WO2023082414A1

WO2023082414A1 - Carbon dioxide energy storage system driven by new energy and electric energy, and energy storage method

Info

Publication number: WO2023082414A1
Application number: PCT/CN2021/138544
Authority: WO
Inventors: 夏霖
Original assignee: 深圳先进技术研究院
Priority date: 2021-11-09
Filing date: 2021-12-15
Publication date: 2023-05-19
Also published as: CN113943942B; CN113943942A

Abstract

Provided in the present invention are a system and method for energy storage by means of the electrochemical catalytic reduction of carbon dioxide under the driving of new energy and electric energy. A copper-based catalyst is modified by sodium polybutadiene sulfonate and used for preparing an electrochemical catalytic electrode, and the current density, the temperature range, and the pH value of an electrolyte in the electrochemical catalysis process are optimized, such that the efficiency of the electrochemical catalytic reduction of carbon dioxide and the Faraday efficiency of methane are further improved, the loss of input energy is reduced, and the efficient storage of electric energy is realized.

Description

Carbon dioxide energy storage system and energy storage method driven by new energy electric energy

technical field

The invention relates to the technical field of electric energy storage, in particular to a carbon dioxide reduction energy storage method driven by new energy electric energy.

Background technique

General Secretary Xi Jinping proposed at the general debate of the 75th session of the United Nations General Assembly that "China will increase its nationally determined contributions and adopt more powerful policies and measures. neutralize". Therefore, doing a good job in carbon peaking and carbon neutrality is my country's national policy to deal with climate change, and it is an internal demand for my country's economic structure transformation and upgrading and implementation of sustainable development. Promoting carbon peaking and achieving carbon neutrality is the key to further fighting the tough battle against pollution and promoting high-quality development.

In terms of sources of carbon emissions, carbon dioxide emissions from energy consumption account for nearly 90% of my country's total carbon dioxide emissions and nearly 80% of net greenhouse gas emissions. Therefore, the green transition in the energy sector is crucial to the realization of the goal of carbon neutrality. In the field of energy, carbon emissions from the power sector account for about 40%, and the proportion is increasing year by year. Under the general trend of electrification, the zero-carbon development of the power system will be a key to achieving the "30·60 goal". Therefore, in December 2020, China further promised at the Climate Ambition Summit: by 2030, non-fossil energy will account for about 25% of China's primary energy consumption, and the total installed capacity of wind power and solar power will reach more than 1.2 billion kilowatts. As a key technology supporting the development of renewable energy, energy storage will usher in a new stage of leapfrog development.

Electrochemical catalytic processes are considered to be a reliable solution for the efficient integration of renewable resources such as wind and solar energy into the current carbon-neutral energy mix. The scheme aims to use electrocatalysts combined with carbon dioxide, activated by electrical energy, to reduce carbon dioxide into fuels such as methanol, ethanol and methane, and store these fuels until they are reconverted during periods of high power consumption. Compared with methanol and ethanol, it is easier to transport, has higher energy storage density per unit mass, and is more compatible with existing fuel storage equipment. An important carrier fuel and widely used.

There have been a large number of studies on the use of electrocatalysts for the reduction of carbon dioxide to produce methane for electrical energy storage. Nickel-based catalysts are widely used in the reduction of carbon dioxide to methane due to their low cost and easy availability. However, even at low temperatures, nickel catalysts may be deactivated due to sintering of nickel particles, formation of mobile nickel carbonylenes, or formation of carbon deposits. In addition, active metals Rh, Co, Fe, etc. have also been reported as effective catalysts for carbon dioxide reduction to methane, but the high cost of these catalysts limits their industrial applications.

Compared with the above-mentioned catalysts, copper-based catalysts are cheaper and are the most effective catalysts for reducing carbon dioxide to hydrocarbons. They have advantages in improving the selectivity of carbon dioxide conversion products, and are also the most effective for carbon dioxide methanation and industrialized electric energy storage. means. By modifying the copper-based catalyst with chemical small molecules, not only the reaction rate can be increased, but also the formation of methane on the copper-based surface can be further promoted by suppressing the hydrogen evolution reaction.

However, for the use of copper-based catalysts, the current research problems are the key parameters of energy storage efficiency in the process of electrochemical reduction of carbon dioxide energy storage, that is, insufficient Faraday efficiency and large energy input loss. Because the use of traditional chemical small molecules to modify copper electrodes can increase the conversion efficiency of carbon dioxide, but it is easy to desorb from the copper electrodes during use and then be removed with the liquid flow in the electrolytic cell, resulting in loss of input energy. Faraday is inefficient.

In related applications, the inventors of the present application proposed that copper-based catalysts be modified with polymers having proton-conductive side chains and electron-conductive main chains, which can improve the Faradaic efficiency and catalytic efficiency of existing copper-based catalysts and reduce the cost of input energy. Loss, to achieve efficient storage of electrical energy.

In the course of further research, we found that using this polymer-modified copper-based catalyst for electrochemical catalytic carbon dioxide reduction energy storage, the conditions in the reduction process also have a great impact on the conversion efficiency of methane, therefore, further optimized New energy-driven electrochemical catalytic carbon dioxide reduction energy storage method.

Technical solutions

The technical problem to be solved by the present invention is to provide a new energy-driven electrochemical catalytic carbon dioxide reduction energy storage system and energy storage method, using a polymer-modified copper-based catalyst with a proton-conductive side chain and an electronic-conductive main chain to prepare Electrochemical catalytic electrodes, and optimize the current density, temperature range and pH value of the electrolyte in the electrochemical catalytic process, further improve the efficiency of electrochemical catalytic carbon dioxide reduction and the Faradaic efficiency of methane, reduce the loss of input energy, and achieve high efficiency of electric energy storage.

Based on this, the present invention provides a new energy-driven electrochemical catalytic carbon dioxide reduction energy storage system, as the electrochemical catalytic electrode, electrolyte and anode of the cathode, the electrochemical catalytic electrode has a modified polymer, and the modified polymer It is a polymer with proton conductive side chain and electron conductive main chain.

Wherein, the anode can be an inert metal electrode or a carbon electrode.

Wherein, the electrolyte solution may be KHCO ₃ , NaHCO ₃ , and the concentration is between 0.05M-2M.

The present invention also provides a new energy-driven electrochemical catalytic carbon dioxide reduction energy storage method, which includes:

The first step is to pass the carbon dioxide gas source into the system electrolyte until saturated;

The second step is to use new energy to provide electricity to the above-mentioned carbon dioxide reduction energy storage system for electrochemical catalytic reaction;

The third step is to export and store the generated methane fuel for subsequent energy use.

Wherein, in the second step, the pH range of the electrolyte is 4.8-6.8.

Wherein, in the second step, the reaction temperature ranges from 25°C to 65°C.

Wherein, in the second step, the applied catalytic potential ranges from -0.82V to 1.02V.

Beneficial effect

The invention provides an electrochemical catalytic carbon dioxide reduction energy storage system and an energy storage method driven by new energy electric energy. The copper-based catalyst is modified by a polymer having a proton conductive side chain and an electronic conductive main chain to prepare an electrochemical catalytic electrode. And optimize the applied catalytic potential, temperature range and pH value of the electrolyte in the electrochemical catalysis process, further improve the efficiency of electrochemical catalysis for carbon dioxide reduction and the Faraday efficiency of methane, reduce the loss of input energy, and realize the efficient storage of electrical energy as a chemical able.

Description of drawings

Figure 1 Effects of different potentials on Faraday conversion efficiency and catalytic efficiency;

Fig. 2 Effects of different electrolyte pH values on faradaic conversion efficiency and catalytic efficiency;

Figure 3 In the electrolyte system with different electrolyte pH, the polymer/copper catalytic electrode maintains the maximum active current density percentage within 10 hours of continuous operation;

Fig. 4 Effects of different reaction temperatures on faradaic conversion efficiency and catalytic efficiency.

Detailed ways

Copper-based catalysts are modified by polymer modification groups with special structures. The hydrophilicity and hydrophobicity of polymer side chains affect the protonation process of _CO2 reduction reaction and the diffusion process of _CO2 on the electrode surface, both of which will affect the efficiency of the reaction. and further regulation of product production.

First, the chemical properties of the polymer polymer side chains provided by the present invention regulate the reduction of _CO2 on the Cu surface, since the polymers used contain proton-conducting side chains, such as those containing sulfonic acid groups or containing phosphoric acid groups The side chain can effectively increase the concentration of CO radicals on the surface of the Cu electrode and the surface pH value in the reaction system. While regulating the catalytic activity, it also significantly regulates the formation of products, making the entire reaction easy to form methane.

In addition, the electronically conductive main chain of the polymer provided by the present invention has more than one conjugated group, and the conjugated group can be an alkenyl group, an aromatic conjugated group, etc., which can significantly reduce the electrode interface impedance and improve the conversion into methane Faraday efficiency and catalytic current density (catalytic efficiency).

Based on the above principles, the present invention provides a copper-based catalyst for electrochemically catalytic carbon dioxide reduction energy storage driven by new energy. The copper-based catalyst is obtained by electroplating copper nanoparticles and modified polymers. The modified polymer The polymer is a polymer with a proton-conducting side chain and an electron-conducting main chain.

The electron-conductive main chain has one or more conjugated groups, and the conjugated groups are preferably butadienyl groups.

The proton conductive side chain is a side chain of a sulfonic acid group.

The polymer is further preferably polystyrene sulfonic acid (PSS), polybutadiene sulfonic acid, polybutadiene sulfonic acid salt, polyaniline with camphorsulfonic acid as a dopant, most preferably polybutadiene sulfonic acid Sodium acid.

The copper-based catalyst can be prepared as a coating and coated on the electrode substrate to prepare an electrochemical catalytic electrode. The electrode substrate can be selected from carbon material electrodes, carbon material composite electrodes, noble metal electrodes, stainless steel electrodes, copper electrodes, iron electrodes, etc. .

The carbon material electrode can further be a graphite electrode, a carbon fiber electrode, a carbon paper electrode (gas diffusion electrode), a graphene electrode, a carbon nanotube electrode, a diamond electrode, and the like. Further preferred are carbon fiber electrodes, carbon paper electrodes (gas diffusion electrodes), graphene electrodes, and carbon nanotube electrodes.

The noble metal electrode may further be selected from gold, silver, platinum and the like.

The coating thickness is preferably 10 μm-20 μm, further preferably 12 μm-16 μm, and most preferably 12 μm. Through research, we found that when the coating thickness is lower than 10 μm or higher than 20 μm, the faradaic efficiency of methane will be significantly reduced, and the conversion rate is almost less than 50%. And the maximum catalytic current density is also significantly reduced, affecting the reduction efficiency of carbon dioxide.

The present invention adopts an in-situ co-deposition method to prepare an electrochemical catalytic electrode, which can deposit polymers onto copper electrodes, realize polymer molecules remaining on the electrode surface, and avoid the problem of desorption from copper electrodes.

The present invention also provides a preparation method for the above-mentioned electrochemical catalytic electrode, which adopts an in-situ co-deposition method, specifically comprising:

The first step is the preparation of the electroplating solution, the electroplating solution includes CuSO ₄ solution, the above-mentioned modified polymer, Na ₂ SO ₄ , H ₂ SO ₄ , and the above-mentioned components are mixed together in proportion;

In the second step, the electrode base material is put into the above-mentioned electroplating solution, and electroplating is performed by an electroplating method.

The concentration of the CuSO ₄ solution is preferably 1 mM-10 mM, more preferably 3 mM.

The concentration of the modifying polymer is preferably 1 μM-100 μM, more preferably 10 μM-100 μM, even more preferably 10 μM-20 μM.

The concentration of the Na ₂ SO ₄ solution is preferably 0.05M-0.1M, more preferably 0.1M.

The concentration of the H ₂ SO ₄ solution is preferably 0.3M-0.5M, more preferably 0.5M.

The current density in the second step is preferably (-2mA/cm ² )-(-6mA/cm ² ), more preferably (-3mA/cm ² ).

The present invention also provides a new energy-driven electrochemical catalytic carbon dioxide reduction energy storage system, which includes: the above-mentioned electrochemical catalytic electrode as a cathode, an electrolyte, an anode and an electrolytic cell.

The anode can be an inert metal electrode or a carbon electrode.

The electrolyte solution can be KHCO ₃ , NaHCO _{3 ,} etc., and the concentration is between 0.05M-2M, more preferably between 0.05M-1M.

In the second step, the pH value of the electrolyte is 4.8-6.8, and the pH of the electrolyte is lower than 7 to ensure that after _CO2 is reduced to a CO* free radical intermediate, there are enough proton sources in the system to provide For intermediates, protonation occurs to further generate methane, so in theory, the lower the pH of the system, the easier it is for the CO* radical intermediates in the system to undergo protonation. However, too low electrolyte pH will affect the stability of Cu catalyst, so an optimized pH range is needed to ensure the stability of proton donor and catalyst at the same time.

In the second step, the reaction temperature is a given temperature range of 25°C-65°C, and the influence of temperature on the Faraday efficiency and maximum catalytic current (catalytic efficiency) of the catalytic system is mainly reflected in two aspects, 1) thermodynamics affects catalyst activity The activity of the center promotes the combination and dissociation speed of the catalyst and _CO2 and the catalytic turnover rate; 2) improves the solubility and mass transfer rate of _CO2 in the system, and from the consideration of green and low-carbon energy consumption, room temperature is further preferred.

In the second step, the applied catalytic potential ranges from -0.82V to 1.02V. Usually, the catalytic potential applied by electrochemistry will significantly affect the product distribution of electroreduction catalysis, thus affecting the product ratio of catalytic reduction to produce methane And the ratio of by-products, so as to the faradaic efficiency and catalytic efficiency of methane production, the present invention found that within this potential range, the faradaic efficiency of methane exceeded, which greatly improved the accuracy of reducing carbon dioxide into methane.

The implementation of the present invention will be described in detail below with examples and accompanying drawings, so as to fully understand and implement the process of how to apply technical means to solve technical problems and achieve technical effects in the present invention.

Embodiment 1 Preparation of Modified Copper Electrode

Pour 3mM CuSO ₄ solution, 20μM sodium polybutadiene sulfonate, 0.1mM Na ₂ SO ₄ and 0.5mM H ₂ SO ₄ into the electroplating container, use in-situ co-deposition method, stir and mix evenly to obtain electroplating liquid.

The graphite electrode substrate was put into the above electroplating solution, and electroplating was performed with a deposition current density of -3mA/cm ² , a total deposition electricity of 2.5C/cm ² , and a prepared catalyst layer with a thickness of 12 μM.

Faraday efficiency refers to the percentage of the actual product and the amount of the theoretical product. The amount of the theoretical product is the reduction electrons generated by the catalytic electrode using electric energy. The number of electron transfers in the catalytic reaction is calculated, which is theoretically used to reduce CO ₂ The total amount of product that can be produced. The content of the product was detected by gas chromatography.

The effect of applying different catalytic potentials on the faradaic conversion efficiency of methane and the catalytic efficiency of carbon dioxide reduction

The modified copper electrode prepared in Example 1 was used as the cathode, the inert metal platinum electrode was used as the anode, and the 0.1M sodium bicarbonate solution saturated with _CO2 was used as the electrolyte, and the pH value of the electrolyte was adjusted to 6.8 to construct a carbon dioxide reduction energy storage system , put the _CO2 gas source into the system electrolyte to saturation, use the solar power supply system to supply power, apply the working voltage to the cathode (refer to the silver/silver chloride reference electrode), and carry out the electrocatalytic reaction at room temperature to investigate different work Voltage, electrochemical catalytic reaction effect, the results are shown in Table 1 and Figure 1.

Table 1 Effect of different potentials on faradaic conversion efficiency and catalytic efficiency

It can be seen from Table 1 and Figure 1 that when the applied potential is -0.42V, the main product of the catalytic system is CO, and the Faradaic efficiency can reach 85%, because at this potential, the wettability of the electrode surface is insufficient, which is not conducive to The proton transfer on the surface, the CO* free radical intermediate produced by the catalytic reduction of carbon dioxide is more likely to dissociate rapidly from the catalytic site and escape to the electrolyte phase as CO. Further lowering the catalytic potential can significantly affect the dissociation and escape of CO* radical intermediates on the surface of the catalytic electrode. When the catalytic potential reaches -0.82V, the faradaic efficiency of the system for producing methane is the largest, and the production of CO is significantly suppressed. Although reducing the catalytic potential can also inhibit the production of CO, too low a catalytic potential will promote the side reaction of hydrogen evolution on the electrode surface, which also affects the faradaic efficiency and catalytic efficiency of catalytic methanation. When the applied potential is reduced to -1.3V, Although the faradaic efficiency of methane is still the highest, the faradaic efficiency of hydrogen is also significantly increased, while the maximum catalytic current density is significantly reduced. After verification and analysis, when the applied potential is -0.82V--1.02V, it can ensure a high faradaic conversion efficiency of methane, and at the same time, the maximum catalytic current density is also large, maintaining a high catalytic efficiency.

Effects of different pH ranges on the faradaic conversion efficiency of methane and the catalytic efficiency of carbon dioxide reduction

Using the modified copper electrode and energy storage system prepared in Example 1, using the same carbon dioxide reduction conversion energy storage method as above, the working voltage applied to the cathode is -0.82V, and the electrocatalytic reaction is carried out at room temperature, and different electrolytes are selected. The pH ranges were compared, and the results are shown in Table 2 and Figure 2.

Table 2 Effects of pH values of different electrolytes on faradaic conversion efficiency and catalytic efficiency

Previous studies have found that the use of alkaline electrolytes is believed to favor ethylene production by reducing the energy barrier for _CO2 activation, promoting cc coupling and inhibiting _H2 production (Dinh, C.-T. et al. _CO2 Electroreduction to ethylene via hydroxide-mediated

copper catalysis at an abrupt interface. Science 360, 783–787 (2018). The acidic electrolyte will ensure that after CO ₂ is reduced to CO* free radical intermediates, there will be enough proton sources in the system to supply the intermediates, and protonation will further generate methane. Therefore, the lower the pH of the system, the lower the system The CO* radical intermediate in is more prone to protonation. However, too low electrolyte pH will affect the stability of Cu catalyst, so an optimized pH range is needed to ensure the stability of proton donor and catalyst at the same time. Therefore, in this patent’s catalytic system for methanogenicity, in order to study the beneficial effect of pH, a series of electrolytes with a pH range of 2.8–7.8 were used for _CO2 catalytic reduction tests. The catalytic performance in different pH electrolyte systems is plotted in Table 2 and Fig. 2. From the data in the table and the figure, it can be seen that when the pH of the system is a slightly alkaline environment of 7.8, the faradaic efficiency of the system to catalyze methane production is significantly reduced, the production of by-product CO is significantly increased, and the overall catalytic efficiency is also significantly improved. reduce. In the range of pH 2.8–6.8, the side reaction of hydrogen evolution in the catalytic system is suppressed as the pH increases, and the faradaic efficiency of CO by-products is suppressed as the pH decreases. Due to the balance of these two factors, It can be seen that the faradaic efficiency of methanogenesis reaches the highest at pH 6.8. Although the catalytic efficiency of the catalytic system, that is, the maximum catalytic current density, increases significantly with the decrease of pH, but the more acidic pH has a significant impact on the stability of the copper-based catalyst. Considering comprehensively, in the pH range of 4.8-6.8, the faradaic efficiency of methane and the catalytic reduction efficiency of carbon dioxide are both high, which not only meets the higher catalytic reduction efficiency, but also meets the requirement of a single product.

Figure 3 shows the activity retention percentage of the polymer/copper catalytic electrode within 10 hours of continuous operation in the electrolyte system of different pH, that is, the maximum catalytic current density after the continuous operation of the reaction for 10 hours and the initial maximum catalytic current density Ratio, used to indicate the stability of the catalyst at different pH, as shown in the figure, in the strong acidic environment of pH 2.8, the stability of the copper-based catalyst only maintained the initial catalytic activity after 10 hours of continuous work 48% of its activity, while in the ph 6.8 electrolyte environment, its activity remained above 77%.

Effects of different electrocatalytic reaction temperature ranges on the faradaic conversion efficiency of methane and the catalytic efficiency of carbon dioxide reduction

Using the modified copper electrode and energy storage system prepared in Example 1, using the same carbon dioxide reduction conversion energy storage method as above, the working voltage applied to the cathode is -0.82V, the pH value of the electrolyte is 6.8, and different electrocatalytic reactions are selected. The temperature is compared, and the results are shown in Table 3 and Figure 4.

Table 3 Effects of Different Reaction Temperatures on Faradaic Conversion Efficiency and Catalytic Efficiency

It can be seen from Table 3 and Figure 4 that the maximum catalytic current density (catalytic efficiency) of the catalytic system increases with the increase of temperature in the range of 5–85°C, and the temperature has a faradaic efficiency and maximum catalytic current (catalytic efficiency) of the catalytic system. The impact of CO2 is mainly reflected in two aspects, 1) thermodynamics affects the activity of the active center of the catalyst, and promotes the combination and dissociation speed of the catalyst and CO ₂ as well as the catalytic turnover rate; 2) improves the solubility and mass transfer rate of CO ₂ in the system. In addition, it can be seen from the figure that the methanogenic faradaic efficiency of the catalytic system is significantly lower than 5°C, and remains above 90% at other temperatures. However, as the temperature is higher than 45°C, the hydrogen evolution side reaction of the catalytic system also decreases. Therefore, the faradaic efficiency of methane production is also slightly reduced. Finally, from the perspective of practical application, considering the two aspects of carbon-neutral _CO2 conversion and energy storage at the same time, it should be combined with the actual scene to find the balance between catalytic efficiency, electricity efficiency, and system energy consumption, preferably at 25°C-65°C The reaction range, most preferably at room temperature, can minimize energy consumption while ensuring Faraday efficiency and catalytic efficiency.

All of the above-mentioned primary implementations of this intellectual property rights are not intended to limit other forms of implementations of this new product and/or new method. Those skilled in the art will, with this important information, modify the above to achieve a similar implementation. However, all modifications or alterations to the new product based on the present invention belong to reserved rights.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention to other forms. Any skilled person who is familiar with this profession may use the technical content disclosed above to change or modify the equivalent of equivalent changes. Example. However, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims

A carbon dioxide energy storage system driven by new energy electric energy, characterized in that it includes: an electrochemical catalytic electrode as a cathode, an electrolyte, and an anode, the electrochemical catalytic electrode has a modified polymer, and the modified polymer has a proton Polymers with conductive side chains and electronically conductive backbones.
The carbon dioxide energy storage system driven by new energy electric energy according to claim 1, wherein the anode is an inert metal electrode or a carbon electrode.
The carbon dioxide energy storage system driven by new energy electric energy according to claim 1 or 2, characterized in that: the electrolyte is KOH or NaHCO 3 with a concentration of 0.05M-2M.
An electrochemical catalytic carbon dioxide reduction energy storage method driven by new energy electric energy, characterized in that it includes:

The first step is to pass the carbon dioxide gas source into the system electrolyte until saturated;

The second step is to use new energy to provide electricity to the carbon dioxide energy storage system described in any one of claims 1 to 3, and perform electrochemical catalytic reactions;

The third step is to export and store the generated methane fuel for subsequent energy use.
The electrochemical catalytic carbon dioxide reduction energy storage method driven by new energy electric energy according to claim 4, characterized in that: in the second step, the pH value of the electrolyte is in the range of 4.8-6.8.
The electrochemical catalytic carbon dioxide reduction energy storage method driven by new energy electric energy according to claim 4 or 5, characterized in that in the second step, the reaction temperature ranges from 25°C to 65°C.
The electrochemical catalytic carbon dioxide reduction energy storage method driven by new energy electric energy according to claim 4 or 5, characterized in that in the second step, the applied catalytic potential ranges from -0.82V to 1.02V.
The electrochemical catalytic carbon dioxide reduction energy storage method driven by new energy electric energy according to claim 4 or 2, characterized in that: the new energy is photovoltaic or wind energy.