CN113913866B - Preparation method and application of uranium-supported metal-organic framework catalyst - Google Patents

Preparation method and application of uranium-supported metal-organic framework catalyst Download PDF

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CN113913866B
CN113913866B CN202111326286.9A CN202111326286A CN113913866B CN 113913866 B CN113913866 B CN 113913866B CN 202111326286 A CN202111326286 A CN 202111326286A CN 113913866 B CN113913866 B CN 113913866B
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CN113913866A (en
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陈涛
竹文坤
何嵘
杨帆
周莉
任俨
董云
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Southwest University of Science and Technology
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Abstract

The invention discloses a preparation method and application of a uranium-supported catalyst with a metal-organic framework, which comprises the following steps: step one, dividing ZIF-8 powderDispersing in an organic solvent, and carrying out ultrasonic mixing to obtain a uniform solution; adding a uranyl nitrate aqueous solution into the uniform solution, carrying out ultrasonic mixing to obtain a mixture, stirring the mixture, carrying out centrifugal separation, carrying out vacuum drying, calcining the vacuum dried material in an inert gas atmosphere, and cooling to obtain the uranium-supported metal-organic framework catalyst. The uranium-supported metal-organic framework catalyst prepared by the invention has quite large activity, and the geometric current density of the catalyst reaches 200mA/cm under the overpotential of-1.69V vs RHE 2 The catalyst has higher Faraday Efficiency (FE) for CO products, and changes with the total applied current at 150mA/cm 2 The catalyst showed a maximum of 95% for CO at the geometric current density of (c).

Description

Preparation method and application of uranium-supported metal-organic framework catalyst
Technical Field
The invention belongs to the technical field of inorganic nano materials and preparation thereof, and particularly relates to a preparation method and application of a uranium-supported catalyst with a metal-organic framework.
Background
With the continuous increase of nuclear energy demand, a great amount of uranium-containing nuclear waste liquid is generated in the processes of nuclear fuel production, nuclear power plant operation, nuclear facility retirement and the like. In nuclear waste liquid, uranium has strong radioactivity, long half-life period and large biological and chemical toxicity, is easy to migrate to a biosphere along with surface water and underground water, and causes great harm to ecological environment and normal life activities of human beings. At present, landfill is a main treatment method for uranium treatment, but the treatment method not only has potential safety hazards of landfill material decomposition, but also causes waste of a large amount of depleted uranium. How to effectively extract the depleted uranium in the nuclear waste liquid and realize the reuse of the depleted uranium is of great importance.
The chemical property of uranium element is very special, and the energy of 6d orbit is similar to that of 5f orbit, so that unique 6d-5f hybridization phenomenon is formed. This phenomenon causes the valence state of uranium ions to vary from +3 to +6, and the coordination sphere, similar to a transition metal, to be converted. During the redox process, this unique dynamic coordination change tends to change the reaction path, with a significant impact on the reaction energy barrier. In addition, uranium is similar to lanthanide metals in that its unique 5f orbital electron forms an electrophilic complex with small molecules, and its large ionic radius makes it possible to have a unique coordination environment. For example, the f-orbitals of uranium and aromatic hydrocarbons can form delta feedback bonds similar to pi feedback bonds of transition metals and aromatic hydrocarbons. In summary, uranium and its complexes are highly reactive towards substrates that would normally be inert (e.g., nitrogen, small organic molecules, etc.), and are potential catalysts for inert small molecule conversion. Therefore, the catalyst for preparing the depleted uranium in the nuclear waste liquid into the micromolecular catalytic conversion by a physicochemical means is a feasible scheme for realizing the recycling of the depleted uranium.
As early as the early 20 th century, the nobel chemical prize acquirer habai found that uranium could promote the activation of inert n≡n in the catalytic synthesis of ammonia, and thus the catalytic synthesis of ammonia was even more reactive than the usual iron-based catalyst. In the electrolytic water reaction, uranium complexes tend to have cyclic changes of +3 and +4, where U (III) can catalyze H 2 And the cleavage reaction of O generates U (IV) -OH intermediate species, and the U (IV) -OH can be dissociated into U (III) and OH-under the action of electrons, so that the hydrogen evolution reaction of electrolyzed water is promoted. In 2015, the university of Qinghai Wang Xun professor team controllably prepared heterogeneous uranium oxide nanoparticles of various morphologies, which found 10% Ce doped UO 2 The nano-particles can catalyze the hydrogen evolution reaction of electrolyzed water under alkaline conditions. Furthermore, uranium based compounds also exhibit unique catalytic properties in oxidation reactions.
In recent years, in small molecule catalytic reactions, metal monoatomic catalysts have become ideal choices for activating inert small molecules due to ultra-high atom utilization and unsaturated coordination environments. In 2011, university of Dalian chemical and physical institute Zhang Tao academy and university of Qinghai Li Juan taught to develop a catalyst for oxidation of CO with excellent performancePt of (2) 1 /FeO x Catalysts, the concept of a single-atom catalyst is presented for the first time. After this, the monoatomic catalyst is reacted with CO 2 Reduction, N 2 The catalyst has excellent catalytic potential in small molecule catalytic reactions such as reduction, hydrogen evolution of electrolyzed water, oxygen evolution of electrolyzed water and the like. In the catalytic activation of inert small molecules, metal monoatomic catalysts have natural advantages in terms of activity and selectivity: on the one hand, the metal monoatomic catalyst has an active site with high atomic level dispersion, and an unsaturated coordination environment is arranged between the active site and the carrier, so that the catalytic activation of inert N (ident) N, C =O bonds is promoted; on the other hand, the monoatomic active site has high uniformity relative to the nanoparticle system, and the coordination environment has great influence on the electronic structure, so that the monoatomic active site is single and adjustable in catalytic selectivity.
Although development of uranium-based catalysts has been partially studied and reported at present, preparation and catalytic application exploration of single-atom uranium catalysts are extremely rare, and the following bottleneck problems mainly exist: there is a lack of methods for preparing high purity monatomic uranium catalysts in high yield from uranium-containing nuclear waste solutions. In nuclear waste, uranium is generally present in the form of soluble +6 valent uranyl ions (U (VI)). In the process of reducing and enriching U (VI) into a carrier, uranium is extremely easy to bond with oxygen to form a deposited oxide. The formation of isolated and dispersed uranium monoatoms (distinct from uranium oxides) requires a radical or coordination structure of uranium limited uranium by the support and controls the rate of the reduction reaction so that the reaction tends to form multiple monoatomic uranium sites without forming crystalline oxides.
Disclosure of Invention
It is an object of the present invention to address at least the above problems and/or disadvantages and to provide at least the advantages described below.
To achieve these objects and other advantages and in accordance with the purpose of the invention, there is provided a method for preparing a metal-organic framework supported uranium catalyst, including the steps of:
step one, dispersing ZIF-8 powder in an organic solvent, and carrying out ultrasonic mixing to obtain a uniform solution;
adding a uranyl nitrate aqueous solution into the uniform solution, carrying out ultrasonic mixing to obtain a mixture, stirring the mixture, carrying out centrifugal separation, carrying out vacuum drying, calcining the vacuum dried material in an inert gas atmosphere, and cooling to obtain the uranium-supported metal-organic framework catalyst.
Preferably, the mass volume ratio of the ZIF-8 powder to the organic solvent is 80-120 mg:10mL; the mass volume ratio of the ZIF-8 powder to the uranium dioxynitrate aqueous solution is 80-120 mg: 40-60 mu L; the concentration of the uranyl nitrate aqueous solution is 80-100 mg/mL.
Preferably, in the first step, the ultrasonic mixing frequency is 40-60 KHz, the power is 200-300W, and the time is 25-35 min; in the second step, the ultrasonic mixing frequency is 40-60 KHz, the power is 200-300W, and the time is 1-3 min.
Preferably, in the second step, the stirring speed is 300-500 r/min, the stirring time is 5-8 h, the vacuum drying temperature is 70-85 ℃, and the drying time is 5-8 h.
Preferably, the inert gas is argon, and the ventilation speed is 15-25 mL/min; the calcination temperature is 900-1100 ℃, the temperature rising speed is 4-6 ℃/min, and the calcination time is 1.5-3 h.
Preferably, the double-frequency ultrasonic wave is applied in the process of stirring the mixture, and the double-frequency ultrasonic wave adopts an alternate treatment mode: the frequency of the double-frequency ultrasonic wave is 40-60 KHz and 100-120 KHz respectively, the alternating working time of the double-frequency ultrasonic wave is 5-7 s, and the ultrasonic power is 200-300W.
Preferably, the organic solvent is n-hexane.
Preferably, the preparation method of the ZIF-8 powder comprises the following steps: 0.558g Zn (NO) 3 ) 2 ·6H 2 O was dissolved in 15mL of methanol, and 15mL of methanol containing 0.616g of 2-methylimidazole was added thereto, followed by sonication at room temperature for 10 minutes, then static growth at 35℃for 12 hours, centrifugation of the precipitate, washing with methanol 3 times, and vacuum drying at 65℃overnight to give ZIF-8 powder.
The invention also provides a method for preparing the metal-organic framework supported uranium catalyst in CO 2 In electrocatalytic reductionThe application of the method is characterized in that circulating electrolyte is introduced into a cathode chamber and an anode chamber of a flow cell electrolytic cell, a metal-organic framework supported uranium catalyst is manufactured into a working electrode, and a PTFE gasket is used for clamping the working electrode, a Nafion 115 proton exchange membrane and foam nickel; silver/silver chloride is used as a reference electrode, and a platinum wire electrode is used as a counter electrode; CO is introduced into the electrolyte 2 Reach saturation and then apply a voltage to drive CO 2 The reduction reaction takes place on the surface of the catalyst of the invention.
Preferably, the electrolyte is a 1mol/L potassium hydroxide solution, and the introducing speed of the circulating electrolyte is 10mL/min; the CO 2 The inlet speed is 20mL/min; the process for preparing the working electrode by the uranium-supported metal-organic framework catalyst comprises the following steps: dispersing 0.5-1 mg of metal organic framework supported uranium catalyst in 500 mu L of ethanol, 500 mu L of deionized water and 20 mu L of Nafion solution, performing ultrasonic treatment for 30 minutes to obtain uniformly distributed catalyst ink, dripping the uniformly distributed catalyst ink onto carbon fiber paper with polyimide film attached to the back, and drying at 50-60 ℃ to obtain the working electrode.
The invention at least comprises the following beneficial effects: the metal-organic framework supported uranium catalyst prepared by the method shows quite large activity, and the geometric current density of the U-SAs/NC catalyst reaches 200mA/cm under the overpotential of-1.69V vs RHE 2 The catalyst has higher Faraday Efficiency (FE) for CO products, and changes with the total applied current at 150mA/cm 2 U-SAs/NC showed a maximum of 95% for CO, about 1.8 times higher than U-NP/NC and about 11.9 times higher than NC catalyst.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
Description of the drawings:
FIG. 1 is a TEM image of a U-SAs/NC catalyst of the invention;
FIG. 2 is a HADDF-STEM diagram of the U-SAs/NC catalyst of the present invention and an enlarged view thereof;
FIG. 3 is a SEM image of the ZIF-8 powder of the present invention before (a) and after (b) calcination;
FIG. 4 is a TEM image of ZIF-8 powder of the present invention prior to calcination;
FIG. 5 is a graph showing intensity distribution along the X-Y line in an HAADF-STEM image of a U-SAs/NC catalyst of the invention;
FIG. 6 is an XRD pattern for the U-SAs/NC catalyst and NC catalyst of the invention;
FIG. 7 is a diagram of the U-SAs/NC catalyst EDS of the present invention;
FIG. 8 is a graph of geometric current densities on NC, U-NP/NC, and U-SAs/NC of the present invention;
FIG. 9 is a LSV plot of NC, U-NP/NC, and U-SAs/NC of the present invention;
FIG. 10 is a graph of geometric current densities on U-NP/NC, U-SAs/NC, and U-SAs/NC-1 of the present invention;
FIG. 11 shows Faraday efficiencies of CO production at NC, U-NP/NC, and U-SAs/NC of the present invention;
FIG. 12 shows Faraday efficiencies of CO production on U-NP/NC, U-SAs/NC, and U-SAs/NC-1 of the present invention;
FIG. 13 is a graph of the time dependence of the Faraday efficiency of geometric current density (j) and CO at U-SAs/NC for constant potential of-0.8V versus RHE in accordance with the present invention;
FIG. 14 is a SR-FTIR diagram of the U-SAs/NC of the present invention under operating conditions.
The specific embodiment is as follows:
the present invention is described in further detail below with reference to the drawings to enable those skilled in the art to practice the invention by referring to the description.
It will be understood that terms, such as "having," "including," and "comprising," as used herein, do not preclude the presence or addition of one or more other elements or groups thereof.
Example 1:
the preparation method of the metal-organic framework supported uranium catalyst comprises the following steps:
step one, dispersing 100mg of ZIF-8 powder in 10mL of n-hexane, and carrying out ultrasonic mixing to obtain a uniform solution; the frequency of ultrasonic mixing is 45KHz, the power is 300W, and the time is 30min;
adding 50 mu L of uranyl nitrate aqueous solution (100 mg/mL) into the uniform solution, ultrasonically mixing at room temperature (with the frequency of 45KHz, the power of 300W and the time of 2 min) to obtain a mixture, stirring the mixture (400 r/min,6 h), centrifugally separating, vacuum drying at 80 ℃ for 6h, heating the vacuum dried material to 1000 ℃ under Ar atmosphere (20 mL/min), calcining for 2h at the temperature rising rate of 5 ℃/min, and cooling to obtain a metal-organic framework supported uranium catalyst (U-SAs/NC);
the preparation method of the ZIF-8 powder comprises the following steps: 0.558g Zn (NO) 3 ) 2 ·6H 2 O was dissolved in 15mL of methanol, and 15mL of methanol containing 0.616g of 2-methylimidazole was added thereto, followed by sonication at room temperature for 10 minutes, then static growth at 35℃for 12 hours, centrifugation of the precipitate, washing with methanol 3 times, and vacuum drying at 65℃overnight to give ZIF-8 powder.
Example 2:
the preparation method of the metal-organic framework supported uranium catalyst comprises the following steps:
step one, dispersing 100mg of ZIF-8 powder in 10mL of n-hexane, and carrying out ultrasonic mixing to obtain a uniform solution; the frequency of ultrasonic mixing is 45KHz, the power is 300W, and the time is 30min;
adding 50 mu L of uranyl nitrate aqueous solution (100 mg/mL) into the uniform solution, ultrasonically mixing at room temperature (with the frequency of 45KHz, the power of 300W and the time of 2 min) to obtain a mixture, stirring the mixture (400 r/min,6 h), centrifugally separating, vacuum drying at 80 ℃ for 6h, heating the vacuum dried material to 1000 ℃ under Ar atmosphere (20 mL/min), calcining for 2h at the temperature rising rate of 5 ℃/min, and cooling to obtain a metal-organic framework supported uranium catalyst (U-SAs/NC-1); applying double-frequency ultrasonic waves in the process of stirring the mixture, wherein the double-frequency ultrasonic waves adopt an alternate treatment mode: the frequency of the double-frequency ultrasonic wave is 45KHz and 120KHz respectively, the alternating working time of the double-frequency ultrasonic wave is 5s, and the ultrasonic power is 300W;
the preparation method of the ZIF-8 powder comprises the following steps: 0.558g Zn (NO) 3 ) 2 ·6H 2 O was dissolved in 15mL of methanol, and 15mL of methanol containing 0.616g of 2-methylimidazole was added thereto, sonicated at room temperature for 10 minutes, then grown statically at 35℃for 12 hours, centrifuged the precipitate, washed 3 times with methanol, and dried under vacuum at 65℃overnight to giveTo ZIF-8 powder.
Comparative example 1:
the preparation method of the ZIF-8 powder comprises the following steps: 0.558g Zn (NO) 3 ) 2 ·6H 2 O is dissolved in 15mL of methanol, 15mL of methanol containing 0.616g of 2-methylimidazole is added, ultrasonic treatment is performed for 10 minutes at room temperature, then static growth is performed for 12 hours at 35 ℃, precipitation is centrifuged, methanol is washed for 3 times, vacuum drying is performed at 65 ℃ for overnight, ZIF-8 powder is obtained, ZIF-8 powder is heated to 1000 ℃ under Ar atmosphere (20 mL/min) for calcination for 2 hours at a temperature rising rate of 5 ℃/min, and cooling is performed, so that catalyst (NC) is obtained;
comparative example 2:
step one, dispersing 100mg of ZIF-8 powder in 10mL of n-hexane, and carrying out ultrasonic mixing to obtain a uniform solution; the frequency of ultrasonic mixing is 45KHz, the power is 300W, and the time is 30min;
adding 500 mu L of uranyl nitrate aqueous solution (100 mg/mL) into the uniform solution, ultrasonically mixing at room temperature (with the frequency of 45KHz, the power of 300W and the time of 2 min) to obtain a mixture, stirring the mixture (400 r/min,6 h), centrifugally separating, vacuum drying at 80 ℃ for 6h, heating the vacuum dried material to 1000 ℃ under Ar atmosphere (20 mL/min), calcining for 2h at the temperature rising rate of 5 ℃/min, and cooling to obtain a catalyst (U-NP/NC);
the preparation method of the ZIF-8 powder comprises the following steps: 0.558g Zn (NO) 3 ) 2 ·6H 2 O was dissolved in 15mL of methanol, and 15mL of methanol containing 0.616g of 2-methylimidazole was added thereto, followed by sonication at room temperature for 10 minutes, then static growth at 35℃for 12 hours, centrifugation of the precipitate, washing with methanol 3 times, and vacuum drying at 65℃overnight to give ZIF-8 powder.
Characterization of morphology of U-SAs/NC prepared in example 1 and NC prepared in comparative example 1, FIG. 1 is TEM image of U-SAs/NC; FIG. 2 is a HADDF-STEM image and magnified image of U-SAs/NC; FIG. 3 is an SEM image of NC before (a) and after (b) annealing; FIG. 4 is a TEM image before NC annealing;
the morphology of U-SAs/NC was further characterized by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The results show that the prepared U-SAs/NC maintains the original polyhedral shape after annealing treatmentIn the shape of a tube, and no distinct nanoparticles were detected on the surface (U-SAs/NC or NC) (FIG. 1, FIG. 3, FIG. 4). The heavy atomic mass U atoms with atoms dispersed on the NC skeleton can be easily distinguished in an atomic resolution high angle annular dark field scanning transmission electron microscope (HAADF-STEM) image, where they are marked with white circles (fig. 2). The intensity profile along X-Y shows that the spacing between U atoms is at least 0.31nm, significantly greater than the effective diameter (R U =0.277 nm), which further demonstrates the atomic-scale dispersion of U species (fig. 5). In addition, the X-ray powder diffraction (XRD) pattern of U-SAs/NC was almost identical to that of the original MOF-derived N-C backbone, further confirming the absence of a U-containing phase (FIG. 6). Furthermore, the corresponding HAADF energy dispersive X-ray spectroscopy (EDS) element mapping reveals a uniform distribution of C, N, O and U across the architecture (fig. 7).
Furthermore, the U content of the load in U-SAs/NC is as high as 1.8wt% based on inductively coupled plasma emission spectroscopy (ICP-OES) results.
Electrochemical measurement:
with respect to CO 2 Electrochemical experiments of reduction reaction performance were all performed on a CHI760E electrochemical analyzer using a typical three-electrode electrochemical cell with a platinum wire electrode as a counter electrode and saturated Ag/AgCl as a reference electrode, and a metal-organic framework-supported uranium catalyst (i.e., the catalyst prepared in example 1, example 2, comparative example 1 or comparative example 2) was prepared as a working electrode (specifically, catalyst powder was dispersed in 500 μl of ethanol, 500 μl of deionized water and 20 μl of Nafion solution (5 wt%, sigma-Aldrich), then sonicated for 30 minutes, and then uniformly distributed catalyst ink was drop-cast on carbon fiber paper with polyimide film attached on the back, and dried at 50 ℃ to obtain the working electrode). All potentials in the figure are converted to Reversible Hydrogen Electrodes (RHE), which are converted to:
E(vs.RHE)＝E(vs.Ag/AgCl)+0.197V+0.0592×pH；
in a flow cell, electrochemical measurements are performed in a three electrode system of an electrochemical station (AUT 50783). The prepared cathode (working electrode made of uranium catalyst supported by metal organic framework), nafion 115 proton exchange membrane and foam nickel were placed and passed through PTFE gasketClamped together. Here, the nickel foam is used as an anode for the oxygen evolution reaction in the flow cell, since nickel is a good oxygen evolution reaction catalyst in alkaline environments. 30mL of electrolyte (1M KOH aqueous solution) was introduced into the anode chamber between the anode and the membrane, and into the cathode chamber between the membrane and the cathode, respectively. Electrolyte in the cathode and anode was circulated by two pumps at a rate of 10 mL/min. At the same time, CO 2 Gas (99.99%) was continuously supplied to the gas chamber located at the back of the cathode at a rate of 20 mL/min. Through the pores of the cathode, the gas may diffuse to the interface between the cathode and the electrolyte. The performance of the cathode was evaluated by performing constant current electrolysis. All potentials were measured against an Ag/AgCl reference electrode (3M KCl). At each reaction potential, the product gas and CO were collected within 1200 seconds after 600 seconds of reaction 2 Is a mixture of (a) and (b). The gas composition analysis was performed next by GC. The separated gas product is passed through a thermal conductivity detector (for H 2 ) And flame ionization detectors (for CO) for analysis. The product is quantified using a conversion factor derived from a standard calibration gas.
CO and H 2 Faraday efficiency (f.e.) can be calculated as:
Figure BDA0003347041240000081
where F is faraday constant, n=2 is the number of electrons participating in the electrode reaction, S is the integrated area of the CO peak in the GC spectrum, S 0 Is a conversion factor determined by standard sample calibration GC, v=20 mL/min is CO 2 Inflow rate, t, is the time required to collect the gas and Q is the total charge obtained from the j-t curve.
FIG. 8 shows geometric current densities at NC, U-NP/NC, and U-SAs/NC. As shown in FIG. 8, the prepared U-SAs/NC exhibited a higher geometric current density than the U-NP/NC and NC catalysts, as verified by Linear Sweep Voltammetry (LSV) (FIG. 9). In particular, the geometric current density of the U-SAs/NC catalyst reaches 200mA/cm at an overpotential of-1.69V vs RHE 2 1.3 times and 1.6 times that of the U-NP/NC and NC catalysts, respectively. FIG. 10 shows the geometry of the U-NP/NC, U-SAs/NC, and U-SAs/NC-1Flow density U-SAs/NC-1 produced exhibits a higher geometric current density than U-SAs/NC catalyst.
For the catalyst of the invention, H 2 And CO are the main reaction products, which are quantified by gas chromatography analysis. FIGS. 11 and 12 show the Faraday Efficiency (FE) of the catalyst on CO product as a function of total current applied at 150mA/cm 2 U-SAs/NC showed a maximum of 95% for CO, about 1.8 times higher than U-NP/NC and about 11.9 times higher than NC catalyst. Furthermore, U-SAs/NC is controlled in a current window (50 to 150mA/cm 2 ) In which the Faraday efficiencies are all over 90% and U-SAs/NC-1 is higher than U-SAs/NC (FIG. 12); in addition, the prepared U-SAs/NC showed excellent durability in a 10-hour potentiostatic test, the current density decay was less than 4%, and the FE of CO was maintained at 90% or more at-0.8 Vvs RHE, further confirming that U-SAs/NC had better durability (FIG. 13).
To further understand CO 2 The key intermediate species in the electroreduction process were then fourier transformed infrared spectroscopy (SR-FTIR) using synchrotron radiation under operating conditions (fig. 14). Monodentate carbonate groups (m-CO) compared to open circuit voltage 3 2- ) Appear at 1520cm after the voltage is applied -1 Indicating more CO as the applied voltage decreases 2 The molecules adsorb on the catalyst surface. With decreasing applied voltage, 1694cm -1 Characteristic peak intensity at (CO 2 · - Free radical) increase, indicating that in CO 2 More CO in the reduction process 2 The molecule is activated. At the same time at-1354 cm -1 And-1660 cm -1 The peak at is due to COOH, which is CO 2 Key intermediates for electroreduction. Thus, the SR-FTIR results demonstrate the dynamic adsorption and desorption processes of oxygen-containing intermediates at well-defined U monoatomic active sites.
Although embodiments of the present invention have been disclosed above, it is not limited to the details and embodiments shown and described, it is well suited to various fields of use for which the invention would be readily apparent to those skilled in the art, and accordingly, the invention is not limited to the specific details and illustrations shown and described herein, without departing from the general concepts defined in the claims and their equivalents.

Claims (8)

1. Uranium catalyst loaded on metal-organic framework in CO 2 The application of the method in electrocatalytic reduction is characterized in that circulating electrolyte is introduced into a cathode chamber and an anode chamber of a flow cell electrolytic cell, a metal organic framework supported uranium catalyst is manufactured into a working electrode, and a PTFE gasket is used for clamping the working electrode, a Nafion 115 proton exchange membrane and foam nickel; silver/silver chloride is used as a reference electrode, and a platinum wire electrode is used as a counter electrode; CO is introduced into the electrolyte 2 Reach saturation and then apply a voltage to drive CO 2 Carrying out reduction reaction on the surface of the uranium-supported catalyst of the metal organic framework;
the preparation method of the metal-organic framework supported uranium catalyst comprises the following steps:
step one, dispersing ZIF-8 powder in an organic solvent, and carrying out ultrasonic mixing to obtain a uniform solution;
adding a uranyl nitrate aqueous solution into the uniform solution, carrying out ultrasonic mixing to obtain a mixture, stirring the mixture, carrying out centrifugal separation, carrying out vacuum drying, calcining the vacuum dried material in an inert gas atmosphere, and cooling to obtain a uranium-loaded catalyst with a metal-organic framework;
the mass volume ratio of the ZIF-8 powder to the organic solvent is 80-120 mg:10mL; the mass volume ratio of the ZIF-8 powder to the uranium dioxynitrate aqueous solution is 80-120 mg: 40-60 mu L; the concentration of the uranyl nitrate aqueous solution is 80-100 mg/mL.
2. The uranium supported metal organic framework catalyst of claim 1 in CO 2 The application in electrocatalytic reduction is characterized in that in the first step, the ultrasonic mixing frequency is 40-60 KHz, the power is 200-300W, and the time is 25-35 min; in the second step, the ultrasonic mixing frequency is 40-60 KHz, the power is 200-300W, and the time is 1-3 min.
3. The uranium supported metal organic framework catalyst of claim 1 in CO 2 The application in the electrocatalytic reduction is characterized in that in the second step, the stirring speed is 300-500 r/min, the stirring time is 5-8 h, the vacuum drying temperature is 70-85 ℃, and the drying time is 5-8 h.
4. The uranium supported metal organic framework catalyst of claim 1 in CO 2 The application in electrocatalytic reduction is characterized in that the inert gas is argon, and the ventilation speed is 15-25 mL/min; the calcination temperature is 900-1100 ℃, the temperature rising speed is 4-6 ℃/min, and the calcination time is 1.5-3 h.
5. The uranium supported metal organic framework catalyst of claim 1 in CO 2 The application in electrocatalytic reduction is characterized in that in the second step, double-frequency ultrasonic waves are applied in the process of stirring the mixture, and the double-frequency ultrasonic waves adopt an alternate treatment mode: the frequency of the double-frequency ultrasonic wave is 40-60 KHz and 100-120 KHz respectively, the alternating working time of the double-frequency ultrasonic wave is 5-7 s, and the ultrasonic power is 200-300W.
6. The uranium supported metal organic framework catalyst of claim 1 in CO 2 The application of the electrocatalytic reduction is characterized in that the organic solvent is n-hexane.
7. The uranium supported metal organic framework catalyst of claim 1 in CO 2 The application in electrocatalytic reduction is characterized in that the preparation method of the ZIF-8 powder is as follows: 0.558g Zn (NO) 3 ) 2 ·6H 2 O was dissolved in 15mL of methanol, and 15mL of methanol containing 0.616g of 2-methylimidazole was added thereto, followed by sonication at room temperature for 10 minutes, then static growth at 35℃for 12 hours, centrifugation of the precipitate, washing with methanol 3 times, and vacuum drying at 65℃overnight to give ZIF-8 powder.
8. A metal organic framework supported uranium catalyst as claimed in claim 1In CO 2 The application in electrocatalytic reduction is characterized in that the electrolyte is 1mol/L potassium hydroxide solution, and the introducing speed of the circulating electrolyte is 10mL/min; the CO 2 The inlet speed is 20mL/min; the process for preparing the working electrode by the uranium-supported metal-organic framework catalyst comprises the following steps: dispersing 0.5-1 mg of metal organic framework supported uranium catalyst in 500 mu L of ethanol, 500 mu L of deionized water and 20 mu L of Nafion solution, performing ultrasonic treatment for 30 minutes to obtain uniformly distributed catalyst ink, dripping the uniformly distributed catalyst ink onto carbon fiber paper with polyimide film attached to the back, and drying at 50-60 ℃ to obtain the working electrode.
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