Composite bismuth-based catalyst and method as well as application and system of composite bismuth-based catalyst in emission reduction of thermal power plant

Abstract

The invention discloses a composite bismuth-based catalyst, a method and an application and system in emission reduction of a thermal power plant, and belongs to the technical field of electrochemistry and catalysts.The method comprises the steps that copper salt, tin salt and bismuth salt are mixed in an organic solvent, then epoxypropane and deionized water are added, and after aging treatment and vacuum drying, a precursor is obtained; and placing the precursor in a cathode region of a standard three-electrode gas diffusion flow electrolytic tank, and carrying out reduction reaction to convert the precursor into the composite bismuth-based catalyst in situ. Based on the in-situ absorption and conversion technology, the integrated carbon dioxide electroreduction system is constructed, multiple links of carbon dioxide absorption, electrolyte preparation, electroreduction reaction and product collection are integrated, and automatic control from carbon dioxide emission to resource utilization is achieved. By recycling the waste residue calcium carbonate and unreacted lime in the industrial three wastes, the problem of treatment of the desulfurization waste residue of the thermal power plant is solved, and the dual purposes of recycling of carbon resources, energy conservation and emission reduction are achieved.

Description

Technical Field

[0001] This invention belongs to the field of electrochemistry and catalyst technology, specifically relating to composite bismuth-based catalysts and methods, and their application and systems in emission reduction in thermal power plants. Background Technology

[0002] With the acceleration of global industrialization, energy demand is increasing daily. Thermal power generation, as one of the main methods of electricity supply, has also led to a surge in carbon dioxide emissions, posing a serious challenge to global climate change. As a major component of greenhouse gases, the large-scale emission of carbon dioxide exacerbates the greenhouse effect, leading to a series of environmental problems such as rising global temperatures and frequent extreme weather events. Therefore, developing efficient and economical carbon dioxide emission reduction technologies has become a current international research hotspot and urgent task. Electrochemical reduction, as a highly efficient and clean method for carbon dioxide conversion, has promising applications.

[0003] Among numerous emission reduction technologies, electroreduction of carbon dioxide (COD) has attracted significant attention due to its ability to convert COD into high-value-added chemicals or fuels, such as methanol, ethanol, and carbon monoxide. This technology not only helps reduce atmospheric COD concentration but also enables the recycling of carbon resources, playing a crucial role in promoting energy structure transformation and sustainable development. However, the key to COD electroreduction technology lies in the selection and design of the catalyst. An ideal catalyst should possess characteristics such as high activity, high selectivity, good stability, and low cost to ensure efficient conversion of COD into the target product during the electroreduction process, while minimizing byproduct formation and improving energy utilization efficiency. Currently, a wide variety of COD electroreduction catalysts have been reported, including metal catalysts, metal oxide catalysts, and carbon-based catalysts. Although these catalysts have demonstrated potential for COD electroreduction to some extent, they still suffer from problems such as insufficient activity, poor selectivity, poor stability, or high preparation costs, limiting their application in actual industrial production.

[0004] Therefore, to address the shortcomings of existing technologies, it is necessary to find a method for the preparation and application of an electroreduction catalyst for carbon dioxide emission reduction in thermal power plants. This would improve the activity and selectivity of carbon dioxide electroreduction while maintaining good stability, providing a practical technical solution for achieving efficient emission reduction in thermal power plants. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a composite bismuth-based catalyst and method, and its application and system in emission reduction in thermal power plants, so as to solve the technical problems of high processing cost, insufficient catalyst activity, poor selectivity, poor stability and difficulty in treating the large amount of solid waste generated by desulfurization in thermal power plants.

[0006] To achieve the above objectives, the present invention employs the following technical solution: This invention discloses a method for preparing a composite bismuth-based catalyst, comprising the following steps: Copper salt, tin salt and bismuth salt are mixed in an organic solvent, and then propylene oxide and deionized water are added. After aging and vacuum drying, a precursor is obtained. The precursor is placed in the cathode region of a standard three-electrode gas diffusion flow electrolytic cell, and after in-situ reduction reaction, the precursor is converted into a composite bismuth-based catalyst in situ.

[0007] Preferably, the ratio of copper salt, tin salt, bismuth salt, organic solvent, propylene oxide and deionized water is (0.2-0.5) g : (0.5-1.0) g : (5.2-10.5) g : (10-20) mL : (10-20) mL : (2-5) mL; The copper salt is CuCl2·2H2O; the tin salt is SnCl2·2H2O; the bismuth salt is Bi(NO3)3·5H2O; and the organic solvent is isopropanol.

[0008] Preferably, the aging treatment time is 12-24 hours, and the vacuum drying temperature is 50-70℃ for 12-24 hours; The conditions for the reduction reaction include: placing the precursor in the cathode region in a standard three-electrode gas diffusion flow electrolytic cell, introducing CO2 into the gas flow channel, and simultaneously introducing KHCO3 electrolyte solution into the cathode and anode regions. After in-situ reduction reaction under constant current density, the precursor is converted into a composite bismuth-based catalyst in situ.

[0009] More preferably, the CO2 flow rate is 10-20 mL / min; the molar concentration of the KHCO3 electrolyte solution is 0.5-1.0 mol / L; and the constant current density is 300-500 mA·cm⁻¹. -2 The in-situ reduction reaction takes 0.5-1.0 hours.

[0010] The present invention also discloses a composite bismuth-based catalyst, which is prepared by the above-described method for preparing composite bismuth-based catalysts.

[0011] The present invention also discloses the application of the composite bismuth-based catalyst prepared by the above-mentioned method in emission reduction in thermal power plants.

[0012] Preferably, the composite bismuth-based catalyst prepared by the method of preparing composite bismuth-based catalyst is ultrasonically dispersed in an organic solvent and sprayed onto the cathode gas diffusion electrode. After drying, it is used to electroreduc carbon dioxide in the flue gas emitted by thermal power plants to produce formate. The organic solvent is isopropanol and the drying temperature is 50-70℃.

[0013] This invention also discloses a system for the electroreduction of carbon dioxide to formate for emission reduction in thermal power plants, comprising: Flue gas absorption device, used to mix slurry containing limestone or lime with flue gas emitted from thermal power plants, and absorb carbon dioxide in the flue gas emitted from thermal power plants; A slurry circulation and sedimentation device is used to circulate slurry and settle solid substances. A slurry filtration and feeding device is used to filter slurry and provide raw materials for an electroreduction reaction. An electroreduction reactor is used to receive raw materials and carry out an electroreduction reaction. Product collection and processing device, used to collect the products of electroreduction reaction; System monitoring and maintenance devices are used to monitor the system's operating status and parameters; The electroreduction reaction apparatus includes a gas diffusion flow electrolytic cell, which has an anode region and a cathode region. A gas diffusion electrode is installed in the cathode region, and the gas diffusion electrode is loaded with the composite bismuth-based catalyst prepared by the above-mentioned method.

[0014] Preferably, the flue gas absorption device is a countercurrent absorption tower; The slurry circulation and sedimentation device includes: a slurry circulation pump connected to the countercurrent absorption tower, a sedimentation tank connected to the slurry circulation pump via a branch pipeline, and a sediment circulation pump connected to the sedimentation tank; The slurry filtration and feeding device includes: an electric stack feeding pump and a filter connected in sequence to the outlet end of the sedimentation tank; The electroreduction reactor includes: an electroreduction carbon dioxide fuel cell stack and a programmable high-power power supply for regulating the power output; The anode region is the oxygen absorption reaction zone, and the anode electrode is an IrO2 / C electrode.

[0015] More preferably, the slurry circulation pump and the countercurrent absorption tower form a circulation loop; The sedimentation tank and the sediment circulation pump form a circulation loop; The clean carbon dioxide slurry in the sedimentation tank is fed into the electroreduction carbon dioxide stack via the stack feed pump to provide raw materials for the electroreduction reaction.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method for preparing a composite bismuth-based catalyst. Copper, tin, and bismuth salts are uniformly dispersed in isopropanol to form a sol system. The epoxy groups of propylene oxide undergo coordination crosslinking with metal ions to form a gel with a three-dimensional network structure. During aging, the metal ions continuously hydrolyze and condense, forming a stable mesoporous framework. After vacuum drying to remove the solvent, a precursor with a high specific surface area is obtained. In the cathode region of the electrolytic cell, the precursor accepts electrons in a carbon dioxide-saturated electrolyte, reducing the metal oxide to nano-metal particles. Simultaneously, the bismuth component forms a bismuth oxide interface layer rich in oxygen vacancies. This process allows the active component to grow directly on the conductive framework, forming a stable multiphase catalytic interface. Traditional single-metal catalysts can only provide a single active site and cannot achieve the synergistic transformation of multiple intermediates. Although binary alloy systems can improve the electronic structure, they lack precise control over the reaction pathway. This invention, through the combination of ternary metal synergy and mesoporous structure, forms a relay catalytic effect in the carbon dioxide adsorption, electron transfer, and product desorption stages. Existing chemical reduction methods require the addition of a reducing agent and subsequent loading onto the electrode, resulting in weak adhesion between the active layer and the substrate. This invention utilizes in-situ electrochemical reduction to achieve chemical bonding with the electrode while forming active sites, thereby enhancing catalytic stability. It enables the controllable construction of multiple active sites, enhancing the adsorption and activation capacity of carbon dioxide. The three-dimensional network structure provides a high specific surface area and rapid mass transfer channels, improving reaction kinetics. The in-situ reduction process simplifies the preparation procedure, avoids the interfacial loss problems of traditional supported processes, and ensures stable catalyst activity at industrial-grade current densities. This preparation method effectively solves the technical bottlenecks of low catalyst efficiency and short lifespan in the electroreduction of carbon dioxide in thermal power plants.

[0017] Furthermore, the proportions of copper, tin, and bismuth salts synergistically construct a metal composite system. The mixing ratio of isopropanol and propylene oxide ensures the full dissolution of the metal salts and the formation of a stable precursor solution. The precise addition of deionized water controls the hydrolysis reaction rate, preventing premature precipitation of metal ions. The synergistic design of the component proportions optimizes the stability of the precursor solution, providing a homogeneous raw material basis for subsequent in-situ reduction to form a highly active composite catalyst.

[0018] Furthermore, during the aging process, the metal salt and propylene oxide form a cross-linked network in an organic solvent, ensuring that the molecular chains are fully extended and do not shrink excessively within 12-24 hours, thus maintaining the porous structure of the precursor. Vacuum drying avoids pore collapse caused by rapid dehydration. During the reduction reaction, CO2 gas is introduced into the cathode surface at a constant flow rate, forming a bicarbonate ion buffer system with the KHCO3 electrolyte. A stable potential difference is established through the three-electrode system, promoting the synergistic reduction of metal ions in the precursor on the cathode surface, forming a Cu-Sn-Bi composite structure with high catalytic activity.

[0019] Furthermore, by controlling the CO2 flow rate at 10-20 mL / min, a stable diffusion layer is formed on the catalyst surface, maintaining reactant concentration while preventing erosion and damage to the catalyst layer by gas turbulence. A 0.5-1.0 mol / L KHCO3 solution is used as the electrolyte, ensuring the solution's conductivity while avoiding the dissolution of metal active components caused by high-concentration electrolytes. (300-500 mA·cm⁻¹) 2 The current density range effectively suppresses the competitive occurrence of hydrogen evolution side reactions while ensuring sufficient reduction potential to drive the reaction. The reaction time of 0.5-1.0 h completes the transformation of the precursor into the active catalytic phase while avoiding excessive catalyst grain growth caused by prolonged energization.

[0020] This invention also discloses a composite bismuth-based catalyst prepared by the above-mentioned method. Traditional methods often employ single metals or binary composite systems, whose catalytic activity is limited by a limited number of active sites and electronic structures. This invention, however, utilizes the synergistic effect of ternary metals, complementing the conductivity of copper, the electronic modulation capability of tin, and the carbon dioxide adsorption characteristics of bismuth, effectively enhancing catalytic activity. Simultaneously, the in-situ reduction technology avoids the sintering problem of active components caused by traditional high-temperature calcination, maintaining the catalyst's nanoscale dispersion. This solves the technical defects of insufficient active sites and poor product selectivity in traditional catalysts. The ternary metal composite system significantly increases the density of active sites, optimizes the adsorption energy barrier of intermediate products, and preferentially converts carbon dioxide along the formate formation pathway. The combination of the porous precursor structure and the in-situ reduction process ensures that the catalyst has a stable three-phase reaction interface and long-lasting electrochemical stability, maintaining high catalytic efficiency during continuous operation.

[0021] This invention also discloses the application of the composite bismuth-based catalyst prepared by the above-mentioned method in emission reduction in thermal power plants. In current thermal power plants, the widely used lime or limestone desulfurization technology generates a large amount of solid waste. This invention achieves the recycling of waste residue by introducing carbon dioxide into it. The introduced carbon dioxide can react with calcium carbonate or lime in the waste residue to generate soluble salts such as calcium bicarbonate. These salts can further participate in electroreduction reactions during electrolysis, converting into high-value-added chemicals or fuels. This not only achieves the regeneration of calcium carbonate but also reduces the treatment cost and environmental pressure of waste residue. It improves electroreduction efficiency, achieves efficient utilization of industrial waste, and avoids resource waste and environmental pollution. By recycling the waste calcium carbonate and unreacted lime from industrial waste, this invention not only solves the problem of treating desulfurization waste residue from thermal power plants but also achieves the dual goals of carbon resource recycling and energy conservation and emission reduction. It effectively reduces carbon emissions from thermal power plants, realizes the recycling of carbon resources, and, due to the use of in-situ absorption and conversion technology, reduces raw material costs and energy consumption, thereby improving economic efficiency. The generated chemicals have high market value, providing a new economic growth point for the transformation, upgrading, and sustainable development of thermal power plants.

[0022] Furthermore, the catalyst dispersion is ultrasonically treated to form a nanoscale particle suspension system. During spraying, the atomized droplets uniformly adhere to the surface of the electrode pores, forming a continuous catalyst layer. In the drying stage, after solvent evaporation, the catalyst particles and the electrode substrate are fixed through physical adsorption and chemical bonding, forming a stable active interface. When the electrode is applied to the electroreduction system, carbon dioxide in the flue gas reaches the surface of the catalyst layer through the diffusion electrode pores and undergoes a reduction reaction to generate formate under the influence of an electric field. In this process, the metal synergistic effect of the catalyst regulates the reaction pathway, suppresses hydrogen evolution side reactions, and the improved uniformity and stability of the catalyst layer significantly enhances the formate selectivity. The electrode structure design reduces the reaction overpotential, making it suitable for industrial flue gas treatment environments containing impurities.

[0023] This invention also discloses a system for the electroreduction of carbon dioxide to formate for emission reduction in thermal power plants. Flue gas emitted from the power plant enters a countercurrent absorption tower, where it forms a countercurrent contact with a slurry containing limestone or lime flowing downwards. Carbon dioxide is absorbed, forming calcium carbonate precipitate. A slurry circulation pump continuously transports the mixed slurry to a sedimentation tank, where solids settle and separate. A precipitate circulation pump returns some of the precipitate to the countercurrent absorption tower to participate in the reaction. The filtered clean slurry is injected into the electroreduction reaction device via a fuel cell feed pump. Under the action of a composite bismuth-based catalyst loaded on the surface of the gas diffusion electrode, carbon dioxide is reduced to formate at a constant current density. An IrO2 / C electrode is used in the anode region for oxygen absorption, avoiding interference from hydrogen evolution side reactions. A product collection system separates and purifies the electrolysis products, and a monitoring device adjusts the system operating parameters in real time to ensure coordinated operation of all stages. The entire process achieves a closed-loop treatment from carbon dioxide capture and waste recovery to electrochemical conversion.

[0024] Furthermore, when the flue gas emitted from the thermal power plant passes through the countercurrent absorption tower, it forms a countercurrent flow with the limestone or lime-containing slurry flowing downwards. A carbon dioxide absorption reaction occurs on the packing surface, generating a calcium carbonate suspension. A slurry circulation pump drives the slurry to continuously circulate within the countercurrent absorption tower. Part of the slurry enters a sedimentation tank via branch pipelines for solid-liquid separation. A sediment circulation pump pumps unreacted lime deposited at the bottom back into the absorption tower to participate in the reaction. The clean slurry is then transported by the fuel cell feed pump to a filter to remove residual particles before entering the electroreduction fuel cell stack. An electroreduction reaction occurs between the IrO2 / C anode and the catalyst-loaded gas diffusion cathode. A programmable high-power power supply dynamically adjusts the output current according to the reaction requirements. This closed-loop system reduces solid waste emissions through sediment recycling, while filtration and purification ensure the long-term stable operation of the electroreduction carbon dioxide fuel cell stack.

[0025] Furthermore, driven by the slurry circulation pump, the limestone or lime-containing slurry in the countercurrent absorption tower continuously circulates, absorbing carbon dioxide and generating calcium carbonate precipitate during countercurrent contact with the flue gas emitted from the thermal power plant. Unreacted lime particles remain suspended in the slurry. After the slurry containing precipitates enters the settling tank, the precipitate circulation pump mechanically agitates the material in the tank, causing large precipitate particles to settle and separate, while unreacted fine lime particles are resuspended and participate in subsequent circulation. The clean slurry after solid-liquid separation is pressurized and transported to the cathode area of ​​the electroreduction carbon dioxide stack by the fuel cell feed pump. The dissolved calcium bicarbonate releases carbon dioxide under the action of the electric field and participates in the electroreduction reaction, realizing the recycling of calcium-based components in the desulfurization waste residue. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the system for producing formate from electroreduced carbon dioxide for emission reduction in thermal power plants, as disclosed in this invention.

[0027] Among them: 1. Countercurrent absorption tower; 2. Slurry circulation pump; 3. Sedimentation tank; 4. Sediment circulation pump; 5. Electric stack feed pump; 6. Filter; 7. Electro-reducing carbon dioxide electric stack; 8. Programmable high-power power supply; L1. Slurry containing limestone or lime; L2. Flue gas emitted by thermal power plant. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0030] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0031] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0032] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.

[0033] In this invention, unless otherwise specified, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6~22" indicates that all real numbers between "6~22" have been listed in this document, and "6~22" is simply a shortened representation of these numerical combinations.

[0034] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0035] In this invention, the term "and / or" as used herein refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0036] In this invention, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.

[0037] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0038] This invention discloses a method for preparing a composite bismuth-based catalyst, comprising the following steps: Copper salt, tin salt and bismuth salt are mixed in an organic solvent, and then propylene oxide and deionized water are added. After aging and vacuum drying, a precursor is obtained. The precursor is placed in the cathode region of a standard three-electrode gas diffusion flow electrolytic cell, and after reduction reaction, the precursor is converted into a composite bismuth-based catalyst in situ.

[0039] A precursor for a composite bismuth-based catalyst was prepared through specific chemical ratios and synthesis steps. Specifically, the copper salt was CuCl2·2H2O; the tin salt was SnCl2·2H2O; the bismuth salt was Bi(NO3)3·5H2O; and the organic solvent was isopropanol. 0.2-0.5 g of CuCl2·2H2O, 0.5-1.0 g of SnCl2·2H2O, and 5.2-10.5 g of Bi(NO3)3·5H2O were mixed in 10-20 mL of isopropanol, and then 10-20 mL of propylene oxide and 2-5 mL of deionized water were added under ultrasonic water bath conditions to form a mixture. After aging for 12-24 h and vacuum drying at 50-70 °C for 12-24 h, the precursor was obtained.

[0040] Subsequently, in a standard three-electrode gas diffusion flow electrolyzer, the precursor was converted into a Cu-Sn-Bi composite bismuth-based catalyst via in-situ reduction. During this process, CO2 gas was introduced into the gas channel at a specific flow rate, while KHCO3 electrolyte solution was simultaneously introduced into the cathode and anode regions, and the reduction reaction was carried out at a constant current density. Specifically, CO2 gas was introduced into the gas channel at a flow rate of 10-20 mL / min, and 0.5-1.0 mol / L KHCO3 electrolyte solution was introduced into the cathode and anode regions, respectively, at a current density of 300-500 mA·cm⁻¹. -2 The precursor was reduced at a constant current density for 0.5-1.0 h to form a composite bismuth-based catalyst in situ.

[0041] Compared with the present invention, traditional Cu-Bi composite bismuth-based catalysts, Sn-Bi composite bismuth-based catalysts, and single Bi-based catalysts all have shortcomings in catalytic performance and product selectivity. Comparative examples show that the Cu-Sn-Bi composite bismuth-based catalyst of the present invention can significantly improve the formate formation rate and selectivity under the same conditions.

[0042] This invention also discloses a Cu-Sn-Bi composite bismuth-based catalyst prepared by the above-described method, which can efficiently convert carbon dioxide into formate via electroreduction. Not only does it achieve efficient carbon dioxide conversion, but through a precisely designed catalyst structure, it significantly improves the conversion efficiency and product selectivity of the electrochemical reduction of carbon dioxide to formate, exhibiting high efficiency and stability. The synthesis method of this composite bismuth-based catalyst is simple and easy to operate, making it suitable for large-scale production. Furthermore, this composite bismuth-based catalyst demonstrates excellent performance in the application of electrochemical reduction of carbon dioxide to formate, possessing significant practical application value.

[0043] The composite bismuth-based catalyst of this invention, through precise design, effectively combines the electronic and geometric properties of different metal elements, achieving precise control of the carbon dioxide electroreduction reaction. By utilizing isolated heteroatoms to precisely control the electronic activity of the active metal catalyst, the reaction pathway of carbon dioxide protonation to the COOH* intermediate is effectively suppressed, thereby promoting the formation of formate. This strategy not only improves the selectivity of the target product but also reduces the formation of byproducts, providing a new approach for the efficient conversion of carbon dioxide.

[0044] This invention provides a highly efficient and environmentally friendly method for synthesizing composite electrode materials, and the application of the Cu-Sn-Bi composite bismuth-based catalyst prepared by this method in the electroreduction of carbon dioxide to formate. This method not only has significant technical advantages but also provides a new approach for the efficient conversion and resource utilization of carbon dioxide.

[0045] This invention proposes a method for synthesizing composite electrode materials, specifically targeting the synthesis of Cu-Sn-Bi composite bismuth-based catalysts that efficiently convert carbon dioxide to formate via electroreduction. This method achieves high-efficiency carbon dioxide conversion and high product selectivity through precisely designed catalyst structures. Furthermore, the synthesis process is simple, easy to operate, and suitable for large-scale production. Compared to traditional Cu-Bi, Sn-Bi composite bismuth-based catalysts and single Bi-based catalysts, the Cu-Sn-Bi composite bismuth-based catalyst of this invention significantly improves the formate formation rate and selectivity under the same conditions.

[0046] The electroreduction process of this invention is carried out in a gas diffusion flow electrolytic cell. The in-situ reduction technique simplifies the catalyst preparation process and ensures the uniformity and stability of the catalyst. Furthermore, by optimizing parameters such as current density and electrolyte concentration, the efficiency of the electroreduction process is further improved.

[0047] The catalyst obtained in this invention is ultrasonically dispersed in isopropanol and sprayed onto the cathode gas diffusion electrode. After drying in an oven at 50-70°C, it is used for the electroreduction of carbon dioxide to formate.

[0048] The specific steps for using the gas diffusion flow electrolyzer are as follows: the gas diffusion flow electrolyzer is divided into an anode region and a cathode region using an ion exchange membrane. The anode region is equipped with an anode electrode for generating current through the oxygen absorption reaction, preferably an IrO2 / C electrode. The cathode region is equipped with a gas diffusion electrode loaded with the composite bismuth-based catalyst of the present invention.

[0049] Furthermore, this invention also proposes a system for the electroreduction of carbon dioxide to formate for emission reduction in thermal power plants. The system includes a flue gas absorption device, a slurry circulation and sedimentation device, a slurry filtration and feeding device, an electroreduction reaction device, a product collection and treatment device, and a system monitoring and maintenance device. This system enables the resource utilization of carbon dioxide emission reduction waste, demonstrating high practicality and environmental benefits.

[0050] Figure 1 This is a schematic diagram of the electro-reduction carbon dioxide to formate system for emission reduction in thermal power plants disclosed in this invention. As can be seen from the figure, the electro-reduction carbon dioxide to formate system for emission reduction in thermal power plants includes: a countercurrent absorption tower 1 for introducing a slurry stream L1 containing limestone or lime and flue gas L2 emitted from the thermal power plant, so that the two come into countercurrent contact to absorb carbon dioxide in the flue gas; and a slurry circulation pump 2 connected to the bottom of the countercurrent absorption tower 1 for circulating the slurry in the tower and improving the carbon dioxide absorption efficiency. The slurry circulation pump 2 forms a circulation loop connected to the countercurrent absorption tower 1 through pipelines. A settling tank 3 is connected to the pipeline branch of the countercurrent absorption tower 1 and the slurry circulation pump 2 to achieve the sedimentation and separation of solids in the slurry; a settling circulation pump 4 is connected to the bottom of the settling tank 3 to extract the precipitate; and a filter 6 is used to receive the slurry after sedimentation and to filter and remove impurities from the slurry. The filter 6 is connected to the outlet pipeline of the settling circulation pump 4 through a pipeline. A feed pump 5, connected to the outlet of filter 6, is used to transport the filtered clean slurry to the electroreduction reaction zone. An electroreduction carbon dioxide stack 7, connected to the outlet of feed pump 5 and equipped with electrodes, is used to electroreductize carbon dioxide into formate. A programmable high-power power supply 8, connected to the electroreduction carbon dioxide stack 7, provides power to the stack and can adjust the power output according to the stack's operating status. A slurry stream L1 containing limestone or lime is connected to the upper part of the countercurrent absorption tower 1, and flue gas L2 emitted from the thermal power plant is connected to the lower part of the countercurrent absorption tower 1. The electroreduction carbon dioxide stack 7 and the programmable high-power power supply 8 work together to use electrical energy to drive carbon dioxide to undergo a reduction reaction at the electrodes to generate formate. All components are connected sequentially through pipelines to form a complete system process from carbon dioxide absorption, slurry treatment to electroreduction conversion to formate preparation.

[0051] The system for producing formate from electroreduced carbon dioxide in thermal power plants, provided by this invention, is specifically applied to the electroreduction of carbon dioxide to formate, and includes the following steps: Step 1: Flue Gas Absorption Stage Flue gas L2 emitted from the thermal power plant is introduced into countercurrent absorption tower 1. Simultaneously, a slurry L1 containing limestone or lime is poured into countercurrent absorption tower 1 from above, coming into countercurrent contact with the flue gas L2 entering from below. Carbon dioxide in the flue gas L2 is absorbed by the limestone or limestone-containing slurry L1, forming a carbon dioxide-rich slurry. Simultaneously, the limestone or limestone in the carbon dioxide-rich slurry reacts with the carbon dioxide to produce solid substances such as calcium carbonate.

[0052] Step Two: Slurry Circulation and Sedimentation Stage The limestone or lime-containing slurry L1, after absorbing carbon dioxide, is circulated by the slurry circulation pump 2 to ensure sufficient contact between the limestone or lime-containing slurry L1 and the flue gas L2 emitted from the thermal power plant, thereby improving the carbon dioxide absorption efficiency. During the circulation process, the amount of solid matter in the limestone or lime-containing slurry L1 gradually increases, and some of the solid matter will settle in the sedimentation tank 3. The sediment in the sedimentation tank 3 can be extracted by the sediment circulation pump 4 for further treatment or reuse.

[0053] Step 3: Slurry filtration and feeding stage: The carbon dioxide-rich slurry is filtered through filter 6 to remove solid particles and impurities, resulting in a clean carbon dioxide slurry. This clean carbon dioxide slurry is then fed into the electroreduction carbon dioxide stack 7 via the stack feed pump 5, providing raw materials for the electroreduction reaction.

[0054] Step 4: Electroreduction reaction stage In the electroreduction carbon dioxide fuel cell stack 7, carbon dioxide undergoes an electroreduction reaction at the electrodes, converting into formate, while oxygen is produced as a byproduct at the anode. The electroreduction reaction requires electrical energy, which is provided by a programmable high-power power supply 8 of the electroreduction carbon dioxide fuel cell stack 7. The programmable high-power power supply 8 can adjust the power output according to the operating status and needs of the electroreduction carbon dioxide fuel cell stack 7 to ensure the stable operation of the electroreduction reaction.

[0055] Step 5: Product Collection and Processing Stage The chemicals and byproducts generated by the electroreduction reaction are collected through a corresponding collection system. The chemicals can be used in subsequent chemical production or as energy, achieving resource recycling. The byproducts can be further processed or reused as needed.

[0056] Step Six: System Monitoring and Maintenance Phase: The entire system is equipped with monitoring equipment that can monitor the system's operating status and various parameters in real time. Based on the monitoring data, operators can make timely adjustments and maintenance to ensure the system's stable operation and efficient utilization.

[0057] This system utilizes carbon dioxide emitted from thermal power plants and waste residue containing limestone or lime through electrochemical reduction to produce carbon dioxide, achieving both carbon dioxide emission reduction and waste residue resource utilization. The system's operation methods and procedures are clear and straightforward, demonstrating high practicality and environmental benefits. Furthermore, the system is equipped with monitoring equipment to monitor its operating status and various parameters in real time, ensuring stable operation and efficient utilization.

[0058] This invention proposes a system for the electroreduction and conversion of carbon dioxide emitted from thermal power plants and waste residue containing limestone or lime. This system, through integrated in-situ absorption and conversion technology, achieves both carbon dioxide emission reduction and resource utilization of waste residue, demonstrating high practicality and environmental benefits. The innovations of this invention lie in the integrated in-situ absorption and conversion technology, the design and application of a highly efficient electroreduction catalyst, the integrated system construction and intelligent control, and the strategy that balances environmental friendliness and economic benefits. It provides an innovative, efficient, and sustainable technical solution for emission reduction in thermal power plants, possessing broad application prospects and market potential.

[0059] The composite bismuth-based catalyst, method, and their application and system in emission reduction in thermal power plants disclosed in this invention have the following advantages: 1) In-situ absorption and conversion integrated technology This invention proposes an integrated in-situ absorption and conversion technology that directly converts carbon dioxide emitted from thermal power plants into usable electrolyte without the need for additional carbon dioxide capture, purification, and transportation processes. This revolutionary design not only significantly reduces the cost of carbon dioxide emission reduction technologies but also achieves a seamless connection between carbon dioxide emissions at the source and resource utilization, significantly improving the efficiency and environmental benefits of the entire emission reduction process.

[0060] 2) Design and application of high-efficiency electroreduction catalysts To address the characteristics of carbon dioxide emissions from thermal power plants, this invention develops a high-performance electroreduction catalyst. This catalyst not only possesses excellent carbon dioxide adsorption and activation capabilities but also efficiently converts carbon dioxide into high-value-added chemicals or fuels in an in-situ electrolyte. Through meticulous selection of catalyst materials and structural design, this invention successfully solves the problems of insufficient activity and poor selectivity in traditional catalysts during carbon dioxide electroreduction, achieving efficient and targeted conversion of carbon dioxide resources.

[0061] 3) Integrated system construction and intelligent control Based on in-situ absorption and conversion technology, this invention also constructs an integrated electroreduction carbon dioxide system. This system integrates multiple stages, including carbon dioxide absorption, electrolyte preparation, electroreduction reaction, and product collection, achieving fully automated control of the entire chain from carbon dioxide emission to resource utilization. Through an intelligent control system, this invention can monitor the reaction process in real time, optimize operating parameters, ensure stable system operation, and further improve the efficiency of carbon dioxide emission reduction and conversion.

[0062] 4) Balancing environmental friendliness and economic benefits The electroreduction carbon dioxide technology of this invention not only effectively reduces carbon emissions from thermal power plants but also achieves the recycling of carbon resources, resulting in significant environmental benefits. Simultaneously, the use of in-situ absorption and conversion technology reduces raw material costs and energy consumption, improving economic efficiency. Furthermore, the chemicals generated by this technology have high market value, providing a new economic growth point for the transformation, upgrading, and sustainable development of thermal power plants.

[0063] 5) Recycling of industrial waste, including calcium carbonate and unreacted lime. In current thermal power plants, the widely used lime or limestone desulfurization technology generates a large amount of solid waste, mainly consisting of unreacted lime or calcium carbonate. If not properly treated, this waste not only occupies land resources but may also cause secondary pollution. This invention innovatively proposes using this solid waste as a supplementary raw material for electroreduction carbon dioxide technology, achieving waste recycling by introducing carbon dioxide into the process. In the electroreduction system, the introduced carbon dioxide reacts with the calcium carbonate or lime in the waste residue to generate soluble salts such as calcium bicarbonate. These salts can further participate in the electroreduction reaction during electrolysis, transforming into high-value-added chemicals or fuels. This process not only achieves the recycling of calcium carbonate but also reduces waste residue treatment costs and environmental pressure. This strategy not only improves electroreduction efficiency but also achieves efficient utilization of industrial waste, avoiding resource waste and environmental pollution. By recycling the waste calcium carbonate and unreacted lime from industrial waste, this invention not only solves the problem of desulfurization waste residue treatment in thermal power plants but also achieves the dual goals of carbon resource recycling and energy conservation and emission reduction.

[0064] This invention provides an innovative, efficient, and sustainable technical solution for emission reduction in thermal power plants through in-situ absorption and conversion integration technology, the design and application of a highly efficient electroreduction catalyst, integrated system construction and intelligent control, and a strategy that balances environmental friendliness and economic benefits. It has broad application prospects and market potential. The catalyst preparation process of this invention is simple and low-cost, making it easy to industrialize, and is of great significance for promoting the commercial application of carbon dioxide electroreduction technology.

[0065] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0066] Example 1 A method for preparing a composite bismuth-based catalyst includes the following steps: First, the precursor for the Cu-Sn-Bi composite bismuth-based catalyst was synthesized. 0.2 g of CuCl₂·2H₂O, 0.5 g of SnCl₂·2H₂O, and 5.2 g of Bi(NO₃)₃·5H₂O were added to a beaker containing 10 mL of isopropanol. Then, 10 mL of propylene oxide and 2 mL of deionized water were added sequentially under ultrasonic water bath conditions. The resulting mixture was aged for 12 h and then vacuum dried at 50 °C for 12 h.

[0067] Then, in-situ reduction was performed in a standard three-electrode gas diffusion flow electrolytic cell. CO2 gas was introduced into the gas channel at a flow rate of 10 mL / min, while 0.5 mol / L KHCO3 was introduced as the electrolyte into the cathode and anode regions, respectively, at a pressure of 300 mA·cm⁻¹. -2 The precursor was reduced at a constant current density for 0.5 h to form a Cu-Sn-Bi composite bismuth-based catalyst in situ.

[0068] Example 2 A method for preparing a composite bismuth-based catalyst includes the following steps: First, the precursor for the Cu-Sn-Bi composite bismuth-based catalyst was synthesized. 0.2 g of CuCl₂·2H₂O, 0.7 g of SnCl₂·2H₂O, and 6.5 g of Bi(NO₃)₃·5H₂O were added to a beaker containing 10 mL of isopropanol. Then, 10 mL of propylene oxide and 2 mL of deionized water were added sequentially under ultrasonic water bath conditions. The resulting mixture was aged for 12 h and then vacuum dried at 50 °C for 14 h.

[0069] Then, in-situ reduction was performed in a standard three-electrode gas diffusion flow electrolytic cell. CO2 gas was introduced into the gas channel at a flow rate of 12 mL / min, while 0.5 mol / L KHCO3 was introduced as the electrolyte into the cathode and anode regions, respectively, at a pressure of 300 mA·cm⁻¹.-2 The precursor was reduced at a constant current density for 0.5 h to form a Cu-Sn-Bi composite bismuth-based catalyst in situ.

[0070] Example 3 A method for preparing a composite bismuth-based catalyst includes the following steps: First, the precursor for the Cu-Sn-Bi composite bismuth-based catalyst was synthesized. 0.3 g of CuCl₂·2H₂O, 0.6 g of SnCl₂·2H₂O, and 8.4 g of Bi(NO₃)₃·5H₂O were added to a beaker containing 12 mL of isopropanol. Then, 12 mL of propylene oxide and 3 mL of deionized water were added sequentially under ultrasonic water bath conditions. The resulting mixture was aged for 18 h and then vacuum dried at 55 °C for 18 h.

[0071] Then, in-situ reduction was performed in a standard three-electrode gas diffusion flow electrolytic cell. CO2 gas was introduced into the gas channel at a flow rate of 14 mL / min, and 0.7 mol / L KHCO3 was introduced as the electrolyte into the cathode and anode regions, respectively, at 300 mA·cm⁻¹. -2 The precursor was reduced at a constant current density for 0.5 h to form a Cu-Sn-Bi composite bismuth-based catalyst in situ.

[0072] Example 4 A method for preparing a composite bismuth-based catalyst includes the following steps: First, the precursor for the Cu-Sn-Bi composite bismuth-based catalyst was synthesized. 0.4 g of CuCl₂·2H₂O, 0.8 g of SnCl₂·2H₂O, and 9.6 g of Bi(NO₃)₃·5H₂O were added to a beaker containing 15 mL of isopropanol. Then, 15 mL of propylene oxide and 4 mL of deionized water were added sequentially under ultrasonic water bath conditions. The resulting mixture was aged for 20 h and then vacuum dried at 60 °C for 20 h.

[0073] Then, in-situ reduction was performed in a standard three-electrode gas diffusion flow electrolytic cell. CO2 gas was introduced into the gas channel at a flow rate of 18 mL / min, while 0.9 mol / L KHCO3 was introduced as the electrolyte into the cathode and anode regions, respectively, at a pressure of 400 mA·cm⁻¹. -2 The precursor was reduced at a constant current density for 0.8 h to form a Cu-Sn-Bi composite bismuth-based catalyst in situ.

[0074] Example 5 A method for preparing a composite bismuth-based catalyst includes the following steps: First, the precursor for the Cu-Sn-Bi composite bismuth-based catalyst was synthesized. 0.5 g of CuCl₂·2H₂O, 1.0 g of SnCl₂·2H₂O, and 10.5 g of Bi(NO₃)₃·5H₂O were added to a beaker containing 20 mL of isopropanol. Then, 20 mL of propylene oxide and 5 mL of deionized water were added sequentially under ultrasonic water bath conditions. The resulting mixture was aged for 24 h and then vacuum dried at 70 °C for 24 h.

[0075] Then, in-situ reduction was performed in a standard three-electrode gas diffusion flow electrolytic cell. CO2 gas was introduced into the gas channel at a flow rate of 20 mL / min, while 1.0 mol / L KHCO3 was introduced as the electrolyte into the cathode and anode regions, respectively, at a pressure of 500 mA·cm⁻¹. -2 The precursor was reduced at a constant current density for 1.0 h to form a Cu-Sn-Bi composite bismuth-based catalyst in situ.

[0076] Comparative Example 1 A method for preparing a Cu-Bi composite bismuth-based catalyst includes the following steps: First, the precursor for the Cu-Bi composite bismuth-based catalyst was synthesized. 0.2 g of CuCl₂·2H₂O and 5.2 g of Bi(NO₃)₃·5H₂O were added to a beaker containing 10 mL of isopropanol. Then, 10 mL of propylene oxide and 2 mL of deionized water were added sequentially under ultrasonic water bath conditions. The resulting mixture was aged for 12 h and then vacuum dried at 50 °C for 12 h.

[0077] Then, in-situ reduction was performed in a standard three-electrode gas diffusion flow electrolytic cell. CO2 gas was introduced into the gas channel at a flow rate of 10 mL / min, and 0.5 mol / L KHCO3 was introduced as the electrolyte into the cathode and anode regions, respectively, at a pressure of 300 mA·cm⁻¹. -2 The precursor was reduced at a constant current density for 0.5 h to form a Cu-Bi composite bismuth-based catalyst in situ.

[0078] Comparative Example 2 A method for preparing a Sn-Bi composite bismuth-based catalyst includes the following steps: First, the precursor for the Sn-Bi composite bismuth-based catalyst was synthesized. 0.5 g of SnCl₂·2H₂O and 5.2 g of Bi(NO₃)₃·5H₂O were added to a beaker containing 10 mL of isopropanol. Then, 10 mL of propylene oxide and 2 mL of deionized water were added sequentially under ultrasonic water bath conditions. The resulting mixture was aged for 12 h and then vacuum dried at 50 °C for 12 h.

[0079] Then, in-situ reduction was performed in a standard three-electrode gas diffusion flow electrolytic cell. CO2 gas was introduced into the gas channel at a flow rate of 10 mL / min, and 0.5 mol / L KHCO3 was introduced as the electrolyte into the cathode and anode regions, respectively, at a pressure of 300 mA·cm⁻¹. -2 The precursor was reduced at a constant current density for 0.5 h to form an in-situ Sn-Bi composite bismuth-based catalyst.

[0080] Comparative Example 3 A method for preparing a Bi-based catalyst includes the following steps: First, the precursor for the Bi-based catalyst was synthesized. 5.2 g of Bi(NO3)3·5H2O was added to a beaker containing 10 mL of isopropanol, followed by the sequential addition of 10 mL of propylene oxide and 2 mL of deionized water under ultrasonic water bath conditions. The resulting mixture was aged for 12 h and then vacuum dried at 50 °C for 12 h.

[0081] Then, in-situ reduction was performed in a standard three-electrode gas diffusion flow electrolytic cell. CO2 gas was introduced into the gas channel at a flow rate of 10 mL / min, and 0.5 mol / L KHCO3 was introduced as the electrolyte into the cathode and anode regions, respectively, at a pressure of 300 mA·cm⁻¹. -2 The precursor was reduced at a constant current density for 0.5 h to form a Bi-based catalyst in situ.

[0082] The catalysts prepared in Examples 1-5 and Comparative Examples 1-3 were used for the electrochemical reduction of carbon dioxide to formate, comprising the following steps: 0.1 g of the composite bismuth-based catalyst prepared in each example was taken, 10 mL of isopropanol was added, and the mixture was sonicated for 0.5 h to form a uniform dispersion. The dispersion was then sprayed onto the surface of a gas diffusion electrode on a carbon paper substrate (spraying amount 1.0 mg / cm²). 2 The cathode was prepared by drying the catalyst in a 50℃ oven for 12 hours. During electrolysis, the cathode was a carbon paper electrode loaded with the aforementioned composite bismuth-based catalyst, the anode was an IrO2 / C electrode, and the reference electrode was Ag / AgCl. 0.5 mol / L KHCO3 electrolyte was introduced into both the anode and cathode regions, and CO2 was introduced into the cathode gas channel at a rate of 10 mL / min. A programmable high-power DC power supply was set to output the current density of each embodiment. CO2 was reduced at the active sites of the bismuth-based catalyst, and the generated formate dissolved in the cathode electrolyte. The conversion efficiency and product selectivity of the catalyst were tested, including the following steps: the formate formation rate was obtained by chromatographic detection of the formic acid content in the cathode electrolyte and converted into the yield per unit area per unit time. Product selectivity refers to formic acid selectivity, expressed as Faraday efficiency. FE The Faraday efficiency is an important indicator for evaluating the performance of carbon dioxide electroreduction reactions. It represents the ratio of the amount of electricity consumed by a certain reduction product to the total amount of electricity consumed.

[0083] The formula for calculating Faraday efficiency is as follows: FE = z · n · F / Q ×100% in, z This represents the number of electrons transferred per molecule of formic acid. n The number of moles of product i generated per unit time. F It is the Faraday constant (96485.3 C / mol). Q This refers to the amount of electricity input per unit of time.

[0084] Table 1. Comparison of the electrochemical reduction rates and product selectivity of carbon dioxide to formate by the catalysts prepared in Examples 1-5 and Comparative Examples 1-3.

[0085] Table 1 compares the conversion efficiency and product selectivity of the catalysts prepared in Examples 1-5 and Comparative Examples 1-3 in the electrochemical reduction of carbon dioxide to formate. As can be seen from the table, the Cu-Sn-Bi composite bismuth-based catalysts prepared in Examples 1-5 are significantly superior to the Cu-Bi composite bismuth-based catalysts of Comparative Example 1, Sn-Bi composite bismuth-based catalysts of Comparative Example 2, and Bi-based catalysts of Comparative Example 3 in the electrochemical reduction of carbon dioxide to formate. The specific differences are reflected in the following two aspects: 1) In terms of formate formation rate, the ternary composite catalyst exhibits higher activity. The formate formation rate in Examples 1-5 ranged from 231.8 to 419.3 mg / (cm³). 2 The yield increased with optimization of preparation parameters (metal salt dosage, current density, electrolyte concentration), while the yields of comparative examples 1-3 were only 192.1-219.2 mg / (cm³). 2 ·h), among which the Bi-based catalyst (Comparative Example 3) had the lowest formation rate (192.1 mg / (cm³)). 2 While the binary composite catalysts (Comparative Examples 1 and 2) showed slightly better performance than the single Bi-based catalysts, they were still far inferior to the ternary composite system. This indicates that copper enhances conductivity, tin regulates electronic structure, and bismuth strengthens CO2 adsorption. The synergistic effect of the Cu, Sn, and Bi ternary system significantly improves catalytic activity, solving the problem of insufficient active sites in traditional catalysts.

[0086] 2) In terms of product selectivity, the ternary composite catalyst exhibits stronger directional conversion capability. The formate selectivity (Faraday efficiency) of Examples 1-5 remained at 96.7%-99.1%, with Example 2 (SnCl2•2H2O 0.7g) showing the highest selectivity (99.1%), almost directionally converting CO2 into formate. The selectivity of Comparative Examples 1-3 was significantly lower, ranging from 80.3%-91.6%. The single Bi-based catalyst (Comparative Example 3) had a selectivity of only 80.3%, exhibiting numerous side reactions such as hydrogen evolution. The Cu-Bi binary catalyst (Comparative Example 1) had a selectivity of 85.7%, and the Sn-Bi binary catalyst (Comparative Example 2) had a selectivity of 91.6%, which, while superior to the single Bi-based catalyst, still lacked the precise control of the reaction pathway by the ternary metal, failing to completely suppress side reactions. The Cu-Sn-Bi ternary composite system effectively overcomes the bottlenecks of low activity and poor selectivity of traditional single / binary catalysts through multi-active site synergy, mesoporous structure mass transfer optimization, and stable interface for in-situ reduction, providing a highly efficient and stable catalytic solution for the electroreduction of CO2 to formate in thermal power plants.

[0087] In summary, the electroreduction process of this invention is carried out in a gas diffusion flow electrolytic cell. Through in-situ reduction technology, the precursor is directly converted into a composite bismuth-based catalyst, greatly simplifying the preparation process and ensuring the uniformity and stability of the catalyst. Simultaneously, by optimizing parameters such as current density and electrolyte concentration, the efficiency of the electroreduction process is further improved. By precisely designing the Cu-Sn-Bi composite bismuth-based catalyst, the electronic and geometric properties of different metal elements are effectively combined, thereby achieving precise control of the carbon dioxide electroreduction reaction. This composite catalyst not only exhibits excellent catalytic performance but also, through its unique interfacial synergistic effect, alters the conversion pathway of carbon dioxide to formate, suppressing competitive reactions and improving conversion efficiency and product selectivity. Specifically, by utilizing isolated heteroatoms to precisely control the electronic activity of the active metal catalyst, the reaction pathway of protonation of carbon dioxide to the COOH* intermediate is effectively suppressed, thereby promoting formate formation. This strategy not only improves the selectivity of the target product but also reduces the formation of byproducts, providing a new approach for the efficient conversion of carbon dioxide.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a composite bismuth-based catalyst, characterized in that, Includes the following steps: Copper salt, tin salt and bismuth salt are mixed in an organic solvent, and then propylene oxide and deionized water are added. After aging and vacuum drying, a precursor is obtained. The precursor is placed in the cathode region of a standard three-electrode gas diffusion flow electrolytic cell, and after in-situ reduction reaction, the precursor is converted into a composite bismuth-based catalyst in situ.

2. The method for preparing the composite bismuth-based catalyst according to claim 1, characterized in that, The ratio of copper salt, tin salt, bismuth salt, organic solvent, propylene oxide and deionized water is (0.2-0.5) g : (0.5-1.0) g : (5.2-10.5) g : (10-20) mL : (10-20) mL : (2-5) mL; The copper salt is CuCl2·2H2O; the tin salt is SnCl2·2H2O; the bismuth salt is Bi(NO3)3·5H2O; and the organic solvent is isopropanol.

3. The method for preparing the composite bismuth-based catalyst according to claim 1, characterized in that, The aging treatment lasts for 12-24 hours, and the vacuum drying temperature is 50-70℃ for 12-24 hours. The conditions for the reduction reaction include: placing the precursor in the cathode region in a standard three-electrode gas diffusion flow electrolytic cell, introducing CO2 into the gas flow channel, and simultaneously introducing KHCO3 electrolyte solution into the cathode and anode regions. After in-situ reduction reaction under a constant current density, the precursor is converted into a composite bismuth-based catalyst in situ.

4. The method for preparing the composite bismuth-based catalyst according to claim 3, characterized in that, The CO2 flow rate is 10-20 mL / min; the molar concentration of the KHCO3 electrolyte solution is 0.5-1.0 mol / L; and the constant current density is 300-500 mA·cm⁻¹. -2 The in-situ reduction reaction takes 0.5-1.0 hours.

5. A composite bismuth-based catalyst, characterized in that, The composite bismuth-based catalyst was prepared using the method described in any one of claims 1-4.

6. The application of the composite bismuth-based catalyst prepared by the method of any one of claims 1-4 in emission reduction in thermal power plants.

7. The application of the composite bismuth-based catalyst according to claim 6 in emission reduction in thermal power plants, characterized in that, The composite bismuth-based catalyst was ultrasonically dispersed in an organic solvent and sprayed onto the cathode gas diffusion electrode. After drying, it was used to electroreduc the carbon dioxide in the flue gas emitted by thermal power plants to produce formate. The organic solvent was isopropanol, and the drying temperature was 50-70℃.

8. A system for the electroreduction of carbon dioxide to formate for emission reduction in thermal power plants, characterized in that, include: A flue gas absorption device is used to mix a slurry (L1) containing limestone or lime with flue gas (L2) emitted from a thermal power plant, and to absorb carbon dioxide in the flue gas (L2) emitted from the thermal power plant. A slurry circulation and sedimentation device is used to circulate slurry and settle solid substances. A slurry filtration and feeding device is used to filter slurry and provide raw materials for an electroreduction reaction. An electroreduction reactor is used to receive raw materials and carry out an electroreduction reaction. Product collection and processing device, used to collect the products of electroreduction reaction; System monitoring and maintenance devices are used to monitor the system's operating status and parameters; The electroreduction reaction device includes a gas diffusion flow electrolytic cell, which has an anode region and a cathode region. A gas diffusion electrode is installed in the cathode region, and the gas diffusion electrode is loaded with a composite bismuth-based catalyst prepared by the method of any one of claims 1-4.

9. The system for electro-reduction of carbon dioxide to formate for emission reduction in thermal power plants according to claim 8, characterized in that, The flue gas absorption device is a countercurrent absorption tower (1). The slurry circulation and sedimentation device includes: a slurry circulation pump (2) connected to the countercurrent absorption tower (1), a sedimentation tank (3) connected to the slurry circulation pump (2) through a branch pipeline, and a sedimentation circulation pump (4) connected to the sedimentation tank (3). The slurry filtration and feeding device includes: an electric stack feeding pump (5) and a filter (6) connected in sequence to the outlet end of the sedimentation tank (3); The electroreduction reactor includes: an electroreduction carbon dioxide stack (7) and a programmable high-power power supply (8) for regulating power output. The anode region is the oxygen absorption reaction region, and the anode electrode is an IrO2 / C electrode.

10. The system for electro-reduction of carbon dioxide to formate for emission reduction in thermal power plants according to claim 9, characterized in that, The slurry circulation pump (2) and the countercurrent absorption tower (1) form a circulation loop; The sedimentation tank (3) and the sediment circulation pump (4) form a circulation loop; The clean carbon dioxide slurry in the sedimentation tank (3) is fed into the electroreduction carbon dioxide stack (7) by the stack feed pump (5) to provide raw materials for the electroreduction reaction.

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