阅读说明：本技术 一种磷化铂纳米催化剂及其制备方法和在电催化氧还原中的应用 (Platinum phosphide nano-catalyst, preparation method thereof and application thereof in electrocatalytic oxygen reduction ) 是由 金明尚 郭瑞雲 于 2019-09-19 设计创作，主要内容包括：本发明提供一种磷化铂纳米催化剂及其制备方法和在电催化氧还原中的应用,包括如下步骤：1)将铂催化剂分散于溶剂中,搅拌均匀,得到铂催化剂分散液；2)向铂催化剂分散液中加入磷源,混合均匀后在一定温度下反应,待反应完成后离心、洗涤得到磷化铂纳米催化剂。本发明方法通过磷源分解产生的磷原子在一定温度下扩散进入铂催化剂中,合成具有特定电子结构的磷化铂纳米催化剂。该制备方法具有流程简单,成本低廉,重复性好,无环境污染、便于大批量制备的优点,且制备所得磷化铂纳米催化剂在电催化氧还原反应中显示出了远高于商业铂/碳催化剂的催化活性和稳定性,具有良好的应用前景。(The invention provides a platinum phosphide nano-catalyst, a preparation method thereof and application thereof in electrocatalytic oxygen reduction, comprising the following steps: 1) dispersing a platinum catalyst in a solvent, and uniformly stirring to obtain a platinum catalyst dispersion liquid; 2) adding a phosphorus source into the platinum catalyst dispersion liquid, uniformly mixing, reacting at a certain temperature, and centrifuging and washing after the reaction is finished to obtain the platinum phosphide nano-catalyst. The method synthesizes the platinum phosphide nano-catalyst with a specific electronic structure by diffusing phosphorus atoms generated by decomposing a phosphorus source into the platinum catalyst at a certain temperature. The preparation method has the advantages of simple flow, low cost, good repeatability, no environmental pollution and convenient mass preparation, and the prepared platinum phosphide nano-catalyst shows far higher catalytic activity and stability than a commercial platinum/carbon catalyst in an electrocatalytic oxidation-reduction reaction, thereby having good application prospect.)

1. A preparation method of a platinum phosphide nano-catalyst is characterized by comprising the following steps:

step 1, dispersing a platinum catalyst in a solvent to obtain a platinum catalyst dispersion liquid;

and 2, adding a phosphorus source into the platinum catalyst dispersion liquid obtained in the step 1, uniformly stirring, reacting at the temperature of 200-360 ℃ for 1-20h, and centrifuging and washing after the reaction is finished to obtain the platinum phosphide nano-catalyst.

2. The method for preparing a platinum phosphide nano-catalyst according to claim 1, wherein in the step 1, the platinum catalyst is a platinum nanocrystal, a platinum-based alloy or a supported platinum-based catalyst.

3. The method of preparing a platinum phosphide nanocatalyst according to claim 2, wherein the particle size of the platinum nanocrystals is 2 to 8 nm.

4. The method for preparing a platinum phosphide nano-catalyst according to claim 2, wherein 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.

5. The method of preparing a platinum phosphide nanocatalyst according to claim 2, wherein the supported platinum-based catalyst is commercial platinum/carbon, platinum/alumina, platinum/silica, platinum/titania or platinum-supported molecular sieve.

6. The method for preparing the platinum phosphide nanocatalyst according to claim 1, wherein in the step 1, the solvent is oleylamine, oleic acid, 1-octadecene, glycerol, formamide, quinoline, 1-chloronaphthalene, sulfolane, diphenyl ether or diphenyl sulfone.

7. The method for preparing a platinum phosphide nano-catalyst according to claim 1, wherein in the step 2, the phosphorus source is white phosphorus, red phosphorus, phosphine, phosphate, phosphite, hypophosphite, tri-n-octylphosphine oxide or triphenylphosphine.

8. The method for preparing a platinum phosphide nanocatalyst according to claim 1, wherein in the step 1, the concentration of platinum in the platinum catalyst dispersion liquid is 0.01-10 mg/mL; the concentration of the amount of phosphorus species in the phosphorus source used in step 2 is lower than the concentration of the amount of platinum species in the platinum catalyst.

9. The platinum phosphide nano-catalyst prepared by the preparation method of any one of claims 1 to 8.

10. Use of the platinum phosphide nanocatalyst of claim 9 in electrocatalytic oxygen reduction.

Technical Field

The invention belongs to the field of nano science, and particularly relates to a platinum phosphide nano catalyst, a preparation method thereof and application thereof in electrocatalytic oxygen reduction.

Background

The platinum catalyst shows excellent catalytic performance in the fields of energy, chemistry and petrochemical industry, and particularly plays a role in fuel cells, automobile exhaust purification, hydrogenation, dehydrogenation and other industrial catalytic reactions. However, due to the scarcity of platinum resources and the concentration in a few countries and regions, the price of platinum is expensive and the use cost is extremely high, which seriously hinders the large-scale application of platinum in modern industries. Therefore, the method for improving the catalytic performance of the platinum catalyst and reducing the platinum dosage becomes a great research hotspot of energy science at present, and has great significance for promoting economic development and saving resources.

Alloying platinum by introducing a second phase transition metal (such as palladium, gold, cobalt, nickel, copper, iron, lead, etc.) is a strategy for effectively improving the performance of the platinum catalyst. The method mainly improves the number of surface active sites of platinum or changes the binding energy of platinum with reactants, reactant intermediates and products by changing the electronic structure (5d empty rail) of platinum, thereby achieving the purposes of improving the catalytic activity of platinum and reducing the platinum dosage. However, the second phase transition metal component in the catalyst is easy to undergo corrosion dissolution and Ostwald ripening process (Nano Energy 2019,60,111-118) under the conditions of low pH value, high oxygen concentration, high humidity, different potentials and the like, so that the activity of the catalyst is damaged in the using process, the service life is shortened, and the process of commercial scale application of the catalyst is hindered. In addition, the platinum alloying technology is limited by its complicated preparation method and the use of expensive transition metals (such as gold and silver), so that it is not feasible to develop conditions in industry.

Recent research results show that compared with the modification of a platinum catalyst by adding a second phase metal element, the addition of a non-metal atom (such as H, B, N, C or P) into the metal catalyst has a larger influence on the electronic structure (nat. Comm.2014,5,5787, J.Mater. chem.A 2019,7,4714.), and further has better improvement on the catalytic performance. However, due to the strong bonding energy between platinum atoms and the large bonding energy (306.7 kJ/mol) (CRC press,2007), doping non-metal atoms into a platinum lattice to form PtX (X ═ H, B, N, C, P, or the like) remains a great challenge.

In recent years, transition metal phosphides (e.g., phosphorous compounds) have been usedNickel phosphide, cobalt phosphide, iron phosphide, rhodium phosphide, ruthenium phosphide and the like) has the advantages of low raw material cost (avoiding the use of second-phase transition metal), various preparation modes, high catalytic activity and stability and the like, and is widely applied to the research of electrocatalysis, energy storage, photocatalysis, chemical catalysis and the like. The porous surface oxidized cobalt phosphide nano-catalyst is reported to have good electrocatalytic oxygen reduction performance (J.Power Sources,2017,363,87-94), and the rhodium phosphide nano-catalyst shows high catalytic activity and stability in both electrocatalytic hydrogen evolution and oxygen evolution reactions (J.Am.chem.Soc.,2017,139, 5494-. The surface of the palladium catalyst can be rapidly modified by adding a phosphorus source to improve the selectivity of the palladium catalyst in the carbon monoxide catalytic reaction (patent CN107413359A), but the prepared catalyst is palladium-palladium phosphide with a core-shell structure, wherein the palladium phosphide is in an amorphous state, and the structure cannot be stably maintained in the catalytic reaction. In addition, although there have been many studies on metal phosphide, few studies on platinum phosphide nano-catalyst have been reported at present due to the limitations of difficult synthesis of platinum phosphide nano-crystal, harsh production conditions, complex preparation and few controllable factors. Such as PtP formation on a platinum catalyst core by Cramerikawa et al₂A surface layer and is applied to a fuel cell (patent CN 102365775B). However, the catalyst prepared by the method can only be synthesized on a carrier material, has no universality, needs vacuum and high-temperature calcination and other conditions, has high process cost, and is not beneficial to industrial large-scale production. Therefore, developing a low-cost and efficient way to obtain a platinum phosphide nano-catalyst with excellent catalytic activity and stability is a great challenge while having great significance.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a platinum phosphide nano-catalyst, a preparation method thereof and application thereof in electrocatalytic oxygen reduction.

The invention is realized by the following technical scheme:

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

step 1, dispersing a platinum catalyst in a solvent to obtain a platinum catalyst dispersion liquid;

and 2, adding a phosphorus source into the platinum catalyst dispersion liquid obtained in the step 1, uniformly stirring, reacting at the temperature of 200-360 ℃ for 1-20h, and centrifuging and washing after the reaction is finished to obtain the platinum phosphide nano-catalyst.

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

Furthermore, the particle size of the platinum nanocrystal is 2-8 nm.

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/silica, platinum/titania or platinum-supported molecular sieve.

Preferably, in step 1, the solvent is oleylamine, oleic acid, 1-octadecene, glycerol, formamide, quinoline, 1-chloronaphthalene, 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 oxide or triphenylphosphine.

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

The platinum phosphide nano-catalyst prepared by the preparation method.

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

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

in the invention, phosphorus atoms generated by decomposing a phosphorus source are diffused into the platinum catalyst lattice to prepare pure-phase platinum phosphide (with the molecular formula of Pt)₂P) nanocrystalline catalysts, specific forThe determined electronic structure weakens the binding energy of the catalyst to the intermediate of the oxygen reduction reaction, and shows excellent activity of the electrocatalytic oxygen reduction reaction. Meanwhile, the surface of the catalyst is rich in stacking fault defects, and the catalyst has a large number of dangling bonds and rich platinum reaction active sites, so that the electrocatalysis performance is further improved. More importantly, the platinum phosphide nano-catalyst has a good crystal structure (face-centered cubic structure) and is a pure phase, so that the catalyst has structural stability superior to other amorphous structures or heterogeneous catalysts, shows excellent catalytic stability in electrocatalysis reaction, avoids great reduction of catalyst activity in the catalytic process, and has great application potential in the field of electrocatalysis.

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

Further, the components of the catalyst can be regulated and controlled through reaction time, and the size of the catalyst can be accurately controlled through regulating and controlling the size of the original platinum catalyst.

The platinum phosphide nano-catalyst prepared by the invention is applied to electrocatalytic oxygen reduction reaction, has excellent catalytic activity and stability due to the characteristics of specific electronic structure, surface rich defect, stable structure in the reaction, good dispersibility and the like, and can meet the requirement of higher industrial application.

Drawings

FIG. 1 is a TEM photograph of Pt phosphide nanocatalyst prepared in the first example of the present invention, wherein the inset is an enlarged photograph of a single nanoparticle.

FIG. 2 is a TEM photograph of Pt phosphide nanocatalyst prepared in example II of the present invention, wherein the inset is an enlarged photograph of a single nanoparticle.

FIG. 3 is a TEM photograph of Pt phosphide nanocatalyst prepared in example III of the present invention, wherein the inset is an enlarged photograph of a single nanoparticle.

FIG. 4 is a TEM photograph of Pt phosphide nanocatalyst prepared in example IV of the present invention, wherein the inset is an enlarged photograph of a single nanoparticle.

FIG. 5 is a TEM photograph of Pt phosphide nanocatalyst prepared in example V of the present invention, wherein the inset is an enlarged photograph of a single nanoparticle.

FIG. 6 is a high-resolution TEM image of Pt phosphide nanocatalyst prepared in example V of the present invention, and the corresponding Fourier transform image is shown in the inset.

FIG. 7 is an X-ray diffraction spectrum of a platinum phosphide nanocatalyst prepared in example five of the present invention.

FIG. 8 is a TEM photograph of Pt phosphide nanocatalyst prepared in example six of the present invention.

FIG. 9 is a graph comparing the X-ray diffraction spectra of the Pt phosphide nano-catalyst prepared in example six and the Pt nano-particles as the raw material.

FIG. 10 is a TEM photograph of commercial carbon black loaded with Pt nano-catalyst prepared in example six of the present invention.

FIG. 11 is a graph comparing the electrocatalytic oxygen reduction reaction activity of the platinum phosphide nanocatalyst prepared in example six of the present invention and a commercial platinum/carbon catalyst.

FIG. 12 is a graph comparing the stability of electrocatalytic oxygen reduction reaction of the platinum phosphide nanocatalyst prepared in example six of the present invention and a commercial platinum/carbon catalyst.

Detailed Description

The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.

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

step 1, dispersing a platinum catalyst in a solvent to obtain a platinum catalyst dispersion liquid;

and 2, adding a phosphorus source into the platinum catalyst dispersion liquid obtained in the step 1, uniformly stirring, heating for reaction, and centrifuging and washing after the reaction is finished to obtain the platinum phosphide nano-catalyst.

In step 1, the platinum catalyst is platinum nanocrystal, platinum-based alloy or a supported platinum-based catalyst. The platinum-based alloy is a platinum-based binary alloy such as platinum cobalt, platinum nickel, platinum iron, platinum copper, platinum gold, platinum palladium, etc., a platinum-based ternary alloy such as platinum cobalt nickel, platinum rhodium palladium, platinum iron manganese, etc., a platinum-based multicomponent alloy, etc. The supported platinum-based catalysts are commercial platinum/carbon, platinum/alumina, platinum/silica, platinum/titania or platinum-supported molecular sieves.

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

In step 2, the phosphorus source is a simple substance of phosphorus element and compounds with various valence states (inorganic substances of phosphorus such as white phosphorus, red phosphorus, phosphine, phosphate, phosphite, hypophosphite and the like, and organic phosphorus reagents such as tri-n-octylphosphine, tri-n-octylphosphine oxide, triphenylphosphine and the like).

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

In the step 2, the reaction temperature is 200-.