Coating process of electrolytic reactor anode porous transmission layer and porous transmission layer

Abstract

The invention provides a coating process of an electrolytic reactor anode porous transmission layer and the porous transmission layer. The coating process comprises surface pretreatment, first coating treatment and second coating treatment. Wherein in the surface pretreatment, plasma cleaning and acid pickling are sequentially carried out on a porous transmission layer base material so as to respectively remove organic functional groups and an oxidation passivation layer on the surface of the porous transmission layer base material, and in the first coating treatment, a nano metal coating is deposited on the surface of the pretreated porous transmission layer base material by adopting a physical vapor deposition process; and the second coating treatment adopts a chemical plating process to grow a nanowire coating on the surface of the nano metal coating, and finally a double-layer coating structure is formed. The nano-metal coating deposited by means of the first coating treatment is used as a seed layer for growing nanowires, so that a compact, uniform and high-quality nanowire coating can be grown after the second coating treatment, and meanwhile, the interface bonding quality with the nano-metal coating is enhanced, so that the acid corrosion resistance and the oxidation resistance of the porous transmission layer are integrally improved.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis for hydrogen production technology, specifically providing a coating process for a porous transport layer of an electrolysis reactor anode and the porous transport layer itself. Background Technology

[0002] Hydrogen is currently widely used in the chemical industry, with enormous demand. However, traditional hydrogen production methods mainly rely on the processing of fossil fuels, which are high-carbon emission industries and struggle to meet carbon neutrality goals. In contrast, proton exchange membrane water electrolysis (PEMWE) offers significant advantages such as cleanliness, high efficiency, high hydrogen purity, and rapid dynamic response. By coupling with green and clean energy sources such as solar and wind power, PEMWE is expected to play a crucial role in the carbon neutrality process, addressing the mismatch between energy demand in space, time, and quantity, and promoting a green transformation of the energy structure.

[0003] However, the long-term stable operation of PEMWE stacks faces severe challenges, particularly issues related to interfacial contact resistance, internal resistance, and heat and mass transfer in multilayer stacked components. These problems can lead to a significant decrease in hydrogen production efficiency through electrolysis and a shortened stack lifespan. On the anode side, the oxygen evolution reaction (OER) generates oxygen, while the highly acidic environment of the electrolyte places extremely high demands on the oxidation and corrosion resistance of the porous transport layer (PTL). Specifically, corrosion and oxidation of the PTL material increase its resistance and interfacial contact resistance, and reduce the efficiency of water vapor and thermal management, thus severely affecting the performance and durability of PEMWE. Therefore, developing PTL materials with excellent corrosion resistance, high conductivity, and efficient water vapor management capabilities has become a current research focus.

[0004] Among numerous metallic materials, titanium (Ti) has become the preferred material for PTLs due to its outstanding corrosion resistance and relatively low cost. However, a passivation oxide layer easily forms on the surface of titanium, which increases interfacial contact resistance and poses a risk of corrosion during long-term operation. This leads to decreased conductivity and weakened interfacial electron transport capacity, thereby reducing the hydrogen production performance of PEMWE stacks and hindering the further development of PEMWE technology. Summary of the Invention

[0005] The purpose of this invention is to solve the problem of insufficient corrosion resistance and conductivity of the porous transport layer of the anode in existing electrolytic reactors during long-term operation.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] This invention provides a coating process for a porous transport layer of an electrolytic reactor anode, comprising: surface pretreatment: sequentially performing plasma cleaning and acid pickling on the porous transport layer substrate to remove organic functional groups and an oxide passivation layer from the surface of the porous transport layer substrate, respectively; first coating treatment: depositing a nano-metal coating on the surface of the pretreated porous transport layer substrate using a physical vapor deposition process; and second coating treatment: growing a nanowire coating on the surface of the nano-metal coating using a chemical plating process, ultimately forming a double-layer coating structure.

[0008] Preferably, in the surface pretreatment, a plasma cleaning instrument is used to clean the surface of the porous transport layer substrate. The plasma cleaning instrument has a power of 300W-600W, uses Ar as the ionized gas, a gas flow rate of 200sccm-500sccm, and a vacuum degree of 10. -4 Pa-10 -5 Pa, cleaning time is 400s-600s, cleaning temperature is 25℃-60℃.

[0009] Preferably, in the surface pretreatment, oxalic acid, citric acid or hydrochloric acid is used to pickle the surface of the porous transport layer substrate, the pickling temperature is 25℃-80℃ and the pickling time is 30min-60min.

[0010] Preferably, ultrasonic cleaning is added during the pickling process, and the pickling time is 10-20 minutes.

[0011] Preferably, a magnetron sputtering coating machine is used in the first coating process. In the magnetron sputtering coating machine, the distance between the target and the porous transport layer substrate is 50mm-100mm, the sputtering current is 20mA-50mA, the sputtering time is 1min-10min, and the cavity vacuum degree is 10. -3 Pa-10 -2 Pa.

[0012] Preferably, the target material is Au or Pt.

[0013] Preferably, in the second coating process, the porous transport layer substrate is immersed in a chemical nanowire coating solution, wherein the chemical nanowire coating solution comprises chloroplatinic acid, formic acid and water, and the volume ratio of the three is 1:(5-7):(100-200).

[0014] Preferably, the immersion time in the second coating process is 24h-96h.

[0015] Preferably, the thickness of the nano-metal coating is 0.5nm-1.5nm.

[0016] Preferably, the thickness of the nanowire coating is 50nm-200nm.

[0017] Preferably, the diameter of the nanowires in the nanowire coating ranges from 1 nm to 5 nm.

[0018] Preferably, the total metal loading in the double-layer coating structure is 0.34 mg / cm³. 2 -0.82mg / cm 2 .

[0019] Preferably, the porosity of the porous transport layer substrate ranges from 20% to 80%.

[0020] Based on the same inventive concept, the present invention also provides a porous transport layer, which is prepared by the coating process of the aforementioned porous transport layer of the electrolytic reactor anode.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] This invention provides a coating process for a porous transport layer in an electrolytic reactor anode, comprising surface pretreatment, a first coating treatment, and a second coating treatment. The surface pretreatment involves sequentially performing plasma cleaning and acid pickling on the porous transport layer substrate to remove organic functional groups and the oxide passivation layer from its surface, respectively. The first coating treatment uses physical vapor deposition to deposit a nano-metal coating on the pretreated surface of the porous transport layer substrate. The second coating treatment uses chemical plating to grow a nanowire coating on the surface of the nano-metal coating, ultimately forming a double-layer coating structure. The surface pretreatment of the porous transport layer substrate exposes a pure metal surface, providing a high adhesion and good conductivity foundation for subsequent coatings. The nano-noble metal coating deposited in the first coating treatment serves as a "seed" layer for nanowire growth. This noble metal "seed" layer exhibits excellent chemical stability, is not easily corroded even in strong oxidizing or acidic environments, and its nanoscale structure provides a larger specific surface area and better adhesion, further improving electron transport efficiency. PVD allows for uniform distribution on the surface, enabling the growth of a dense, uniform, and high-quality nanowire coating after the second coating treatment. This nanowire coating is a three-dimensional network protective layer with strong shielding properties and complex pathways, making it resistant even to corrosive media (such as H₂O). + Even if O2 or other substances penetrate, it is difficult to penetrate the entire porous layer; the nanowire structure can provide multi-point contact and fast electron channels, further optimizing current distribution and reducing resistance; the nanostructure has strong stress release capability and can maintain good structural integrity in thermal / electrical cycling, reducing the risk of peeling and breakage under optimized loading conditions, thereby improving the overall acid corrosion resistance and oxidation resistance of the porous transport layer, while having a larger and more stable contact with the catalyst layer and bipolar plate, thereby reducing interfacial contact resistance. Attached Figure Description

[0023] Figure 1This is a flowchart of the main steps of the coating process for the porous transport layer of the electrolytic reactor anode in this invention;

[0024] Figure 2 This is a detailed flow chart of the coating process for the porous transport layer of the electrolytic reactor anode in this invention;

[0025] Figure 3 These are low-magnification SEM images of the titanium felt surfaces prepared in Examples 1, 3, and Comparative Example 2 of the present invention.

[0026] Figure 4 High-magnification SEM images of the titanium felt surface prepared in Examples 1 and 3 of this invention;

[0027] Figure 5 Low-magnification SEM images of the titanium felt surface prepared in Examples 2 and 4 of this invention;

[0028] Figure 6 High-magnification SEM images of the titanium felt surfaces prepared in Examples 2 and 4 of this invention. Detailed Implementation

[0029] To enable those skilled in the art to better understand the technical solutions of the present invention, the preferred embodiments of the present invention are described below in conjunction with specific applications. Obviously, the described embodiments are merely a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0030] Unless otherwise specified, the experimental or testing methods described in the following examples are conventional methods; the reagents and materials described are obtained from conventional commercial sources or prepared using conventional methods, unless otherwise specified.

[0031] like Figure 1 As shown, the present invention also provides a coating process for an anode porous transport layer, comprising the following main steps:

[0032] S1 Surface pretreatment: The porous transport layer substrate is subjected to plasma cleaning and acid pickling in sequence to remove the organic functional groups and oxide passivation layer on the surface of the porous transport layer substrate, respectively.

[0033] S2 First coating treatment: A nano-metal coating is deposited on the surface of the pretreated porous transport layer substrate using a physical vapor deposition process.

[0034] S3 Second Coating Treatment: A nanowire coating is grown on the surface of the nano-metal coating using a chemical plating process, ultimately forming a double-layer coating structure.

[0035] Specifically, such as Figure 2As shown, in the S1 surface pretreatment step, a plasma cleaning instrument is first used to clean and remove surface organic functional groups from the porous transport layer substrate. To effectively remove the surface organic functional groups, the parameters used for the plasma cleaning instrument are as follows: the power of the plasma cleaning instrument is 300W-600W, Ar, O2, N2, or H2 is used as the ionizing gas, the gas flow rate is 200sccm-200sccm, and the vacuum degree is 10... -4 Pa-10 -5 The cleaning time is 400-600 seconds, and the cleaning temperature is 25℃-60℃. Ar is the preferred ionizing gas.

[0036] Then, the plasma-cleaned porous transport layer substrate is immersed in an acidic solution to thoroughly remove the surface oxide passivation layer. The acidic solution is any one of oxalic acid, citric acid, or hydrochloric acid, with an acid pickling temperature of 25℃-80℃ and a pickling time of 30-60 minutes. The concentration of oxalic acid or citric acid is 0.05mol / L-33mol / L, and the concentration of hydrochloric acid is 0.01mol / L-1mol / L.

[0037] When ultrasonic-assisted cleaning is used during the pickling process to save time, the pickling time is 10-20 minutes.

[0038] It should be noted that the pretreated porous transport layer substrate materials include, but are not limited to, titanium felt, pure titanium, titanium-based composite materials (including but not limited to titanium-graphite composite materials and titanium-phenolic composite materials), stainless steel, and carbon-based materials. The porous transport layer substrate structure includes, but is not limited to, multi-layer fiber structures, particle sintering structures, or 3D printed structures (including but not limited to control of porosity and surface area). The porosity of the porous transport layer substrate structure ranges from 20% to 80% to meet mass transfer and conductivity requirements. Furthermore, the effectiveness of oxide passivation layer removal is reflected by the ICR value, and the cleaning temperature is the temperature of the porous transport layer substrate during the cleaning process.

[0039] In the first coating process step S2, a PVD coating machine is used to deposit the first layer of coating on the porous transport layer substrate with the surface oxide layer removed. In the PVD coating machine, the distance between the target and the porous transport layer substrate is 50mm-100mm, the sputtering current is 20mA-50mA, the sputtering time is 1min-10min, and the cavity vacuum degree is 10. -3 Pa-10 -2 Pa. The target material is a precious metal, including but not limited to Ir, Ru, Au or Pt, with Au or Pt being preferred.

[0040] By setting the above parameters, the thickness of the nano-metal coating is controlled to be 0.5 nm-1.5 nm, and the metal loading range is 3.6 μg / cm³. 2-4.2μg / cm 2 To ensure that the nano-metal coating serves as the attachment and growth point for nanowires in the second coating process, and to prevent the formation of nanoparticles instead of nanowires, the thickness of the nano-metal coating is preferably controlled to be 1 nm.

[0041] In the second coating process step S3, a chemical plating solution for Pt nanowires is prepared and used to deposit a nanowire coating on the surface of the porous transport layer substrate after the first coating process.

[0042] The chemical plating solution consists of chloroplatinic acid, formic acid, and water, with a volume ratio ranging from 1:(5-7):(100-200).

[0043] A porous transport layer substrate with a nano-metal coating was immersed in a chemical plating solution for 24-96 hours to allow for sufficient growth of the nanowire coating. After immersion, a double-layer coating structure was finally formed on the surface of the porous transport layer substrate.

[0044] After this step, the nanowire coating thickness ranges from 50 nm to 200 nm, the nanowire diameter ranges from 1 nm to 5 nm, and the metal loading ranges from 0.344 mg / cm². 2 -0.81mg / cm 2 Ultimately, the total metal loading in the double-layer coating structure was 0.3482 mg / cm³. 2 -0.8136 mg / cm 2 .

[0045] Furthermore, by precisely controlling the process parameters of the S2 first coating treatment, the nano-metal coating is ensured to be uniformly distributed on the surface of the titanium-based porous transport layer and to form a strong and robust interfacial bond with the substrate, thereby endowing the material with long-lasting corrosion and oxidation resistance. The dual-layer coating structure design maintains excellent protective performance while reducing the demand for precious metals, significantly decreasing precious metal consumption and effectively controlling material preparation costs. This dual-layer coating structure not only significantly improves the corrosion and oxidation resistance of the porous transport layer but also maintains its high electrical conductivity and excellent water vapor transport performance.

[0046] Finally, the porous transport layer substrate samples prepared by the above coating process were characterized in terms of properties such as microstructure, contact resistance, corrosion potential, and corrosion current.

[0047] Examples 1-4 and Comparative Examples 1-3

[0048] Examples 1-4 of this invention use coating process parameters within different ranges as described above. In Examples 1-4 and Comparative Examples 1-3, titanium felt is used. The titanium felt has a metal purity of 99.8%, a thickness of 250 μm, and an area of ​​2.5 × 2.5 cm. 2 The porosity is 56%. The difference between Comparative Example 1 and Examples 1-4 is that Comparative Example 1 underwent only surface pretreatment, Comparative Example 2 underwent only surface pretreatment and PVD coating, and Comparative Example 3 was a commercial titanium felt prepared using Bekaert's electroplating method, with Pt electroplating and a coating thickness of 200 nm.

[0049] Table 1

[0050]

[0051]

[0052] Test Results

[0053] Table 2

[0054]

[0055]

[0056] Table 2 is a comparison table of coating materials, thicknesses, and loads for Examples 1-4 and Comparative Examples 1-3.

[0057] The microstructure and electrochemical performance of the coating process samples prepared in Examples 1-4 and Comparative Examples 1-3 were characterized.

[0058] like Figure 3 As shown, by comparing the surface morphology of Example 1 (Pt+Pt), Example 3 (Au+P) and Comparative Example 2 (single-layer Pt coating), it can be observed that a single Ti fiber and its surface coating are observed. The surface structure of Comparative Example 2 is dense and uniform, while the nanowire coatings of Examples 1 and 3 have a lower Pt loading (double-layer coating) and their surfaces also show better density.

[0059] Further observation at higher magnification reveals, for example Figure 4 As shown, the surfaces of Examples 1 and 3 exhibit typical chemical plating characteristics, namely, the formation of nanowire structures on the surface of microparticles, which are uniformly and densely distributed, and the nanowire growth quality is high.

[0060] like Figure 5As shown, Examples 2 and 4 correspond to Examples 1 and 3 respectively and have higher Pt loading. Under low magnification observation, their coatings still adhere well to the fibers. The larger gaps on them can form air chamber structures, which effectively prevent the Ti fiber surface from contacting the liquid and have the potential for corrosion resistance.

[0061] At higher magnifications, such as Figure 6 As shown, its surface also exhibits a nanowire structure, further illustrating that dense and uniform nanowires can be grown through the nanometal coating (noble metal layer) treated in the first coating process.

[0062] Table 3 is a comparison table of the contact resistance, corrosion voltage, and corrosion current results of samples from Examples 1-4 and Comparative Examples 1-3.

[0063] Table 3

[0064]

[0065]

[0066] Corrosion resistance is determined by the corrosion voltage value. A higher corrosion voltage indicates that the sample is less prone to corrosion, and vice versa. Table 3 shows that, except for Example 3, all samples with double-layer coatings exhibited increased corrosion voltages compared to Comparative Examples 1, 2, and 3. Among them, Pt+Pt double-layer coatings in Examples 1 and 2 showed better corrosion resistance. corr The values ​​were 0.97V and 1.01V, respectively. Example 4, with an Au+Pt bilayer, exhibited excellent corrosion resistance (0.90V) at a higher Pt loading, but it was still lower than that of Examples 1 and 2. This indicates that Pt plays a more important role in improving corrosion resistance than Au. It also shows that the Au+Pt coating has higher corrosion resistance (0.90V) at a high Pt loading (Example 4), while the corrosion resistance is relatively poor at a low Pt loading (Example 3), with a value of only 0.23V.

[0067] Comparative Example 1, lacking a coating, achieved a maximum ICR of 3.32 mΩ / cm at 4 MPa. 2 Comparative Example 3 (commercial coating) achieved the second highest resistance at 0.83 mΩ / cm. 2 Comparative Example 2 has the lowest ICR of 0.48 mΩ / cm. 2 However, its corrosion resistance is poor (0.73V), compared to Comparative Example 3 (0.83mΩ / cm). 2 In Examples 1-4, the ICR@4MPa of all double-layer coatings was significantly reduced to 0.62 mΩ / cm², 0.64 mΩ / cm², and 0.74 mΩ / cm², respectively. 2and 0.54mΩ / cm 2 Example 3: Although the low Pt loading of Au+Pt results in a low ICR@4MPa (0.74mΩ / cm),... 2 However, its corrosion resistance is poor, only 0.23V. In summary, compared to commercial coatings and self-made PVD coatings, the double-layer coating exhibits the best corrosion resistance at a lower Pt loading (Example 1), while maintaining a relatively low ICR@4MPa value. The best results are achieved when both the first and second layers are Pt.

[0068] Example 6

[0069] Based on the same inventive concept, embodiments of the present invention also provide a porous transport layer, including the porous transport layer prepared in Examples 1-4.

[0070] The porous transport layer for the electrolytic reactor anode, prepared using Examples 1-4, features a specific flow channel design and is assembled into the electrolytic reactor electrode plate. One side of the layer is in direct contact with the membrane electrode anode or its microporous layer, while the other side is connected to the flow channel of the anode bipolar plate. The porous transport layer matrix material performs electron and heat conduction functions in this process, while its porous structure facilitates the transport of water vapor through the flow channel to the membrane electrode anode catalytic layer, while simultaneously releasing oxygen generated by the catalytic reaction.

[0071] Because of the high specific surface area of ​​the nanowire structure, effective contact between the surface and the bipolar plates and catalyst layer can be achieved, thereby having and maintaining a low interfacial resistance. This effectively reduces the overall ohmic polarization voltage loss of the stack, thereby reducing the power loss in the process of hydrogen production by water electrolysis, preventing local high current, reducing the probability of passivation and corrosion, and thus significantly improving the hydrogen production efficiency and service life of the electrolysis stack.

[0072] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of the claims of the present invention pending approval.

Claims

1. A coating process for a porous transport layer of an electrolytic reactor anode, characterized in that, include: Surface pretreatment: The porous transport layer substrate is subjected to plasma cleaning and acid pickling in sequence to remove the organic functional groups and oxide passivation layer on the surface of the porous transport layer substrate, respectively. First coating treatment: A nano-metal coating is deposited on the surface of the pretreated porous transport layer substrate using a physical vapor deposition process; Second coating treatment: A nanowire coating is grown on the surface of the nano-metal coating using a chemical plating process, ultimately forming a double-layer coating structure.

2. The coating process for the porous transport layer of the electrolytic reactor anode according to claim 1, characterized in that, In the surface pretreatment, a plasma cleaning instrument is used to clean the surface of the porous transport layer substrate. The plasma cleaning instrument has a power of 300W-600W, uses Ar as the ionized gas, a gas flow rate of 200sccm-500sccm, and a vacuum degree of 10. -4 Pa-10 -5 Pa, cleaning time is 400s-600s, cleaning temperature is 25℃-60℃.

3. The coating process for the porous transport layer of the electrolytic reactor anode according to claim 1, characterized in that, In the surface pretreatment, oxalic acid, citric acid or hydrochloric acid is used to pickle the surface of the porous transport layer substrate. The pickling temperature is 25℃-80℃ and the pickling time is 30min-60min.

4. The coating process for the porous transport layer of the electrolytic reactor anode according to claim 3, characterized in that, Ultrasonic cleaning is added during the pickling process, and the pickling time is 10-20 minutes.

5. The coating process for the porous transport layer of the electrolytic reactor anode according to claim 1, characterized in that, In the first coating process, a magnetron sputtering coating machine is used. The distance between the target and the porous transport layer substrate in the magnetron sputtering coating machine is 50mm-100mm, the sputtering current is 20mA-50mA, the sputtering time is 1min-10min, and the cavity vacuum degree is 10. -3 Pa-10 - 2 Pa.

6. The coating process for the porous transport layer of the electrolytic reactor anode according to claim 5, characterized in that, The target material is Au or Pt.

7. The coating process for the porous transport layer of the electrolytic reactor anode according to claim 1, characterized in that, In the second coating process, the porous transport layer substrate is immersed in a chemical nanowire coating solution, which includes chloroplatinic acid, formic acid and water, with a volume ratio of 1:(5-7):(100-200).

8. The coating process for the porous transport layer of the electrolytic reactor anode according to claim 7, characterized in that, The immersion time in the second coating treatment is 24h-96h.

9. The coating process for the porous transport layer of the electrolytic reactor anode according to claim 1, characterized in that, The thickness of the nano-metal coating is 0.5nm-1.5nm.

10. The coating process for the porous transport layer of the electrolytic reactor anode according to claim 1, characterized in that, The thickness of the nanowire coating is 50nm-200nm.

11. The coating process for the porous transport layer of the electrolytic reactor anode according to claim 10, characterized in that, The diameter of the nanowires in the nanowire coating ranges from 1 nm to 5 nm.

12. The coating process for the porous transport layer of the electrolytic reactor anode according to claim 1, characterized in that, The total metal loading in the double-layer coating structure is 0.34 mg / cm³. 2 -0.82mg / cm 2 .

13. The coating process for the porous transport layer of the electrolytic reactor anode according to claim 1, characterized in that, The porosity of the porous transport layer substrate ranges from 20% to 80%.

14. A porous transport layer, characterized in that, It is prepared by the coating process of the porous transport layer of the electrolytic reactor anode according to any one of claims 1-13.

Images