A PdNi / PCNS-O-NH2 nanocatalyst, its preparation method and application

Abstract

This invention belongs to the field of hydrogen storage materials technology, specifically relating to a PdNi / PCNS-O-NH2 nanocatalyst, its preparation method, and its application. The method involves obtaining a PCNS-O-NH2 support from porous carbon nanosheets through nitric acid oxidation and amino functionalization. Then, water-based Pd precursor salts, Ni precursor salts, and NaBH4 are sequentially added to the PCNS-O-NH2, mixed thoroughly, and stirred until the reaction is complete, yielding a mixed solution. This solution is then centrifuged, washed, and dried to finally obtain the PdNi / PCNS-O-NH2 nanocatalyst. The preparation method of this invention is simple, easy to implement, and low in cost. The resulting catalyst is small in size, uniformly dispersed, exhibits high catalytic activity, excellent cycle stability, is easy to recover, and can be reused, making it a catalyst with great application prospects.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen storage materials technology, specifically relating to a PdNi / PCNS-O-NH2 nanocatalyst, its preparation method, and its application. Background Technology

[0002] With increasingly prominent environmental problems and dwindling fossil fuel supplies, the development of clean and renewable energy is imperative, yet challenging. Hydrogen (H2) is considered one of the most promising solutions due to its renewable nature and high energy density. However, its safe and efficient large-scale storage and release remain among the biggest challenges. Formic acid (FA) is a major liquid product of biomass processing, and especially as a liquid organic hydrogen carrier, it has become a promising renewable liquid organic hydrogen carrier due to its large volumetric capacity, low toxicity, good flammability, and convenient storage and transportation. Therefore, FA should selectively decompose and release H2 via the decomposition pathway (HCOOH → H2 + CO2) rather than the dehydration pathway (HCOOH → H2O + CO). However, the selective decomposition reaction of formic acid still heavily relies on noble metal catalysts, such as Pd (ChemEng J, 2022,429: 132388; JMater Chem A, 2019, 7(45): 25791-25795) and Au (J Am Chem Soc, 2012,134(21): 8926-8933; J Mater Chem, 2012, 22(25): 12582-12586). These noble metal catalysts are expensive and scarce, greatly hindering their widespread application. Developing non-noble metal catalysts is highly attractive in order to save on catalyst costs. However, to date, the activity and stability of Pd-based catalysts containing non-noble metals remain poor at high temperatures, especially without additional additives (such as HCOONa). Therefore, developing a simple and effective catalyst with low noble metal content and high efficiency and stability is key to realizing the practical application of formic acid as a liquid organic hydrogen carrier.

[0003] Carbon-based materials are widely used as catalyst supports due to their large specific surface area, high porosity, and excellent performance. In particular, the two-dimensional structure of two-dimensional (2D) porous carbon facilitates the exposure of active sites, promotes mass transfer, and shortens the diffusion path of substrate molecules, thereby improving reaction performance. However, the template method commonly used to synthesize carbon materials currently suffers from low yields, hindering large-scale applications. Furthermore, its hydrophobic surface leads to poor dispersion in aqueous solutions, and the lack of functional groups on the surface impedes interaction with supported metal nanoparticles (NPs). In addition, current methods for preparing ultrasmall metal nanoclusters (NCs) require high temperatures, long durations, or complex processes, significantly impeding their large-scale practical application. Therefore, developing a simple, high-yield method for synthesizing porous carbon and implementing low-temperature, controllable surface modification of carbon materials to prepare ultrafine and highly dispersed NCs is of great significance for improving the activity of FA decomposition reactions. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing catalysts, such as low catalytic stability, which is detrimental to practical applications. This invention provides a PdNi / PCNS-O-NH2 nanocatalyst, its preparation method, and its applications. Specifically, the following technical solution is adopted:

[0005] A method for preparing a PdNi / PCNS-O-NH2 nanocatalyst includes the following steps:

[0006] Step 1: Place porous carbon nanosheets PCNS in HNO3 solution and stir in an oil bath to carry out the reaction. After the reaction is completed, cool, centrifuge, wash until neutral, and dry to obtain PCNS-O;

[0007] Step 2: Place PCNS-O in anhydrous toluene, then add APTES (3-aminopropyltriethoxysilane), and reflux the reaction in an oil bath. After the reaction is complete, cool, centrifuge, wash, and vacuum dry to obtain PCNS-O-NH2.

[0008] Step 3: Pd precursor salt, Ni precursor salt and NaBH4 are added sequentially to PCNS-O-NH2 and stirred until the reaction is complete to obtain a mixed solution. Then, PdNi / PCNS-O-NH2 nanocatalyst is obtained by centrifugation, washing and drying.

[0009] This invention utilizes porous nitrogen-doped carbon treated with nitric acid oxidation and amino functionalized as a support, and non-noble metal Ni and noble metal Pd as active components. An ultrafine and highly dispersed PdNi NCs composite material supported on oxygen- and amino-functionalized PCNS-O-NH2 is prepared via a simple impregnation co-reduction method. Due to the alloying synergy between the non-noble metal and the noble metal, the catalyst exhibits superior activity. Furthermore, because nanoparticles (NPs) or nanoclusters (NCs) have very high surface energy, they are generally thermodynamically unstable and prone to aggregation, leading to a decrease in catalytic activity. To avoid aggregation, various support materials, such as graphene, metal-organic frameworks (MOFs), and zeolites, are used to stabilize the ultrasmall metal NCs. This PCNS-O-NH2 support not only prevents the aggregation of metal NPs but also enhances the catalytic activity of metal NPs due to the strong metal-support interaction. Building upon this, the use of porous nitrogen-doped carbon with a relatively large specific surface area, treated with nitric acid oxidation and amino functionalized, as a support further improves the dispersion of active particles and reduces particle size, thereby enhancing the catalytic activity of the catalyst. The catalyst prepared by this invention exhibits superior activity compared to other commercially available carbon materials that have undergone the same post-treatment and loading process to produce PdNi catalysts. The PdNi bimetallic NPs supported on PCNS demonstrate superior catalytic performance compared to other catalyst materials. For PdNi / PCNS-O-NH2, at 323 K, 120 mL of gas (H2+ CO2) can be released in just 0.83 min, with a corresponding TOF value reaching 5521 h. -1 The activities of PdNi / KotchenHei-O-NH2, PdNi / Carbonpower-O-NH2, PdNi / XC-72-O-NH2, and PdNi / Activatedcharcoal-O-NH2 were 2.2, 3.3, 7.0, and 16.7 times greater than those of PdNi / KotchenHei-O-NH2, PdNi / Carbonpower-O-NH2, PdNi / XC-72-O-NH2, and PdNi / Activatedcharcoal-O-NH2, respectively, under the same measurement conditions.

[0010] The formation mechanism of ultrasmall PdNi NCs in PdNi / PCNS-O-NH2 is as follows: HNO3 treatment of PCNS introduces oxygen-containing functional groups onto the PCNS surface; under ultrasonic conditions, the oxygen functional groups in PCNS react with the Si-OH groups generated by the hydrolysis of APTES, and amino groups (-NH2) are readily adsorbed onto the PCNS surface. Ni can be effectively adsorbed onto the PCNS surface through charge interactions. 2+ and Pd 2+ Ions serve as initial nucleation sites; then Ni 2+ and Pd 2+In the presence of NaBH4, ions are directly reduced to form ultra-small PdNi NCs; the formed NiPd NCs are fixed on the surface of PCNS and covered by excess APTES, thereby preventing them from agglomerating into larger NCs or NPs, resulting in the formation of ultra-small and well-dispersed PdNi NCs.

[0011] In the above preparation method, the Ni precursor salt is at least one of nickel chloride hexahydrate, nickel sulfate hexahydrate, or nickel nitrate hexahydrate; the Pd precursor salt is at least one of sodium tetrachloropalladate, palladium chloride, or palladium nitrate.

[0012] As a further preferred embodiment, PCNS is specifically prepared by the following steps:

[0013] First, SiO2 is dispersed in toluene and ultrasonically stirred. Then, APTES is added, and the reaction is carried out under reflux in an oil bath. After the reaction is completed, the mixture is cooled, centrifuged, washed, and vacuum dried to obtain SiO2-NH2. Then, anhydrous glucose and water are added to SiO2-NH2, stirred, and hydrothermally reacted at 180℃ for 12 h. After the reaction is completed, the mixture is cooled to room temperature, centrifuged, washed, and vacuum dried. It is then calcined at 800℃ for 2 h under an Ar atmosphere. After cooling, the SiO2 template agent is removed by etching with 2 M NaOH solution at 70℃ to obtain PCNS. The preparation method of this invention is simple and has a high yield. The prepared PCNS is a porous two-dimensional material with a large specific surface area and an easy surface modification by functional groups. Furthermore, the PdNi nanoparticles supported after nitric acid oxidation and amino functionalization are uniformly dispersed and ultrafine, exhibiting excellent catalytic activity for the decomposition of formic acid to produce hydrogen, which is superior to the catalytic activity of most commercially available carbon-supported PdNi catalysts.

[0014] The SiO2 mentioned above is obtained through the following steps:

[0015] Tetraethyl orthosilicate was dissolved in a beaker containing a mixed solvent of n-pentanol and cyclohexane and stirred magnetically until homogeneous; this mixture is designated as the oil phase. Hexadecyl bromide pyridine and urea were dissolved in deionized water and stirred magnetically until homogeneous; this mixture is designated as the aqueous phase. The oil phase was slowly added dropwise to the aqueous phase under rapid, vigorous stirring. After vigorous stirring at room temperature, the mixture was transferred to a reaction vessel and placed in a preheated oven at 120 °C. After hydrothermal treatment for a period of time, the mixture was cooled to room temperature, filtered, and washed three times each with deionized water and ethanol. It was then dried in an oven overnight, ground until homogeneous, and calcined in a muffle furnace at 550 °C for 6 h at a heating rate of 3 °C / min. After cooling, it was ground again to obtain SiO2. The SiO2 synthesized by this method has a high yield and a large specific surface area. Scanning electron microscopy revealed a two-dimensional lamellar structure with clearly visible pores on the surface, which is beneficial for subsequent surface modification treatments.

[0016] As a further preferred embodiment, the total molar amount of the Ni precursor salt and the Pd precursor salt in step 3 is 0.1 mmol, wherein the molar ratio of Pd to Ni is 2:8 to 9:1. More preferably, the molar ratio of Pd to Ni is 8:2. The activity of the catalyst prepared by this invention first increases and then decreases with the molar ratio of Pd to Ni. This is mainly because Pd is an active metal for catalyzing the decomposition of formic acid to produce hydrogen, while Ni has no activity for catalyzing the decomposition of formic acid to produce hydrogen. When the molar amount of Pd is relatively small, the activity is low. When the molar ratio of Pd to Ni is 8:2, the catalytic activity for the decomposition of formic acid to produce hydrogen is optimal.

[0017] As a further preferred embodiment, the ratio of APTES in step 2 to NaBH4 in step 3 is 3 mL~12 mL: 30 mg~70 mg. More preferably, the ratio of APTES in step 2 to NaBH4 in step 3 is 6 mL: 40 mg. The catalyst activity obtained by the present invention first increases and then decreases with the amount of APTES. When the amount of APTES is very small, the selectivity and activity of the catalyst are relatively low because the amino functional groups generated by APTES hydrolysis are few and insufficient to anchor more active metals. When the amount of APTES is 6 mL, the catalyst has the highest catalytic activity, indicating that when the amount is too large, APTES covers part of the metal active sites. Because the amino functional groups provided by APTES hydrolysis can be grafted onto the support as Brønsted basic sites and act as proton scavengers to break the CH bonds of formic acid, thereby accelerating the dehydrogenation of formic acid.

[0018] The present invention also provides a PdNi / PCNS-O-NH2 nanocatalyst, wherein the loading of metallic PdNi in the catalyst is 5.7~20 wt%.

[0019] As a further preferred embodiment, the loading of metallic PdNi in the above-mentioned PdNi / PCNS-O-NH2 nanocatalyst is 13.9 wt%. The catalytic reaction rate of the nanocatalyst prepared by the present invention shows a trend of first increasing and then decreasing with the increase of metallic PdNi loading. When the loading is 13.9 wt%, the PdNi / PCNS-O-NH2 nanocatalyst exhibits the best performance for the decomposition of formic acid to produce hydrogen. This is mainly because, on the one hand, when the PdNi metal loading is lower than 13.9 wt% (e.g., 10.8 wt%), the excess PCNS-O-NH2 and the abundant -NH2 groups (important interaction sites of metal NCs) can provide more anchoring sites, hindering the excessive growth and aggregation process of PdNi NCs. The excess PCNS-O-NH2 will also block the active sites of PdNi NCs, resulting in imperfect mass transfer efficiency. On the other hand, when the PdNi metal loading exceeds 13.9 wt% (e.g., 16.2 wt%), the smaller number of PCNS-O-NH2 and -NH2 groups cannot provide sufficient interaction sites to stabilize the dispersed PdNiNCs.

[0020] The PdNi nanoclusters prepared in this invention have an average particle size of 1.4 ± 0.5 nm. The ultrafine PdNi nanoclusters with an average particle size of approximately 1.4 nm are uniformly distributed on the PCNS-O-NH2 support, resulting in excellent catalytic activity in the final nanocatalyst.

[0021] The PdNi / PCNS-O-NH2 nanocatalyst prepared in this invention can be applied to hydrogen source production in fuel cells. The catalyst catalyzes the decomposition of formic acid to produce hydrogen at a temperature of 303 K-333 K. Since the catalytic reaction takes place in solution, excessively high temperatures can lead to water evaporation, increasing the concentration of formic acid and making its decomposition more difficult. Therefore, the catalytic temperature should not be too high. At 323 K, the PdNi / PCNS-O-NH2 catalyst prepared without any additives rapidly catalyzes the decomposition of formic acid to produce hydrogen, with a TOF value as high as 5521 h⁻¹. -1 100% H2 selectivity.

[0022] The beneficial effects of this invention are as follows: This invention uses porous nitrogen-doped carbon as a support, with non-noble metal Ni and noble metal Pd as active components. Due to the synergistic effect between the non-noble metal and the noble metal, the catalyst exhibits superior activity. Simultaneously, by using porous nitrogen-doped carbon with a relatively large specific surface area, and after nitric acid oxidation treatment and amino functionalization, the dispersion of active particles is improved and the particle size is reduced, further enhancing the catalytic activity of the catalyst. The preparation method of this invention is simple, easy to implement, and low in cost. The prepared nitrogen-doped porous carbon has a large specific surface area, uniform mesoporous channels, and high yield. The prepared catalyst is small in size and uniformly dispersed, exhibits high catalytic activity, excellent cycle stability, is easy to recover, and can be reused, showing good application prospects. Furthermore, the PdNi / PCNS-O-NH2 catalyst prepared at 323 K without any additives rapidly catalyzes the decomposition of formic acid to produce hydrogen, with a TOF value as high as 5521 h⁻¹. -1 With 100% H2 selectivity, it still maintains high activity after 20 cycles, making it a catalyst with great application prospects. Attached Figure Description

[0023] Figure 1 The image shown is a transmission electron microscope image of the composite nanocatalyst PdNi / PCN-O-NH2 obtained in Example 1 (the inset is a particle size distribution diagram of PdNi NCs).

[0024] Figure 2 The image shown is a scanning electron microscope image of silica and nitrogen-doped porous carbon (PCNS) obtained in Example 1 (left image is silica, right image is PCNS).

[0025] Figure 3 The image shows the polycrystalline X-ray diffraction patterns of the composite nanocatalyst PdNi / PCN-O-NH2 obtained in Example 1 and its comparative sample.

[0026] Figure 4 The image shown is a transmission electron microscope (TEM) image of the composite nanocatalyst PdNi / PCN-O-NH2 obtained in Example 1 and its comparative sample (inset is a particle size distribution map).

[0027] Figure 5 The left figure shows the N2 adsorption-desorption isotherm of the PdNi / PCN-O-NH2 catalyst obtained in Example 1, and its corresponding pore size distribution (right figure).

[0028] Figure 6 The image shows the photoelectron spectra of the composite nanocatalyst PdNi / PCNS-O-NH2 obtained in Example 1 and its comparative sample (the left image is the Pd 3d spectrum, and the right image is the Ni 2p spectrum).

[0029] Figure 7The figure shown is a graph of the catalytic performance test of the composite nanocatalyst PdNi / PCNS-O-NH2 obtained in Examples 1-5 on formic acid decomposition at 323 K;

[0030] Figure 8 The figure shows the test results of the composite nanocatalyst PdNi / PCNS-O-NH2 with different metal loadings for the decomposition of formic acid obtained in Examples 1 and 7-10.

[0031] Figure 9 The figure shown is a graph of the catalytic performance of the PdNi / PCNS-O-NH2 composite nanocatalysts prepared in Examples 1 and 11-14 for the production of hydrogen from formic acid.

[0032] Figure 10 The figure shown is a graph of the catalytic performance of each composite nanocatalyst obtained in Example 1 and Example 15 at 323 K for the decomposition of formic acid.

[0033] Figure 11 The figure shown is a graph of the catalytic performance of the composite nanocatalyst PdNi / PCNS-O-NH2 obtained in Example 1 at different temperatures for the decomposition of formic acid.

[0034] Figure 12 The figure shown is a test diagram of the catalytic decomposition and recycling of formic acid by the composite nanocatalyst PdNi / PCNS-O-NH2 obtained in Example 1 at 323 K;

[0035] Figure 13 The figure shows the system before and after recycling of the composite nanocatalyst PdNi / PCNS-O-NH2 obtained in Example 1 at 323 K for the decomposition of formic acid. 13 CNMR spectra (left image is before the reaction, right image is after 20 reactions). Detailed Implementation

[0036] The following will provide a clear and complete description of the concept, specific structure, and technical effects of the present invention in conjunction with the embodiments and accompanying drawings, so as to fully understand the purpose, solution, and effects of the present invention.

[0037] Example 1

[0038] A method for preparing a PdNi / PCNS-O-NH2 nanocatalyst, specifically including the following steps:

[0039] Step 1: Synthesis of SiO2 nanosheets: Dissolve 10 g of tetraethyl orthosilicate in a beaker containing 6 mL of n-pentanol and 120 mL of cyclohexane, and stir magnetically until homogeneous. This mixture is referred to as the oil phase. Dissolve 4 g of hexadecyl bromide pyridine and 2.4 g of urea in 120 mL of deionized water, and stir magnetically until homogeneous. This mixture is referred to as the aqueous phase. Slowly add the oil phase dropwise to the aqueous phase under rapid and vigorous stirring. After vigorous stirring at room temperature for 30 min, transfer the mixture to a reaction vessel and place it in a high-temperature oven preheated to 120 °C. After hydrothermal treatment for 6 h, cool to room temperature, filter, and wash three times each with deionized water and ethanol. Dry in an oven overnight, and then calcine in a muffle furnace at 550 °C for 6 h at a heating rate of 3 °C / min.

[0040] Step 2: Synthesis of porous nitrogen-doped carbon nanosheets (PCNS): 1 g SiO2 was dispersed in a round-bottom flask containing toluene, sonicated for 10 min, magnetically stirred for 20 min, and then 5 mL APTES was added. The mixture was refluxed in an oil bath at 80 ℃ for 12 h. After cooling, it was centrifuged, washed, and dried in a vacuum oven to obtain aminated silica (SiO2-NH2). 1 g SiO2-NH2 was placed in a 200 mL reactor, then 2 g anhydrous glucose was added, followed by 75 mL deionized water. After magnetic stirring for 30 min, it was placed in a high-temperature oven and hydrothermally reacted at 180 ℃ for 12 h. After cooling to room temperature, it was centrifuged, washed, and dried in a vacuum oven. After drying, it was placed in a porcelain boat and calcined in a tube furnace under an Ar atmosphere at 800 ℃ for 2 h, with a heating rate of 3 ℃ / min. After cooling, the SiO2 template agent was removed by etching with 2 M NaOH solution at 70 ℃ for 12 h.

[0041] Step 3, Oxygen-functionalized PCNS (PCNS-O): Weigh 1 g of PCNS and mix it with 100 mL of 5 mol / L HNO3 to obtain a mixed solution of PCNS and HNO3. Stir at 40 °C for 7 h, cool, centrifuge and wash until neutral, and dry to obtain PCNS-O.

[0042] Step 4, Aminofunctionalization of PCNS-O (PCNS-O-NH2): Place PCNS-O in 80 mL of anhydrous toluene, add 6 mL of APTES, reflux at 80 °C in an oil bath for 12 h, cool, centrifuge and wash, and vacuum dry to obtain PCNS-O-NH2.

[0043] Step 5: Weigh 60 mg of PCNS-O-NH2, add 4 mL of H2O, and sonicate to mix evenly. Then add 0.08 mmol of Pd precursor salt and 0.02 mmol of Ni precursor salt, sonicate to mix evenly, and then add 40 mg of NaBH4. Stir until the reaction is complete. Finally, centrifuge and wash until neutral, separate and dry to obtain PdNi / PCNS-O-NH2 catalyst.

[0044] Example 2

[0045] In Example 1, step 5, which involved adding 0.08 mmol of Pd precursor salt and 0.02 mmol of Ni precursor salt, was replaced with adding 0.09 mmol of Pd precursor salt and 0.01 mmol of Ni precursor salt. The other steps were the same as in Example 1, resulting in a PdNi / PCNS-O-NH2 composite nanocatalyst with a Pd to Ni molar ratio of 9:1.

[0046] Example 3

[0047] In Example 1, step 5, the addition of 0.08 mmol Pd precursor salt and 0.02 mmol Ni precursor salt was changed to 0.06 mmol Pd precursor salt and 0.04 mmol Ni precursor salt. The other steps were the same as in Example 1, resulting in a PdNi / PCNS-O-NH2 composite nanocatalyst with a Pd to Ni molar ratio of 6:4.

[0048] Example 4

[0049] In Example 1, step 5, the addition of 0.08 mmol Pd precursor salt and 0.02 mmol Ni precursor salt was changed to 0.04 mmol Pd precursor salt and 0.06 mmol Ni precursor salt. The other steps were the same as in Example 1, resulting in a PdNi / PCNS-O-NH2 composite nanocatalyst with a Pd to Ni molar ratio of 4:6.

[0050] Example 5

[0051] In Example 1, step 5, the addition of 0.08 mmol Pd precursor salt and 0.02 mmol Ni precursor salt was changed to 0.02 mmol Pd precursor salt and 0.08 mmol Ni precursor salt, while the other steps were the same as in Example 1, to obtain a PdNi / PCNS-O-NH2 composite nanocatalyst with a Pd to Ni molar ratio of 2:8.

[0052] Example 6

[0053] In Example 1, step 5, adding 40 mg of NaBH4 was replaced with adding 70 mg of NaBH4, while the other steps remained the same as in Example 1, resulting in a PdNi / PCNS-O-NH2 composite nanocatalyst with a Pd to Ni molar ratio of 8:2.

[0054] Example 7

[0055] In Example 1, the step 5, weighing 60 mg of the solid obtained in step 2, was changed to weighing 160 mg of the solid obtained in step 2. The other steps were the same as in Example 1, resulting in a PdNi / PCNS-O-NH2 composite nanocatalyst with a metal PdNi loading of 5.7 wt%.

[0056] Example 8

[0057] In Example 1, step 5, weighing 60 mg of the solid obtained in step 4, was changed to weighing 80 mg of the solid obtained in step 4. Other steps were the same as in Example 1, resulting in a PdNi / PCNS-O-NH2 composite nanocatalyst with a PdNi loading of 10.8 wt%.

[0058] Example 9

[0059] In Example 1, step 5, weighing 60 mg of the solid obtained in step 4, was changed to weighing 70 mg of the solid obtained in step 4. The other steps were the same as in Example 1, resulting in a PdNi / PCNS-O-NH2 composite nanocatalyst with a metal PdNi loading of 12.2 wt%.

[0060] Example 10

[0061] In Example 1, step 5, weighing 60 mg of the solid obtained in step 4, was changed to weighing 50 mg of the solid obtained in step 4. The other steps were the same as in Example 1, resulting in a PdNi / PCNS-O-NH2 composite nanocatalyst with a metal PdNi loading of 16.2 wt%.

[0062] Example 11

[0063] In Example 1, step 4, which involved adding 6 mL of APTES, was changed to adding 0 mL of APTES. The other steps were the same as in Example 1, resulting in a PdNi / PCNS-O-NH2 composite nanocatalyst with a Pd to Ni molar ratio of 8:2 and a metal loading of 13.9 wt%.

[0064] Example 12

[0065] In Example 1, step 4, which involved adding 6 mL of APTES, was changed to adding 3 mL of APTES. The other steps were the same as in Example 1, resulting in a PdNi / PCNS-O-NH2 composite nanocatalyst with a Pd to Ni molar ratio of 8:2 and a metal loading of 13.9 wt%.

[0066] Example 13

[0067] In Example 1, step 4, which involved adding 6 mL of APTES, was changed to adding 9 mL of APTES. The other steps were the same as in Example 1, resulting in a PdNi / PCNS-O-NH2 composite nanocatalyst with a Pd to Ni molar ratio of 8:2 and a metal loading of 13.9 wt%.

[0068] Example 14

[0069] In Example 1, step 4, which involved adding 6 mL of APTES, was changed to adding 12 mL of APTES. The other steps were the same as in Example 1, resulting in a PdNi / PCNS-O-NH2 composite nanocatalyst with a Pd to Ni molar ratio of 8:2 and a metal loading of 13.9 wt%.

[0070] Example 15

[0071] The PCNS synthesized in steps 1 and 2 of Example 1 were replaced with commercially available carbon materials (Kotchen Hei, Carbon Power, XC-72, and Activatedcharcoal), while the other steps were the same as in Example 1, resulting in various composite nanocatalysts (PdNi / Kotchen Hei-O-NH2, PdNi / CarbonPower-O-NH2, PdNi / XC-72-O-NH2, and PdNi / Activatedcharcoal-O-NH2) with a Pd to Ni molar ratio of 8:2 and a metal loading of 13.9 wt%.

[0072] Example 16

[0073] The present invention has performed relevant characterization data on some of the materials obtained in the above embodiments, as detailed below:

[0074] Figure 1 The image shown is a transmission electron microscope (TEM) image of the composite nanocatalyst PdNi / PCN-O-NH2 obtained in Example 1 (inset shows the particle size distribution of PdNi NCs). Figure 1 It can be seen that the fine PdNi nanoclusters catalyst is uniformly dispersed on the two-dimensional sheet-like PCN-O-NH2 support, with a particle size of about 1.4 nm.

[0075] Figure 2The image shown is a scanning electron microscope image of the silica and nitrogen-doped porous carbon nanosheets (PCNS) obtained in Example 1. Figure 2 It can be seen that the synthesized silica and PCNS are both two-dimensional sheet structures with clearly visible surface pores.

[0076] Figure 3 The image shows the polycrystalline X-ray diffraction patterns of the composite nanocatalyst PdNi / PCN-O-NH2 obtained in Example 1 and its comparative sample. Figure 3 It can be seen that all catalysts exhibit a broad peak around 24.9°, which is attributed to the (002) crystal plane of amorphous carbon. No Ni or Pd diffraction peaks were observed in PdNi / PCNS, PdNi / PCNS-O, PdNi / PCNS-NH2, and PdNi / PCNS-O-NH2, but a broad peak between Pd (111) and Ni (111) was observed, indicating the formation of a PdNi alloy structure.

[0077] Figure 4 The image shown is a transmission electron microscope (TEM) image of the composite nanocatalyst PdNi / PCN-O-NH2 obtained in Example 1 and its comparative sample. Figure 4 It was found that PdNi NCs with an average particle size of 1.7 nm were uniformly dispersed on PCNS-NH2, providing abundant and accessible active sites for FA molecules. In contrast, larger PdNi NPs were observed in PdNi / PCNS, with an average size of 3.2 nm. This indicates that the well-distributed and ultrafine PdNi NCs in PdNi / PCNS-NH2 can be attributed to the surface amino groups in PCNS, which effectively stabilize PdNi NCs and prevent their aggregation into larger particles. Compared to PdNi / PCNS, the average particle size of PdNi NPs in PdNi / PCNS-O was 2.3 nm; compared to PdNi / PCNS-NH2, PdNi NCs in PdNi / PCNS-O-NH2 showed the smallest particle size, with an average particle size of 1.4 nm. This demonstrates that the treatment of PCNS with HNO3 and the functionalization of APTES play a crucial role in controlling the growth of PdNi NPs and in anchoring and stabilizing them.

[0078] Figure 5 The figure shows the N2 adsorption-desorption isotherms (left) and the corresponding pore size distribution (right) of the PdNi / PCN-O-NH2 catalyst obtained in Example 1. Figure 5All five samples exhibited type IV isotherms, with significant capillary condensation within the P / P0 range of 0.5 to 1.0, indicating that the nanosheets contain a relatively uniform mesoporous structure. Compared to the original PCNS, the specific surface area and pore volume of PCNS-O, PCNS-O-NH2, and PdNi / PCNS-O-NH2 decreased sequentially, indicating that PCNS was successfully modified by oxygen-containing functional groups and −NH2 groups, and the porous portion of the PCNS nanosheets was occupied by ultrafine and dispersed PdNi NCs.

[0079] Figure 6 The image shows the photoelectron spectra of the composite nanocatalyst PdNi / PCNS-O-NH2 obtained in Example 1 and its comparative sample (left image is the Pd 3d spectrum, right image is the Ni 2p spectrum). Figure 6 It can be seen that Pd and Ni in PdNi / PCNS-O-NH2 exist in the metallic state, where Pd 0 3D 5 / 2 and Pd 0 3D 3 / 2 Ni appeared at 336.1 eV and 341.4 eV respectively. 0 2p 3 / 2 and Ni 0 2p 1 / 2 They appeared at 853.5 eV and 870.6 eV, respectively. There were also small amounts of Pd. 2+ and Ni 2+ Pd 2+ 3D 5 / 2 At 336.9 eV, Pd 2+ 3D 3 / 2 At 342.1 eV, Ni 2+ Appearing at 857.2 and 874.8 eV. Small amounts of Pd. 2+ and Ni 2+ This can be attributed to the partial oxidation of surface Pd and Ni atoms during XPS sample preparation. In contrast, the Pd 3d peak in PdNi / PCNS-O-NH2 shifts to a lower binding energy compared to Pd / PCNS-O-NH2. Furthermore, the Ni 2p binding energy in PdNi / PCNS-O-NH2 shifts to a higher binding energy compared to Ni / PCNS-O-NH2, indicating that some electrons transfer from Ni to Pd in ​​PdNi / PCNS-O-NH2, making the Pd surface electron-rich, which facilitates the breaking of C-H bonds in FA.

[0080] Example 17

[0081] The composite nanocatalysts obtained in Examples 1, 2, 3, 4, and 5 were used for the decomposition of formic acid to produce hydrogen. The catalysts were placed in a 50 mL three-necked flask containing 4 mL of ultrapure water, and then formic acid was added. The reaction was carried out at 323 K (results are shown in Figure 1). Figure 7 As shown in the figure), the following results were obtained after the completion (Table 1):

[0082] Table 1. Summary of the catalytic performance of the composite nanocatalysts obtained in Examples 1, 2, 3, 4 and 5 for hydrogen production from formic acid decomposition.

[0083]

[0084] The results in Table 1 show that the catalytic activity is strongly dependent on the Pd / Ni molar ratio. Compared with single-metal Pd, the catalytic activity is improved due to the introduction of Ni and alloying with Ni. Figure 7 The catalytic activity increased with increasing Pd molar content; however, further increases in Pd content led to a significant decrease in activity, and single-metal Ni showed no activity. When the Pd:Ni molar ratio was 8:2, the Pd8Ni2 / PCNS-O-NH2 catalyst exhibited the best activity among all tested catalysts, producing the theoretical amount of formic acid in only 0.87 min at 323 K, with a hydrogen production rate of 100%. This indicates that the alloying effect between nickel and palladium plays a positive synergistic role in the formic acid decomposition reaction. Furthermore, the PdNi / PCNS-O-NH2 catalyst showed the best catalytic activity for hydrogen production from formic acid decomposition when nPd:nNi was 8:2.

[0085] Example 18

[0086] The composite nanocatalysts obtained in Examples 1, 7, 8, 9, and 10 were used for the decomposition of formic acid to produce hydrogen. The catalysts were placed in a 50 mL three-necked flask containing 4 mL of ultrapure water, and then formic acid was added. The reaction was carried out at 323 K (results are shown in Figure 1). Figure 8 As shown in the figure), the following results were obtained after the completion (Table 2):

[0087] Table 2. Summary of PdNi / PCNS-O-NH2 composite nanocatalysts prepared in Examples 1 and 7-10 for the catalytic hydrogen production from formic acid.

[0088]

[0089] The results in Table 2 show that the PdNi / PCNS-O-NH2 composite nanocatalysts with different metal loadings all exhibited good activity in the formic acid decomposition reaction, with the best activity observed at a metal loading of 13.9 wt%. This is mainly because: when the PdNi metal loading is below 13.9 wt% (e.g., 10.8 wt%), the excess PCNS-O-NH2 may block the active sites of PdNi NCs, leading to imperfect mass transfer efficiency; when the PdNi metal loading exceeds 13.9 wt% (e.g., 16.2 wt%), the relatively small amount of PCNS-O-NH2, along with the relatively small number of -NH2 groups, is insufficient to provide enough interaction sites to stabilize the dispersed PdNi NCs.

[0090] Example 19

[0091] The PdNi / PCNS-O-NH2 composite nanocatalysts obtained in Examples 1 and 11-14 were used to catalyze the decomposition of formic acid to produce hydrogen at 323 K. The catalyst was placed in a three-necked flask containing 4 mL of ultrapure water, and then formic acid was added to carry out the reaction (results are shown below). Figure 9 As shown in the figure), the following results were obtained after the completion (Table 3):

[0092] Table 3. Summary of PdNi / PCNS-O-NH2 composite nanocatalysts prepared in Examples 1 and 11-14 for the catalytic hydrogen production from formic acid.

[0093]

[0094] Table 3 shows that APTES significantly promotes the formic acid decomposition reaction catalyzed by the PdNi / PCNS-O-NH2 composite nanocatalyst. All nanocatalysts exhibited good activity after APTES functionalization, with the optimal activity observed at 6 mL of APTES. Without APTES, the PdNi / PCNS-O-NH2 composite nanocatalyst exhibited very low catalytic activity and hydrogen production rate for the formic acid decomposition reaction. This is because the amino functional groups grafted onto the PCN-O surface can stabilize the PdNi nanoclusters, and the PdNi nanoclusters are reduced by NaBH4 at room temperature. 2+ Ni 2+ During the process, the PdNi nanoclusters maintain a relatively small particle size, protecting them from aggregation during subsequent catalytic reactions. Furthermore, the amino functional groups can act as Brønsted basic sites, promoting the deprotonation of formic acid to formate intermediates, while the surrounding ultrasmall PdNi nanoclusters catalytically activate the C-H bond breaking of the resulting formate species, thereby enhancing the catalytic activity of the formic acid decomposition reaction.

[0095] Example 20

[0096] The composite nanocatalysts obtained in Examples 1 and 15 were used to catalyze the decomposition of formic acid to produce hydrogen at 323 K. The catalysts were placed in a three-necked flask containing 4 mL of ultrapure water, and then formic acid was added to carry out the reaction (results are shown below). Figure 10 As shown in the figure), the following results were obtained after the completion (Table 4):

[0097] Table 4. Summary of the composite nanocatalysts prepared in Examples 1 and 15 for the catalytic production of hydrogen from formic acid.

[0098]

[0099] Table 4 shows that after commercially purchased carbon materials underwent the same nitric acid oxidation and amino functionalization processes as PCNS, and were then loaded with PdNi nanoparticles to catalyze the decomposition of formic acid, the PdNi bimetallic NPs loaded on PCNS exhibited superior catalytic performance compared to other catalyst materials. This is because the synthesized PCNS material presents a two-dimensional sheet-like structure with a porous surface, which is more conducive to exposing more active sites, thereby anchoring more nanoparticles and improving the activity of formic acid decomposition to hydrogen production.

[0100] Example 21

[0101] The PdNi / PCNS-O-NH2 composite nanocatalyst obtained in Example 1 was used to catalyze the decomposition of formic acid to produce hydrogen at five different reaction temperatures. The catalyst was placed in a three-necked flask containing 4 mL of ultrapure water, and then formic acid was added. The reaction was carried out at different temperatures (results are shown in Figure 1). Figure 11 As shown in the figure), the following results were obtained after the completion (Table 5):

[0102] Table 5. Summary of the catalytic performance of the PdNi / PCNS-O-NH2 composite nanocatalyst obtained in Example 1 at different reaction temperatures for the decomposition of formic acid to produce hydrogen.

[0103]

[0104] The results in Table 5 show that the activity of the PdNi / PCNS-O-NH2 composite nanocatalyst in the formic acid decomposition to hydrogen production increases with increasing temperature. This is because the formic acid decomposition to hydrogen production is exothermic, and increasing the temperature favors this process.

[0105] Example 22

[0106] The PdNi / PCNS-O-NH2 catalyst obtained in Example 1 was tested for its recyclability at 323 K. After the formic acid was completely decomposed, an equal amount of formic acid was added to the flask to test the recyclability of the PdNi / PCNS-O-NH2 catalyst in catalyzing the decomposition of formic acid to produce hydrogen. See details below. Figure 12After 20 cycles of PdNi / PCNS-O-NH2 catalyzed FDR testing, the filtrates before and after the reaction were tested. 13 CNMR spectroscopy showed that no FA was detected in the filtrate after 20 cycles of testing. 13 CNMR spectral signal, results as follows Figure 13 As shown in the figure. Multiple cycle tests show that the synthesized PdNi / PCNS-O-NH2 catalyst has excellent stability against FDR, and FA can be completely decomposed with a conversion rate of 100%.

[0107] Although the description of the invention has been quite detailed and particularly of several described embodiments, it is not intended to limit it to any of these details or embodiments or any particular embodiment, but should be considered as providing a broad possible interpretation of the claims by referring to the appended claims and taking into account the prior art, thereby effectively covering the intended scope of the invention. Furthermore, the invention has been described above with respect to embodiments foreseeable by the inventors in order to provide a useful description, and non-substantial modifications to the invention that have not yet been foreseen may still represent equivalent modifications.

Claims

1. A method for preparing a PdNi / PCNS-O-NH2 nanocatalyst, characterized in that, Includes the following steps: Step 1: Place porous carbon nanosheets PCNS in HNO3 solution, stir in an oil bath to carry out the reaction, cool, centrifuge, wash until neutral, and dry to obtain PCNS-O; Step 2: Place PCNS-O in anhydrous toluene, then add APTES (3-aminopropyltriethoxysilane), reflux in an oil bath to carry out the reaction, cool after the reaction is complete, centrifuge, wash, and vacuum dry to obtain PCNS-O-NH2; Step 3: Pd precursor salt, Ni precursor salt and NaBH4 are added sequentially to PCNS-O-NH2 and stirred until the reaction is complete to obtain a mixed solution. Then, PdNi / PCNS-O-NH2 nanocatalyst is finally obtained by centrifugation, washing and drying. PCNS is obtained through the following steps: First, SiO2 was dispersed in toluene and ultrasonically stirred. Then, APTES was added, and the mixture was refluxed in an oil bath to carry out the reaction. After the reaction was completed, the mixture was cooled, centrifuged, washed, and vacuum dried to obtain SiO2-NH2. Then, anhydrous glucose and water were added to SiO2-NH2, stirred, and hydrothermally reacted at 180℃ for 12 h. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, washed, and vacuum dried. It was then calcined at 800℃ for 2 h under an Ar atmosphere. After cooling, the SiO2 template agent was removed by etching with 2 M NaOH solution at 70℃ to obtain PCNS. In step 3, the total molar amount of the precursor salts of Pd and Ni is 0.1 mmol. The molar ratio of Pd to Ni is 8:

2.

2. The preparation method according to claim 1, characterized in that, In step 2, the ratio of APTES to NaBH4 in step 3 is 3 mL ~ 12 mL: 30 mg ~ 70 mg.

3. The preparation method according to claim 2, characterized in that, In step 2, the ratio of APTES to NaBH4 in step 3 is 6 mL: 40 mg.

4. A PdNi / PCNS-O-NH2 nanocatalyst, characterized in that, It is prepared by the preparation method described in any one of claims 1-3.

5. The PdNi / PCNS-O-NH2 nanocatalyst according to claim 4, characterized in that, The loading of metallic PdNi in the PdNi / PCNS-O-NH2 nanocatalyst is 5.7 ~ 20 wt%.

6. The PdNi / PCNS-O-NH2 nanocatalyst according to claim 5, characterized in that, The loading of metallic PdNi in the PdNi / PCNS-O-NH2 nanocatalyst is 13.9 wt%.

7. The application of the PdNi / PCNS-O-NH2 nanocatalyst according to any one of claims 4-6 in the preparation of hydrogen source for fuel cells, wherein the PdNi / PCNS-O-NH2 nanocatalyst is used to catalyze the decomposition of formic acid to produce hydrogen.

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