CuNi catalyst, its preparation method and application

Abstract

The application belongs to the technical field of electrocatalytic biomass conversion catalysts, and specifically discloses a CuNi catalyst and a preparation method and application thereof, wherein a nickel foil is used as a substrate, the surface of the nickel foil is pretreated to remove the oxide film on the surface of the nickel foil; the pretreated nickel foil is used as a working electrode, Ag / AgCl is used as a reference electrode, a 2*1 cm platinum sheet is used as a counter electrode, a deposition electrolyte is added, stirring is continuously carried out at a speed of 600 rmp, deposition is carried out by CV cycle under a voltage of +0.5V to -2V vs Ag / AgCl, the deposited coulombic quantity is 5-20C; the obtained precipitate is rinsed with water and ethanol respectively once, and then dried in a vacuum drying box at 60-70 DEG C for 7 min to obtain a CuNi bimetallic catalyst. When the CuNi catalyst prepared by the application is used for electrocatalytic hydrogenation of 5-hydroxymethylfurfural to synthesize 2,5-dihydroxymethylfuran, the HMF is successfully converted in a mild and clean manner, the CuNi catalyst has the advantages of low cost, high yield, high practicability and good industrialization prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrocatalytic biomass conversion catalysts, in particular to a CuNi catalyst and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of industrial level, the overuse of fuels such as coal and oil leads to a large reduction of fossil resources and causes irreversible damage to human body and environment, so more and more attention is paid to green energy-biomass energy. Due to its renewability, biomass energy is called "sleeping giant". 5-hydroxymethylfurfural (HMF) is an important biomass platform compound, which can produce 2,5-dihydroxymethylfuran (DHMF) by catalytic hydrogenation. DHMF is a biomaterial with special synthetic properties, which has great potential to improve the performance of polyester materials, so in recent years researchers have carried out extensive research.

[0003] Traditional thermal catalytic HMF hydrogenation reaction research is relatively mature, but it usually needs to be carried out at a high temperature of 100 DEG C or above and a high pressure of 3 MPa or even higher. In addition, the hydrogen involved in the reaction is still mainly extracted from fossil resources, which reduces the sustainability of the entire reduction process. The electro-reduction technology provides a more mild, controllable and clean strategy for the value-added production of biomass, without involving H2, so it has a broader application prospect. In the catalytic process, the role of the catalyst is crucial, and traditional thermal catalysis usually uses Ag, Pt and other expensive noble metals for hydrogenation reaction, which further increases the cost, therefore, it has good practicability to develop non-noble metal catalysts to catalyze 5-hydroxymethylfurfural hydrogenation. SUMMARY

[0004] In order to solve the above technical problems, the present application provides a CuNi catalyst and a preparation method and application thereof.

[0005] In order to achieve the above purpose, the present application is implemented according to the following technical solutions:

[0006] One of the purposes of the present application is to provide a preparation method of CuNi catalyst, which comprises the following steps:

[0007] S1, pretreatment of the substrate: taking a nickel foil as the substrate, pretreating the surface of the nickel foil to remove the oxide film on the surface of the nickel foil;

[0008] S2, electrodeposition: the pretreated nickel foil is used as a working electrode, Ag / AgCl is used as a reference electrode, a 2*1cm platinum sheet is used as a counter electrode, a deposition electrolyte is added, stirring is continuously carried out at 600rmp, deposition is carried out by CV cycle at a voltage of +0.5V to-2V vs Ag / AgCl, the deposited coulombic quantity is 5-20C, the obtained precipitate is rinsed with water and ethanol respectively once, and then is dried in a vacuum drying box at 60-70 DEG C for 7min to obtain a CuNi bimetallic catalyst.

[0009] Further, the step S1 specifically comprises:

[0010] S11, after the nickel foil (Ni>=99.99%) is cut to a size of 2cm*1cm, the nickel foil is repeatedly rinsed with ethanol and ultrapure water for 3 times;

[0011] S12, the cathode of a double electrode direct current power supply is connected with a graphite rod electrode, the anode is connected with the treated nickel foil, the nickel foil is placed in an electrochemical polishing solution, the solution is continuously stirred at a rotating speed of 400rmp, a constant voltage of 7V is applied for electrolysis, the polishing is finished after 2min30s, the anode nickel foil becomes bright, the nickel foil is taken out and rinsed with ethanol and water respectively for 2 times, and the oxide film on the surface of the nickel foil is completely removed.

[0012] Further, the preparation method of the electrochemical polishing solution is:

[0013] 30ml of 99% pure ethanol and 10ml of perchloric acid are mixed under ice water bath condition, ultrasonic mixing is carried out for 30s, and the electrochemical polishing solution is obtained.

[0014] Further, in the step S2, the preparation method of the deposition electrolyte is:

[0015] 0.8g of Cu(NO3)2*6H2O and 272mg of sodium dodecyl sulfonate are respectively weighed and placed in a three-electrode single-chamber electrolytic cell containing 40ml of ultrapure water, at this time, the copper ion concentration is 0.0677mol / L, the above solution is ultrasonically mixed for 20min, then is transferred to a water bath kettle with a temperature of 65 DEG C for constant temperature water bath for 15min, and after the water bath is finished, deposition is rapidly carried out, and the deposition electrolyte is obtained.

[0016] Further, in the step S2, the scanning rate of CV is 100mV / s.

[0017] The second purpose of the application is to provide a CuNi catalyst prepared by the above method.

[0018] The third purpose of the application is to provide an application of the CuNi catalyst in electrocatalytic 5-hydroxymethylfurfural hydrogenation to synthesize 2,5-dihydroxymethylfuran.

[0019] The mechanism of the present application is that the CuNi non-noble metal material is obtained by electrochemically polishing the Ni foil in a strong acid solution, then electrodepositing, and depositing the copper microspheres on the Ni foil, and drying.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] (1) The method for preparing the CuNi catalyst of the present application has the advantages of simple synthesis, low price, low synthesis temperature, high material reproducibility, and stable material structure, etc., compared with the traditional solid-phase reaction method and the solvothermal method.

[0022] (2) The present application controls the deposition amount of Cu on the surface of the Ni sheet, regulates the number of active sites of the Cu-Ni interface, enhances the interaction between the CuNi catalyst and HMF, and effectively solves the problems of poor catalytic effect, low product conversion rate, and low selectivity in the process of electrocatalytic reduction of 5-hydroxymethylfurfural.

[0023] (3) The CuNi catalyst prepared by the present application successfully converts HMF in a mild and clean way when used in the electrocatalytic hydrogenation of 5-hydroxymethylfurfural to 2,5-dihydroxymethylfuran, has the advantages of low cost, high yield, high practicability, and good industrialization prospect. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The flow chart for preparing the CuNi catalyst of the present application.

[0025] Figure 2 The SEM image of the CuNi catalyst prepared in Example 1.

[0026] Figure 3 The XRD image of the CuNi catalyst prepared in Example 1.

[0027] Figure 4 The DHMF production efficiency of the 10C material under different potentials.

[0028] Figure 5 The DHMF faradic efficiency of the three materials under different potentials.

[0029] Figure 6 The faradic efficiency and conversion rate of the 10C material in the catalytic reaction under different HMF concentrations.

[0030] Figure 7 The conversion rate and DHMF faradic efficiency of the 10C material in 8 cycles. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to examples. The specific examples described herein are only used to explain the present application and do not limit the present application.

[0032] The raw materials, reagents and equipment used in the following examples are commercially available unless otherwise specified.

[0033] Example 1

[0034] Reference Figure 1 Three pieces of Ni foil with a size of 2x1 cm were taken, washed in ethanol and ultrapure water in turn, and then placed in a mixed solution of 30 ml of ethanol (purity 99%) and 10 ml of perchloric acid (analytical pure) to perform electrochemical polishing by a direct current power supply at a voltage of 7 V. The electrolysis was ended after 2 min 30 s, and the nickel foil was taken out and washed with ethanol and water twice. Then 0.8 g of Cu(NO3)2·6H2O and 272 mg of sodium dodecyl sulfonate were weighed and placed in a three-electrode single-chamber electrolytic cell containing 40 ml of ultrapure water, and ultrasonic mixing was performed for 20 min. Then the mixture was transferred to a water bath at a temperature of 65°C for constant temperature water bath for 15 min. After the water bath was completed, the deposition was quickly performed. The treated nickel foil was used as the working electrode, Ag / AgCl was used as the reference electrode, a 2x1 cm platinum sheet was used as the counter electrode, and the above-mentioned mixed solution was used as the deposition electrolyte. The stirring was continuously performed at a speed of 600 rpm, and the deposition was performed by CV cycle at a voltage of +0.5 V to -2 V vs Ag / AgCl, wherein the scan rate of CV was 100 mV / s. The coulombic quantities of the deposition of the three pieces of identical nickel foil were 5 C, 10 C and 20 C, respectively. The obtained materials were washed with water and ethanol once, respectively, and then dried in a vacuum drying oven at 60-70°C for 7 min to obtain the final CuNi catalysts with different deposition quantities.

[0035] The CuNi catalysts with deposition quantities of 5 C, 10 C and 20 C obtained in this example were subjected to scanning electron microscope analysis, and the results are shown in Figure 2 It can be seen from Figure 2 that the distribution of copper particles on the Ni foil is in the form of nearly circular island-shaped particles, and the distribution state of Cu particles caused by different deposition quantities is different. The copper particles of the 5 C material are uniformly distributed on the Ni foil but the number of copper particles is small, the copper particles of the 10 C material are uniformly distributed on the substrate and the number of copper particles is large, and the 20 C material has a large number of copper particles and forms clusters.

[0036] It can be seen from Figure 2 that the island-shaped Cu particles are successfully grown on the Ni surface. These morphology characterizations show that different deposition quantities are an effective strategy to control the number of active sites of CuNi catalysts.

[0037] The CuNi catalyst prepared in the present example was subjected to X-ray diffraction (XRD) analysis, and the results are shown in Figure 3 It can be seen from Figure 3 that characteristic peaks of Cu appeared at 43.3°, 50.4° and 74.1°, and characteristic peaks of the substrate Ni appeared at 44.5°, 51.8° and 76.4°, which indicates that the Cu particles are successfully deposited on the nickel sheet and different deposition amounts result in consistent valence of the deposited metal.

[0038] Example 2

[0039] The 5C, 10C and 20C materials prepared in Example 1 were respectively used as working electrodes in H cells for electrocatalytic reduction of HMF to generate product DHMF. The cathode and anode of the H cell were separated by a proton membrane (model: DuPont Nafion 117), the cathode electrolyte was a H3BO3-KOH solution containing 20 mM / L HMF, and the anode electrolyte was a H3BO3-KOH solution (the concentration of H3BO3 in the electrolyte was 0.5 mol / L, and KOH was added to adjust the pH to 9.2); a Pt sheet electrode was used as a counter electrode, an Ag / AgCl electrode was used as a reference electrode, and the CuNi material described in the present application was used as a working electrode. When HMF was electrolyzed, five potentials were selected in the potential range of -0.36 to -0.56 V vs RHE for constant potential polarization, and during the reaction process, the solution in the cathode chamber changed from light yellow to colorless, indicating the gradual consumption of HMF. The present application quantitatively determined HMF and DHMF before and after the reaction by Agilent high performance liquid chromatography. The production efficiency and Faraday efficiency of product DHMF were calculated using the following formulas:

[0040] DHMF yield = (actual yield / theoretical yield) x 100%;

[0041] Faraday efficiency (FE) of DHMF = moles of DHMF produced x number of electrons transferred x 96485 / actual charge passed in the reaction.

[0042] The results are shown in Figure 4 and Figure 5 It can be seen from Figure 4 and Figure 5 that as the reaction potential continuously increases, the Faraday efficiency of DHMF under the action of 5C, 10C and 20C materials increases first and then decreases with the increase of the potential, and in particular, the performance of the 10C catalyst is always higher than that of 5C and 20C materials at different potentials. At a potential of -0.46 V vs RHE, the Faraday efficiency of DHMF under the action of the 10C catalyst reaches 83.4%, the yield of DHMF is as high as 90%, and the conversion rate of DHMF continuously increases with the increase of the potential at different potentials, which indicates that the catalyst has good catalytic effect.

[0043] Example 3

[0044] The 10C material prepared in Example 1 was used as the working electrode in the H-cell for the electrocatalytic reduction of HMF to product DHMF. The HMF concentration in the catholyte was controlled from 20 mM to 100 mM, and the anolyte was still H3BO3-KOH solution; Pt sheet electrode was used as the counter electrode, and Ag / AgCl electrode as the reference electrode. The potential for the reduction of HMF was set at -0.61 V vs RHE, and the Faraday efficiency and conversion of the product were calculated, in which the amount of hydrogen produced was detected by high efficiency gas chromatography. The results are shown in Figure 6 , and it can be seen that the Faraday efficiency of DHMF is close to 80% at 100 mM HMF concentration, indicating that the 10C catalyst is expected to help the actual industrial production and scale up. Figure 6

[0045] Example 4

[0046] The 10C material prepared in Example 1 was used as the working electrode in the H-cell for the electrocatalytic reduction of HMF to product DHMF. The catholyte and anolyte were still H3BO3-KOH solution; Pt sheet electrode was used as the counter electrode, and Ag / AgCl electrode as the reference electrode. The potential for the reduction of HMF was set at -0.46 V vs RHE, and the Faraday efficiency and conversion of the product were calculated, in which the amount of hydrogen produced was detected by high efficiency gas chromatography. The results are shown in Figure 7 , and it can be seen that the Faraday efficiency of DHMF is close to 80% at 100 mM HMF concentration, indicating that the 10C catalyst is expected to help the actual industrial production and scale up. Figure 7

[0047] In summary, the CuNi catalyst prepared in the application shows excellent catalytic performance when applied to the electrocatalytic reduction of HMF, and the yield and Faraday efficiency of product DHMF reach 90% and 83.4% respectively at a reaction potential of -0.46 V vs RHE.

[0048] The technical scheme of the application is not limited to the above specific examples, and any technical modification made according to the technical scheme of the application falls within the protection scope of the application.​​

Claims

1. A method for preparing a CuNi catalyst, characterized by, It comprises the following steps: S1, pretreatment of the substrate: taking a nickel foil as the substrate, electrochemically polishing the surface of the nickel foil for pretreatment to remove the oxide film on the surface of the nickel foil; S2, electrodeposition: taking the pretreated nickel foil as a working electrode, Ag / AgCl as a reference electrode, a 2*1 cm platinum sheet as a counter electrode, adding a deposition electrolyte, continuously stirring at a speed of 600 rpm, depositing at a voltage of +0.5V~-2V vs Ag / AgCl by CV cycle, and the deposited coulombic quantity is 5-20C; the obtained precipitate is washed with water and ethanol respectively once, and then dried in a vacuum drying oven at 60-70℃ for 7min to obtain a CuNi bimetallic catalyst; In the step S2, the preparation method of the deposition electrolyte is: 0.8 g of Cu(NO3)2·6H2O and 272 mg of sodium dodecyl sulfonate are weighed respectively and placed in a three-electrode single-chamber electrolytic cell containing 40 ml of ultrapure water, at this time the copper ion concentration is 0.0677 mol / L; the above solution is ultrasonically mixed for 20 min, then transferred to a water bath at a temperature of 65℃ for constant temperature water bath for 15 min, and then quickly deposited to obtain a deposition electrolyte; In the step S2, the scanning rate of CV is 100 mV / s.

2. The method of claim 1, wherein the CuNi catalyst is prepared by the steps of: The step S1 specifically comprises: S11, cutting the nickel foil to a size of 2cm*1cm and then repeatedly washing with ethanol and ultrapure water for 3 times; S12, connecting the cathode of a double-electrode direct-current power supply to a graphite rod electrode and the anode to the treated nickel foil, placing them in an electrochemical polishing solution for electrochemical polishing, continuously stirring the solution at a speed of 400 rpm, applying a constant voltage of 7V for electrolysis, and polishing for 2min30s, after which the anode nickel foil becomes bright, the nickel foil is taken out and washed with ethanol and water for 2 times respectively, and the oxide film on the surface of the nickel foil is completely removed.

3. The method of claim 2, wherein the CuNi catalyst is prepared by the steps of: The preparation method of the electrochemical polishing solution is: 30 ml of 99% pure ethanol and 10 ml of perchloric acid are mixed under ice water bath conditions, ultrasonically mixed for 30 s, and an electrochemical polishing solution is obtained.

4. A CuNi catalyst prepared by the method of any one of claims 1-3.

5. Use of the CuNi catalyst of claim 4 in electrocatalytic hydrogenation of 5-hydroxymethylfurfural to synthesize 2,5-dihydroxymethylfuran.

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