An inert anode and its preparation method and application

Abstract

The application provides an inert anode and a preparation method and application thereof, and belongs to the technical field of electrolytic aluminum anode materials. The anode substrate is pretreated and then coated, dried and solidified in a polytetrafluoroethylene dispersion liquid to obtain the inert anode. The tungsten anode is surface-modified, the excellent corrosion resistance and electrochemical stability are maintained, the bubble dynamic behavior is significantly optimized, and the efficient separation of chlorine bubbles and the synchronous improvement of current efficiency are realized in the process of low-temperature electrolytic aluminum in ionic liquids.

Description

Technical Field

[0001] This invention relates to the field of electrolytic aluminum anode materials technology, and in particular to an inert anode, its preparation method, and its application. Background Technology

[0002] The industrial production of aluminum has long relied on high-temperature molten salt electrolysis (Hall-Hellenic process), a process characterized by high energy consumption and significant emissions of greenhouse gases and fluorine-containing pollutants. Developing low-temperature aluminum electrolysis technology is crucial for the industry's green transformation. Low-temperature electrolyte systems, represented by aluminochloroaluminate ionic liquids, offer the possibility of low-temperature electrolysis due to their low melting point, high conductivity, and low volatility. However, in actual operation of this system, the excessive adhesion and accumulation of bubbles generated by the chlorine evolution reaction at the anode on the electrode surface creates a severe "bubble shielding effect." This not only significantly increases the reaction overpotential and energy consumption but also leads to instability in the electrolysis process, becoming one of the core bottlenecks restricting the application of this technology.

[0003] The retention behavior of bubbles on the electrode surface is influenced by both surface properties and the electrolysis environment. When bubbles cannot detach in time, they can cover part of the active sites, reducing the effective electrochemical area and leading to an increase in the actual current density and local potential shift. More seriously, densely packed bubbles may form a continuous gas film, blocking the mass transfer of reacting ions, causing a sharp drop in electrolysis efficiency or even interruption of the reaction. The surface characteristics of the inert anode materials commonly used in low-temperature aluminum electrolysis with ionic liquids are often unfavorable for bubble nucleation and detachment; therefore, simply replacing the material cannot fundamentally solve the bubble shielding problem.

[0004] Therefore, researching an inert anode and its preparation method can effectively promote the rapid detachment of bubbles from the surface of the inert anode, which is of great significance for unleashing the full potential of ionic liquid low-temperature electrolytic aluminum technology. Summary of the Invention

[0005] The purpose of this invention is to provide an inert anode, its preparation method, and its application, in order to solve the problem in the prior art where severe bubble adhesion on the surface of the inert anode during the electrolysis of aluminochloride ion liquids hinders the reaction and affects the electrolysis efficiency.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: The present invention provides a method for preparing an inert anode, comprising the following steps: pretreating the anode substrate and then coating it in a polytetrafluoroethylene dispersion, drying and curing it to obtain an inert anode.

[0007] Preferably, the anode substrate is a tungsten mesh, a tungsten rod, or a tungsten sheet.

[0008] Preferably, the pretreatment process is as follows: the anode substrate is sequentially acid-washed and water-washed.

[0009] Preferably, the polytetrafluoroethylene dispersion contains 0.1-3% polytetrafluoroethylene by mass.

[0010] Preferably, the coating time is 20-40 minutes.

[0011] Preferably, the coating process requires a draining treatment.

[0012] Preferably, the drying and curing temperature is room temperature, and the drying and curing time is 10~14h.

[0013] The present invention also provides an inert anode prepared by the above-described method for preparing an inert anode, wherein the inert anode has an air-repellent thin film coating.

[0014] The present invention also provides an application of the above-described inert anode in low-temperature electrolytic aluminum.

[0015] The beneficial effects of this invention are: This invention directly and effectively solves the problem of "bubble shielding" by constructing a robust ultra-thin gas-repellent film coating on the surface of the anode substrate. The prepared inert anode maintains the excellent conductivity and corrosion resistance of the substrate while significantly changing the behavior of the gas-liquid-solid three-phase interface, strongly promoting the rapid detachment of chlorine bubbles, reducing the bubble shielding effect, thereby reducing the anode overpotential, stabilizing the electrolysis current, and improving the current efficiency.

[0016] This invention significantly enhances the surface gas-repellent properties of the inert anode by modifying the surface of the tungsten anode, while maintaining excellent corrosion resistance and electrochemical stability, and significantly optimizes the bubble dynamics behavior. This enables the efficient removal of chlorine bubbles and the simultaneous improvement of current efficiency in the low-temperature electrolysis of aluminum with ionic liquids. Attached Figure Description

[0017] Figure 1 The LSV curves are for the tungsten mesh inert anodes of Examples 1-4 and Comparative Example 1. Figure 2 The following are the it curves of the tungsten mesh inert anodes of Examples 1-4 and Comparative Example 1; Figure 3 The image shows the surface morphology of the tungsten mesh inert anode in Comparative Example 1 at a constant potential of 3V. Figure 4 The attached diagram shows the rapid bubble removal of the tungsten mesh inert anode in Example 2 under a constant potential of 3V. Detailed Implementation

[0018] The present invention provides a method for preparing an inert anode, comprising the following steps: pretreating the anode substrate and then coating it in a polytetrafluoroethylene dispersion, drying and curing it to obtain an inert anode.

[0019] In this invention, the anode substrate is a tungsten mesh, a tungsten rod, or a tungsten sheet.

[0020] In this invention, the specific process of the pretreatment is as follows: the anode substrate is sequentially acid-washed and water-washed.

[0021] In this invention, the polytetrafluoroethylene dispersion contains 0.1-3% polytetrafluoroethylene by mass, specifically 0.1%, 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, or 3%.

[0022] In this invention, the coating time is 20-40 minutes, specifically 20 minutes, 25 minutes, 30 minutes, 35 minutes, or 40 minutes. The coating time is to ensure that the polytetrafluoroethylene dispersion fully wets the porous structure of the anode substrate, forming a uniform liquid film on the substrate surface.

[0023] In this invention, the coating process also requires a draining treatment.

[0024] In this invention, the drying and curing temperature is room temperature, and the drying and curing time is 10~14h, specifically 10h, 11h, 12h, 13h, or 14h.

[0025] The present invention also provides an inert anode prepared by the above-described method for preparing an inert anode, wherein the inert anode has an air-repellent thin film coating.

[0026] In this invention, the gas-repellent thin film coating is composed of dense nano-sized polytetrafluoroethylene particles. The nano-sized polytetrafluoroethylene particles are superimposed with the micron-sized substrate mechanical grooves to form a continuous and robust micro-nano composite coating.

[0027] This invention modifies the surface of the inert anode substrate to form a gas-repellent thin film coating, fundamentally changing the wettability of the inert anode surface. Without excessively increasing the interfacial resistance of the precursor, it effectively controls the desorption behavior of chlorine bubbles and significantly alleviates the "bubble shielding effect" during the electrolysis process.

[0028] The present invention also provides an application of the above-described inert anode in low-temperature electrolytic aluminum.

[0029] In this invention, the low-temperature electrolytic aluminum uses aluminochloride ionic liquid as the electrolyte.

[0030] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0031] Example 1

[0032] Using a tungsten mesh as the anode substrate, the surface was sequentially acid-washed with dilute hydrochloric acid (1 mol / L) and ultrasonically cleaned with deionized water to remove impurities and obtain a clean surface.

[0033] Weigh out the aqueous dispersion of polytetrafluoroethylene (PTFE) and dilute it with deionized water to a PTFE content of 0.1%. Immerse the pretreated tungsten mesh completely in the 0.1% PTFE coating solution for 30 minutes. Then remove it, drain off the excess solution, and place the coated tungsten mesh in a vacuum drying oven to dry and cure at room temperature for 12 hours to form a PTFE gas-repellent thin film layer, thus obtaining the tungsten mesh inert anode.

[0034] Example 2

[0035] The difference from Example 1 is that a polytetrafluoroethylene aqueous dispersion was weighed and diluted with deionized water to a polytetrafluoroethylene (PTFE) mass content of 0.5%. The pretreated tungsten mesh was completely immersed in a 0.5% polytetrafluoroethylene coating solution, and all other conditions were the same, to obtain a tungsten mesh inert anode.

[0036] Example 3

[0037] The difference from Example 1 is that a polytetrafluoroethylene aqueous dispersion was weighed and diluted with deionized water to a polytetrafluoroethylene (PTFE) content of 1%. The pretreated tungsten mesh was completely immersed in the 1% polytetrafluoroethylene coating solution, and all other conditions were the same, to obtain a tungsten mesh inert anode.

[0038] Example 4

[0039] The difference from Example 1 is that a polytetrafluoroethylene aqueous dispersion was weighed and diluted with deionized water to a polytetrafluoroethylene (PTFE) content of 3%. The pretreated tungsten mesh was completely immersed in the 3% polytetrafluoroethylene coating solution, and all other conditions were the same, to obtain a tungsten mesh inert anode.

[0040] Example 5

[0041] The difference from Example 2 is that the substrate is a tungsten sheet, while all other conditions are the same, resulting in a tungsten sheet inert anode.

[0042] Example 6

[0043] The difference from Example 2 is that the substrate is a tungsten rod, while all other conditions are the same, resulting in a tungsten sheet inert anode.

[0044] Comparative Example 1

[0045] Using a tungsten mesh as the anode substrate, the surface was sequentially acid-washed with dilute hydrochloric acid (1 mol / L) and ultrasonically cleaned with deionized water to remove impurities and obtain a clean surface.

[0046] The pretreated tungsten mesh was completely immersed in deionized water for 30 minutes, then removed and placed in a vacuum drying oven to dry and cure at room temperature for 12 hours to obtain a tungsten mesh inert anode.

[0047] Performance testing: (1) Electrochemical tests were performed on the tungsten mesh inert anodes of Examples 1-4 and Comparative Example 1 using an electrochemical workstation. The counter electrode was a platinum sheet electrode, and the reference electrode was an aluminum wire electrode. Polarization curves were measured at a scan rate of 10 mV / s, and electrochemical stability tests were performed at a voltage of 3 V. The test results are as follows: Figure 1 and Figure 2 As shown.

[0048] from Figure 1 It can be seen that the tungsten mesh inert anode prepared with 0.5% polytetrafluoroethylene coating solution has the highest chlorine evolution current density, indicating that it has the best chlorine evolution activity.

[0049] from Figure 2 It can be seen that the tungsten mesh inert anode prepared with 0.5% polytetrafluoroethylene coating solution has the highest current density and the most stable current response.

[0050] (2) The bubble detachment behavior on the surface of the tungsten mesh inert anode of Comparative Example 1 and the tungsten mesh inert anode of Example 2 was observed using a high-speed camera. The results are as follows: Figure 3 and Figure 4 As shown, the tungsten mesh inert anode of Comparative Example 1 did not form large-volume bubbles and was difficult to desorb, while the tungsten mesh inert anode of Example 2 was able to rapidly form large-volume bubbles and desorb.

[0051] The tungsten mesh inert anode prepared by the 0.5% polytetrafluoroethylene coating solution provided by this invention exhibits higher current density, more stable current response, and better bubble desorption kinetics in the chlorine evolution reaction, thereby significantly improving the current efficiency and operational stability of low-temperature aluminum electrolysis with ionic liquids.

[0052] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an inert anode, characterized in that, The process includes the following steps: after pretreating the anode substrate, it is coated in a polytetrafluoroethylene dispersion, dried and cured to obtain an inert anode.

2. The method for preparing an inert anode according to claim 1, characterized in that, The anode substrate is a tungsten mesh, tungsten rod, or tungsten sheet.

3. The method for preparing the inert anode according to claim 1 or 2, characterized in that, The specific process of the pretreatment is as follows: the anode substrate is sequentially acid-washed and water-washed.

4. The method for preparing an inert anode according to claim 3, characterized in that, The polytetrafluoroethylene dispersion contains 0.1-3% polytetrafluoroethylene by mass.

5. The method for preparing an inert anode according to claim 2 or 4, characterized in that, The coating time is 20-40 minutes.

6. The method for preparing an inert anode according to claim 5, characterized in that, After coating, a draining process is required.

7. The method for preparing an inert anode according to claim 1, 4, or 6, characterized in that, The drying and curing temperature is room temperature, and the drying and curing time is 10~14 hours.

8. The inert anode prepared by the method of any one of claims 1 to 7, characterized in that, The inert anode has an air-repellent thin film coating.

9. The application of the inert anode according to claim 8 in low-temperature electrolytic aluminum.

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