A method of making a modified porous titanium-based current collector

Abstract

The application belongs to the technical field of proton exchange membrane water electrolysis cell, and discloses a method for preparing a modified porous titanium-based current collector. The method specifically comprises the following steps: performing organic solvent oil removal and acid treatment on a titanium substrate, then cleaning the titanium substrate with deionized water, and drying; performing constant potential electrochemical nitriding treatment on the treated titanium substrate to form a nitriding film on the surface of the titanium substrate, thereby obtaining a modified porous titanium-based current collector. The application has the beneficial effect that: after the constant potential electrochemical nitriding in the acid nitrate solution, the method of the application forms a dense and uniform conductive coating on the surface of the titanium felt, thereby improving the corrosion resistance and conductivity of the titanium felt. The application has excellent conductivity and corrosion resistance, and has a broad application prospect for the durability of future proton exchange membrane electrolysis cell current collectors.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of proton exchange membrane water electrolysis cell, and particularly relates to a method for preparing a modified porous titanium-based current collector. BACKGROUND

[0002] The porous diffusion layer, as one of the key components in the PEM water electrolysis hydrogen production device, has a great influence on the operation life, cost and wide range application of the device. Metal materials have excellent electric and thermal conductivity, large power density, good gas resistance, high mechanical strength, easy processing and low production cost and the like. However, the metal materials will appear corrosion behavior in the long-term use process, and the appearance of metal ions after corrosion will hinder the migration of protons to a certain extent and will also have a certain toxic effect on the membrane electrode. At present, the metal diffusion layer, especially titanium, has been widely concerned. Their characteristics are that the entire surface is covered with a passivation oxide (hydroxide) layer. This passivation layer is very stable, adherent and highly compact, which effectively protects the metal from further oxidation. However, the proton exchange membrane water electrolysis cell operates in an acidic, high-temperature and high-pressure environment, and the titanium surface in the metal material is easy to oxidize to form a dense oxide film. The existence of the oxide film greatly hinders the corrosion behavior and improves the corrosion resistance of itself, but also increases the interface contact resistance, which will cause the ohmic loss of the entire stack. Therefore, it is difficult to achieve the demand for high corrosion resistance and low contact resistance at the same time by relying on the characteristics of the metal material itself. One method is to use corrosion-resistant and conductive materials such as titanium materials containing Nb and Ta. However, the oxide layer is formed on the surface, and the resistance increases after long-time water electrolysis; another method is to coat a layer of noble metal (Au, IrO2, Pt) by magnetron sputtering, but the application cost is high; and another method is to form a passivation film on the titanium surface by heat treatment or plasma nitrogen doping treatment. This method improves the corrosion resistance of the titanium surface by nitrogenization treatment and maintains the conductivity of the titanium surface. The heat treatment method for nitrogenization treatment is more stable, but the material has been found to be oxidized after long-time water electrolysis. The chemical nitriding treatment improves the conductivity and corrosion resistance of the substrate material, but these methods generally have the problems of complex process technology and high cost. Therefore, it is urgent to find a simple, efficient and low-cost nitrogenization treatment method to replace the traditional high-energy consumption nitriding process. SUMMARY

[0003] The main purpose of the present application is to provide a method for preparing a modified porous titanium-based current collector to overcome the deficiencies in the prior art.

[0004] The present application is realized by the following technical scheme: a method for preparing a modified porous titanium-based current collector, comprising the following steps:

[0005] S1) titanium felt pretreatment;

[0006] The titanium felt is treated with organic solvent degreasing and acid treatment to remove grease and passivation film on the surface of the titanium felt; the titanium felt is treated in a solution for 10-20 s, then washed with deionized water and dried in a vacuum oven;

[0007] S2) Preparation of a constant potential electrochemical nitriding solution;

[0008] The titanium felt electrochemical nitriding solution is composed of nitrate and acid solution, and the nitriding potential, time, area ratio and spacing of working electrode and counter electrode are controlled;

[0009] Constant potential electrochemical nitriding connection device;

[0010] The obtained titanium felt is placed in the prepared acidic nitrate solution, nitrogen is introduced, the temperature is controlled at 25-50°C, and electrochemical treatment is carried out by using a three-electrode system, in which the titanium felt is the working electrode, the platinum sheet is the counter electrode, and the saturated calomel electrode (SCE) is the reference electrode;

[0011] 4) PEW WE titanium felt diffusion layer constant potential nitriding process;

[0012] The constant potential electrochemical nitriding process is divided into three processes: the first part is to pre-treat the titanium felt by cathode for a period of time in the nitriding solution to remove the adsorbed oxygen in the air transfer process; the second part is to nitride the titanium felt for different times at a selected potential range; the third part is to rinse the nitrided titanium felt with deionized water and dry it for use.

[0013] Further, the volume ratio of acid treatment is HF:HNO3:H2O = 1:8:10, HF:HNO3:H2O = 1:10:20, and HF:HNO3:H2O = 1:10:50.

[0014] Further, the concentration of nitrate is potassium nitrate (0.1-2.0 mol / L), sodium nitrate (0.1-2.0 mol / L), preferably potassium nitrate concentration (0.3-1 mol / L), and sodium nitrate concentration (0.4-1.5 mol / L).

[0015] Further, the concentration of acid is nitric acid (0.01-1 mol / L), hydrochloric acid (0.01-0.5 mol / L), and sulfuric acid (0.01-1 mol / L), preferably nitric acid (0.05-0.2 mol / L), hydrochloric acid (0.08-0.4 mol / L), and sulfuric acid (0.04-0.1 mol / L).

[0016] Further, the distance between the working electrode and the counter electrode is 0.5-3 cm, and the area ratio of the working electrode to the counter electrode is 0.5:1, 1:1 or 1:2.

[0017] The nitrogen is introduced for 15-30 minutes.

[0018] Further, the cathode is pretreated for 20-30 minutes at a temperature of 25-50 DEG C, preferably 25-30 DEG C.

[0019] Further, the second part of the constant potential nitriding is performed at a potential of-3 to 0 V for 0.5-10 h, preferably-1.5 to-0.5 V.

[0020] The present application has the following features:

[0021] 1. In order to solve the problem of the high internal resistance of the PEM water electrolysis porous current collector caused by the oxidation of the anode at a high potential, the present application forms a high-conductivity and corrosion-resistant composite coating by constant potential electrochemical nitriding.

[0022] 2. The present application forms a dense and uniform conductive coating on the surface of the titanium felt by constant potential electrochemical nitriding in an acidic nitrate solution, thereby improving the corrosion resistance and conductivity of the titanium felt.

[0023] 3. The high-conductivity nitriding coating prepared by the present application has greatly improved corrosion resistance, and in a 0.5 mol / L H2SO4+2 ppm F - solution, the corrosion current density is 0.920·10 -6 A / cm 2 , and the conductivity is also greatly improved, and the contact resistance is 1.60 mΩ cm 2 at 140 N cm -2 .

[0024] The present application has the following advantages:

[0025] 1. The preparation process is simple and efficient, does not require special equipment, has low cost, and has wide application range.

[0026] 2. High conductivity, the contact resistance remains stable in a low range after 10 hours of polarization.

[0027] 3. Good stability under constant potential polarization at a potential of 1.7 V to 2.0 V.

[0028] 4. The improvement space is wide, and the modified porous titanium-based current collector can be obtained by introducing different types of conductive material matrix materials and different concentrations of nitrate additives and adjusting different proportions of the components to improve the metal diffusion layer to different degrees. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 SEM and EDS of pure titanium felt of example 1 using the method of the present application.

[0030] Figure 2 Morphology of electrochemical nitridation at different potentials of example 1 using the method of the present application.

[0031] Figure 3 Potentiodynamic polarization curve of example 2 using the method of the present application at different nitriding times.

[0032] Figure 4 Contact resistance test diagram of example 1 using the method of the present application at different pressures.

[0033] Figure 5 Potentiodynamic polarization curve of example 3 using the method of the present application. DETAILED DESCRIPTION

[0034] The present application will be further described in detail below in conjunction with the embodiments and drawings, but the embodiments of the present application are not limited thereto. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0035] The present application is a method for preparing a modified porous titanium-based current collector, which specifically comprises the following steps:

[0036] S1) The titanium substrate is subjected to organic solvent degreasing and acid treatment, and then washed with deionized water and dried;

[0037] S2) The titanium substrate treated in S1) is subjected to constant potential electrochemical nitriding treatment to form a nitriding coating on the surface of the titanium substrate, thereby obtaining a modified porous titanium-based current collector.

[0038] The titanium substrate in S1) is titanium felt, titanium fiber or titanium mesh;

[0039] The acid treatment time is 10-20 s; the acid treatment solution is a mixed solution of HF, HNO3 and H2O, and the volume ratio among the three is 1:8-10:20-50.

[0040] The specific steps of S2) are:

[0041] S2.1) Prepare an acidic nitriding solution for standby;

[0042] S2.2) continuously passing nitrogen into the obtained acidic nitriding solution in S2.1) to perform cathodic pretreatment;

[0043] S2.3) temperature control at 25-50℃, electrochemical treatment in a three-electrode system to obtain a modified porous titanium-based current collector for a proton exchange membrane water electrolyzer.

[0044] The acidic nitriding solution in S2.1) is a mixed solution of a nitrate solution and an acid solution;

[0045] The concentration of the nitrate in the mixed solution is 0.1-2.0 mol / L, and the concentration of the acid is 0.01-1 mol / L.

[0046] The nitrate is potassium nitrate or sodium nitrate, and the acid is nitric acid, hydrochloric acid or sulfuric acid.

[0047] The nitrogen gas in S2.2) is passed for 15-30 minutes;

[0048] The cathodic pretreatment time is 20-30 minutes, and the temperature is 25-50℃.

[0049] The titanium substrate in the three-electrode system in S2.3) is the working electrode, the platinum sheet is the counter electrode, and the saturated calomel electrode is the reference electrode.

[0050] The area ratio of the working electrode to the counter electrode is 0.5-1:1-2, and the distance between the working electrode and the counter electrode is 1-3 cm.

[0051] The nitriding potential is between -3 and 0 V, and the nitriding time is 0.5-10 h.

[0052] The area ratio of the working electrode to the counter electrode can also be 1:1, and the distance between the working electrode and the counter electrode is 1-2 cm.

[0053] The nitriding potential is between -1.5 and 0 V, and the nitriding time is 2-8 h.

[0054] A proton exchange membrane water electrolyzer, wherein the modified porous titanium-based current collector is prepared by the above method.

[0055] Example 1:

[0056] The titanium felt was ultrasonically cleaned in acetone, ethanol and deionized water to remove organic matter on the surface, then acid treated with a volume ratio (HF:HNO3:H2O =1:8:10) to remove the surface oxide film, washed with deionized water and dried for storage.

[0057] The solution composition for electrochemical nitridation of the titanium felt is potassium nitrate and nitric acid solution, the area ratio of the working electrode to the counter electrode is 1:1, the spacing is 2 cm, the concentration of potassium nitrate is 0.5 mol / L, and the concentration of nitric acid is 0.1 mol / L. The constant potential electrochemical nitridation treatment is performed at room temperature by using a three-electrode system, in which the titanium felt is the working electrode, the platinum sheet is the counter electrode, and the saturated calomel electrode (SCE) is the reference electrode. Nitrogen is introduced for 15 minutes before electrochemical nitridation, and then cathodic pretreatment is performed for 20 minutes; electrochemical nitridation is performed at different potentials, the potentials are -0.45 V, -0.85 V, -1.05 V and -1.25 V, and the nitridation time is 2 h. The treated titanium felt sample is washed with deionized water and then dried for morphology characterization and electrochemical test.

[0058] Example 2:

[0059] The titanium felt is ultrasonically cleaned in acetone, ethanol and deionized water respectively to remove the organic matter on the surface, and then is acid treated in a volume ratio (HF:HNO3:H2O =1:8:10) to remove the oxide film on the surface, and is washed with deionized water and then dried for storage.

[0060] The solution composition for electrochemical nitridation of the titanium felt is potassium nitrate and nitric acid solution, the area ratio of the working electrode to the counter electrode is 1:1, the spacing is 2 cm, the concentration of potassium nitrate is 0.5 mol / L, and the concentration of nitric acid is 0.1 mol / L. The constant potential electrochemical nitridation treatment is performed at room temperature by using a three-electrode system, in which the titanium felt is the working electrode, the platinum sheet is the counter electrode, and the saturated calomel electrode (SCE) is the reference electrode. Nitrogen is introduced for 15 minutes before electrochemical nitridation, and then cathodic pretreatment is performed for 20 minutes; electrochemical nitridation is performed at different potentials, the potentials are -0.45 V, -0.85 V, -1.05 V and -1.25 V, and the nitridation time is 2 h. The treated titanium felt sample is washed with deionized water and then dried for morphology characterization and electrochemical test.

[0061] Example 3:

[0062] The titanium felt is ultrasonically cleaned in acetone, ethanol and deionized water respectively to remove the organic matter on the surface, and then is acid treated in a volume ratio (HF:HNO3:H2O =1:8:10) to remove the oxide film on the surface, and is washed with deionized water and then dried for storage.

[0063] The solution for electrochemical nitridation of the titanium felt is composed of potassium nitrate and nitric acid solution, the area ratio of the working electrode to the counter electrode is 1:1, the distance is 2 cm, the concentration of the sodium nitrate is 0.5 mol / L, and the concentration of the nitric acid is 0.1 mol / L. The constant potential electrochemical nitridation is performed at room temperature by using a three-electrode system, in which the titanium felt is the working electrode, the platinum sheet is the counter electrode, and the saturated calomel electrode (SCE) is the reference electrode. Nitrogen is introduced for 15 minutes before the electrochemical nitridation, and then the cathodic pretreatment is performed for 20 minutes; the potential is selected as -1.05 V for nitridation for 4 h. The treated titanium felt sample is cleaned with deionized water and then dried for electrochemical test.

[0064] Example 4

[0065] The titanium felt is ultrasonically cleaned in acetone, ethanol and deionized water respectively to remove the organic matters on the surface, and then is acid treated in a volume ratio (HF:HNO3:H2O =1:8:10, HF:HNO3:H2O =1:10:20, and HF:HNO3:H2O =1:10:50) to remove the oxide film on the surface, and is cleaned with deionized water and then dried for storage.

[0066] The solution for electrochemical nitridation of the titanium felt is composed of potassium nitrate and nitric acid solution, the area ratio of the working electrode to the counter electrode is 1:1, the distance is 2 cm, the concentration of the potassium nitrate is 0.5 mol / L, and the concentration of the nitric acid is 0.1 mol / L. The constant potential electrochemical nitridation is performed at room temperature by using a three-electrode system, in which the titanium felt is the working electrode, the platinum sheet is the counter electrode, and the saturated calomel electrode (SCE) is the reference electrode. Nitrogen is introduced for 15 minutes before the electrochemical nitridation, and then the cathodic pretreatment is performed for 20 minutes; the potential is selected as -0.85 V for nitridation for 4 h for the titanium felt treated by the three different acids. The treated titanium felt sample is cleaned with deionized water and then dried for electrochemical test.

[0067] Example 5

[0068] The titanium felt is ultrasonically cleaned in acetone, ethanol and deionized water respectively to remove the organic matters on the surface, and then is acid treated in a volume ratio (HF:HNO3:H2O =1:8:10) to remove the oxide film on the surface, and is cleaned with deionized water and then dried for storage.

[0069] The solution composition of the electrochemical nitridation of titanium felt is potassium nitrate and nitric acid solution, the area ratio of working electrode to counter electrode is 0.5:1, 1:1 and 1:2 respectively, the interval is 2 cm, the concentration of sodium nitrate is 0.5 mol / L, and the concentration of nitric acid is 0.1 mol / L. At room temperature, a three-electrode system is used for constant potential electrochemical nitridation treatment, in which titanium felt is used as the working electrode, platinum sheet is used as the counter electrode, and saturated calomel electrode (SCE) is used as the reference electrode. Nitrogen is introduced for 15 minutes before electrochemical nitridation, and then cathodic pretreatment is carried out for 20 minutes; the potential is selected as-0.85 V for nitridation for 2 h. The treated titanium felt sample is washed with deionized water and dried for electrochemical test.

[0070] The above describes in detail the method for preparing the modified porous titanium-based current collector provided by the embodiments of the application. The above description of the embodiments is only used to help understand the method and its core idea of the application; meanwhile, for those skilled in the art, the specific implementation and application range can be changed according to the idea of the application; therefore, the content of the specification should not be understood as a limitation of the application.

[0071] As some terms are used in the description and claims to refer to certain components. Those skilled in the art should understand that hardware manufacturers may use different names to refer to the same component. The description and claims of the specification do not take the difference in name as a way to distinguish components, but take the difference in function of components as a criterion for distinction. As mentioned throughout the description and claims, "including" and "including" are open-ended terms, which should be interpreted as "including / including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve the technical problems within a certain error range and basically achieve the technical effects. The subsequent description in the specification is a preferred embodiment for implementing the application, and the description is for the purpose of illustrating the general principles of the application, not to limit the scope of the application. The scope of protection of the application is defined by the appended claims.

[0072] It should also be noted that the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that the products or systems including a series of elements not only include those elements, but also include other elements not explicitly listed or inherent to such products or systems. Without more limitations, the element defined by the statement "including a" does not exclude the presence of other identical elements in the product or system including the element.

[0073] It should be understood that the term "and / or" as used herein merely describes associated objects, and can exist in three forms: A and / or B, A or B, and A and B. In addition, the character " / " generally represents an "or" relationship between the front and rear associated objects.

[0074] The above description illustrates and describes several preferred embodiments of the present application, but as previously noted, it is not intended to be exhaustive or to be limited to the precise form disclosed. It is intended to cover various modifications and alternate methods, and combinations thereof, falling within the scope of the application as defined by the appended claims, and their equivalents. Changes and modifications can be made to the application in light of the above teachings. It is therefore, intended to cover any and all changes and modifications of the application in accordance with the scope of the appended claims.

Claims

1. A method of making a modified porous titanium-based current collector, characterized in that, The method specifically comprises the following steps: S1) treating a titanium substrate with organic solvent degreasing and acid treatment, then washing with deionized water and drying; The titanium substrate is a titanium felt, a titanium fiber or a titanium mesh; the acid treatment time is 10-20 s; the acid treatment solution is a mixed solution of HF, HNO3 and H2O, and the volume ratio among the three is 1:8-10:20-50; S2) treating the titanium substrate treated in S1) with constant potential electrochemical nitriding treatment to obtain a modified porous titanium-based current collector; The specific steps are: S2.1) preparing an acid nitriding solution; The acid nitriding solution is a mixed solution of a nitrate solution and an acid solution; the concentration of the nitrate in the mixed solution is 0.1-2.0 mol / L, and the concentration of the acid solution in the mixed solution is 0.01-1 mol / L; S2.2) continuously introducing nitrogen into the acid nitriding solution prepared in S2.1) for cathodic pretreatment; S2.3) controlling the temperature at 25-50℃, and performing electrochemical treatment with a three-electrode system to obtain the modified porous titanium-based current collector; In the three-electrode system in S2.3), the titanium substrate is a working electrode, a platinum sheet is a counter electrode, and a saturated calomel electrode is a reference electrode; The area ratio of the working electrode to the counter electrode is 0.5-1:1-2; the distance between the working electrode and the counter electrode is 1-3 cm; the nitriding potential is-3-0 V, and the nitriding time is 0.5-10 h.

2. The method of claim 1, wherein, The nitrate is potassium nitrate or sodium nitrate, and the acid solution is nitric acid, hydrochloric acid or sulfuric acid.

3. The method of claim 1, wherein, In S2.2), the nitrogen introduction time is 15-30 minutes; the cathodic pretreatment time is 20-30 minutes, and the temperature is 25-50℃.

4. The method of claim 1, wherein, The area ratio of the working electrode to the counter electrode can also be 1:1; the distance between the working electrode and the counter electrode is 1-2 cm; the nitriding potential is-1.5-0 V, and the nitriding time is 2-8 h.

5. A proton exchange membrane water electrolyser characterised in that, The modified porous titanium-based current collector in the proton exchange membrane water electrolyzer is prepared by the method according to any one of claims 1-4.

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