CN108736031B - Self-supporting PtCo alloy nanoparticle catalyst and preparation method and application thereof - Google Patents

Abstract

Translated fromChinese

本发明涉及一种自支撑PtCo合金纳米颗粒催化剂及其制备方法与应用，具体方法是通过液相手段在碳布上合成三维自支撑钴基金属有机框架(Co‑MOFs)纳米棒阵列结构，经过高温碳热还原技术获得一种三维多孔氮掺杂碳包覆金属钴纳米颗粒(Co@N‑C)纳米棒结构，并以此作为模板，利用金属Pt和Co氧化还原电势的差异，采用简易的电位置换反应方法最终获得了氮掺杂碳/PtCo(PtCo@N‑C)多孔催化剂。与现有技术相比，本发明的复合催化剂无需粘结剂和导电添加剂，具有优异的甲醇氧化性能和CO抗毒性，柔性碳布基底作为集流体，可弯曲可折叠，具有非常好的机械性能。

The invention relates to a self-supporting PtCo alloy nano-particle catalyst and a preparation method and application thereof. The specific method is to synthesize a three-dimensional self-supporting cobalt-based metal-organic framework (Co-MOFs) nano-rod array structure on a carbon cloth by means of liquid phase. A three-dimensional porous nitrogen-doped carbon-coated metal cobalt nanoparticle (Co@N‑C) nanorod structure was obtained by high-temperature carbothermic reduction technology, and the nanorod structure was used as a template. The potential displacement reaction method finally obtained nitrogen-doped carbon/PtCo (PtCo@N‑C) porous catalysts. Compared with the prior art, the composite catalyst of the present invention does not need binders and conductive additives, has excellent methanol oxidation performance and CO anti-toxicity, and the flexible carbon cloth substrate acts as a current collector, which can be bent and folded, and has very good mechanical properties. .

Description

Self-supporting PtCo alloy nanoparticle catalyst and preparation method and application thereof

Technical Field

The invention relates to the technical field of fuel cells, in particular to a self-supporting PtCo alloy nanoparticle catalyst and a preparation method and application thereof.

Background

Fuel cells, as an efficient energy conversion device, have the potential of low cost and zero emission, and are considered to be an important approach to solve the increasing energy crisis and environmental pollution problems of mankind. And the methanol has the advantages of high commercialization degree, high specific energy, good portability and the like, so that the direct methanol fuel cell has a very promising application prospect and draws wide attention of people. Platinum and platinum-based alloys remain among the most effective and stable catalysts for methanol oxidation among numerous electrocatalysts, however, platinum reserves are limited and expensive, greatly limiting its large-scale commercial use. In addition, the catalytic performance of platinum is also limited by its slow methanol oxidation kinetics and CO poisoning.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a self-supporting PtCo alloy nanoparticle catalyst with good catalytic activity, strong antitoxic ability and good mechanical property, and a preparation method and application thereof.

The purpose of the invention can be realized by the following technical scheme: a self-supporting PtCo alloy nanoparticle catalyst comprises three-dimensional porous nitrogen-doped carbon and Pt and Co coated inside the three-dimensional porous nitrogen-doped carbon, wherein the mass ratio of the Pt to the Co is (0.5-0.6): 1 the total mass of the Pt and the Co accounts for 43-48% of the mass of the catalyst, and the three-dimensional porous nitrogen-doped carbon is in an array structure. The invention adopts Pt and Co as the effective components of the catalyst, the combination of Pt and Co reduces the electron binding energy in Pt, and promotes C-H cracking reaction under low potential, thereby improving the activity and antitoxicity of the catalyst. Meanwhile, the precursor of the cobalt-based metal organic framework material is of a three-dimensional array structure, so that the porous nitrogen-doped carbon after calcination is also of an array structure. The highly graphitized porous nitrogen-doped carbon nanorod array has large specific surface area and high conductivity, provides ideal support for the dispersion of PtCO nano particles, and is favorable for promoting the migration of ions/protons; the doped nitrogen element can enhance the interaction between alloy particles and carbon and improve the stability of the catalyst; and the intrinsic catalytic capability of the porous nitrogen-doped carbon also makes a certain contribution to the improved catalytic activity.

A method for preparing the self-supporting PtCo alloy nanoparticle catalyst as described above, comprising the steps of:

(1) putting carbon cloth into an aqueous solution of acetone for ultrasonic treatment, washing and drying, and then putting the carbon cloth into a precursor solution to form a cobalt-based metal organic framework, wherein the precursor solution is a mixed aqueous solution of cobalt nitrate and dimethylimidazole;

(2) calcining the cobalt-based metal organic framework to obtain three-dimensional porous nitrogen-doped carbon coated with Co nanoparticles;

(3) soaking the obtained Co nanoparticle-coated three-dimensional porous nitrogen-doped carbon in H₂PtCl₄And (3) obtaining the self-supporting PtCo alloy nano-particle catalyst in a Pt solution.

The carbon cloth woven by the carbon fibers is a good three-dimensional conductive substrate material, so that the specific surface area of the prepared material can be increased, and the active sites can be increased; on the other hand, the active material grown on the carbon cloth can be directly used as a catalytic electrode, and the step of preparing the electrode like other powder catalysts is omitted. In the whole preparation process, Co is gradually replaced by Pt from outside to inside to form alloy particles.

The time for carrying out ultrasonic treatment on the carbon cloth in the aqueous solution of acetone is 20-30 min, and the carbon cloth is cleaned by ultrasonic.

Deionized water is adopted for washing, and the drying temperature is 60-80 ℃.

In the precursor solution, the molar ratio of cobalt nitrate to dimethyl imidazole is 1 (15-20).

The calcination is carried out on Ar and H₂Wherein Ar is Ar and H₂90 to 95 percent of the total volume. H₂The addition of the carbon nano-tube can promote the catalytic action of Co in the calcining process, and a plurality of carbon nano-tubes grow on the surface of the array structure, so that the specific surface area of the structure is increased.

Heating to 700-900 ℃ at a speed of less than 5 ℃/min, preserving heat for 2-4 h, and naturally cooling to room temperature. The cobalt-based metal organic framework array can be highly graphitized at 700-900 ℃, and the conductivity is increased.

Said H₂PtCl₄The concentration of the Pt solution is 0.5-2 mmol/L, and the Co nano-particle coated three-dimensional porous nitrogen-doped carbon is in H₂PtCl₄The soaking time in the Pt solution is 2-4 min.

Use of a self-supporting PtCo alloy nanoparticle catalyst as described above for use in the anode of a methanol fuel cell. The anode of the methanol fuel cell generates methanol oxidation reaction, and the cathode generates oxygen reduction reaction. The material prepared by the invention is a methanol oxidation catalyst, so the material is used for an anode of a methanol fuel cell.

Compared with the prior art, the beneficial effects of the invention are embodied in the following aspects:

(1) when the catalyst is used for the anode of a methanol fuel cell, the initial potential of methanol oxidation is high, and the current density of the anode is high;

(2) when the catalyst is used for an anode of a methanol fuel cell, the CO toxicity resistance and the durability are excellent.

Drawings

FIG. 1 is a three-dimensional porous Co @ N-C scanning electron microscope picture;

FIG. 2 is a planar scanning electron microscope image of a three-dimensional PtCo @ N-C catalyst;

FIG. 3 shows PtCo @ N-C and Pt/C at 0.5M H₂SO₄Is measured at a sweep rate of 50 mV/s.

FIG. 4 shows PtCo @ N-C and Pt/C at 0.5M CH₃OH+0.5M H₂SO₄Is measured at a sweep rate of 50 mV/s.

FIG. 5 shows PtCo @ N-C and Pt/C at 0.5M CH₃OH+0.5M H₂SO₄The peak current density of the electrolyte solution of (2) was compared with that of the electrolyte solution with the increase of the cycle number.

FIG. 6 shows PtCo @ N-C and Pt/C at 0.5M H₂SO₄The CV curve for CO antitoxicity tested in the electrolyte of (a).

Detailed Description

The following examples are given for the detailed implementation and specific operation of the present invention, but the scope of the present invention is not limited to the following examples.

Example 1

A preparation method of a self-supporting PtCo alloy nanoparticle catalyst comprises the following steps:

preparation of Co-MOFs nanorod array on carbon cloth

Firstly, selecting carbon cloth as a substrate, wherein the model is as follows: WOS 1002. And respectively putting the carbon cloth into acetone and deionized water for ultrasonic treatment for 20 minutes, finally washing with the deionized water, and putting into a forced air drying oven for drying.

Preparing a Co-MOFs precursor solution: 40ml of 25mM cobalt nitrate (Co (NO)₃)₂·6H₂O) was added rapidly to 40ml of 0.4M dimethylimidazole (C)₄H₆N₂) In an aqueous solution, and then stirred.

And soaking the treated carbon cloth in the Co-MOFs precursor solution at 30 ℃ for reaction for 4 hours. Then washing the product by deionized water.

And repeating the steps, and secondarily growing the Co-MOFs under the same temperature and reaction time.

Preparation of Co @ N-C nanorod array on carbon cloth

The Co-MOFs nanorod array prepared on the carbon cloth is subjected to Ar/H reaction at 800 DEG C₂(5％H₂95% Ar) for 2 hours, wherein the heating rate is 5 ℃/min. Naturally cooling to obtain the Co @ N-C nanorod array structure (figure 1).

Preparation of PtCo @ N-C nanorod array on carbon cloth

The prepared PtCo @ N-C nanorod array on the carbon cloth was placed in a stirred 1mM chloroplatinic acid (H)₂PtCl₆·6H₂O) for 3 minutes, labeled PtCo @ N-C. The reaction equation is:

Co+PtCl₄^2-→Co²⁺+Pt+4Cl^-

the PtCo @ N-C nanorod array prepared on the carbon cloth is subjected to Ar/H reaction at 400 DEG C₂(5％H₂95% Ar) for 1 hour, wherein the heating rate is 3.5 ℃/min. And naturally cooling to obtain the PtCo @ N-C nanorod array structure (shown in figure 2).

The mass of Pt and Co in the prepared PtCo @ N-C is 0.278mg cm^-2And 0.533mg cm^-2The corresponding atomic ratio is 14: 86.

The invention synthesizes a three-dimensional Co-MOFs nanorod structure with large specific surface area by a liquid phase method, obtains a Co @ N-C structure through annealing treatment, takes the Co @ N-C structure as a carrier, prepares a series of Pt loaded PtCo @ N-C catalysts by adopting a simple Pt precursor soaking method, and carries out system test and analysis on the electrocatalytic performance of the catalysts.

The electrocatalytic performance of the prepared PtCo @ N-C catalyst is tested by an electrochemical workstation under a three-electrode system. The PtCo @ N-C catalyst is used as a working electrode, Ag/AgCl (+0.197V vs RHE) soaked in a saturated KCl solution is used as a reference electrode, and a graphite rod is used as a counter electrode.

Before measurement, high-purity Ar is introduced into the electrolyte for 20 minutes,to remove CO and O in the solution₂。

The electrochemical active area of the prepared PtCo @ N-C catalyst is 0.5M H₂SO₄In a solution of (a), wherein the test voltage is in the range of 0 to 1.0V vs RHE and the sweep rate is 50mV s^-1。

The electrochemical active areas of the prepared PtCo @ N-C and Pt/C catalysts are respectively 20m²G and 14.2m²The/g, PtCo @ N-C catalyst exhibited a larger electrochemically active area (FIG. 3).

The methanol oxidation performance of the prepared PtCo @ N-C catalyst was improved by including 0.5M H₂SO₄And 0.5M CH₃Obtained by testing a voltammetry Curve (CV) in an OH mixed solution, wherein the test voltage range is 0-1.2V vs. RHE, and the sweep rate is 50mV s^-1。

The prepared PtCo @ N-C catalyst has more negative initial voltage (0.563V) than the Pt/C catalyst<0.642V) and greater positive peak current density (433.5mA mg^-1>140mA mg^-1). Thus, the PtCo @ N-C catalyst exhibited superior methanol oxidation activity (FIG. 4).

The methanol oxidation stability of the prepared PtCo @ N-C catalyst is 0.5M H₂SO₄And 0.5M CH₃Obtained by testing a CV curve of 100 continuous cycles in an OH mixed solution, wherein the test voltage interval is 0-1.2V vs. RHE, and the sweep rate is 50mV s^-1。

The anode peak current density retention of the prepared PtCo @ N-C and Pt/C catalysts after 100 cycles was 94.4% and 68.7% of the peak, respectively, indicating that the durability of the PtCo @ N-C catalysts was due to commercial Pt/C (FIG. 5).

The CO antitoxic performance of the prepared PtCo @ N-C catalyst is 0.5M H of CO saturation₂SO₄The test voltage interval is-0.1-1.4V vs RHE, and the sweep rate is 50mV s^-1. High purity CO gas and A r gas were passed into the electrolyte for 15 minutes each before the measurement to ensure that the catalyst active sites were covered with sufficient CO and that the solution was free of CO.

The prepared PtCo @ N-C and Pt/C catalysts have CO desorption peaks at 0.92V and 1.03V respectively, and the more negative CO desorption peaks of PtCo @ N-C prove that the prepared PtCo @ N-C has more excellent CO CO-solubility (figure 6).

Thus, the PtCo @ N-C catalyst prepared in this example has excellent methanol oxidation current density, CO poisoning resistance, and durability.

Example 2

A similar preparation method to that of example 1 was employed, except that:

(1) the ultrasonic treatment time of the carbon cloth in the aqueous solution of acetone is 20min, and the drying temperature of the carbon cloth is 60 ℃;

(2) the molar ratio of cobalt nitrate to dimethyl imidazole in the precursor solution is 1: 15.

(3) calcining at Ar and H₂Wherein Ar accounts for 90% of the total gas volume; the calcining temperature is 700 ℃, and the calcining time is 4 hours;

(4) h for soaking₂PtCl₄The concentration of the Pt solution is 0.5m mol/L, and the soaking time is 4 min.

The catalyst prepared in the embodiment is used for an anode of a methanol fuel cell, and tests show that the catalyst has higher current density and good CO anti-toxicity performance.

Example 3

A similar preparation method to that of example 1 was employed, except that:

(1) the ultrasonic treatment time of the carbon cloth in the aqueous solution of acetone is 30min, and the drying temperature of the carbon cloth is 80 ℃;

(2) the molar ratio of cobalt nitrate to dimethyl imidazole in the precursor solution is 1: 20.

(3) Calcining at Ar and H₂Wherein Ar accounts for 90 to 95 percent of the total gas volume; the calcining temperature is 900 ℃, and the calcining time is 2 hours;

(4) h for soaking₂PtCl₄The concentration of the Pt solution is 2m mol/L, and the soaking time is 2 min.

The catalyst prepared in the embodiment is used for an anode of a methanol fuel cell, and tests show that the catalyst has higher current density and good CO anti-toxicity performance.

Claims (9)

Translated fromChinese

1.一种自支撑PtCo合金纳米颗粒催化剂，其特征在于，该催化剂用于甲醇燃料电池的阳极，包括三维多孔氮掺杂碳以及包覆在三维多孔氮掺杂碳内部的Pt和Co，其中，所述Pt和Co的质量比为（0.5~0.6）：1， 所述Pt和Co总质量占催化剂质量的43%~48%，所述的三维多孔氮掺杂碳呈阵列结构；1. A self-supporting PtCo alloy nanoparticle catalyst, characterized in that, the catalyst is used for the anode of a methanol fuel cell, comprising three-dimensional porous nitrogen-doped carbon and Pt and Co wrapped inside the three-dimensional porous nitrogen-doped carbon, wherein , the mass ratio of the Pt and Co is (0.5-0.6): 1, the total mass of the Pt and Co accounts for 43%-48% of the catalyst mass, and the three-dimensional porous nitrogen-doped carbon is in an array structure;该催化剂的制备方法，包括以下步骤：The preparation method of the catalyst comprises the following steps:（1）将碳布放入丙酮的水溶液中进行超声处理，洗涤干燥，然后置于前驱体溶液中，形成钴基金属有机框架化物，其中，所述前驱体溶液为硝酸钴和二甲基咪唑的混合水溶液；(1) The carbon cloth is put into an aqueous solution of acetone for ultrasonic treatment, washed and dried, and then placed in a precursor solution to form a cobalt-based metal organic framework, wherein the precursor solution is cobalt nitrate and dimethylimidazole mixed aqueous solution;（2）将钴基金属有机框架化物煅烧，得到包覆Co纳米颗粒的三维多孔氮掺杂碳；(2) calcining the cobalt-based metal organic framework to obtain three-dimensional porous nitrogen-doped carbon coated with Co nanoparticles;（3）将得到的包覆Co纳米颗粒的三维多孔氮掺杂碳浸泡在H₂PtCl₄Pt溶液中，即得所述自支撑PtCo合金纳米颗粒催化剂；(3) soaking the obtained three-dimensional porous nitrogen-doped carbon coated with Co nanoparticles in a H₂ PtCl₄ Pt solution to obtain the self-supporting PtCo alloy nanoparticle catalyst;步骤（1）中，在30℃下，将处理好的碳布浸泡在前驱体溶液中反应4小时，然后用去离子水冲洗干净；重复上述步骤，在相同的温度和反应时间下，二次生长Co-MOFs，通过液相手段合成了具有大比表面积的三维Co-MOFs纳米棒结构。In step (1), the treated carbon cloth was soaked in the precursor solution for 4 hours at 30°C, and then rinsed with deionized water; the above steps were repeated, and at the same temperature and reaction time, two Co-MOFs were grown, and three-dimensional Co-MOFs nanorod structures with large specific surface area were synthesized by liquid-phase means.2.一种如权利要求1所述自支撑PtCo合金纳米颗粒催化剂的制备方法，其特征在于，包括以下步骤：2. a preparation method of self-supporting PtCo alloy nanoparticle catalyst as claimed in claim 1, is characterized in that, comprises the following steps:（1）将碳布放入丙酮的水溶液中进行超声处理，洗涤干燥，然后置于前驱体溶液中，形成钴基金属有机框架化物，其中，所述前驱体溶液为硝酸钴和二甲基咪唑的混合水溶液；(1) The carbon cloth is put into an aqueous solution of acetone for ultrasonic treatment, washed and dried, and then placed in a precursor solution to form a cobalt-based metal organic framework, wherein the precursor solution is cobalt nitrate and dimethylimidazole mixed aqueous solution;（2）将钴基金属有机框架化物煅烧，得到包覆Co纳米颗粒的三维多孔氮掺杂碳；(2) calcining the cobalt-based metal organic framework to obtain three-dimensional porous nitrogen-doped carbon coated with Co nanoparticles;（3）将得到的包覆Co纳米颗粒的三维多孔氮掺杂碳浸泡在H₂PtCl₄Pt溶液中，即得所述自支撑PtCo合金纳米颗粒催化剂。(3) soaking the obtained three-dimensional porous nitrogen-doped carbon coated with Co nanoparticles in a H₂ PtCl₄ Pt solution to obtain the self-supporting PtCo alloy nanoparticle catalyst.3.根据权利要求2所述的一种自支撑PtCo合金纳米颗粒催化剂的制备方法，其特征在于，所述的碳布在丙酮的水溶液进行超声处理的时间为20~30min。3. the preparation method of a kind of self-supporting PtCo alloy nano-particle catalyst according to claim 2, is characterized in that, the time that described carbon cloth carries out ultrasonic treatment in the aqueous solution of acetone is 20～30min.4.根据权利要求2所述的一种自支撑PtCo合金纳米颗粒催化剂的制备方法，其特征在于，所述洗涤采用去离子水，干燥温度为60~80℃。4 . The method for preparing a self-supporting PtCo alloy nanoparticle catalyst according to claim 2 , wherein the washing adopts deionized water, and the drying temperature is 60-80° C. 5 .5.根据权利要求2所述的一种自支撑PtCo合金纳米颗粒催化剂的制备方法，其特征在于，所述前驱体溶液中，硝酸钴和二甲基咪唑的摩尔为1:（15~20）。5. the preparation method of a kind of self-supporting PtCo alloy nanoparticle catalyst according to claim 2, is characterized in that, in described precursor solution, the mole of cobalt nitrate and dimethyl imidazole is 1:(15～20) .6.根据权利要求2所述的一种自支撑PtCo合金纳米颗粒催化剂的制备方法，其特征在于，所述煅烧在Ar和H₂的混合氛围中进行，其中，Ar占Ar和H₂总体积的90%~95%。6 . The method for preparing a self-supporting PtCo alloy nanoparticle catalyst according to claim 2 , wherein the calcination is carried out in a mixed atmosphere of Ar and H₂ , wherein Ar accounts for the total volume of Ar and H₂ . 90%~95%.7.根据权利要求6所述的一种自支撑PtCo合金纳米颗粒催化剂的制备方法，其特征在于，所述煅烧步骤为：以小于5℃/min升温到700~900℃，并保温2~4h后，自然降到室温。7. The preparation method of a self-supporting PtCo alloy nanoparticle catalyst according to claim 6, wherein the calcining step is: raising the temperature to 700-900°C at less than 5°C/min, and maintaining the temperature for 2-4h After that, it naturally came down to room temperature.8.根据权利要求2所述的一种自支撑PtCo合金纳米颗粒催化剂的制备方法，其特征在于，所述H₂PtCl₄Pt溶液的浓度为0.5~2mmol/L，包覆Co纳米颗粒的三维多孔氮掺杂碳在H₂PtCl₄Pt溶液中浸泡时间为2~4min。8. The method for preparing a self-supporting PtCo alloy nanoparticle catalyst according to claim 2, wherein the concentration of the H₂ PtCl₄ Pt solution is 0.5 to 2 mmol/L, and the three-dimensional coating of the Co nanoparticles The soaking time of porous nitrogen-doped carbon in H₂ PtCl₄ Pt solution is 2~4min.9.一种如权利要求1所述自支撑PtCo合金纳米颗粒催化剂的应用，其特征在于，该催化剂用于甲醇燃料电池的阳极。9 . An application of the self-supporting PtCo alloy nanoparticle catalyst as claimed in claim 1 , wherein the catalyst is used in the anode of a methanol fuel cell. 10 .

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