CN115851697B - Complex enzyme electrointegration catalyst, preparation method thereof and carbon dioxide reduction method - Google Patents
Complex enzyme electrointegration catalyst, preparation method thereof and carbon dioxide reduction method Download PDFInfo
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Abstract
The invention provides a composite enzyme electric integrated catalyst which comprises a catalyst carrier and a composite biological enzyme, wherein the catalyst carrier is a three-way electric catalyst which has a mesoporous structure and is doped with Bi element, and the three-way electric catalyst has a two-dimensional nano-sheet structure, and the transverse dimension of the three-way electric catalyst is not more than 10 mu m. The method utilizes the characteristics of robustness and reusability of the three-way electrocatalyst and the selectivity and activity of biological enzyme to realize the efficient conversion of carbon dioxide into organic acid and organic alcohol through an electrocatalytic means. Compared with the method for producing ethanol and acetic acid by simulating the fermentation process in C.ljungdahlii bacteria by using the complex enzyme, the complex enzyme electrointegration catalyst path does not need to adopt formate dehydrogenase and carbon monoxide dehydrogenase, and part of gaseous raw materials are converted into liquid organic matters for reaction in the reaction process, so that the raw material utilization efficiency of the whole reaction is provided.
Description
Technical Field
The invention relates to the technical field of enzyme catalysis, in particular to a composite enzyme electrointegration catalyst for reducing carbon dioxide into organic acid and organic alcohol and a preparation method thereof.
Background
CO from tail gas of industrial emission 2 As raw material, the catalyst is prepared into ethanol/acetic acid by electrochemical reduction reaction under the assistance of an electrocatalyst, so that CO can be reduced 2 And the pollution problem that the tail gas is discharged into the atmosphere is solved, and finally, the carbon recycling economic target is realized.
However, CO 2 Electrocatalytic reduction has multiple reaction paths at the same time, and the variety of products is large, so that the reaction selectivity is limited. CO 2 Reduction can be carried out by 2, 4, 6, 8, 12 or more electron transfer pathways, thereby producing a wide variety of reduction products, some of which are selective, e.g., 2 electrons are converted to CO; some reduction products, such as ethanol (12 electron pathway)/acetic acid (8 electron pathway) and the like, which need to adopt multiple electron transfer pathways, show poor selectivity, while ethanol and acetic acid are important organic chemical raw materials, so how to control the electrocatalytic reduction reaction to realize CO 2 Highly selective production of acetic acid/ethanol as CO 2 The high-value utilization is brought, and the method becomes a problem to be solved urgently in the industry.
Intracellular multi-enzyme systems are capable of maintaining structural organization while maintaining extremely high efficiency and high selectivity. Enzymes can efficiently synthesize many complex products, and can also perform challenging reactions that many artificial catalysts cannot achieve, such as photosynthesis, nitrogen fixation, and water splitting. In nature, multiple enzymes are linked together to perform a coupling reaction in cells; for example, in 1987, clostridium ljungdahlii found a gram-positive rod-shaped anaerobic bacterium (i.e., c.ljungdahlii bacterium) with the ability to ferment carbon monoxide and hydrogen to ethanol and acetic acid; since then, synthesis gas fermentation (CO/CO 2 And H 2 Mixtures of (d) has made significant progress in research.
Has been studied by using CO and CO 2 And H 2 Ethanol and acetic acid are produced by simulating the fermentation process in C.ljungdahlii bacteria with complex enzymes as substrates, which pathway employs formate dehydrogenase, carbon monoxide dehydrogenase, leucovorin synthase, methyltransferase, phosphotransacetylaseThe complex action of enzymes, acetate kinase, acetaldehyde dehydrogenase and alcohol dehydrogenase generates acetic acid and alcohol through acetyl-CoA pathway, and the specific metabolic pathway is shown in FIG. 5.
The raw materials adopting the path are in a gaseous state, so that the problem of low direct utilization rate of the raw materials exists, and the industrialized application of the raw materials is limited.
Therefore, there have been a number of studies to make the use of enzyme catalysis in biotechnology processes more advantageous, one of which is immobilization technology. The immobilization technology greatly simplifies the operation of the biocatalyst and the control of the reaction process, and simultaneously enhances the stability of the enzyme under storage and operating conditions. Immobilization allows for easy separation of the enzyme from the product, ensuring that protein contamination of the product is minimized or completely avoided.
In addition to the ease of separation of the enzyme from the reaction mixture, enzyme immobilization also significantly reduces the cost of the enzyme and enzymatic products. Insolubilizing the enzyme by attachment to the substrate also brings about some additional advantages, such as a rapid stopping of the reaction by removing the enzyme from the reaction solution. In addition, it also helps to efficiently recover and reuse expensive enzymes and allows their use in continuous fixed bed operations. Thus, the use of enzyme immobilization techniques can increase the productivity of biocatalysts and enhance their properties, making them more attractive for a variety of applications.
It has been found that the use of a three-way electrocatalyst as a carrier in combination with a bio-enzyme catalyst to form a Hybrid Chemical Enzymatic Heterogeneous Catalyst (HCEHC) is an attractive strategy to run chemical enzymatic reactions using immobilized enzyme technology. Combining a three-way electrocatalyst and a biological enzyme in one system can take advantage of both catalysts, enzyme selectivity and activity can be combined with robustness and reusability of inorganic catalysts, and ongoing reactions can be controlled with the aid of a carrier, resulting in a fine tuning system with many industrial and pharmaceutical applications.
Disclosure of Invention
The invention aims to provide a composite enzyme electrointegration catalyst, which is used for realizing the efficient conversion of carbon dioxide into organic acid and organic alcohol by an electrocatalytic means by utilizing the characteristics of robustness and reusability of a ternary electrocatalyst and the selectivity and activity of biological enzymes. Compared with the method for producing ethanol and acetic acid by simulating the fermentation process in C.ljungdahlii bacteria by using the complex enzyme, the complex enzyme electrointegration catalyst path does not need to adopt formate dehydrogenase and carbon monoxide dehydrogenase, and part of gaseous raw materials are converted into liquid organic matters for reaction in the reaction process, so that the raw material utilization efficiency of the whole reaction is provided.
In order to solve the technical problems, the invention provides a composite enzyme electric integrated catalyst which comprises a catalyst carrier and a composite biological enzyme, wherein the catalyst carrier is a three-way electric catalyst which has a mesoporous structure and is doped with Bi element, and the three-way electric catalyst has a two-dimensional nano-sheet structure, and the transverse dimension of the three-way electric catalyst is not more than 10 mu m.
Wherein the complex biological enzyme comprises leucovorin synthetase, methyltransferase, phosphotransacetylase, acetate kinase, acetaldehyde dehydrogenase and alcohol dehydrogenase.
Wherein the preparation method of the catalyst carrier comprises the following steps of,
firstly, preparing a two-dimensional lamellar mesoporous structure NiCuAl catalyst, dissolving Cu precursor salt, ni precursor salt and Al precursor salt in deionized water, and then dropwise adding an aqueous solution of a precipitant into a salt solution until the mixed solution is alkaline to obtain a mixed solution;
secondly, dissolving Bi precursor salt with a certain mass into deionized water, dropwise adding a salt solution of the Bi precursor into the mixed solution obtained in the first step, stirring, and aging;
and thirdly, filtering the mixed solution after aging in the second step, centrifugally washing to pH=7, and drying at 60 ℃ to obtain the mesoporous structure bismuth-doped electrocatalyst.
Wherein, in the first step, cu of the Cu precursor salt 2+ Ni of ion and Ni precursor salt 2+ The ratio of the amount of ionic species is 1:0.5-2.
Wherein, in the first step, cu 2+ Ion, ni 2+ The sum of the amounts of the ionic species is Al of the Al precursor salt 3+ 2-4 times the amount of ionic species.
Wherein, in the first step, bi in the Bi precursor salt 3+ The amount of ionic substances and Al 3+ The mass ratio of the ions is 0.1-0.7.
The invention also provides a preparation method of the composite enzyme electrointegration catalyst, which comprises the following steps:
firstly, stirring leucovorin synthetase, methyltransferase, phosphotransacetylase, acetate kinase, acetaldehyde dehydrogenase, alcohol dehydrogenase, the ternary electrocatalyst serving as a catalyst carrier, bovine serum albumin and acrylamide in PBS buffer solution to obtain a mixed solution, adding absolute ethyl alcohol into the mixed solution, and continuously stirring to obtain a precipitation reaction;
secondly, adding glutaraldehyde solution into the mixed solution in the first step for crosslinking reaction, wherein the solution is kept in a stirring state;
and thirdly, centrifuging and drying the mixed solution in the second step to obtain the composite enzyme-electric integrated catalyst.
Wherein the dosage mass ratio of the methyltransferase, the phosphotransacetylase, the acetate kinase, the acetaldehyde dehydrogenase, the ethanol dehydrogenase and the leucovorin synthase is 0.8-1.2:1, and the amount of any one of the methyltransferase, phosphotransacetylase, acetate kinase, acetaldehyde dehydrogenase, and alcohol dehydrogenase cannot be 0.
The invention also provides an electrode coated with the composite enzyme electrointegration catalyst, wherein the catalyst loading of the electrode is 1-2mg/cm 2 。
The invention also provides a method for electrocatalytic reduction of carbon dioxide into organic acids and organic alcohols, wherein CO is introduced into an electrocatalytic system 2 The gas, the anode electrode is commercial Pt electrode, the cathode electrode adopts the composite enzyme electric integrated catalyst electrode, the applied voltage is-1.2V (vs. Ag/AgCl), and the CO is driven by the electric catalyst in the composite enzyme electric integrated catalyst 2 Conversion to formic acid and CO, followed by conversion of the substrate to the desired product organic acid/alcohol by a range of enzymes.
The beneficial effects of the invention are that
The inventionThe carrier of the provided composite enzyme electro-integrated catalyst is nickel-copper-aluminum ternary electro-catalyst which has a two-dimensional lamellar mesoporous structure and is doped with bismuth elements, and a cross-linked enzyme aggregate preparation method is adopted to enable a series of composite enzymes to be loaded on the carrier, on one hand, the thickness of a two-dimensional nano sheet is about one nanometer, the transverse dimension is unequal from submicron to tens of microns, the composite enzyme electro-integrated catalyst has higher specific surface area and more active sites, in addition, the mesoporous structure of the ternary electro-catalyst can provide efficient mass transfer and microcosmic high specific surface area, and the cross-linked enzymes can be dispersed, so that the utilization of raw materials is enhanced in a mode of increasing active sites of the ternary electro-catalyst, and meanwhile, the CO is enhanced by introducing the bismuth elements 2 The selectivity of reducing to formic acid further improves the utilization rate of raw materials.
The bismuth-doped nickel-copper-aluminum ternary electrocatalyst with the two-dimensional lamellar mesoporous structure prepared by the invention can effectively mix gaseous CO at first 2 Is dissolved in electrolyte to improve CO 2 Provides a large amount of raw materials for a subsequent series of reactions; second, it will convert CO from the traditional formate dehydrogenase/CO dehydrogenase 2 The step of converting into formic acid/CO is replaced by electrocatalysis, so that the industrial difficulty of low utilization rate of gaseous raw materials in the biological fermentation industry is avoided, a large amount of raw materials are provided for subsequent fermentation of biological enzymes, and the yield is further improved.
3. The invention combines biological enzyme and ternary electrocatalyst (i.e. immobilized enzyme) to make enzyme directly use formic acid and CO generated by electrocatalyst, which avoids the problem of low raw material utilization rate caused by directly using gaseous raw material, and simultaneously the immobilized enzyme can easily separate enzyme from product, thereby minimizing the probability of pollution of product and remarkably reducing the cost of enzyme and enzymatic product. Therefore, the combination of the enzyme and the three-way electrocatalyst physically limits the enzyme in a specific space region and retains the catalytic activity thereof, so that the enzyme can be repeatedly and continuously used, the operation of the biocatalyst and the control of the reaction process are simplified, and the stability of the enzyme under the storage and operation conditions is enhanced.
Drawings
FIG. 1 is an SEM image of an electrocatalyst according to example 1;
FIG. 2 is a graph showing the physical adsorption and desorption of the supported electrocatalysts of example 1, comparative example 1, and comparative example 4;
FIG. 3 is an SEM image of the electrocatalyst of comparative example 1;
FIG. 4 is an SEM image of the electrocatalyst of comparative example 4;
FIG. 5 is a diagram showing the metabolic pathways for ethanol and acetic acid production by a complex enzyme to simulate the fermentation process in C.ljungdahlii bacteria.
Detailed Description
The invention provides a composite enzyme electric integrated catalyst which comprises a catalyst carrier and a composite biological enzyme, wherein the catalyst carrier is a three-way electric catalyst which has a mesoporous structure and is doped with Bi element, and the three-way electric catalyst has a two-dimensional nano-sheet structure, and the transverse dimension of the three-way electric catalyst is not more than 10 mu m.
The complex biological enzyme is specifically leucovorin synthetase, methyltransferase, phosphotransacetylase, acetate kinase, acetaldehyde dehydrogenase and alcohol dehydrogenase.
The preparation method of the catalyst carrier specifically comprises the following steps:
firstly, preparing a two-dimensional lamellar mesoporous structure NiCuAl catalyst, dissolving Cu precursor salt, ni precursor salt and Al precursor salt in deionized water, and then dropwise adding an aqueous solution of a precipitant into a salt solution until the mixed solution is alkaline to obtain a mixed solution;
wherein the concentrations of Cu precursor salt, ni precursor salt and Al precursor salt are controlled to be 1-9M, and Cu 2+ Ion, ni 2+ The ratio of the amount of ionic species is 1:0.5-2, cu 2+ Ion, ni 2+ The sum of the amounts of ionic species is Al 3+ 2-4 times the amount of ionic species;
wherein the precipitant is one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate and ammonia water, and the total substance amount is 3-5 times of the total substance amount of the precursor salt in the first step.
Wherein the pH value of the alkaline mixed solution is controlled between 9 and 11.
Secondly, dissolving Bi precursor salt with a certain mass into deionized water, dropwise adding a salt solution of the Bi precursor into the mixed solution obtained in the first step, stirring, and aging;
wherein Bi is 3+ The amount of ionic substances and Al 3+ The mass ratio of the ionic substances is preferably 0.1 to 0.7:1, and controlling the salt solution concentration of the Bi precursor to be between 0.5 and 2M;
and thirdly, filtering the mixed solution after aging in the second step, centrifugally washing to pH=7, and drying at 60 ℃ to obtain the mesoporous structure bismuth-doped electrocatalyst.
In the first step, the Cu precursor salt is one or more of copper nitrate, copper chloride and copper acetate.
In the first step, the Al precursor salt is one or more of aluminum nitrate, aluminum chloride and aluminum acetate.
In the first step, the Ni precursor salt is one or more of nickel nitrate, nickel chloride and nickel acetate.
The aging time in the second step is preferably 12-24h, and the aging temperature is preferably 60-70 ℃.
The subsequent calcination of the electrocatalyst in an air atmosphere at 300-500 ℃ does not destroy the inherent mesoporous structure, and can increase the disorder degree and thus enhance the catalytic activity.
The invention also provides a preparation method of the composite enzyme electrointegration catalyst, which comprises the following steps:
firstly, stirring leucovorin synthetase, methyltransferase, phosphotransacetylase, acetate kinase, acetaldehyde dehydrogenase, alcohol dehydrogenase, electrocatalyst, bovine serum albumin and acrylamide in PBS buffer solution to obtain a mixed solution, then adding absolute ethyl alcohol into the mixed solution, and obtaining a precipitation reaction in continuous stirring;
wherein, the dosage mass ratio of the methyltransferase, the phosphotransacetylase, the acetate kinase, the acetaldehyde dehydrogenase, the alcohol dehydrogenase and the leucovorin synthase is 0.8-1.2:1, and the amount of any one of the methyltransferase, phosphotransacetylase, acetate kinase, acetaldehyde dehydrogenase, and alcohol dehydrogenase cannot be 0.
Wherein the mass of the PBS buffer solution is 100-400 times of that of the leucovorin synthetase.
Wherein the concentration of each substance in the PBS buffer solution is 0.137M/L NaCl, 0.0027M/L KCl and 0.01M/L Na 2 HPO 4 、0.0018M/L KH 2 PO 4 ,pH=7.3。
Wherein, the mass dosage of the absolute ethyl alcohol is 50-150% of the mass of the PBS buffer solution.
Secondly, adding glutaraldehyde solution into the mixed solution in the first step for crosslinking reaction, wherein the solution is kept in a stirring state;
wherein, the dosage volume of glutaraldehyde is 80% -120% of the volume of PBS buffer solution.
And thirdly, centrifuging and drying the mixed solution in the second step to obtain the composite enzyme-electric integrated catalyst.
In the first step, the precipitation time is 0.5-3 h, and the precipitation temperature is 20-40 ℃.
In the second step, the crosslinking reaction time is 10-60 mins.
In the first step, the mass ratio of the protein content of the bovine serum albumin to the complex enzyme is 0.3-4:1.
the complex enzyme electric integrated catalyst takes bismuth-doped nickel-copper-aluminum ternary mesoporous material as a carrier, and utilizes glutaraldehyde to crosslink protein, immobilized leucovorin synthase, methyltransferase, phosphotransacetylase, acetate kinase, acetaldehyde dehydrogenase and alcohol dehydrogenase, and finally realizes carbon dioxide reduction at a cathode.
The invention also provides an electrode coated with the composite enzyme electrointegration catalyst, the electrode is square carbon fiber paper, the side length is between 1 and 2cm, and the catalyst loading capacity of the electrode is preferably 1 to 2mg/cm 2 。
The invention also provides a method for electrocatalytic reduction of carbon dioxide into organic acids and organic alcohols, wherein CO is introduced into an electrocatalytic system 2 The gas, electrolyte of cathode chamber in electro-catalysis system is sodium sulfate solution of 0.5M, 1M sodium hydroxide solution is added in anode pool, anode electrode is commercial Pt electrode, cathode electrode adopts the above composite enzyme electro-integrated catalyst electrode, applied voltage is-1.2V (vs. Ag/AgCl), and CO is maintained 2 The flow rate of the catalyst is 20mL/min, and the CO is driven by the electric catalyst in the composite enzyme electric integrated catalyst 2 Conversion to formic acid and CO, followed by conversion of the substrate to the desired product organic acid/alcohol by a range of enzymes.
Wherein the organic acid is acetic acid and the organic alcohol is ethanol.
Wherein the voltage is between-0.5V and-3V (Ag/AgCl is used as reference electrode), and the current density is 80mA/cm 2 -440mA/cm 2 。
The following examples and drawings are used to describe embodiments of the present invention in detail, thereby solving the technical problems by applying the technical means to the present invention, and realizing the technical effects can be fully understood and implemented accordingly.
Example 1
The embodiment relates to an enzyme-electric integrated catalyst, which comprises a carrier, wherein the carrier is a nickel-copper-aluminum ternary electric catalyst which has a two-dimensional lamellar mesoporous structure and is doped with bismuth, and a series of compound enzymes immobilized on the carrier by a crosslinking method are loaded on the carrier.
The specific synthesis steps are as follows:
step 1) preparing a NiCuAl catalyst with a two-dimensional lamellar mesoporous structure: firstly, dissolving 0.5mol of copper nitrate trihydrate, 0.5mol of nickel nitrate hexahydrate and 0.33mol of aluminum nitrate nonahydrate in 500ml of deionized water, stirring until the solution is clear, then dropwise adding 2M sodium hydroxide aqueous solution into the salt solution until the pH value of the mixed solution is 9, and aging for 14 hours in an oil bath at 60 ℃;
step 2) 0.1mol of bismuth nitrate pentahydrate is dissolved in 100ml of deionized water, stirred until the solution in step 1 is clarified, and aged in an oil bath at 60 ℃ for 14h.
Step 3) filtering the mixed solution, centrifugally washing to pH=7, drying at 60 ℃ to obtain the mesoporous-structure bismuth-doped electrocatalyst, wherein an SEM image of the mesoporous-structure bismuth-doped electrocatalyst is shown in figure 1, and the lateral dimension of the catalyst prepared by the embodiment is not more than 10 mu m, a physical adsorption-desorption curve of the catalyst is shown in figure 2, and the curve in the figure is an IV-type isothermal curve, so that the mesoporous-structure bismuth-doped electrocatalyst is proved to be a mesoporous material.
Step 4) stirring 10mg of leucovorin synthase, 10mg of methyltransferase, 10mg of phosphotransacetylase, 10mg of acetate kinase, 10mg of acetaldehyde dehydrogenase, 10mg of alcohol dehydrogenase, 0.4g of electrocatalyst, 200mg of bovine serum albumin and 50mg of acrylamide in 20ml of PBS buffer to obtain a mixed solution, adding absolute ethyl alcohol into the mixed solution, and stirring for 30 min;
step 5) adding 2ml of glutaraldehyde solution into the mixed solution in the step one, and stirring for 30 min;
step 6) centrifuging and drying the mixed solution in the step 5 to obtain the integrated enzyme electrocatalyst named enzyme@Bi/NiCuAl-cat.
Comparative example 1
The comparative example relates to an enzyme-electric integrated catalyst, which comprises a carrier, wherein the carrier is a nickel-copper-aluminum ternary electric catalyst with a two-dimensional lamellar mesoporous structure, and a series of compound enzymes immobilized on the carrier by a crosslinking method are loaded on the carrier.
The specific synthesis steps are as follows:
step 1) preparing a NiCuAl catalyst with a two-dimensional lamellar mesoporous structure: firstly, dissolving 0.5mol of copper nitrate trihydrate, 0.5mol of nickel nitrate hexahydrate and 0.33mol of aluminum nitrate nonahydrate in 500ml of deionized water, stirring until the solution is clear, then dropwise adding 2M sodium hydroxide aqueous solution into the salt solution until the pH value of the mixed solution is 9, and aging for 14 hours in an oil bath at 60 ℃;
step 2) filtering the mixed solution, centrifugally washing to pH=7, and drying at 60 ℃ to obtain the mesoporous-structure bismuth-doped electrocatalyst, wherein an SEM (scanning electron microscope) diagram is shown in fig. 3, and a physical adsorption-desorption curve is shown in fig. 2, so that the mesoporous-structure bismuth-doped electrocatalyst is proved to be a mesoporous material.
Step 3) stirring 10mg of leucovorin synthase, 10mg of methyltransferase, 10mg of phosphotransacetylase, 10mg of acetate kinase, 10mg of acetaldehyde dehydrogenase, 10mg of alcohol dehydrogenase, 0.4g of electrocatalyst, 200mg of bovine serum albumin and 50mg of acrylamide in 20ml of PBS buffer to obtain a mixed solution, adding absolute ethyl alcohol into the mixed solution, and stirring for 30 min;
step 4) adding 2ml of glutaraldehyde solution into the mixed solution in the step one, and stirring for 30 min;
step 5) centrifuging and drying the mixed solution in the step 5 to obtain the integrated enzyme electrocatalyst named enzyme@NiCuAl-cat.
Comparative example 2
The present comparative example relates to an enzyme-electric integrated catalyst comprising a carrier, the carrier being a bismuth-nickel-copper-supported non-mesoporous structure electrocatalyst, and a series of complex enzymes immobilized on the carrier by a crosslinking method being supported on the carrier.
Step 1) BiNiCuAlOx catalyst: firstly, dissolving 0.5mol of copper nitrate trihydrate, 0.1mol of bismuth nitrate pentahydrate, 0.5mol of nickel nitrate hexahydrate and 0.33mol of non-mesoporous alumina powder in 500ml of deionized water, stirring, and aging for 14 hours in an oil bath at 60 ℃;
and 2) filtering the mixed solution, washing to pH=7, drying at 60 ℃ for 12 hours, and placing the obtained sample in a muffle furnace at 400 ℃ for calcining for 2 hours to obtain the BiNiCuAlOx catalyst electrocatalyst.
Step 3) stirring 10mg of leucovorin synthase, 10mg of methyltransferase, 10mg of phosphotransacetylase, 10mg of acetate kinase, 10mg of acetaldehyde dehydrogenase, 10mg of alcohol dehydrogenase, 0.4g of electrocatalyst, 200mg of bovine serum albumin and 50mg of acrylamide in 20ml of PBS buffer to obtain a mixed solution, adding absolute ethyl alcohol into the mixed solution, and stirring for 30 min;
step 4) adding 2ml of glutaraldehyde solution into the mixed solution in the step one, and stirring for 30 min;
step 5) centrifuging and drying the mixed solution in the step 5 to obtain the integrated enzyme electrocatalyst named enzyme@BiNiCuAlOx-cat.
Comparative example 3
The present comparative example relates to an enzyme-electric integrated catalyst comprising a carrier, which is an electric catalyst of alumina having a mesoporous structure and carrying bismuth-nickel-copper, and on which a series of complex enzymes immobilized on the carrier by a crosslinking method are carried.
Step 1) BiNiCuAlOx catalyst: firstly, dissolving 0.5mol of copper nitrate trihydrate, 0.1mol of bismuth nitrate pentahydrate, 0.5mol of nickel nitrate hexahydrate and 0.33mol of mesoporous alumina powder in 500ml of deionized water, stirring, and aging for 14 hours in an oil bath at 60 ℃;
and 2) filtering the mixed solution, washing to pH=7, drying at 60 ℃ for 12 hours, and placing the obtained sample in a muffle furnace at 400 ℃ for calcining for 2 hours to obtain the BiNiCu@AlOx catalyst electrocatalyst.
Step 4) stirring 10mg of leucovorin synthase, 10mg of methyltransferase, 10mg of phosphotransacetylase, 10mg of acetate kinase, 10mg of acetaldehyde dehydrogenase, 10mg of alcohol dehydrogenase, 0.4g of electrocatalyst, 200mg of bovine serum albumin and 50mg of acrylamide in 20ml of PBS buffer to obtain a mixed solution, adding absolute ethyl alcohol into the mixed solution, and stirring for 30 min;
step 5) adding 2ml of glutaraldehyde solution into the mixed solution in the step one, and stirring for 30 min;
step 6) centrifuging and drying the mixed solution in the step 5 to obtain the integrated enzyme electrocatalyst named enzyme@BiNiCu@AlOx-cat.
Comparative example 4
The same preparation method as in the step 1-3 in the example 1 is adopted to synthesize the electrocatalyst Bi/NiCuAl-cat, the SEM image of which is shown in figure 4, and the physical adsorption and desorption curve of which is shown in figure 2, so that the material is proved to be mesoporous.
Comparative example 5
The specific procedure is substantially the same as in steps 4-6 of example 1, except that a mesoporous structure of gamma-Al is used 2 O 3 （γ-Al 2 O 3 No catalytic activity) instead of the electrocatalyst from step 4 of example 1, the sample obtained was designated enzyme@al 2 O 3 -cat。
The test conditions for the samples in examples and comparative examples are as follows:
firstly preparing a cathode electrode, mixing 10mg of sample catalyst, 1ml of isopropanol and 100ul of nafion solution, ultrasonically vibrating for 30min, then dripping the prepared mixture on carbon paper, and controlling the load of the catalystThe amount was 1mg/cm 2 In an electrocatalytic system (H-cell), the electrolyte in the cathode chamber was 0.5M sodium sulfate solution (100 mL) and then CO was added 2 (flow rate 20 mL/min) into the cathode chamber; 1M sodium hydroxide solution (100 mL) is added into an anode pool of an electrocatalytic system, the anode electrode is a commercial Pt electrode, the applied voltage is-1.2V (vs. Ag/AgCl), and the test time is 24 hours, so that the enzyme electrocatalytic integrated catalyst CO is realized 2 And (5) reduction. The test data for each sample are shown in Table 1 below:
comparative example 6
Reference (renewability)&Sustainable Energy Reviews, 2011, 15 (9), 4255-4273) and (Bioresource Technology,2022,3632, 127906) the experimental conditions in which c.ljungdahlii bacteria were cultivated to convert CO2 to acetic acid and ethanol. C. ljungdahlii c.ljungdahlii bacteria were cultivated at 37 ℃ using DSMZ 879 medium; this culture step follows anaerobic media preparation and culture techniques. In the case of bicarbonate as the sole carbon source (without fructose, cysteine and yeast extract), resazurin as redox indicator, na 2 The growth incubated in DSMZ medium 879 with S as reducing agent was subjected to Microbial Electrochemical Synthesis (MES) experiments.
Before the start of the MES test, the test period of the MES was sterilized. In the cathodic compartment of the MES reactor (H-cell), modified DSMZ 879 medium was used as growth medium and catholyte. The commercial carbon paper was used as a cathode electrode, and the rest of the test conditions were the same as in example 1, and the test results are shown in table 1.
As can be seen from the data of example 1 and comparative example 1 above, the electrocatalyst prepared in comparative example 1 performs electrocatalytic CO 2 Reduction, the absence of Bi doping, of comparative example 1 only produced CO, but not formic acid, and further the enzyme supported on the catalyst of comparative example 1 did not obtain raw material to produce acetic acid/ethanol, which demonstrated that the incorporation of bismuth enhanced CO 2 The selectivity of reducing to formic acid further improves the raw material utilizationAnd (5) utilization rate.
As can be seen from the data of the above example 1 and comparative example 2, comparative example 3, the catalyst of comparative example 2 having the same elemental composition as the catalyst of example 1 but a non-mesoporous structure and the catalyst of comparative example 3 having a mesoporous structure have the function of converting CO 2 The ability to convert to acetic acid/ethanol, but with much lower acetic acid/ethanol yields per unit time than in example 1, demonstrates from the side that the mesoporous structure provides efficient mass transfer and microscopic high specific surface area, and disperses the cross-linked enzyme to enhance utilization of the feedstock in a manner that increases its active sites.
As can be seen from comparison of the experimental results of example 1 and comparative example 4, only CO was reacted with the mesoporous structure of the two-dimensional lamellar Bi/NiCuAl-cat 2 The ability to convert to formic acid and CO does not allow further conversion of the feedstock to acetic acid/ethanol.
As can be seen from comparison of the experimental results of example 1 and comparative example 5, the complex enzyme can only further convert formic acid and CO into acetic acid/ethanol, and cannot directly convert CO 2 。
As can be seen from the comparison of the experimental results of the embodiment 1 and the comparative example 6, the enzyme-electricity integrated catalyst and the system provided by the invention can effectively avoid the industrial difficulty of low utilization rate of the gaseous raw materials in the biological fermentation industry, provide a large amount of raw materials for subsequent fermentation of biological enzymes, and further improve the yield. Thanks to the CO which will be gaseous 2 Is dissolved in alkaline electrolyte to improve CO 2 Provides a large amount of raw materials for the subsequent series of reactions, and is hardly formed by the method of comparative example 6.
As can be seen from the comparison, the carrier of the composite enzyme electrointegration catalyst prepared by the invention is a two-dimensional layered material with a mesoporous structure, has higher specific surface area and more active sites, and meanwhile, the mesoporous structure can provide efficient mass transfer and microcosmic high specific surface area, and can disperse the crosslinked enzyme so as to increase the active sites of the enzyme to enhance the utilization of raw materials. The enzyme catalyst prepared by the invention combines the characteristics of easy recovery and reuse and high selectivity of the enzyme catalyst by combining the electrocatalyst, and can realize the high-efficiency production of acetic acid/ethanol.
All of the above-described primary implementations of this intellectual property are not intended to limit other forms of implementing this new product and/or new method. Those skilled in the art will utilize this important information and the above modifications to achieve a similar implementation. However, all modifications or adaptations belong to the reserved rights based on the new products of the invention.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the invention in any way, and any person skilled in the art may make modifications or alterations to the disclosed technical content to the equivalent embodiments. However, any simple modification, equivalent variation and variation of the above embodiments according to the technical substance of the present invention still fall within the protection scope of the technical solution of the present invention.
Claims (4)
1. A preparation method of a composite enzyme electrointegration catalyst is characterized by comprising the following steps: the preparation method of the composite enzyme electrointegration catalyst comprises the following steps of,
firstly, stirring leucovorin synthase, methyltransferase, phosphotransacetylase, acetate kinase, acetaldehyde dehydrogenase, alcohol dehydrogenase, a three-way electrocatalyst which is used as a catalyst carrier and has a mesoporous structure and is doped with Bi element, bovine serum albumin and acrylamide under a PBS buffer solution to obtain a mixed solution, adding absolute ethyl alcohol into the mixed solution, and obtaining a precipitation reaction in continuous stirring, wherein the dosage mass ratio of the methyltransferase, phosphotransacetylase, acetate kinase, acetaldehyde dehydrogenase, alcohol dehydrogenase and leucovorin synthase is (0.8-1.2): 1, and the dosage of any one of the methyltransferase, the phosphotransacetylase, the acetate kinase, the acetaldehyde dehydrogenase and the alcohol dehydrogenase cannot be 0;
secondly, adding glutaraldehyde solution into the mixed solution in the first step for crosslinking reaction, wherein the solution is kept in a stirring state;
thirdly, centrifuging and drying the mixed solution obtained in the second step to obtain the composite enzyme-electricity integrated catalyst;
the preparation method of the catalyst carrier comprises the following steps of,
step a, preparing a two-dimensional lamellar mesoporous structure NiCuAl catalyst, dissolving Cu precursor salt, ni precursor salt and Al precursor salt in deionized water, then dropwise adding an aqueous solution of a precipitant into a salt solution until the mixed solution is alkaline to obtain a mixed solution, wherein Cu of the Cu precursor salt is prepared by 2+ Ni of ion and the Ni precursor salt 2+ The ratio of the amount of ionic species is 1:0.5-2, said Cu 2 + Ion, ni 2+ The sum of the amounts of the ionic species is Al of the Al precursor salt 3+ 2-4 times the amount of ionic species;
step b, dissolving Bi precursor salt with certain mass into deionized water, dropwise adding a Bi precursor salt solution into the mixed solution obtained in the step a, stirring, and aging, wherein Bi in the Bi precursor salt is added 3+ The amount of ionic species and the Al 3+ The mass ratio of the ionic substances is 0.1-0.7;
step c, filtering the aged mixed solution in the step b, centrifugally washing to pH=7, and drying at 60 ℃ to obtain the mesoporous structure bismuth-doped electrocatalyst;
the Cu precursor salt is one or more of copper nitrate, copper chloride and copper acetate;
the Al precursor salt is one or more of aluminum nitrate, aluminum chloride and aluminum acetate;
the Ni precursor salt is one or more of nickel nitrate, nickel chloride and nickel acetate;
the precipitant is one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate and ammonia water.
2. The composite enzyme electrointegration catalyst prepared by the preparation method of the composite enzyme electrointegration catalyst of claim 1, which is characterized in that: the catalyst carrier is a ternary electrocatalyst which has a mesoporous structure and is doped with Bi elements, the ternary electrocatalyst is of a two-dimensional nano-sheet structure, and the transverse dimension of the ternary electrocatalyst is not more than 10 mu m.
3. Coating claim 2The electrode of the complex enzyme electric integrated catalyst is characterized in that: the catalyst loading of the electrode is 1-2mg/cm 2 。
4. A process for electrocatalytic reduction of carbon dioxide to acetic acid, formic acid and ethanol, characterized by: CO is introduced into an electrocatalytic system 2 The gas, the positive electrode is commercial Pt electrode, the negative electrode adopts the complex enzyme electrointegration catalyst electrode of claim 3, ag/AgCl is used as reference electrode, and the applied voltage is-1.2V.
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