PdIr / PdO catalyst and preparation method thereof
By using PdO support and PdIr alloy catalyst, the agglomeration problem of Ir-based catalysts in acidic oxygen evolution reaction was solved, and a catalyst with high activity, high stability and low Ir loading was achieved, which improved the efficiency and stability of hydrogen production by water electrolysis.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-26
- Publication Date
- 2026-03-31
AI Technical Summary
Existing Ir-based catalysts suffer from agglomeration problems in acidic oxygen evolution reactions, leading to a reduction in active sites and a decrease in reaction rate. Furthermore, Ir resources are scarce and expensive, making large-scale application difficult.
The catalyst, which uses PdO as a support and PdIr alloy as the active component, avoids particle contact by using a molten salt barrier agent, adjusts the particle surface charge and interfacial tension, promotes interfacial bonding, and inhibits agglomeration.
This resulted in a catalyst with high activity, high stability, and low Ir loading, which improved the catalyst's reaction performance and stability while reducing production costs.
Smart Images
Figure CN121760001A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of water electrolysis for hydrogen production technology, specifically relating to a PdIr / PdO catalyst and its preparation method. Background Technology
[0002] Hydrogen energy, as a clean and efficient secondary energy carrier, occupies a core position in the global energy structure transition towards a low-carbon model. Proton exchange membrane electrolysis (PEMWE) technology, with its advantages of high gas purity, fast response speed, and high energy conversion efficiency, has become a key technological path for the large-scale production of green hydrogen. However, the oxygen evolution reaction (OER) at the PEMWE anode suffers from high kinetic barriers and harsh reaction conditions, requiring a highly efficient catalyst. Currently, Ir-based catalysts are the mainstream choice in this field due to their excellent catalytic activity and stability in acidic OERs. However, Ir is extremely scarce in the Earth's crust and expensive, and pure Ir catalysts are prone to particle agglomeration and excessive oxidation during long-term operation, leading to activity decay, which severely restricts the commercialization of PEMWE technology.
[0003] To overcome the aforementioned bottlenecks, the industry has developed a variety of strategies to improve the performance of Ir-based catalysts: introducing transition metals or other platinum group metals through alloying to optimize the electronic structure of Ir by utilizing electronic synergy, thereby reducing the activation energy of the reaction and reducing the amount of Ir used; using highly stable supports to improve the dispersion of Ir and enhance metal-support interactions to suppress agglomeration; and regulating catalyst morphology to increase the exposure of active sites.
[0004] During catalyst preparation, agglomeration causes many active sites that were originally exposed in the reaction medium to be covered by other catalyst particles, preventing them from fully contacting the reactant water molecules. Agglomerated catalyst particles form larger aggregates, hindering the diffusion of reactants into the catalyst interior and the escape of products. This slows down the reaction rate, requiring higher overpotentials to maintain a certain current density, thus reducing hydrogen production efficiency. Although the total amount of agglomerated catalyst remains unchanged, the effective surface area available for catalytic reaction is significantly reduced, resulting in a significant decrease in the activity per unit mass of catalyst. Reducing agglomeration during catalyst preparation is a key breakthrough in its technology.
[0005] However, existing methods still have limitations. First, alloying is prone to structural collapse due to selective metal dissolution, resulting in limited improvement in stability. Second, support modification may introduce mass transfer resistance or weaken the intrinsic activity of active sites. Third, the preparation processes for complex morphologies mostly rely on high-end equipment, which is costly and difficult to scale up. Therefore, developing a method for preparing Ir-based catalysts that can simultaneously achieve high activity, high stability, low Ir loading, and easy industrial production has become the key to a technological breakthrough for PEMWE. Summary of the Invention
[0006] To address the shortcomings of existing technologies, this invention provides a PdIr / PdO catalyst and its preparation method.
[0007] The catalyst of this invention uses in-situ generated PdO as a support and PdIr alloy as the active metallic component, promoting interfacial bonding between the PdIr alloy and the PdO support, thereby improving catalyst activity and stability while reducing the loading of the noble metal Ir. The preparation method of this invention uses molten salt as a barrier agent to prevent direct particle contact and fusion; it also adjusts the surface charge and interfacial tension of the particles, weakening the driving force for particle agglomeration.
[0008] To achieve the aforementioned objectives of improving catalyst activity and stability, reducing the loading of the noble metal Ir, and weakening the driving force for interparticle agglomeration during catalyst preparation, this invention provides the following technical solution: A PdIr / PdO catalyst, the catalyst composition comprising: PdO and PdIr alloy, wherein the catalyst uses PdO as a support and the PdIr alloy metal active component is supported on the PdO support.
[0009] Furthermore, the PdIr alloy and the PdO are integrally formed using an in-situ method, and the PdIr... The loading of PdO on the alloy is 30wt%~60wt%, and the atomic molar ratio of Pd to Ir in the PdIr alloy is 1:1~0.5.
[0010] A method for preparing a PdIr / PdO catalyst, the method being used to prepare the PdIr / PdO catalyst according to claim 1 or 2, the method comprising the following steps: S1. Weigh out the required iridium source, palladium source and molten salt in the required stoichiometric ratio, and grind and mix them. S2. The ground mixture is calcined under a carbon dioxide atmosphere to obtain a solid powder containing impurities; S3. Disperse the obtained impurity-containing solid powder in sulfuric acid solution, stir and acid wash, centrifuge, and vacuum separate. After drying, the purified solid powder was collected to obtain the PdIr / PdO catalyst.
[0011] Further, in step S1 of the preparation method, the iridium source is one or more of the following: IrCl3·xH2O, IrCl3, H2IrCl6, Ir(acac)3, K3IrCl6, and K2IrCl6; the palladium source is one or more of the following: PdCl2, Pd(NO3)2, and K2PdCl6; and the molten salt is one or more of the following: KNO3, NaNO3, KCO3, NaCO3, K2SO4, Na2SO4, NaCl, and KCl.
[0012] Further, in step S1 of the preparation method, the total mass of the molten salt, iridium source, and palladium source is... The mass ratio is 1:3 to 3:1.
[0013] Furthermore, in step S1 of the preparation method, the molar ratio of the iridium source to the palladium source is 1:1 to 1:5.
[0014] Furthermore, in step S1 of the preparation method, the grinding and mixing time is 10 minutes or more. The particle size of the ground mixture is 50~100um.
[0015] Furthermore, in step S2 of the preparation method, the calcination is performed by heating from room temperature to the calcination temperature and then holding the temperature, the heating rate is 1~5℃ / min, the calcination temperature is 350~600℃, and the holding time is 0.5~4h.
[0016] Furthermore, in step S3 of the preparation method, the acid washing time is 1-6 hours, and the sulfuric acid concentration is... The speed ranges from 0.1 to 1 meter.
[0017] Preferably, the preparation method of the PdIr / PdO catalyst includes the following steps: S1. Weigh K2IrCl6 and K2PdCl6 with an iridium and palladium molar ratio of 1:2, and weigh K2CO3 with a mass ratio of 1:1 to the total mass of the iridium and palladium sources. Grind thoroughly for more than 10 minutes. S2. Place the mixture from step S1 in a CO2 atmosphere in a tube furnace, heat it to 400°C at a heating rate of 5°C / min and hold it at that temperature for 1 hour, then let it cool naturally to room temperature to obtain a solid powder containing impurities. S3. After cooling the impurity-containing solid powder obtained in step S2, acid wash it with 50 mL of 0.5 M H2SO4 at 80 °C for 3 h, and then vacuum dry it at 60 °C to obtain the PdIr / PdO catalyst.
[0018] Compared with existing technologies, the present invention provides a PdIr / PdO catalyst and its preparation method, which has the following beneficial effects: First, this invention uses molten salt as a barrier agent. On the one hand, molten salt is liquid at high temperatures, which can uniformly encapsulate and disperse the reactants, forming a "liquid-phase mass transfer environment" and preventing direct contact and fusion of particles. On the other hand, molten salt ions can be adsorbed on the surface of oxide particles, regulating the surface charge and interfacial tension of the particles and weakening the driving force for particle agglomeration. This simple and mild method successfully synthesized a highly alloyed and uniformly dispersed small-particle-size PdIr / PdO catalyst.
[0019] Secondly, this invention utilizes in-situ generated PdO as a support and PdIr alloy as the active metal component, successfully synthesizing a highly alloyed and uniformly dispersed PdIr / PdO catalyst using a simple and mild method. The introduction of PdO promotes interfacial bonding between the PdIr alloy and the PdO support through metal-support interaction, constructing a strong metal-support interaction. This optimizes the electronic structure of Ir and inhibits the dissolution of metal particles. It also suppresses the aggregation and dissolution of PdIr nanoparticles during the reaction process, successfully achieving a synergistic improvement in the activity and stability of PdIr sites. Attached Figure Description
[0020] Figure 1 This is a process flow diagram of the preparation method of the PdIr / PdO catalyst of the present invention; Figure 2 This is a high-resolution transmission electron microscope (HRTEM) image of the PdIr / PdO catalyst prepared in Example 1 of the present invention. Figure 3 The image shows the X-ray diffraction (XRD) pattern of the PdIr / PdO catalyst prepared in Example 1 of this invention. Figure 4 Linear sweep voltammetry (LSV) curves of the PdIr / PdO catalysts prepared in Examples 1 and 6 of this invention; Figure 5 The PdIr / PdO catalysts prepared in Examples 1 and 6 of this invention were tested at 10 mA / cm². -2 Electrochemical lifetime test graph below; Figure 6 The polarization curve of the membrane electrode prepared in specific embodiment 1 of the present invention is shown. Figure 7 This is a stability test diagram of the membrane electrode prepared in Specific Embodiment 1 of the present invention. Detailed Implementation
[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.
[0022] Example 1 This embodiment provides a method for preparing a PdIr / PdO catalyst, which includes the following steps: S1. Weigh 100 mg K2IrCl6, 100 mg K2PdCl6, and 0.2 g K2CO3, and grind them thoroughly for at least 10 minutes. S2. Place the mixture from step S1 in a CO2 atmosphere in a tube furnace, heat it to 400°C at a heating rate of 5°C / min and hold it at that temperature for 1 hour, then allow it to cool naturally to room temperature to obtain a solid powder containing impurities. S3. After cooling the impurity-containing solid powder obtained in step S2, acid wash it with 50 mL of 0.5 M H2SO4 at 80 °C for 3 h to remove excess potassium carbonate and unreacted Pd salt, and then vacuum dry it at 60 °C to obtain the PdIr / PdO catalyst.
[0023] Catalyst performance test results: See Figure 2 The image shows an HRTEM image of the PdIr / PdO catalyst prepared in Example 1. As can be seen from the image, Example 1 successfully prepared a uniformly distributed ultra-small PdIr / PdO catalyst with a particle size of about 2 nm.
[0024] See Figure 3 The image shows the XRD pattern of the PdIr / PdO catalyst prepared in Example 1.
[0025] Electrochemical performance evaluation The PdIr / PdO catalyst prepared in Example 1 above was applied to the acidic water electrolysis oxygen evolution reaction, and its electrochemical performance was evaluated. The specific methods included the following: A1. Mix 3 mg of catalyst, 10 μL of 5% perfluorosulfonic acid (Nafion) solution, 750 μL of isopropanol and 250 μL of ultrapure water, and sonicate for 1 h to prepare an electrochemical test ink solution. A2. Select a glassy carbon electrode tip (GC) with a diameter of 5mm and an area of 0.196cm². 2 ), 15 μL of ink solution was added to the pre-polished GC, and allowed to air dry to form the test electrode. At this point, the Ir loading was 150 μg·cm⁻¹. -2 ; A3. The oxygen evolution performance of the test electrode in water electrolysis was tested. Specifically, a 0.5M H2SO4 solution was placed in a five-cell electrolytic cell, and N2 was introduced for half an hour to saturate the solution. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) tests were then performed. The scan rate for the CV test was 50 mVs. -1 The scan was performed until the CV curve coincided, with a voltage range of 0.7~1.5V / RHE; during linear scan testing, the scan speed was 5 mVs. -1 The scanning range was 1.2~1.7V / RHE; then, at a current density of 10mA / cm², the scanning range was... -2 Electrochemical lifetime testing was then conducted.
[0026] See test results Figure 4 and Figure 5 ,Depend on Figure 4 It can be seen that the PdIr / PdO catalyst prepared in the examples exhibits good performance at 10 mA / cm². -2 The overpotential is 285mV; by Figure 5 It can be seen that the PdIr / PdO catalyst prepared in Example 1 has excellent stability and no significant degradation after 240 hours of constant current.
[0027] Example 2 This embodiment provides a method for preparing a PdIr / PdO catalyst, which differs from that of Example 1 in that: in step S1, the iridium source and palladium source are IrCl3·xH2O and PdCl2, respectively, and the mass ratio of molten salt to noble metal salt precursor is 1:3; in step S2, the calcination temperature is 500℃; in step S3, the acid washing time is 6h; other steps and methods are the same as in Example 1, and will not be repeated here.
[0028] Example 3 This embodiment provides a method for preparing a PdIr / PdO catalyst. The difference between this method and that of Example 1 is that the iridium source and palladium source in step S1 are K3IrCl6 and Pd(NO3)2, respectively; the heating rate in step S2 is 1℃ / min; the acid washing concentration in step S3 is 0.1 M; and the other steps and methods are the same as in Example 1, and will not be repeated here.
[0029] Example 4 This embodiment provides a method for preparing a PdIr / PdO catalyst. The difference between this method and that of Example 1 is that the molten salt in step S1 is a combination of NaNO3 and NaCl; the calcination temperature in step S2 is 350℃ and the holding time is 2h; the acid washing concentration in step S3 is 1 M and the acid washing time is 0.5h; other steps and methods are the same as in Example 1 and will not be repeated here.
[0030] Example 5 This embodiment provides a method for preparing a PdIr / PdO catalyst, which differs from that in Example 1 in that: the molten salt in step S1 is KNO3, and the mass ratio of the molten salt to the noble metal salt precursor is 1:3; the heating rate in step S2 is 2℃ / min, and the calcination temperature is 600℃; the acid washing time in step S3 is 2h; other steps and methods are the same as in Example 1, and will not be repeated here.
[0031] Example 6 This embodiment is a comparative embodiment, which provides a method for preparing a PdIr / PdO catalyst. The difference between this method and that of Embodiment 1 is that no molten salt is added in step S1; the other steps and methods are the same as those of Embodiment 1, and will not be repeated here.
[0032] The effect data of Examples 1 to 6 above are shown in Table 1.
[0033] Table 1 Particle size (nm) Pd, Ir atomic ratio PdIr loading on PdO (wt%) Overpotential (mV) Stability (h) Example 1 2.2 1:1 45 285 240 Example 2 3.5 1:0.6 35 298 120 Example 3 3.0 2:1 40 302 180 Example 4 2.5 1:0.8 60 290 100 Example 5 4.3 1:0.7 30 301 200 Example 6 5.1 1:1 30 300 75 Table 1 shows that changing the type and feed ratio of the Ir source, Pd source, and molten salt, as well as the calcination and acid washing conditions, all affect the final catalyst particle size, activity, and stability. In Example 6, without molten salt, the particle size was the largest, demonstrating the irreplaceable role of molten salt in the synthesis process. Different PdIr loadings resulted in significant differences in catalyst activity and stability. This is because the interaction between the PdO support and PdIr varies with the loading. Lower loadings lead to insufficient interaction between the metal and the support, resulting in low activity, while higher loadings reduce the interparticle distance, potentially causing agglomeration. The interaction between the metal and support is strongest when the noble metal loading is 45%, resulting in optimal activity and stability.
[0034] As shown in Table 1, the catalyst prepared in Example 1 has good performance. The catalyst prepared in Example 1 is further processed into a film electrode, and the preparation method includes the following steps: B1. Take 20 mg of the PdIr / PdO catalyst prepared in Example 1, add water and isopropanol in a mass ratio of 15:15:1, then add 20% Nafion membrane solution, and sonicate for 1 hour to obtain anode catalyst ink. Spray the anode catalyst ink onto the surface of the proton exchange membrane. B2. Take 20 mg of Pt / C catalyst (Pt content is 60 wt%), add water and isopropanol in a mass ratio of 15:15:1 to Pt / C catalyst, then add 20% Nafion membrane solution, wherein the mass of Nafion resin is 20% of the mass of Pt / C catalyst. After sonication for 1 hour, obtain cathode catalyst ink. Spray the cathode catalyst ink onto the other side of the above proton exchange membrane to finally obtain a low noble metal loading water electrolysis membrane electrode.
[0035] The catalyst loading in the membrane electrode prepared by the catalyst in Example 1 was determined by gravimetric analysis, and the Ir loading in the membrane electrode was measured to be 0.6 mg / cm³. 2 .
[0036] The prepared membrane electrodes were applied to the proton exchange membrane water electrolysis catalytic reaction. Each membrane electrode was placed in a small water electrolysis fixture, with the anode immersed in 65°C deionized pure water. The entire system was maintained at 65°C, and the current density for water electrolysis was set to 0–3 A / cm². 2 Tests were conducted to obtain the polarization curves of each membrane electrode for water electrolysis. (Refer to...) Figure 6 As shown, by Figure 6 It can be seen that the PdIr / PdO catalyst maintains excellent activity even with ultra-low iridium loading. The PdIr / PdO membrane electrode catalyst prepared by the catalyst in Example 1 exhibits excellent activity at 3 A / cm². 2 The cell voltage at 65°C is only 1.741V; this indicates that the membrane electrode prepared by the PdIr / PdO catalyst in Example 1 can effectively improve the utilization rate of the water electrolysis catalyst and improve the reaction performance. That is, the PdIr / PdO catalyst prepared in Example 1 has high catalytic activity and high metal utilization.
[0037] The membrane electrode prepared with the catalyst from Example 1 was applied to the proton exchange membrane water electrolysis catalytic reaction. The membrane electrode was placed in a small water electrolysis fixture, and stability tests were conducted at 65°C. During the tests, ultrapure water was passed through the anode, and the current density was set to 2 A / cm². 2 The stability test results are available in the reference section. Figure 7 As shown, by Figure 7 It can be seen that the PdIr / PdO catalyst at 2 A / cm 2 It can run stably for at least 1000 hours.
[0038] It should be noted that, in this document, terms such as "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A PdIr / PdO catalyst, characterized in that: The catalyst composition includes PdO and PdIr alloy, wherein the catalyst uses PdO as a support and the PdIr alloy metal active component is loaded on the PdO support.
2. The PdIr / PdO catalyst according to claim 1, characterized in that: The loading of PdO on the PdIr alloy is 30wt%~60wt%, and the atomic molar ratio of Pd to Ir in the PdIr alloy is 1:1~0.
5.
3. A method for preparing a PdIr / PdO catalyst, wherein the method is used to prepare the PdIr / PdO catalyst according to claim 1 or 2, characterized in that: The PdIr alloy and the PdO are integrally prepared using an in-situ method, and the preparation method includes the following steps: S1. Weigh out the required iridium source, palladium source and molten salt in the required stoichiometric ratio, and grind and mix them. S2. The ground mixture is calcined under a carbon dioxide atmosphere to obtain a solid powder containing impurities; S3. Disperse the obtained impurity-containing solid powder in sulfuric acid solution, stir and acid wash, centrifuge, vacuum dry and collect the purified solid powder to obtain the PdIr / PdO catalyst.
4. The method for preparing the PdIr / PdO catalyst according to claim 3, characterized in that: In step S1 of the preparation method, the iridium source is one or more of the following: IrCl3·xH2O, IrCl3, H2IrCl6, Ir(acac)3, K3IrCl6, and K2IrCl6; the palladium source is one or more of the following: PdCl2, Pd(NO3)2, and K2PdCl6; and the molten salt is one or more of the following: KNO3, NaNO3, KCO3, NaCO3, K2SO4, Na2SO4, NaCl, and KCl.
5. The method for preparing the PdIr / PdO catalyst according to claim 3, characterized in that: In step S1 of the preparation method, the mass ratio of the molten salt to the total mass of the iridium source and palladium source is 1:3 to 3:
1.
6. The method for preparing the PdIr / PdO catalyst according to claim 3, characterized in that: In step S1 of the preparation method, the molar ratio of iridium to palladium in the iridium source and palladium source is 1:1 to 1:
5.
7. The method for preparing the PdIr / PdO catalyst according to claim 3, characterized in that: In step S1 of the preparation method, the grinding and mixing time is more than 10 minutes, and the particle size of the mixture after grinding is 50~100um.
8. The method for preparing the PdIr / PdO catalyst according to claim 3, characterized in that: In step S2 of the preparation method, the calcination is performed by heating from room temperature to the calcination temperature and then holding the temperature, with a heating rate of 1~5℃ / min, a calcination temperature of 350~600℃, and a holding time of 0.5~4h.
9. The method for preparing the PdIr / PdO catalyst according to claim 3, characterized in that: In step S3 of the preparation method, the pickling time is 1-6 hours and the sulfuric acid concentration is 0.1-1 M.
10. The method for preparing the PdIr / PdO catalyst according to any one of claims 3 to 9, characterized in that: The preparation method includes the following steps: S1. Weigh K2IrCl6 and K2PdCl6 with an iridium and palladium molar ratio of 1:2, and weigh K2CO3 with a mass ratio of 1:1 to the total mass of the iridium and palladium sources. Grind thoroughly for more than 10 minutes. S2. Place the mixture from step S1 in a CO2 atmosphere in a tube furnace, heat it to 400°C at a heating rate of 5°C / min and hold it at that temperature for 1 hour, and then cool it naturally to room temperature to obtain a solid powder containing impurities. S3. After cooling the impurity-containing solid powder obtained in step S2, acid wash it with 50 mL of 0.5 M H2SO4 at 80 °C for 3 h, and then vacuum dry it at 60 °C to obtain the PdIr / PdO catalyst.