Bent monatomic layer catalyst as well as preparation method and application thereof
By preparing a noble metal bent single-atom layer catalyst, the problem of insufficient activity and stability of fuel cell catalysts was solved, and the catalytic performance of high activity and high stability was improved, resulting in a significant improvement in fuel cell performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHONGQING UNIV
- Filing Date
- 2025-12-31
- Publication Date
- 2026-05-19
AI Technical Summary
The insufficient activity and stability of existing fuel cell catalysts limit the performance improvement of fuel cells, especially in the formic acid oxidation reaction, where traditional catalysts have poor stability under high activity and insufficient activity under high stability.
A noble metal bent monolayer catalyst was prepared by mixing a noble metal salt solution with a two-dimensional layered compound, followed by intercalation and low-temperature annealing to form nanosheets with triaxially anisotropic structures, including monolayer/few-layer nanosheets bent along the short axis. The electronic structure was optimized to enhance the catalytic performance.
The noble metal bent monolayer catalyst exhibits excellent electrocatalytic activity and stability in the formic acid oxidation reaction, with the mass activity of formic acid oxidation increased several times and the stability significantly better than that of traditional catalysts, resulting in a significant increase in fuel cell power density.
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Figure CN122068052A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalytic material preparation technology and fuel cell application technology, specifically relating to a method for preparing a noble metal bent single-atom layer catalyst and its application. Background Technology
[0002] The microstructure of nanomaterials is closely related to the spatial distribution and coordination characteristics of their active sites. Therefore, precisely designing catalytic materials at the atomic and molecular scale and developing new materials with unique structures and catalytic properties holds promise for breaking through the current limitations of electrocatalytic reaction performance. Reducing the thickness of noble metal two-dimensional nanosheets to a single atomic layer can endow them with unique catalytic properties. The literature [Science 2019,363: 870-874] reports a planar palladium nanosheet with a thickness of 3-5 single atoms. By precisely adjusting the thickness to control the internal compressive strain at 2-1%, the catalytic oxygen reduction activity is improved by more than an order of magnitude compared to traditional nanoparticles. Building on this, the thickness of ultrathin two-dimensional nanosheets is further reduced to only one atomic layer, and curvature stretching is achieved by bending the plane, further endowing the material with structural properties and thus enhancing catalytic performance.
[0003] Catalysts, as core materials for energy conversion, play a crucial role in improving conversion efficiency and selectivity. However, their low activity and poor stability are the biggest obstacles to the effective development of energy conversion technologies. Taking formic acid fuel cells as an example, Chinese invention patent CN119447342A discloses a multi-component platinum-bismuth-based intermetallic ordered nanosheet, which exhibits a mass activity of 12.4 A / mg for the catalytic oxidation of formic acid at 0.75 V. Pt The activity significantly decreased after 5000s stability testing. The literature [Adv. Mater. 2025, 37(4): 2414283] reports a novel palladium-based high-entropy amorphous alloy catalyst with a porous network, exhibiting a mass activity of 5.5 A / mg for the oxidation of formic acid at 0.3 V. Pd This is the highest value reported so far. The literature [Nat. Nanotechnol., 2020, 15(5): 390-397] reports a single-atom Rh-based FAOR catalyst whose activity decreased by 11% after 67 hours, which is the best value reported so far. Furthermore, among the FAOR catalysts developed domestically and internationally, less than 5% have been successfully applied to DFAFCs, and according to the literature [Angew. Chem. Int. Ed, 2014, 53(1): 122-126], the highest output power currently recorded is 550 mW cm⁻¹. -2 Therefore, developing a novel catalyst with high activity and high stability is of great significance for promoting the development of fuel cells. Summary of the Invention
[0004] The purpose of this invention is to provide a method for preparing a noble metal bent single-atom-layer catalyst and its application. The noble metal bent single-atom-layer material provided by this invention, when used as an electrocatalyst in fuel cells, exhibits excellent electrocatalytic activity, stability, and power output.
[0005] To achieve the above objectives, the present invention provides the following technical solution:
[0006] The present invention provides a noble metal bent single-atom layer catalyst, comprising a noble metal single-atom layer having a micro-geometry with different dimensions in three dimensions, and a single / few-layer nanosheet morphology bent along the short axis.
[0007] Optionally, the noble metal in the noble metal-based monolayer includes one or more of the elements ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, and gold.
[0008] Optionally, the length of the noble metal-based monolayer is 10~1000 nm, the width is less than 500 nm, and the thickness is less than 1 nm.
[0009] This invention provides a method for preparing the noble metal bent monolayer catalyst described above, comprising the following steps:
[0010] Step 1: The noble metal salt solution and the two-dimensional layered compound are thoroughly mixed under ultrasound to obtain a suspension;
[0011] Step 2: The obtained suspension is subjected to intercalation treatment to allow metal cations to enter the two-dimensional layered compound space;
[0012] Step 3: Heat in a water bath to 50-80°C and keep warm for 5-8 hours to remove the solvent and obtain a solid precursor;
[0013] Step 4: The solid precursor is annealed at low temperature in a reducing atmosphere and then naturally cooled to room temperature to obtain the reduced product;
[0014] Step 5: Remove the two-dimensional layered compound from the reduction product, then wash and dry it to obtain a curved monolayer catalyst.
[0015] Optionally, the precious metal salt mentioned in step 1 includes, but is not limited to, chloride salts, nitrate salts, sulfate salts, acetylacetone salts, or acetate salts; the concentration of the precious metal salt in the precious metal salt solution is 0.05-0.15 mol / L.
[0016] Optionally, the two-dimensional layered compounds described in step 1 include, but are not limited to, layered bimetallic hydroxides, metal cation-modified montmorillonite, layered silicates RUB-15 and RUB-18, and transition metal dichalcogenides such as molybdenum disulfide and tungsten disulfide.
[0017] Optionally, the mass of the noble metal salt solution added in step 1 is 20% of the mass of the two-dimensional layered compound.
[0018] Optionally, the intercalation process described in step 2 includes, but is not limited to, vacuum forced intercalation, mixed free intercalation, or organic material expansion intercalation.
[0019] Optionally, the reducing atmosphere described in step 4 is a mixture of hydrogen and an inert gas.
[0020] Optionally, the low-temperature annealing treatment in step 4 is performed at a temperature of 50-200℃ and a holding time of 1-6 h.
[0021] Optionally, the etching agent in step 5 includes, but is not limited to, hydrofluoric acid, ammonium fluoride, potassium hydroxide, or sodium hydroxide.
[0022] Preferably, the drying conditions in step 5 are a vacuum of 50-70°C.
[0023] This invention provides the application of the noble metal bent monolayer material described in the above technical solutions or the noble metal bent monolayer prepared by the above technical solutions as a catalyst in fuel cells.
[0024] This invention provides a noble metal bent monolayer material with varying dimensions in three directions (major axis X, minor axis Y, and thickness Z), a thickness of only 1-3 atoms, and a nanosheet structure bent along the minor axis. The noble metal bent monolayer provided by this invention not only possesses the structural characteristics of a large number of active sites in monolayer / few-layer nanosheets, but the bending of the monolayer induces tensile strain along the minor axis and compressive strain along the major axis, inducing orbital hybridization and constructing three different bonding modes: free orbitals (thickness) along the Z direction, compressive bonding along the X direction (major axis), and stretched bonding along the Y direction (minor axis). This unique triple-split novel electronic structure allows for simultaneous optimization of electrons. Compression in the X direction lowers the bonding orbitals, resulting in stronger bonds and easier electron accommodation. Stretching in the Y direction allows electrons to occupy higher bonding orbitals, while the Z direction remains unbonded, thus enhancing electron contribution. This optimizes the adsorption and desorption capabilities of the reactants, enabling the catalyst to exhibit excellent electrocatalytic performance. Attached Figure Description
[0025] Figure 1 This is a transmission electron microscope image of the noble metal curved single-atom layer prepared in Example 1;
[0026] Figure 2 This is a transmission electron microscope image of the noble metal curved single-atom layer prepared in Example 2;
[0027] Figure 3 This is a transmission electron microscope image of the noble metal curved single-atom layer prepared in Example 3;
[0028] Figure 4 This is a transmission electron microscope image of the noble metal curved single-atom layer prepared in Example 4;
[0029] Figure 5 This is a transmission electron microscope image of the noble metal curved single-atom layer prepared in Example 5;
[0030] Figure 6 This is a transmission electron microscope (TEM) image of the noble metal bent single-atom layer prepared in Example 6;
[0031] Figure 7 This is a transmission electron microscope image of the noble metal curved single-atom layer prepared in Example 7;
[0032] Figure 8 This is a transmission electron microscope image of the noble metal curved single-atom layer prepared in Example 8;
[0033] Figure 9 This is a comparison of the mass activity and stability of the palladium bent monolayer catalyst prepared in Example 1 and the palladium-carbon catalyst prepared in Comparative Example 1 under acidic conditions for formic acid oxidation.
[0034] Figure 10 The graph shows a comparison of the polarization and power curves of formic acid fuel cells using the palladium bent monolayer catalyst prepared in Example 1 and the palladium carbon catalyst prepared in Comparative Example 1 as anode catalysts. Detailed Implementation
[0035] To further illustrate the present invention, the preparation method and application of the noble metal curved single-atom layer material provided by the present invention are described in detail below with reference to examples, but these should not be construed as limiting the scope of protection of the present invention.
[0036] Example 1
[0037] 0.25 g of sodium montmorillonite was ultrasonically dispersed in 9.40 mL of 0.05 mol / L palladium chloride solution to obtain a homogeneous suspension, which was then transferred to a rotary evaporator flask; vacuum (pressure 10) was applied. -4Under certain conditions (Pa), palladium ions were intercalated into the montmorillonite interlayer, and the solid powder was obtained by evaporation at 60°C for 5 h. The obtained solid was then annealed under a reducing atmosphere consisting of a mixture of nitrogen at a flow rate of 90 mL / min and hydrogen at a flow rate of 10 mL / min, with a programmed heating rate of 5°C / min. The mixture was held at 50°C for 2 h and then allowed to cool naturally to obtain a bent palladium monolayer precursor. The montmorillonite in the precursor was etched away using a 40% HF solution, followed by alternating washing with ethanol and ultrapure water 10 times, and then vacuum drying and grinding at 60°C to obtain a bent palladium monolayer catalyst.
[0038] The palladium-bent monolayer catalyst obtained in this example is as follows: Figure 1 The aberration-corrected electron microscopy (TEM) image of the single-atom-layer material shows that the palladium nanosheets in the image reach approximately 140 nm along the long axis and only about 20 nm along the short axis, indicating a significant difference in size between the length and width directions in the plane. The area circled by the red dashed line is located at the edge of the sheet or at a slightly upturned point, showing that its "thickness" direction has deviated from the typical planar projection, thus demonstrating its difference in thickness, length, and width directions, i.e., "three-dimensional anisotropy". Furthermore, this edge region is extremely thin in the TEM image and no obvious multilayer stacking striations are observed, indicating that the nanosheet is most likely a few-layer or even single-layer state. The yellow model in the image visually shows its geometry, and the location indicated by the red circle is the key part when the view changes from a planar perspective to an inclined state. Through this point, both the characteristics of "three-dimensional anisotropy" and "single / few-layer nanosheets" can be verified.
[0039] As can be seen, this example demonstrates the achievement of low-temperature precision atomic weaving with controllable major axis X and minor axis Y dimensions through vacuum-confined flow synthesis technology. This method utilizes the following two points: i) vacuum-enhanced capillary action (10 -4 The Pascal method induces the infiltration of noble metal ion precursors into the 0.3–0.5 nm interlayer space of montmorillonite, where the interaction between capillary forces and interatomic cohesion determines the extension of the long axis and the formation of the short axis. Constrained atomic reduction at 50–200°C inhibits the diffusion of noble metal atoms while simultaneously reducing metal ions, thus maintaining an anisotropic morphology along the flow direction. This dual control mechanism produces strip-shaped single / few-atom layer structures with defined dimensions (length 10–1000 nm, width less than 500 nm, thickness less than 1 nm). When montmorillonite is etched, spontaneous bending occurs to balance the high surface energy, resulting in curvature suitable for atomic-scale strain engineering.
[0040] It is worth noting that the two-dimensional layered compounds used for obtaining single-atom layers include, but are not limited to, layered bimetallic hydroxides, metal cation-modified montmorillonite, layered silicates RUB-15 and RUB-18, and transition metal dichalcogenides such as molybdenum disulfide and tungsten disulfide. Intercalation methods include, but are not limited to, vacuum forced intercalation, mixed free intercalation, or organic layer expansion followed by intercalation. Etching agents used include, but are not limited to, hydrofluoric acid, ammonium fluoride, potassium hydroxide, or sodium hydroxide.
[0041] Example 2
[0042] 0.25 g of sodium montmorillonite was ultrasonically dispersed in 3.30 mL of 0.15 mol / L ruthenium trichloride solution to obtain a homogeneous suspension, which was then transferred to a rotary evaporator flask; vacuum (pressure 10) was applied. -4 Under certain conditions (Pa), ruthenium ions were intercalated into the montmorillonite interlayer, and the solid powder was obtained by evaporation at 50°C for 5 h. The obtained solid was then annealed under a reducing atmosphere consisting of a mixture of nitrogen at a flow rate of 80 mL / min and hydrogen at a flow rate of 20 mL / min, with a programmed heating rate of 5°C / min. The mixture was held at 100°C for 2 h and then allowed to cool naturally to obtain a bent ruthenium monolayer precursor. The montmorillonite in the precursor was etched away using a 40% HF solution, followed by alternating washing with ethanol and ultrapure water 10 times, and then vacuum drying and grinding at 60°C to obtain a bent ruthenium monolayer catalyst.
[0043] The ruthenium-bent monolayer catalyst obtained in this example is basically as follows: Figure 2 As shown, the ruthenium nanosheet has a major axis of approximately 90 nm and a minor axis of approximately 20 nm, indicating a significant difference in size between the two dimensions within the plane. The blue schematic diagram in the figure represents a three-dimensional projection of the nanosheet, used to visually demonstrate its geometric morphology. Combined with the size difference, it can be inferred that the nanosheet also differs from its length and width in the thickness direction, exhibiting a three-dimensionally different structure, and its relatively small thickness suggests it may be a single-layer or few-layer thin-sheet structure.
[0044] Example 3
[0045] 0.25 g of layered double hydroxide was ultrasonically dispersed in 9.70 mL of 0.05 mol / L rhodium trichloride solution to obtain a homogeneous suspension, which was then transferred to a rotary evaporation flask; vacuum (pressure 10) was applied. -4Under certain conditions (Pa), rhodium ions were intercalated into layered double hydroxides, and the mixture was evaporated at 60°C for 5 h to obtain a solid powder. The obtained solid was then annealed under a reducing atmosphere consisting of a mixture of nitrogen at a flow rate of 90 mL / min and hydrogen at a flow rate of 10 mL / min. The temperature was programmed to rise at 5°C / min and held at 50°C for 2 h. After natural cooling, a bent rhodium monolayer precursor was obtained. The layered double hydroxides in the precursor were etched away using a 3 mol / L NaOH solution. The precursor was then washed 10 times alternately with ethanol and ultrapure water, and finally vacuum dried and ground at 60°C to obtain a rhodium bent monolayer catalyst.
[0046] The rhodium-bent monolayer catalyst obtained in this example is basically as follows: Figure 3 As shown, the major axis of the rhodium nanosheet is approximately 80 nm, and the minor axis is approximately 20 nm, indicating a significant difference in size between the two dimensions within the plane, reflecting obvious anisotropy in its geometry. The blue schematic diagram on the left serves as an auxiliary structure, possibly representing the cross-section and three-dimensional projection of the nanosheet, visually demonstrating its sheet morphology and spatial positioning. Combining the projected morphology and the absence of obvious layered striations in the TEM image, it can be preliminarily inferred that the nanosheet is a single-layer or few-layer structure.
[0047] Example 4
[0048] 0.25 g of layered silicate RUB-15 was ultrasonically dispersed in 3.10 mL of 0.15 mol / L silver nitrate solution to obtain a homogeneous suspension, which was then transferred to a rotary evaporation flask; vacuum (pressure 10) was applied. -4 Under certain conditions (Pa), silver ions were intercalated into the interlayer of RUB-15 and evaporated at 50°C for 5 h to obtain a solid powder. The obtained solid was then annealed under a reducing atmosphere consisting of a mixture of nitrogen at a flow rate of 90 mL / min and hydrogen at a flow rate of 10 mL / min, with a programmed heating rate of 5°C / min. The mixture was held at 50°C for 2 h and then allowed to cool naturally to obtain a bent silver monolayer precursor. The silicates in the precursor were etched away using a 3 mol / L KOH solution, followed by alternating washing with ethanol and ultrapure water 10 times. The precursor was then vacuum dried and ground at 60°C to obtain a bent silver monolayer catalyst.
[0049] The silver-bent monolayer catalyst obtained in this example is basically as follows: Figure 4 As shown, the silver nanosheet has a major axis of approximately 75 nm and a minor axis of approximately 15 nm, exhibiting a significant difference in size between the two dimensions within the plane, thus indicating significant geometric anisotropy. The blue auxiliary structure depicted in the figure can be seen as a visual illustration of the nanosheet's geometry, aiding in understanding its three-dimensional morphology and structural features from different perspectives. No obvious layered striations were observed in the TEM image, suggesting a preliminary assessment that it is a single-layer or few-layer structure.
[0050] Example 5
[0051] 0.25 g of sodium montmorillonite was ultrasonically dispersed in 5.30 mL of 0.05 mol / L osmium trichloride solution to obtain a homogeneous suspension, which was then transferred to a rotary evaporator flask; a vacuum (pressure 10) was applied. -4 Under certain conditions (Pa), osmium ions were intercalated into the montmorillonite interlayer, and the solid powder was obtained by evaporation at 60°C for 5 h. The obtained solid was then annealed under a reducing atmosphere consisting of a mixture of nitrogen at a flow rate of 90 mL / min and hydrogen at a flow rate of 10 mL / min, with a programmed heating rate of 5°C / min. The mixture was held at 80°C for 2 h and then allowed to cool naturally to obtain a bent osmium monolayer precursor. The montmorillonite in the precursor was etched away using a 40% HF solution, followed by alternating washing with ethanol and ultrapure water 10 times, and then vacuum drying and grinding at 60°C to obtain the bent osmium monolayer catalyst.
[0052] The osmium-bent monolayer catalyst obtained in this example is basically as follows: Figure 5 As shown, the osmium nanosheet has a major axis of approximately 50 nm and a minor axis of approximately 10 nm, indicating a significant difference in size between the two dimensions within the plane. The blue schematic diagram in the figure represents a three-dimensional projection of the nanosheet, used to visually demonstrate its geometric morphology. Combined with the size difference, it can be inferred that the nanosheet also differs from its length and width in the thickness direction, exhibiting a three-dimensionally different structure, and its relatively small thickness suggests it may be a single-layer or few-layer thin-sheet structure.
[0053] Example 6
[0054] 0.25 g of layered double hydroxide was ultrasonically dispersed in 5.20 mL of 0.05 mol / L chloroiridium acid solution to obtain a homogeneous suspension, which was then transferred to a rotary evaporator flask; vacuum (pressure 10) was applied. -4 Under certain conditions (Pa), iridium ions were intercalated into the interlayer of layered double hydroxides, and the solid powder was obtained by evaporation at 60°C for 5 h. The obtained solid was then annealed under a reducing atmosphere consisting of a mixture of nitrogen at a flow rate of 80 mL / min and hydrogen at a flow rate of 20 mL / min, with a programmed heating rate of 5°C / min, and held at 100°C for 2 h. After natural cooling, a bent iridium monolayer precursor was obtained. The layered double hydroxides in the precursor were etched away using a 3 mol / L NaOH solution, followed by alternating washing with ethanol and ultrapure water 10 times, and vacuum drying and grinding at 60°C to obtain the bent iridium monolayer catalyst.
[0055] The iridium-bent monolayer catalyst obtained in this example is basically as follows: Figure 6As shown, the nanosheet has a major axis of approximately 80 nm and a minor axis of approximately 15 nm, indicating a significant difference in size between the two dimensions within the plane, demonstrating anisotropy in planar geometry. The blue auxiliary structure in the upper right corner of the image is used to visually illustrate the geometry and projection of the nanosheet. Combining the aforementioned dimensions with the absence of obvious layered striations in the TEM image, it can be inferred that the nanosheet is extremely thin, consistent with a single-layer or few-layer structure. In summary, this sheet exhibits anisotropic characteristics in three directions: the major axis, the minor axis, and the thickness.
[0056] Example 7
[0057] 0.25 g of layered silicate RUB-15 was ultrasonically dispersed in 2.50 mL of 0.10 mol / L chloroplatinic acid solution to obtain a homogeneous suspension, which was then transferred to a rotary evaporation flask; vacuum (pressure 10) was applied. -4 Under certain conditions (Pa), platinum ions were intercalated into the interlayer of RUB-15, and the solid powder was obtained by evaporation at 50°C for 5 h. The obtained solid was then annealed under a reducing atmosphere consisting of a mixture of nitrogen at a flow rate of 90 mL / min and hydrogen at a flow rate of 10 mL / min, with a programmed heating rate of 5°C / min. The mixture was held at 50°C for 2 h and then allowed to cool naturally to obtain a bent platinum monolayer precursor. The silicates in the precursor were etched away using a 3 mol / L KOH solution, followed by alternating washing with ethanol and ultrapure water 10 times, and vacuum drying and grinding at 60°C to obtain a platinum bent monolayer catalyst.
[0058] The platinum-bent monolayer catalyst obtained in this example is basically as follows: Figure 7 As shown, the nanosheet has a major axis of approximately 90 nm and a minor axis of approximately 33 nm, indicating a significant difference in size between the two dimensions within the plane, reflecting a marked anisotropy in its geometry. The blue auxiliary structure in the upper right corner of the figure is used to visually demonstrate its geometry and projection. Since no overlapping stripes are observed in the figure, it can be preliminarily determined to be a single-layer or few-layer structure.
[0059] Example 8
[0060] 0.25 g of layered double hydroxide was ultrasonically dispersed in 5.10 mL of 0.05 mol / L chloroauric acid solution to obtain a homogeneous suspension, which was then transferred to a rotary evaporation flask; vacuum (pressure 10) was applied. -4Under certain conditions (Pa), gold ions were intercalated into the interlayer of layered double hydroxides, and the solid powder was obtained by evaporation at 60°C for 5 h. The obtained solid was then annealed under a reducing atmosphere consisting of a mixture of nitrogen at a flow rate of 90 mL / min and hydrogen at a flow rate of 10 mL / min, with a programmed heating rate of 5°C / min. The mixture was held at 50°C for 2 h and then allowed to cool naturally to obtain a bent gold monolayer precursor. The layered double hydroxides in the precursor were etched away using a 3 mol / L NaOH solution, followed by alternating washing with ethanol and ultrapure water 10 times, and vacuum drying and grinding at 60°C to obtain a bent gold monolayer catalyst.
[0061] The gold-bent monolayer catalyst obtained in this example is basically as follows: Figure 8 As shown, the nanosheet has a major axis of approximately 80 nm and a minor axis of approximately 25 nm, indicating a significant difference in size between the two dimensions within the plane, reflecting a marked anisotropy in its geometry. The blue auxiliary structure in the upper right corner of the image illustrates its geometry and three-dimensional structure. No obvious layered striations are observed in the TEM image, suggesting that it is a single-layer or few-layer structure.
[0062] Comparative Example 1
[0063] 0.08 g of carbon powder was ultrasonically dispersed in 1.88 mL of 0.1 mol / L palladium chloride solution and stirred vigorously for 24 h. Then, 8 mL of aqueous solution containing 60 mg of sodium citrate was added, and the pH was adjusted to 9 using 1 mol / L sodium carbonate in ethylene glycol solution. 10 mL of aqueous solution containing 1 g of sodium borohydride was added dropwise under vigorous stirring in an ice bath, and the reaction was stirred for 12 h. Finally, the palladium-on-carbon catalyst was obtained after filtration, washing, drying, and grinding.
[0064] The electrocatalytic performance of the palladium bent monolayer catalyst prepared in Example 1 for formic acid oxidation was tested. The test methods and conditions were as follows: all electrochemical test data were collected by a Princeton VersaSTAT 3F electrochemical workstation under 30°C water bath conditions. A three-electrode system was used for the electrochemical formic acid oxidation performance test. The working electrode was a glassy carbon electrode, the reference electrode was a silver / silver chloride electrode, and the counter electrode was a carbon rod. The formic acid oxidation electrolyte was a nitrogen-saturated 0.1 mol / L perchloric acid solution containing 0.5 mol / L formic acid. The formic acid oxidation potential window was 0.1–1.2 V (vs. RHE), and the scan rate was 50 mV / s. The stability test was performed using accelerated aging cycles. Cyclic voltammetry scans were performed in a nitrogen-saturated 0.1 mol / L perchloric acid solution containing 0.5 mol / L formic acid. The scan range was 0–0.8 V (vs. RHE), and the scan rate was 200 mV / s. After each 10,000 cycles, a new electrolyte was used to test the formic acid oxidation activity. The above steps were repeated to compare the changes in activity before and after aging. Comparative Example 1, palladium catalyst on carbon, was used as a control.
[0065] Figure 9 (A) is a comparison graph of the mass activity of the palladium bent monolayer catalyst prepared in Example 1 and the palladium-carbon catalyst prepared in Comparative Example 1 under acidic conditions for formic acid oxidation, where the vertical axis represents the mass activity (A / mg). Pd ).from Figure 9 As shown in (A), the palladium bent monolayer catalyst exhibits superior formic acid oxidation performance, with the reaction following a dehydrogenation pathway. At 0.3 V, its formic acid oxidation mass activity is 12.3 A / mg. Pd It is 49.2 times that of the palladium on carbon catalyst in Comparative Example 1 under the same conditions. Figure 9 (B) is a comparison of the stability of the palladium bent monolayer catalyst prepared in Example 1 and the palladium-carbon catalyst prepared in Comparative Example 1 under acidic conditions. Figure 9 As shown in (B), comparing the longitudinal mass activity after different number of cycles, its activity only decreased by 10.6% after 200 k cycles, and its stability was significantly better than that of the palladium on carbon catalyst in Comparative Example 1.
[0066] The palladium-bent monolayer catalyst prepared in Example 1 was used to test the performance of a formic acid fuel cell. The test method and conditions were as follows: the test data of the formic acid fuel cell were recorded using a Scribner 850e fuel cell test workstation. The noble metal loading of the palladium-bent monolayer catalyst at the anode was 0.127 mg / cm³. Pd 2 The noble metal loading of the commercial platinum-carbon cathode catalyst is 0.4 mg / cm³. Pt 2The ionomer was a 5 wt.% Nafion solution, and its mass was 25% of the catalyst mass. The catalyst and ionomer were ultrasonically dispersed in isopropanol. The thoroughly mixed catalyst slurry was sprayed onto the gas diffusion layer using a spray gun. The cathode gas diffusion layer was HCP-120 carbon paper, and the anode liquid diffusion layer was Toray carbon paper. The membrane electrode assembly was prepared by hot pressing according to the anode-proton exchange membrane-cathode sequence at a pressure of 5 MPa, a temperature of 135°C, and a time of 150 s. Power performance testing used a Nafion 212 membrane (DuPont). The effective geometric area was 1 cm². 2 The anode fuel was a 3 mol / L formic acid solution supplied by a flow pump at a flow rate of 30 mL / min, and the cathode fuel was oxygen at a flow rate of 1000 mL / min. The single-cell test temperature was 80°C, and a small pressure of 5 kPa was applied to the cathode during the test.
[0067] Figure 10 This is a comparison of the polarization and power curves of formic acid fuel cells using the palladium bent single-atom-layer catalyst prepared in Example 1 and the palladium-carbon catalyst prepared in Comparative Example 1 as anode catalysts. Figure 10 It can be seen that the power density of the palladium bent monolayer catalyst reaches 618 mW / cm². 2 This is significantly higher than the 133 mW cm⁻¹ achieved by traditional palladium-on-carbon catalysts. -2 .
[0068] In summary, compared to palladium-on-carbon catalysts, palladium-curved monolayer catalysts significantly enhance both the activity and stability of formic acid oxidation, stemming from their unique curved nanosheet structure and the resulting triple-split electronic structure modulation advantages. Specifically, compression along the X-axis (long axis) elevates antibonding orbitals and lowers bonding orbitals, making it easier to accommodate electrons and thus enhancing reaction stability. Stretching along the Y-axis (short axis) lowers antibonding orbitals and elevates bonding orbitals, placing the molecule in a high-energy state. Furthermore, the Z-axis consists of unbonded free orbitals with more free electrons, which is beneficial for enhancing reaction activity.
[0069] It is worth noting that noble metal elements (ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, and gold) all have unfilled d-electron orbitals, suitable d-band centers, and high Fermi levels, making them widely used in the field of catalysis. Therefore, other noble metal element monolayer catalysts prepared in the aforementioned examples can achieve the same or similar performance when used in fuel cells.
Claims
1. A noble metal bent monolayer catalyst, characterized in that, This includes noble metal monolayers with micro-geometry that varies in three dimensions, and mono / few-layer nanosheet morphologies that bend along the short axis.
2. The noble metal bent monolayer catalyst according to claim 1, characterized in that, The noble metal in the noble metal-based monolayer includes one or more of the following elements: ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, and gold.
3. The noble metal bent monolayer catalyst according to claim 1, characterized in that, The length of the noble metal-based monolayer is 10~1000 nm, the width is less than 500 nm, and the thickness is less than 1 nm.
4. The method for preparing the noble metal bent monolayer catalyst according to any one of claims 1-3, characterized in that, This includes confining noble metal precursors in a two-dimensional space for in-situ reduction or transformation, allowing the noble metal to grow in the form of a single atomic layer or few atomic layers, and spontaneously forming a curved structure after releasing the spatial constraints, thereby obtaining a curved single atomic layer catalyst with anisotropic strain distribution.
5. The method according to claim 4, characterized in that, in, In-situ low-temperature reduction treatment is used to suppress long-range diffusion of noble metal atoms and maintain the anisotropic morphology of nanosheets, wherein the low temperature refers to less than 200°C.
6. The method according to claim 4, characterized in that, The anisotropic strain distribution enables different regions on the surface of the nanosheets to have differentiated adsorption and desorption capabilities for reaction intermediates.
7. The method for preparing the noble metal bent monolayer catalyst according to any one of claims 1-3, characterized in that, Includes the following steps: Step 1: The noble metal salt solution and the two-dimensional layered compound are thoroughly mixed under ultrasound to obtain a suspension; Step 2: The obtained suspension is subjected to intercalation treatment to allow metal cations to enter the two-dimensional layered compound space; Step 3: Heat in a water bath to 50-80°C and keep warm for 5-8 hours to remove the solvent and obtain a solid precursor; Step 4: The solid precursor is annealed at low temperature in a reducing atmosphere and then naturally cooled to room temperature to obtain the reduced product; Step 5: Remove the two-dimensional layered compound from the reduction product, then wash and dry it to obtain a curved monolayer catalyst.
8. The method according to claim 7, characterized in that, The two-dimensional layered compounds mentioned in step 1 include, but are not limited to, layered bimetallic hydroxides, metal cation-modified montmorillonite, layered silicates RUB-15 and RUB-18, and transition metal dichalcogenides such as molybdenum disulfide and tungsten disulfide.
9. A fuel cell, characterized in that, This includes the noble metal bent monolayer catalyst as described in any one of claims 1-3.
10. The application of the noble metal bent monolayer catalyst as described in any one of claims 1-3 in fuel cells.