CN114892203B

CN114892203B - Method for synthesizing carbon monoxide by electrochemical catalytic conversion of carbon dioxide

Info

Publication number: CN114892203B
Application number: CN202210341469.6A
Authority: CN
Inventors: 谭醒醒; 孙晓甫; 韩布兴; 郭伟伟; 徐亮
Original assignee: Institute of Chemistry CAS
Current assignee: Institute of Chemistry CAS
Priority date: 2022-04-02
Filing date: 2022-04-02
Publication date: 2023-10-10
Anticipated expiration: 2042-04-02
Also published as: CN114892203A

Abstract

The invention discloses a method for synthesizing carbon monoxide by electrochemical catalytic conversion of carbon dioxide. The method adopts an electrochemical catalytic system consisting of a copper-based catalyst/gas diffusion electrode composite material modified by transition metal, electrolyte and a flowing electrolytic cell device. The invention designs the copper-based catalyst/gas diffusion electrode composite material modified by the transition metal for the first time as a cathode material to be applied to the electrochemical catalytic conversion of carbon dioxide to synthesize carbon monoxide with high selectivity and high current density. The electrocatalyst provided by the invention is simple to prepare, low in cost and good in stability, can simultaneously realize high current density, high selectivity and long-time stable electrocatalytic conversion of carbon dioxide into carbon monoxide, greatly improves the product selectivity efficiency and current density of the copper-based catalyst in a carbon dioxide electrocatalytic system, and has potential industrial value.

Description

Method for synthesizing carbon monoxide by electrochemical catalytic conversion of carbon dioxide

Technical Field

The invention belongs to the field of chemistry and chemical engineering, and particularly relates to a method for synthesizing carbon monoxide by electrochemical catalytic conversion of carbon dioxide.

Background

Since the industrial revolution, the massive use of fossil fuels has led to atmospheric carbon dioxide (CO ₂ ) The concentration increases sharply. CO in the global atmosphere ₂ The concentration has risen from 280ppm in 1750 to 415ppm in 2021, causing a series of environmental problems such as global warming and ocean acidification. CO ₂ Is one of the main greenhouse gases and is also a rich, nontoxic and renewable C1 resource. How to effectively reduce, convert and utilize CO ₂ Is one of the most urgent tasks for humans. Much research effort has been devoted to this area and has developed a variety of conversions and uses of CO ₂ Including thermochemical, biochemical, electrochemical, photochemical, radiochemical, and the like. In which CO is converted electrochemically ₂ Due to mild reaction conditions, regulatable reaction products, green clean reaction processes and renewable sources of electricity (nuclear, wind, tidal) are receiving a great deal of attention.

In electrocatalytic CO ₂ During the conversion process, CO can be converted by multiple electron transfer ₂ Is converted into high added value carbon-based fuels and chemicals such as carbon monoxide (CO), alkane, alkene, alcohols, esters and the like. However, these products have similar redox potentials, resulting in poor selectivity for the particular product. Thus, in electrocatalytic conversion of CO ₂ Before becoming a viable option for storing renewable energy sources, there is a need to address the issues of high energy efficiency and selectivity. CO is used as an important industrial gas raw material and is widely used for metal processing, fuel and synthesis of basic chemicals; in particular, it is one of the components of synthesis gas, which can be processed downstream by Fischer-Tropsch chemistry to synthesize a range of organic chemical products. However, the high temperature reaction process involved in the conventional CO production method is energy-consuming and slow in reaction speed, and produces unwanted by-products and is limited by high costs. Electrocatalytic CO production ₂ The conversion to CO only involves a two electron transfer process, and the product has high selectivity, simple separation process and low conversion cost. Thus, CO is converted into ₂ Electrocatalytic conversion to CO is achieved on an industrial scale ₂ Electrochemical reduction is the most economical and technically feasible method.

The catalyst is the core of the electrocatalytic reaction, and the electrocatalytic catalyst with high activity, high selectivity and long service life is CO ₂ The primary task in the field of electrotransformation research. In recent years much research has been focused on designing CO ₂ High efficiency electrocatalysts for conversion to CO. Au and Ag are CO ₂ The good catalyst for reducing CO can inhibit the activity of the catalyst on hydrogen evolution reaction by designing different Au and Ag nano structures, thereby improving the selectivity on CO products. However, au and Ag catalysts are noble metalsCatalysts, which are limited in reserves and expensive, limit their large-scale practical use. Therefore, the research on inexpensive and efficient non-noble metal catalysts is to realize low-cost electrocatalytic conversion of CO ₂ One of the key scientific problems in the production of CO. The non-noble metal copper-based catalyst is CO ₂ One of important research systems of electric conversion has the designability of adjustability, and is expected to realize high-efficiency, high-selectivity and adjustable CO by accurately controlling the size, composition, morphology and structure of a Cu-based nano catalyst and assisting in the research on the catalytic mechanism of the catalyst and the reaction paths of different products in the reaction process by means of instrument characterization and the like ₂ And (5) electric conversion. However, the existing copper-based catalyst system is difficult to realize high current density, high selectivity and stable electrocatalytic conversion of CO for a long time ₂ Is CO. Therefore, the research of the copper-based catalyst with low cost, high efficiency and industrialization prospect is important, and is a research hotspot and an important point in the field at present.

Disclosure of Invention

It is an object of the present invention to provide an electrode material.

The electrode material is a copper-based catalyst/gas diffusion electrode composite material modified by transition metal.

The copper-based catalyst modified by the transition metal is prepared by a chemical precipitation method through the following steps: 1) Adding an ethanol solution of a transition metal compound into an aqueous solution of a copper compound, adding citric acid as a stabilizer, adding an alkaline aqueous solution into the obtained solution, and stirring;

2) After the reaction is finished, centrifuging, washing and drying the obtained precipitate to obtain a solid powder product;

3) And calcining the obtained solid powder to obtain the transition metal modified copper-based catalyst.

In the above method step 1), the copper compound may be selected from copper sulfate (CuSO) ₄ ) Copper nitrate (CuNO) ₃ ) Copper chloride (CuCl) ₂ ) Copper acetate (Cu (CH) ₃ COO) ₂ ) Copper acetylacetonate (Cu (acac) ₂ ) At least one of the hydrate thereof, specifically CuSO ₄ Hydrates, more particularly CuSO ₄ ·5H ₂ O；

The post-transition metal compound may be selected from tin chloride (SnCl) ₄ ) Indium chloride (InCl) ₃ ) Bismuth chloride (BiCl) ₃ ) Lead chloride (PbCl) ₂ ) At least one of the hydrates thereof, in particular SnCl ₄ Hydrates, more particularly SnCl ₄ ·5H ₂ O；

The molar ratio of the copper compound to the transition metal compound may be from 100:1 to 1:100, preferably from 5:1 to 1:2, and in particular may be 1:1;

according to an embodiment of the invention, the copper compound is CuSO ₄ ·5H ₂ O, the transition metal compound is SnCl ₄ ·5H ₂ O, the molar ratio of the two can be 7:1, 70:1 or 7:2.

The molar ratio of the citric acid to the copper compound is 10:1-1:10, which may be specifically 1:1.

The alkaline aqueous solution is selected from NaOH aqueous solution, KOH aqueous solution, na ₂ CO ₃ Aqueous solution, K ₂ CO ₃ Aqueous solution of NaHCO ₃ Aqueous solution, KHCO ₃ At least one of the aqueous solutions, in particular, may be an aqueous NaOH solution;

the concentration of the alkaline aqueous solution can be 0.01-10M, and can be specifically 2M;

the temperature of the stirring can be 0-100 ℃, and can be 25 ℃;

the stirring time may be 0.2 to 50 hours, and specifically may be 1 to 3 hours.

In the step 2), the rotating speed is 1000-10000rpm, and the time is 1-60min; specifically, the speed is 9000rpm,2min;

the solvent for washing can be deionized water, ethanol, acetone, methanol and mixed solution thereof, and can be specifically deionized water and ethanol;

the drying temperature can be 30-150 ℃, the time can be 1-50h, and the drying time can be 60 ℃ for 12h;

in the step 3), the calcination is performed in an inert atmosphere of argon or nitrogen, and the calcination temperature can be 300-700 ℃, specifically can be in an atmosphere of argon at 500-600 ℃;

the calcination time can be 1-10 hours, and specifically can be 2-5 hours;

the transition metal modified copper-based catalyst/gas diffusion electrode composite material is prepared by a method comprising the following steps: dispersing the copper-based catalyst modified by the transition metal into an organic solvent, adding Nafion D-521 dispersion liquid as a binder, and dripping the obtained dispersion liquid on a gas diffusion layer to obtain the catalyst.

Wherein the organic solvent is selected from at least one of the following: acetone, ethanol, isopropanol, methanol, specifically isopropanol;

the mass fraction of the Nafion D-521 dispersion liquid is 5-20wt%;

the ratio of the Nafion D-521 dispersion liquid to the catalyst is 5-100 mu L to 10mg, such as 50 mu L to 10 mg;

the gas diffusion layer can be carbon fiber paper, carbon fiber woven cloth, non-woven cloth, carbon black paper or PTFE film, and can be specifically carbon fiber paper;

the dosage of the transition metal modified copper-based catalyst can be 0.1-100mg cm ^-2 Specifically, it may be 2mg cm ^-2 。

It is a second object of the present invention to provide an electrochemical catalytic system.

The electrochemical catalytic system comprises the electrode material, a reaction electrolyte and a reaction device; the reaction electrolyte is selected from at least one of the following: KOH aqueous solution, KHCO ₃ Aqueous solution, KCl aqueous solution, naOH aqueous solution and NaHCO aqueous solution ₃ An aqueous solution, an aqueous NaCl solution;

the concentration of the reaction electrolyte may be 0.1 to 10M; specifically, 1M KOH aqueous solution;

the reaction device can be an H-type electrolytic cell, a flow-type electrolytic cell or a membrane electrode electrolytic cell;

the electrode material and the electrochemical catalytic system are used for electrochemical catalytic conversion of CO ₂ The use in synthesizing CO is also within the scope of the present invention.

Furthermore, the inventionAlso provided is an electrochemical catalytic conversion CO ₂ A method for synthesizing CO.

The electrochemical catalytic conversion of CO provided by the invention ₂ A method of synthesizing CO comprising the steps of: by using the electrochemical catalytic system and CO ₂ The raw materials are reacted in an electrolytic cell reaction device to synthesize CO through the action of electrode materials and electrolyte.

In the method, the reaction potential can be-0.3 to-1.5V vs. RHE (-1.3 to-4.0V vs. Ag/AgCl) in an H-type electrolytic cell system or a flow-type electrolytic cell system, and the reaction potential can be 2 to 7V in a membrane electrode electrolytic cell system; specifically, the method can be a flowing type electrolytic cell system, and the reaction potential is between-0.35 and-1.0V vs. RHE;

the reaction time may be from 0.2 to 500 hours, preferably from 1 to 300 hours.

The reaction products include CO, formic acid, hydrogen, mainly CO.

The invention provides a method for preparing the catalyst by CO ₂ A method for synthesizing CO under electrochemical catalysis. The reaction can be efficiently carried out in a flow type electrolytic cell and a membrane electrode electrolytic cell system by taking the copper-based catalyst/gas diffusion electrode composite material modified by transition metal as an electrode material, and the electrode material is CO ₂ An important breakthrough in the field of electrochemical catalytic conversion. In addition, the catalyst disclosed by the invention has excellent recycling performance, and lays a solid foundation for the industrialized development of the catalyst. The method adopts cheap and easily available non-noble metal raw materials for CO ₂ The recycling of the water-soluble polymer has large-scale practical application value, and has profound significance in solving energy crisis and environmental problems.

Drawings

FIG. 1 is a Scanning Electron Microscope (SEM) image of 2.8% Sn-Cu-O;

FIG. 2 is an X-ray diffraction analysis (XRD) pattern of 2.8% Sn-Cu-O;

FIG. 3 is an elemental distribution diagram (EDS Mapping) of 2.8% Sn-Cu-O;

FIG. 4 is an electrochemical reduction of CO to 2.8% Sn-Cu-O ₂ Faraday efficiency plot for CO;

FIG. 5 is an electrochemical reduction of CO to 2.8% Sn-Cu-O ₂ Current density for COAnd (5) a degree graph.

Detailed Description

The invention will be further illustrated with reference to the following specific examples, but the invention is not limited to the following examples. The methods are conventional methods unless otherwise specified. The starting materials are available from published commercial sources unless otherwise specified.

Example 1, preparation and characterization of the catalyst:

take a catalyst with a mass fraction of Sn of 2.8% (2.8% Sn-Cu-O) as an example.

First 20mL SnCl ₄ ·5H ₂ A solution of O (4.0 mmol) in ethanol was added to 140mL of CuSO with vigorous stirring ₄ ·5H ₂ O (4.0 mmol) and citric acid (4.0 mmol). Slowly adding 20mL of NaOH (2M) aqueous solution into the solution under stirring, and vigorously stirring for 1h; then, 60mL of NaOH (2M) aqueous solution was added and stirred for 30min. Centrifugal for 2min at 9000rpm to obtain precipitate, washing with deionized water and ethanol respectively, and drying the precipitate at 60deg.C in a vacuum drying oven for 12 hr. Calcining the obtained solid powder for 2 hours at 600 ℃ under argon atmosphere to obtain the 2.8% Sn-Cu-O catalyst, wherein the mass fraction of the elements is measured by an inductively coupled plasma emission spectrometer. By adjusting SnCl ₄ ·5H ₂ O and CuSO ₄ ·5H ₂ O is added in proportion to respectively obtain CuO, 0.6 percent Sn-Cu-O and 4.0 percent Sn-Cu-O catalysts, and the corresponding SnCl ₄ ·5H ₂ O and CuSO ₄ ·5H ₂ The addition amounts of O are respectively as follows: 4.0mmol CuSO ₄ ·5H ₂ O、0mmol SnCl ₄ ·5H ₂ O(CuO)；4.0mmol CuSO ₄ ·5H ₂ O、0.4mmol SnCl ₄ ·5H ₂ O(0.6％Sn-Cu-O)；4.0mmol CuSO ₄ ·5H ₂ O、8mmol SnCl4·5H ₂ O(4.0％Sn-Cu-O)。

Based on the above method, we also utilized InCl ₃ 、BiCl ₃ 、PbCl ₂ A catalyst of 2.8% in-Cu-O, 2.8% Bi-Cu-O, 2.8% Pb-Cu-O was prepared.

We performed systematic characterization of 2.8% sn-Cu-O catalyst. Scanning Electron Microscope (SEM) images showed that 2.8% sn-Cu-O exhibited a uniform rod-like structure (fig. 1). X-ray diffraction analysis (XRD) showed that Cu was present as divalent copper oxide in the 2.8% Sn-Cu-O catalyst (FIG. 2). Elemental distribution map (EDS Mapping) studies showed that the Cu, sn, O elements were uniformly distributed on the catalyst surface (fig. 3).

The catalyst prepared above: the structure and performance of the 0.6% Sn-Cu-O, 4.0% Sn-Cu-O catalyst, 2.8% in-Cu-O, 2.8% Bi-Cu-O, 2.8% Pb-Cu-O catalyst are similar to those of the 2.8% Sn-Cu-O catalyst.

Example 2 electrochemical catalytic conversion of carbon dioxide:

to prepare the working electrode, 10mg of 2.8% Sn-Cu-O catalyst (prepared in example 1) was first dispersed in 2mL of isopropanol together with 50. Mu.L of Nafion D-521 dispersion (5 wt%) and sonicated for 30min to make the dispersion uniform. Uniformly dripping the dispersion liquid on the surface of the carbon fiber paper with the gas diffusion layer, and standing for 12 hours at room temperature, wherein the loading capacity of each electrode catalyst is 2mg cm ^-2 。

All electrochemical experiments were performed on an electrochemical workstation (CHI 660E, shanghai Chen Hua instruments Co., ltd.). The electrolysis experiment is carried out at 25 ℃, the used electrolysis cell device is a three-electrode flow type electrolysis cell system, and the three electrodes comprise the working electrode, a foam nickel counter electrode and an Ag/AgCl reference electrode, and 3M KCl aqueous solution is added. Prior to the experiment, the reference electrode was calibrated according to literature methods. In the experiment, fumasepFAA-3-PK-130 membrane is used as anion exchange membrane to separate the cathode from the anode, 1M KOH aqueous solution is used as electrolyte, the electrolyte dosage is 30ml and CO is used in each experiment ₂ The flow rate was 20sccm, and electrolysis was performed. Collecting gas product with gas bag, analyzing with gas chromatograph (GC, HP 4890D), and performing nuclear magnetic resonance on liquid product ¹ H NMR, bruker Avance III, 400, HD).

Electrocatalytic CO under different catalytic conditions ₂ The test results of the reaction are shown in FIGS. 4 and 5. As can be seen from the graph, the catalytic system of the invention maintains excellent selectivity (Faraday efficiency is more than 90%) and high current density for CO at a wide potential, and the current density meets the industrial current density requirement (> 100mA cm) when the potential is-0.6V vs. RHE ^-2 )。

EXAMPLE 3 catalyst stability Studies

The reaction was continued at a potential of-0.8V vs RHE for 300 hours, and the long-term stability of 2.8% Sn-Cu-O was evaluated. The current density and the Faraday efficiency of CO are not changed obviously, which indicates that the catalyst has good electrochemical stability and potential industrial value.

Claims

1. A preparation method of a transition metal modified copper-based catalyst is prepared by a chemical precipitation method and comprises the following steps:

1) Adding an ethanol solution of a transition metal compound into an aqueous solution of a copper compound, adding citric acid as a stabilizer, adding an alkaline aqueous solution into the obtained solution, and stirring;

3) Calcining the obtained solid powder to obtain the copper-based catalyst modified by the transition metal;

in the step 1), the copper compound is at least one selected from copper sulfate, copper nitrate, copper chloride, copper acetate, copper acetylacetonate and hydrates thereof;

the transition metal compound is at least one selected from tin chloride, indium chloride, bismuth chloride, lead chloride and hydrates thereof;

the mass ratio of the copper compound to the transition metal compound is 5:1-1:2;

the molar ratio of the citric acid to the copper compound is 10:1-1:10;

in the step 3), the calcination is carried out in an inert atmosphere of argon or nitrogen, and the temperature of the calcination is 300-700 DEG C ^o C, performing operation; the calcination time is 1-10 h.

2. The method of manufacturing according to claim 1, characterized in that: in the step (1) of the above-mentioned process,

the alkaline aqueous solution is selected from NaOH aqueous solution, KOH aqueous solution and Na ₂ CO ₃ Aqueous solution, K ₂ CO ₃ Aqueous solution of NaHCO ₃ Aqueous solution, KHCO ₃ At least one of the aqueous solutions;

the concentration of the alkaline aqueous solution is 0.01-10M;

the stirring temperature is 0-100 ^o C；

The stirring time is 0.2-50 h;

or, in the step 2), the rotational speed in the centrifugation step is 1000-10000 RPM; the time is 1-60min;

the washing solvent is at least one selected from deionized water, ethanol, acetone, methanol and mixed solutions thereof;

the drying temperature is 30-150 DEG C ^o C, time is 1-50 h.

3. A post-transition metal modified copper-based catalyst prepared by the method of claim 1 or 2.

4. An electrode material which is an electrode composite material composed of the post-transition metal-modified copper-based catalyst of claim 3 and a gas diffusion layer.

5. The electrode material according to claim 4, wherein: the electrode material is prepared by a method comprising the following steps: dispersing the copper-based catalyst modified by the transition metal into an organic solvent, adding Nafion D-521 dispersion liquid as a binder, and then dripping the obtained dispersion liquid on a gas diffusion layer to obtain the catalyst.

6. The electrode material according to claim 5, wherein: the organic solvent is selected from at least one of the following: acetone, ethanol, isopropanol, methanol;

the mass fraction of the Nafion D-521 dispersion liquid is 5-20wt%;

the ratio of the Nafion D-521 dispersion liquid to the catalyst is 5-100 mu L:10 mg;

the gas diffusion layer is carbon fiber paper, carbon fiber woven cloth, non-woven cloth, carbon black paper or PTFE film;

the dosage of the catalyst is 0.1-100mg cm ^-2 。

7. An electrochemical catalytic system comprising the electrode material of claim 5 or 6, a reaction electrolyte, and a reaction device.

8. The electrochemical catalytic system of claim 7, wherein: the reaction electrolyte is selected from at least one of the following: KOH aqueous solution, KHCO ₃ Aqueous solution, KCl aqueous solution, naOH aqueous solution and NaHCO aqueous solution ₃ An aqueous solution, an aqueous NaCl solution;

the concentration of the reaction electrolyte is 0.1-10M;

the reaction device is an H-type electrolytic cell, a flow-type electrolytic cell or a membrane electrode electrolytic cell.

9. Use of an electrode material according to any one of claims 4 to 6 or an electrochemical catalytic system according to claim 7 or 8 for the electrochemical catalytic conversion of carbon dioxide to carbon monoxide.

10. A method for synthesizing carbon monoxide by electrochemical catalytic conversion of carbon dioxide is characterized by comprising the following steps: the electrochemical catalytic system as claimed in claim 7 or 8 is used for synthesizing carbon monoxide by taking carbon dioxide as a raw material and reacting the carbon monoxide with electrolyte in an electrolytic cell reaction device under the action of electrode materials.

11. The method according to claim 10, wherein: the reaction potential is-0.3 to-1.5V vs. RHE or-1.3 to-4.0V vs. Ag/AgCl in the H-type electrolytic cell and the flowing type electrolytic cell system, and the reaction potential is 2 to 7V in the membrane electrode electrolytic cell system; the reaction time is 0.2-500 and h.