CN112133930A

CN112133930A - Preparation method of ZIF-8-derived Pd-N-C oxygen reduction electrocatalyst

Info

Publication number: CN112133930A
Application number: CN202010984609.2A
Authority: CN
Inventors: 逯一中; 张华星; 姜媛媛; 陈传霞; 倪朋娟; 王波; 张成会
Original assignee: University of Jinan
Current assignee: University of Jinan
Priority date: 2020-09-18
Filing date: 2020-09-18
Publication date: 2020-12-25
Anticipated expiration: 2040-09-18
Also published as: CN112133930B

Abstract

The invention provides a preparation method of a ZIF-8 derived Pd-N-C oxygen reduction electrocatalyst, which is prepared by reducing Zn (NO)₃)₂•6H₂Adding O into methanol to obtain a mixed solution A; then adding dimethyl imidazole into methanol to obtain a mixed solution B; then adding the solution A into the solution B under vigorous stirring, and reacting at room temperature; washing and vacuum drying to obtain a product ZIF-8; adding the product into methanol, performing ultrasonic dispersion, adding sodium chloropalladate, stirring vigorously, performing centrifugal washing, and performing vacuum drying to obtain Pd/Zn ZIF; dispersing the prepared Pd/Zn ZIF into a buffer solution, quickly adding polydopamine, stirring, centrifugally washing, and drying in vacuum to obtain a product, namely Pd/Zn @ PDA ZIF; heating and preserving heat in nitrogen atmosphere to obtain a product recorded as Pd-N-C. The prepared catalyst has better conductivityElectrical property and excellent stability, and is expected to replace commercial platinum carbon.

Description

Preparation method of ZIF-8-derived Pd-N-C oxygen reduction electrocatalyst

Technical Field

The invention relates to a preparation method of a ZIF-8 derived Pd-N-C oxygen reduction electrocatalyst, belonging to the technical field of non-noble metal catalysts in electrocatalysis.

Background

The global use of fossil fuels has led to a series of environmental problems, and fuel cells are a new energy conversion device in which Oxygen Reduction Reaction (ORR) is an important cathode reaction thereof. The oxygen content in air is relatively high (21%), so that air can be used directly as a source of oxygen for the cathode reaction. However, ORR is inefficient, limiting the efficient energy conversion of fuel cells. Currently, commercial platinum carbon is a well-known catalyst with the best performance, but the platinum carbon is expensive due to the scarce reserves and limits the practical application of the platinum carbon due to the defects of poor stability and easy poisoning.

In order to reduce the cost of the catalyst, on the premise of keeping high ORR catalytic activity, the method which is generally adopted at present is to reduce the use amount of Pt or replace Pt by other non-noble metals. In the research and development of fuel cells, the search for non-noble transition metal nanocatalysts to replace noble metal catalysts has become a hotspot of the research on ORR catalysts. Transition metal-nitrogen-carbon (M-N-C) electrocatalysts (M = Au, Pd, Fe, Co, Ni, etc.) are considered to be the most promising commercial platinum-carbon candidate electrocatalysts due to high utilization of active sites, superior conductivity, coordination of metal sites with the matrix.

Disclosure of Invention

Aiming at the problems, the three-dimensional porous Pd-N-C oxygen reduction electrocatalyst with clear morphology is prepared by using sodium chloropalladate as a Pd source and using 2-methylimidazolium zinc salt MAF-4 (ZIF-8) as a precursor and a template. The obtained Pd-N-C catalyst has a half-wave potential of 0.75V (vs RHE) in alkaline conditions and performance close to that of commercial platinum carbon. In addition, the prepared catalyst has better conductivity and excellent stability, and is expected to replace commercial platinum carbon.

The invention is realized by the following technical scheme:

a ZIF-8 derived Pd-N-C oxygen reduction electrocatalyst is prepared by reducing Zn (NO)₃)₂•6H₂Adding O into methanol to obtain a mixed solution A; then adding dimethyl imidazole into methanol to obtain a mixed solution B; then rapidly adding the solution A into the solution B under vigorous stirring, and reacting at room temperature; centrifuging and washing the obtained product for several times, and vacuum-drying at 70 ℃ for one night to obtain a ZIF-8 product; adding the product into methanol, performing ultrasonic dispersion, adding sodium chloropalladate, stirring vigorously, performing centrifugal washing, and performing vacuum drying to obtain Pd/Zn ZIF; preparing a buffer solution, dispersing the prepared Pd/Zn ZIF into the buffer solution, performing ultrasonic dispersion, rapidly adding polydopamine under vigorous stirring, performing centrifugal washing after stirring, and performing vacuum drying to obtain a product, namely Pd/Zn @ PDA ZIF; and transferring the product to a porcelain boat, placing the porcelain boat in a tubular furnace, and heating and insulating the porcelain boat in a nitrogen atmosphere to obtain a product recorded as Pd-N-C.

Preferably, the mixed solution A is 1.68 g of Zn (NO)₃)₂•6H₂O was added to 20 mL of methanol, and 4.00 g of dimethylimidazole as a mixed solution B was added to 60 mL of methanol.

Preferably, the solution A is added into the solution B and then reacts for 24 hours at room temperature; the heating and heat preservation conditions are as follows: heating to 950 ℃ at a heating rate of 5 ℃ per second in a nitrogen atmosphere and keeping the temperature for 8 hours.

Preferably, the mass ratio of the ZIF-8 to the sodium chloropalladate to the polydopamine is 200: 17.3: 100.

preferably, the buffer solution is Tris, with a concentration of 10Mm, pH = 8.5.

The invention also provides the ZIF-8 derived Pd-N-C oxygen reduction electrocatalyst prepared by the preparation method.

The invention also provides the application of the Pd-N-C oxygen reduction electrocatalyst in a novel energy device.

Advantageous effects

The invention discloses a preparation method of a ZIF-8 derived Pd-N-C oxygen reduction electrocatalyst, which (1) has the advantages of simple preparation process, no pollution, rich raw materials and low price. (2) The electrocatalyst prepared by the method has the advantages of higher half-slope potential, excellent methanol poisoning resistance and higher stability. (3) The catalytic performance is close to commercial platinum carbon, the catalyst is expected to replace the commercial platinum carbon, and the oxygen reduction research on non-noble metal materials can provide reference for the application of novel energy devices.

Drawings

FIG. 1 TEM images of Pd-N-C at different scales (A) 100nm scale (B) (C) 50nm scale;

FIG. 2 (A) Pd-N-C catalyst prepared in N₂/O₂CV curve in (1); (B) ORR polarization curves of the prepared Pd-N-C catalyst in 0.1M KOH solution at different sweep rates; (C) and testing the stability of the prepared Pd-N-C catalyst.

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

(1) Preparation and characterization of Pd-N-C electrocatalyst: 1.68 g of Zn (NO)₃)₂•6H₂Adding O into 20 mL of methanol to obtain a mixed solution A; then adding 4.00 g of dimethyl imidazole into 60 mL of methanol to obtain a mixed solution B; then rapidly adding the solution A into the solution B under vigorous stirring, and reacting for 24 hours at room temperature; finally, centrifugally washing the obtained product for several times, and carrying out vacuum drying at 70 ℃ for one night to obtain a ZIF-8 product; adding 200mg of freshly prepared ZIF-8 into 50mL of methanol, performing ultrasonic dispersion for 20 minutes, adding 17.3 mg of sodium chloropalladate into the solution, violently stirring, performing centrifugal washing by the same method after 12 hours, and performing vacuum drying to obtain Pd/Zn ZIF; buffer solution (10 Mm, PH = 8.5) was prepared, the prepared Pd/Zn ZIF was dispersed into 50mL of buffer solution and ultrasonically dispersed for 20 minutes, and then 100 mg of polydopa was stirred vigorouslyAdding amine (PDA) quickly, stirring for 12h, centrifuging, washing, and drying in vacuum to obtain a product which is recorded as Pd/Zn @ PDA ZIF; and transferring the product to a porcelain boat, placing the porcelain boat in a tubular furnace, heating the porcelain boat to 950 ℃ in a nitrogen atmosphere at a heating rate of 5 ℃ per second, and keeping the temperature for 8 hours to obtain a product recorded as Pd-N-C. According to TEM images, the obtained catalyst maintains a framework of a regular dodecahedron structure after high-temperature pyrolysis, and Pd elements form uniformly distributed Pd nanoparticles after doping. FIG. 1 TEM images of Pd-N-C on different scales (A) 100nm scale (B) (C) 50nm scale.

(2) Electrochemical oxygen reduction test: all electrochemical tests were performed in a conventional three-electrode system at room temperature at the CHI 660 electrochemical station. A Rotating Disk Electrode (RDE), a Saturated Calomel Electrode (SCE) and a graphite rod were used as a working electrode, a reference electrode and a counter electrode, respectively. Both Cyclic Voltammetry (CV) and Linear Sweep (LSV) tests are at saturation N₂Or O₂In 0.1M KOH electrolyte. The scanning rates of CV and LSV were 50 mV s, respectively^-1And 10 mV s^-1。

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims

1. A process for preparing a ZIF-8 derived Pd-N-C oxygen reduction electrocatalyst, characterized in that Zn (NO) is added₃)₂•6H₂Adding O into methanol to obtain a mixed solution A; then adding dimethyl imidazole into methanol to obtain a mixed solution B; then rapidly adding the solution A into the solution B under vigorous stirring, and reacting at room temperature; the obtained productCentrifuging and washing the product for several times, and vacuum-drying at 70 ℃ for one night to obtain a product of ZIF-8; adding the product into methanol, performing ultrasonic dispersion, adding sodium chloropalladate, stirring vigorously, performing centrifugal washing, and performing vacuum drying to obtain Pd/Zn ZIF; preparing a buffer solution, dispersing the prepared Pd/Zn ZIF into the buffer solution, performing ultrasonic dispersion, rapidly adding polydopamine under vigorous stirring, performing centrifugal washing after stirring, and performing vacuum drying to obtain a product, namely Pd/Zn @ PDA ZIF; and transferring the product to a porcelain boat, placing the porcelain boat in a tubular furnace, and heating and insulating the porcelain boat in a nitrogen atmosphere to obtain a product recorded as Pd-N-C.

2. The method according to claim 1, wherein the mixed solution A is 1.68 g of Zn (NO)₃)₂•6H₂O was added to 20 mL of methanol, and 4.00 g of dimethylimidazole as a mixed solution B was added to 60 mL of methanol.

3. The preparation method of claim 1, wherein the solution A is added to the solution B and then reacted for 24 hours at room temperature; the heating and heat preservation conditions are as follows: heating to 950 ℃ at a heating rate of 5 ℃ per second in a nitrogen atmosphere and keeping the temperature for 8 hours.

4. The preparation method according to claim 1, wherein the mass ratio of ZIF-8 to sodium chloropalladate to polydopamine is 200: 17.3: 100.

5. the method of claim 1, wherein the buffer solution is Tris, at a concentration of 10Mm, and at pH = 8.5.

6. A ZIF-8 derived Pd-N-C oxygen reduction electrocatalyst prepared by the preparation process of any one of claims 1 to 5.

7. Use of the ZIF-8 derived Pd-N-C oxygen reduction electrocatalyst according to claim 6 in a novel energy device.