CN114628700A - Preparation method of platinum-nickel-gold alloy nano catalyst - Google Patents

Abstract

The invention discloses a preparation method of platinum-nickel-gold alloy nano-catalyst. The method includes the following steps: (1) preparing a mixed solution of metal ions: dissolving chloroplatinic acid, chloroauric acid and nickel salt in water, and adjusting the pH value to above 9; (2) preparing carbon black slurry: dispersing the carbon black in the mixed solution of water and ethylene glycol; (3) adding the metal ion mixed solution to the carbon black slurry, mixing, heating and reacting, the product is filtered, washed and dried; (4) the product obtained in step (3) is dispersed in In the mixed solution of water and ethanol, nickel salt is added, and after mixing, concentration and drying are performed to obtain a solid; (5) the solid obtained in step (4) is first reduced with hydrogen at high temperature, and then washed with a perchloric acid solution to obtain platinum-nickel-gold Alloy nanocatalysts. Compared with the prior art, the method of the present invention is simple to operate, can produce and prepare uniformly loaded platinum-nickel-gold alloy nano-catalysts on a large scale, and the prepared catalyst has good electrocatalytic activity.

Description

Preparation method of platinum-nickel-gold alloy nanocatalyst

technical field

The invention belongs to the field of catalysts for proton exchange membrane fuel cells, in particular to a preparation method of platinum-nickel-gold alloy nano-catalysts.

Background technique

Proton exchange membrane fuel cells use hydrogen energy as fuel. They have the advantages of small size, light weight, high energy conversion efficiency, no environmental pollution, wide source of raw materials, and long cruising range. They have broad application prospects and are considered to have the most commercial value. of fuel cells.

The proton exchange membrane fuel cell is mainly composed of membrane electrodes, end plates, flow field plates and external circuits. Among them, the membrane electrode is composed of a gas diffusion layer, a catalyst and a proton exchange membrane, and is the core component of the fuel cell. Electrode reactions also take place here. The two-stage reaction of the battery is as follows:

Anodic reaction: H ₂ → 2H ⁺ +2e ^-

Cathodic reaction: 4H ⁺ +4e ^- +O ₂ → 2H ₂ O

Overall reaction: 2H ₂ +O ₂ → 2H ₂ O

This reaction is a spontaneous reaction, but the reaction rate is extremely slow, which is limited by the reaction kinetics. It is necessary to use noble metals such as platinum and palladium as catalysts to improve the kinetic performance. However, the high cost of platinum catalysts currently used limits the commercial development of proton exchange membrane fuel cells. Therefore, the development of catalysts with higher activity is a key step to promote the commercial application of proton exchange membrane fuel cells.

A series of problems such as high cost of traditional commercial Pt/C catalysts, long-term operation leading to catalyst agglomeration, corrosion of carbon supports in high temperature and high acid working environment, and chemical degradation of proton exchange membranes restrict the commercialization of proton exchange membrane fuel cells. Chemical applications, in which the high cost of the catalyst itself is the main factor restricting the development of proton exchange membrane fuel cells. The introduction of some relatively inexpensive transition metals into pure platinum catalysts to form alloys can relatively reduce the amount of platinum used, and can adjust the electronic structure of platinum, reduce the d-band center, and improve the electrocatalytic activity of the catalyst. Incorporating high-stability gold metal into the alloy catalyst can improve the stability of the catalyst. However, the complex alloy dynamics and the bulk thermodynamic incompatibility of Au with other noble metals (eg: Pt, Ru, Rh) or transition metals (eg: Fe, Co, Ni) make PtAuM (M=Fe, Co , Ni) ternary alloy materials are extremely challenging to construct.

SUMMARY OF THE INVENTION

Based on the above prior art, the purpose of the present invention is to provide a method for preparing a platinum-nickel-gold alloy nano-catalyst.

To achieve the above object, the present invention adopts the following technical solutions:

The preparation method of platinum-nickel-gold alloy nano-catalyst comprises the following steps:

(1) Preparation of mixed solution of metal ions: chloroplatinic acid, chloroauric acid and nickel salt are dissolved in water, and the pH value is adjusted to above 9;

(2) Preparation of carbon black slurry: disperse carbon black in a mixed solution of water and ethylene glycol;

(3) adding the metal ion mixed solution to the carbon black slurry, mixing, heating and reacting, and the product is filtered, washed and dried;

(4) disperse the product obtained in step (3) in a mixed solution of water and ethanol, add nickel salt, and concentrate and dry after mixing to obtain a solid;

(5) the solid obtained in step (4) is first reduced with hydrogen at high temperature, and then washed with a perchloric acid solution to obtain a platinum-nickel-gold alloy nano-catalyst.

Preferably, the Pt loading of the platinum-nickel-gold alloy nanocatalyst is more than 40wt%.

More preferably, the Pt loading is 40wt% to 50wt%.

Preferably, in step (1), the concentration of chloroplatinic acid in the metal ion mixed solution is 1-3 wt%.

Preferably, chloroplatinic acid, chloroauric acid and nickel salt are charged according to the atomic ratio of Pt, Ni and Au of 3:2-6:0.1-1.5. Wherein, in step (1), 2/3 of the nickel salt is put in, and in step (4) the remaining nickel salt is put in.

The purpose of adding nickel salt in step (1) is to make nickel and platinum be reduced together in ethylene glycol solution; the purpose of adding nickel salt in step (4) is to suppress the growth of platinum-nickel-gold alloy particles in the high-temperature reduction process, thereby improving the catalyst activity.

More preferably, the atomic ratio of Pt, Ni, Au is 3:3:0.1.

Preferably, the nickel salt is nickel nitrate or nickel chloride.

Preferably, in step (2), the mass ratio of water and ethylene glycol is 0.1-1:1, and the concentration of carbon black is 0.1-1 wt%. Ethylene glycol is both a solvent and a reducing agent.

More preferably, the mass ratio of water and ethylene glycol is 0.3-0.4:1, and the concentration of carbon black is 0.4-0.5 wt%.

Preferably, in step (3), a microwave reactor is used to heat the reaction, the temperature is 180-190° C., and the time is 3-10 min. The use of microwave reactor can increase the nucleation rate and shorten the reaction time, which can be a good auxiliary for the preparation of catalysts.

The product obtained in step (3) can obtain good dispersibility in the mixed solution of water and ethanol, preferably, the mass ratio of water and ethanol is 0.5～3:5, more preferably, the mass ratio of water and ethanol is 1～ 2:5.

Preferably, in step (5), the temperature of hydrogen high-temperature reduction is 600-800° C., and the time is 1-3 h.

After high temperature reduction, some Ni fails to form an alloy with Pt, and washing with perchloric acid solution plays a role in dissolving and removing this part of unalloyed Ni.

beneficial effect

Compared with the prior art, the method of the invention is simple to operate, and can produce and prepare platinum-nickel-gold alloy nano-catalysts with uniform loading and order on a large scale, and the prepared catalyst has good electrocatalytic activity.

Description of drawings

Figure 1 is the XRD pattern of Pt ₃ Ni ₃ Au _0.1 /C and the PDF card of Pt;

Fig. 2 is the cyclic voltammogram of Pt ₃ Ni ₃ Au _0.1 /C;

FIG. 3 is a linear scan diagram of a half-cell of Pt ₃ Ni ₃ Au _0.1 /C.

FIG. 4 is a transmission electron microscope (TEM) image of Pt ₃ Ni ₃ Au _0.1 /C.

Detailed ways

The technical solutions of the present invention will be further detailed below in conjunction with the accompanying drawings and embodiments.

The preparation process of platinum-nickel-gold alloy nanocatalyst is as follows:

Dissolve chloroplatinic acid aqueous solution, chloroauric acid aqueous solution and two-thirds of nickel nitrate in water for ultrasonic dispersion for 10-20 min; add an appropriate amount of NaOH solution, adjust the pH value to 9, and obtain a metal ion mixed solution, and the concentration of chloroplatinic acid is 2wt %;

The carbon black ECP-600 was ultrasonically dispersed uniformly into a mixed solution with a mass ratio of water and ethylene glycol of 0.37:1, and ultrasonically dispersed for 20 min to obtain a carbon black slurry with a carbon black concentration of 0.45wt%;

The above-mentioned metal ion mixed solution is dropped dropwise into the carbon black slurry, and ultrasonically dispersed to uniformity to obtain a precursor solution, wherein the mass ratio of platinum in the chloroplatinic acid to the mass of carbon black ECP-600 is 1:1;

The precursor solution was put into a microwave reactor and heated to 186 °C, reacted for 5 min, cooled to 90 °C, taken out, filtered, washed and dried;

The dried samples were ultrasonically dispersed in a mixed solution with a mass ratio of water and ethanol of 1:5 for 20 min, and the remaining Ni(NO ₃ ) ₂ was added to ultrasonically disperse for 1 h, and steamed at 70°C in a water bath until smooth and thick. Dry at 60°C overnight to obtain a black solid;

The black solid was ground and placed in a high temperature tube furnace (heating rate 5°C/min), and 5 vol.% hydrogen-nitrogen mixture was used for reduction (temperature 700°C, time 2h) to obtain a crude PtNiAu catalyst;

Take 0.1 g of the crude catalyst and put it into 25 mL of 0.1 mol·L ^-1 perchloric acid solution, oil bath at 60 °C for 2 h, filter, wash and dry to obtain a carbon-supported PtNiAu catalyst. It can be seen from the TEM image that the PtNiAu supported on carbon black Alloy distribution is uniform and orderly.

By adjusting the atomic ratios of Pt, Ni, and Au during feeding, the ECSA (electrochemical Active area) and MA (oxygen reduction mass specific activity) are the highest, the XRD is shown in Figure 1, and the TEM image is shown in Figure 4.

sample name ECSA(m²·g_Pt^-1) MA(mA·g_Pt^-1) Example 1 Pt₃Ni₂Au_0.2/C 20.9 0.195 Example 2 Pt₃Ni₂Au_0.4/C 18.8 0.112 Example 3 Pt₃Ni₆Au_0.2/C 48.9 0.115 Example 4 Pt₃Ni₆Au_0.4/C 41.7 0.098 Example 5 PtNiAu_0.5/C 33.2 0.134 Example 6 PtNi_1.5Au_0.5/C 52.2 0.270 Example 7 Pt₃Ni₃Au_0.1/C 55.7 0.294

ECSA was calculated by measuring the cyclic voltammetry curve and MA was calculated by measuring the half-cell linear sweep curve.

Catalyst metal composition of Pt ₃ Ni ₃ Au _0.1 /C measured by ICP

Finally, it should be noted that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it is still The technical solutions described in the foregoing embodiments may be modified, or some technical features thereof may be equivalently replaced. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. The preparation method of platinum-nickel-gold alloy nano-catalyst, comprising the following steps: (1) Preparation of mixed solution of metal ions: chloroplatinic acid, chloroauric acid and nickel salt are dissolved in water, and the pH value is adjusted to above 9; (2) Preparation of carbon black slurry: disperse carbon black in a mixed solution of water and ethylene glycol; (3) adding the metal ion mixed solution to the carbon black slurry, mixing, heating and reacting, and the product is filtered, washed and dried; (4) disperse the product obtained in step (3) in a mixed solution of water and ethanol, add nickel salt, and concentrate and dry after mixing to obtain a solid; (5) the solid obtained in step (4) is first reduced with hydrogen at high temperature, and then washed with a perchloric acid solution to obtain a platinum-nickel-gold alloy nano-catalyst. 2 . The preparation method according to claim 1 , wherein the Pt loading of the platinum-nickel-gold alloy nanocatalyst is more than 40 wt %; preferably, the Pt loading is 40 wt % to 50 wt %. 3 . 3 . The preparation method according to claim 1 , wherein in step (1), the concentration of chloroplatinic acid in the metal ion mixed solution is 1-3 wt %. 4 . 4. preparation method according to claim 1 is characterized in that: chloroplatinic acid, chloroauric acid and nickel salt are 3:2～6:0.1～1.5 feed intake by Pt, Ni, Au atomic ratio; Preferably, Pt , Ni, Au atomic ratio of 3:3:0.1. 5. The preparation method according to claim 1 or 4, wherein the nickel salt is nickel nitrate or nickel chloride. 6. preparation method according to claim 1 is characterized in that: in step (2), the mass ratio of water and ethylene glycol is 0.1～1:1, and the concentration of carbon black is 0.1～1wt%; Preferably, The mass ratio of water and ethylene glycol is 0.3-0.4:1, and the concentration of carbon black is 0.4-0.5 wt%. 7. The preparation method according to claim 1, characterized in that: in step (3), a microwave reactor is used to heat the reaction, the temperature is 180～190°C, and the time is 3～10min. 8. preparation method according to claim 1 is characterized in that: in step (4), the mass ratio of water and ethanol is 0.5～3:5; Preferably, the mass ratio of water and ethanol is 1～2:5 . 9 . The preparation method according to claim 1 , characterized in that: in step (5), the temperature of hydrogen high-temperature reduction is 600-800° C., and the time is 1-3 h. 10 . 10. The platinum-nickel-gold alloy nanocatalyst prepared by any one of claims 1-9.

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