阅读说明：本技术 一种MXene负载纳米合金催化剂、制备方法及其应用 (MXene loaded nano alloy catalyst, preparation method and application thereof ) 是由 周迪红 于 2020-12-08 设计创作，主要内容包括：本发明提供了一种MXene负载纳米合金催化剂、应用及其应用方法,包括作为载体的MXene二维材料以及负载于载体上的纳米合金,MXene载体为单层或多层的片层分散结构,纳米合金的颗粒大小为2-3nm。制备方法为将MXene前驱体经过分散预处理后得到的层状MXene材料,浸渍在金属盐混合溶液中进行超声处理；然后滴加NaBH4溶液,搅拌均匀,离心后在高温下反应,得到MXene负载的纳米合金氮还原电催化剂。本发明通过MXene负载的合金纳米颗粒具有较好的热稳定性和化学稳定性,合金颗粒在2-3nm左右,并且分布均匀,在低的催化剂量下,氮还原电催化效果好于同类其他碳材料负载的催化剂,催化剂100％转化率可以维持在100h以上。(The invention provides an MXene supported nano alloy catalyst, application and an application method thereof, and the MXene supported nano alloy catalyst comprises an MXene two-dimensional material serving as a carrier and a nano alloy loaded on the carrier, wherein the MXene carrier is of a single-layer or multi-layer lamellar dispersed structure, and the particle size of the nano alloy is 2-3 nm. The preparation method comprises the steps of dipping a layered MXene material obtained by carrying out dispersion pretreatment on an MXene precursor in a metal salt mixed solution for ultrasonic treatment; then adding NaBH4 solution dropwise, stirring uniformly, centrifuging and reacting at high temperature to obtain the MXene-loaded nano-alloy nitrogen reduction electrocatalyst. The MXene-loaded alloy nanoparticles have good thermal stability and chemical stability, the alloy particles are about 2-3nm and are uniformly distributed, the nitrogen reduction electrocatalysis effect is better than that of catalysts loaded by other similar carbon materials under low catalyst dosage, and the 100% conversion rate of the catalysts can be maintained above 100 h.)

1. An MXene supported nano alloy catalyst is characterized by comprising an MXene material serving as a carrier and a nano alloy supported on the carrier, wherein the MXene carrier is of a single-layer or multi-layer lamellar dispersed structure, and the particle size of the nano alloy is 2-3 nm.

2. The MXene-supported nanoalloy catalyst of claim 1, wherein the nanoalloy is composed of 2 of Mo, Pt, Ru, Au, Pd, Cu, Fe.

3. The MXene-supported nanoalloy catalyst of claim 1, wherein the nanoalloy is supported at a loading of 1-3 wt% based on the mass of the support.

4. The preparation method of the MXene supported nano alloy catalyst is characterized by comprising the following steps of:

1) dipping a layered MXene material obtained by carrying out dispersion pretreatment on an MXene precursor in a metal salt mixed solution for ultrasonic treatment;

2) dropwise adding NaBH4 solution into the mixed solution after ultrasonic treatment, stirring uniformly, centrifuging and reacting at high temperature to obtain the MXene-loaded nano-alloy nitrogen reduction electrocatalyst.

5. The MXene-supported nano alloy catalyst according to claim 1, wherein the MXene precursor in step 1) is Ti₂AlC、V₂AlC、Ti₃AlC₂、Mo₂AlC and Nb₂One or more of AlC.

6. The method for preparing the MXene-supported nano alloy catalyst according to claim 4, wherein the specific method for performing dispersion pretreatment on the MXene material in the step 1) comprises the following steps: standing MXene material in 10% hydrofluoric acid water solution at 120 deg.C for 300min, and centrifuging and drying to obtain layered MXene powder.

7. The method for preparing the MXene-supported nano alloy catalyst according to claim 6, wherein the N-methyl pyrrolidone is added into the hydrofluoric acid aqueous solution during the dispersion pretreatment in the step 1), and the mass concentration of the N-methyl pyrrolidone after the addition is 0.2%.

8. The method for preparing the MXene-supported nano-alloy catalyst of claim 4, wherein the mass-to-volume ratio of the layered MXene material to the NaBH4 solution in step 2) is 1 g/mL.

9. The method for preparing the MXene-supported nano alloy catalyst as claimed in claim 4, wherein the reaction temperature in step 2) is 250-420 ℃.

10. Use of an MXene supported nanoalloy catalyst as catalyst in the preparation of ammonia by nitrogen reduction according to any one of claims 1 to 3.

Technical Field

The invention relates to the technical field of electrochemical catalysis, in particular to an MXene supported nano alloy catalyst, a preparation method and application thereof.

Background

In a nitrogen reduction (NRR) experiment, the Haber method is always an important technology in the traditional industrial field, in the method, hydrogen and nitrogen synthesize ammonia under the environment of catalyst, high temperature and high pressure, but the ammonia conversion rate is only 10% -15%, so that the development of the method for synthesizing ammonia with simple operation, low consumption, low pollution and high conversion rate is very important.

The electrochemical ammonia synthesis method can ensure that the thermodynamic non-spontaneous ammonia synthesis reaction is not limited by or less by thermodynamic equilibrium under the promotion of electric energy, realize the normal-temperature normal-pressure synthesis of ammonia, and the search for high-efficiency electrocatalysts becomes the technical core of the field.

The nano metal material is a catalyst with high conversion rate and high stability for petrochemical industry, automobile exhaust purification and organic synthesis reaction, and is also an electrocatalyst for various electrochemical reactions (such as NRR, HER, OER and ORR), the material has high conductivity, and the high density of non-coordinated surface atoms can adsorb various reactants. For example, Ru nanoparticles grown on carbon fibers have been widely used as excellent NRR electrocatalysts, achieving high faradaic efficiency, 5.4% at 10 mV. Also as on carbon black supported palladium nanoparticles (Pd/C), faradaic efficiency was 8.2% at 0.1V for electrocatalytic reduction of N2 to NH 3. However, in practical application, nanoparticles are easy to agglomerate, and part of noble metals are expensive and difficult to separate, so that further development of the nanoparticles is inhibited.

The choice of support is of crucial importance for the supported catalyst. MXenes is a class of two-dimensional inorganic compounds consisting of several atom thick transition metal carbides, nitrides or carbonitrides, which combine the metallic conductivity and hydrophilicity of transition metal carbides. Particularly when HF is used as the etchant, the intercalation and delamination steps under ultrasound exfoliate the material into individual flakes, resulting in flakes with lateral dimensions of several hundred nanometers, which studies have been well bedding the material for catalysis.

The supported nano metal catalyst alloyed with some transition metals in the form of nano alloy shows enhanced catalytic or electrocatalytic activity to various reactions, and the alloy nano catalyst also has good thermal stability and chemical stability. Therefore, by combining the advantages of the MXene carrier and the nano alloy in the field of electrocatalysis, the MXene-loaded nano alloy catalyst has very important significance in the process of nitrogen reduction electrocatalysis. Currently, MXenes is used as a carrier-supported metal catalyst, and as disclosed in patent application No. 201910216542.5, MXenes-supported PtRhFe ternary alloy catalysts are known, MXenes are widely used in the aspect of supporting metal alloy catalysts, but the size of metal alloys is large and reaches more than 50nm, and the adopted preparation method usually requires a surfactant, and the post-treatment method is complex, and a large number of means are required to remove surface groups brought in the supporting process.

Disclosure of Invention

The invention aims to solve the defects in the prior art, and provides an MXene supported nano alloy catalyst, a preparation method and application thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

an MXene supported nano alloy catalyst comprises an MXene two-dimensional material serving as a carrier and a nano alloy supported on the carrier, wherein the MXene carrier is of a single-layer or multi-layer lamellar dispersed structure, and the particle size of the nano alloy is 2-3 nm.

Preferably, the nano alloy is formed by randomly combining 2 elements of molybdenum, platinum, ruthenium, gold, palladium, copper and iron.

Preferably, the loading amount of the nano alloy is 1 to 3 wt% based on the mass of the carrier.

The invention also provides a preparation method of the MXene supported nano alloy catalyst, which comprises the following steps:

1) dipping a layered MXene material obtained by carrying out dispersion pretreatment on an MXene precursor in a metal salt mixed solution for ultrasonic treatment;

2) dropwise adding a NaBH4 solution into the mixed solution after ultrasonic treatment, uniformly stirring, centrifuging, and reacting at high temperature to obtain an MXene-loaded nano alloy nitrogen reduction electrocatalyst;

preferably, MXene precursor in step 1) is Ti₂AlC、V₂AlC、Ti₃AlC₂、Mo₂AlC and Nb₂One or more of AlC.

Preferably, the specific method for the MXene material dispersion pretreatment in the step 1) comprises the following steps: standing MXene material in 10% hydrofluoric acid water solution at 120 deg.C for 300min, and centrifuging and drying to obtain layered MXene powder.

Preferably, N-methyl pyrrolidone is added into the hydrofluoric acid aqueous solution during the dispersion pretreatment in the step 1), and the mass concentration of the added N-methyl pyrrolidone is 0.2%.

Preferably, the layered MXene material obtained in the step 2) is mixed with NaBH₄The mass-to-volume ratio of the solution was 1 g/mL.

Preferably, the reaction temperature in step 2) is 250-420 ℃.

The metal salt mixed solution is one or more of molybdenum salt, platinum salt, ruthenium salt, gold salt, palladium salt, copper salt and iron salt.

The invention also provides an application of the MXene supported nano alloy catalyst, and the MXene supported nano alloy catalyst is used as a catalyst in preparation of ammonia by nitrogen reduction.

The method for applying the catalyst in the preparation of ammonia by nitrogen reduction comprises the following steps: reaction gas N₂And H₂Is 3: 1, introducing the mixture into an electrochemical reaction tank at the flow rate of 100ml/min, raising the temperature from room temperature to the temperature for completely converting N2 by a temperature program of 0.5 ℃ min < -1 >, adding the MXene supported nano alloy catalyst prepared in the application, and measuring the 100% conversion rate of the nitrogen reduction electrocatalysis to be more than 100 h.

MXenes is a class of two-dimensional inorganic compounds consisting of several atom thick transition metal carbides, nitrides or carbonitrides, which combine the metallic conductivity and hydrophilicity of transition metal carbides. Particularly when HF is used as the etchant, the intercalation and delamination steps under ultrasound exfoliate the material into individual flakes, resulting in flakes with lateral dimensions of several hundred nanometers, which studies have been well bedding the material for catalysis. MXenes has more applications in the aspect of loading metal alloy catalysts at present, but the size of metal alloys is larger and reaches more than 50nm, and the adopted preparation method usually needs a surfactant, the post-treatment mode is complex, a large amount of means are needed to remove surface groups brought in the loading process, and the catalytic effect is poor.

Has the advantages that: by adopting the method, the MXene-loaded alloy nanoparticles have better thermal stability and chemical stability, the alloy particles are about 2-3nm and are uniformly distributed, the nitrogen reduction electrocatalysis effect is better than that of catalysts loaded by other similar carbon materials under the low catalyst dosage, and the 100% conversion rate of the catalyst can be maintained above 100 h.

Drawings

Fig. 1 is a transmission electron micrograph of MXene after dispersion in example 1.

FIG. 2 is an electron micrograph of the catalyst of example 1, after Mxene supports 1% nano Pt-Mo alloy.

FIG. 3 is an electron microscope image of the catalyst after Mxene is loaded with 3% nanometer Pt-Mo alloy.

FIG. 4 is a graph of Faraday efficiency of MXene supported nano Pt-Mo alloy catalyst for nitrogen reduction.

FIG. 5 is a graph of nitrogen conversion for different alloy particle loadings and different alloy compositions.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.

Example 1

Ti₃C₂Pt-Mo alloy particle-loaded (loading amount is 1.0%) catalyst and preparation thereof

Weighing MXene precursor Ti₂Grinding AlC, then dispersing 1g of the ground AlC in 60ml of hydrofluoric acid aqueous solution with the mass concentration of 10-25%, stirring for 20h, then washing and centrifuging for multiple times, and drying in an oven at 80 ℃ to obtain well-dispersed Ti₃C₂A material. The material was then allowed to stand for 300min in a 10% aqueous hydrofluoric acid solution (0.2% N-methylpyrrolidone added) at a temperature of 120 ℃ and then centrifugally dried, weighing 0.1 g of the Ti after delamination₃C₂The material was immersed in 20ml of a mixed solution of ammonium molybdate (2% by mass) and platinum dichloride (2% by mass), sonicated, and transferred to a round-bottom flaskStirring in a bottle, and dropwise adding 0.1ml of NaBH₄And (3) reducing the solution, stirring, centrifugally separating, and placing in a high-temperature oven (350 ℃) in an oxygen-free environment for 1000min to prepare the MXene-loaded nano alloy nitrogen reduction electrocatalyst.

The nitrogen reduction electrocatalytic reaction is carried out in a self-assembled electrochemical reaction cell. Weighing 0.05g of catalyst, dispersing in a mixed solution of ethanol and deionized water, adding a naphthol solution, mixing, performing ultrasonic treatment, then dispersing a certain amount of mixed solution on a pretreated glassy carbon disc, and drying for later use.

The data of the electrochemical measurement is completed by an electrochemical workstation, the manufactured electrode is used as a working electrode, a carbon rod/Pt wire is used as a counter electrode, and an Ag/AgCl, Hg/HgO or saturated calomel electrode is used as a reference electrode to assemble a three-electrode test system so as to independently research the catalytic performance of the working electrode; the electrolyte is divided into 1.0M H acidity₂SO₄Solution and basic 1.0M KOH solution. The volume ratio of the reaction gas is N₂：H₂3: 1, introducing the mixture at the flow rate of 100ml/min, and controlling the flow rate through a rotameter. The nitrogen reduction conversion rate under other conditions and different temperatures is examined through experiments. The experimental temperature was programmed from room temperature to a temperature at which nitrogen was completely converted at 0.5 ℃ min-1 by means of a temperature controller. The tail gas is analyzed on line by a gas chromatograph, a chromatographic column of the tail gas is a TDX-01 packed column with the thickness of 3m, argon is used as a carrier, the temperature of a column box is 80 ℃, the sample introduction temperature is 150 ℃, the temperature of a thermal conductivity cell is 110 ℃, and the bridge current is 80 mA. The nitrogen reduction conversion rate was calculated by the formula (1).

N₂Conversion [% ], ((1-x [ + ]. alpha.)/x)₀)*100％

Wherein x is₀Is N before reaction₂The percentage content in the mixed gas, x is N after reaction₂Alpha is a correction factor.

Example 2

Ti₃C₂Au-Cu alloy particle-loaded (loading amount is 3.0%) catalyst and preparation thereof

Weighing MXene precursor Ti₂Grinding AlC, and then taking 1g of the ground AlC to be dispersed in 10-25% of hydrofluoric acidStirring the acid aqueous solution for 20 hours in 60ml of acid aqueous solution, then washing and centrifuging the acid aqueous solution for many times, and drying the acid aqueous solution in an oven at 80 ℃ to obtain the well-dispersed Ti₃C₂A material. The material was then allowed to stand for 300min in a 10% aqueous hydrofluoric acid solution (0.2% N-methylpyrrolidone added) at a temperature of 120 ℃ and then centrifugally dried, weighing 0.1 g of the Ti after delamination₃C₂The material is immersed in 20ml of mixed solution of gold chloride (mass concentration 2%) and copper chloride (mass concentration 2%), transferred to a round bottom flask after ultrasonic treatment and stirred, and then is reduced by dripping 0.1ml of NaBH4 solution, stirred, and then placed in a high-temperature oven (390 ℃) in an oxygen-free environment for 1000min after centrifugal separation, so that the MXene-supported nano-alloy nitrogen reduction electrocatalyst is prepared. N is a radical of₂The catalytic reaction test conditions were the same as in example 1.

Example 3

Mo₂Preparation of C-loaded Ru-Fe alloy particle (loaded 3.0%) catalyst

Weighing MXene precursor Mo₂Grinding AlC, then taking 1g of the obtained product to disperse in 60ml of hydrofluoric acid aqueous solution with the mass concentration of 10-25%, stirring for 20h, then washing and centrifuging for multiple times, and drying in an oven at 80 ℃ to obtain well-dispersed Mo₂And C, material. The material was then allowed to stand for 300min in a 10% aqueous hydrofluoric acid solution (0.2% N-methylpyrrolidone added) at a temperature of 120 ℃ and then centrifugally dried, weighing 0.1 g of the layered Mo₂And soaking the material C in 20ml of a mixed solution of ruthenium chloride (mass concentration is 2%) and ferric nitrate (mass concentration is 2%), performing ultrasonic treatment, transferring the mixed solution to a round-bottom flask, stirring, dropwise adding 0.1ml of NaBH4 solution, reducing, stirring, performing centrifugal separation, and placing the obtained product in a high-temperature oven (420 ℃) in an oxygen-free environment for 1000min to prepare the MXene-supported nano-alloy nitrogen reduction electrocatalyst. N is a radical of₂The catalytic reaction test conditions were the same as in example 1.

In fig. 1, it is shown that the layered MXene after dispersion of example 1 can be used for subsequent nano-metal particle loading.

An electron microscope image of the catalyst of example 1Mxene loaded with 1% nanometer Pt-Mo alloy in FIG. 2 shows that the particles are uniformly distributed, and the alloy can be uniformly loaded on the carrier.

An electron microscope image of the catalyst in which the Mxene is loaded with 3% of nano Pt-Mo alloy in figure 3 shows that the nano particles are uniform in particle size and good in thermal stability.

The Faraday efficiency graph of MXene supported nano Pt-Mo alloy catalyst in nitrogen reduction in FIG. 4 shows that the catalysis efficiency is high.

Fig. 5 is a graph of nitrogen conversion rates for different alloy particle loadings and different alloy compositions, and it is seen from the graph that these types of alloy catalysts have better performance and are superior to both the unsupported system and the graphene (carbon material) supported system. And the temperature at which the Au — Cu alloy-supported catalyst reaches 100% conversion is the lowest.

The MXene-loaded alloy nanoparticles have good thermal stability and chemical stability, the alloy particles are about 2-3nm and are uniformly distributed, the nitrogen reduction electrocatalysis effect is better than that of catalysts loaded by other similar carbon materials under low catalyst dosage, and the 100% conversion rate of the catalyst can be maintained above 100 h.

The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present invention, and are intended to be included within the scope of the present invention.