Covalent phosphorus-modified porous nitrogen-carbon sphere-supported noble metal nanoparticles and preparation method and application thereof

Abstract

The present invention relates to catalytic materials, and more particularly to precious metal nanoparticles supported by covalent phosphorus-modified porous nitrogen-carbon balls, and a preparation method and application thereof. In the present invention, polydopamine and a phosphorus source are used as precursors, and phosphorus atoms (P) and phosphorus oxygen groups (PO x ) are covalently doped on the nitrogen-carbon nanosphere carrier. This covalent phosphorus-modified porous nitrogen-carbon sphere can provide abundant loading sites for precious metals, so that the precious metals can evenly form ultrafine nanoparticles on the surface of the nanospheres. Highly dispersed ultrafine precious metal nanoparticles can expose abundant catalytic active sites, thereby improving the electrocatalytic activity.

Description

Technical Field

[0001] The invention relates to catalytic materials, in particular to precious metal nanoparticles supported by covalent phosphorus-modified porous nitrogen-carbon balls, and a preparation method and application thereof. Background Art

[0002] Supported noble metal catalyst is a commonly used catalyst, and its basic structure is to load noble metals (such as platinum, palladium, rhodium, etc.) on a carrier. Supported noble metal catalyst has many advantages, such as high activity, good selectivity, low cost, etc.

[0003] Since precious metals are expensive, loading them on low-cost carriers can effectively reduce the cost of catalysts, so they are widely used in many fields, such as petrochemicals, fuel cells, hydrogen-powered vehicles and other energy fields. In the process of precious metal loading, it is often difficult to achieve uniform dispersion, and clusters or uneven particle structures are easily formed, which may lead to uneven distribution of active sites in the catalytic reaction and affect the overall performance of the catalyst. At the same time, the interaction between the carrier and the precious metal may lead to the deactivation or reduction of the active sites of the precious metals. It is particularly noteworthy that precious metal catalysts may face stability challenges during long-term use, because the precious metals may dissolve into the electrolyte, thereby reducing the performance of the catalyst. Summary of the invention

[0004] Based on this, the present invention provides covalent phosphorus-modified porous nitrogen-carbon sphere-supported noble metal nanoparticles and a preparation method and application thereof, which at least solve one problem in the prior art.

[0005] In a first aspect, the present invention provides a method for preparing noble metal nanoparticles supported by covalent phosphorus-modified porous nitrogen-carbon spheres, which comprises the following steps:

[0006] The polydopamine nanospheres are mixed with a phosphorus source and subjected to heat treatment in an inert gas atmosphere to obtain covalently phosphorus-modified porous nitrogen-carbon spheres (PNC nanospheres);

[0007] Dispersing the covalent phosphorus-modified porous nitrogen-carbon spheres in water, adding a noble metal hydrochloric acid solution, reacting at 50-70° C., and separating solid matter to obtain noble metal nanoparticles supported by the covalent phosphorus-modified porous nitrogen-carbon spheres;

[0008] Wherein, the temperature of the heat treatment is 700-1100°C.

[0009] In a second aspect, the present invention provides covalent phosphorus-modified porous nitrogen-carbon sphere-supported noble metal nanoparticles obtained by the preparation method of the covalent phosphorus-modified porous nitrogen-carbon sphere-supported noble metal nanoparticles.

[0010] In a third aspect, the present invention provides the use of the covalent phosphorus-modified porous nitrogen-carbon sphere-supported noble metal nanoparticles in water electrolysis hydrogen evolution reaction, carbon dioxide reduction reaction, oxygen reduction reaction or organic catalytic reaction.

[0011] In a fourth aspect, the present invention provides an electrode comprising the noble metal nanoparticles supported by the covalent phosphorus-modified porous nitrogen-carbon spheres.

[0012] Due to the adoption of the above technical solution, the embodiments of the present invention have at least the following beneficial effects:

[0013] (1) Using polydopamine and a phosphorus source as precursors, phosphorus atoms (P) and phosphorus oxygen groups (PO x ) are covalently doped on the nitrogen-carbon nanosphere carrier, providing abundant loading sites for the precious metals, so that the precious metals can form ultrafine nanoparticles evenly on the surface of the nanospheres; P heteroatoms and PO x The group-doped carbon optimizes the hydrogen adsorption energy and thus improves the intrinsic activity of the electrocatalyst. It can also stabilize ultrafine noble metal nanoparticles, effectively avoiding noble metal agglomeration, dissolution and catalytic deactivation, balancing the activity and long-term stability of the catalyst, and provides a new idea for the performance optimization of supported composite electrocatalysts.

[0014] (2) Ultrafine noble metals are evenly distributed on the surface of PNC nanospheres, where the average particle size of the noble metals is 1-10 nm and the loading amount is 2-15 wt%; the diameter of the PNC nanospheres is about 0.1-1 µm, the phosphorus content is 1-10 wt%, and the nitrogen content is 1-5 wt%;

[0015] (3) Precious metal nanoparticles supported on covalently phosphorus-modified porous nitrogen-carbon spheres can be prepared in batches with simple operation and good reproducibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a Raman spectrum of PNC nanospheres in an embodiment of the present invention.

[0017] Figure 2 It is the X-ray powder diffraction pattern of the noble metal / PNC in the embodiment of the present invention.

[0018] Figure 3 This is a scanning electron microscope image of the noble metal / PNC in the embodiment of the present invention.

[0019] Figure 4 It is a transmission electron microscope image of the noble metal / PNC in the embodiment of the present invention.

[0020] Figure 5 It is the Raman spectrum of the noble metal / PNC in the embodiment of the present invention.

[0021] Figure 6 1 is a linear sweep voltammetry curve of noble metal / PNC in an embodiment of the present invention.

[0022] Figure 7 It is the Tafel plot of precious metal / PNC in the embodiment of the present invention.

[0023] Figure 8 This is a graph showing the IT stability test results of precious metal / PNC in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The following is a clear and complete description of the concept of the present invention and the technical effects produced, so as to fully explain the purpose, scheme and effect of the present invention.

[0025] In order to balance the activity and long-term stability of supported noble metal catalysts and improve catalytic performance, the present invention provides covalent phosphorus-modified porous nitrogen-carbon sphere-supported noble metal nanoparticles, and a preparation method and application thereof.

[0026] In a first aspect, the present invention provides a method for preparing noble metal nanoparticles supported by covalent phosphorus-modified porous nitrogen-carbon spheres, which comprises the following steps:

[0027] The polydopamine nanospheres are mixed with a phosphorus source and subjected to heat treatment in an inert gas atmosphere to obtain covalently phosphorus-modified porous nitrogen-carbon spheres (PNC nanospheres);

[0028] Dispersing the covalent phosphorus-modified porous nitrogen-carbon spheres in water, adding a noble metal hydrochloric acid solution, reacting at 50-70° C., and separating solid matter to obtain noble metal nanoparticles supported by the covalent phosphorus-modified porous nitrogen-carbon spheres;

[0029] Wherein, the temperature of the heat treatment is 700-1100°C.

[0030] Using polydopamine and a phosphorus source as precursors, phosphorus atoms (P) and phosphorus oxygen groups (PO x ) are covalently doped on the nitrogen-carbon nanosphere carrier. This covalent phosphorus-modified porous nitrogen-carbon sphere can provide abundant loading sites for precious metals, so that the precious metals can form ultrafine nanoparticles uniformly on the surface of the nanospheres. Highly dispersed ultrafine precious metal nanoparticles can expose abundant catalytic active sites, thereby improving the electrocatalytic activity. P heteroatom and PO x Group-doped carbon can not only optimize hydrogen adsorption energy and thus improve the intrinsic activity of electrocatalysts, but also stabilize ultrafine precious metal nanoparticles. Therefore, this method can effectively balance the activity and long-term stability of the catalyst by rationally regulating the structure of the catalyst carrier, providing a new idea for the performance optimization of supported composite catalysts and has commercial prospects.

[0031] In some optional embodiments, the phosphorus source is at least one of diammonium hydrogen phosphate, diammonium hydrogen phosphite, ammonium dihydrogen phosphate, ammonium phosphate, phosphoric acid, diphenyl phosphate, and ammonium polyphosphate. Preferably, the phosphorus source is diammonium hydrogen phosphate.

[0032] In some optional embodiments, the noble metal salt acidic solution is formed by dissolving a noble metal salt in an acidic solution, wherein the noble metal salt is at least one of acetate, nitrate, sulfate and chloride of gold, silver, palladium, platinum, iridium, osmium, rhodium and ruthenium, and the acidic solution is at least one of acetic acid solution, nitric acid solution, sulfuric acid solution and hydrochloric acid solution. The acidic solution plays a role in dissolving the noble metal salt, and it is preferably a dilute acid solution, for example, the concentration can be 0.5 M. Preferably, the noble metal salt is palladium chloride, platinum chloride or rhodium chloride.

[0033] In some optional embodiments, the temperature of the heat treatment is 900°C.

[0034] In some optional embodiments, the heat treatment time is 0.1-6 h.

[0035] In some optional embodiments, the inert gas is argon or nitrogen.

[0036] In some optional embodiments, the polydopamine nanospheres are obtained by polymerizing dopamine hydrochloride in a mixed solution of water, anhydrous ethanol and aqueous ammonia.

[0037] In some optional embodiments, before the heat treatment, the step of grinding the polydopamine nanospheres and the phosphorus source is further included. By grinding, the polydopamine nanospheres and the phosphorus source can be mixed more evenly.

[0038] In a second aspect, the present invention provides covalent phosphorus-modified porous nitrogen-carbon sphere-supported noble metal nanoparticles obtained by the preparation method of the covalent phosphorus-modified porous nitrogen-carbon sphere-supported noble metal nanoparticles.

[0039] In a third aspect, the present invention provides the use of the covalent phosphorus-modified porous nitrogen-carbon sphere-supported noble metal nanoparticles in a water electrolysis hydrogen evolution reaction, a carbon dioxide reduction reaction, an oxygen reduction reaction, or an organic catalytic reaction. For example, the covalent phosphorus-modified porous nitrogen-carbon sphere-supported noble metal nanoparticles are used as catalysts for a water electrolysis hydrogen evolution reaction.

[0040] In a fourth aspect, the present invention provides an electrode comprising the noble metal nanoparticles supported by the covalent phosphorus-modified porous nitrogen-carbon spheres.

[0041] In some optional embodiments, the noble metal nanoparticles supported by the covalent phosphorus-modified porous nitrogen-carbon spheres are loaded on a glassy carbon electrode to form an electrode with electrocatalytic properties.

[0042] Some typical embodiments are described below.

[0043] In the following examples, the preparation method of polydopamine (PDA) nanospheres is as follows: 90 mL of deionized water is added with 40 mL of anhydrous ethanol and 2 mL of aqueous ammonia, and stirred for 30 min until uniform; 100 mL of the above solution is added with 500 mg of dopamine hydrochloride, and stirred for reaction at room temperature for 24 h to polymerize to form PDA nanospheres; the solid is filtered and washed with a microporous filter membrane to obtain a black solid, which is dried in an oven at 60°C overnight and ground to obtain a black PDA nanosphere powder.

[0044] Example 1

[0045] Take 100 mg of dried PDA nanospheres, add 200 mg of diammonium hydrogen phosphate, and grind in a mortar for 30 min to obtain a uniform powder; then, in a vacuum tube furnace, in a N2 (15 mL / min) atmosphere, increase the temperature to 1100°C at a rate of 2°C / min, and carbonize at 1100°C for 0.1 h; then, add 100 mL of 1 M HCl solution and stir and wash for 12 h, filter and wash, and dry in an oven at 60°C overnight to obtain PNC nanospheres (PNC-1100).

[0046] Example 2

[0047] 100 mg of dried PDA nanospheres and 200 mg of diammonium phosphate were ground in a mortar for 30 min to obtain a uniform powder. Then, the temperature was raised to 1000°C at a rate of 2°C / min in a vacuum tube furnace under a N2 (15 mL / min) atmosphere, and carbonized at 1000°C for 1 h. Next, 100 mL of 1 M HCl solution was added and stirred for washing for 12 h, filtered and washed, and dried in an oven at 60°C overnight to obtain PNC nanospheres (PNC-1000).

[0048] Example 3

[0049] 100 mg of dried PDA nanospheres and 300 mg of ammonium phosphate were ground in a mortar for 30 min to obtain a uniform powder. Then, the temperature was raised to 900 °C at a rate of 2 °C / min in a vacuum tube furnace under a N2 (15 mL / min) atmosphere, and carbonization was performed at 900 °C for 3 h. Next, 100 mL of 1 M HCl solution was added and stirred for washing for 12 h, filtered and washed, and dried in an oven at 60 °C overnight to obtain PNC nanospheres (PNC-900).

[0050] Example 4

[0051] 100 mg of dried PDA nanospheres and 400 mg of diphenyl phosphate were ground in a mortar for 30 min to obtain a uniform powder; then, in a vacuum tube furnace, the temperature was raised to 800°C at a rate of 2°C / min under a N2 (15 mL / min) atmosphere, and carbonized at 800°C for 3 h; then, 100 mL of 1 M HCl solution was added and stirred for washing for 12 h, filtered and washed, and dried in an oven at 60°C overnight to obtain PNC nanospheres (PNC-800).

[0052] Example 5

[0053] 200 mg of dried PDA nanospheres and 400 mg of ammonium polyphosphate were ground in a mortar for 30 min to obtain a uniform powder; then, the temperature was raised to 700 °C at a rate of 2 °C / min in a vacuum tube furnace under a N2 (15 mL / min) atmosphere, and carbonized at 700 °C for 6 h; then, 200 mL of 1 M HCl solution was added and stirred for washing for 12 h, filtered and washed, and dried in an oven at 60 °C overnight to obtain PNC nanospheres (PNC-700).

[0054] Example 6

[0055] Take 25 mg of the PNC nanospheres (PNC-900) obtained in Example 3 above, add 6 mL of deionized water and ultrasonically disperse them into a uniform ink-like solution; finally, add 250 μL of palladium chloride acid solution (10 mg / mL, 0.5 M HCl as solvent), stir and react at 60°C for 16 h, wash by centrifugation with deionized water and ethanol, and dry in an oven at 60°C overnight to obtain covalent phosphorus-modified porous nitrogen-carbon sphere-supported precious metal nanoparticles (labeled as Pd / PNC).

[0056] Example 7

[0057] Take 25 mg of the PNC nanospheres (PNC-900) obtained in Example 3 above, add 6 mL of deionized water and ultrasonically disperse them into a uniform ink-like solution; finally, add 250 μL of platinum chloride acid solution (10 mg / mL, 0.5 M HCl as solvent), stir and react at 60°C for 16 h, wash by centrifugation with deionized water and ethanol, and dry in an oven at 60°C overnight to obtain covalent phosphorus-modified porous nitrogen-carbon sphere-supported precious metal nanoparticles (labeled as Pt / PNC).

[0058] Example 8

[0059] Take 25 mg of the PNC nanospheres (PNC-900) obtained in Example 3 above, add 6 mL of deionized water and ultrasonically disperse them into a uniform ink-like solution; finally, add 250 μL of rhodium chloride acidic solution (10 mg / mL, 0.5 M HCl as solvent), stir and react at 60°C for 16 h, wash by centrifugation with deionized water and ethanol, and dry in an oven at 60°C overnight to obtain covalent phosphorus-modified porous nitrogen-carbon sphere-supported precious metal nanoparticles (labeled as Rh / PNC).

[0060] The PNC nanospheres prepared under different conditions were subjected to Raman testing, and the spectra are shown in Figure 1 .

[0061] PNC nanospheres (PNC-900), Pd / PNC, Pt / PNC and Rh / PNC were analyzed and tested respectively, and the X-ray diffraction patterns are shown in Figure 2 ; Scanning electron microscopy images are shown in Figure 3 Transmission electron microscopy images are shown in Figure 4 ; Raman spectrum see Figure 5 .

[0062] The electrocatalytic HER performance of Pd / PNC, Pt / PNC and Rh / PNC in Examples 6-8 was tested on a CHI760E electrochemical workstation, and commercial 20% Pt / C (brand: Innochem, catalog number: A07498) was used as a control. Before the electrochemical test, N2 was passed for 30 min to remove the air dissolved in the 0.5 M H2SO4 electrolyte; the catalysts (commercial 20% Pt / C, Pd / PNC, Pt / PNC and Rh / PNC) were loaded on glassy carbon electrodes (GCE, diameter 5 mm, geometric area 0.196 cm 2 ) was prepared as the working electrode, a carbon rod was used as the counter electrode, and Ag / AgCl was used as the reference electrode (0.220 V).

[0063] Figure 6 The linear sweep voltammetry curve shown was obtained at a scan rate of 10 mV / s. Figure 6 It is known that noble metal / PNC (Pd / PNC, Pt / PNC and Rh / PNC) drive 10 mA cm -2 The overpotentials required for the current density are 25 mV, 8 mV, and 27 mV, respectively, which are better than the overpotential of commercial 20% Pt / C (36 mV). Figure 7 The Tafel curve shown is from Figure 6 The Tafel slope of the precious metal / PNC (Pd / PNC, Pt / PNC and Rh / PNC) is 34 mV·dec. -1 、25 mV·dec-1 and 38mV·dec -1 , and have basically reached the Tafel slope of commercial 20% Pt / C (30 mV·dec -1 ).

[0064] The long-term stability test of Pd / PNC in Example 6 was carried out by chronopotentiometry. The results are as follows: Figure 8 The it electrolysis test of Pd / PNC in 0.5 M H2SO4 electrolyte shows that the current density hardly changes within 110 h, which indicates that the catalyst Pd / PNC has excellent stability.

[0065] The above is only a preferred embodiment of the present invention. The present invention is not limited to the above implementation. As long as the technical effect of the present invention is achieved by the same or equivalent means, it should belong to the protection scope of the present invention. Within the protection scope of the present invention, its technical scheme and / or implementation method can have various modifications and changes.

Claims

1. A method for preparing noble metal nanoparticles supported by covalent phosphorus-modified porous nitrogen-carbon balls, characterized in that: The following steps are involved: The polydopamine nanospheres are mixed with a phosphorus source and subjected to heat treatment in an inert gas atmosphere to obtain covalent phosphorus-modified porous nitrogen-carbon spheres; Dispersing the covalent phosphorus-modified porous nitrogen-carbon spheres in water, adding a noble metal hydrochloric acid solution, reacting at 50-70° C., and separating solid matter to obtain noble metal nanoparticles supported by the covalent phosphorus-modified porous nitrogen-carbon spheres; The heat treatment temperature is 700-1100°C; the noble metal nanoparticles are evenly distributed on the surface of the covalent phosphorus-modified porous nitrogen-carbon spheres, wherein the average particle size of the noble metal nanoparticles is 1-10 nm and the loading amount is 2-15wt%; the diameter of the covalent phosphorus-modified porous nitrogen-carbon spheres is 0.1-1 µm, the phosphorus content is 1-10 wt%, and the nitrogen content is 1-5wt%; The phosphorus source is at least one of diammonium hydrogen phosphate, diammonium hydrogen phosphite, ammonium dihydrogen phosphate, ammonium phosphate, phosphoric acid, diphenyl phosphate, and ammonium polyphosphate; The noble metal salt acidic solution is formed by dissolving a noble metal salt in an acidic solution, wherein the noble metal salt is at least one of acetates, nitrates, sulfates and chlorides of gold, silver, palladium, platinum, iridium, osmium, rhodium and ruthenium, and the acidic solution is at least one of acetic acid solution, nitric acid solution, sulfuric acid solution and hydrochloric acid solution.

2. The method according to claim 1, characterized in that The phosphorus source is diammonium hydrogen phosphate.

3. The method according to claim 2, characterized in that The noble metal salt is palladium chloride, platinum chloride or rhodium chloride.

4. The method according to claim 1, characterized in that The heat treatment time is 0.1-6 h.

5. The method according to claim 1, characterized in that Before the heat treatment, the method further comprises the step of grinding the polydopamine nanospheres and the phosphorus source.

6. Precious metal nanoparticles supported by covalent phosphorus-modified porous nitrogen-carbon spheres obtained according to the method of any one of claims 1 to 5.

7. Use of the covalent phosphorus-modified porous nitrogen-carbon sphere-supported noble metal nanoparticles according to claim 6 in water electrolysis hydrogen evolution reaction, carbon dioxide reduction reaction, oxygen reduction reaction or organic catalytic reaction.

8. An electrode, characterized in that: It comprises the noble metal nanoparticles supported by the covalent phosphorus-modified porous nitrogen-carbon spheres according to claim 6.

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