Method for synthesizing high-value product by capturing and converting CO2 through photoelectric synergistic enhanced microbial electro-synthesis system

Abstract

The invention relates to the technical field of microbial electro-synthesis systems and photocatalysis, in particular to a method for synthesizing high-value chemicals by enhancing the reducing power of suspended microorganisms through photoelectric synergy to improve the CO2 capture and conversion potential. The method comprises the following steps: in a microbial electrosynthesis system, modifying suspended microorganisms by using a photocatalytic material to obtain modified microorganisms capable of receiving photo-induced electrons under an illumination condition; under the synergistic effect of illumination and electrochemical conditions, the reducing power of suspended microorganisms is enhanced; and further capturing and converting CO2 by using suspended microorganisms with enhanced reducing power to generate target products such as acetic acid, ethanol and the like. The problem that the CO2 conversion efficiency is low due to insufficient reducing power of suspended microorganisms in MES is effectively solved through the photoelectric synergistic effect, the CO2 capture and conversion potential of the microorganisms is remarkably improved, and the method has the advantages of being efficient, environmentally friendly and sustainable and is suitable for the field of industrial waste gas treatment and resource utilization.

Description

Technical Field

[0001] The present invention relates to the technical fields of microbial electrosynthesis systems (MES) and photocatalysis, and particularly relates to a method for enhancing the reducing power of suspended microorganisms through photoelectric synergy to improve the potential of CO2 capture and conversion and synthesize high-value chemicals. Background Art

[0002] With the increasing severity of global climate change problems, the capture and resource conversion of CO2 have become the core research directions in the fields of environmental science and energy technology. Microbial electrosynthesis (MES) technology uses microorganisms to catalyze the conversion of CO2 into high-value products such as acetic acid and methane, and has attracted much attention due to its environmental friendliness and sustainability.

[0003] However, this technology faces many challenges in practical applications: firstly, the accumulation of acetic acid in the cathode chamber will inhibit the metabolic activity of acetic acid-producing bacteria, resulting in a decrease in productivity, and subsequent complex processes such as product separation are required to recover the product, significantly increasing the operating cost (see CN 117779070 A); secondly, more critically, in the MES system, suspended microorganisms lack a stable electron supply and have insufficient reducing power, making it difficult to effectively accumulate target products such as acetic acid, and may even cause the degradation of acetic acid, thereby reducing the CO2 conversion efficiency and system stability (see CN 118931978 A). To address these problems, existing technologies have tried to enhance the diversity of the microbial community by inoculating activated sludge (CN 117779070 A) or regulate the hydrogen partial pressure to inhibit acetic acid degradation (CN118931978 A), but these improvement measures only alleviate the problems to a certain extent and fail to fundamentally break through the efficiency bottleneck caused by insufficient electron supply. Especially in a mixed culture system, the competition between suspended microorganisms and biofilm microorganisms in the MES electrode chamber for electrons further weakens their performance and limits the application potential of MES technology in CO2 capture and efficient conversion.

[0004] In recent years, the photocatalytic system combining nano-semiconductor materials with microorganisms has received extensive attention due to its potential to break through the limitations of traditional electron transfer. In traditional MES, suspended microorganisms cannot directly utilize light energy and have limited physical contact with the electrode, resulting in low efficiency of electron transfer from the electrode to the microorganisms, severely restricting the CO2 conversion efficiency. Cadmium sulfide (CdS), as a semiconductor photocatalytic material, has the potential to generate photo-generated electrons under light illumination and can provide an additional electron source for microorganisms. This technology uses photo-generated electrons to replace traditional chemical electron donors to provide an electron source for microbial metabolism. For example, Patent CN 109666703A discloses a technical solution in which a hybrid system is constructed by combining Methanosarcina with cadmium sulfide (CdS), and photo-generated electrons can directly drive the reduction of CO2 to produce methane. Similarly, Patent Document CN117229936 B discloses a photocatalytic system that combines Clostridium butyricum with CdS to utilize solar energy to excite photo-generated electrons, promote the regeneration of intracellular NADH, and thus significantly improve the synthesis efficiency of high-value-added chemicals such as butyric acid. These studies indicate that the synergistic effect of photocatalytic technology and microorganisms can, to a certain extent, make up for the shortage of electron supply in traditional MES and provide new ideas for improving the CO2 conversion efficiency. However, CdS naturally carries a negative charge on its surface, and there is electrostatic repulsion with the negatively charged surface of Gram-negative bacteria, making it difficult to effectively adhere to microorganisms and achieve efficient transfer of photo-generated electrons.

[0005] Therefore, it is necessary to develop a new light energy-driven electron transfer mechanism to solve the problems existing in the prior art. Summary of the Invention

[0006] Aiming at the technical problems of insufficient reducing power of suspended microorganisms and low CO2 capture and conversion efficiency in the existing microbial electrosynthesis (MES) system, the present invention provides a method and system for enhancing the supply of reducing power of suspended microorganisms through optoelectronic synergy, aiming to significantly improve the CO2 capture and conversion potential and electron transfer efficiency.

[0007] In the present invention, by introducing polydimethyldiallylammonium chloride (PDDA), the surface of CdS is modified by its positive charge to form a CdS@PDDA complex, changing the surface potential of CdS from negative charge to positive charge, so as to form a stable hybrid system with the negative-charged surface of Gram-negative bacteria through electrostatic interaction. This scheme not only eliminates the charge repulsion between CdS and microorganisms, but also significantly enhances the interfacial binding force between the two, enabling the modified microorganisms to directly receive the photocatalytically generated electrons under light, thus effectively making up for the defect of insufficient electron supply in traditional MES. Based on this, the present invention further constructs a photo-electro synergistic system by modifying Gram-negative bacteria with CdS@PDDA to form a hybrid system and combining with the stable electron flow provided by the external electric field of MES. This system makes full use of the advantages of high-efficiency light energy capture of photocatalysis technology and stable electron supply of electrochemistry, significantly improving the electron transfer efficiency of suspended microorganisms, thereby enhancing the CO2 conversion efficiency and product stability.

[0008] The first aspect of the present invention is to provide a method for photo-electro synergistically enhancing the capture and conversion of CO2 in a microbial electrosynthesis system, using CdS@PDDA to modify the suspended microorganisms in the system and based on the photo-electro synergistic reduction of the modified suspended microorganisms;

[0009] Specifically, it includes the following steps:

[0010] S11. Provide a microbial electrosynthesis system;

[0011] S12. Use CdS@PDDA to perform single-bacteria modification on the suspended microorganisms in the microbial electrosynthesis system to obtain CdS@PDDA-modified suspended microorganisms;

[0012] S13. Place the CdS@PDDA-modified suspended microorganisms prepared in step S12 in the cathode chamber of the microbial electrosynthesis system, introduce CO2, and capture and convert CO2 to generate the target product under the conditions of an external voltage and light.

[0013] In some embodiments, the preparation method of CdS@PDDA specifically includes the following steps:

[0014] (1) Using the hydrothermal method, cadmium nitrate tetrahydrate, polyvinylpyrrolidone, thioacetamide and hexamethylenetetramine are sequentially added to a round-bottom flask containing ethylenediamine in a certain proportion, stirred evenly and then placed in a polytetrafluoroethylene-lined autoclave, and reacted at 180 °C for 24 hours to obtain CdS nanorods;

[0015] (2) Disperse the CdS nanorods obtained in step (1) in deionized water, add a PDDA solution with a concentration of 3.5% wt, and stir at room temperature for 4 hours to uniformly coat PDDA on the surface of CdS; subsequently, collect the product by centrifugation (6000 rpm, 15 minutes), wash it 3 times with deionized water, and obtain the CdS@PDDA composite after vacuum drying.

[0016] Further, the modification method in step S12 is: co-culture CdS@PDDA with suspended microorganisms so that CdS@PDDA adheres to the surface of the suspended microorganisms;

[0017] In some embodiments, the co-culture conditions are: add CdS@PDDA to the bacterial solution with an OD 600 = 0.3 - 0.5 at a concentration of 100 - 400 mg / L, and shake and culture for 2 - 12 hours;

[0018] The concentration of CdS@PDDA in the MES is 50 mg to 2000 mg / L, preferably 50 - 400 mg / L.

[0019] In a preferred embodiment, step S12 is specifically: under anaerobic conditions, add the prepared CdS@PDDA to the microbial medium so that CdS@PDDA adheres to the surface of the microorganisms through electrostatic interaction or physical adsorption, and shake and culture at 30 °C and 150 rpm to form a microbial-CdS@PDDA hybrid system. Preferably, the culture time of the hybrid system is 5 hours.

[0020] Further, the suspended microorganisms are microorganisms capable of performing CO2 reduction, including but not limited to one or more of acetic acid synthesis microorganisms, methanogens, or hydrogen-producing bacteria.

[0021] In some embodiments, in step S13, the light source has a light wavelength of 200 nm to 800 nm, and more preferably a light source of 400 nm to 700 nm (visible light range);

[0022] In some embodiments, in step S13, the light intensity is a light source of 0.1 mW / cm 2 to 100 mW / cm 2 and more preferably 1 mW / cm 2 to 20 mW / cm 2 .

[0023] In some embodiments, in step S13, the conditions of the microbial electrosynthesis system are: temperature 15 °C to 40 °C, pH value 5.5 to 8.5, and electrode potential -0.4 V to -1.2 V (relative to Ag / AgCl);

[0024] In some embodiments, in step S13, the concentration of the CdS@PDDA-modified suspended microorganisms in the electrochemical system is 10 6 to 10 9 CFU / mL.

[0025] In one embodiment, step S13: inoculate the modified microorganisms obtained in step S12 into a microbial electrosynthesis system to construct a photo-assisted microbial electrosynthesis system; after the inoculation is completed, control the optical density (OD value) of the catholyte to be maintained between 0.3 and 0.5. Then apply a cathodic potential (-1.1 V vs. Ag / AgCl) and turn on the light source (light intensity 2 - 10 mW / cm 2 ), and under the synergistic action of photo-electricity, synchronous synthesis of acetic acid by the biocathode and suspended microorganisms is achieved.

[0026] Furthermore, the target products include but are not limited to acetic acid, methane, ethanol, CO, and H2.

[0027] The second aspect of the present invention lies in providing a photo-electricity synergistic carbon dioxide capture and conversion system, specifically a method for enhancing the supply of reducing power of suspended microorganisms to improve the potential of CO2 capture and conversion and its supporting system. The system includes:

[0028] (a) A microbial electrosynthesis reactor: including a cathode chamber and an anode chamber separated by a proton membrane, and configured with a working electrode, a counter electrode, and a reference electrode;

[0029] (b) Add CdS@PDDA-modified suspended microorganisms to the cathode chamber, where CdS@PDDA is used to provide photo-generated electrons for the suspended microorganisms under light conditions, enhance the reducing power, and capture and convert CO2.

[0030] (c) A lighting device for providing a light source;

[0031] (d) An aeration device for introducing CO2.

[0032] In one embodiment, the system includes a cathode chamber and an anode chamber (separated by a proton exchange membrane), a working electrode (using a three-dimensional cyanobacteria electrode), a counter electrode (using a carbon felt electrode), a reference electrode (Ag / AgCl), and an incandescent lamp. After the inoculation is completed, CO2 is introduced. Then apply a cathodic potential (-1.1 V vs. Ag / AgCl) and turn on the light source, and under the synergistic action of photo-electricity, synchronous synthesis of acetic acid by the biocathode and suspended microorganisms is achieved. In a preferred embodiment, the light intensity is 2 mW / cm 2 .

[0033] In some embodiments, the configuration method of the lighting device includes: the lighting device directly irradiates, or introduces the light source into the reactor interior through an optical fiber.

[0034] In one embodiment, the cathode and anode of the microbial electrosynthesis system are both 3.5 cm × 3.5 cm × 0.5 cm in size, and the working volume of the cathode chamber is 170 ml.

[0035] In some embodiments, the CO2 aeration rate in the aeration device is 2 - 40 ml / min; in a preferred embodiment, the CO2 aeration rate is 20 ml / min.

[0036] Furthermore, the operating temperature range of the photo-assisted MES is 15°C to 40°C, and more preferably 25 - 35°C;

[0037] Furthermore, the pH value is 5.5 to 8.5, and more preferably 6.5 - 7.5.

[0038] The second aspect of the present invention lies in providing the application of the method or the system in the field of industrial waste gas treatment and resource utilization.

[0039] Beneficial effects:

[0040] (1) The present invention first provides a method for photoelectrically synergistically enhancing the reducing power of suspended microorganisms. In the microbial electrosynthesis system, photocatalytic materials are used to modify the suspended microorganisms to obtain modified microorganisms that can accept photogenerated electrons under light illumination conditions; under the synergistic action of light illumination and electrochemical conditions, the reducing power of the suspended microorganisms is significantly enhanced, overcoming the limitation of insufficient electron supply in traditional MES.

[0041] (2) The microbial-CdS@PDDA hybrid system prepared based on the present invention provides stable photogenerated electrons. Combining with the electric field driving of MES, the photoelectric synergistic effect increases the CO2 conversion efficiency by 55.6% (compared with a single MES system); compared with the microbial-CdS hybrid system, the CO2 conversion efficiency increases by 38.1%.

[0042] (3) The system provided by the present invention is reasonably designed. After optimizing the light illumination and electrochemical conditions, the electron transfer efficiency and system stability are significantly improved, suitable for long-term operation, and no attenuation is observed after continuous operation for 20 days.

[0043] (4) The technical solution of the present invention uses visible light for driving, combined with the adaptability of the mixed bacteria system, the process is green and efficient, with significant technical advantages and broad application prospects. It meets the carbon neutrality goal. Description of the Drawings

[0044] The drawings are used to provide a further understanding of the present application and constitute a part of the specification. They are used together with the embodiments of the present application to explain the present application and do not constitute a limitation to the present application. In the drawings:

[0045] Figure 1 Schematic diagram of the process of enhancing microbial electrosynthesis of acetic acid by photo - electro - synergy;

[0046] Figure 2 It is the acetic acid synthesis performance of the microbial - CdS@PDDA hybrid system under different CdS@PDDA addition amounts in Example 1;

[0047] Figure 3 It is the acetic acid synthesis performance of the microbial - CdS@PDDA hybrid system under different light intensities in Example 2;

[0048] Figure 4 It is the acetic acid synthesis performance of Example 3, Comparative Example 1 and Comparative Example 2;

[0049] Figure 5 Scanning electron microscope images of the microbial - CdS@PDDA hybrid system (a) and the microbial - CdS hybrid system (b);

[0050] Figure 6 Zeta potential of CdS, CdS@PDDA and the microbial surface;

[0051] Figure 7 Acetic acid synthesis effects of the microbial - CdS hybrid system and the microbial - CdS@PDDA hybrid system. Detailed implementation manners

[0052] To make the above - mentioned objects, features and advantages of the present invention more obvious and understandable, the following will describe the detailed implementation manners of the present invention in combination with the examples / comparative examples of the specification. Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific examples disclosed below.

[0053] For the experiments involved in the following examples, if not specified clearly, they can be carried out according to the conventional conditions or methods in the art.

[0054] As Figure 1 shown, it is a schematic diagram of the photo - electro - synthesis system of the present invention; it includes an H - type electrolytic cell composed of a cathode chamber and an anode chamber, and the cathode chamber and the anode chamber are separated by a proton exchange membrane. An anode is arranged in the anode chamber, and a cathode is arranged in the cathode chamber. The anode and the cathode are respectively connected to the positive and negative electrodes of a power supply. A suspension microbial system modified with CdS@PDDA is added to the cathode chamber, and under the action of light, photogenerated electrons are generated to improve the electron transfer efficiency of the suspension microorganisms.

[0055] The microorganism used in the example is a Gram-negative bacterium, which is derived from a microbial electrosynthesis reactor that has been operating for a long time with anaerobic granular sludge from a sewage treatment plant as the inoculum.

[0056] Preparation of the microorganism-CdS@PDDA hybrid system in Example 1

[0057] This example aims to study the effect of different CdS@PDDA concentrations on the acetic acid synthesis efficiency of a photo-assisted microbial electrochemical system (MES) to determine the optimal concentration and improve the system performance. The specific implementation steps are as follows:

[0058] (1) 2.35 g of cadmium nitrate tetrahydrate, 1.3 g of polyvinylpyrrolidone, 0.9 g of thioacetamide, and 0.8 g of hexamethylenetetramine were successively added to a round-bottom flask containing 40 mL of ethylenediamine, and magnetically stirred for 60 minutes until the solution was homogeneous. Subsequently, the mixed solution was transferred to a 100 mL polytetrafluoroethylene-lined autoclave and reacted at a constant temperature of 180 °C for 24 hours. After the reaction, it was naturally cooled to room temperature, centrifuged at 6000 rpm for 5 minutes to separate the precipitate, washed 5 times with deionized water and anhydrous ethanol respectively, and dried in a vacuum oven at 60 °C for 10 hours to obtain cadmium sulfide (CdS) nanorods. Then, 50 mg of CdS was dispersed in 50 mL of a 0.5 M NaCl solution containing 3.5 wt% of poly(diallyldimethylammonium chloride) (PDDA), vigorously stirred for 6 hours, washed with deionized water and dried to obtain the surface-modified CdS@PDDA nanomaterial.

[0059] (2) CdS@PDDA was added to the bacterial solution with OD 600 = 0.5 at concentrations of 50 mg / L, 100 mg / L, 200 mg / L, and 300 mg / L respectively, and oscillated and cultured at 30 °C and 150 rpm for 5 hours to form a microorganism-CdS@PDDA hybrid system. This system was placed in a serum bottle with a working volume of 170 mL and reacted under the conditions of a light intensity of 2 mW / cm 2 , a temperature of 30 °C, a pH of 7.0, and a CO2 flow rate of 20 mL / min. Samples were taken every 24 hours to measure the acetic acid concentration.

[0060] The medium components include: sodium bicarbonate 2.5 g / L, L-cysteine 0.25 g / L, ammonium chloride 0.25 g / L, sodium dihydrogen phosphate 4.4 g / L, disodium hydrogen phosphate 2.6 g / L, trace element solution 1 mL, vitamin solution 1 mL;

[0061] The experimental results are as Figure 2As shown: The acetic acid concentration gradually accumulates with the progress of the reaction time, and first increases and then decreases with the increase of the CdS@PDDA concentration. After 7 days of reaction, the acetic acid concentration is 0.4 g / L when the addition of CdS@PDDA is 50 mg / L, 0.55 g / L when it is 100 mg / L, reaches the peak value of 0.69 g / L when it is 200 mg / L, and drops to 0.45 g / L when it is 300 mg / L. Among them, the acetic acid production rate is the highest when the addition of CdS@PDDA is 200 mg / L, indicating that the photogenerated electron transfer efficiency is the best at this concentration. The analysis shows that the supply of photogenerated electrons is insufficient at low concentrations (such as 50 mg / L), and the efficiency decreases due to the inhibition of microbial activity at high concentrations (such as 300 mg / L).

[0062] Example 2 Photocatalytic Performance of the Microorganism-CdS@PDDA Hybrid System

[0063] This example aims to study the effect of different light intensities on the acetic acid synthesis efficiency of the microorganism-CdS@PDDA hybrid system (CdS@PDDA concentration 200 mg / L) to determine the optimal light intensity and optimize the system performance. The specific implementation steps are as follows:

[0064] Prepare the CdS@PDDA nanomaterial according to the method of Example 1 and add it to the bacterial solution with OD 600 = 0.5 at a concentration of 200 mg / L, and shake and culture at 30 °C and 150 rpm for 5 hours to construct the microorganism-CdS@PDDA hybrid system. Place this system in a photoreactor, and set the light intensities to 0.5, 2.0, 5.0, and 10.0 mW / cm 2 (wavelength 400 - 700 nm), and the remaining conditions are: temperature 30 °C, pH 7.0, CO2 flow rate 20 mL / min, and sample the acetic acid concentration every 24 hours for determination.

[0065] The experimental results are as Figure 3 shown: The light intensity significantly affects the acetic acid production rate. After 72 hours of reaction, the acetic acid production rate is 0.28 g / L at 0.5 mW / cm 2 , reaches the peak value of 0.58 g / L at 2.0 mW / cm 2 , drops to 0.50 g / L at 5.0 mW / cm 2 , and further drops to 0.45 g / L at 10.0 mW / cm 2 . Among them, the acetic acid production rate is the highest at 2.0 mW / cm 2 , indicating that the generation and microbial utilization efficiency of photogenerated electrons reach the best balance at this light intensity. When the light intensity is too low (such as 0.5 mW / cm 2 ), the supply of photogenerated electrons is insufficient, and when it is too high (such as 10.0 mW / cm 2 ), the efficiency may decrease due to light inhibition or charge recombination.

[0066] Example 3 Photoelectrochemical Synergistic Enhancement of Microbial Electrosynthesis System

[0067] This example aims to study the effect of the photoelectrochemical synergistic effect on acetic acid synthesis performance under electrochemical assistance in a photo-assisted microbial electrosynthesis system. The specific implementation steps are as follows:

[0068] Prepare the CdS@PDDA nanomaterial according to the method of Example 1, add it to the bacterial solution with OD600 = 0.5 at a concentration of 150 mg / L, and shake and culture at 30 °C and 150 rpm for 5 hours to construct a microbial-CdS@PDDA hybrid system. Transfer this system to a two-chamber MES reactor. The working electrode is a cyanobacteria-based three-dimensional porous electrode (3.5 cm × 3.5 cm × 0.5 cm), the counter electrode is a carbon felt electrode (3.5 cm × 3.5 cm × 0.5 cm), and the reference electrode is an Ag / AgCl electrode. Add the culture medium containing the hybrid system (170 mL) to the cathode chamber, and add 0.1 M phosphate buffer solution (pH 7.0) to the anode chamber. Then, introduce nitrogen into the cathode chamber for 25 min to provide an anaerobic environment. Finally, connect the reactor to a potentiostat and operate it under the condition that the cathode potential is constant at -1.1 V (vs. Ag / AgCl). The system is supplied with CO2 (flow rate 20 mL / min), the light intensity is 2.0 mW / cm 2 (wavelength 400 - 700 nm), the temperature is 30 °C, and the pH is 7.0. Sample and measure the acetic acid concentration every 24 hours, and monitor the current density and electron transfer efficiency.

[0069] Comparative Example 1

[0070] This comparative example studies the acetic acid synthesis efficiency of a photo-assisted microbial electrosynthesis system coupled with MES and a microbial-CdS@PDDA hybrid system under open-circuit conditions. The specific implementation steps are as follows:

[0071] Prepare the CdS@PDDA nanomaterial according to the method of Example 1, add it to the bacterial solution with OD 600 = 0.5 at a concentration of 150 mg / L, and shake and culture at 30 °C and 150 rpm for 5 hours to construct a microbial-CdS@PDDA hybrid system. Transfer this system to a two-chamber MES reactor, where the working electrode is a cyanobacteria-based three-dimensional porous electrode (size: 3.5 cm × 3.5 cm × 0.5 cm), the counter electrode is a carbon felt electrode (size: 3.5 cm × 3.5 cm × 0.5 cm), and the reference electrode is an Ag / AgCl electrode; add the culture medium containing the hybrid system (170 mL) to the cathode chamber with a diameter of 5 cm and a height of 10 cm, and add 0.1 M phosphate buffer solution (pH 7.0) to the anode chamber with a diameter of 5 cm and a height of 10 cm.

[0072] Subsequently, nitrogen gas was introduced into the cathode chamber for 25 minutes to provide an anaerobic environment. The system was supplied with CO2 (flow rate 20 mL / min), the light intensity was 2.0 mW / cm 2 (wavelength 400 - 700 nm), the temperature was 30 °C, the pH was 7.0, and it was kept in an open circuit state (no applied potential). Samples were taken every 24 hours to measure the acetic acid concentration.

[0073] Comparative Example 2 Microbial Electrocatalysis System

[0074] In this comparative example, the acetic acid synthesis efficiency of the MES without the CdS@PDDA photocatalytic system was studied. The specific implementation steps are as follows:

[0075] A two-chamber MES reactor was constructed. The working electrode was a cyanobacteria-based three-dimensional porous electrode (3.5 cm × 3.5 cm × 0.5 cm), the counter electrode was a carbon felt electrode (3.5 cm × 3.5 cm × 0.5 cm), and the reference electrode was an Ag / AgCl electrode

[0076] 100 mL of OD 600 = 0.5 bacterial solution (without CdS@PDDA) was added to the Ф5 cm × 10 cm cathode chamber, and 0.1 M phosphate buffer solution (pH 7.0) was added to the Ф5 cm × 10 cm anode chamber.

[0077] Nitrogen gas was introduced into the cathode chamber for 25 minutes to provide an anaerobic environment. Subsequently, the reactor was connected to a potentiostat, and the cathode potential was kept constant at -1.1 V (vs. Ag / AgCl). The system was supplied with CO2 (flow rate 20 mL / min), there was no light, the temperature was 30 °C, the pH was 7.0. Samples were taken every 24 hours to measure the acetic acid concentration, and the current density and electron transfer efficiency were monitored.

[0078] Comparative Example 3 Microorganism-CdS Hybrid System

[0079] The CdS nanomaterial was prepared according to the method of Example 1 and added to the OD 600 = 0.5 bacterial solution at a concentration of 200 mg / L, and cultured with shaking at 30 °C and 150 rpm for 5 hours to construct a microorganism-CdS hybrid system. This system was placed in a photoreactor, and the light intensities were set to 0.5, 2.0, 5.0, and 10.0 mW / cm 2 (wavelength 400 - 700 nm), and the other conditions were: temperature 30 °C, pH 7.0, CO2 flow rate 20 mL / min. Samples were taken every 24 hours to measure the acetic acid concentration.

[0080] The experimental results of Example 3, Comparative Example 1, and Comparative Example 2 are as Figure 4 shown. Among them, in Example 3, the cathode potential was -1.1 V (vs. Ag / AgCl) and the light intensity was 2.0 mW / cm 2Under these conditions, the acetic acid concentration reached 2.3 g / L after 3 days of reaction, and the current density stabilized at 1.4 mA / cm 2 ; after 20 days of reaction, the acetic acid concentration could reach 9.8 g / L. In Comparative Example 1, the acetic acid production rate was low under open circuit conditions, and the acetic acid concentration was 1.0 g / L after 20 days of reaction; in Comparative Example 2, the acetic acid concentration was 6.3 g / L after 20 days of reaction.

[0081] In Example 3, the acetic acid production rates were increased by 880% and 55.6% compared with Comparative Example 1 and Comparative Example 2, respectively. It shows that the photo - electro - synergy significantly enhances the CO2 conversion efficiency. CdS@PDDA generates photo - generated electrons under light illumination, and the applied potential accelerates the electron transfer, jointly promoting the efficient synthesis of acetic acid. Moreover, the system has excellent stability. During long - term operation, the acetic acid production rate continuously increases within 20 days without attenuation.

[0082] As Figure 5 (a) shows that in the microorganism - CdS@PDDA hybrid system, the CdS@PDDA nanomaterials are uniformly loaded on the surface of the microorganism. As Figure 5 (b) shows, in the microorganism - CdS hybrid system, the loading effect of CdS on the surface of the microorganism is poor, indicating the deficiency of its integration performance.

[0083] The Zeta potential test results of CdS, CdS@PDDA and the microorganism surface are as Figure 6 shown: which further supports the above conclusion. Both CdS and the microorganism surface carry negative charges, while after modification with PDDA, the surface potential of CdS is significantly increased. It shows that CdS@PDDA can form a closer combination with the microorganism through electrostatic interaction, thus improving the performance of the hybrid system.

[0084] As Figure 7 shown: the acetic acid synthesis performance of the microorganism - CdS hybrid system is poor; after 24 hours of reaction, the acetic acid production rate of the microorganism - CdS hybrid system is only 0.14 g / L, and the cumulative acetic acid concentration is 0.42 g / L after 168 hours; while the acetic acid production rate of the microorganism - CdS@PDDA hybrid system of the present invention is as high as 0.58 g / L. Compared with CdS alone, the hybrid ability of CdS@PDDA and the microorganism is stronger and it is easier to achieve effective combination.

[0085] In summary, the present invention relates to a method for enhancing the reducing power of suspended microorganisms by photo - electro - synergy to improve the CO2 capture and conversion potential, especially applicable to the technology of efficiently capturing and converting CO2 by suspended microorganisms in MES to produce high - value products. The solution of the present invention effectively solves the problem of low CO2 conversion efficiency caused by insufficient reducing power of suspended microorganisms in MES through photo - electro - synergy.

[0086] In the present invention, by introducing polydimethyldiallylammonium chloride to positively modify the surface of CdS, a CdS@PDDA composite is formed, converting the surface potential of CdS from negative charge to positive charge. Thus, a stable hybrid system is formed with the negatively charged surface of Gram-negative bacteria through electrostatic interaction, eliminating the charge repulsion between CdS and microorganisms and significantly enhancing the interfacial binding force between the two. As a result, the modified microorganisms can directly receive the electrons generated by photocatalysis under light, effectively compensating for the defect of insufficient electron supply in traditional MES. Further, in the present invention, a hybrid system is formed by modifying Gram-negative bacteria with CdS@PDDA, and combined with the stable electron flow provided by the external electric field of MES, a photo-electro synergistic system is constructed. This system makes full use of the advantages of efficient light energy capture of photocatalysis technology and stable electron supply of electrochemistry, significantly improving the electron transfer efficiency of suspended microorganisms, thereby enhancing the CO2 conversion efficiency and product stability, providing an innovative solution for the green conversion of CO2 and the efficient production of high-value-added chemicals, featuring high efficiency, environmental protection and sustainability, and being applicable to the field of industrial waste gas treatment and resource utilization.

[0087] 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 preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the present invention.

Claims

1. A method for capturing and converting CO2 by a photo-electrochemical synergistic enhanced microbial electrosynthesis system, characterized in that, Modify the suspended microorganisms in the system with CdS@PDDA, and photoelectrochemically reduce CO2 based on the modified suspended microorganisms to synthesize target products; Specifically, it includes the following steps: S11. Provide a microbial electrosynthesis system; S12. Use CdS@PDDA to perform single-bacteria modification on the suspended microorganisms in the microbial electrosynthesis system to obtain CdS@PDDA-modified suspended microorganisms; S13. Place the CdS@PDDA-modified suspended microorganisms prepared in step S12 in the cathode chamber of the microbial electrosynthesis system, introduce CO2, and capture and convert CO2 to generate target products under the conditions of an applied voltage and light irradiation.

2. The method for capturing and converting CO2 according to claim 1, wherein The modification method in step S12 is: co-culture CdS@PDDA with suspended microorganisms to make CdS@PDDA attach to the surface of suspended microorganisms; The co-culture conditions were as follows: CdS@PDDA was added to the bacterial solution with an OD 600 of 0.3 - 0.5 at a concentration of 50 - 400 mg / L, and the mixture was cultured with shaking for 2 - 12 hours.

3. The method for capturing and converting CO2 according to claim 1, wherein The suspended microorganisms are microorganisms capable of reducing CO2, including but not limited to one or more of acetic acid-synthesizing microorganisms, methanogens, or hydrogen-producing bacteria.

4. The method for capturing and converting CO2 according to claim 1, wherein In step S13, the light source has a wavelength of 200 nm to 800 nm, preferably a light source of 400 nm to 700 nm; and / or, the light intensity is 0.1 mW / cm 2 to 100 mW / cm 2 of the light source, preferably 1 mW / cm 2 to 20 mW / cm 2 .

5. The method for capturing and converting CO2 according to claim 1, wherein In step S13, the conditions of the microbial electrosynthesis system are: temperature 15°C to 40°C, pH value 5.5 to 8.5, and electrode potential -0.4 V to -1.2 V.

6. The method for capturing and converting CO2 according to claim 1, characterized in that, In step S13, the concentration of the CdS@PDDA-modified suspended microorganisms is 10 6 to 10 9 CFU / mL.

7. The method for capturing and converting CO2 according to claim 1, characterized in that, The target products include acetic acid, methane, ethanol, CO, and H2.

8. A carbon dioxide capture and conversion system for implementing the method according to any one of claims 1-7, characterized in that, It includes: (a) A microbial electrosynthesis reactor: including a cathode chamber and an anode chamber separated by a proton membrane, and equipped with a working electrode, a counter electrode, and a reference electrode; (b) Add CdS@PDDA-modified suspended microorganisms to the cathode chamber, where CdS@PDDA is used to provide photogenerated electrons for the suspended microorganisms under light irradiation conditions; (c) A lighting device for providing a light source; (d) An aeration device for introducing CO2.

9. The carbon dioxide capture and conversion system according to claim 8, wherein The configuration method of the lighting device includes: the lighting device directly irradiates, or introduces the light source into the reactor interior through an optical fiber. The application of the method according to any one of claims 1-7, or the system according to any one of claims 8-9, in the field of industrial waste gas treatment and resource utilization.

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