CN110627030A - A platinum phosphide nanocatalyst, its preparation method and its application in electrocatalytic oxygen reduction - Google Patents

Abstract

The invention provides a platinum phosphide nano-catalyst and its preparation method and application in electrocatalytic oxygen reduction, comprising the following steps: 1) dispersing the platinum catalyst in a solvent and stirring evenly to obtain a platinum catalyst dispersion; A phosphorus source is added to the platinum catalyst dispersion liquid, mixed evenly, reacted at a certain temperature, centrifuged and washed to obtain a platinum phosphide nanometer catalyst after the reaction is completed. In the method of the invention, phosphorus atoms produced by the decomposition of phosphorus sources are diffused into platinum catalysts at a certain temperature to synthesize platinum phosphide nano catalysts with specific electronic structures. The preparation method has the advantages of simple process, low cost, good repeatability, no environmental pollution, and convenient mass production, and the prepared platinum phosphide nano-catalyst shows much higher performance in the electrocatalytic oxygen reduction reaction than commercial platinum/carbon The catalytic activity and stability of the catalyst have good application prospects.

Description

A platinum phosphide nano-catalyst and its preparation method and its use in electrocatalytic oxygen reduction application

technical field

The invention belongs to the field of nanometer science, and in particular relates to a platinum phosphide nanometer catalyst, its preparation method and its application in electrocatalytic oxygen reduction.

Background technique

Platinum catalysts have shown excellent catalytic performance in the fields of energy, chemistry and petrochemical industry, especially in fuel cells, automobile exhaust purification, hydrogenation, dehydrogenation and other industrial catalytic reactions. However, platinum resources are scarce and concentrated in a few countries and regions, making it expensive and extremely expensive to use, which seriously hinders its large-scale application in modern industry. Therefore, improving the catalytic performance of platinum catalysts and reducing the amount of platinum has become a major research hotspot in energy science, which is of great significance for promoting economic development and saving resources.

Alloying platinum by introducing second-phase transition metals (such as palladium, gold, cobalt, nickel, copper, iron, lead, etc.) is an effective strategy to enhance the performance of platinum catalysts. It mainly improves the catalytic activity of platinum and reduces the amount of platinum by changing the electronic structure of platinum (5d empty orbital) to increase the number of active sites on the surface of platinum or changing the binding energy between platinum and reactants, reactant intermediates and products. . However, the second-phase transition metal component in the catalyst is prone to corrosion, dissolution and Ostwald aging process under conditions such as low pH, high oxygen concentration, high humidity, and different potentials (Nano Energy 2019, 60, 111-118), resulting in The activity is impaired and the lifespan is shortened, hindering the process of its commercial scale application. In addition, the alloying technology of platinum is also limited by its complex preparation method and the use of expensive transition metals (such as gold and silver), making it unfeasible to develop in industry.

Recent research results have shown that the addition of non-metallic atoms (such as H, B, N, C, or P) to metal catalysts can change the electronic structure of platinum catalysts compared to the modification of platinum catalysts by adding second-phase metal elements. Greater impact (Nat.Comm.2014, 5, 5787, J.Mater.Chem.A 2019, 7, 4714.), and thus better catalytic performance. However, due to the strong binding energy between platinum atoms and the large bond energy (306.7kJ/mol) (CRC press, 2007), non-metal atoms are doped into the platinum lattice to form PtX (X=H, B, N, C or P, etc.) remains a great challenge.

In recent years, transition metal phosphides (such as nickel phosphide, cobalt phosphide, iron phosphide, rhodium phosphide, ruthenium phosphide, etc.) have low raw material costs (avoiding the use of second-phase transition metals), various preparation methods, Due to the advantages of high catalytic activity and stability, it is widely used in the research of electrocatalysis, energy storage, photocatalysis and chemical catalysis. It has been reported that cobalt phosphide nanocatalysts oxidized on porous surfaces have good electrocatalytic oxygen reduction performance (J. It shows high catalytic activity and stability (J.Am.Chem.Soc., 2017, 139, 5494-5502). Adding a phosphorus source to the palladium catalyst can quickly modify its surface to improve its selectivity in the catalytic reaction of carbon monoxide (patent CN107413359A), but the prepared catalyst is palladium-palladium phosphide with a core-shell structure, and wherein Palladium phosphide is amorphous, and this structure cannot be stably maintained in catalytic reactions. In addition, although there have been a lot of research on metal phosphides, due to the limitations of difficult synthesis of platinum phosphide nanocrystals, harsh production conditions, complex preparation and few controllable factors, there are few research reports on platinum phosphide nanocatalysts. . For example, N. Klemmlikova et al. generate a PtP surface layer _on the platinum catalyst core and apply it to a fuel cell (patent CN102365775B). However, the prepared catalyst can only be synthesized on a carrier material, which is not versatile, and requires conditions such as vacuum and high-temperature calcination, and the process cost is high, which is not conducive to large-scale industrial production. Therefore, developing a low-cost and efficient route to obtain platinum phosphide nanocatalysts with excellent catalytic activity and stability is of great significance but also a great challenge.

Contents of the invention

Aiming at the problems existing in the prior art, the present invention provides a platinum phosphide nanocatalyst and its preparation method and its application in electrocatalytic oxygen reduction. The prepared platinum phosphide nanocatalyst is applied in electrocatalytic oxygen reduction reaction, showing excellent catalytic activity and stability.

The present invention is achieved through the following technical solutions:

A preparation method of platinum phosphide nano catalyst, comprising the steps of:

Step 1, dispersing the platinum catalyst in a solvent to obtain a platinum catalyst dispersion;

Step 2, adding a phosphorus source to the platinum catalyst dispersion in step 1, stirring evenly, reacting at 200-360° C. for 1-20 hours, centrifuging and washing after the reaction to obtain a platinum phosphide nano-catalyst.

Preferably, in step 1, the platinum catalyst is platinum nanocrystal, platinum-based alloy or supported platinum-based catalyst.

Further, the particle size of platinum nanocrystals is 2-8nm.

Further, the platinum-based alloy is an alloy of platinum-cobalt, platinum-nickel, platinum-iron, platinum-copper, platinum-gold, platinum-palladium, platinum-cobalt-nickel, platinum-rhodium-palladium or platinum-iron-manganese.

Further, the supported platinum-based catalyst is commercial platinum/carbon, platinum/alumina, platinum/silicon dioxide, platinum/titania or platinum-supported molecular sieves.

Preferably, in step 1, the solvent is oleylamine, oleic acid, 1-octadecene, glycerol, formamide, quinoline, 1-chlorinated naphthalene, sulfolane, diphenyl ether or diphenyl sulfone.

Preferably, in step 2, the phosphorus source is white phosphorus, red phosphorus, phosphine, phosphate, phosphite, hypophosphite, tri-n-octylphosphine, tri-n-octylphosphine oxide or triphenylphosphine.

Preferably, in step 1, the concentration of platinum in the platinum catalyst dispersion is 0.01-10 mg/mL; the concentration of phosphorus in the phosphorus source used in step 2 is lower than the concentration of platinum in the platinum catalyst.

The platinum phosphide nanometer catalyst prepared by the preparation method.

The application of the platinum phosphide nano catalyst in electrocatalytic oxygen reduction.

Compared with the prior art, the present invention has the following beneficial technical effects:

In the present invention, the phosphorus atoms produced by the decomposition of the phosphorus source diffuse into the platinum catalyst lattice, and the pure-phase platinum phosphide (molecular formula is Pt ₂ P) nanocrystalline catalyst is prepared, and its specific electronic structure makes the catalyst intermediate to the oxygen reduction reaction. The binding energy of the body is weakened, showing excellent electrocatalytic oxygen reduction reaction activity. At the same time, because the surface is rich in stacking fault defects, it has a large number of dangling bonds and abundant platinum reactive active sites, which further improves the electrocatalytic performance. More importantly, the platinum phosphide nanocatalyst has a good crystal structure (face-centered cubic structure) and is a pure phase, which makes the catalyst have better structural stability than other amorphous structures or heterogeneous catalysts. The electrocatalytic reaction exhibits excellent catalytic stability, which avoids a significant drop in catalyst activity during the catalytic process, and has great application potential in the field of electrocatalysis.

In addition, the invention avoids the use of transition metals in conventional platinum-based alloy catalysts, greatly reduces the manufacturing cost of the catalyst, and further meets the requirements of industrial mass production. Compared with the existing platinum-based catalyst, the preparation method provided by the invention is simple, the raw material is cheap, the production cost is low, and there is no environmental pollution.

Further, the components of the catalyst can be regulated by the reaction time, and the size of the catalyst can be precisely controlled by regulating the size of the original platinum catalyst.

The platinum phosphide nano-catalyst prepared by the present invention is applied in the electrocatalytic oxygen reduction reaction, because of its specific electronic structure, rich defects on the surface, stable structure in the reaction, good dispersion and other characteristics, it shows excellent catalytic activity And stability, can adapt to the needs of higher industrial applications.

Description of drawings

FIG. 1 is a transmission electron micrograph of the platinum phosphide nanocatalyst prepared in Example 1 of the present invention, and the inset in the figure is an enlarged photo of a single nanoparticle.

Fig. 2 is a transmission electron micrograph of the platinum phosphide nanocatalyst prepared in Example 2 of the present invention, and the inset in the figure is an enlarged photo of a single nanoparticle.

Fig. 3 is a transmission electron micrograph of the platinum phosphide nanocatalyst prepared in Example 3 of the present invention, and the inset in the figure is an enlarged photo of a single nanoparticle.

Fig. 4 is a transmission electron micrograph of the platinum phosphide nanocatalyst prepared in Example 4 of the present invention, and the inset in the figure is an enlarged photo of a single nanoparticle.

Fig. 5 is a transmission electron micrograph of the platinum phosphide nanocatalyst prepared in Example 5 of the present invention, and the inset in the figure is an enlarged photo of a single nanoparticle.

Fig. 6 is a high-resolution transmission electron micrograph of the platinum phosphide nanocatalyst prepared in Example 5 of the present invention, and the inset in the figure is its corresponding Fourier transform image.

Fig. 7 is the X-ray diffraction spectrum of the platinum phosphide nanocatalyst prepared in Example 5 of the present invention.

Fig. 8 is a transmission electron micrograph of the platinum phosphide nanocatalyst prepared in Example 6 of the present invention.

Fig. 9 is a comparison chart of the X-ray diffraction spectra of the platinum phosphide nanocatalyst prepared in Example 6 of the present invention and its raw material platinum nanoparticles.

Fig. 10 is a transmission electron micrograph of the platinum phosphide nanocatalyst loaded on commercial carbon black prepared in Example 6 of the present invention.

Fig. 11 is a comparison chart of the electrocatalytic oxygen reduction reaction activity between the platinum phosphide nanocatalyst prepared in Example 6 of the present invention and the commercial platinum/carbon catalyst.

Fig. 12 is a comparison chart of electrocatalytic oxygen reduction reaction stability between the platinum phosphide nanocatalyst prepared in Example 6 of the present invention and the commercial platinum/carbon catalyst.

Detailed ways

The present invention will be further described in detail below in conjunction with specific embodiments, which are explanations of the present invention rather than limitations.

The preparation method of platinum phosphide nano-catalyst comprises the following steps:

Step 1, dispersing the platinum catalyst in a solvent to obtain a platinum catalyst dispersion;

Step 2, adding a phosphorus source to the platinum catalyst dispersion in step 1, stirring evenly, heating and reacting, centrifuging and washing after the reaction to obtain a platinum phosphide nano-catalyst.

In step 1, the platinum catalyst is platinum nanocrystal, platinum-based alloy or supported platinum-based catalyst. Platinum-based alloys are platinum-based binary alloys such as platinum-cobalt, platinum-nickel, platinum-iron, platinum-copper, platinum, and platinum-palladium, platinum-based ternary alloys such as platinum-cobalt-nickel, platinum-rhodium-palladium, and platinum-iron-manganese, and platinum-based multiple alloys Wait. Supported platinum-based catalysts are commercial platinum/carbon, platinum/alumina, platinum/silica, platinum/titania or platinum-supported molecular sieves.

In step 1, the solvent is oleylamine, oleic acid, 1-octadecene, glycerol, formamide, quinoline, 1-chlorinated naphthalene, sulfolane, diphenyl ether or diphenyl sulfone.

In step 2, the phosphorus source used is the simple substance of phosphorus element and the compound of various valence states (white phosphorus, red phosphorus, phosphine, phosphate, the inorganic matter of phosphorus such as phosphite, hypophosphite, and trin-octyl Phosphine, tri-n-octylphosphine oxide, triphenylphosphine and other organophosphorus reagents).

In step 1, the concentration of platinum in the platinum catalyst dispersion is 0.01-10 mg/mL; the concentration of phosphorus in the phosphorus source used in step 2 is lower than the concentration of platinum in the platinum catalyst.

In step 2, the reaction temperature is 200-360°C, and the reaction time is 1-20h.

Embodiment one

The preparation method of platinum phosphide nano-catalyst of the present invention comprises the following steps:

1) Ultrasonic dispersion of 3.76 mg of platinum nanocubes (average particle size of 8 nm) in 10 mL of oleylamine to obtain a stable platinum catalyst dispersion, wherein the concentration of platinum is 0.376 mg/mL;

2) Add 1.6 mL of tri-n-octylphosphine to the platinum catalyst dispersion in step 1), and stir evenly to obtain a reaction precursor;

3) Heating and stirring the reaction precursor solution at 300° C., centrifuging and washing after reacting for 1 hour to obtain a platinum phosphide nano-catalyst. The content of phosphorus atoms in the catalyst is 4%, the morphology remains as nano-cubes, and the size does not change significantly.

Embodiment two

The preparation method of platinum phosphide nano-catalyst of the present invention comprises the following steps:

1) Ultrasonic dispersion of 3.76 mg of platinum nanocubes (average particle size of 8 nm) in 10 mL of oleylamine to obtain a stable platinum catalyst dispersion, wherein the concentration of platinum is 0.376 mg/mL;

2) Add 1.6 mL of tri-n-octylphosphine to the platinum catalyst dispersion in step 1), and stir evenly to obtain a reaction precursor;

3) heating and stirring the reaction precursor solution at 300° C., centrifuging and washing after reacting for 1.5 hours to obtain a platinum phosphide nano-catalyst. The content of phosphorus atoms in the catalyst is 10%, and the shape gradually changes to a cube with cut corners.

Embodiment Three

The preparation method of platinum phosphide nano-catalyst of the present invention comprises the following steps:

1) Ultrasonic dispersion of 3.76 mg of platinum nanocubes (average particle size of 8 nm) in 10 mL of oleylamine to obtain a stable platinum catalyst dispersion, wherein the concentration of platinum is 0.376 mg/mL;

2) Add 1.6 mL of tri-n-octylphosphine to the platinum catalyst dispersion in step 1), and stir evenly to obtain a reaction precursor;

3) heating and stirring the reaction precursor solution at 300° C., centrifuging and washing after reacting for 2 hours to obtain a platinum phosphide nano-catalyst. The content of phosphorus atoms in the catalyst is 16%, the catalyst particles become round gradually, and the corners gradually disappear.

Embodiment four

The preparation method of platinum phosphide nano-catalyst of the present invention comprises the following steps:

1) Ultrasonic dispersion of 3.76 mg of platinum nanocubes (average particle size of 8 nm) in 10 mL of oleylamine to obtain a stable platinum catalyst dispersion, wherein the concentration of platinum is 0.376 mg/mL;

2) Add 1.6 mL of tri-n-octylphosphine to the platinum catalyst dispersion in step 1), and stir evenly to obtain a reaction precursor;

3) heating and stirring the reaction precursor solution at 300° C., centrifuging and washing after reacting for 2.5 hours to obtain a platinum phosphide nano-catalyst. The content of phosphorus atoms in the catalyst is 21%, the morphology of the catalyst becomes nearly spherical, and the size does not change significantly.

Embodiment five

The preparation method of platinum phosphide nano-catalyst of the present invention comprises the following steps:

1) Ultrasonic dispersion of 3.76 mg of platinum nanocubes (average particle size of 8 nm) in 10 mL of oleylamine to obtain a stable platinum catalyst dispersion, wherein the concentration of platinum is 0.376 mg/mL;

2) Add 1.6 mL of tri-n-octylphosphine to the platinum catalyst dispersion in step 1), and stir evenly to obtain a reaction precursor;

3) Heating and stirring the reaction precursor solution at 300° C., centrifuging and washing after reacting for 3 hours to obtain a platinum phosphide nano-catalyst. The phosphorus atom content in the catalyst is 33.3%, the particle morphology further becomes spherical, and the particle size increases to 9.5nm.

Embodiment six

The preparation method of platinum phosphide nano-catalyst of the present invention comprises the following steps:

1) ultrasonically disperse 3.76 mg of platinum nanoparticles (average particle size is 5 nm) in 10 mL of oleylamine to obtain a stable platinum catalyst dispersion, wherein the concentration of platinum is 0.376 mg/mL;

2) Add 1.6 mL of tri-n-octylphosphine to the platinum catalyst dispersion in step 1), and stir evenly to obtain a reaction precursor;

3) Heating and stirring the reaction precursor solution at 300° C., centrifuging and washing after reacting for 3 hours to obtain a platinum phosphide nano-catalyst. The phosphorus atom content in the catalyst is 33.3%, the particle shape is quasi-spherical, and the particle size is 6.2nm.

Embodiment seven

The preparation method of platinum phosphide nano-catalyst of the present invention comprises the following steps:

1) Ultrasonic dispersion of 3.76 mg of platinum nanoparticles (average particle size of 2 nm) in 10 mL of oleylamine to obtain a stable platinum catalyst dispersion, wherein the concentration of platinum is 0.376 mg/mL;

2) Add 1.6 mL of tri-n-octylphosphine to the platinum catalyst dispersion in step 1), and stir evenly to obtain a reaction precursor;

3) heating and stirring the reaction precursor solution at 300° C., centrifuging and washing after reacting for 1.5 hours to obtain a platinum phosphide nano-catalyst. The phosphorus atom content in the catalyst is 33.3%, the particle shape is quasi-spherical, and the particle size is 2.5nm.

Embodiment eight

The preparation method of platinum phosphide nano-catalyst of the present invention comprises the following steps:

1) Ultrasonic dispersion of 3.71 mg of platinum-nickel alloy (composed of PtNi ₃ ) nanocatalyst in 10 mL of oleylamine was obtained to obtain a stable platinum-nickel alloy nanocatalyst dispersion. The concentration of platinum atoms is 0.195mg/mL;

2) Add 3 mL of tri-n-octylphosphine to the platinum-nickel alloy catalyst dispersion in step 1), and stir evenly to obtain a reaction precursor;

3) heating and stirring the reaction precursor solution at 200° C., centrifuging and washing after reacting for 20 hours to obtain a platinum-nickel-phosphorus alloy nanocatalyst.

Embodiment nine

The preparation method of platinum phosphide nano-catalyst of the present invention comprises the following steps:

1) Ultrasonic dispersion of 5 mg of platinum alloy (composed as Pt ₅₀ Au ₅₀ ) nanocatalyst in 10 mL of oleic acid to obtain a stable platinum alloy nanocatalyst dispersion. The concentration of platinum atoms is 0.249mg/mL;

2) Add 5.4 mL of tri-n-octylphosphine to the platinum alloy catalyst dispersion in step 1), and stir evenly to obtain a reaction precursor;

3) Heating and stirring the reaction precursor solution at 290° C., centrifuging and washing after reacting for 8.5 hours to obtain a platinum-phosphorus alloy nanocatalyst.

Embodiment ten

The preparation method of platinum phosphide nano-catalyst of the present invention comprises the following steps:

1) Ultrasonic dispersion of 17 mg of platinum-rhodium-palladium alloy (composed as Pt ₄₇ Rh ₃₃ Pd ₂₀ ) nanocatalyst in 10 mL of 1-octadecene to obtain a stable platinum-rhodium-palladium alloy nanocatalyst dispersion. The concentration of platinum atoms is 1.06mg/mL;

2) Add 5 mL of tri-n-octylphosphine to the platinum-rhodium-palladium alloy catalyst dispersion in step 1), and stir to obtain a reaction precursor;

3) heating and stirring the reaction precursor solution at 280° C., centrifuging and washing after reacting for 3.5 hours to obtain a platinum-rhodium-palladium alloy nano-catalyst.

Embodiment Eleven

The preparation method of platinum phosphide nano-catalyst of the present invention comprises the following steps:

1) Ultrasonic dispersion of 50 mg of commercial platinum/carbon catalyst (10% loading) in 10 mL of 1-octadecene to obtain a stable platinum/carbon catalyst dispersion. The concentration of platinum atoms is 0.5mg/mL;

2) Add 2 mL of tri-n-octylphosphine to the platinum/carbon catalyst dispersion in step 1), and stir evenly to obtain a reaction precursor;

3) heating and stirring the reaction precursor solution at 250° C., centrifuging and washing after reacting for 6 hours to obtain a platinum phosphide/carbon nano catalyst.

Embodiment 12

The preparation method of platinum phosphide nano-catalyst of the present invention comprises the following steps:

1) Ultrasonic dispersion of 100 mg of commercial platinum/silica catalyst (5% loading) in 10 mL of 1-octadecene to obtain a stable platinum/silica catalyst dispersion. The concentration of platinum atoms is 0.5mg/mL;

2) Add 2 mL of tri-n-octylphosphine to the platinum/silicon dioxide catalyst dispersion in step 1), and stir evenly to obtain a reaction precursor;

3) Heating and stirring the reaction precursor solution at 260° C., centrifuging and washing after reacting for 5 hours to obtain a platinum phosphide/silicon dioxide nano-catalyst.

Embodiment Thirteen

The preparation method of platinum phosphide nano-catalyst of the present invention comprises the following steps:

1) Ultrasonic dispersion of 10 mg of platinum-supported molecular sieve catalyst (1% loading) in 10 mL of oleylamine to obtain a stable platinum-supported molecular sieve catalyst dispersion. The concentration of platinum atoms is 0.01mg/mL;

2) Add 5 mL of tri-n-octylphosphine to the platinum-loaded molecular sieve catalyst dispersion in step 1), and stir evenly to obtain a reaction precursor;

3) Heating and stirring the reaction precursor solution at 320° C., centrifuging and washing after reacting for 10 hours to obtain a platinum-supported phosphide molecular sieve nano-catalyst.

Embodiment Fourteen

The preparation method of platinum phosphide nano-catalyst of the present invention comprises the following steps:

1) uniformly mix 10 mg of platinum nanoparticles (average particle size is 5 nm) with 20 mg of diphenyl sulfone;

2) Add 6 mg of white phosphorus elemental substance (dissolved in carbon disulfide) to step 1) and stir evenly to obtain a reaction precursor;

3) heating and stirring the reaction precursor at 360° C., centrifuging and washing after reacting for 4 hours to obtain a platinum phosphide nano-catalyst.

Embodiment 15

The preparation method of platinum phosphide nano-catalyst of the present invention comprises the following steps:

1) Ultrasonic dispersion of 100 mg of platinum nanoparticles (with an average particle size of 5 nm) in 10 mL of glycerol to obtain a stable platinum catalyst dispersion. The concentration of platinum atoms is 10 mg/mL;

2) Add 72 mg of sodium hypophosphite to the platinum catalyst dispersion in step 1), and stir evenly to obtain a reaction precursor;

3) heating and stirring the reaction precursor solution at 260° C., centrifuging and washing after reacting for 8.5 hours to obtain a platinum phosphide nano-catalyst.

Application example

0.6 mg of the platinum phosphide nanocatalyst prepared in Example 6 was evenly loaded on the surface of a commercial carbon material (KetjenBlack EC-300J, platinum loading 20%). The loaded catalyst was dispersed in 5 mL of acetic acid and kept at 70 °C for 12 h to clean the surface of the catalyst, washed twice with ethanol solution after centrifugation, dried in an oven at 60 °C for 12 h, and then ultrasonically dispersed in 2 mL of water, isopropyl Alcohol and 5% nafion solution mixed solution (volume ratio is 4:1:0.02). Take 10 μL (containing 3 μg of platinum) of the above dispersion liquid and drop it on a glassy carbon electrode (with an area of 0.196 cm ² ) with a clean surface. After drying, the electrocatalytic oxygen reduction reaction performance test was performed on an AutolabPGSTAT302N electrochemical workstation. The test temperature was 25°C, and a three-electrode system was adopted, and the reference electrode and the counter electrode were Ag/AgCl and Pt foil electrodes, respectively. Cyclic voltammetry curves were obtained in _N2 -saturated 0.1M _HClO4 solution with a sweep rate of 50 mV/s. The linear sweep voltammetry test was carried out in an O ₂ atmosphere with a scan rate of 10 mV/s and an electrode rotation speed of 1600 rpm. The catalyst stability test was carried out in _O2 saturated 0.1M _HClO4 solution, the scan cycle range was 0.6-1.1V (relative to the standard hydrogen electrode potential), and the scan rate was 100mV/s. After the stability test, the cyclic voltammetry and Linear sweep voltammetry curve.

Figures 1-5 are transmission electron micrographs of the platinum phosphide nanocatalysts prepared in Examples 1 to 5, respectively, showing that as the reaction time prolongs, phosphorus atoms diffuse evenly into the platinum catalyst lattice, and the size of the nanocrystals increases. The morphology of the catalyst gradually evolved from the cube of the original platinum nanocatalyst to a near-spherical shape, which further proves that with the diffusion of phosphorus atoms, platinum nanocrystals evolve into platinum phosphide nanocrystals. At the same time, as the reaction progresses, the content of phosphorus atoms in platinum phosphide gradually increases, which also indicates that the composition of platinum phosphide catalyst can be precisely controlled by adjusting the reaction time.

Fig. 6 is a high-resolution transmission electron micrograph of the platinum phosphide nanocatalyst prepared in Example 5 and its corresponding Fourier transform image, which shows that the platinum phosphide nanocatalyst is rich in a large number of stacking fault defects.

Fig. 7 is the X-ray diffraction spectrum of the platinum phosphide nanocatalyst prepared in Example 5, and the generation of pure-phase platinum phosphide (molecular formula: Pt ₂ P) nanocrystals can be confirmed by analyzing the diffraction spectrum.

Fig. 8 and 9 are respectively the transmission electron micrograph and the X-ray diffraction spectrum of the platinum phosphide nano-catalyst prepared in embodiment six, and the catalyst particle size is 6.2nm, proves that small size pure phase platinum phosphide (molecular formula is Pt ₂ P) nanometer The formation of the catalyst indicates that the size of the platinum phosphide catalyst can be regulated by controlling the size of the platinum catalyst in step one.

Fig. 10 is a transmission electron micrograph of the small-sized platinum phosphide nanocatalyst loaded on commercial carbon black prepared in Example 6. It can be seen that the platinum phosphide nanoparticles are easy to load evenly, which is convenient for the research on the catalytic performance in the subsequent application examples.

FIG. 11 is a comparison chart of electrocatalytic oxygen reduction reaction performance between the platinum phosphide nanocatalyst in FIG. 9 and the platinum catalyst before phosphating. It can be seen from the data in the figure that the area activity of the platinum phosphide nanocatalyst is 10.2 times that of the platinum catalyst, and the mass activity is 10.3 times that of the platinum catalyst, indicating that the platinum phosphide nanocatalyst has excellent catalytic activity.

Fig. 12 is a comparison chart of electrocatalytic oxygen reduction reaction stability between the platinum phosphide nanocatalyst prepared in Example 6 of the present invention and the commercial platinum/carbon catalyst. It can be seen from the calculation of the data in the figure that after 10,000 and 30,000 cycle tests, the mass activity of the platinum phosphide nanocatalyst decreased by 6.8% and 9.1%, respectively. As a comparison, commercial platinum/carbon catalysts exhibited mass activity decreases of 22% and 55% after the same number of cycles. The activity loss of platinum phosphide nanocatalysts is much lower than that of commercial platinum/carbon catalysts, indicating its excellent catalytic stability.

Claims (10)

1. a preparation method of platinum phosphide nano-catalyst, is characterized in that, comprises the steps: Step 1, dispersing the platinum catalyst in a solvent to obtain a platinum catalyst dispersion; Step 2, adding a phosphorus source to the platinum catalyst dispersion in step 1, stirring evenly, reacting at 200-360° C. for 1-20 hours, centrifuging and washing after the reaction to obtain a platinum phosphide nano-catalyst. 2. The preparation method of platinum phosphide nano-catalyst according to claim 1, characterized in that, in step 1, the platinum catalyst is a platinum nanocrystal, a platinum-based alloy or a loaded platinum-based catalyst. 3. the preparation method of platinum phosphide nano-catalyst according to claim 2, is characterized in that, the particle diameter of platinum nano-crystal is 2-8nm. 4. the preparation method of platinum phosphide nano-catalyst according to claim 2, is characterized in that, described platinum base alloy is platinum cobalt, platinum nickel, platinum iron, platinum copper, platinum gold, platinum palladium, platinum cobalt nickel, platinum An alloy of rhodium palladium or platinum iron manganese. 5. the preparation method of platinum phosphide nano-catalyst according to claim 2, is characterized in that, the platinum-based catalyst of described load type is commercial platinum/carbon, platinum/alumina, platinum/silicon dioxide, platinum/titania Or platinum-loaded molecular sieves. 6. the preparation method of platinum phosphide nano-catalyst according to claim 1 is characterized in that, in step 1, described solvent is oleylamine, oleic acid, 1-octadecene, glycerol, formamide, quinolone phenoline, 1-chlorinated naphthalene, sulfolane, diphenyl ether or diphenyl sulfone. 7. the preparation method of platinum phosphide nano-catalyst according to claim 1 is characterized in that, in step 2, described phosphorus source is white phosphorus, red phosphorus, phosphine, phosphate, phosphite, hypophosphite , tri-n-octylphosphine, tri-n-octylphosphine oxide or triphenylphosphine. 8. the preparation method of platinum phosphide nano-catalyst according to claim 1 is characterized in that, in step 1, the concentration of platinum in the platinum catalyst dispersion is 0.01-10mg/mL; The molar concentration of species is lower than the molar concentration of platinum in the platinum catalyst. 9. The platinum phosphide nano-catalyst prepared by the preparation method described in any one of claims 1-8. 10. the application of platinum phosphide nano-catalyst described in claim 9 in electrocatalytic oxygen reduction.