Method for preparing cathode indium with compact and flat surface through electrolysis
By adding a composite additive of dimethylthiourea and gelatin to the electrolyte and combining it with suitable electrolysis conditions, the problem of non-dense and uneven cathodes in the electrolytic preparation of indium was solved, achieving efficient and low-cost improvement of indium deposition and enhancing current efficiency and purity.
Patent Information
- Application Number
- CN202511724397.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-23
- Publication Date
- 2026-02-24
AI Technical Summary
In the existing electrolytic process for preparing indium, dendritic deposits are easily formed on the cathode surface, resulting in a non-dense and uneven surface, low current efficiency, and low indium ion recovery rate. Existing improvement measures are still insufficient in terms of uniformity control.
By adding appropriate amounts of dimethylthiourea and gelatin as composite additives to the electrolyte, dendrite growth is suppressed and the deposition morphology of indium is optimized by regulating the cathode deposition kinetics. An electrolysis process using titanium plates as cathodes and sponge indium as anodes is adopted, and the cathode products are washed and dried under suitable electrolysis conditions.
It significantly improves the deposition morphology and quality of indium in the cathode, enhances the density and surface smoothness of the deposited layer, improves current efficiency and indium purity, is easy to operate and industrialize, and is low in cost and environmentally friendly.
Smart Images
Figure CN121556093A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrolytic indium production technology, and particularly relates to a method for preparing a dense and flat cathode indium by electrolysis. Background Technology
[0002] Indium is a typical rare metal with a low melting point (156.61℃) and an extremely high boiling point (2060℃). Due to its excellent electrical and optical properties, indium has important applications in the field of photovoltaic materials, mainly used to prepare transparent conductive oxide (TCO) thin films and copper indium gallium selenide (CIGS) thin film solar cells.
[0003] Electrolytic refining is the main industrial process for purifying indium metal and has been widely applied. However, several technical challenges remain to be addressed in practical applications. Taking the indium sulfate aqueous solution system as an example, this process currently faces the following main problems: First, the low conductivity of the electrolyte solution leads to low current efficiency; second, dendritic deposits easily form on the cathode surface, which may not only cause electrode short circuits but also affect product density; furthermore, the recovery rate of indium ions in the electrolyte after electrolysis is low, resulting in a waste of rare and precious metal resources.
[0004] To address the aforementioned technical bottlenecks, various process improvement schemes have been proposed in existing technologies. For example, adding NaCl to the indium sulfate electrolyte to increase the Cl- concentration... - The concentration of electrolytes is adjusted to improve conductivity; additives such as gelatin are introduced to regulate cathode deposition kinetics and inhibit dendrite growth; and diaphragm electrolysis technology is used to prevent anode mud from contaminating the electrolyte. Although these improvements have achieved some success, from an industrial application perspective, the existing process still has significant shortcomings in controlling the uniformity of cathode deposition morphology, and there is still considerable room for technological improvement. Summary of the Invention
[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for electrolytically preparing dense and flat cathode indium, thereby solving the problems of rough and uneven surface and non-dense structure of cathode indium deposited by existing electrolytic methods.
[0006] The objective of this invention is achieved through the following technical solution: A method for electrolytically preparing a dense and flat indium cathode includes the following steps: S1. Mix sulfuric acid, refined indium, water, NaCl, gelatin, and dimethylthiourea evenly to prepare a mixed solution; wherein the concentration of dimethylthiourea is 0.025~0.1 g / L, the concentration of indium ions is 80~85 g / L, the concentration of NaCl is 80~90 g / L, the concentration of gelatin is 0.5~0.6 g / L, and the pH of the mixed solution is 2~3; S2. Electrolysis is performed using the mixture prepared in step S1 as the electrolyte, with a titanium plate as the cathode and indium sponge as the anode. S3. After electrolysis, the electrolysis products on the cathode are washed and dried to obtain dense and smooth metallic indium.
[0007] In this invention, the addition of an appropriate amount of gelatin helps to improve the purity of indium at the cathode, as it can inhibit the co-deposition of impurity metals at the cathode. Compared to using gelatin alone, dimethylthiourea has a synergistic effect with gelatin: dimethylthiourea preferentially adsorbs onto the cathode surface, increasing the overpotential of the hydrogen evolution reaction, thereby inhibiting the hydrogen evolution side reaction; simultaneously, dimethylthiourea reacts with In... 3+ The formation of a complex lowers the activation energy for indium reduction, allowing In... 3+ Easier to reduce at the cathode. At lower concentrations, dimethylthiourea preferentially covers the hydrogen evolution active sites and promotes In... 3+ The indium crystals are uniformly distributed; however, at higher concentrations, excessive adsorption can occupy the active sites for indium deposition, hindering metal deposition and leading to a decrease in current efficiency. Therefore, under suitable dimethylthiourea concentration conditions, the rapid growth of indium crystals can be effectively suppressed, the grains can be refined, and a smooth, dense cathode indium deposition layer can ultimately be obtained.
[0008] Preferably, the sulfuric acid in step S1 is high-purity sulfuric acid.
[0009] Preferably, the purity of the refined indium in step S1 is 4N5.
[0010] Preferably, in step S1, the concentration of dimethylthiourea is 0.025~0.1 g / L, the concentration of indium ions is 80 g / L, the concentration of NaCl is 80 g / L, the concentration of gelatin is 0.5 g / L, and the pH of the mixture is 2.
[0011] Preferably, in step S2, the mixture is filtered, and the resulting filtrate is used as the electrolyte.
[0012] Preferably, the titanium plate described in step S2 needs to have its surface oxide film removed before use.
[0013] Preferably, in step S2, the sponge indium is first removed from its surface oxide film before use, and then tightly wrapped with filter paper and polyester cloth.
[0014] In this invention, firstly, removing the oxide film from the surfaces of the cathode and anode ensures good conductivity and reactivity of the electrodes, preventing uneven current distribution due to passivation. Secondly, wrapping the anode with filter paper and polyester cloth physically isolates it from anode sludge, preventing it from entering the electrolyte and contaminating the cathode, thereby ensuring the purity of the final product.
[0015] Preferably, the electrolysis operating conditions in step S2 are: a temperature of 25 °C and a current density of 90~100 A / m. 2 The electrode spacing is 5~6 cm, and the electrolysis time is 6~7 days.
[0016] Preferably, the washing method in step S3 is as follows: first, ultrasonic cleaning is performed using deionized water, and then ultrasonic cleaning is performed using anhydrous ethanol.
[0017] Preferably, the drying method in step S3 is as follows: drying at 28~30℃ for 12~15h.
[0018] Compared with the prior art, the beneficial effects of the present invention include: This invention does not rely on complex equipment or demanding process conditions. Simply introducing a composite additive system of dimethylthiourea and gelatin into a conventional electrolyte can significantly improve the deposition morphology and quality of indium cathodes. This method is simple to operate, easy to implement industrially, effectively suppresses cathode dendrite growth and hydrogen evolution side reactions, and improves the density and surface smoothness of the deposited layer. Furthermore, the additives used are used in small quantities, are inexpensive, and environmentally friendly, requiring no modification to existing electrolysis equipment, thus possessing good compatibility and promotional value. Attached Figure Description
[0019] Figure 1 The image shows a scanning electron microscope (SEM) image of the metallic indium prepared in Example 1 (magnification 1000x).
[0020] Figure 2 The image shows a scanning electron microscope (SEM) image of the metallic indium prepared in Example 2 (magnification 1000x).
[0021] Figure 3 The image shows a scanning electron microscope (SEM) image of the metallic indium prepared in Example 3 (magnification 1000x).
[0022] Figure 4 The image shows a scanning electron microscope (SEM) image of the metallic indium prepared in Example 4 (magnification 1000x).
[0023] Figure 5 Scanning electron microscope image of metallic indium prepared for Comparative Example 1 (magnification 1000x).
[0024] Figure 6 The image shows a scanning electron microscope (SEM) image of the metallic indium prepared in Comparative Example 2 (magnification 500x).
[0025] Figure 7 The image shows a scanning electron microscope (SEM) image of the metallic indium prepared in Comparative Example 3 (magnification 500x).
[0026] Figure 8The image shows a scanning electron microscope (SEM) image of the metallic indium prepared in Example 1 (magnification 500x). Detailed Implementation
[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0028] Example 1 A method for electrolytically preparing a dense and flat indium cathode, comprising the following specific steps: S1. High-purity sulfuric acid, 4N5 purity indium, deionized water, NaCl, gelatin, and dimethylthiourea are mixed evenly to prepare a mixture; wherein, the concentration of dimethylthiourea is 0.025 g / L, the concentration of indium ions is 80 g / L, the concentration of NaCl is 80 g / L, the concentration of gelatin is 0.5 g / L, and the pH of the mixture is 2. S2. Filter the mixture prepared in S1. Use the filtrate as the electrolyte in an electrolytic cell to treat the cathode titanium plate and anode sponge indium to remove the oxide film on their surfaces. Wrap the anode sponge indium with filter paper and polyester filter cloth. Place the treated cathode titanium plate and anode sponge indium in the electrolytic cell and, while maintaining a constant electrolyte volume, apply an electrolyte at 100 A / m³. 2 Electrolysis was carried out at a current density of 5 cm and an electrode spacing of 5 cm for 7 days. S3. After electrolysis, the electrolysis products on the cathode are ultrasonically cleaned sequentially with deionized water and anhydrous ethanol. After cleaning, they are placed in a 30°C drying oven and dried for 12 hours to obtain dense and smooth metallic indium. The purity of the metal is 99.996%.
[0029] Scanning electron microscope image (1000x magnification) of metallic indium prepared in Example 1 is shown below. Figure 1 As shown.
[0030] Example 2 A method for electrolytically preparing a dense and flat indium cathode, comprising the following specific steps: S1. High-purity sulfuric acid, 4N5 purity indium, deionized water, NaCl, gelatin, and dimethylthiourea are mixed evenly to prepare a mixture; wherein the concentration of dimethylthiourea is 0.05 g / L, the concentration of indium ions is 80 g / L, the concentration of NaCl is 80 g / L, the concentration of gelatin is 0.5 g / L, and the pH of the mixture is 2. S2. Filter the mixture prepared in S1. Use the filtrate as the electrolyte in an electrolytic cell to treat the cathode titanium plate and anode sponge indium to remove the oxide film on their surfaces. Wrap the anode sponge indium with filter paper and polyester filter cloth. Place the treated cathode titanium plate and anode sponge indium in the electrolytic cell and, while maintaining a constant electrolyte volume, apply an electrolyte at 100 A / m³. 2 Electrolysis was carried out at a current density of 5 cm and an electrode spacing of 5 cm for 7 days. S3. After electrolysis, the electrolysis products on the cathode are ultrasonically cleaned with deionized water and anhydrous ethanol in sequence. After cleaning, they are placed in a 30°C drying oven and dried for 12 hours to obtain dense and smooth metallic indium. The purity of the metal is 99.997%.
[0031] Scanning electron microscope image (1000x magnification) of the metallic indium prepared in Example 2 is shown below. Figure 2 As shown.
[0032] Example 3 A method for electrolytically preparing a dense and flat indium cathode, comprising the following specific steps: S1. High-purity sulfuric acid, 4N5 purity indium, deionized water, NaCl, gelatin, and dimethylthiourea are mixed evenly to prepare a mixture; wherein the concentration of dimethylthiourea is 0.075 g / L, the concentration of indium ions is 80 g / L, the concentration of NaCl is 80 g / L, the concentration of gelatin is 0.5 g / L, and the pH of the mixture is 2.5. S2. Filter the mixture prepared in S1. Use the filtrate as the electrolyte in an electrolytic cell to treat the cathode titanium plate and anode sponge indium to remove the oxide film on their surfaces. Wrap the anode sponge indium with filter paper and polyester filter cloth. Place the treated cathode titanium plate and anode sponge indium in the electrolytic cell and, while maintaining a constant electrolyte volume, apply an electrolyte at 100 A / m³. 2 Electrolysis was carried out at a current density of 5 cm and an electrode spacing of 5 cm for 7 days. S3. After electrolysis, the electrolysis products on the cathode are ultrasonically cleaned sequentially with deionized water and anhydrous ethanol. After cleaning, they are placed in a 30°C drying oven and dried for 12 hours to obtain dense and smooth metallic indium. The purity of the metal is 99.996%.
[0033] Scanning electron microscope image (1000x magnification) of the metallic indium prepared in Example 3 is shown below. Figure 3 As shown. A scanning electron microscope image (500x magnification) of the metallic indium prepared in Example 3 is shown below. Figure 8 As shown.
[0034] Example 4 A method for electrolytically preparing a dense and flat indium cathode, comprising the following specific steps: S1. High-purity sulfuric acid, 4N5 purity indium, deionized water, NaCl, gelatin, and dimethylthiourea are mixed evenly to prepare a mixed solution; wherein, the concentration of dimethylthiourea is 0.1 g / L, the concentration of indium ions is 80 g / L, the concentration of NaCl is 80 g / L, the concentration of gelatin is 0.5 g / L, and the pH of the mixed solution is 2.5. S2. Filter the mixture prepared in S1. Use the filtrate as the electrolyte in an electrolytic cell to treat the cathode titanium plate and anode sponge indium to remove the oxide film on their surfaces. Wrap the anode sponge indium with filter paper and polyester filter cloth. Place the treated cathode titanium plate and anode sponge indium in the electrolytic cell and, while maintaining a constant electrolyte volume, apply an electrolyte at 100 A / m³. 2 Electrolysis was carried out at a current density of 5 cm and an electrode spacing of 5 cm for 7 days. S3. After electrolysis, the electrolysis products on the cathode are ultrasonically cleaned sequentially with deionized water and anhydrous ethanol. After cleaning, they are placed in a 30°C drying oven and dried for 12 hours to obtain dense and smooth metallic indium. The purity of the metal is 99.994%.
[0035] Scanning electron microscope image (1000x magnification) of metallic indium prepared in Example 4 is shown below. Figure 4 As shown.
[0036] Comparative Example 1 A method for electrolytically preparing a dense and flat indium cathode, comprising the following specific steps: S1. Mix high-purity sulfuric acid, 4N5 purity indium, deionized water, NaCl and gelatin evenly to prepare a mixed solution; wherein, the concentration of indium ions is 80 g / L, the concentration of NaCl is 80 g / L, the concentration of gelatin is 0.5 g / L, and the pH of the mixed solution is 2. S2. Filter the mixture prepared in S1. Use the filtrate as the electrolyte in an electrolytic cell to treat the cathode titanium plate and anode sponge indium to remove the oxide film on their surfaces. Wrap the anode sponge indium with filter paper and polyester filter cloth. Place the treated cathode titanium plate and anode sponge indium in the electrolytic cell and, while maintaining a constant electrolyte volume, apply an electrolyte at 100 A / m³. 2 Electrolysis was carried out at a current density of 5 cm and an electrode spacing of 5 cm for 7 days. S3. After electrolysis, the electrolysis products on the cathode are ultrasonically cleaned sequentially with deionized water and anhydrous ethanol. After cleaning, they are dried in a 30°C drying oven for 12 hours to obtain metallic indium. The purity of the metal is 99.995%.
[0037] Scanning electron microscope image (1000x magnification) of metallic indium prepared in Comparative Example 1 is shown below. Figure 5 As shown.
[0038] Comparative Example 2 A method for electrolytically preparing a dense and flat indium cathode, comprising the following specific steps: S1. High-purity sulfuric acid, 4N5 purity indium, deionized water, NaCl, gelatin, and diethylthiourea are mixed evenly to prepare a mixture; wherein the concentration of diethylthiourea is 0.05 g / L, the concentration of indium ions is 80 g / L, the concentration of NaCl is 80 g / L, the concentration of gelatin is 0.5 g / L, and the pH of the mixture is 2. S2. Filter the mixture prepared in S1. Use the filtrate as the electrolyte in an electrolytic cell to treat the cathode titanium plate and anode sponge indium to remove the oxide film on their surfaces. Wrap the anode sponge indium with filter paper and polyester filter cloth. Place the treated cathode titanium plate and anode sponge indium in the electrolytic cell and, while maintaining a constant electrolyte volume, apply an electrolyte at 100 A / m³. 2 Electrolysis was carried out at a current density of 5 cm and an electrode spacing of 5 cm for 7 days. S3. After electrolysis, the electrolysis products on the cathode are ultrasonically cleaned sequentially with deionized water and anhydrous ethanol. After cleaning, they are placed in a 30°C drying oven and dried for 12 hours to obtain metallic indium. The purity of the metal is 99.996%.
[0039] Scanning electron microscope image (500x magnification) of indium metal prepared in Comparative Example 2 is shown below. Figure 6 As shown.
[0040] Comparative Example 3 A method for electrolytically preparing a dense and flat indium cathode, comprising the following specific steps: S1. High-purity sulfuric acid, 4N5 purity indium, deionized water, NaCl, gelatin, and phenylthiourea are mixed evenly to prepare a mixture; wherein, the concentration of phenylthiourea is 0.05 g / L, the concentration of indium ions is 80 g / L, the concentration of NaCl is 80 g / L, the concentration of gelatin is 0.5 g / L, and the pH of the mixture is 2. S2. Filter the mixture prepared in S1. Use the filtrate as the electrolyte in an electrolytic cell to treat the cathode titanium plate and anode sponge indium to remove the oxide film on their surfaces. Wrap the anode sponge indium with filter paper and polyester filter cloth. Place the treated cathode titanium plate and anode sponge indium in the electrolytic cell and, while maintaining a constant electrolyte volume, apply an electrolyte at 100 A / m³. 2 Electrolysis was carried out at a current density of 5 cm and an electrode spacing of 5 cm for 7 days. S3. After electrolysis, the electrolysis products on the cathode are ultrasonically cleaned sequentially with deionized water and anhydrous ethanol. After cleaning, they are placed in a 30°C drying oven and dried for 12 hours to obtain metallic indium. The purity of the metal is 99.996%.
[0041] Scanning electron microscope image (500x magnification) of indium metal prepared in Comparative Example 3 is shown below. Figure 7 As shown.
[0042] Depend on Figures 1-5 It can be seen that the introduction of the additive dimethylthiourea can effectively improve the surface uniformity of the indium cathode. Further comparison... Figures 6-8 It was found that only dimethylthiourea and gelatin had a significant synergistic effect, which could significantly inhibit dendrite growth and improve the density of the deposited layer; in contrast, the combination of phenylthiourea and diethylthiourea with gelatin did not show a significant synergistic effect and the deposited morphology was poor.
[0043] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.
Claims
1. A method for electrolytically preparing a dense and smooth surface indium cathode, characterized in that, Includes the following steps: S1. Mix sulfuric acid, refined indium, water, NaCl, gelatin, and dimethylthiourea evenly to prepare a mixed solution; wherein the concentration of dimethylthiourea is 0.025~0.1 g / L, the concentration of indium ions is 80~85 g / L, the concentration of NaCl is 80~90 g / L, the concentration of gelatin is 0.5~0.6 g / L, and the pH of the mixed solution is 2~3; S2. Electrolysis is performed using the mixture prepared in step S1 as the electrolyte, with a titanium plate as the cathode and indium sponge as the anode. S3. After electrolysis, the electrolysis products on the cathode are washed and dried to obtain dense and smooth metallic indium.
2. The method for preparing a dense and flat cathode indium by electrolysis according to claim 1, characterized in that, In step S1, the concentration of dimethylthiourea is 0.025~0.1 g / L, the concentration of indium ions is 80 g / L, the concentration of NaCl is 80 g / L, the concentration of gelatin is 0.5 g / L, and the pH of the mixture is 2.
3. The method for preparing a dense and flat cathode indium by electrolysis according to claim 1, characterized in that, The sulfuric acid mentioned in step S1 is high-purity sulfuric acid.
4. The method for preparing a dense and flat cathode indium by electrolysis according to claim 1, characterized in that, The purity of the refined indium in step S1 is 4N5.
5. The method for preparing a dense and flat cathode indium by electrolysis according to claim 1, characterized in that, In step S2, the mixture is filtered, and the resulting filtrate is used as the electrolyte.
6. The method for preparing a dense and flat cathode indium by electrolysis according to claim 5, characterized in that, The titanium plate described in step S2 needs to have its surface oxide film removed before use.
7. The method for preparing a dense and flat cathode indium by electrolysis according to claim 6, characterized in that, In step S2, the sponge indium is first removed from its surface oxide film before use, and then wrapped tightly with filter paper and polyester cloth.
8. The method for electrolytically preparing a dense and flat indium cathode according to claim 1, characterized in that, The electrolysis operating conditions in step S2 are: temperature 25℃, current density 90~100 A / m 2 The electrode spacing is 5~6 cm, and the electrolysis time is 6~7 days.
9. The method for preparing a dense and flat cathode indium by electrolysis according to claim 1, characterized in that, The specific washing method described in step S3 is as follows: first, use deionized water for ultrasonic cleaning, and then use anhydrous ethanol for ultrasonic cleaning.
10. The method for preparing a dense and flat cathode indium by electrolysis according to claim 1, characterized in that, The specific drying method described in step S3 is as follows: drying at 28~30℃ for 12~15 hours.