A carbon-titanium based porous transport layer deposited on a proton exchange membrane water electrolysis cathode, its preparation method and application

Abstract

This invention discloses a carbon-titanium-based porous transport layer for proton exchange membrane (PEM) water electrolysis cathode, its preparation method, and its application, belonging to the field of PEM water electrolysis technology. The invention involves sequentially depositing a Ti transition layer and a Cr-Zr-Nb ternary doped amorphous carbon layer on the surface of a titanium-based porous substrate, followed by heat treatment in a nitrogen-containing atmosphere. The Ti transition layer enhances the adhesion between the coating and the substrate, while the synergistic effect of the Cr-Zr-Nb ternary doped amorphous carbon layer improves the coating's density and corrosion resistance. The nitride nanoparticles generated through post-treatment nitriding further strengthen the coating's barrier properties, effectively inhibiting surface oxidation and Ti ion dissolution of the cathode titanium-based porous transport layer, preventing cathode catalyst poisoning, and extending the lifespan of the PEM water electrolysis device.

Description

Technical Field

[0001] This invention belongs to the field of proton exchange membrane water electrolysis technology, specifically relating to a carbon-titanium based porous transport layer deposited on the cathode of a proton exchange membrane water electrolysis, its preparation method, and its application. Background Technology

[0002] Proton exchange membrane electrolysis (PEMWE), as a highly efficient, fast-response, and high-purity hydrogen production technology, has broad application prospects in the field of renewable energy coupled hydrogen production. The porous transport layer (PTL) is one of the key components in a PEMWE single cell, located between the catalyst layer and the bipolar plates, and plays multiple roles, including supplying water to the catalyst layer, expelling gas, conducting electrons and heat, and providing mechanical support. Currently, titanium-based porous transport layers (Ti-PTLs) are commonly used on the anode side, relying on the naturally formed titanium oxide passivation layer on the titanium surface to resist corrosion in strong acid, high potential, and oxygen-rich environments. However, this passivation layer has poor conductivity, and thickening it leads to increased interfacial contact resistance. Therefore, existing technologies often incorporate noble metals such as platinum, gold, and iridium, or corrosion-resistant conductive coatings on the anode Ti-PTL surface to improve conductivity and durability.

[0003] Unlike the anode, the cathode is located in a hydrogen evolution environment with a lower potential. Traditionally, this environment is considered relatively mild for Ti-PTLs, leading to insufficient attention being paid to the degradation of Ti-PTL cathodes during long-term operation. Currently, carbon paper or carbon cloth are commonly used as porous transport layers on the cathode side of PEMWEs, primarily due to the low cost of carbon materials and their mature applications in fuel cells. However, under conditions of high differential pressure, high-pressure hydrogen, high current density, and long-term operation, carbon paper or carbon cloth suffers from compression deformation, localized damage, and insufficient thickness and pore structure stability, making it difficult to meet the mechanical strength and long-term durability requirements of high differential pressure operation. While using titanium fiber felt, titanium mesh, or sintered titanium porous materials as the cathode PTL can improve mechanical strength and pressure adaptability, the degradation problem of unprotected Ti-PTL cathodes during long-term operation remains largely unrecognized.

[0004] In recent years, research on the degradation of Ti-PTL in PEMWE has gradually increased, but the vast majority of studies focus on the anode side. For example, the research paper entitled "Dissolution of the Ti porous transport layer inproton exchange membrane water electrolyzers" published by J. Cho et al. systematically studied the dissolution behavior of titanium-based PTL under anode operating conditions. However, there is no systematic study in the existing literature on the degradation mechanism of cathode-side Ti-PTL in low-potential hydrogen evolution environment and its impact on the long-term stability of the electrolyzer. This field lacks both a clear understanding of the failure modes of cathode Ti-PTL and effective protection measures for cathode service conditions. Existing coating technologies also have significant shortcomings: noble metal coatings are expensive and difficult to achieve uniform coverage within three-dimensional porous titanium fiber structures; conventional non-noble metal coatings or ceramic coatings are mostly designed for high-potential anode environments, and their applicability in acidic hydrogen evolution environments at the cathode is still unclear.

[0005] Therefore, there is an urgent need for a protection scheme specifically for the titanium-based porous transport layer of the proton exchange membrane water electrolysis cathode to suppress the degradation of the titanium matrix under cathode service conditions, while taking into account the needs of low cost and large-scale application. Summary of the Invention

[0006] This invention addresses the problems existing in the prior art by providing a carbon-titanium-based porous transport layer deposited on the cathode of a proton exchange membrane water electrolysis device, its preparation method, and its application. The aim is to overcome the issues of insufficient mechanical strength or easy degradation of existing cathode porous transport layers under high pressure differential and long-life operating conditions, reduce the risk of surface oxidation and titanium ion dissolution of the cathode titanium-based porous transport layer in acidic hydrogen evolution environments, suppress the increase in interfacial contact resistance and the poisoning of the cathode catalyst layer, thereby improving the long-term operational stability and durability of the proton exchange membrane water electrolysis device.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The first aspect of this invention provides a method for preparing a carbon-titanium-based porous transport layer deposited on a proton exchange membrane water electrolysis cathode, comprising the following steps: (1) Pre-treat the titanium-based porous matrix to remove surface oil and impurities; (2) The pretreated titanium-based porous substrate is placed in a magnetron sputtering device and a Ti target is used for magnetron sputtering to deposit a Ti transition layer on the surface of the titanium-based porous substrate. (3) On the surface of the Ti transition layer, a Cr-Zr-Nb ternary doped amorphous carbon layer is formed by magnetron sputtering co-deposition using a graphite target, a Cr target, a Zr target, and an Nb target. During the deposition process, the sputtering power of the Cr target, the Zr target, and the Nb target is controlled so that the atomic percentage of Cr in the Cr-Zr-Nb ternary doped amorphous carbon layer is 2%-4%, the atomic percentage of Zr is 2%-4%, and the atomic percentage of Nb is 0.5%-1.5%. (4) After deposition, heat treatment is carried out in a nitrogen atmosphere to obtain the carbon titanium-based porous transport layer of the proton exchange membrane water electrolytic cathode.

[0009] Further, the titanium-based porous matrix in step (1) is titanium fiber felt, titanium mesh, sintered titanium powder porous plate, titanium foam or a composite of the above structures.

[0010] Further, the titanium-based porous matrix in step (1) is titanium fiber felt with a thickness of 100-400 μm, a porosity of 30%-70%, and a titanium fiber diameter of 1-100 μm.

[0011] Furthermore, the thickness of the Ti transition layer in step (2) is 50-200 nm.

[0012] During magnetron sputtering deposition, a natural titanium oxide passivation layer inevitably forms on the surface of the porous titanium substrate after exposure to the atmosphere. This significantly reduces the interfacial bonding strength between the subsequent carbon-based coating and the titanium substrate, leading to coating delamination failure during service. By depositing a high-purity Ti transition layer on the pretreated porous titanium substrate, a fresh, oxide-free titanium metal surface is provided. This Ti transition layer has the same chemical composition and crystal structure as the titanium substrate, forming a strong metallurgical bond. Simultaneously, the pure titanium atoms on the Ti transition layer surface can form Ti-C chemical bonds with the carbon atoms in the subsequently deposited doped amorphous carbon layer, further improving the interfacial bonding between the carbon layer and the substrate. Furthermore, the Ti transition layer also acts as a gradient buffer layer, alleviating thermal stress caused by the difference in thermal expansion coefficients between the titanium substrate and the doped amorphous carbon layer. This prevents cracking or delamination due to stress accumulation during heat treatment or long-term service, thus ensuring the structural integrity and long-term stability of the entire composite coating system under the PEMWE cathode acidic hydrogen evolution environment.

[0013] Furthermore, in step (3), the thickness of the Cr-Zr-Nb ternary doped amorphous carbon layer is 150-400 nm.

[0014] Further, in step (4), the nitrogen-containing atmosphere is nitrogen, ammonia, or a mixture of nitrogen and argon.

[0015] Furthermore, in step (4), the heat treatment temperature is 400-550℃ and the time is 0.5-3 h.

[0016] Amorphous carbon matrix possesses high electronic conductivity and chemical inertness, forming a physical barrier between the titanium matrix and the acidic hydrogen evolution environment of the cathode, preventing direct contact between the corrosive medium and the titanium matrix. Doping amorphous carbon with Cr, Zr, and Nb at atomic percentages of 2%-4%, 2%-4%, and 0.5%-1.5% can improve its density and corrosion resistance while maintaining the carbon layer's conductivity. During service, Cr can form a dense Cr₂O₃ passivation layer in situ, filling micropores in the carbon film; Zr has a strong affinity for carbon, forming ZrC nanocrystals dispersed within the carbon matrix during co-deposition, providing dispersion reinforcement; Nb can form NbC nanocrystal nuclei, further increasing structural density, while also exhibiting excellent chemical stability in acidic environments. The synergistic effect of these three elements results in doped amorphous carbon layers with significantly higher density, corrosion resistance, and long-term structural stability than pure amorphous carbon layers, effectively blocking the penetration pathways of corrosive media. In addition, after the nitriding heat treatment in step (4), Cr, Zr, and Nb are partially converted into CrN, ZrN, and NbN nanoparticles, which further enhances the barrier properties of the coating.

[0017] The second aspect of the present invention provides a carbon-titanium based porous transport layer deposited on a proton exchange membrane water electrolysis cathode, which is prepared by the preparation method of the proton exchange membrane water electrolysis cathode deposited on a carbon-titanium based porous transport layer described in the present invention.

[0018] A third aspect of the present invention provides a proton exchange membrane water electrolysis device, comprising a membrane electrode, an anode porous transport layer, a cathode porous transport layer, an anode flow field plate, a cathode flow field plate, a seal and an end plate, wherein the cathode porous transport layer is the carbon-plated titanium-based porous transport layer of the present invention.

[0019] Furthermore, the proton exchange membrane water electrolysis device is a differential pressure proton exchange membrane water electrolysis stack, with a cathode-side back pressure of 0.5-4.0 MPa.

[0020] Compared with the prior art, the present invention has the following beneficial effects: Based on the understanding of the "oxidative dissolution" failure mechanism of Ti-PTL cathodes, this invention specifically designs a composite coating system combining a Ti transition layer, a Cr-Zr-Nb ternary doped amorphous carbon layer, and post-treatment nitriding, significantly enhancing the adhesion between the coating and the titanium substrate. In the doped amorphous carbon layer, Cr forms a dense chromium oxide passivation layer, filling the micropores in the carbon film; Zr has a strong affinity for carbon, and the resulting ZrC nanocrystals are dispersed throughout the carbon substrate, providing reinforcement; Nb further improves the structural density and maintains chemical stability in acidic environments. The combined use of these three elements enables the coating to maintain good conductivity while possessing excellent density and corrosion resistance. The post-treatment nitriding process further transforms the doped metal into nitride nanoparticles, filling the micro-defects in the carbon layer and enhancing the barrier effect. This approach inhibits the oxidation and ion dissolution of the titanium substrate at its source, blocking the migration path of Ti ions to the cathode catalyst layer, thereby effectively preventing catalyst layer poisoning and increased interfacial contact resistance. Compared with existing precious metal coating solutions, this invention employs a non-precious metal doping system combined with magnetron sputtering, significantly reducing costs and ensuring compatibility with existing production lines, making it suitable for large-scale fabrication. Furthermore, the carbon-titanium-based porous transport layer obtained by this invention possesses both high-pressure mechanical strength and resistance to oxidation and leaching, meeting the high-pressure operation requirements of differential pressure PEMWE stacks. Attached Figure Description

[0021] Figure 1 The images show the appearance of the uncoated titanium-based porous transport layer and the carbon-coated titanium-based porous transport layer obtained in Example 1 of this invention. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] In existing technologies, carbon paper or carbon cloth are often used as porous transport layers on the cathode side of proton exchange membrane water electrolysis. While some schemes propose using titanium-based materials as alternatives, none have systematically studied the failure mechanism of the titanium-based porous transport layer during long-term operation, nor have they recognized the potential for degradation pathways independent of hydrogen embrittlement under low-potential acidic hydrogen evolution environments at the cathode. Through a systematic study of uncoated Ti-PTL cathodes under simulated PEMWE cathode service conditions, the inventors discovered that the dominant failure mechanism is Ti ion dissolution induced by surface oxidation and subsequent catalyst layer poisoning. The specific verification process is as follows: A TA1 titanium sheet was used as the test sample, serving as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode. All test potentials were converted to values ​​using a reversible hydrogen electrode as the reference electrode. The electrolyte was 1.0 mol / L sulfuric acid, the temperature was 80℃, and hydrogen gas was continuously introduced to simulate the cathode hydrogen evolution environment. First, open-circuit potential tests were performed. The results showed that under hydrogen saturation conditions, the open-circuit potential gradually stabilized at -0.3 V to -0.4 V, indicating that the titanium surface was in a more active electrochemical state under this simulated cathode environment. Subsequently, potentiodynamic polarization tests were performed, with corrosion potentials of approximately -0.3 V to -0.4 V and corrosion current densities of approximately 400-500 μA cm⁻¹. -2 This indicates that titanium-based materials exhibit a persistent anodic dissolution tendency under the cathode simulation environment. Further, the titanium sample was subjected to constant potential polarization at -0.1 V, a potential close to the local potential of the PEMWE cathode Ti-PTL during actual service. The current density remained stable and positive during the test, indicating that a net anodic oxidation process still occurred on the titanium surface under this low cathode potential. After 3 hours of constant potential polarization, the electrolyte was analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES). The Ti ion concentration was 100-200 ppb, confirming that Ti ion dissolution continued in the titanium matrix under these conditions. X-ray photoelectron spectroscopy was used to analyze the titanium surface after the constant potential test, revealing Ti 2p... 3 / 2 The signal is mainly located in the binding energy region of titanium oxide, and no obvious dominant peaks of metallic titanium or titanium hydrides were observed; Raman spectra showed peaks similar to those of amorphous or low-crystallinity TiO₂. x Broad peaks or envelope peaks related to terminal Ti-OH, bridged Ti-O(H)-Ti, and Ti-O-Ti were observed. The XPS and Raman spectroscopy results consistently indicate that a surface layer mainly composed of titanium oxide and titanium hydroxylate was formed on the titanium surface under the cathode simulation environment, rather than a hydride layer.

[0024] Based on the above electrochemical tests, ion dissolution detection, and surface chemical analysis results, the failure of the cathode Ti-PTL in the low-potential acidic hydrogen evolution environment of PEMWE is mainly manifested by surface oxidation to form TiO2. x Or Ti(OH) x The defect layer, accompanied by the continuous dissolution of Ti ions, can migrate to the cathode catalyst layer, causing poisoning of the catalyst active sites. This failure mechanism is different from the traditionally believed hydrogen embrittlement-dominated one, and is a degradation process characterized by surface oxidation and ion dissolution.

[0025] Based on the discovery of the above failure mechanism, the present invention provides a carbon-plated titanium-based porous transport layer specifically targeting this failure path and its preparation method. By constructing a Ti transition layer and a Cr-Zr-Nb ternary doped amorphous carbon layer on the surface of a titanium-based porous substrate and then performing post-treatment nitriding, the surface oxidation of the titanium substrate and the dissolution of Ti ions are suppressed from the source.

[0026] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments. The raw materials and reagents used in the following embodiments are all commercially available, and the magnetron sputtering equipment is conventional equipment in the art. Experimental methods not specified in the embodiments were performed according to conventional operating conditions in the art.

[0027] Example 1 This embodiment provides a carbon-titanium based porous transport layer deposited on a proton exchange membrane water electrolysis cathode, the preparation method of which includes the following steps: (1) Titanium fiber felt was selected as the titanium-based porous matrix and cut to a size of 3.0 cm × 3.0 cm. The titanium fiber felt was ultrasonically cleaned in acetone and ethanol for 15 min each, and then ultrasonically cleaned in deionized water for 15 min to remove surface oil and impurities. After cleaning, it was dried in a vacuum drying oven at 80℃ for 4 h. The thickness of the titanium fiber felt was 250 μm, the porosity was 55%, and the diameter of the titanium fiber was about 30 μm.

[0028] (2) Fix the dried titanium fiber felt onto the sample holder of the magnetron sputtering equipment, allowing the titanium fiber felt to rotate with the sample holder. Close the vacuum chamber and evacuate until the background pressure does not exceed 5 × 10⁻⁶. -3 Argon gas was introduced as the working gas, and the working pressure was adjusted to 0.5 Pa. The Ti target power supply was turned on, and DC magnetron sputtering mode was adopted with a sputtering power of 200 W, a substrate temperature of room temperature, and a deposition time of 10 min to deposit a Ti transition layer on the surface of titanium fiber felt. The thickness of the Ti transition layer was approximately 100 nm.

[0029] (3) On the surface of the titanium fiber felt with the Ti transition layer, a Cr-Zr-Nb ternary doped amorphous carbon layer was formed by magnetron sputtering co-deposition using graphite, Cr, Zr, and Nb targets. Argon gas was introduced as the working gas during the deposition process, with a working pressure of 0.5 Pa, a sputtering power of 300 W, a substrate temperature of 150 °C, a deposition time of 60 min, and a substrate bias of -100 V. At the same time, the sample holder was continuously rotated at a speed of 5 rpm to ensure uniform coverage of the coating on the inner and outer surfaces of the three-dimensional porous structure. By independently controlling the sputtering power of the Cr, Zr, and Nb targets, the atomic percentages of Cr, Zr, and Nb in the obtained Cr-Zr-Nb ternary doped amorphous carbon layer were 3%, 3%, and 1%, respectively, with a total doping amount of 7% and the remainder being carbon. The thickness of the Cr-Zr-Nb ternary doped amorphous carbon layer was approximately 280 nm.

[0030] (4) After deposition, the sputtering power supply is turned off, a vacuum state is maintained, the temperature is raised to 450°C, and a mixed atmosphere of nitrogen and argon (volume ratio of 1:1) is introduced. The mixture is kept at this temperature for 1 h for heat treatment, so that the Cr, Zr, and Nb elements in the Cr-Zr-Nb ternary doped amorphous carbon layer are partially converted into CrN, ZrN, and NbN nanoparticles. After heat treatment, the mixture is naturally cooled to room temperature under nitrogen atmosphere protection to obtain the carbon titanium-based porous transport layer deposited on the proton exchange membrane water electrolysis cathode.

[0031] The morphologies of the uncoated titanium-based porous transport layer (uncoated Ti-PTL) and the carbon-coated titanium-based porous transport layer (carbon-coated Ti-PTL) obtained in Example 1 are as follows: Figure 1 As shown.

[0032] Example 2 This embodiment provides a carbon-titanium based porous transport layer deposited on a proton exchange membrane water electrolysis cathode, the preparation method of which includes the following steps: (1) Titanium fiber felt was selected as the titanium-based porous matrix and cut to a size of 3.0 cm × 3.0 cm. The titanium fiber felt was ultrasonically cleaned in acetone and ethanol for 15 min each, and then ultrasonically cleaned in deionized water for 15 min to remove surface oil and impurities. After cleaning, it was dried in a vacuum drying oven at 80℃ for 4 h. The thickness of the titanium fiber felt was 250 μm, the porosity was 55%, and the diameter of the titanium fiber was about 30 μm.

[0033] (2) Fix the dried titanium fiber felt onto the sample holder of the magnetron sputtering equipment, allowing the titanium fiber felt to swing with the sample holder. Close the vacuum chamber and evacuate until the background pressure does not exceed 5 × 10⁻⁶. -3 Argon gas was introduced as the working gas, and the working pressure was adjusted to 0.6 Pa. The Ti target power supply was turned on, and DC magnetron sputtering mode was adopted with a sputtering power of 150 W, a substrate temperature of 50℃, and a deposition time of 15 min to deposit a Ti transition layer on the surface of titanium fiber felt. The thickness of the Ti transition layer was approximately 150 nm.

[0034] (3) On the surface of the titanium fiber felt with the Ti transition layer, a Cr-Zr-Nb ternary doped amorphous carbon layer was formed by magnetron sputtering co-deposition using graphite, Cr, Zr, and Nb targets. Argon gas was introduced as the working gas during the deposition process, with a working pressure of 0.7 Pa, a sputtering power of 400 W, a substrate temperature of 100 °C, a deposition time of 90 min, and a substrate bias of -80 V. At the same time, the sample holder was continuously oscillating at a speed of 8 rpm to ensure uniform coverage of the coating on the inner and outer surfaces of the three-dimensional porous structure. By independently controlling the sputtering power of the Cr, Zr, and Nb targets, the atomic percentages of Cr, Zr, and Nb in the obtained Cr-Zr-Nb ternary doped amorphous carbon layer were 2.5%, 3.5%, and 0.8%, with a total doping amount of 6.8% and the remainder being carbon. The thickness of the Cr-Zr-Nb ternary doped amorphous carbon layer was approximately 200 nm.

[0035] (4) After deposition, the sputtering power supply is turned off, a vacuum state is maintained, the temperature is raised to 480℃, an ammonia atmosphere is introduced, and the temperature is maintained for 0.8 h for heat treatment, so that the Cr, Zr, and Nb elements in the Cr-Zr-Nb ternary doped amorphous carbon layer are partially converted into CrN, ZrN, and NbN nanoparticles. After heat treatment, the layer is naturally cooled to room temperature under a nitrogen atmosphere to obtain the carbon titanium-based porous transport layer deposited on the proton exchange membrane water electrolysis cathode.

[0036] Comparative Example 1 The difference between this comparative example and Example 1 is that: in step (2), no Ti transition layer is deposited, and the pretreated titanium fiber felt is directly co-deposited with the Cr-Zr-Nb ternary doped amorphous carbon layer in step (3). The rest is the same as in Example 1.

[0037] Comparative Example 2 The difference between this comparative example and Example 1 is that in step (3), a graphite target, a Cr target, and a Zr target are used for magnetron sputtering co-deposition, and an Nb target is not set to form a Cr-Zr binary doped amorphous carbon layer, wherein the atomic percentage of Cr is 3%, the atomic percentage of Zr is 3%, and the balance is carbon. All other aspects are the same as in Example 1.

[0038] Comparative Example 3 The difference between this comparative example and Example 1 is that in step (3), the Nb target is replaced with a Mo target, and a Cr-Zr-Mo ternary doped amorphous carbon layer is formed by magnetron sputtering co-deposition using a graphite target, a Cr target, a Zr target, and a Mo target. The atomic percentage of Mo is controlled to be 1%, the atomic percentages of Cr and Zr are still 3%, the total doping amount is 7%, and the remainder is carbon. All other aspects are the same as in Example 1.

[0039] Comparative Example 4 The difference between this comparative example and Example 1 is that in step (3), the Cr target is replaced with a Ti target, and a graphite target, a Ti target, a Zr target and a Nb target are used for magnetron sputtering co-deposition to form a Ti-Zr-Nb ternary doped amorphous carbon layer. The atomic percentage of Ti is controlled to be 3%, the atomic percentages of Zr and Nb are 3% and 1% respectively, the total doping amount is 7%, and the remainder is carbon. All other aspects are the same as in Example 1.

[0040] Comparative Example 5 The difference between this comparative example and Example 1 is that the heat treatment atmosphere in step (4) is changed to argon atmosphere, and no nitrogen-containing gas is introduced. The heat treatment is carried out at 450°C for 1 h, and after the heat treatment is completed, it is naturally cooled to room temperature under the protection of argon atmosphere. All other aspects are the same as in Example 1.

[0041] Performance testing 1. Electrochemical corrosion performance testing The test samples included: uncoated carbon titanium-based porous transport layer, carbon titanium-based porous transport layer prepared in Examples 1-2, and carbon titanium-based porous transport layer prepared in Comparative Examples 1-5.

[0042] A three-electrode system was used, with each sample as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode (the test potential was converted to a reversible hydrogen electrode). The electrolyte was 1.0 mol / L sulfuric acid, the temperature was 80℃, and hydrogen gas was continuously introduced. After the open-circuit potential stabilized, potentiodynamic polarization testing was performed at a scan rate of 1 mV / s, and the corrosion potential and corrosion current density were recorded.

[0043] 2. Tests on potentiostatic stability and Ti ion dissolution. The test samples were the same as above. Each sample was subjected to constant potential polarization at -0.1 V (vs. RHE) for 48 h, and the change in current density over time was recorded. After the constant potential test, the electrolyte was collected, and the Ti ion concentration in the electrolyte was detected by inductively coupled plasma atomic emission spectrometry (ICP-AES). The cumulative Ti dissolution amount over 48 h was calculated.

[0044] The test results are shown in Table 1.

[0045] Table 1. Comparison of electrochemical corrosion performance and Ti leaching amount in each example and comparative example.

[0046] 3. Long-term operational stability test of a single battery PEMWE single cells were assembled using uncoated titanium carbon-based porous transport layers, titanium carbon-based porous transport layers prepared in Examples 1-2, and titanium carbon-based porous transport layers prepared in Comparative Examples 1-5 as cathode porous transport layers.

[0047] The assembly structure of the single cell is as follows: cathode flow field plate / cathode porous transport layer / cathode catalyst layer (Pt / C) / proton exchange membrane / anode catalyst layer (iridium-based oxide) / anode porous transport layer / anode flow field plate, with each layer sealed together by seals and fasteners. The anode porous transport layer is a platinum-coated titanium-based porous transport layer.

[0048] Operating conditions: 80℃, deionized water is introduced at the anode (20 mL / min), at 2.0 A cm -2 The membrane electrode was continuously run under constant current for 1000 h, and the voltage decay rate was recorded. After the test, the membrane electrode was digested, and the Ti content in the cathode catalyst layer was detected by ICP-OES.

[0049] The test results are shown in Table 2.

[0050] Table 2. Results of 1000-hour long-term operation test of single cells for each embodiment and comparative example.

[0051] As can be seen from the test results in Tables 1 and 2, the carbon-plated titanium-based porous transport layers prepared in Examples 1 and 2 of this invention are significantly superior to the uncoated titanium-based porous transport layers and the comparative examples in all performance indicators. The corrosion potentials of Examples 1 and 2 showed a significant positive shift, and the corrosion current density and constant potential current density were significantly reduced, indicating a significant decrease in the cumulative dissolution of Ti. This demonstrates that the present invention constructs a dense composite protective coating on the surface of titanium fibers, which can effectively block the contact between the corrosive medium and the titanium substrate, thereby inhibiting the oxidation and dissolution of titanium at the source. In the long-term operation test of the single cell, the voltage decay rates of Examples 1 and 2 were both at extremely low levels, and the Ti content in the cathode catalyst layer was significantly lower than that of the uncoated sample and the comparative examples. This indicates that the inhibitory effect of the coating on the dissolution of titanium ions directly translates into improved long-term operational stability of the electrolyzer. The significant reduction in the Ti content in the cathode catalyst layer further confirms that the coating effectively blocks the migration path of titanium ions to the catalyst layer, avoiding catalyst layer poisoning.

[0052] In Comparative Example 1, the lack of a Ti transition layer resulted in insufficient adhesion between the coating and the titanium substrate, leading to numerous defects in the coating. Corrosive media easily penetrated into the titanium substrate along these defects, significantly reducing the protective effect. In Comparative Example 2, the absence of Nb doping meant the Cr-Zr binary doping system lacked the structural densification effect of Nb. Consequently, the coating's density and barrier properties were inferior to the Cr-Zr-Nb ternary system, resulting in relatively high corrosive media permeability. In Comparative Example 3, replacing Nb with Mo resulted in Mo having lower carbide-forming ability and chemical stability in acidic environments compared to Nb. Furthermore, the synergistic effect between Mo and Cr / Zr was weak, failing to achieve the structural densification level of the Cr-Zr-Nb ternary system. In Comparative Example 4, replacing Cr with Ti, while Ti is homologous to the substrate and has a strong affinity for carbon, it cannot form a dense passivation layer like Cr₂O₃ to fill the micropores in the carbon film during service. Therefore, the barrier properties of the coating were significantly lower than those of the Cr-containing system. Comparative Example 5, without post-treatment nitriding, does not contain CrN, ZrN, or NbN nanoparticles in its coating. Lacking the filling and densification effect of these nitride particles on coating defects, the coating's density and long-term stability are inferior to those of the Example.

[0053] 4. Differential pressure stack operation test The carbon-plated titanium-based porous transport layer prepared in Example 1 was used as the cathode porous transport layer to assemble a differential pressure PEMWE stack. The stack structure consisted of multiple single cells stacked in series, with the single cell structure as described in "3. Long-term operational stability test of single cells" above. A back pressure valve was installed on the cathode side to achieve a back pressure of 3.0 MPa, while the anode side was at atmospheric pressure. The stack was operated at 80°C, and the pressure was recorded at 0.5 A / cm. -2 and 3.0 A cm -2 The voltage of the fuel cell stack.

[0054] Test results show that the fuel cell stack can operate stably under a cathode back pressure of 3.0 MPa. At 0.5 A cm⁻¹ -2 At that time, the stack voltage was 4.82 V, corresponding to an average single-cell voltage of approximately 1.61 V; at 3.0 A cm -2 At that time, the stack voltage was 5.72 V, corresponding to an average single-cell voltage of approximately 1.91 V. This result indicates that the carbon-plated titanium-based porous transport layer prepared in this invention is suitable not only for laboratory single cells but also for high-voltage or differential-voltage PEMWE stacks.

[0055] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a carbon-titanium-based porous transport layer deposited on a proton exchange membrane water electrolysis cathode, characterized in that, Includes the following steps: (1) Pre-treat the titanium-based porous matrix to remove surface oil and impurities; (2) The pretreated titanium-based porous substrate is placed in a magnetron sputtering device and a Ti target is used for magnetron sputtering to deposit a Ti transition layer on the surface of the titanium-based porous substrate. (3) On the surface of the Ti transition layer, a Cr-Zr-Nb ternary doped amorphous carbon layer is formed by magnetron sputtering co-deposition using a graphite target, a Cr target, a Zr target, and an Nb target. During the deposition process, the sputtering power of the Cr target, the Zr target, and the Nb target is controlled so that the atomic percentage of Cr in the Cr-Zr-Nb ternary doped amorphous carbon layer is 2%-4%, the atomic percentage of Zr is 2%-4%, and the atomic percentage of Nb is 0.5%-1.5%. (4) After deposition, heat treatment is carried out in a nitrogen atmosphere to obtain the carbon titanium-based porous transport layer of the proton exchange membrane water electrolytic cathode.

2. The preparation method according to claim 1, characterized in that: The titanium-based porous matrix in step (1) is titanium fiber felt, titanium mesh, sintered titanium powder porous plate, titanium foam or a composite of the above structures.

3. The preparation method according to claim 2, characterized in that: The titanium-based porous matrix in step (1) is titanium fiber felt with a thickness of 100-400 μm, a porosity of 30%-70%, and a titanium fiber diameter of 1-100 μm.

4. The preparation method according to claim 1, characterized in that: The thickness of the Ti transition layer in step (2) is 50-200 nm.

5. The preparation method according to claim 1, characterized in that: In step (3), the thickness of the Cr-Zr-Nb ternary doped amorphous carbon layer is 150-400 nm.

6. The preparation method according to claim 1, characterized in that: In step (4), the nitrogen-containing atmosphere is nitrogen, ammonia, or a mixture of nitrogen and argon.

7. The preparation method according to claim 1, characterized in that: In step (4), the heat treatment temperature is 400-550℃ and the time is 0.5-3 h.

8. A carbon-titanium based porous transport layer deposited on the cathode of a proton exchange membrane water electrolysis process, characterized in that, It is prepared by the method for preparing a carbon-titanium based porous transport layer by plating a proton exchange membrane water electrolysis cathode as described in any one of claims 1-7.

9. A proton exchange membrane water electrolysis device, comprising a membrane electrode, an anode porous transport layer, a cathode porous transport layer, an anode flow field plate, a cathode flow field plate, a sealing element, and an end plate, characterized in that, The cathode porous transport layer is the carbon-plated titanium-based porous transport layer as described in claim 8.

10. The proton exchange membrane water electrolysis device according to claim 9, characterized in that: The proton exchange membrane water electrolysis device is a differential pressure proton exchange membrane water electrolysis stack with a cathode-side back pressure of 0.5-4.0 MPa.

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