Copper-nickel alloy nanoparticle catalyst, preparation method thereof and application of copper-nickel alloy nanoparticle catalyst in microbial electrosynthesis

Abstract

The invention discloses a copper-nickel alloy nanoparticle catalyst and a preparation method and application thereof in microbial electrosynthesis, and belongs to the technical field of energy conversion and microbial electrosynthesis, the preparation method comprises the following steps: dissolving Cu (NO3) 2 and Ni (NO3) 2 in a mixed solution of water and ethanol, dispensing the mixed solution on a carbon-based material, drying the surface by baking and drying overnight, and obtaining the copper-nickel alloy nanoparticle catalyst. A copper-nickel loaded carbon-based material is obtained; calcining the copper-nickel loaded carbon-based material in air at 350-450 DEG C to obtain a copper-nickel oxide loaded carbon-based material; and reducing the carbon-based material loaded with the copper-nickel oxide in flowing H2 at 500-600 DEG C to obtain the copper-nickel alloy nanoparticle catalyst. According to the method, the volatile fatty acid can be synthesized by taking CO2 as a raw material, and the product yield and the Faraday efficiency are relatively high. The method is simple to operate, mild in condition and low in cost, and has relatively high environmental benefits.

Description

Technical Field

[0001] The present invention relates to the technical fields of energy conversion and microbial electrosynthesis, and particularly relates to a copper-nickel alloy nanoparticle catalyst, a preparation method thereof, and an application thereof in microbial electrosynthesis. Background Art

[0002] CO 2 The C=O bond of CO has a high bond energy of 750 kJ mol-1 and relatively high thermodynamic stability. With the development of technology, CO 2 has been able to be converted into fuels such as CO, CH 4 and high-value-added chemicals such as butyric acid and isobutanol through chemical, light, electricity, biological and other means. Therefore, carbon capture, utilization and storage technologies involving resource utilization have become a research hotspot at present.

[0003] Microbial electrosynthesis (MES) is a new energy conversion technology first proposed in 2010. This system couples electrocatalysis and biological conversion, and can use renewable electric energy to drive microorganisms to convert water and CO 2 into one-carbon and multi-carbon compounds at room temperature, and is expected to achieve the conversion of CO 2 into high-value-added products. Moreover, it combines the characteristics of biochemical conversion and electrochemical conversion, and has the advantages of renewable catalyst, mild reaction conditions, high conversion efficiency, and the ability to synthesize multi-carbon products.

[0004] In recent years, research on improving the production efficiency of volatile fatty acids in microbial electrosynthesis systems has mainly focused on the development of new cathode materials, the screening of cathode microorganisms, and the online separation of products. Metal modification of the biocathode of microbial electrosynthesis can, on the one hand, improve the conductivity of the cathode and promote electron transfer at the biological and abiotic interfaces; on the other hand, it can enhance the electrocatalytic reduction of CO 2Or a hydrogen evolution reaction occurs to generate electron donors such as formic acid or hydrogen gas, providing greater reducing power for the microbial electrochemical synthesis system. Since Ni and Cu have suitable work functions and binding strengths for hydrogen atoms, their special electronic structures make them a very promising hydrogen evolution electrocatalyst. However, most existing studies focus on the synthesis of small molecule carbon-containing products (such as methane), lacking research on the electron transfer efficiency and product generation efficiency at the biological and abiotic interfaces. Traditional microbial electrosynthesis systems usually face difficulties such as poor activity of the conductive biofilm at the biological-abiotic interface, slow electron-proton transfer rate, and difficult carbon and hydrogen migration inside and outside the cells. Moreover, the binder present in the cathode material will hinder electron transport, reduce the material conductivity, and have poor material stability. Long-term immersion in the solution will cause catalyst exfoliation and cathode structure collapse. More importantly, the selectivity and yield of multi-carbon products still need to be improved. Therefore, designing a biocathode electrocatalyst with excellent hydrogen evolution performance, low cost, and good biocompatibility is an urgent problem to be solved in the existing technology. Summary of the Invention

[0005] In order to solve the problems existing in the related technologies, the purpose of the present invention is to provide a copper-nickel alloy nanoparticle catalyst, its preparation method and application in microbial electrosynthesis. By loading a self-synthesized copper-nickel alloy nanoparticle on the cathode of a microbial electrosynthesis reactor, the yield and Faraday efficiency of multi-carbon products are improved. This method is simple to operate, has mild conditions, low raw material costs, and has high environmental benefits.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A preparation method of a copper-nickel alloy nanoparticle catalyst, comprising the following steps: Dissolve Cu(NO 3 ) 2 and Ni(NO 3 ) 2 in a mixed solution of water and ethanol, drop-coat it on a carbon-based material, bake it on the surface and dry it overnight to obtain a carbon-based material loaded with copper and nickel; Calcinate the carbon-based material loaded with copper and nickel in air at 350-450 °C to obtain a carbon-based material loaded with copper-nickel oxides; Reduce the carbon-based material loaded with copper-nickel oxides in flowing H 2 at 500-600 °C to obtain a copper-nickel alloy nanoparticle catalyst.

[0008] Further, the molar ratio of Cu(NO 3 ) 2 and Ni(NO 3 ) 2 is 0-4:1.

[0009] Further, the carbon-based material is one or more of carbon felt, carbon cloth, graphite rod, and activated carbon.

[0010] Further, the concentration by volume percentage of the flowing H 2 is 10%, the carrier gas is Ar, and the flow rate is 50 - 70 mL / min; the reduction time of the flowing H 2 is 2 - 4 h.

[0011] The present invention also provides a copper-nickel alloy nanoparticle catalyst prepared by the above preparation method.

[0012] The present invention also provides the application of the above copper-nickel alloy nanoparticle catalyst in microbial electrosynthesis.

[0013] The present invention also provides a microbial electrosynthesis system. The cathode of the microbial electrosynthesis device includes a carbon-based material loaded with the above copper-nickel alloy nanoparticle catalyst, and a fully domesticated electroactive microbial consortium is inoculated in the cathode culture medium of the microbial electrosynthesis system.

[0014] Further, the microbial electrosynthesis system includes a two-chamber reactor, and the cathode and anode chambers of the two-chamber reactor are separated by a proton exchange membrane.

[0015] Further, the anode includes a material for oxidizing the electrolyte, and the material for oxidizing the electrolyte is one or more of stainless steel, platinum, and ruthenium-iridium-titanium mesh.

[0016] Further, the microbial electrosynthesis system further includes an electrolyte solution, the electrolyte solution includes a cathode electrolyte solution and an anode electrolyte solution, the cathode electrolyte solution includes a cathode culture medium and a fully domesticated electroactive microbial consortium, and the anode electrolyte solution includes an anode culture medium.

[0017] The biocatalyst used in the microbial electrosynthesis system of the present invention is an electroactive microorganism, and an external power source is required to provide electrons for the microbial conversion of CO 2 In this reaction system, the microbial electrosynthesis reactor provides electrons for the system through an applied voltage. The electrons are transferred to the cathode through an external circuit, and a hydrogen evolution reaction occurs at the cathode. The electroactive microorganisms present in the cathode chamber and the biofilm on the cathode surface use hydrogen as an electron donor to reduce CO 2 to organic matter, completing the biological fixation of CO 2 . Due to the synergistic effect among diverse microorganisms, CO 2 can generate multi-carbon products through different characteristic reaction pathways. The copper-nickel alloy nanoparticles can provide a carrier for electron transfer for the electroactive microorganisms on the cathode surface by catalyzing the generation of hydrogen on the cathode, thereby accelerating the electron transfer rate at the bio-non-biological interface, and further increasing the yield and Faraday efficiency of multi-carbon products. Before startup, the oxygen in the cathode chamber is exhausted, and CO 2; Apply a voltage to the anode and cathode with an externally applied DC power supply, and use a rotor to continuously magnetically stir during operation.

[0018] Further, the electrodes include: a cathode and an anode. The cathode uses a carbon-based material, on which a copper-nickel alloy is loaded, and microorganisms are attached to the surface to form a biofilm, constituting a biocathode; the anode can be a material that can cause the electrolyte to undergo an oxidation reaction, and the material can be stainless steel, platinum, ruthenium-iridium titanium mesh, etc.

[0019] Further, the medium is composed of substances such as nitrogen source, trace elements, minerals, and vitamins, and the pH is adjusted to 6.5.

[0020] Further, the cathode inoculum is electroactive anaerobic microorganisms, preferably a mixed flora obtained by domestication of the remaining sludge from anaerobic fermentation in an electrified environment.

[0021] Further, the CO 2 in the microbial electrosynthesis reactor is allowed to exist in different forms, such as CO 2 gas, HCO 3 - 、CO 3 2- etc.

[0022] Further, the operating temperature condition of the reaction system is 37 ± 1 °C.

[0023] Further, the voltage intensity applied by the external power supply is 1 - 2.5 V.

[0024] Further, the acetic acid production rate of the electroactive microbial mixed flora loaded with the copper-nickel alloy cathode material is ≥ 750 mg / L, and the Faraday efficiency is ≥ 85%.

[0025] Beneficial effects

[0026] Compared with the traditional microbial electrosynthesis system that uses CO 2 to synthesize acetic acid with low added value, in the present invention, due to the existence of different functional microbial communities on the biological carrier, the enrichment of dominant flora can be carried out, so as to more efficiently synthesize multi-carbon products such as volatile fatty acids.

[0027] Using copper-nickel alloy as a catalyst promotes the evolution of hydrogen on the surface of the cathode in the system, strengthens the indirect electron transfer process of using hydrogen as an electron donor to transfer electrons from the electrode to microorganisms, and improves the product yield and Faraday efficiency of the carbon chain elongation reaction. Description of the drawings

[0028] Figure 1 Linear voltammogram curves of the cathode materials for Examples 1 - 3 and Comparative Examples 1 - 3;

[0029] Figure 2 Current density diagrams for the operation processes of Examples 1 to 3 and Comparative Examples 1 to 3. Detailed implementation manners

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] Example 1

[0032] Construction of a bioelectrochemical reaction device:

[0033] In this experiment, a two-chamber microbial electrochemical reactor was used. The volume was approximately 200 mL for both chambers, and the anode and cathode chambers were separated by a proton exchange membrane. The proton exchange membrane was soaked in deionized water for at least 24 h before use to fully wet the proton exchange membrane, which was more conducive to the passage of protons.

[0034] A carbon felt was used as the cathode, a platinum electrode was used as the anode, and a Ag / AgCl (vs. SHE) reference electrode was placed in the cathode electrolysis chamber. The anode electrolyte was 150 mL of a culture medium, and the components of the culture medium were: 50 mM phosphate buffer, 0.31 g / L NH 4 Cl, 0.2 g / L MgCl 2 ·6H 2 O, 0.13 g / L KCl, and the pH was adjusted to 6.5. The cathode electrolyte was 60 mL of an inoculum (a fully domesticated mixed electroactive microbial flora) and 90 mL of a culture medium, and the components of the culture medium were 50 mM phosphate buffer, 0.31 g / L NH 4 Cl, 0.2 g / L MgCl 2 ·6H 2 O, 0.13 g / L KCl, 0.05 g / L yeast powder, 10 g / L methane inhibitor, 0.05 g / L Na 2 SO 4 , 4.2 g / L NaHCO 3 , trace elements, vitamins, and the pH was adjusted to 6.5. The culture temperature was 37 ± 1°C.

[0035] In this experiment, all potential data were relative to the Ag / AgCl reference electrode, and the voltage output and current monitoring of the bioelectrochemical system were both carried out using an electrochemical workstation.

[0036] Modification of the cathode material:

[0037] Dissolve 0.1 mmol of Cu(NO 3 ) 2 and 0.05 mmol of Ni(NO 3 ) 2 in a mixed solution of 1.5 mL of water and 1.5 mL of ethanol, drop-coat it on a 2×2 cm carbon felt, and dry the surface with an infrared heating lamp, then dry it overnight at 60 °C to obtain a sample of the copper-nickel salt material;

[0038] Calcine the copper-nickel-loaded carbon-based material in air at 400 °C for 4 h to obtain copper-nickel oxide;

[0039] Reduce the copper-nickel oxide in a flowing 10% H 2 (the carrier gas is Ar, and the flow rate is 60 mL / min) at 550 °C for 3 h to obtain a copper-nickel alloy catalyst, denoted as Cu2Ni1@CF (Cu2Ni1 NP@CF).

[0040] Operation of the bioelectrochemical reactor:

[0041] (1) To exclude the influence of the residual culture medium on the experiment, centrifuge the enriched inoculum at 4000 r for 5 min, pour off the upper-layer culture medium, add physiological saline (0.9% NaCl), mix evenly, and centrifuge again;

[0042] (2) Before the experiment, introduce nitrogen into the cathode chamber of the H-type reactor for 10 min to exhaust the oxygen in the cathode chamber (4.2 g / L of NaHCO 3 is used as the only carbon source, and CO 2 is not introduced in this part of the experiment).

[0043] (3) At 37 °C, gradually increase the voltages on both the cathode and anode sides in steps (1 V → 1.5 V → 2.0 V → 2.5 V). Use a data collector to measure the voltage (U, V) across the external resistor (1 Ω) every 10 s to calculate the current density (I, A / m 2 , relative to the biofilm area of 4 cm 2 ). At the same time, use a data collector to measure the potential difference between the cathode and the Ag / AgCl reference electrode every 10 s.

[0044] (4) The experiment process includes two cycles, each cycle is 18 days. The first cycle is mainly used to enrich electroactive microorganisms at the cathode. At the end of the first cycle, replace the new culture medium.

[0045] Sampling and testing:

[0046] (1)Each time, 2 mL of the cathode solution was taken to detect the pH change. After centrifugation and filtration, the resulting fermentation broth was used to determine the change in the concentration of volatile fatty acids (1 mL plus 50 μL of formic acid) by gas chromatography, and the Faraday efficiency was calculated.

[0047] (2)After the experiment, electrochemical tests (CV, LSV: H-type reactor) were performed on the cathode.

[0048] As can be seen from Table 1, Example 1 achieved the highest acetic acid concentration (797.65 ± 37.97 mg / L) and the maximum Faraday efficiency (89.0 ± 4.2%) during the operation of the system.

[0049] For the test of the hydrogen evolution performance during the electrochemical reaction process, the corresponding overpotential at a current density of 10 mA / cm 2 is commonly used to evaluate the quality of the catalyst. As Figure 1 can be seen, Example 1 had the smallest overpotential corresponding to a current density of 10 mA / cm 2 , proving that Example 1 had excellent hydrogen evolution performance.

[0050] As Figure 2 can be seen, after the applied voltage was kept constant at 2.5 V, due to the gradual increase in electroactive microorganisms attached to the biocathode and the consumption of substances in the culture medium, the current density decreased slightly.

[0051] Example 2

[0052] On the basis of Example 1, in the cathode material modification step, different ratios of copper-nickel alloy were loaded. That is, 0.075 mmol of Cu(NO 3 ) 2 and 0.075 mmol of Ni(NO 3 ) 2 were dissolved in a mixed solution of 1.5 mL of water and 1.5 mL of ethanol, and then drop-coated on a 2×2 cm carbon felt. The rest were the same as in Example 1, and the cathode material with a copper-nickel molar ratio of 1:1 was obtained, denoted as Cu1Ni1@CF (Cu1Ni1 NP@CF).

[0053] As Figure 2 can be seen, Example 2 had the maximum current density during the operation.

[0054] Example 3

[0055] On the basis of Example 1, in the cathode material modification step, different ratios of copper-nickel alloy were loaded. That is, 0.12 mmol of Cu(NO 3 ) 2 and 0.03 mmol of Ni(NO 3 ) 2Dissolved in a mixed solution of 1.5 mL of water and 1.5 mL of ethanol, and drop-coated on a 2×2 cm carbon felt. The rest was the same as in Example 1, and a cathode material with a copper-nickel molar ratio of 4:1 was obtained, denoted as Cu4Ni1@CF (Cu4Ni1 NP@CF).

[0056] Comparative Example 1

[0057] The difference between this example and Example 1 is that the cathode material was not modified, and the copper-nickel alloy nanoparticle catalyst used in the present invention was not adopted. That is, pure carbon felt was used as the cathode material, denoted as CF, and the bioreactor was operated according to the reactor and operating conditions of Example 1.

[0058] As can be seen from Table 1, the acetic acid concentration that could be achieved in Comparative Example 1 during the system operation was 436.72±32.67 mg / L, and the Faraday efficiency was 65.1±4.9%.

[0059] Comparative Example 2

[0060] The difference between this example and Example 1 is that in the cathode material modification step of Comparative Example 2, only copper was loaded as a single metal material. That is, 0.15 mmol of Cu(NO 3 ) 2 was dissolved in a mixed solution of 1.5 mL of water and 1.5 mL of ethanol, drop-coated on a 2×2 cm carbon felt, and the rest of the steps were the same as in Example 1. A cathode material loaded only with copper was obtained, denoted as Cu@CF (Cu NP@CF), and the bioreactor was operated according to the reactor and operating conditions of Example 1.

[0061] As can be seen from Table 1, the acetic acid concentration that could be achieved in Comparative Example 2 during the system operation was 315.30±32.42 mg / L, and the Faraday efficiency was 40.5±2.8%. As Figure 2 can be seen, the current density of Comparative Example 2 was similar to that of Comparative Example 1, and it had a lower current density during operation.

[0062] Comparative Example 3

[0063] The difference between this example and Example 1 is that in the cathode material modification step of Comparative Example 3, only nickel was loaded as a single metal material. Instead, 0.15 mmol of Ni(NO 3 ) 2 was dissolved in a mixed solution of 1.5 mL of water and 1.5 mL of ethanol, drop-coated on a 2×2 cm carbon felt, and the rest of the steps were the same as in Example 1. A cathode material loaded only with nickel was obtained, denoted as Ni@CF (NiNP@CF), and the bioreactor was operated according to the reactor and operating conditions of Example 1.

[0064] As can be seen from Table 1, the acetic acid concentration that can be achieved during the operation of Comparative Example 3 is 548.76 ± 26.55 mg / L, and the Faraday efficiency is 67.8 ± 3.3%.

[0065] The acetic acid concentration and Faraday efficiency results of the fermentation broths obtained in Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 1.

[0066] Table 1 Product concentration and Faraday efficiency of Examples 1 to 6 during operation

[0067]

[0068] Table 1 shows the acetic acid concentration and Faraday efficiency of Examples 1 to 3 and Comparative Examples 1 to 3 during operation. During the operation of the system, the acetic acid in Examples 1 and 2 reached 797.65 ± 37.97 mg / L and 651.56 ± 24.46 mg / L respectively, which are 1.8 and 1.5 times that of Comparative Example 1. Compared with Comparative Example 1, the Faraday efficiency of Example 1 increased by 36.71%. Comparative Examples 1 to 3 have lower acetic acid and Faraday efficiency, mainly because of the mismatch between the hydrogen evolution reaction of the electrode intrinsic and the biofilm electron utilization process, and the total amount of microorganisms attached to the electrode surface is limited, resulting in lower acetic acid production and Faraday efficiency.

[0069] Figure 1 For the linear sweep voltammograms of the operation processes of Examples 1 to 3 and Comparative Examples 1 to 3, the hydrogen evolution performance of the cathode material was tested. The overpotential corresponding to Example 1 at a current density of 10 mA / cm 2 is the smallest, showing excellent hydrogen evolution performance. At the same time, Examples 1 to 2 exhibit higher current densities (-0.4 to -0.8 V), indicating that the charge transfer on the surface of the copper-nickel alloy nanoparticle catalyst electrode enhances the chemical reaction on the electrode surface and can provide stronger reducing power for the microbial electrosynthesis system. Compared with Examples 1 to 2, the electrodes loaded with no copper-nickel alloy nanoparticles and single-metal alloy nanoparticles lead to inhibited electron transfer processes and lack sufficient electron storage capacity, so Comparative Examples 1 to 3 have lower current densities.

[0070] Figure 2 For the current density diagrams of the operation processes of Examples 1 to 3 and Comparative Examples 1 to 3. Due to different cathode materials, there are obvious differences in current density. The current density of Comparative Example 1 is the lowest. After loading single-metal alloy nanoparticles, the current densities of Comparative Examples 2 to 3 have all increased. However, the current densities of Examples 1 to 3 loaded with both copper and nickel bimetallic alloy nanoparticles are higher than those of Comparative Examples 2 to 3 loaded with single metals, indicating that the copper-nickel alloy bimetallic nanoparticle cathode material has good biocompatibility, enabling the conductive microbial community to have more superior electron utilization ability.

[0071] As can be seen from the above embodiments, a copper-nickel alloy nanoparticle catalyst and its preparation method provided by the present invention can improve the biocompatibility and conductivity of the cathode during the operation of the microbial electrosynthesis system, while promoting the hydrogen evolution reaction and strengthening the interfacial electron transfer. By controlling the ratio of copper-nickel alloy nanoparticles, a higher current density can be achieved in the electroactive biofilm formed on the cathode surface during the system operation. At the same time, the electrochemical process has a high degree of matching with the extracellular electron utilization process of microorganisms, and has a stronger ability to produce volatile fatty acids. Therefore, this research provides a new idea for enhancing the production of multi-carbon products, and has good research value and application prospects.

[0072] The above only introduces the technical solutions of the present invention with preferred embodiments. However, for those of ordinary skill in the art, according to the idea of the embodiments of the present invention, changes should be made in the specific implementation manners and application scopes. Therefore, in summary, the content of this specification should not be construed as a limitation of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A method for preparing a copper-nickel alloy nanoparticle catalyst, characterized in that: The method comprises the following steps: dissolving Cu(NO3)2 and Ni(NO3)2 in a mixture of water and ethanol, dripping the mixture on a carbon-based material, baking the surface and drying overnight to obtain a copper-nickel loaded carbon-based material; calcining the copper-nickel loaded carbon-based material in air at 350-450°C to obtain a copper-nickel oxide loaded carbon-based material; reducing the copper-nickel oxide loaded carbon-based material in flowing H2 at 500-600°C to obtain a copper-nickel alloy nanoparticle catalyst.

2. The method for preparing the copper-nickel alloy nanoparticle catalyst according to claim 1, characterized in that: The molar ratio of Cu(NO3)2 and Ni(NO3)2 is: 0~4:

1.

3. The method for preparing the copper-nickel alloy nanoparticle catalyst according to claim 1, characterized in that: The carbon-based material is one or more of carbon felt, carbon cloth, graphite rod, and activated carbon.

4. The method for preparing the copper-nickel alloy nanoparticle catalyst according to claim 1, characterized in that: The concentration volume percentage of the flowing H2 is 10%, the carrier gas is Ar, and the flow rate is 50-70 mL / min; the reduction time of the flowing H2 is 2-4 h.

5. A copper-nickel alloy nanoparticle catalyst, characterized in that: The preparation method is described in any one of claims 1 to 4.

6. Use of the copper-nickel alloy nanoparticle catalyst according to claim 5 in microbial electrosynthesis.

7. A microbial electrosynthesis system, characterized in that: The cathode of the microbial electrosynthesis device comprises a carbon-based material loaded with the copper-nickel alloy nanoparticle catalyst according to claim 5, and the cathode culture medium of the microbial electrosynthesis system is inoculated with a fully domesticated mixed community of electroactive microorganisms.

8. The microbial electrosynthesis system according to claim 7, characterized in that: The microbial electrosynthesis system comprises a dual-chamber reactor, wherein the cathode chamber and the anode chamber of the dual-chamber reactor are separated by a proton exchange membrane.

9. The microbial electrosynthesis system according to claim 8, characterized in that: The anode includes a material that causes an oxidation reaction in the electrolyte, and the material that causes an oxidation reaction in the electrolyte is one or more of stainless steel, platinum, and ruthenium-iridium-titanium mesh.

10. The microbial electrosynthesis system according to claim 7, characterized in that: The microbial electrosynthesis system also includes an electrolyte, which includes a cathode electrolyte and an anode electrolyte. The cathode electrolyte includes a cathode culture medium and a fully domesticated mixed population of electroactive microorganisms, and the anode electrolyte includes an anode culture medium.

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