阅读说明：本技术 Cu NPs-rGO电催化剂的制备方法及其应用 (Preparation method and application of Cu NPs-rGO electrocatalyst ) 是由 渠凤丽 郭晓茜 于 2019-10-31 设计创作，主要内容包括：本发明属于纳米新材料领域,具体涉及一种Cu NPs-rGO电催化剂的制备方法及其应用,通过水热法和氢氩混合气退火处理合成了二维的还原氧化石墨烯负载零价的铜纳米颗粒(Cu NPs-rGO),相比于氧化铜催化剂而言,零价铜催化剂更容易形成反馈π键,因此更容易吸附和活化氮气,提高催化活性,制备方法简单易行,本发明以还原性的氧化石墨烯作为基底能够进一步增强材料的导电性,也能更好的分散铜纳米颗粒和稳定单质铜,所制得的Cu NPs-rGO催化剂在-0.4V的电位下具有较高的产氨速率(24.58μg h<Sup>-</Sup><Sup>1</Sup>mgcat.<Sup>-1</Sup>)和法拉第效率(15.32％)。(The invention belongs to the field of new nano materials, and particularly relates to a preparation method and application of a Cu NPs-rGO electrocatalyst, wherein two-dimensional reduced graphene oxide loaded zero-valent copper nanoparticles (Cu NPs-rGO) are synthesized by a hydrothermal method and hydrogen-argon mixed gas annealing treatment, and compared with a copper oxide catalyst, the zero-valent copper catalyst is easier to form a feedback pi bond, so that nitrogen is easier to adsorb and activate, the catalytic activity is improved, and the preparation method is simple and easy to implement ‑ 1 mgcat. ‑1 ) And faraday efficiency (15.32%).)

1. A preparation method of a Cu NPs-rGO electrocatalyst is characterized by comprising the following steps: the method comprises the following steps:

(1) mixing CuAc₂·H₂Dissolving O and graphene oxide in water to prepare a mixed solution, and carrying out ultrasonic treatment on the mixed solution;

(2) transferring the mixed solution into an oven for hydrothermal reaction under the conditions of 175 ℃ and 180 ℃ for 2-2.5 hours, centrifuging the product after the hydrothermal reaction, and washing the product with water to obtain a solid product;

(3) freeze-drying the obtained solid product in a freeze dryer, taking out and grinding to obtain powder;

(4) and (3) placing the ground powder in a tube furnace, introducing atmosphere, and annealing at the temperature of 490-510 ℃ for 3-3.5h to obtain the finished product of the Cu NPs-rGO.

2. The method of preparing a Cu NPs-rGO electrocatalyst according to claim 1, characterized in that: CuAc₂·H₂The mass ratio of O to graphene oxide is 4-5: 1.

3. the method of preparing a Cu NPs-rGO electrocatalyst according to claim 1, characterized in that: the atmosphere is a mixture of argon and hydrogen.

4. The method of preparing a Cu NPs-rGO electrocatalyst according to claim 1, characterized in that: and dissolving the prepared CuNPs-rGO finished product and a Nafion solution in an ethanol solution, placing the solution in an ultrasonic machine for ultrasonic treatment, dripping the ultrasonic solution on the surface of carbon paper, and airing at room temperature to obtain the working electrode.

5. The method of preparing a Cu NPs-rGO electrocatalyst according to claim 1, characterized in that: the freeze-drying time is 20-24 hours.

6. The method of preparing a Cu NPs-rGO electrocatalyst according to claim 1, characterized in that: the prepared CuNPs-rGO has the following structure: and the surface of the rGO is uniformly loaded with zero-valent copper nanoparticles.

7. The method of preparing a Cu NPs-rGO electrocatalyst according to claim 1, characterized in that: the preparation method specifically comprises the following steps:

mixing 1.0mM CuAc₂·H₂Dissolving O and 50mg of graphene oxide in 35mL of water, placing the water in an ultrasonic machine for ultrasonic treatment for 1 hour, transferring the obtained liquid to a 50mL reaction kettle, placing the reaction kettle in an oven at 180 ℃ for hydrothermal reaction for 2 hours, taking the reaction kettle out after cooling to room temperature, centrifuging the reacted liquid, and washing the liquid with water for three times to remove unreacted CuAc₂·H₂And O, freeze-drying the solid obtained by centrifugation in a freeze dryer for 24 hours, finally grinding the solid, placing the ground solid in a tubular furnace, introducing mixed gas of hydrogen and argon, and annealing at 500 ℃ for 3 hours to obtain the CuNPs-rGO electrocatalyst.

8. Use of the prepared Cu NPs-rGO electrocatalyst according to claim 1, wherein: the application of the electrocatalyst used for nitrogen reduction in preparing ammonia gas by electrocatalysis of artificial nitrogen fixation.

9. Use of the Cu NPs-rGO electrocatalyst according to claim 8, characterized in that: the Cu NPs-rGO electrocatalyst is loaded on carbon paper and is used as a working electrode in the preparation of ammonia gas by electrocatalysis artificial nitrogen fixation.

10. Use of the Cu NPs-rGO electrocatalyst according to claim 9, characterized in that: the preparation method of the working electrode comprises the following steps: 10mg of CuNPs-rGO electrocatalyst and 40. mu.L of 5 wt% Nafion solution were dissolved in 960mL of a mixed solution containing 640mL of ethanol and 320mL of water, and the solution was sonicated in a sonicator for 1 hour to obtain a uniform solution, and then 10. mu.L of the above solution was dropped on clean carbon paper having an area of 1X 1cm, and naturally dried at room temperature.

Technical Field

The invention belongs to the field of new nano materials, and particularly relates to a preparation method and application of a Cu NPs-rGO electrocatalyst.

Background

Ammonia is an important industrial raw material and plays an irreplaceable role in the fields of agriculture, plastics, medicine, textile industry and the like. Because of the low liquefaction pressure of ammonia, the ideal hydrogen storage medium and the absence of carbon, etc., have been widely used. Currently, the industrial production of ammonia relies mainly on the conventional Haber-Bosch process, in which nitrogen and hydrogen are co-catalyzed by a heterogeneous catalyst at high pressure (150-300 atm) and high temperature (300-500 ℃ C.). However, this process consumes over 1% of the total global fossil energy annually, and results in carbon dioxide emissions of 300 million metric tons. Thus, there is a need for an economical, sustainable alternative. The realization of artificial nitrogen fixation from nitrogen and water by electrochemical catalysis under environmental conditions is an effective method for realizing clean, carbon-free and sustainable development, and has great potential, thus becoming a good choice for replacing the traditional Haber-Bosch process. However, an electrocatalyst for efficient nitrogen reduction is the most important part. The noble metal catalyst has the advantages of good conductivity, more active crystal faces, easy combination with reactants and the like, thereby showing excellent nitrogen reduction performance, but the practical application of the noble metal catalyst is limited by resource shortage, high cost and low Faraday efficiency. Therefore, it remains a great challenge to develop low-cost and earth-resource-rich electrocatalysts.

Copper is a cheap transition metal, and the unique physical and chemical properties of copper arouse great research interest. Copper-based materials can undergo a variety of reactions due to the wide range of valence states of copper. Generally, the feedback pi-bonding between metal and nitrogen weakens the N ≡ N bond, and plays a crucial role in the fixation and activation of nitrogen. Thus, the feedback pi-bonds are more easily formed for zero-valent copper catalysts than for copper oxide catalysts. On the other hand, the development of copper-based catalysts has been the most challenging to synthesize cheap zero-valent copper nanoparticle nano-particles with high activity, stability and oxidation resistance. In general, immobilization of copper nanoparticles on a substrate is an effective method. In recent years, Graphene Oxide (GO) has attracted much attention as an excellent catalyst carrier with characteristics of high specific surface area, good conductivity and strong nanoparticle coupling ability.

Disclosure of Invention

The invention aims to provide a preparation method of a Cu NPs-rGO electro-catalyst, and the prepared Cu NPs-rGO electro-catalyst is applied to electro-catalysis artificial nitrogen fixation for preparing ammonia gas, and has the advantages of high efficiency and high selectivity.

The preparation method of the Cu NPs-rGO electrocatalyst comprises the following steps:

(1) mixing CuAc₂·H₂Dissolving O and graphene oxide in water to prepare a mixed solution, and carrying out ultrasonic treatment on the mixed solution;

(2) transferring the mixed solution into an oven for hydrothermal reaction under the conditions of 175 ℃ and 180 ℃ for 2-2.5 hours, centrifuging the product after the hydrothermal reaction, and washing the product with water to obtain a solid product;

(3) freeze-drying the obtained solid product in a freeze dryer, taking out and grinding to obtain powder;

(4) and (3) placing the ground powder in a tube furnace, introducing atmosphere, and annealing at the temperature of 490-510 ℃ for 3-3.5h to obtain the finished product of the Cu NPs-rGO.

CuAc₂·H₂The mass ratio of O to graphene oxide is 4-5: 1.

the atmosphere is a mixture of argon and hydrogen.

And dissolving the prepared Cu NPs-rGO finished product and a Nafion solution in an ethanol solution, placing the solution in an ultrasonic machine for ultrasonic treatment, dripping the ultrasonic solution on the surface of carbon paper, and airing at room temperature to obtain the working electrode.

The freeze-drying time is 20-24 hours.

The prepared Cu NPs-rGO has the following structure: and the surface of the rGO is uniformly loaded with zero-valent copper nanoparticles.

As a preferable technical scheme, the preparation method of the Cu NPs-rGO electrocatalyst specifically comprises the following steps:

mixing 1.0mmol CuAc₂·H₂Dissolving O and 50mg of graphene oxide in 35mL of water, placing the water in an ultrasonic machine for ultrasonic treatment for 1 hour, transferring the obtained liquid to a 50mL reaction kettle, placing the reaction kettle in an oven at 180 ℃ for hydrothermal reaction for 2 hours, taking the reaction kettle out after cooling to room temperature, centrifuging the reacted liquid, and washing the liquid with water for three times to remove unreacted CuAc₂·H₂And O, freeze-drying the solid obtained by centrifugation in a freeze dryer for 24 hours, finally grinding the solid, placing the ground solid in a tubular furnace, introducing mixed gas of hydrogen and argon, and annealing at 500 ℃ for 3 hours to obtain the Cu NPs-rGO.

The Cu NPs-rGO electrocatalyst disclosed by the invention is applied to preparation of ammonia gas by electrocatalysis artificial nitrogen fixation as a nitrogen reduction electrocatalyst, and the Cu NPs-rGO electrocatalyst is loaded on carbon paper to serve as a working electrode during application.

The preparation method of the working electrode comprises the following steps: dissolving 10mg of Cu NPs-rGO electrocatalyst and 40 mu L of Nafion solution with the concentration of 5 wt% in 960mL of mixed solution, wherein the mixed solution contains 640 mu L of ethanol and 320 mu L of water, placing the mixed solution in an ultrasonic machine for ultrasonic treatment for 1 hour to obtain a uniform solution, then dripping 10 mu L of the solution on clean carbon paper with the area of 1 x 1cm, and naturally airing the solution at room temperature to obtain the working electrode.

In the invention, the Cu NPs-rGO electrocatalyst prepared by using the two-dimensional layered graphene to load the zero-valent copper nanoparticles has a very large specific surface area, good conductivity and strong coupling with the nanoparticles, so that the graphene and the copper nanoparticles are compounded, the copper nanoparticles can be effectively prevented from agglomerating, more copper active sites are exposed, and the conductivity of the copper nanoparticles can be further enhanced. The exposed active sites can adsorb and activate nitrogen molecules more easily, and the good conductivity can reduce the impedance in the reaction process, thereby being beneficial to the electro-catalytic nitrogen reduction reaction, and improving the Faraday efficiency and the ammonia production rate.

Compared with the prior art, the invention has the following beneficial effects.

(1) The preparation method is simple and easy to operate, the two-dimensional reduced graphene oxide loaded zero-valent copper nanoparticles (Cu NPs-rGO) are synthesized by a hydrothermal method and hydrogen-argon mixed gas annealing treatment, and compared with a copper oxide catalyst, the zero-valent copper catalyst is easier to form feedback pi bonds, so that nitrogen is easier to adsorb and activate, and the catalytic activity is improved;

(2) according to the invention, the reductive graphene oxide is used as a substrate, so that the conductivity of the material can be further enhanced, copper nanoparticles and stable elemental copper can be better dispersed, and the prepared Cu NPs-rGO catalyst has a higher ammonia production rate (24.58 mu g h) under a potential of-0.4V^-1mgcat.^-1) And faraday efficiency (15.32%).

Drawings

In FIG. 1, a is an X-ray diffraction pattern of a Cu NPs-rGO nano-catalyst; b is a scanning electron microscope image of the Cu NPs-rGO nano catalyst; c is a transmission electron microscope image of the Cu NPs-rGO nano catalyst; d is a high-resolution transmission electron microscope image of the Cu NPs-rGO nano catalyst; e-g are respectively a mapping chart of Cu, C and O elements of the Cu NPs-rGO nano catalyst;

in FIG. 2, a is a general X-ray photoelectron spectroscopy diagram of the Cu NPs-rGO nano-catalyst; b is a high-resolution X-ray photoelectron spectrum of a Cu element in a Cu NPs-rGO nano catalyst; c is an Auger spectrogram of Cu; d is a high-resolution X-ray photoelectron spectrum of a C element in a Cu NPs-rGO nano catalyst; e is a high-resolution X-ray photoelectron spectrum of O element in the Cu NPs-rGO nano catalyst; f is a Raman spectrogram of the CuNPs-rGO nano catalyst and the rGO;

in FIG. 3, a is a schematic diagram of a nitrogen reduction test; b is an instant current diagram of the Cu NPs-rGO nano catalyst under each potential; c is an ultraviolet absorption diagram of the Cu NPs-rGO nano catalyst under each potential; d is a graph of ammonia production rate and Faraday efficiency of the Cu NPs-rGO nano catalyst under each potential; e is the ammonia yield of different electrodes; f is the ammonia production rate when different copper nanoparticles are loaded;

in FIG. 4, a is a cycle test chart of the Cu NPs-rGO nano-catalyst at-0.4V; b is long-time i-t of the Cu NPs-rGO nano catalyst;

FIG. 5 is a graph of the ultraviolet absorption curve of hydrazine hydrate detected after Cu NPs-rGO nano-catalyst testing.

The Cu NPs-rGO nanocatalysts in FIGS. 1-5 were prepared as in example 1.

Detailed Description

The invention is further illustrated by the following examples and figures of the specification.