Repeated regeneration electrode structure and repeated regeneration method for electrode net of alkaline electrolytic cell

Abstract

The invention relates to the technical field of water electrolysis hydrogen production, and discloses an alkaline electrolytic cell electrode net repeated regeneration electrode structure and a repeated regeneration method, and the specific method comprises the following steps: S1, ultrasonic treatment; s2, gradient pickling treatment: first pickling with a concentrated acid solution, then pickling with a weak acid solution for the second time, and finally cleaning with deionized water; s3, sand blasting treatment is conducted, specifically, 100-200-mesh sand grains are adopted for the side, provided with a catalytic layer, of an original alkaline electrolytic cell electrode net; 50-100-mesh coarse sand is adopted for the non-catalytic layer side of an original alkaline electrolytic cell electrode net; s4, coating a catalytic layer: spraying the catalytic layer on the catalytic layer side of the original alkaline electrolytic cell electrode net, wherein the content of Ni is greater than or equal to 80%; a catalyst layer with the Ni content of 60-80% is sprayed on the non-catalyst-layer side of the original alkaline electrolytic cell electrode net; the catalytic activity of the two sides of the electrode net is less than or equal to 15%; and S5, activating treatment. According to the invention, repeated utilization of the electrode net is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen production by electrolyzing water, and particularly relates to a structure and a method for repeatedly regenerating an electrode network of an alkaline electrolyzer and a method for repeatedly regenerating the electrode network. Background Art

[0002] In recent years, the green hydrogen industry has developed rapidly, and the usage of alkaline electrolyzers has increased rapidly. Generally, the designed service life of an alkaline electrolyzer is 10 - 20 years. With the development of the industry, in the next few years, a large number of electrolyzers will be phased out due to reasons such as the expiration of the designed service life of the alkaline electrolyzer and the decline in performance. Taking a 1000 Nm³ electrolyzer as an example, the weight of the electrode network (including the cathode and anode) is 2 - 3 tons. The electrode network is usually made of metals such as nickel, molybdenum, and aluminum, and has a high value. Since the electrode network is made of nickel-based material, it will not corrode in alkaline solution for a long time, and there is a possibility of reuse. Currently, after the electrode network reaches the end of its life, it is recycled as scrap metal, and the recovery rate of nickel-based materials is less than 70%, resulting in waste of resources; there are metal deposits such as Fe and Ca (content 0.5 - 3%) on the surface of the retired electrode, which directly affects the performance of the regenerated electrode; single cleaning treatment cannot restore the activity of the electrode network. Summary of the Invention

[0003] Object of the Invention: Aiming at the problems existing in the prior art, the present invention provides a structure and a method for repeatedly regenerating an electrode network of an alkaline electrolyzer and a method for repeatedly regenerating the electrode network. Through multiple methods such as deep cleaning, surface reconstruction, and construction of a double-sided catalytic layer, the reuse of the electrode network is realized.

[0004] Technical Solution: The present invention provides a method for repeatedly regenerating an electrode network of an alkaline electrolyzer, including the following steps: S1. Ultrasonic treatment; S2. Gradient pickling treatment: First, pickle with an acid solution of 0.5 - 0.6 mol / L for the first time, then pickle with an acid solution of 0.1 - 0.2 mol / L for the second time, and finally wash with deionized water; S3. Sandblasting treatment: Denote the side of the original electrode network of the alkaline electrolyzer with a catalytic layer as side A, and use 100 - 200 mesh sand grains for side A; Denote the side of the original electrode network of the alkaline electrolyzer without a catalytic layer as side B, and use 50 - 100 mesh coarse sand for side B; S4. Coating the catalytic layer: Spray different catalytic layers on both sides of the electrode network obtained in S3: The Ni content of the catalytic layer sprayed on side A is > 80%; The Ni content of the catalytic layer sprayed on side B is 60 - 80%; The catalytic activity on both sides of the electrode network is ≤ 15%; S5. Activation treatment: Apply a pulsed current in a KOH + Na₂S·9H₂O activation solution to activate the electrode network obtained in S4.

[0005] Further, in S1, the specific conditions for the ultrasonic treatment are as follows: the ultrasonic frequency is 20 - 40 kHz, the power density is 0.5 - 1.5 W / cm², and the ultrasonic cleaning solution is deionized water added with 0.1% sodium dodecyl sulfate.

[0006] Perform ultrasonic cleaning to remove the alkali solution precipitate and other impurities on the surface of the scrapped electrode, and at the same time remove the catalyst coating that is not firmly bonded.

[0007] Further, in S2, for the first pickling: the pickling time is 3 - 30 min, the pickling temperature is 20 - 50 °C, and the acid concentration is 0.5 mol / L; for the second pickling: the pickling time is 10 - 60 min, and the acid concentration is 0.2 mol / L.

[0008] The present invention adopts a three-step gradient pickling method. In the first step, strong acid is used to mainly remove impurities such as Fe, Cr, and Ca on the electrode surface (cathodic electrochemical precipitation caused by long-term operation of the electrolytic cell). In the second step, weak acid is used. In an acidic environment, the activity of Al element is higher than that of nickel. In a weak acid environment, Al preferably reacts with H⁺. Considering the layered structure characteristics of the catalyst layer, using weak acid can remove elements such as Al inside the electrode without corroding the electrode mesh, thereby increasing stability. In the third step, deionized water is used for further cleaning.

[0009] Further, in S3, the angle of the sandblasting is 30 - 60°.

[0010] Usually, the catalyst is made on one side of the electrode mesh. Therefore, in the scrapped electrode mesh, one side has a catalyst layer, denoted as side A; the other side does not have a catalyst layer, denoted as side B; since side A originally had a catalyst layer, its original roughness is better, and 100 - 200 mesh sand grains are used for sandblasting treatment; side B has a smooth substrate, and 50 - 100 mesh coarse sand is used for sandblasting treatment.

[0011] Further, in S4, the catalyst layer on side A is a NiAl layer; the catalyst layer on side B is NiFeMoAl, NiFeAl, NiMoAl, etc.; the ratio of the thickness of the catalyst layer on side A to the thickness of the catalyst layer on side B is 1∶1.2 - 1.5.

[0012] The present invention makes different performance coatings on both sides: (a) After treatment, a catalyst coating is made again on side A. Since side A originally had a catalyst layer, its original roughness is better. Therefore, its high specific surface area is fully utilized to make a coating with a high nickel content, mainly to increase the bonding force; (b) A catalyst coating with high catalytic performance is made on side B to mainly increase the electrode performance.

[0013] The difference in double-sided catalytic activity is ≤15%. When simulating the intermittent current impact during green electricity-based hydrogen production, the electrode decay is ≤5%. During the electrolysis process, the potentials on both sides of side A and side B can be kept close as much as possible to avoid the "galvanic cell" effect caused by excessive potential difference, which may lead to the shedding of the coating after the generation of internal stress, thus increasing the electrode stability.

[0014] Further, in S5, the activation liquid is specifically 6M KOH + 0.1M Na2S·9H2O.

[0015] Further, the specific conditions of the pulsed current are as follows: the current density is 1-3 A / cm², the pulse frequency is 100-500 Hz, and the duty cycle is 30-70%.

[0016] Preferably, the specific conditions for activation are: the activation temperature is 50-80 °C; the activation time is 20-30 min.

[0017] By adopting the activation combined with the pulsed current technology, the operating conditions of the electrode in the alkaline electrolytic cell are simulated, deep de-aluminum pore formation is achieved, the activation effect of aluminum extraction pore formation is increased, the surface of the electrode is modified to increase the specific surface area, and the electrode stability is increased.

[0018] The present invention also provides a structure of a repeatedly regenerated electrode of an alkaline electrolytic cell electrode mesh prepared by the method described in any one of the above.

[0019] Beneficial effects: Compared with the prior art, the present invention realizes the reuse of the electrode mesh through multiple ways of deep cleaning, surface reconstruction, and the construction of a double-sided catalytic layer. The specific beneficial effects are as follows: (1) Cost reduction: Compared with the preparation of new electrodes, the cost of regenerating waste electrode meshes is only 40% of that of preparing new electrodes; (2) Environmental benefits: Through the regeneration treatment of waste electrode meshes, the utilization rate of nickel resources is increased to over 92%, and the CO2 emissions per ton of regenerated electrodes are reduced by 3.2 tons.

[0020] (3) Extended lifespan: After long-term current impact, the coating of the regenerated electrode does not fall off and the performance does not significantly decay, and the stability of the regenerated electrode mesh is stronger.

[0021] (4) Lower overpotential: The overpotential of the regenerated electrode is reduced and the catalytic activity is stronger. Description of the Drawings Figure 1 It is the LSV diagram of the electrode mesh catalytic layer at different current densities in the present invention; Figure 2 It is the hydrogen evolution overpotential test diagram of the repeatedly regenerated electrode of the alkaline electrolytic cell electrode mesh and the original electrode prepared in the present invention. Among them, the green line is the hydrogen evolution overpotential of the original electrode; the purple line is the hydrogen evolution overpotential of the repeatedly regenerated electrode of the alkaline electrolytic cell electrode mesh prepared in the present invention; Figure 3 The cyclic curve diagram of the recycled electrodes of the alkaline electrolyzer electrode mesh prepared in the present invention; Figure 4 SEM diagrams of side A (a) and side B (b) of the recycled electrodes of the alkaline electrolyzer electrode mesh prepared in the present invention after long-time current shock. Specific embodiments

[0022] The present invention will be introduced in detail below in conjunction with the embodiments.

[0023] Embodiment 1: This embodiment provides a method for recycling 1000 Nm³ / h of waste alkaline electrolyzer electrode mesh, which is as follows: (1) Ultrasonic treatment: The 1000 Nm³ / h of waste alkaline electrolyzer electrode mesh is ultrasonically treated with a 40 kHz variable-frequency ultrasound and a power density of 0.5 W / cm 2 , and the ultrasonic cleaning solution is deionized water added with 0.1% sodium dodecyl sulfonate; (2) Pickling process: First, pickling treatment is carried out with 0.5 mol / L HCl for 20 min at a pickling temperature of 25°C; then pickling treatment is carried out with 0.2 mol / L HCl for 60 min; finally, it is cleaned with deionized water; (3) Sandblasting treatment: Sandblasting treatment is carried out on the side of the waste alkaline electrolyzer electrode mesh with a catalytic layer using 150-mesh alumina sand grains at a pressure of 0.3 MPa; sandblasting treatment is carried out on the side of the waste alkaline electrolyzer electrode mesh without a catalytic layer using 80-mesh silicon carbide sand grains; the sandblasting angles on both sides are 60°; (4) Preparation of the catalytic layer: The catalytic layer NiAl composite powder is sprayed on the side of the waste alkaline electrolyzer electrode mesh with a catalytic layer, where the Ni content > 80%; the catalytic layer NiFeMoAl composite powder is sprayed on the side of the waste alkaline electrolyzer electrode mesh without a catalytic layer, where the Ni content is 60 - 80%; ensure that the catalytic activity on both sides of the electrode mesh ≤ 15%; the ratio of the thickness of the catalytic layer prepared on the side of the waste alkaline electrolyzer electrode mesh that originally had a catalytic layer to the thickness of the catalytic layer prepared on the side that originally did not have a catalytic layer is 1∶1.2 - 1.5.

[0024] Optionally, the preparation method of the double-sided catalytic layer is as follows: The first step: 99.6% pure nickel powder with a particle size of 50 - 80 microns, 99.8% pure aluminum powder with a particle size of 100 - 150 microns, and NiFeMo composite powder are respectively placed in a vacuum oven, and the oven drying temperature is 80°C for more than 16 h to remove moisture and increase fluidity.

[0025] Step 2: Spraying and manufacturing on the side with a catalytic layer of the waste alkaline electrolyzer electrode mesh: Add nickel powder and aluminum powder to a double-cone mixer at a mass ratio of 90:10, with a rotation speed of 60 rpm and a time of 8 h. Use plasma spraying to manufacture the Ni90Al10 coating, with a power of 60 KW, the main plasma gas being argon with a flow rate of 4000 L / h, the secondary gas being hydrogen with a flow rate of 1200 L / h, the powder feeding rate being 180 g / min, the carrier gas being nitrogen with a pressure of 0.02 Mpa and a flow rate of 15 NLPM, the gun distance being 190 mm, the purging gas being nitrogen with a pressure of 0.8 Mpa and a flow rate of 150 m3 / h, and the gun traversing speed being 2 m / s, and the coating thickness being 30 - 50 μm.

[0026] Step 3: Spraying and manufacturing on the side without a catalytic layer of the waste alkaline electrolyzer electrode mesh: Here, according to actual production needs, single-layer catalytic layer spraying or multi-layer catalytic layer spraying can be carried out: For example, in single-layer catalytic layer spraying, mix Ni powder, Fe powder, Mo powder, and Al powder at a mass ratio of 65:20:10:5, and the remaining steps are carried out in the same manner as in Step 2 above, with a coating thickness of 36 - 75 μm; in double-layer catalytic layer spraying, according to the spraying parameters in Step 2 above, the bottom layer is sprayed with a Ni65Fe25Mo10 doped with 5% Al coating, and the top layer is made of Ni60Fe20Mo20 doped with 8% Al material. The plasma spraying power is 42 KW, the main plasma gas is argon with a flow rate of 3200 L / h, the secondary gas is hydrogen with a flow rate of 600 L / h, the powder feeding rate is 150 g / min, the carrier gas is nitrogen with a pressure of 0.02 Mpa and a flow rate of 12 NLPM, the gun distance is 170 mm, the purging gas is nitrogen with a pressure of 0.8 Mpa and a flow rate of 150 m3 / h, and the gun traversing speed is 2 m / s, and the coating thickness is 36 - 75 μm.

[0027] (5) Activation treatment: Apply a pulsed current (duty cycle 50%) of 2 A / cm 2 in an activation solution at 70 °C for 30 min Embodiment

[0028] This embodiment is generally the same as Embodiment 1, except that in this embodiment, a catalytic layer of NiFeAl composite powder is sprayed on the side without a catalytic layer of the waste alkaline electrolyzer electrode mesh.

[0029] Except for this, this embodiment is exactly the same as Embodiment 1 and will not be elaborated here.

[0030] Embodiment 3: This embodiment is generally the same as Embodiment 1, except that in this embodiment, a catalytic layer of NiMoAl composite powder is sprayed on the side without a catalytic layer of the waste alkaline electrolyzer electrode mesh.

[0031] Except for this, this embodiment is exactly the same as Embodiment 1 and will not be elaborated here.

[0032] Performance test: Figure 1 This is the LSV diagram at different current densities of the electrode network catalytic layer in the present invention; the double-sided catalytic electrode prepared in the present invention is 3560 A / m2 @ 2.0 V. The electrode of the B-side catalytic layer is 3320 A / m2 @ 2.0 V, and the electrode of the A-side catalytic layer is 3290 A / m2 @ 2.0 V.

[0033] Figure 2 This is the hydrogen evolution overpotential test diagram of the repeated regeneration electrode and the original electrode of the electrode network of the alkaline electrolyzer prepared in the present invention. Among them, the green line is the hydrogen evolution overpotential of the original electrode; the purple line is the hydrogen evolution overpotential of the repeated regeneration electrode of the electrode network of the alkaline electrolyzer prepared in the present invention; the repeated regeneration electrode of the electrode network of the alkaline electrolyzer prepared in the present invention is -0.5 V @ -6000 A / m 2 , and the original electrode is -0.52 @ -6000 A / m 2 .

[0034] Figure 3 This is the cyclic curve diagram of the repeated regeneration electrode of the electrode network of the alkaline electrolyzer prepared in the present invention: the influence of the fluctuating voltage impact on the electrode, and the electrode attenuation is <2% after 100 cycles; Figure 4 This is the SEM diagram of the A-side (a) and B-side (b) of the repeated regeneration electrode of the electrode network of the alkaline electrolyzer prepared in the present invention after long-term current impact.

[0035] The above embodiments are only for illustrating the technical concept and characteristics of the present invention, and the purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. All equivalent transformations or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for repeated regeneration of an electrode mesh of an alkaline electrolyzer, characterized in that, It includes the following steps: S1. Ultrasonic treatment; S2. Gradient pickling treatment: First, pickle with an acid solution of 0.5 - 0.6 mol / L for the first time, then pickle with an acid solution of 0.1 - 0.2 mol / L for the second time, and finally wash with deionized water; S3. Sandblasting treatment: Denote the side of the original alkaline electrolyzer electrode mesh with a catalytic layer as side A, and use 100 - 200 mesh sand grains for side A; Denote the side of the original alkaline electrolyzer electrode mesh without a catalytic layer as side B, and use 50 - 100 mesh coarse sand for side B; S4. Coating the catalytic layer: Spray different catalytic layers on both sides of the electrode mesh obtained in S3: The Ni content in the catalytic layer sprayed on side A > 80%; The Ni content in the catalytic layer sprayed on side B is 60 - 80%; The catalytic activity on both sides of the electrode mesh ≤ 15%; S5. Activation treatment: Apply a pulsed current in a KOH + Na2S·9H2O activation solution to activate the electrode mesh obtained in S4.

2. The method for repeatedly regenerating the electrode mesh of an alkaline electrolyzer according to claim 1, wherein: In S1, the specific conditions of the ultrasonic treatment are: The ultrasonic frequency is 20 - 40 kHz, the power density is 0.5 - 1.5 W / cm², and the ultrasonic cleaning solution is deionized water added with 0.1% sodium dodecyl sulfonate.

3. The method for repeatedly regenerating the electrode mesh of an alkaline electrolyzer according to claim 1, characterized in that: In S2, for the first pickling: The pickling time is 3 - 30 min, the pickling temperature is 20 - 50 °C, and the acid concentration is 0.5 mol / L; For the second pickling: The pickling time is 10 - 60 min, and the acid concentration is 0.2 mol / L.

4. The method for repeatedly regenerating the electrode mesh of an alkaline electrolyzer according to claim 1, characterized in that: In S3, the angle of the sandblasting is 30 - 60°.

5. The method for repeatedly regenerating the electrode mesh of an alkaline electrolyzer according to claim 1, wherein: In S4, the catalytic layer on side A is a NiAl layer; The catalytic layers on side B are NiFeMoAl, NiFeAl, NiMoAl, etc.; The ratio of the thickness of the catalytic layer on side A to the thickness of the catalytic layer on side B is 1∶1.2 - 1.

5.

6. The method for repeatedly regenerating the electrode mesh of an alkaline electrolyzer according to claim 1, characterized in that: In S5, the activation solution is specifically 6M KOH + 0.1M Na2S·9H2O.

7. The method for repeatedly regenerating the electrode mesh of an alkaline electrolyzer according to claim 1, characterized in that: The specific conditions of the pulsed current are: The current density is 1 - 3 A / cm², the pulse frequency is 100 - 500 Hz, and the duty cycle is 30 - 70%.

8. The method for repeatedly regenerating the electrode mesh of an alkaline electrolyzer according to claim 1, characterized in that: The specific conditions of the activation are: The activation temperature is 50 - 80 °C; The activation time is 20 - 30 min.

9. The alkaline electrolyzer electrode mesh repeating regeneration electrode structure prepared by the method according to any one of claims 1 - 8.

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