A palladium-iridium-based ultrathin two-dimensional alloy nanosheet electrocatalyst and its preparation method
By preparing palladium-iridium-based ultra-thin two-dimensional alloy nanosheet materials, the problems of low activity and poor stability of existing platinum-based catalysts have been solved, and the electrocatalytic performance improvement of efficient and anti-toxicity is achieved.
Patent Information
- Application Number
- CN202310819631.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-07-05
- Publication Date
- 2025-07-11
- Estimated Expiration
- 2043-07-05
AI Technical Summary
The existing platinum-based hydrogen conversion electrocatalysts have low catalytic activity and poor stability, are easily toxic to carbon monoxide in hydrogen, and lack efficient material synthesis strategies to achieve high-performance electrocatalysis with accurate and controllable sites.
The palladium-iridium-based ultrathin two-dimensional alloy nanosheet materials were synthesized by wet chemistry. By adjusting the proportion of elements of Pd, Ir, Ru, Mo, and Pt, ultrathin two-dimensional alloy nanosheets with uniform size and atomic thickness were prepared for hydrogen conversion electrocatalysis.
It realizes an electrocatalyst with high specific surface area, flexible and adjustable components, and excellent anti-toxicity performance, improving the performance of electrolytic hydrogen evolution reaction and fuel cell hydroxide reaction.
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Figure CN116885221B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical fields of new energy and new materials, and particularly relates to a palladium-iridium-based ultrathin two-dimensional alloy nanosheet electrocatalyst and a preparation method thereof. Background Art
[0002] With the increasing severity of the current world energy crisis and environmental pollution problems, the global energy structure is transforming towards green, low-carbon, and high-efficiency directions. Hydrogen energy has a high energy density and is environmentally friendly. It is one of the ideal energy conversion media and can be used as a new energy carrier to support the large-scale development of renewable energy, providing an ultimate solution for achieving the dual-carbon goal. The core industrial technologies involved in the development of the hydrogen energy economy include upstream hydrogen production and downstream hydrogen utilization. Among them, electrolytic water hydrogen production technology can achieve high-efficiency hydrogen production with environmental protection, and fuel cell-related technologies represented by hydrogen fuel cells can achieve the efficient utilization of green hydrogen in various fields such as aerospace and military transportation. The cooperation of the two realizes the efficient conversion of electrical energy and chemical energy, which is of great significance for vigorously developing the hydrogen energy economy.
[0003] Benefiting from high catalytic efficiency, excellent cold start performance, and low cost, anion exchange membrane electrolytic water and fuel cell devices have received extensive attention. However, the hydrogen conversion electrocatalytic reactions involved therein (hydrogen evolution reaction HER in electrolytic water and hydrogen oxidation reaction HOR in fuel cells) have slow kinetics and rely on high-loading platinum-based noble metal catalysts, which bring double constraints on cost and performance to the development of this field. Existing platinum-based hydrogen conversion electrocatalysts have low catalytic activity and poor stability, and are easily poisoned and inactivated by trace carbon monoxide contained in hydrogen. Therefore, there is an urgent need to develop low-platinum hydrogen conversion electrocatalytic materials with high activity, high stability, and high CO poisoning resistance.
[0004] Palladium (Pd) is a homologous element of platinum (Pt), having similar physical and chemical properties and valence electron structures to platinum, and is more abundant in the earth's crust. It is currently the most ideal alternative catalyst; iridium (Ir) has high intrinsic catalytic activity for HOR, and there is a strong ligand effect with palladium. It can not only effectively modulate the d-band electronic structure of palladium, optimize the hydrogen adsorption energy to improve the hydrogen conversion catalytic activity, but also enhance its poisoning resistance through the dilution effect; ruthenium (Ru), as a middle transition metal element, is an excellent bifunctional electrocatalyst for HER / HOR and has strong oxygen affinity, which can further adjust the hydroxyl adsorption energy. However, in existing ruthenium-based catalysts, Ru atoms are easily oxidized to inactive ruthenium dioxide, and the hydrogen conversion electrocatalytic performance cannot meet the long-term working conditions. At the same time, there are few studies on the structure-activity relationship of real active sites in hydrogen conversion electrocatalysis, and there is a lack of general and effective material synthesis strategies for efficient HER / HOR electrocatalysis with precise and controllable sites.
[0005] In summary, it is of great significance both scientifically and engineeringly to invent a simple, efficient and novel preparation method of high-performance palladium-iridium (ruthenium)-based hydrogen conversion electrocatalysts to improve the electrocatalytic performance of hydrogen conversion. Summary of the Invention
[0006] The main object of the present invention is to provide a palladium-iridium-based ultrathin two-dimensional alloy nanosheet hydrogen conversion electrocatalyst and a preparation method thereof; the two-dimensional PdIr-based hydrogen conversion electrocatalytic material prepared by this method has the characteristics of high specific surface area, flexible adjustable composition, high intrinsic catalytic activity, excellent anti-poisoning performance, etc.
[0007] To achieve the above object, the present invention adopts the following technical solutions:
[0008] A palladium-iridium-based ultrathin two-dimensional alloy nanosheet material for hydrogen conversion electrocatalysis, the composition of which is adjustable from binary (PdIr) to quinary (PdIrRuMoPt), and the general formula of the multi-component is Pd x Ir y M z , where M is selected from one or more of the three elements of platinum, molybdenum, and ruthenium, x + y + z = 1, 0.3 ≤ x ≤ 0.6, 0.1 ≤ y ≤ 0.5, 0 ≤ z ≤ 0.6; the ultrathin two-dimensional alloy nanosheet material is a circular or polygonal thin sheet with a size of 30 - 40 nm and a thickness of 0.8 - 1.2 nm.
[0009] Furthermore, the proportion of each element in the palladium-iridium-based ultrathin two-dimensional alloy nanosheet material is adjustable. The molar percentage of the Pd element ranges from 30% to 60%, the molar percentage of the Ir element ranges from 10% to 50%, the molar percentage of the Ru element ranges from 0 to 40%, the molar percentage of the Mo element ranges from 0 to 20%, and the molar percentage of the Pt element ranges from 0 to 10%.
[0010] The present invention also provides a preparation method of the above palladium-iridium-based ultrathin two-dimensional alloy nanosheet material. The metal precursor salt, carbonyl-based reducing agent and inorganic salt structure inducer are mixed in a specific organic solvent, and slowly heated to a certain temperature (220 - 230 °C) for reaction, and then washed and dispersed to obtain palladium-iridium-based alloy nanosheets with an ultrathin two-dimensional structure.
[0011] Among them, the metal precursor salts include: palladium acetylacetonate, platinum acetylacetonate, ruthenium acetylacetonate, dodecacarbonyltetrairidium and hexacarbonylmolybdenum; the carbonyl-based reducing agent is preferably a combination of dodecacarbonyltetrairidium and hexacarbonylmolybdenum; the inorganic salt structure inducer is preferably ammonium bromide; the organic solvent is preferably oleylamine.
[0012] It should be noted that only when Pt is present, Mo in hexacarbonylmolybdenum and Ru in ruthenium acetylacetonate can be doped into the palladium-iridium-based alloy nanosheets.
[0013] Specifically, the preparation method of the above-mentioned palladium-iridium-based ultrathin two-dimensional alloy nanosheet material may include the following steps:
[0014] (1) First, weigh a certain amount of precursor salts of each metal element, carbonyl-based reducing agents, and inorganic salt structure inducing agents into a dry, clean, and pressure-resistant bottle, add a certain amount of organic solvent, seal it, and heat it at 50°C - 70°C with the rotation speed controlled at 200 - 350 rmp for 40 - 60 min. After all the raw materials are dissolved, a homogeneous precursor mixed solution is obtained;
[0015] (2) Slowly raise the temperature of the precursor mixed solution to 220 - 230°C at a heating rate not exceeding 6°C / min, adjust the rotation speed to 150 - 300 rmp, and keep it warm for 3 - 6 h to obtain a black colloidal liquid;
[0016] (3) After the obtained colloidal liquid is naturally cooled to room temperature, add cyclohexane solvent or a mixed solvent of cyclohexane and ethanol (the volume ratio is preferably 1:1) and wash it multiple times. After centrifugation, disperse it in the washing solvent to obtain a dispersion of palladium-iridium-based ultrathin two-dimensional alloy nanosheets.
[0017] Preferably, in the mixed solution of step (1) above, the concentration range of the precursor salts of each metal element is as follows: palladium acetylacetonate 1.25 - 2 mg / mL, dodecacarbonyltetrairidium 1.1 - 1.2 mg / mL, hexacarbonylmolybdenum 3 - 4 mg / mL, platinum acetylacetonate 0 - 1.56 mg / mL, ruthenium acetylacetonate 0 - 2.26 mg / mL. The concentration of ammonium bromide as the inorganic salt structure inducing agent is 2 - 5 mg / mL.
[0018] In step (2) above, the heating rate is preferably < 3°C / min.
[0019] In step (3) above, when washing with cyclohexane, the centrifugation speed should not be lower than 2000 r / min, and is preferably 6000 - 8500 r / min.
[0020] The palladium-iridium-based ultrathin two-dimensional alloy nanosheets prepared by the above method have uniform size, controllable composition, and adjustable ratio of each metal element. As a hydrogen conversion electrocatalyst, it can be effectively applied to electrolytic water hydrogen evolution reaction, fuel cell hydrogen oxidation reaction, fuel cell formic acid oxidation reaction, etc.
[0021] Compared with the prior art, the present invention has the following advantages:
[0022] (1) The synthesis method is simple and easy to implement, does not rely on expensive and complex specific synthesis equipment; the synthesis time is short, the efficiency is high, the cycle is short, and it is easy to control; batch preparation can be realized, providing an important technical support for promoting the commercialization of hydrogen energy and fuel cell catalysts;
[0023] (2) The prepared palladium-iridium-based ultrathin two-dimensional alloy nanosheet hydrogen conversion electrocatalyst is in the shape of hexagonal / circular flakes, with uniform size and atomic-level thickness, breaking through the bottleneck that it is difficult to prepare sub-nanometer / atomic-level two-dimensional nanocrystals by traditional liquid-phase synthesis, and introducing an ultra-high specific surface area and an intrinsic strong strain effect;
[0024] (3) The designed material components are flexibly adjustable, the proportion of each element is controllable, the alloying of multiple elements brings a strong ligand effect and rich lattice distortion, and the multi-active sites trigger a synergistic effect, significantly improving the performance of the hydrogen evolution reaction of electrolyzed water and the hydrogen oxidation reaction of fuel cells;
[0025] (4) A five-element palladium-iridium-based ultrathin two-dimensional alloy nanosheet with a ratio of Pd:Ir:Ru:Mo:Pt = 46:18:18:14:4 can achieve ultra-high HOR catalytic performance under an ultra-low platinum loading. Brief Description of the Drawings
[0026] Figure 1 is the TEM photo of the PdIrMoPtRu (Pd:Ir:Ru:Mo:Pt = 46:18:18:14:4) five-element ultrathin two-dimensional alloy nanosheet electrocatalyst prepared in Example 3 of the present invention.
[0027] Figure 2 is the XRD pattern of the PdIrMoPtRu (Pd:Ir:Ru:Mo:Pt = 46:18:18:14:4) five-element ultrathin two-dimensional alloy nanosheet electrocatalyst prepared in Example 3 of the present invention.
[0028] Figure 3 is the alkaline hydrogen oxidation performance of the palladium-iridium-based ultrathin two-dimensional alloy nanosheet electrocatalyst prepared in Examples 1 to 3 of the present invention. Detailed Embodiments
[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, exemplary embodiments will be described in detail below, but the scope of protection required by the present invention is not limited to the following embodiments.
[0030] The preparation scheme involved in the present invention is based on the wet chemical synthesis method. By placing a mixture of specific metal precursor salts, carbonyl-based reducing agents, and inorganic salt structure inducing agents in a specific organic solvent and slowly heating to a certain temperature for reaction, a binary or even multi-element PdIr-based alloy nanosheet electrocatalyst with an ultrathin two-dimensional structure and adjustable components is obtained. This method has the advantages of high universality, short reaction time, simple operation, controllable components and morphology, etc.
[0031] Example 1
[0032] (1) Weigh 6 mg of palladium acetylacetonate, 5.5 mg of tetrairidium dodecacarbonyl, 10 mg of ammonium bromide and 15 mg of molybdenum hexacarbonyl into a 15 mL thick-walled pressure bottle, add 5 mL of oleylamine solvent, seal the bottle and place it in an oil bath, keep it warm at 50° C. for 60 minutes, so that all metal precursor salts (especially inorganic crystalline salts) are completely dissolved in the organic solvent, and a dark purple uniform precursor mixed solution is obtained;
[0033] (2) slowly heating the precursor mixed solution to 220° C. at a heating rate of less than 3° C. / min, maintaining a temperature fluctuation of no more than 3° C., and keeping the temperature for 3 h to obtain a black colloidal liquid;
[0034] (3) After the obtained colloidal liquid is naturally cooled to room temperature, 15 mL of cyclohexane solvent is added, and after sufficient ultrasonic mixing, it is centrifuged at 8500 r / min for 5 minutes, and then washed twice with 10 mL of cyclohexane in the same way, and finally dispersed in 5 mL of cyclohexane for standby use, thereby obtaining a binary PdIr (Pd:Ir=51:49) ultrathin two-dimensional alloy nanosheet dispersion.
[0035] The obtained ultra-thin two-dimensional alloy nanosheets are hexagonal sheet structures with an edge diameter range of 30-40nm. They are loaded on an XC-72 carbon carrier at a loading of 20wt.%, and blended with a mixed solution of 1:1:0.04 (volume ratio) of water, isopropanol, and 0.5wt.% Nafion solution by ultrasonication for 1 hour to prepare a 1mg / mL catalyst slurry. The alkaline hydrogen oxidation catalytic performance was tested on an electrochemical workstation using a three-electrode test system. The reference electrode used was a saturated calomel electrode, the counter electrode was a carbon rod, and the electrolyte was a 0.1mol / L KOH solution. After activation, the polarization curve was tested under H2 saturation conditions, as shown in Figure 3 As shown, it can be seen that compared with the commercial platinum-carbon catalyst, the binary PdIr nanosheet catalyst has a higher limiting diffusion current value and a more vertical mixing control zone, reflecting its excellent mass transfer performance and faster reaction kinetics.
[0036] Embodiment 2
[0037] (1) 6 mg of palladium acetylacetonate, 7.8 mg of platinum acetylacetonate, 5.5 mg of tetrairidium dodecacarbonyl, 10 mg of ammonium bromide and 15 mg of molybdenum hexacarbonyl were weighed into a 15 mL thick-walled pressure bottle, 5 mL of oleylamine solvent was added, the bottle was sealed and placed in an oil bath, and kept warm at 50° C. for 60 minutes to completely dissolve all metal precursor salts (especially inorganic crystalline salts) in the organic solvent, to obtain a dark purple uniform precursor mixed solution;
[0038] (2) slowly heating the precursor mixed solution to 220° C. at a heating rate of less than 3° C. / min, maintaining a temperature fluctuation of no more than 3° C., and keeping the temperature for 3 h to obtain a black colloidal liquid;
[0039] (3) After the obtained colloidal liquid is naturally cooled to room temperature, 15 mL of cyclohexane solvent is added. After sufficient ultrasonic mixing, it is centrifuged at 8500 r / min for 5 minutes, and then washed twice with 10 mL of cyclohexane in the same way. It is dispersed in 5 mL of cyclohexane for use, and a quaternary PdIrMoPt (Pd:Ir:Mo:Pt = 61:29:4:6) ultra-thin two-dimensional alloy nanosheet dispersion can be obtained.
[0040] The obtained ultra-thin two-dimensional alloy nanosheets are circular flake structures with a diameter range of 30 - 40 nm. They are loaded on an XC-72 type carbon support at a loading of 20 wt.%, and are ultrasonically mixed with a mixed solution of water, isopropanol, and 0.5 wt.% Nafion solution in a volume ratio of 1:1:0.04 for 1 hour to prepare a 1 mg / mL catalyst slurry. The alkaline hydrogen oxidation catalytic performance is tested on an electrochemical workstation using a three-electrode test system. The reference electrode used is a saturated calomel electrode, the counter electrode is a carbon rod, and the electrolyte is a 0.1 mol / L KOH solution. After activation, the polarization curve is tested under H2-saturated conditions, as Figure 3 shown. It can be seen that the quaternary PdIrMoPt nanosheet catalyst has a limiting diffusion current value and a mixed control region similar to those of the binary PdIr nanosheets, reflecting its excellent mass transfer performance and fast reaction kinetics.
[0041] Example 3
[0042] (1) Weigh 6 mg of palladium acetylacetonate, 7.8 mg of platinum acetylacetonate, 3.8 mg of ruthenium acetylacetonate, 5.5 mg of dodecacarbonyltetrairidium, 10 mg of ammonium bromide, and 15 mg of hexacarbonylmolybdenum into a 15 mL thick-walled pressure-resistant bottle. Add 5 mL of oleylamine solvent, seal it, and place it in an oil bath. Keep it at 50 °C for 60 minutes to completely dissolve all metal precursor salts (especially inorganic crystalline salts) in the organic solvent, obtaining a deep purple homogeneous precursor mixed solution;
[0043] (2) Slowly heat the precursor mixed solution to 220 °C at a heating rate of less than 3 °C / min, keep the temperature fluctuation within 3 °C, and hold for 3 h to obtain a black colloidal liquid;
[0044] (3) After the obtained colloidal liquid is naturally cooled to room temperature, 15 mL of cyclohexane solvent is added. After sufficient ultrasonic mixing, it is centrifuged at 8500 r / min for 5 minutes, and then washed twice with 10 mL of cyclohexane in the same way. Finally, it is dispersed in 5 mL of cyclohexane for use, and a quinary PdIrRuMoPt (Pd:Ir:Ru:Mo:Pt = 46:18:18:14:4) ultra-thin two-dimensional alloy nanosheet dispersion can be obtained.
[0045] The obtained ultrathin two-dimensional alloy nanosheets are circular flake structures with a diameter range of 30 - 40 nm. Their TEM images are as Figure 1 shown. It can be seen that the obtained materials are all ultrathin two-dimensional flake structures with uniform sizes. Their XRD patterns are as Figure 2 shown. The main characteristic peaks all show broadening characteristics, indicating that the obtained nanomaterials have low crystallinity and small grain sizes, confirming their ultrathin structures; the characteristic peaks are consistent with the fcc conventional crystal of Pd and slightly shifted to the left, proving their alloy structures. The ultrathin two-dimensional alloy nanosheets are loaded on the XC-72 type carbon carrier at a loading of 20 wt.%, and are mixed and ultrasonically treated for 1 hour with a mixed solution of water, isopropanol, and 0.5 wt.% Nafion solution at a volume ratio of 1:1:0.04 to prepare a 1 mg / mL catalyst slurry. The alkaline hydrogen oxidation catalytic performance is tested on an electrochemical workstation using a three-electrode test system. The reference electrode used is a saturated calomel electrode, the counter electrode is a carbon rod, and the electrolyte is 0.1 mol / L KOH solution. After activation, the polarization curve is tested under H2-saturated conditions. As Figure 3 shown, it can be seen that the limiting diffusion current value of the quinary PdIrRuMoPt nanosheet catalyst is higher than that of the binary PdIr nanosheet and the quaternary PdIrMoPt nanosheet, and the mixed control region is the steepest, reflecting its extremely excellent mass transfer performance and reaction kinetics. The significant improvement in its performance comes from the introduction of the Ru element.
Claims
1. A preparation method of a palladium-iridium-based ultrathin two-dimensional alloy nanosheet material, which mixes a metal precursor salt, a carbonyl-based reducing agent and an inorganic salt structure inducer in an organic solvent, and slowly heats up to 220-230 °C at a heating rate not exceeding 6 °C / min for reaction, and then washes and disperses to obtain palladium-iridium-based alloy nanosheets with an ultrathin two-dimensional structure; the component general formula of the palladium-iridium-based ultrathin two-dimensional alloy nanosheet material is Pd x Ir y M z , where M is selected from one or more of the three elements of platinum, molybdenum, and ruthenium, x + y + z = 1, 0.3 ≤ x ≤ 0.6, 0.1 ≤ y ≤ 0.5, 0 ≤ z ≤ 0.6; the ultrathin two-dimensional alloy nanosheet material is a circular or polygonal thin sheet with a size of 30-40 nm and a thickness of 0.8-1.2 nm.
2. The preparation method according to claim 1, wherein The molar percentage content of each metal element is Pd: 30% - 60%, Ir: 10% - 50%, Ru: 0 - 40%, Mo: 0 - 20%, Pt: 0 - 10%.
3. The preparation method according to claim 1, characterized in that, The material is a binary PdIr ultrathin two-dimensional alloy nanosheet, where the molar ratio of Pd:Ir = 51:49; or, the material is a quaternary PdIrMoPt ultrathin two-dimensional alloy nanosheet, where the molar ratio of Pd:Ir:Mo:Pt = 61:29:4:6; or, the material is a quinary PdIrRuMoPt ultrathin two-dimensional alloy nanosheet, where the molar ratio of Pd:Ir:Ru:Mo:Pt = 46:18:18:14:
4.
4. The preparation method according to any one of claims 1 to 3, characterized in that The metal precursor salts include palladium acetylacetonate, platinum acetylacetonate, ruthenium acetylacetonate, dodecacarbonyltetrairidium, and molybdenum hexacarbonyl; the carbonyl reducing agent is a combination of dodecacarbonyltetrairidium and molybdenum hexacarbonyl; the inorganic salt structure inducer is ammonium bromide; the organic solvent is oleylamine.
5. The preparation method according to any one of claims 1 to 3, characterized in that It includes the following steps: 1) Weigh a certain amount of the precursor salts of each metal element, the carbonyl reducing agent, and the inorganic salt structure inducer into a dry, clean, and pressure-resistant bottle, add a certain amount of organic solvent, seal it, and heat it at 50 °C - 70 °C with the rotation speed controlled at 200 - 350 rmp for 40 - 60 min. After all the raw materials are dissolved, a homogeneous precursor mixed solution is obtained; 2) Slowly heat the precursor mixed solution to 220 - 230 °C at a heating rate not exceeding 6 °C / min, adjust the rotation speed to 150 - 300 rmp, and keep it warm for 3 - 6 h to obtain a black colloidal liquid; 3) After the obtained colloidal liquid is naturally cooled to room temperature, add cyclohexane solvent or a mixed solvent of cyclohexane and ethanol for washing multiple times. After centrifugation, it is dispersed in the washing solvent to obtain a dispersion of palladium-iridium-based ultrathin two-dimensional alloy nanosheets.
6. The preparation method according to claim 5, characterized in that In step 1), palladium acetylacetonate, platinum acetylacetonate, ruthenium acetylacetonate, dodecacarbonyltetrairidium, and molybdenum hexacarbonyl are used as the precursor salts of the corresponding metal elements, and at the same time, a combination of dodecacarbonyltetrairidium and molybdenum hexacarbonyl is used as the carbonyl reducing agent; the inorganic salt structure inducer is ammonium bromide; the organic solvent is oleylamine.
7. The preparation method according to claim 6, characterized in that, In the mixed solution obtained in step 1), the concentrations of each component are: palladium acetylacetonate 1.25 - 2 mg / mL, dodecacarbonyltetrairidium 1.1 - 1.2 mg / mL, molybdenum hexacarbonyl 3 - 4 mg / mL, platinum acetylacetonate 0 - 1.56 mg / mL, ruthenium acetylacetonate 0 - 2.26 mg / mL, ammonium bromide 2 - 5 mg / mL.
8. The preparation method according to claim 6, characterized in that, The heating rate in step 2) < 3 °C / min; the centrifugation speed in step 3) is not less than 2000 r / min.
9. Application of the palladium-iridium-based ultrathin two-dimensional alloy nanosheet material obtained by the preparation method according to any one of claims 1 - 8 as a hydrogen conversion electrocatalyst.