Preparation and application of in-situ constructed ultra-low iridium confined supported PEM electrode material

Abstract

This invention discloses an in-situ constructed ultra-low iridium confined loaded PEM electrode material and its preparation and application. Using a three-dimensional titanium-based porous conductive framework as a substrate, channels with a curvature of 0.025–0.077 nm are constructed in-situ through anodic oxidation. ‑1 The nanotube structure was used, and then the iridium precursor was selectively coordinated and adsorbed at high curvature and defect sites by pulsed bias voltage. Stable iridium single-atom active centers were formed through low-temperature immobilization, resulting in an integrated electrode that can be directly used as the anode for PEM water electrolysis. Results showed that at 60℃ and with pure water feed, 1A cm⁻¹… ‑2 and 2A cm ‑2 The time slot voltages were 1.67V and 1.8V respectively, and the 1A cm ‑2 Stable operation for 1050 hours, with a decay rate of less than 32 μV / h. ‑1 The iridium loading on the anode side is as low as 0.11 mg. Ir cm ‑2 Compared with traditional powder catalyst coated anodes, this invention eliminates the need for multi-interface superposition of traditional powder catalyst layers and independent PTLs, and can be directly used as the anode side of PEM membrane electrodes, achieving functional coupling between the catalyst layer and the PTL, and alleviating local overpotential concentration and structural inhomogeneity degradation under high current operation.

Description

Technical Field

[0001] This invention belongs to the field of proton exchange membrane electrolysis for hydrogen production technology. Specifically, it relates to a method for preparing and applying an integrated in-situ constructed electrode material that serves as both a catalytic layer and a porous transport layer for the anode side of a PEM electrolyzer. In particular, it relates to a PEM anode material in which tubular channels are formed in situ on a three-dimensional titanium-based porous conductive framework and iridium single-atom active sites are confined and loaded, and its application. Background Technology

[0002] Electrolysis of water can convert renewable energy into high-purity hydrogen. Proton exchange membrane (PEM) electrolysis offers advantages such as high current density, fast response, compact system, and high hydrogen purity, but its large-scale application is still limited by anode efficiency, stability, and cost. Existing PEM electrolyzers typically use iridium-containing powdered catalysts coated on the membrane or support surface, then assembled with an independent porous transport layer. This type of split structure often suffers from the problem of multiple interfaces overlapping—catalyst layer, binder, transport layer, and current collector framework—which easily leads to increased interfacial contact resistance, increased catalyst layer resistance, insufficient utilization of active sites, and localized overpotential concentration under high current density, potentially causing uneven degradation of the anode catalyst layer. Existing research shows that the catalyst layer resistance, PTL / catalyst layer contact state, and local stress distribution in PEM anodes directly affect device performance and lifespan. Simultaneously, the porous titanium transport layer must also function as a conductor, water supply, oxygen removal, and mechanical support. Traditional structures are prone to problems such as limited mass transfer, uneven contact, and structural instability under high current density conditions.

[0003] To reduce iridium usage and improve practical utilization, it is urgent to develop an integrated in-situ construction method that differs from traditional powder-coated anodes. This method can directly form a stable channel structure on the surface of a three-dimensional titanium-based porous conductive framework, and achieve high dispersion and strong anchoring load of iridium active centers within the channels. This reduces ohmic losses and interlayer failures caused by multi-interface assembly, while also ensuring high conductivity, high stability, and feasibility of scale-up preparation. The result is a practical integrated electrode material that can be directly used on the anode side of a PEM electrolyzer. Summary of the Invention

[0004] The purpose of this invention is to provide an integrated anode construction strategy suitable for PEM electrolyzers. By constructing the active structure in situ on the surface of a three-dimensional titanium-based porous conductive framework, problems such as poor interfacial contact, active site shielding, and catalyst layer peeling caused by traditional powder catalyst slurry preparation, catalyst layer transfer, and binder-assisted film formation can be reduced, which is beneficial to improving the structural stability and mass transfer performance of the anode material.

[0005] Another objective of this invention is to provide a method for constructing an interface microenvironment based on curvature control. By controlling the anodic oxidation conditions, titanium dioxide channel structures with different channel sizes and local curvature characteristics are obtained, thereby forming differentiated geometric confinement on the carrier surface. This allows for the regulation of the adsorption, migration, and immobilization behavior of iridium precursors, improving the probability of iridium single-atom formation and stable anchoring capability.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a method for preparing an in-situ constructed ultra-low iridium confined loaded PEM electrode material, comprising the following steps:

[0008] S1. The three-dimensional titanium-based porous conductive framework is sequentially cleaned with organic solvent and deionized water, and then dried after acid washing to remove the surface oxide layer, to obtain the pretreated titanium-based framework.

[0009] S2. Using the pretreated titanium-based framework as the anode and an inert conductive material as the cathode, anodic oxidation is performed in a mixed electrolyte containing ammonium fluoride, deionized water, and ethylene glycol to obtain a titanium dioxide channel precursor grown in situ on the surface of a three-dimensional titanium-based framework.

[0010] S3. The titanium dioxide channel precursor obtained in step S2 is placed as the working electrode in the adsorption solution containing iridium precursor. Under the action of pulse bias voltage, induced coordination adsorption treatment is performed to make the iridium precursor selectively adsorbed in the titanium dioxide channel, at the tube opening, in the high curvature region and at the surface active sites.

[0011] S4. The sample after step S3 is subjected to low-temperature immobilization treatment to fix the iridium precursor adsorbed on the surface of the titanium dioxide channel structure in an orientation, forming a stable anchored iridium single-atom active center.

[0012] S5. The sample obtained in step S4 is naturally cooled and then washed and dried to obtain the in-situ constructed ultra-low iridium confined load PEM electrode material.

[0013] In a preferred embodiment, in step S1, the three-dimensional titanium-based porous conductive framework includes at least one of titanium felt, titanium mesh, and titanium foam, preferably titanium felt. The thickness of the three-dimensional titanium-based porous conductive framework is 0.1–1.0 mm, preferably 0.2–0.8 mm. The titanium-based framework is preferably cut to a size of 1.0 × 1.0 cm. 2 1.5×2.0cm 2 Or 1.5×4.0cm 2 One of them.

[0014] In a preferred embodiment, in step S1, the cleaning process involves sequential ultrasonic cleaning in acetone, ethanol, and deionized water, with each cleaning cycle lasting 3–15 minutes, preferably 5 minutes. The acid pickling uses one or more of hydrochloric acid, nitric acid, or sulfuric acid, preferably hydrochloric acid or nitric acid; the acid concentration is 5%–20%, preferably 8%–15%; and the pickling time is 10–30 minutes, preferably 15–20 minutes.

[0015] In a preferred embodiment, in step S2, the electrolyte is prepared by mixing 0.1–0.5 g ammonium fluoride, 3–10 mL deionized water, and 30–50 mL ethylene glycol, preferably by mixing 0.25 g ammonium fluoride, 5 mL deionized water, and 40 mL ethylene glycol. The anodic oxidation voltage is 20–60 V, preferably 20–50 V, more preferably 20 V, 40 V, or 60 V; the anodic oxidation time is 1–3 h, preferably 2 h.

[0016] In a preferred embodiment, in step S3, the adsorption solution includes an iridium precursor, a solvent, and an optional acid adjuster. The iridium precursor is one or more of chloroiridium acid, iridium chloride, or an iridium complex, preferably chloroiridium acid. The concentration of the iridium precursor in the adsorption solution is 0.1–10 mg / mL, preferably 0.5–5 mg / mL. The acid adjuster is hydrochloric acid, with a concentration of 0.001–0.05 mol / L, preferably 0.005–0.02 mol / L. The solvent is water, ethanol, or a water / ethanol mixture.

[0017] In a preferred embodiment, in step S3, the pulsed bias-induced coordination adsorption treatment uses the titanium dioxide channel precursor obtained in step S2 as the working electrode, an inert conductive material as the counter electrode, and optionally a reference electrode to form an electrochemical system. The pulsed bias is one of a square wave pulse, a step-like pulse, a cathode bias pulse, an anode bias pulse, or an alternating cathode-anode pulse, preferably an alternating cathode-anode pulse. The peak potential of the pulsed bias is -0.5 to 1.5 V, the duration of a single pulse is 0.01 to 10 s, the pulse interval is 0.01 to 30 s, and the total number of cycles is 10 to 5000, preferably 100 to 3000.

[0018] In a preferred embodiment, in step S3, the pulse bias-induced coordination adsorption treatment temperature is 10–60°C, preferably 20–40°C; the treatment time is 1–120 min, preferably 5–60 min. Under the action of pulse bias, the iridium precursor preferentially undergoes selective coordination adsorption at the channel opening region, high curvature region, defect site, hydroxyl site, and oxygen coordination site of the titanium dioxide channel, thereby improving the selectivity and stability of iridium single atom formation during subsequent low-temperature immobilization.

[0019] In a preferred embodiment, the cryogenic immobilization treatment in step S4 is carried out in a tube furnace under an atmosphere of argon, nitrogen, or a mixture thereof. The heating rate is 0.5–2 °C / min, preferably 1 °C / min; the cryogenic immobilization temperature is 120–250 °C, preferably 150–220 °C; and the holding time is 0.5–3 h, preferably 1–2 h. Cryogenic immobilization treatment facilitates the directional immobilization of iridium precursors adsorbed on high-curvature regions, channel inner walls, and surface active sites without damaging the original structure of the titanium dioxide channels, thereby inhibiting iridium species migration and aggregation.

[0020] In a preferred embodiment, steps S3 and S4 constitute a cyclic "pulse bias-induced coordination adsorption-low temperature immobilization" process, with 1 to 5 cycles, preferably 2 to 3 cycles. By employing a multi-stage induced adsorption-step immobilization method, the anchoring density of iridium active centers can be gradually increased, and the tendency for local enrichment and granulation caused by a single high load can be reduced.

[0021] In a preferred embodiment, after step S4, the obtained sample can be washed with deionized water or ethanol and dried at 40–80°C for 1–6 hours to remove weakly adsorbed precursors and residual impurities.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] First, this invention uses a three-dimensional titanium-based porous conductive framework as a substrate, constructs nanotube channels in situ through anodic oxidation, and further confines and forms iridium single-atom active centers. The resulting material can be directly used as an anode in a PEM electrolyzer, representing an integrated in-situ structure with functional coupling between the catalytic layer and the porous transport layer. Compared to traditional powder catalyst-coated anodes, this reduces the superposition of multiple interfaces, lowers the risk of poor interfacial contact and interlayer failure, and improves interfacial bonding strength and overall structural stability.

[0024] Second, the present invention employs a pulsed bias-induced coordination adsorption-low temperature immobilization strategy, which differs from traditional static impregnation, drop coating or conventional heat treatment loading methods. This can promote selective coordination adsorption of iridium precursors at high curvature sites and surface active sites, and achieve directional fixation through subsequent low temperature immobilization, thereby inhibiting iridium species migration, aggregation and granulation, improving the utilization rate of precious metals and the long-term stability of single-atom active centers.

[0025] Third, the PEM anode material obtained by the invention combines the conductive support of the three-dimensional titanium-based framework, the mass transfer effect of the titanium dioxide channel structure, and the high atomic utilization efficiency of the iridium single-atom active center. This is beneficial to reduce the resistance of the catalyst layer and the ohmic loss at the interface, improve electron transport, water / oxygen transport and local structural stability under high current density operating conditions, and take into account the low amount of precious metals, high conductivity, high stability and feasibility of scale-up preparation, and has good prospects for practical application. Attached Figure Description

[0026] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0027] Figure 1 SEM image of the ultra-low iridium confined loaded PEM electrode material prepared in Example 1;

[0028] Figure 2 SEM comparison images of PEM electrode materials with different curvatures prepared in Examples 1, 2, and 3;

[0029] Figure 3 The image shows a side SEM image of the ultra-low iridium confined loaded PEM electrode material prepared in Example 1.

[0030] Figure 4 TEM image of the ultra-low iridium confined loaded PEM electrode material prepared in Example 1;

[0031] Figure 5 This is a SEM image of the cross-section of the MEA film electrode prepared by hot pressing of a PEM electrode in Example 1;

[0032] Figure 6 XRD patterns of Ir before and after loading, prepared in Example 1;

[0033] Figure 7 Example 1 compares the activity of the ultra-low iridium confined loaded PEM electrode material prepared in Comparative Example 1 in PEM.

[0034] Figure 8 The results of stability tests in PEM for Example 1 are shown. Detailed Implementation

[0035] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0036] Example 1

[0037] This embodiment provides an in-situ constructed titanium dioxide channel-confined iridium single-atom PEM anode material with adjustable curvature, and its preparation steps are as follows:

[0038] (1) Substrate pretreatment: Take a titanium felt with a thickness of 0.25 mm and cut it into pieces of 1.5 × 4.0 cm. 2 The titanium felt was ultrasonically cleaned in acetone, ethanol and deionized water for 5 min each in sequence; then it was placed in 10% nitric acid solution for 20 min to remove the surface oxide layer; after removal, it was thoroughly washed with deionized water and dried in air to obtain pretreated titanium felt.

[0039] (2) Anodizing: Using the pretreated titanium felt obtained in step (1) as the anode and the platinum sheet as the cathode, the two were placed in a mixed electrolyte consisting of 0.25g NH4F, 5mL deionized water and 40mL ethylene glycol, and anodized for 2h under constant voltage of 40V to obtain a titanium felt sample with titanium dioxide channel precursors grown in situ on the surface.

[0040] (3) Pulse bias-induced coordination adsorption: Prepare an adsorption solution with an iridium chloroacetic acid concentration of 1.0 mg / mL, using a deionized water / ethanol mixture in a volume ratio of 4:1, and add hydrochloric acid to achieve a hydrochloric acid concentration of 0.01 mol / L. Place the sample obtained in step (2) as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode in the adsorption solution. Apply a square wave pulse bias to an electrochemical workstation. The high potential of the pulse is 0.8 V, and the low potential is 0.2 V. The duration of each high and low potential is 1 s, and the total number of pulse cycles is 900. After the pulse bias-induced coordination adsorption treatment is completed, remove the sample and gently wash it with deionized water.

[0041] (4) Low temperature fixation: The sample after step (3) is placed in a tube furnace and heated to 200°C at a heating rate of 1°C / min under an argon atmosphere. The temperature is held for 2 hours and then naturally cooled to room temperature to obtain the sample of Example 1.

[0042] (5) PEM single cell assembly: The sample obtained in step (4) is directly used as the integrated electrode on the anode side of the proton exchange membrane electrolyzer. The titanium felt substrate serves as both the anode catalyst support and the porous transport layer on the anode side. During assembly, the electrode is attached to the proton exchange membrane, with the in-situ constructed confined ultra-low iridium active layer facing the membrane side. A Pt / C electrode is used on the cathode side. The electrode is then assembled and pressed together with the sealing gasket and bipolar plate to obtain a PEM electrolyzer single cell.

[0043] In this embodiment, the titanium dioxide channel structure formed by 40V anodizing has moderate channel size and local curvature characteristics, with an average channel aperture diameter of approximately 57 nm and a corresponding local curvature of approximately 0.035 nm. -1 A single pulse bias-induced coordination adsorption-low temperature immobilization process facilitates the selective adsorption and directional fixation of iridium precursors on the inner wall of the channel, the edge of the channel opening, and in high curvature regions, thereby achieving the single-atom construction of iridium species.

[0044] Example 2

[0045] The difference between this embodiment and embodiment 1 is that the anodizing voltage in step (2) is adjusted to 20V, while the other steps are the same, resulting in the sample of embodiment 2.

[0046] In this embodiment, a lower anodizing voltage corresponds to a smaller channel diameter and a higher local curvature. The resulting titanium dioxide channel structure has an average channel opening diameter of approximately 26 nm and a corresponding local curvature of approximately 0.077 nm. -1 This embodiment is used to investigate the effect of high-curvature channel interfaces on the coordination adsorption and single-atom anchoring behavior of iridium precursors.

[0047] Example 3

[0048] The difference between this embodiment and embodiment 1 is that the anodizing voltage in step (2) is adjusted to 60V, while the other steps are the same, resulting in the sample of embodiment 3.

[0049] In this embodiment, a higher anodizing voltage corresponds to a larger channel diameter and a relatively lower local curvature. The resulting titanium dioxide channel structure has an average channel opening diameter of approximately 79 nm and a corresponding local curvature of approximately 0.025 nm. -1 This embodiment is used to investigate the effect of low-curvature channel interfaces on the adsorption, enrichment, and subsequent single-atom immobilization behavior of iridium precursors.

[0050] Example 4

[0051] The difference between this embodiment and embodiment 1 is that the total number of pulse cycles in step (3) is adjusted from 900 to 450, while the other steps are the same, resulting in the sample of embodiment 4.

[0052] In this embodiment, a shorter pulse bias-induced coordination adsorption time corresponds to a lower precursor adsorption amount, which is used to investigate the effect of pulse bias treatment intensity on the iridium precursor adsorption density and subsequent single-atom anchoring effect.

[0053] Example 5

[0054] The difference between this embodiment and embodiment 1 is that the total number of pulse cycles in step (3) is adjusted from 900 to 1800, while the other steps are the same, resulting in the sample of embodiment 5.

[0055] This embodiment is used to investigate the effect of long-pulse bias-induced coordination adsorption treatment on the enrichment degree of iridium precursor on the surface of titanium dioxide channels and the subsequent single-atom construction effect.

[0056] Example 6

[0057] The difference between this embodiment and embodiment 1 is that the low-temperature solidification temperature in step (4) is adjusted from 200℃ to 150℃, while the other steps are the same, resulting in the sample of embodiment 6.

[0058] This embodiment is used to investigate the effect of low-temperature solidification temperature on the orientation fixation degree of iridium precursor and the anchoring stability of single atoms.

[0059] Comparative Example 1

[0060] The difference between this comparative example and Example 1 is that the drop-coating method was used instead of the pulse bias-induced coordination adsorption method for iridium loading. The specific steps are as follows: First, the anodized sample was calcined at 450°C for 3 hours in air. Then, a drop-coating solution was prepared: 156 μL of 0.05 mol / L chloroiridium acid solution, 24 μL of 15 mM citric acid solution, and 10 μL of Nafion solution were mixed and sonicated for 30 minutes. A total of 120 μL of the resulting drop-coating solution was added to the sample surface in 6 separate drops of 20 μL each time. The previous drop was allowed to dry before the next drop was added. After the drop-coating was completed, the sample was placed in a muffle furnace and heated to 350°C at a rate of 1°C / min. The temperature was maintained for 1 hour, and then the sample was allowed to cool naturally to obtain the sample of Comparative Example 3.

[0061] This comparative example demonstrates that, compared to the traditional drop-coating-annealing method, pulsed bias-induced coordination adsorption-low-temperature immobilization is more conducive to utilizing the curvature characteristics and surface sites of titanium dioxide channels to achieve selective adsorption and single-atom anchoring of iridium precursors, thus better aligning with the innovative theme of "curvature-controlled single-atom PEM anode materials".

[0062] Comparative Example 2

[0063] The difference between this comparative example and Example 1 is that after step (2), the anodized sample was first placed in a muffle furnace and calcined at 450°C for 3 hours in an air atmosphere to obtain a crystallized titanium dioxide channel structure; then the same pulse bias-induced coordination adsorption and low-temperature immobilization steps as in Example 1 were performed, and the rest of the operations were the same to obtain the sample of Comparative Example 2.

[0064] This comparative example is used to demonstrate that retaining the hydroxyl sites, defect sites, and incompletely crystallized interfaces on the surface of the titanium dioxide channel precursor formed after anodizing is more conducive to the selective adsorption and single-atom anchoring of the iridium precursor.

[0065] Comparative Example 3

[0066] The difference between this comparative example and Example 1 is that no pulse bias voltage is applied in step (3). The sample is simply soaked in the same adsorption solution for 45 minutes. The rest of the operation is the same, and the sample of Comparative Example 3 is obtained.

[0067] This comparative example demonstrates that pulsed bias-induced coordination adsorption can promote the directional enrichment and selective coordination adsorption of iridium precursors within titanium dioxide channels, at channel openings, and in high curvature regions, thereby improving the uniformity and stability of single-atom loading.

[0068] Comparative Example 4

[0069] The difference between this comparative example and Example 1 is that the titanium felt was replaced with a titanium sheet of the same area as the substrate. The remaining steps are the same as in Example 1, resulting in sample 4 of comparative example.

[0070] This comparative example demonstrates that, compared to planar titanium sheets, three-dimensional titanium-based porous conductive frameworks have a larger effective surface area, a richer channel spatial distribution, and better gas-liquid mass transfer conditions, making them more conducive to constructing integrated high-efficiency anode materials that can be directly used in PEM electrolyzers.

[0071] Characterization and performance testing

[0072] (1) Electron microscopy analysis

[0073] Figure 1 The image shows a SEM image of the ultra-low iridium confined loaded PEM electrode material prepared in Example 1. The results show that the nanotube structure remains relatively intact, with no obvious collapse or severe blockage. This indicates that the pulsed bias-induced coordination adsorption-low temperature immobilization method used in this invention can achieve effective loading and immobilization of ultra-low iridium species while maintaining structural stability. This is beneficial for the stable existence of active sites and the transport of reactants and desorption of products during the operation of the PEM electrolyzer.

[0074] Titanium dioxide nanotubes with different curvatures prepared in Examples 1, 2, and 3 were compared and analyzed by SEM (scanning electron microscopy). The results are as follows: Figure 2 As shown in the figure, a, b, and c correspond to Examples 2, 1, and 3, respectively. The titanium dioxide channel structures obtained under different preparation conditions exhibit significantly different channel sizes. The characteristic channel diameters of the three groups of samples are approximately 26 nm, 57 nm, and 79 nm, respectively, with corresponding local curvatures of approximately 0.077 nm. -1 0.035nm -1 and 0.025n m - 1The results show that the present invention can effectively control the channel size and local curvature of titanium dioxide by adjusting the anodic oxidation conditions, thereby constructing differentiated geometrically confined and interface-confined microenvironments on the carrier surface, providing a structural basis for the selective adsorption, directional enrichment and single-atom anchoring of iridium precursors in suitable curvature regions.

[0075] Figure 3 This is a cross-sectional SEM image of the titanium dioxide nanotubes prepared in Example 1. The present invention allows for the in-situ construction of nanotube structures with relatively complete morphology on the surface of a titanium-based framework via anodic oxidation. The cross-sectional image also shows that the channel structure has a certain lateral length, approximately 3 μm, which is beneficial for providing a larger effective interface area and space for subsequent loading of active species.

[0076] Figure 4 The image shows a TEM image of the sample prepared in Example 1. The results indicate that the sample maintains a relatively intact titanium dioxide channel morphology, with clear channel wall structures and no obvious collapse or damage. Furthermore, no large-sized iridium-containing particles were observed, indicating that iridium species are highly dispersed on the surface of the titanium dioxide channel structure. These results demonstrate that the pulsed bias-induced coordination adsorption method used in this invention is beneficial for achieving effective loading of iridium species while maintaining channel structural stability.

[0077] Figure 5 This is a cross-sectional SEM image of the PEM membrane electrode of the present invention after hot-press assembly. As can be seen from the image, the resulting MEA has a clear layered composite structure, with tight adhesion between the membrane layers and the electrode layers, continuous interfaces, and no obvious large-area delamination or macroscopic voids, indicating that the anode material prepared by the present invention can achieve good bonding with the proton exchange membrane. Meanwhile, the underlying three-dimensional porous conductive framework retains its porous fiber network characteristics, which is beneficial for maintaining the structural stability of the membrane electrode and its electron conduction and mass transfer performance during operation.

[0078] (2) XRD analysis

[0079] Figure 6 The image shows the XRD pattern of the iridium single-atom supported titanium dioxide channel structure PEM anode material prepared in Example 1.

[0080] Depend on Figure 6 As can be seen, the sample mainly exhibits titanium-based framework and titanium dioxide-related diffraction peaks. No obvious characteristic peaks of metallic iridium or iridium oxide crystal phases were observed, indicating that no detectable large-sized iridium-containing crystalline particles were formed in the sample. This shows that the iridium species are highly dispersed on the surface of the titanium dioxide channel structure, thus demonstrating that the present invention has successfully prepared titanium dioxide-confined iridium single-atom PEM anode material.

[0081] (3) PEM electrode testing

[0082] To evaluate the practical application performance of the anode material obtained in this invention in a proton exchange membrane electrolyzer, the samples obtained in Example 1 and Comparative Example 1 were used as integrated anode electrodes to assemble PEM single cells for testing. The proton exchange membrane used was Nafion 115, the test temperature was 60°C, and pure water was used as the feed to the anode side. The cell voltage response of different samples under PEM water electrolysis conditions was compared by recording the single-cell polarization curves.

[0083] Figure 7 The graphs show the polarization curves of Example 1 and Comparative Example 1 in a PEM single cell. Figure 7 It can be seen that Example 1 still exhibits good PEM electrolysis activity under ultra-low iridium loading conditions, where the iridium loading on the anode side is only 0.11 mg. Ir cm -2 Under conditions of 60℃ and pure water feed, when the current density is 1A cm⁻¹ -2 At that time, the corresponding electrolytic cell voltage was 1.67V; when the current density was 2Acm⁻¹ -2 At that time, the corresponding electrolytic cell voltage was 1.8V. The above results show that the present invention, by constructing an ultra-low iridium electrode material in situ on the surface of a three-dimensional titanium-based porous conductive framework, further achieves a highly dispersed and confined load of iridium active centers. While significantly reducing the amount of precious metals used, it can still maintain good single-cell oxygen evolution reaction performance and device-level output capability.

[0084] (4) Stability test of PEM electrolyzer

[0085] Figure 8 The PEM anode material obtained in Example 1 at 1Acm -2 The results of single-cell stability tests under constant current conditions. Figure 8 It can be seen that, in Example 1, the tank voltage remained stable throughout the 1050 hours of continuous operation, with a voltage decay rate of less than 32 μVh. -1 The results demonstrate good long-term operational stability. This indicates that the three-dimensional titanium-based porous conductive framework and iridium active centers constructed in this invention can maintain good interfacial bonding strength and structural integrity under PEM electrolyzer operating conditions, while also ensuring electron conduction, water and oxygen transport, and stable anchoring of the active centers, thus showing good prospects for practical applications.

[0086] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing an in-situ constructed ultra-low iridium confined supported PEM electrode material, characterized in that, Includes the following steps: S1. The three-dimensional titanium-based porous conductive framework is cleaned sequentially with acetone, ethanol and deionized water, then placed in an acid solution to remove the surface oxide layer, washed and dried to obtain the pretreated titanium-based framework. S2. Using the pretreated titanium-based framework as the anode, an inert conductive material as the cathode, and a mixed solution containing ammonium fluoride, deionized water, and ethylene glycol as the electrolyte, the pretreated titanium-based framework is subjected to constant-voltage anodic oxidation to obtain a titanium dioxide precursor with a nanotube morphology. S3. The titanium dioxide precursor obtained in step S2 is placed as the working electrode in an adsorption solution containing iridium precursor. The first induced coordination adsorption treatment is carried out under the action of pulse bias voltage, so that the iridium precursor is selectively adsorbed in the titanium dioxide channel, at the tube opening, in the high curvature region and on the surface active site. S4. The sample after step S3 is subjected to a first low-temperature immobilization treatment; optionally, the sample after the first low-temperature immobilization treatment is placed in the adsorption solution for a second and subsequent pulse bias-induced coordination adsorption treatment, and then subjected to the corresponding low-temperature immobilization treatment. S5. After the low-temperature solidification treatment is completed, the material is naturally cooled to obtain the in-situ constructed titanium dioxide channel confined iridium single-atom PEM anode material with adjustable curvature.

2. The preparation method according to claim 1, characterized in that, In step S1, the three-dimensional titanium-based porous conductive skeleton is one of titanium felt, titanium mesh or titanium foam; the skeleton thickness is 0.1-1.0 mm, preferably 0.2-0.8 mm; the cleaning time is 3-15 min, preferably 5 min; the acid solution is one or more of hydrochloric acid, nitric acid or sulfuric acid, the acid concentration is 5%-20%, and the treatment time is 10-30 min.

3. The preparation method according to claim 1, characterized in that, In step S2, the electrolyte is composed of 0.1-0.5g ammonium fluoride, 3-10mL deionized water and 30-50mL ethylene glycol; the anodic oxidation voltage is 20-60V and the anodic oxidation time is 1-3h; preferably, the anodic oxidation voltage is 20-50V, more preferably 40V, and the anodic oxidation time is 2h.

4. The preparation method according to claim 1, characterized in that, In step S3, the adsorption solution contains an iridium precursor, a solvent, and an optional acid adjuster; the iridium precursor is one or more of chloroiridium acid, iridium chloride, and iridium complex, preferably chloroiridium acid; the concentration of the iridium precursor in the adsorption solution is 0.1–10 mg / mL, preferably 0.5–5 mg / mL; the acid adjuster is hydrochloric acid, and the concentration of hydrochloric acid is 0.001–0.05 mol / L, preferably 0.005–0.02 mol / L; the solvent is water, ethanol, or a water / ethanol mixture.

5. The preparation method according to claim 1, characterized in that, In step S3, the pulse bias-induced coordination adsorption treatment uses the sample obtained in step S2 as the working electrode, an inert conductive material as the counter electrode, and optionally a reference electrode to form an electrochemical system. The pulse bias is one of square wave pulse, step pulse, cathode bias pulse, anode bias pulse, or alternating anode and cathode pulse, preferably an alternating anode and cathode pulse. The peak potential of the pulse bias is -0.5 to 1.5 V, the duration of a single pulse is 0.01 to 10 s, the pulse interval is 0.01 to 30 s, and the total number of cycles is 10 to 5000, preferably 100 to 3000.

6. The preparation method according to claim 6, characterized in that, The pulse bias-induced coordination adsorption treatment temperature is 10–60℃, preferably 20–40℃; the treatment time is 1–120 min, preferably 5–60 min; under the action of pulse bias, the iridium precursor preferentially undergoes selective coordination adsorption at the orifice region, high curvature region, defect site, hydroxyl site and oxygen coordination site of the titanium dioxide channel.

7. The preparation method according to claim 1, characterized in that, The low-temperature immobilization treatment in step S4 is carried out in a tube furnace under an atmosphere of argon, nitrogen, or a mixture thereof; the heating rate is 0.5–2 °C / min, the low-temperature immobilization temperature is 120–250 °C, and the holding time is 0.5–3 h; preferably, the heating rate is 1 °C / min, the low-temperature immobilization temperature is 150–220 °C, and the holding time is 1–2 h; steps S3 and S4 constitute a cyclic "pulse bias-induced coordination adsorption-low-temperature immobilization" process, with 1–5 cycles, preferably 2–3 cycles; the method of multiple induced adsorption and stepwise immobilization is adopted to gradually increase the anchoring density of iridium active centers and inhibit the migration, aggregation, and granulation of iridium species.

8. An in-situ constructed titanium dioxide channel-confined iridium single-atom PEM anode material with adjustable curvature, characterized in that, It is prepared by the method according to any one of claims 1 to 7, wherein the PEM anode material comprises a three-dimensional titanium-based porous conductive framework, a titanium dioxide channel structure grown in situ on the surface of the three-dimensional titanium-based porous conductive framework, and iridium single-atom active centers dispersed and confined in the titanium dioxide channels, at the orifice, in the high curvature region and on the surface active sites.

9. The PEM anode material according to claim 8, characterized in that, The titanium dioxide channel structure is an array structure with a nanotube morphology. The iridium single atoms are preferentially anchored at the defect sites, hydroxyl sites, oxygen coordination sites, and high curvature regions of the titanium dioxide channel. The anode material can be directly used as the anode in a proton exchange membrane water electrolysis device without the need for additional catalyst coating and binder.

10. The application of the in-situ constructed, curvature-adjustable titanium dioxide channel-confined iridium single-atom PEM anode material as described in claim 8 or 9 in proton exchange membrane electrolysis of water, characterized in that... The anode material is used as the anode material of the PEM electrolyzer or the PEM membrane electrode for the oxygen evolution reaction on the anode side.

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