol 400 in the acidic electrolyte is 5%.

[0082] (2) Using a titanium plate as the cathode and a high-purity iron plate as the anode, the plates were placed in an acidic electrolyte and electrodeposited for 5 hours at 50°C and a current density of 250 A / m². The cathode electrodeposit was then stripped, cleaned, and dried to obtain high-purity iron.

[0083] Example 3

[0084] This embodiment provides a method for suppressing hydrogen evolution during high-purity iron electrodeposition, the method comprising the following steps:

[0085] (1) A mixture of ferrous methanesulfonate solution, sulfuric acid solution, N,N-diethylhydroxylamine and N,N-dimethylformamide solubilizing additive was prepared to obtain an acidic electrolyte with a ferrous ion concentration of 150 g / L, an N,N-diethylhydroxylamine concentration of 3 g / L and a pH of 1.5.

[0086] In step (1), the molar ratio of N,N-dimethylformamide to ferrous ions in the acidic electrolyte is 0.15.

[0087] (2) Using a titanium plate as the cathode and a high-purity iron plate as the anode, the plates are placed in an acidic electrolyte at 80°C and a current density of 100 A / m. 2 Under certain conditions, electrodeposition was carried out for 8 hours. The cathode electrodeposit was then stripped, cleaned, and dried to obtain high-purity iron.

[0088] Example 4

[0089] This embodiment provides a method for suppressing hydrogen evolution during the electrodeposition of high-purity iron. The only difference between this method and Embodiment 1 is that the molar ratio of dimethyl sulfoxide to ferrous ions in the acidic electrolyte in step (1) is 0.005, while the other steps remain unchanged.

[0090] Example 5

[0091] This embodiment provides a method for suppressing hydrogen evolution during the electrodeposition of high-purity iron. The only difference between this method and Embodiment 1 is that in the acidic electrolyte of step (1), the molar ratio of dimethyl sulfoxide to ferrous ions is 1, and the other steps remain unchanged.

[0092] Example 6

[0093] This embodiment provides a method for suppressing hydrogen evolution during the electrodeposition of high-purity iron. The only difference between this method and Embodiment 2 is that the volume fraction of polyethylene glycol 400 in the acidic electrolyte in step (1) is 0.05%, while the other steps remain unchanged.

[0094] Example 7

[0095] This embodiment provides a method for suppressing hydrogen evolution during the electrodeposition of high-purity iron. The only difference between this method and Embodiment 2 is that the volume fraction of polyethylene glycol 400 in the acidic electrolyte in step (1) is 40%, while the other steps remain unchanged.

[0096] Example 8

[0097] This embodiment provides a method for suppressing hydrogen evolution during the high-purity iron electrodeposition process. The only difference between this method and Embodiment 1 is that the concentration of L-ascorbic acid in step (1) is 0.1 g / L, while the other steps remain unchanged.

[0098] Example 9

[0099] This embodiment provides a method for suppressing hydrogen evolution during the high-purity iron electrodeposition process. The only difference between this method and Embodiment 1 is that the concentration of L-ascorbic acid in step (1) is 10 g / L, while the other steps remain unchanged.

[0100] Comparative Example 1

[0101] This comparative example provides a method for a high-purity ferroelectric deposition process. The only difference between this method and Example 1 is that dimethyl sulfoxide is not added in step (1).

[0102] The reaction mechanism diagram of the method provided in Example 1 is shown below. Figure 1 As shown, by Figure 1 It is known that by adding solubilizing additives such as dimethyl sulfoxide to acidic electrolytes, the solubilizing additives can regulate the hydrogen bond network and the local solubilization structure of ferrous ions in the electrolyte through hydrogen bonding, dipole interaction, or coordination with water molecules, hydrated protons, and / or ferrous ions via their polar groups. This effect can reduce the competition from the cathode hydrogen evolution side reaction, decrease the generation and coverage of hydrogen bubbles on the cathode surface, make the ferrous ion reduction deposition process more stable, and improve the cathode current efficiency and the density of the deposited layer.

[0103] A schematic diagram of the reaction mechanism of the method provided in Comparative Example 1 is shown below. Figure 2 As shown, by Figure 2 It is known that, without the addition of solvating additives, the hydrogen bond network of water molecules in the acidic electrolyte is relatively complete, resulting in stronger ability of hydrated protons to migrate and participate in the cathode hydrogen evolution reaction, and making it easier for more hydrogen bubbles to be generated on the cathode surface. The generation, growth, and desorption of hydrogen bubbles can disrupt the local mass transfer and current distribution near the cathode, easily leading to problems such as loose deposition layers, pores, or rough surfaces. Figure 1 and Figure 2 As can be seen from the comparison, the present invention can achieve the technical effects of suppressing hydrogen evolution side reactions, improving current efficiency, and improving the deposition quality of high-purity iron by introducing solubilizing additives to adjust the electrolyte bulk structure and cathode reaction environment.

[0104] Comparative Example 2

[0105] This comparative example provides a method for a high-purity ferroelectrodeposition process. The only difference between this method and Example 1 is that the dimethyl sulfoxide in step (1) is replaced with an equimolar amount of sodium chloride, while the other steps remain unchanged.

[0106] test:

[0107] The cathode current efficiency and the purity of the obtained high-purity iron were tested using the methods provided in the examples and comparative examples:

[0108] (1) The cathode current efficiency is calculated based on the actual deposited iron mass and the theoretical deposited iron mass;

[0109] (2) The purity of electrodeposited iron was calculated using either the impurity element content deduction method or the total element impurity content statistical method. The test results are shown in Table 1 below.

[0110] Table 1

[0111]

[0112] The test results show that:

[0113] (1) Examples 1-3 employed different ferrous salts, acid solutions, stabilizers, solvation additives, and electrodeposition process conditions. Test results showed that under each of the specific combinations described above, the method of this invention could be implemented and electrodeposited iron with high cathode current efficiency and purity could be obtained, indicating that the method of this invention is applicable to acidic ferrous salt electrolytes with different compositions and different electrodeposition process conditions. Specifically, Example 1 used dimethyl sulfoxide as a solvation additive, achieving a cathode current efficiency of 95.25% and an iron purity of 99.9812%. It should be noted that, due to differences in the basic electrolyte composition and electrodeposition parameters of Examples 1-3, the test results are mainly used to illustrate the feasibility of different technical solutions and are not intended for a direct horizontal comparison of the effects of different solvation additives.

[0114] (2) A comparison of Examples 1 and 4-5 shows that when the molar ratio of dimethyl sulfoxide to ferrous ions is too low, the solvation additive has insufficient effect on regulating the local solvation environment of water molecules, hydrated protons, and ferrous ions, resulting in limited hydrogen evolution inhibition. When the molar ratio is too high, the electrolyte viscosity, ion migration, and ferrous ion reduction and deposition process may be adversely affected, leading to lower current efficiency and product purity than the preferred conditions. Therefore, controlling the molar ratio of small molecule solvation additive to ferrous ions within the range of 0.01-0.50 has better technical effects.

[0115] (3) A comparison between Example 2 and Examples 6-7 shows that when the content of polyethylene glycol 400 is too low, its effect on regulating the solvation structure of the electrolyte and the reaction environment at the cathode interface is insufficient; when the content of polyethylene glycol 400 is too high, the viscosity and mass transfer resistance of the electrolyte increase, the migration of ferrous ions to the cathode surface is affected, and the cathode current efficiency and the purity of iron decrease. Therefore, controlling the volume fraction of the polymer solvation additive in the acidic electrolyte within the range of 1%-30% is beneficial to balancing hydrogen evolution inhibition and iron deposition quality.

[0116] (4) A comparison between Example 1 and Examples 8-9 shows that the stabilizer concentration has a significant impact on the stability of ferrous ions and the electrodeposition effect. When the L-ascorbic acid concentration is too low, the inhibition effect on the oxidation of Fe²⁺ to Fe³⁺ is insufficient, and the stability of the electrolyte decreases. When the L-ascorbic acid concentration is too high, excessive stabilizer may change the electrolyte composition and the cathode reaction environment, and increase the risk of impurity residues or side reactions. Therefore, controlling the stabilizer concentration within the range of 0.5 g / L-5 g / L can better maintain the stability of the electrolyte, improve the cathode current efficiency, and improve the quality of the deposited layer.

[0117] (5) A comparison of Example 1 with Comparative Examples 1 and 2 shows that without the addition of the solvation additive, both the cathode current efficiency and the purity of iron are low. When dimethyl sulfoxide is replaced with a compound not limited to those specified in this invention, it is difficult to effectively regulate the solvation structure of water molecules, hydrated protons, and ferrous ions, resulting in limited suppression of the hydrogen evolution side reaction. Therefore, the solvation additive described in this invention has a specific solvation regulation effect, which can achieve higher cathode current efficiency and better high-purity iron deposition effect.

[0118] In summary, this invention, by introducing solvation additives, regulates the hydrogen bonding network, proton migration environment, and ferrous ion solvation structure in the acidic system, thereby suppressing the cathode hydrogen evolution side reaction, improving cathode current efficiency, and enhancing the density of the deposited layer and the purity of the high-purity iron product. This invention offers advantages such as simple process, weak hydrogen evolution side reaction, high current efficiency, good deposited layer quality, and wide applicability, making it suitable for the electrochemical preparation of high-purity iron and iron-based functional materials.

[0119] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for suppressing hydrogen evolution during high-purity iron electrodeposition, characterized in that, The method includes the following steps: A ferrous salt solution, an acid solution, a stabilizer, and a solubilizing additive are mixed to obtain an acidic electrolyte. High-purity iron is obtained by placing the cathode and anode in an acidic electrolyte and performing electrodeposition. The solvating additive is a compound that interacts with water molecules, hydrated protons, or ferrous ions through hydrogen bonding, coordination, dipole interaction, or solvation.

2. The method according to claim 1, characterized in that, The solvation additive contains any one or at least two polar groups selected from S=O, C=O, COC, -OH, -NH-, -CN, -SO2- or -CONH-. And / or, the solvation additives include small molecule compounds and / or polymers.

3. The method according to claim 2, characterized in that, When the solvating additive is a small molecule compound, the molar ratio of the solvating additive to ferrous ions in the acidic electrolyte is 0.01-0.50; And / or, when the solvation additive is a polymer, the volume fraction of the solvation additive in the acidic electrolyte is 1%-30%.

4. The method according to claim 2 or 3, characterized in that, The small molecule compounds include any one or a combination of at least two of the following: sulfoxide compounds, sulfone compounds, amide compounds, lactam compounds, ether compounds, alcohol compounds, alcohol ether compounds, nitrile compounds, or urea compounds; And / or, the polymer includes polyether compounds.

5. The method according to any one of claims 2-4, characterized in that, The small molecule compounds include any one or a combination of at least two of the following: dimethyl sulfoxide, sulfolane, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerol, ethylene glycol monomethyl ether, or urea. And / or, the polymer includes any one or a combination of at least two of polyethylene glycol, polypropylene glycol, polyetheramine, or polyvinyl ether.

6. The method according to any one of claims 1-5, characterized in that, The ferrous salt solution includes any one or a combination of at least two of the following: ferrous sulfate solution, ferrous chloride solution, ferrous methanesulfonate solution, or ferrous aminosulfonate solution. And / or, the acid solution includes any one or a combination of at least two of sulfuric acid solution, hydrochloric acid solution, methanesulfonic acid solution or aminosulfonic acid solution; And / or, the stabilizer comprises any one or a combination of at least two of ascorbic acid, ascorbate, sulfite, hypophosphite or hydroxylamine compounds.

7. The method according to any one of claims 1-6, characterized in that, The concentration of ferrous ions in the acidic electrolyte is 50 g / L-150 g / L; And / or, the concentration of the stabilizer in the acidic electrolyte is 0.5 g / L to 5 g / L; And / or, the pH of the acidic electrolyte is 1.5-3.5; And / or, the stabilizer includes L-ascorbic acid.

8. The method according to any one of claims 1-7, characterized in that, The electrodeposition temperature is 50℃-80℃; And / or, the electrodeposition time is 1h-10h; And / or, the electrodeposition current density is 50 A / m 2 -250A / m 2 .

9. The method according to any one of claims 1-8, characterized in that, Before obtaining high-purity iron, the electrodeposition process includes stripping, cleaning, and drying the cathode electrodeposit.

10. The method according to any one of claims 1-9, characterized in that, The cathode includes any one or a combination of at least two of the following: a titanium plate, a stainless steel plate, a copper plate, a nickel plate, or a surface-treated conductive substrate. And / or, the anode includes any one or a combination of at least two of the following: high-purity iron anode, industrial pure iron anode, graphite anode, platinum anode, or titanium-based coated anode.

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