阅读说明：本技术 一种二维MXene/铁钴基复合催化材料的制备及其应用 (Preparation and application of two-dimensional MXene/iron-cobalt-based composite catalytic material ) 是由 张蓉仙 胡志晨 柯文韬 尚子彬 唐燕 于 2020-05-09 设计创作，主要内容包括：本发明属于锌空气电池及电化学催化技术领域,涉及一种二维MXene/铁钴基复合催化材料的制备方法及应用；具体步骤为：首先在酸液中加入MAX粉末通过化学刻蚀,经洗涤,离心,冷冻干燥后得MXene二维材料；再经过插层,剥离得MXene纳米片溶液并与金属盐复合而得；本发明合成方法所需设备简单,操作方便成本低；可以有效解决OER及ORR催化剂存在的价格昂贵,催化性能单一,稳定性差及储量低问题,可提高析氧反应速率以及锌空气电池的可逆性；该催化材料具有高比表面积和高导电性,在碱性条件下显示出较好的电催化性能,可应用于析氧反应以及锌空气电池电极催化材料。(The invention belongs to the technical field of zinc-air batteries and electrochemical catalysis, and relates to a preparation method and application of a two-dimensional MXene/iron-cobalt-based composite catalytic material; the method comprises the following specific steps: adding MAX powder into acid liquor, and carrying out chemical etching, washing, centrifuging, and freeze-drying to obtain MXene two-dimensional material; then intercalation and stripping are carried out to obtain MXene nano-sheet solution which is compounded with metal salt to obtain the compound; the synthesis method of the invention has the advantages of simple required equipment, convenient operation and low cost; the problems of high price, single catalytic performance, poor stability and low reserve of OER and ORR catalysts can be effectively solved, and the oxygen evolution reaction rate and the reversibility of a zinc-air battery can be improved; the catalytic material has high specific surface area and high conductivity, shows good electrocatalytic performance under alkaline conditions, and can be applied to oxygen evolution reaction and zinc-air battery electrode catalytic materials.)

1. A preparation method of a two-dimensional MXene/iron-cobalt-based composite catalytic material is characterized by comprising the following specific steps:

(1) adding MAX powder into acid liquor, placing the mixture into a constant-temperature water bath kettle, magnetically stirring, standing, centrifugally washing until the supernatant of a sample is neutral, collecting a centrifugal substrate, and freeze-drying to obtain an MXene two-dimensional material;

(2) intercalating the MXene two-dimensional material prepared in the step (1) in a dimethyl sulfoxide solution, removing oxygen, sealing and stirring, centrifuging to collect solids, and diluting with ionized water to obtain an intercalated MXene solution; ultrasonically stripping MXene solution in an ice water bath, centrifuging and collecting clear liquid to obtain stripped MXene nanosheet solution, introducing N₂Sealing, and sealing in shade;

(3) taking the MXene nanosheet solution stripped in the step (2) and a metal salt M (NO)₃) And mixing the solutions, stirring for reaction, standing, centrifuging, washing, and drying in a vacuum drying oven to obtain the two-dimensional MXene/Fe-Co based composite catalytic material.

2. The method for preparing the two-dimensional MXene/iron cobalt based composite catalytic material as claimed in claim 1, wherein the acid solution in step (1) is 40 wt% hydrofluoric acid; the MAX powder is Ti₃AlC₂(ii) a The dosage ratio of the acid solution to the MAX powder is 15-30 mL:1 g.

3. The preparation method of the two-dimensional MXene/iron cobalt-based composite catalytic material as claimed in claim 1, wherein the freeze drying in step (1) is specifically that the material is frozen in a refrigerator for 24-48 h, and then transferred to a freeze drier, wherein the freeze drying temperature is less than or equal to-45 ℃.

4. The method for preparing the two-dimensional MXene/iron cobalt based composite catalytic material as claimed in claim 1, wherein the dosage ratio of MXene two-dimensional material to dimethyl sulfoxide solution in step (2) is 0.5 g: 20-25 mL.

5. The method for preparing the two-dimensional MXene/iron cobalt based composite catalytic material as claimed in claim 1, wherein the concentration of the intercalated MXene solution obtained by diluting the collected solid in the step (2) in the ionized water is 0.6-0.7 mg/mL.

6. The method for preparing the two-dimensional MXene/iron cobalt-based composite catalytic material as claimed in claim 1, wherein the MXene nanosheet solution in step (3) is mixed with M (NO)₃)_nThe volume ratio of the solution is 25-35: 10.

7. The method for preparing the two-dimensional MXene/Fe-Co based composite catalyst material as claimed in claim 1, wherein M (NO) in step (3)₃)_nThe solution consists of Co (NO)₃)₂·6H₂O、Fe(NO₃)₃·9H₂O and deionized water, wherein the molar ratio of Co to Fe is 2: 1.

8. The preparation method of the two-dimensional MXene/iron cobalt based composite catalytic material as claimed in claim 1, wherein the stirring reaction time in step (3) is 10-24 h.

9. The preparation method of the two-dimensional MXene/iron cobalt-based composite catalytic material as claimed in claim 1, wherein the centrifugal rotation speed in steps (1) - (3) is 3500-5000 r/min.

10. The use of the two-dimensional MXene/Fe-Co based composite catalytic material prepared by the method according to any one of claims 1 to 9 in oxygen evolution reaction and zinc-air battery electrode catalytic materials.

Technical Field

The invention belongs to the technical field of zinc-air batteries and electrochemical catalysis, and relates to a preparation method of a two-dimensional MXene/Fe-Co based composite catalytic material and application of the two-dimensional MXene/Fe-Co based composite catalytic material in oxygen evolution reaction and zinc-air battery electrode catalytic materials.

Background

With the rapid development of society, the traditional fossil energy is exhausted day by day, the environmental problem is prominent day by day, and the zinc-air battery with low cost, high energy density, good safety and high environmental protection has received wide attention. The zinc storage capacity is rich, and the zinc-air battery has the theoretical energy density as high as 1086Wh/kg, so the zinc-air battery is an ideal energy storage and conversion device. However, the power density of practical zinc-air batteries is generally low and the reversibility is poor. The air cathode catalyst can accelerate ORR and OER and maintain OH^-And O₂Has important functions in the aspects of concentration balance and battery reversibility, however, the common electrocatalysts for ORR and OER are Pt/C and RuO respectively₂/IrO₂The problems of single catalytic activity, poor stability, low reserve, high cost and the like exist, and the application of the zinc-air battery is greatly limited.

Similarly, for the pollution-free and renewable hydrogen production process by electrolyzing water, the OER electrocatalyst mainly used is RuO₂/IrO₂The scarcity and the high cost of the method seriously limit the development of the water electrolysis hydrogen production industry. The transition metal with rich earth reserves has good conductivity and thermal stability, has good catalytic oxygen evolution activity in alkaline electrolyte, and is a good choice for replacing noble metal as an OER reaction catalyst; meanwhile, two-dimensional MXene is an emerging transition metal carbide, and has a unique 2D structure and electronic properties, a high specific surface area and high conductivity. The prepared MXene/transition metal composite catalytic material comprisesBetter OER and ORR catalytic activity, and improved reaction rate of oxygen evolution reaction and reversibility of zinc-air battery.

At present, a literature report shows that an MXene and polypyrrole composite electrode material is prepared based on MXene, but the problems that self-stacking phenomenon easily occurs between MXene sheets, the charge transmission capability is insufficient, the electrochemical utilization rate is low and the like still exist.

Disclosure of Invention

In view of the deficiencies in the prior art, the present invention is directed to solving one of the problems set forth above; the material is prepared by mixing, stirring and reacting two-dimensional MXene serving as a metal carbon layer material source and cobalt nitrate hexahydrate and ferric nitrate nonahydrate serving as a cobalt source and an iron source. The invention can provide inspiration for developing the research of novel two-dimensional MXene metal composite catalytic materials, can effectively solve the problems of high price, single catalytic performance, poor stability and low reserve of OER and ORR catalysts, and can improve the oxygen evolution reaction rate and the reversibility of zinc-air batteries.

In order to achieve the purpose, the invention provides a preparation method of a two-dimensional MXene/iron cobalt-based composite catalytic material, wherein the two-dimensional MXene/iron cobalt-based composite catalytic material is prepared by adding MAX powder into acid liquor, carrying out chemical etching, washing, centrifuging, carrying out freeze drying to obtain an MXene two-dimensional material, carrying out intercalation and stripping to obtain an MXene nanosheet solution, and compounding the MXene nanosheet solution with a metal salt.

The method specifically comprises the following steps:

(1) adding MAX (ternary transition metal carbide and nitride) powder into acid liquor, placing the mixture into a constant-temperature water bath kettle for magnetic stirring, standing, centrifugally washing until the supernatant of a sample is neutral, collecting a centrifugal substrate, and carrying out freeze drying to obtain an MXene two-dimensional material;

(2) intercalating the MXene two-dimensional material prepared in the step (1) in a dimethyl sulfoxide solution, removing oxygen, sealing and stirring, centrifuging to collect solids, and diluting with ionized water to obtain an intercalated MXene solution; ultrasonically stripping MXene solution in an ice water bath, centrifuging and collecting clear liquid to obtain stripped MXene nanosheet solution, introducing N₂Sealing, and sealing in shade;

(3) taking the MXene nanosheet solution stripped in the step (2) and a metal salt M (NO)₃)_nAnd mixing the solutions, stirring for reaction, standing, centrifuging, washing, and drying in a vacuum drying oven to obtain the two-dimensional MXene/iron-cobalt-based composite catalytic material.

Preferably, the acid solution in the step (1) is 40 wt% of HF (hydrofluoric acid); the MAX powder is Ti₃AlC₂(ii) a The dosage ratio of the acid solution to the MAX powder is 15-30 mL:1 g.

Preferably, the freeze drying in the step (1) is specifically that the raw materials are firstly placed in a refrigerator for freezing for 24-48 hours and then transferred to a freeze dryer, and the freeze drying temperature is less than or equal to-45 ℃.

Preferably, the dosage ratio of the MXene two-dimensional material to the dimethyl sulfoxide solution in the step (2) is 0.5 g: 20-25 mL.

Preferably, the collected solid in the step (2) is diluted in the ionized water to prepare an intercalated MXene solution, and the concentration of the intercalated MXene solution is 0.6-0.7 mg/mL.

Preferably, the MXene nanosheet solution in step (3) is mixed with M (NO)₃)_nThe volume ratio of the solution is 25-35: 10.

Preferably, M (NO) as described in step (3)₃)_nThe solution consists of Co (NO)₃)₂·6H₂O、Fe(NO₃)₃·9H₂O and deionized water, wherein the molar ratio of Co to Fe is 2: 1; said M (NO)₃)_nThe pH of the solution was 10.

Preferably, the stirring reaction time in the step (3) is 10-24 h.

Preferably, the centrifugal rotation speed in the steps (1) - (3) is 3500-5000 r/min.

The two-dimensional MXene/iron-cobalt-based composite catalytic material prepared by the method is applied to oxygen evolution reaction and zinc-air battery electrode catalytic materials.

The invention has the beneficial effects that:

(1) the synthesis method of the invention has the advantages of simple required equipment, convenient operation and low cost; the problems of high price, single catalytic performance, poor stability and low reserve of OER and ORR catalysts can be effectively solved, and the oxygen evolution reaction rate and the reversibility of the zinc-air battery can be improved.

(2) The catalytic material with the 2D nanosheet structure with the attached nanoparticles and the square holes prepared by the method develops the research of a novel two-dimensional MXene metal composite catalytic material, and has better OER and ORR catalytic activity; at a current density of 10mA cm^-2The overpotential of the OER is 428mV, the half-wave potential of the catalytic ORR is 580mV, and the limiting current is-5.4 mA cm^-2(ii) a Can be used as an electrocatalyst of renewable fuel cells, rechargeable zinc-air cells and the field of water electrolysis.

Drawings

FIG. 1 is a scanning electron microscope image of the material prepared in example 1, wherein a is a scanning electron microscope image of MXene nanosheets prepared in example 1, and b is a scanning electron microscope image of MXene-FeCo prepared in example 1.

FIG. 2 is an X-ray diffraction pattern of MXene powder and MXene-FeCo prepared in example 1.

FIG. 3 is a LSV graph of MXene-FeCo prepared in example 1 as an electrolytic water oxygen evolution reaction catalyst.

FIG. 4 is a solution of MXene-FeCo prepared in example 1 in 0.1mol/L KOH, N₂And O₂CV curve on rotating ring disk electrode under atmosphere.

FIG. 5 is a solution of MXene-FeCo prepared in example 1 in 0.1mol/L KOH, N₂And O₂And after the CV test under the atmosphere, an LSV test chart with the rotating speed of 1600rpm is carried out on the electrode of the rotating ring plate at different rotating speeds (400-1600 rpm).

Detailed Description

It will be understood by those skilled in the art that the following examples are illustrative of the present invention only and should not be construed as limiting in any way.

The raw materials used in the invention are all conventional commercial products.

Unless otherwise specified, the Oxygen Evolution (OER) activity and oxygen reduction (ORR) activity of the catalyst prepared by the present invention were evaluated by the following methods.

Taking 4mg of catalyst, ultrasonically dispersing in 1mL of absolute ethyl alcohol, adding 20 mu L of 5% Nafion solution, ultrasonically forming uniform slurry, then coating the slurry on a glassy carbon electrode, and carrying out electrochemical test after the electrode is dried.

The OER test is as follows:

1) the electrochemical system is a standard three-electrode system (a glassy carbon electrode attached with a catalyst is used as a working electrode, a platinum wire is used as an auxiliary electrode, a Saturated Calomel Electrode (SCE) is used as a reference electrode), and an electrolyte is a 1.0mol/L KOH solution.

2) Evaluating the activity of Oxygen Evolution (OER), and performing a linear sweep voltammetry test (LSV), wherein the voltage sweep range is 0-0.8V, and the sweep rate is 2mV s^-1。

The ORR test is as follows:

electrochemical measurements were carried out on a Rotating Ring Disk Electrode (RRDE) at different spin rates in an oxygen-saturated KOH solution (0.1 mol/L). The scanning rate is 2mV s^-1And the rotation rate of a Ring Disk Electrode (RDE) is 400-2500 rpm.