Three-dimensional carrier supported palladium-gold nanocatalyst and preparation method thereof

Abstract

The application discloses a three-dimensional carrier loaded palladium-gold nano catalyst and a preparation method thereof, and belongs to the technical field of hydrogen energy storage battery catalysts. The three-dimensional layered nitrogen-doped carbon black / nitrogen-doped graphene is used as a composite carrier, and after being modified by an amino group, a wet chemical reduction method is used to load palladium-gold bimetallic nanoparticles, so that a catalyst capable of efficiently catalyzing the dehydrogenation of formic acid at room temperature without adding an additive is obtained. The nitrogen-doped carbon black spacing prevents the stacking of graphene sheets, the nitrogen-doping and amino modification strengthen the metal anchoring capacity, the PdAu nanoparticles are uniformly and stably loaded, and the catalytic activity and the cycle stability are significantly improved. The obtained PdAu / NH2-NCB H @NGS has an initial conversion frequency of 5819 h ‑1 at 30 DEG C, the formic acid conversion rate and the hydrogen selectivity are both 100%, no additional additive is needed, and the technical problems of low activity, easy agglomeration and deactivation and poor stability of traditional palladium-based catalysts are effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology for hydrogen energy storage batteries, specifically a three-dimensional supported palladium nanocatalyst and its preparation method. Background Technology

[0002] The excessive use of fossil fuels has led to massive greenhouse gas emissions, causing global warming and driving the rapid development of zero-carbon clean energy technologies. Hydrogen, with its high energy density and clean, pollution-free nature, is an ideal green energy source, but its low storage density and poor storage and transportation safety limit its commercial application. Liquid organic hydrogen storage materials, such as formic acid and methanol, can reversibly store and release hydrogen under mild conditions, offering advantages such as low cost and compatibility with existing storage and transportation facilities. Among these, formic acid has the highest hydrogen storage capacity and best safety, making it the most promising candidate for application.

[0003] Formic acid dehydrogenation catalysts are mainly divided into homogeneous catalysts and heterogeneous catalysts. Homogeneous catalysts have high activity but are costly, difficult to recover, and have poor stability, making them difficult to industrialize. Supported heterogeneous catalysts are easy to separate and recycle, making them more suitable for industrial applications. Among heterogeneous catalysts, palladium-based bimetallic alloys (PdM) exhibit excellent catalytic performance, especially palladium-gold (PdAu) alloys, which can modulate the electronic structure of Pd, significantly improving dehydrogenation activity and resistance to poisoning. However, metal nanoparticles have high surface energy, making them prone to aggregation, sintering, and deactivation, requiring high-performance supports for stable anchoring and dispersion. Existing graphene supports are prone to layer stacking, leading to a decrease in specific surface area and insufficient exposure of active sites; conventional supports have weak interactions with metals, making metal particles prone to detachment and aggregation, ultimately resulting in low formic acid dehydrogenation activity, poor stability, and the need for external additives.

[0004] Therefore, developing palladium bimetallic catalysts that combine high activity and high stability with room temperature operation without additives is a key technological requirement in the field of hydrogen energy storage. Summary of the Invention

[0005] This invention addresses the problems of low activity, poor stability, and easy agglomeration and deactivation of traditional Pd-based catalysts in formic acid dehydrogenation. It provides a three-dimensional supported palladium nanocatalyst and its preparation method, wherein PdAu nanoparticles are supported on an amino-NH2 modification and used as a room-temperature, additive-free formic acid dehydrogenation catalyst. The specific technical solution is as follows: The core technical solution adopted in this invention is: using three-dimensional layered nitrogen-doped carbon black / nitrogen-doped graphene (NCB). H @NGS was used as a composite support, and PdAu nanoparticles were loaded onto it after amino-NH2 modification. This catalyst was used as a room-temperature, additive-free formic acid dehydrogenation catalyst. Graphene oxide (GO) and acid-etched carbon black (CB) were employed. H A porous network structure was fabricated by self-assembly combined with urea hydrothermal reduction doping; then, uniform PdAu loading was achieved through wet chemical reduction. The optimized Pd... 0.6 Au 0.3 / NH2-2NCB H @NGS exhibits excellent catalytic performance, achieving an initial TOF of 5819 h at 303 K. -1 The formic acid conversion rate and hydrogen selectivity were both 100%, and the reaction required no additives. As an innovation, this study innovatively constructed a nitrogen-doped carbon black-interspersed, anti-stacking three-dimensional porous graphene composite support. Through nitrogen doping and synergistic modification with amino groups to enhance metal anchoring, uniform and stable PdAu loading was achieved, successfully overcoming the limitations of low activity and low stability of existing palladium-based catalysts.

[0006] A method for preparing palladium nanocatalyst supported on a three-dimensional support, comprising the following steps: -NH2-modified Pd-based alloy nanoparticles grown on a three-dimensional support are prepared by wet chemical reduction and used as a formic acid dehydrogenation catalyst at room temperature without additives. Step 1: Preparation of graphene oxide (GO); Using a modified Hummers method, graphite sheets were partially oxidized with potassium permanganate in an ice-water bath in a concentrated sulfuric acid-phosphoric acid mixture. The oxidation was carried out at 50°C for 24 h, followed by ice-water quenching, hydrogen peroxide oxidation, and repeated acid washing, water washing, and centrifugation to obtain a 10 mg / mL graphene oxide (GO) solution. -1 GO aqueous dispersion; Step 2: NCB H Preparation of @NGS: First, carbon powder was etched with 6.0 M nitric acid at 90 °C for 3 h and then washed with water until neutral to obtain functionalized carbon material CB. H Then CB H NCB was prepared by ultrasonic dispersion of GO aqueous dispersion, hydrothermal treatment with urea at 160 °C for 4 h, filtration, washing with water, and freeze-drying. H @NGS composite carrier; Step 3: PdAu / NH2-NCB H Preparation of @NGS catalyst; NCB H The NGS composite carrier was dispersed in water and stirred thoroughly for 1 h. 3-Aminopropyltriethoxysilane was added and stirred for 1 h. K₂PdCl₄ and HAuCl₄ in a molar ratio of 3:2 were then added and stirred for 1 h. Under vigorous stirring in an ice bath, freshly prepared NaBH₄-containing aqueous solution was added dropwise to the mixture and stirred for 1 h. Finally, the product was filtered with deionized water and freeze-dried overnight to prepare PdAu / NH₂-NCB. H @NGS.

[0007] Preferably, in step 1, potassium permanganate is added in batches in an ice-water bath at a temperature of <5°C, in batches of 0.1g each time, for a total of 18g of potassium permanganate.

[0008] Preferably, in step 1, the graphite sheets are added to potassium permanganate in batches in an ice-water bath in a concentrated sulfuric acid-phosphoric acid mixture, with the mass ratio of graphite sheets to potassium permanganate being 1:6, and the mass ratio of concentrated sulfuric acid to phosphoric acid in the concentrated sulfuric acid-phosphoric acid mixture being 3:1.

[0009] Preferably, the functionalized carbon material CB obtained in step 2 H The mass is 0.5g; CB H The mass ratio of GO aqueous dispersion and urea is 2:1:30.

[0010] Preferably, in step 3, NCB H The mass ratio of @NGS composite carrier to water is 1:1; 0.2 mL of 3-aminopropyltriethoxysilane is added.

[0011] Preferably, the mass ratio of NaBH4 to aqueous solution in step 3 is 1:125.

[0012] A three-dimensional support for palladium nanocatalyst, wherein the catalyst support is an amino-modified nitrogen-doped carbon black / nitrogen-doped graphene three-dimensional porous composite material, and the active component is palladium bimetallic nanoparticles.

[0013] Preferably, the catalyst, under additive-free conditions at 30°C, has a TOF... initial 5819h -1 The formic acid conversion rate and H2 selectivity both reached 100%.

[0014] Compared with the closest existing technology, the technical solution provided by the present invention has the following beneficial effects: 1. The unique three-dimensional layered composite structure of this invention is conducive to exposing more Pd active sites; -NH2, as a Lewis basic site, can provide electrons to PdA nanoparticles, promote the dissociation and adsorption of formic acid, and reduce the CH bond breaking energy barrier by stabilizing the transition state, thus accelerating the dehydrogenation step; the second metal element Au optimizes the d-band center of Pd through strong electronic effects, inhibits the excessive adsorption of CO, promotes the rapid desorption or oxidation of CO to CO2, and induces Pd to be highly dispersed, forming highly active sites.

[0015] 2. This invention provides PdAu / NH2-NCB without additives. H @NGS can catalyze the complete hydrogen production from formic acid within 2.6 min, and TOF at 30 °C initial 5819 h -1 With an apparent activation energy of only 29.9 kJ / mol, it maintains 100% formic acid conversion and H2 selectivity. After five cycles of reaction, the catalyst still maintains good structural stability and catalytic activity, demonstrating excellent overall performance and solving the problem of easy agglomeration and deactivation of traditional palladium-based catalysts.

[0016] 3. The preparation process of this invention is simple and the conditions are mild, making it suitable for industrial production. Attached Figure Description

[0017] Figure 1 For the present invention GO, NCB H @NGS and PdAu / NH2-NCB H XRD patterns of @NGS; Figure 2 The present invention is PdAu / NH2-NCB H @NGS HRTEM characterization test plot; where: (a) and (b) are TEM images; (c) is the HR-TEM image; (d) is the corresponding particle size distribution diagram; Figure 3 This invention utilizes NH2-NCB under additive-free conditions at 303 K. H Volumetric images of a series of PdM-catalyzed formic acid gas production prepared using @NGS as a support; where: (a) is a graph showing the change in gas volume over time; (b) is a graph showing the corresponding Transition Frequency (TOF) values; (c) is the reaction time graph; Figure 4 The present invention is PdAu / NH2-NCB H @NGS curves showing the relationship between the volume of gas produced and time in the catalytic dehydrogenation reaction of formic acid at different temperatures, and the corresponding TOF values. Detailed Implementation

[0018] 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.

[0019] Example 1 Step 1: Preparation of graphene oxide (GO); 1) Place 3g of graphite sheets in a large beaker containing 360 mL of a mixture of concentrated sulfuric acid and phosphoric acid (H2SO4 / H3PO4 = 3:1) and stir thoroughly to form a homogeneous mixture; 2) In an ice-water bath environment, slowly add 18 g of potassium permanganate (KMnO4) in batches and continue stirring for 30 min to ensure uniform dispersion.

[0020] 3) The reaction system was transferred to an oil bath at 50 °C and reacted at a constant temperature for 24 h. After the reaction, it was allowed to cool naturally to room temperature. Finally, 400 mL of ice water and 30 mL of hydrogen peroxide (H2O2) were added to the system to control the intense exothermic reaction and to terminate the reaction. The system was then subjected to repeated acid washing, deionized water washing, and centrifugation to obtain a GO aqueous dispersion with a concentration of approximately 10 mg / mL. -1 .

[0021] Step 2: NCB H Preparation of @NGS; 1) Immerse the toner in a 6.0 M nitric acid HNO3 aqueous solution, stir continuously at 90 °C for 3 h, and then rinse repeatedly with deionized water until the pH is neutral; 2) 80 mg CB H 4 mL of GO aqueous dispersion and 10 mg mL-1 GO aqueous dispersion were dispersed in 70 mL of H2O and ultrasonically dispersed for 2 h. 3) Add 1.2 g of urea and stir vigorously for 15 min; 4) Perform a solvothermal reaction at 160 °C for 4 h; after the reaction is complete, wash and dry to obtain NCB. H @NGS.

[0022] Step 3: PdAu / NH2-NCB H Preparation of @NGS catalysts; 1) 50 mg NCB H The NGS carrier was dispersed in 50 mL of water and stirred thoroughly. 2) Add 0.2 mL of 3-aminopropyltriethoxysilane and stir for 1 h; 3) Add 56.4 mM, 1.064 mL K2PdCl4 and 25.39 mM, 1.182 mL HAuCl4, and stir for 1 h; 4) Under vigorous stirring in an ice bath environment, add 5 mL of freshly prepared aqueous solution containing 37.83 mg NaBH4 dropwise to the mixture and stir for 1 h. 5) Finally, the product was filtered with deionized water and freeze-dried overnight to prepare PdAu / NH2-NCB. H @NGS.

[0023] Comparative Example 1 Step 1: Preparation of graphene oxide (GO) 1) Place 3g of graphite sheets in a large beaker containing 360 mL of a mixture of concentrated sulfuric acid and phosphoric acid (H2SO4 / H3PO4 = 3:1) and stir thoroughly to form a homogeneous mixture; 2) In an ice-water bath, slowly add 18 g of potassium permanganate in batches and continue stirring for 30 min to ensure uniform dispersion.

[0024] 3) The reaction system was transferred to an oil bath at 50 °C and reacted at a constant temperature for 24 h. After the reaction, it was allowed to cool naturally to room temperature. Finally, 400 mL of ice water and 30 mL of hydrogen peroxide (H2O2) were added to the system to control the intense exothermic reaction and to terminate the reaction. The system was then subjected to repeated acid washing, deionized water washing, and centrifugation to obtain a GO aqueous dispersion with a concentration of approximately 10 mg / mL. -1 .

[0025] Step 2: NCB H Preparation of @NGS; 1) Immerse the toner in a 6.0 M nitric acid aqueous solution, stir continuously at 90 °C for 3 h, and then rinse repeatedly with deionized water until the pH is neutral; 2) 80 mg CB H 4 mL of 10 mg mL⁻¹ GO was dispersed in 70 mL of H₂O and ultrasonically dispersed for 2 h. 3) Add 1.2 g of urea and stir vigorously for 15 min; 4) Perform a solvothermal reaction at 160 °C for 4 h; after the reaction is complete, wash and dry the product, and name it NCB. H @NGS.

[0026] Step 3: PdAg / NH2-NCB H Preparation of @NGS catalysts; 1) 50 mg NCB H The NGS carrier was dispersed in 50 mL of water and stirred thoroughly. 2) Add 0.2 mL of 3-aminopropyltriethoxysilane and stir for 1 h; 3) Add 0.03 mM K2PdCl4 and 0.02 mM AgNO3.

[0027] 4) Under vigorous stirring in an ice bath environment, add 5 mL of freshly prepared aqueous solution containing 37.83 mg NaBH4 dropwise to the mixture and stir for 1 h. 5) The product was filtered with deionized water and freeze-dried overnight to obtain PdAg / NH2-NCB. H @NGS.

[0028] Comparative Example 2 The preparation method is the same as described above, except that in step 3), 0.03 mM K2PdCl4 and 0.02 mM M LuCl3 are added, ultimately yielding PdRu / NH2-NCB.H @NGS.

[0029] Comparative Example 3 The preparation method is the same as described above, except that in step 3), 0.03 mM K₂PdCl₄ and 0.02 mM H₂PtCl₆ are added, ultimately yielding PdPt / NH₂-NCB. H @NGS.

[0030] Comparative Example 4 The preparation method is the same as described above, except that in step 3), 0.03 mM K2PdCl4 and 0.02 mM MrCl3 are added, ultimately yielding PdIr / NH2-NCB. H @NGS.

[0031] Performance testing PdAu / NH2-NCB prepared in Example 1 H The performance test results of the @NGS catalyst are as follows: 30 ℃, TOF initial 5819 h -1 Formic acid conversion rate 100%; 40 ℃, TOF initial 8570 h -1 Formic acid conversion rate 100%; 50 ℃, TOF initial 12128 h -1 Formic acid conversion rate is 100%.

[0032] PdAg / NH2-NCB prepared in Comparative Example 1 H The performance test results of the @NGS catalyst are as follows: 30 ℃, TOF initial 1344 h -1 Formic acid conversion rate is 100%.

[0033] PdRu / NH2-NCB prepared in Comparative Example 2 H The performance test results of the @NGS catalyst are as follows: 30 ℃, TOF initial 1301 h -1 Formic acid conversion rate is 100%.

[0034] PdPt / NH2-NCB prepared in Comparative Example 3 H The performance test results of the @NGS catalyst are as follows: 30 ℃, TOF initial 1097 h -1 Formic acid conversion rate: 70%.

[0035] PdIr / NH2-NCB prepared in Comparative Example 4 H The performance test results of the @NGS catalyst are as follows: 30 ℃, TOF initial 729 h -1 Formic acid conversion rate is 100%.

[0036] like Figure 1 As shown, for GO and NCB H @NGS and PdAu / NH2-NCB H XPS characterization analysis was performed using NGS. As shown in the figure, the sharp peak at 10.8° in the XRD pattern of GO originates from the (002) diffraction plane of its layered stacked structure. Further analysis using GO and CB... H After self-assembly and combined with a urea-assisted hydrothermal doping process, NCB H The @NGS sample exhibited a broad diffraction signal around 24.5°, confirming the successful reduction of graphene oxide to graphene via urea-assisted solvothermal method. After impregnation with the metal precursor and subsequent reduction treatment, a diffraction peak at 39.2° appeared, intersecting the face-centered cubic (fcc) Au(111) and fcc Pd(111) crystal planes, providing direct evidence for the successful anchoring of PdAu alloy NPs on the support surface. Furthermore, for the PdAu / NH2-NCB sample... H @NGS, the diffraction peak at 38.2° is attributed to the fcc Au(111) crystal plane.

[0037] like Figure 2 As shown, (a, b) represent PdAu / NH2-NCB. H @NGS TEM images, (c) is the HR-TEM image, and (d) is the corresponding particle size distribution. As shown in the figures, the initially synthesized GO exhibits wrinkled characteristics, with irregular edges and a typical layered folded configuration. This structural feature stems from the incomplete adhesion of GO to the substrate. For PdAu / NH2-NCB... H @NGS catalyst, carbon nanospheres can be observed embedded in graphene sheets ( Figure 2 (b) Under the influence of -NH2, which can strongly coordinate with metal ions, PdAu NPs with an average particle size of 2.4 nm are highly dispersed on the support. Furthermore, in PdAu / NH2-NCB... H A lattice fringes of 0.23 nm can be observed in the HRTEM image of @NGS ( Figure 2 c), this value is between the fcc Pd(111) (0.224 nm) and Au(111) crystal plane (0.235 nm), further confirming the formation of PdAu alloy NPs, consistent with the XRD results.

[0038] like Figure 3 As shown, (a) is the result of using NH2-NCB at 303 K without additives. H The volume change of formic acid produced by a series of PdM catalysts prepared using @NGS as a support over time is shown in (b) the corresponding conversion frequency (TOF) value and (c) the reaction time. As can be seen from the figure, although all are noble metal catalysts, the PdAu component exhibits the best activity, mainly due to the following reasons. First, Au optimizes the d-band center of Pd through strong electronic effects, balancing the adsorption and desorption processes. Au's electronegativity (2.54) is higher than Pd's (2.20). After alloying, Au shifts the d-band center of Pd downwards through electron transfer, thereby weakening the reaction of FA and intermediates (HCOO). * The adsorption strength of FA molecules at Pd active sites is considered. Moderate adsorption avoids CO poisoning at active sites caused by excessive adsorption, while maintaining the adsorption capacity required for reactant activation. In contrast, Ag (electronegativity 1.93) has a weaker electronic effect on Pd, while Pt (2.28) or Ir (2.20) have similar electronic structures to Pd, making it difficult to significantly optimize the d-band position. Secondly, Au can induce highly dispersed Pd atoms, forming highly active sites. This can be confirmed by TEM characterization. Au's atomic radius (1.44 Å) is larger than Pd's (1.37 Å), and alloying induces highly dispersed Pd on Au. This structure is beneficial for the selective adsorption and dissociation of FA molecules at Pd sites (such as CH bond breaking). Although Ag (atomic radius 1.45 Å) has a similar atomic size to Pd, the Ag-Pd interaction is weaker, easily forming larger Pd clusters and reducing the density of active sites. Furthermore, Au's high thermal stability (melting point 1064°C) helps maintain the dispersed state of Pd during the reaction, while high-melting-point metals such as Pt (melting point 1768°C) or Ir (melting point 2466°C) may promote Pd sintering, reducing the active surface area. Finally, Au plays a crucial role in suppressing CO adsorption and side reactions, and improving selectivity and durability. The addition of Au significantly reduces the adsorption strength of CO at Pd sites, promoting rapid desorption or oxidation of CO to CO2 (through surface oxygen species), thus avoiding CO poisoning. In contrast, the strong adsorption of CO by Ru or Pt (e.g., high Pt-CO bond energy) easily leads to blockage of active sites. Simultaneously, the Au surface energy inhibits the dehydration of formic acid to form CO (a side reaction), preferentially promoting the dehydrogenation pathway to generate H2 and CO2, improving H2 selectivity.

[0039] like Figure 4 As shown, PdAu / NH2-NCB H @NGS curves showing the relationship between the volume of gas produced and time in the catalytic dehydrogenation reaction of formic acid at different temperatures, and the corresponding TOF. The graph shows that as the reaction temperature increases from 303 K to 323 K, the TOF... initialFrom an upgrade of 5819 h -1 up to 12128 h -1 .

[0040] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing palladium nanocatalysts supported on a three-dimensional support, characterized in that, Pd-based alloy nanoparticles modified with -NH2 grown on a three-dimensional support were prepared by a wet chemical reduction method and used as a formic acid dehydrogenation catalyst at room temperature without additives. The specific steps included: Step 1: Preparation of graphene oxide (GO); Using a modified Hummers method, graphite sheets were partially oxidized with potassium permanganate in an ice-water bath in a concentrated sulfuric acid-phosphoric acid mixture. The oxidation was carried out at 50°C for 24 h, followed by ice-water quenching, hydrogen peroxide oxidation, and repeated acid washing, water washing, and centrifugation to obtain a 10 mg / mL graphene oxide (GO) solution. -1 GO aqueous dispersion; Step 2: NCB H Preparation of @NGS: First, carbon powder was etched with 6.0 M nitric acid at 90 °C for 3 h and then washed with water until neutral to obtain functionalized carbon material CB. H Then CB H NCB was prepared by ultrasonic dispersion of GO aqueous dispersion, hydrothermal treatment with urea at 160 °C for 4 h, filtration, washing with water, and freeze-drying. H @NGS composite carrier; Step 3: PdAu / NH2-NCB H Preparation of @NGS catalyst; NCB H The NGS composite carrier was dispersed in water and stirred thoroughly for 1 h. 3-Aminopropyltriethoxysilane was added and stirred for 1 h. K₂PdCl₄ and HAuCl₄ in a molar ratio of 3:2 were then added and stirred for 1 h. Under vigorous stirring in an ice bath, freshly prepared NaBH₄-containing aqueous solution was added dropwise to the mixture and stirred for 1 h. Finally, the product was filtered with deionized water and freeze-dried overnight to prepare PdAu / NH₂-NCB. H @NGS.

2. The method for preparing palladium nanocatalyst supported on a three-dimensional support according to claim 1, characterized in that, In step 1, potassium permanganate is added in batches in an ice-water bath at a temperature of <5°C. 0.1g of potassium permanganate is added slowly in batches, totaling 18g.

3. The method for preparing palladium nanocatalyst supported on a three-dimensional support according to claim 1, characterized in that, In step 1, the graphite sheets are added to potassium permanganate in batches in an ice-water bath in a concentrated sulfuric acid-phosphoric acid mixture. The mass ratio of graphite sheets to potassium permanganate is 1:6, and the mass ratio of concentrated sulfuric acid to phosphoric acid in the concentrated sulfuric acid-phosphoric acid mixture is 3:

1.

4. The method for preparing palladium nanocatalyst supported on a three-dimensional support according to claim 1, characterized in that, The functionalized carbon material CB obtained in step 2 H The mass is 0.5g; CB H The mass ratio of GO aqueous dispersion and urea is 2:1:

30.

5. The method for preparing palladium nanocatalyst supported on a three-dimensional support according to claim 1, characterized in that, NCB in step 3 H The mass ratio of @NGS composite carrier to water is 1:1; 0.2 mL of 3-aminopropyltriethoxysilane is added.

6. The method for preparing palladium nanocatalyst supported on a three-dimensional support according to claim 1, characterized in that, In step 3, the mass ratio of NaBH4 to the aqueous solution is 1:

125.

7. A three-dimensional supported palladium nanocatalyst, characterized in that, The catalyst is prepared by the method according to any one of claims 1 to 6, wherein the catalyst support is an amino-modified nitrogen-doped carbon black / nitrogen-doped graphene three-dimensional porous composite material, and the active component is palladium bimetallic nanoparticles.

8. The three-dimensional supported palladium nanocatalyst according to claim 7, characterized in that, The catalyst, under additive-free conditions at 30°C, TOF initial 5819h -1 The formic acid conversion rate and H2 selectivity both reached 100%.

Images