CN114784303A - Preparation and application of copper polyphenol supramolecular network interface modified rare earth-based organic frame cathode material - Google Patents
Preparation and application of copper polyphenol supramolecular network interface modified rare earth-based organic frame cathode material Download PDFInfo
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Abstract
The invention discloses a copper polyphenol supermolecular network interface modified rare earth-based organic frame cathode material electrocatalyst material and a preparation method thereof, and an active substance of a nano material is Ce-MOF @ BT-Cu. The problems of single precursor and high synthesis cost of the fuel cell catalyst are generally faced at present, while the commercial platinum carbon catalyst has high cost and poor stability. In order to overcome the problems, the invention develops a copper polyphenol supermolecular network interface modified rare earth-based organic frame cathode material based on the unique structure of a metal polyphenol network. The material has a uniform granular structure and a rich pore structure, has high potential and good limiting current, and has excellent stability. The adopted synthesis method is simple and convenient to operate, low in cost and short in preparation time, and is beneficial to realizing large-scale commercial production.
Description
Technical Field
The invention discloses a catalyst for a nano-scale copper-based oxide proton membrane fuel cell, and relates to a method for preparing Ce-MOF @ BT-Cu by a thermal decomposition process
Background
Since the 21 st century, the rapid growth of the global economy and world population has accelerated the demand for energy in human society, leading to the gradual depletion of traditional fossil energy, thereby causing a great reduction in the reserves of non-renewable energy and causing a severe situationA serious environmental problem. The problem of global environmental pollution is increasingly aggravated by a large amount of toxic gases and dust particles released by the combustion of traditional fossil energy. Therefore, actively promoting and developing new, clean and efficient renewable energy sources to replace traditional fossil energy sources has great significance on sustainable development of economy in China. Fuel Cells (FCs) are a new type of power generation device, and the theoretical power generation efficiency is 85-90% because the Fuel Cells are not affected by carnot cycle effect. In addition, the fuel has the advantages of fuel diversity, high fuel energy density, cleanness, environmental protection, low noise and the like. Therefore, the development of the fuel cell can not only relieve the energy crisis, but also eliminate the problem of environmental pollution caused by the combustion of fossil energy, and provide new opportunities for the sustainable development of human society. Rare earth elements are a large family in the periodic table of elements, and include 15 elements of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and also include 17 elements of scandium (Sc) and yttrium (Y) having properties similar to those of the elements. Most rare earth elements have no 5d orbital electrons (except lanthanum), and the outermost electrons of ions are arranged to be 4fn5d25p6. From the electronic structure, the 5d orbital of the rare earth element is empty, and generally, the empty orbital can provide a good electron transfer path for catalytic reaction. Therefore, the rare earth elements and the compounds thereof have excellent catalytic performance and extremely wide application, and are considered to be treasury of new materials such as 'new energy'. In addition, researchers at home and abroad find that the rare earth element has various catalytic and catalysis-assisting properties, so far, the rare earth element accounting for 1/4 in the total world production is used for preparing the catalyst, and good results are obtained.
Compared with common MOF, the rare earth Ce-MOF has better electrocatalytic performance, and the copper oxide has the advantages of good chemical stability, high electrochemical activity, no toxicity, low price and the like. According to the invention, a Ce-MOF metal organic framework is selected as a precursor, the Ce-MOF is modified by BT, and meanwhile, a mixture of hexahydrate copper nitrate and BT is added into Ce-MOF @ BT to improve the catalytic performance.
According to the invention, a series of rare earth-based organic framework negative catalysts with different Cu loading and prepared by high-temperature heat treatment are designed and synthesized by regulating and controlling metal loading and heat treatment temperature. Electrochemical test research shows that the Ce-MOF @ BT-Cu catalyst has the limiting current density close to that of a commercial Pt/C catalyst in 0.1M KOH at the potential equal to 0.1V, meanwhile, the reaction process of ORR in an alkaline medium is 4 electrons, and in addition, the catalyst has better stability than the commercial Pt/C catalyst.
Disclosure of Invention
The invention aims to solve the problems of the existing fuel cell catalyst, overcome the defects of the prior art, solve the problems of single precursor and synthesis cost of the existing fuel cell catalyst, and overcome the defects of high cost, toxicity and the like of a platinum-based catalytic material; the rare earth-based organic framework cathode electrocatalyst material based on copper polyphenol supramolecular network interface modification has high potential, good limiting current and excellent stability.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a preparation method of a copper polyphenol supramolecular network interface modified rare earth-based organic framework cathode electrocatalyst material comprises the following steps:
(1) firstly, preparing a Ce-MOF polymer substrate, weighing 3.3620g of trimesic acid, dissolving the trimesic acid in 60mL of absolute ethyl alcohol, dissolving 6.9480g of cerium nitrate hexahydrate in 60mL of deionized water, mixing, carrying out ultrasound treatment at room temperature, pouring the sonicated trimesic acid solution into the cerium nitrate hexahydrate solution, stirring, then placing the solution into a constant-temperature oscillator for oscillation, finally washing the obtained product with deionized water and ethyl alcohol for several times, and carrying out vacuum drying to obtain Ce-MOF;
(2) mixing the Ce-MOF prepared in the step (1) and plant polyphenolDispersing in deionized water, and performing ultrasonic treatment at room temperature; a plurality of ortho-position phenolic hydroxyl groups in the plant polyphenol can be used as a polybase ligand to carry out complexation reaction with metal ions to form a stable five-membered ring chelate. Because of many plant polyphenol coordination groups, strong complexing ability and stable complex, most metal ions form precipitates after complexing with polyphenol. Under alkaline conditions, polyphenols and metal ions are prone to form a multi-complex. Polyphenols and certain high valence metal ions such as Cr6+、Fe3+And the like, and the metal ions are reduced from a high valence state to a low valence state while complexing. Different plant polyphenols have different grabbing capacities for different metal ions; the plant polyphenol used in the present invention is myricetin, including but not limited to, tannic acid, valonea, larch, etc.
(3) Dispersing copper nitrate hexahydrate and plant polyphenol in deionized water, carrying out ultrasonic treatment at room temperature, pouring the solution subjected to ultrasonic treatment into the solution subjected to ultrasonic treatment in the step (2), and stirring and reacting at room temperature;
(4) washing and centrifuging the product obtained in the step (3) by using deionized water and an ethanol solution, and drying the product in an oven to obtain a Ce-MOF @ BT-Cu precursor;
(5) and uniformly dispersing a proper amount of dried precursor at the bottom of the porcelain ark, putting the porcelain ark into a tube furnace for high-temperature pyrolysis in an argon or nitrogen atmosphere, and naturally cooling to room temperature to obtain the copper polyphenol supermolecular network interface modified rare earth-based organic frame negative electrode electrocatalyst material Ce-MOF @ BT-Cu.
And (2) ultrasonically treating the trimesic acid, the absolute ethyl alcohol, the cerium nitrate hexahydrate and the deionized water in the step (1) for 5-10 minutes, stirring on a magnetic stirrer for 30 minutes, shaking at 60 ℃ for 1 hour, and drying at 60-80 ℃ for 13-20 hours.
The mass ratio of the plant polyphenol to the Ce-MOF in the step (2) is 1:1, and the ultrasonic time is 30-40 minutes;
the addition amount of the plant polyphenol in the step (3) is the same as that in the step (2), and the ultrasonic time is 30-40 minutes;
the drying temperature in the step (4) is 60-80 ℃, and the drying time is 16 hours;
and (5) performing high-temperature pyrolysis, namely directly heating to 800 ℃ at the heating rate of 5 ℃/min in the atmosphere of pure argon or nitrogen, keeping the temperature for 2 hours, and naturally cooling to room temperature.
The active component of the proton membrane fuel cell cathode material provided by the invention is Ce-MOF @ BT-Cu. Cu in the material exists in an atomic form and is tightly combined with a plant polyphenol network structure, so that oxygen reduction catalytic active sites of the material are effectively increased. The material has a uniform granular structure, has rich pore channel structures inside, increases the specific surface area of the material, and simultaneously exposes rich active sites, thereby promoting the permeation of electrolyte. Therefore, the material shows good oxygen reduction electrocatalytic performance, has high potential and good limiting current, and has excellent stability.
The invention has the technical advantages and beneficial effects that:
(1) the invention adopts a simple and convenient synthesis method, and has the characteristics of economy, high efficiency, environmental protection. The synthesis steps are simple and convenient to operate, the reaction conditions are mild and easy to control, and the preparation cost is low. The prepared oxygen reduction catalyst not only shows high potential and good limiting current, but also has excellent stability.
(2) The initial potential of the prepared copper polyphenol supermolecular network interface modified rare earth-based organic frame cathode material catalyst is 1.0V, the half-wave potential is 0.67V, and the limiting current density reaches 7.6mAcm-2Slightly higher than commercial platinum carbon catalyst and better electrocatalytic stability than commercial Pt/C catalyst, the catalyst is better than commercial platinum carbon catalyst as a whole.
(3) Unique metal polyphenol network structure. Firstly, the plant polyphenol has abundant phenolic hydroxyl structures, can form a stable structure with metal ions, and can be combined with a rare earth-based organic framework, so that the active sites of the material can be increased, and the accumulation of active components can be avoided. Secondly, the free H released from the plant polyphenol can penetrate into the polymer matrix and destroy the internal skeleton, while the plant polyphenol macromolecules coat the exposed surface of the material, thereby protecting its exterior from further etching and collapse of the shell. The porous structure is elaborately carved by regulating the concentration and the reaction time of plant polyphenol, so that the Ce-MOF @ BT-Cu presents uniform granular morphology to form a layered porous structure, the permeation of electrolyte is facilitated, and the oxygen reduction catalytic performance of the material is improved; in addition, the metal polyphenol network can form a metal protective layer on the surface of the organic polymer, so that the thermal stability of the organic polymer is improved. The Ce-MOF without plant polyphenol modification has poor thermal stability, and the mass of the Ce-MOF is completely lost under the calcination at the temperature of 700-900 ℃, so that the metal polyphenol network effectively improves the thermal stability of the Ce-MOF, and the Ce-MOF can be used as an electro-catalytic oxygen reduction catalyst.
Drawings
FIG. 1 is a scanning electron micrograph of a Ce-MOF @ BT-Cu nanocomposite;
FIG. 2 is an XRD pattern of the Ce-MOF @ BT-Cu nanocomposite (scan interval: 5 ° -80 °, step size: 0.02 °, scan rate: 1.5 °/min);
FIG. 3 is a Raman spectrum of a Ce-MOF @ BT-Cu nanocomposite;
FIG. 4 is an XPS spectrum of a Ce-MOF @ BT-Cu nanocomposite as a whole spectrum (a), a C spectrum (b), an O spectrum (C), an N spectrum (d), a Ce spectrum (e) and a Cu spectrum (f);
FIG. 5 is a graph showing the cyclic voltammetry characteristics of the Ce-MOF @ BT-Cu catalyst (test voltage sweep range: -0.9-0.1V, sweep rate: 50 mV/s);
FIG. 6 is a graph of Ce-MOF @ BT-Cu in O for different Cu loadings (mass ratios of copper nitrate hexahydrate to Ce-MOF of 1:2, 1:1, 2:1, 3:1, respectively)2Linear cyclic voltammograms in saturated 0.1M KOH (scan range-0.9-0.1V, scan rate 10 mv/s);
FIG. 7 shows the mass ratio of copper nitrate hexahydrate to Ce-MOF at 1:1 at different temperatures in O2Linear cyclic voltammograms in saturated 0.1M KOH (scan range-0.9-0.1V, scan rate 10 mv/s);
FIG. 8 is a linear cyclic voltammogram (scan rate: 10mV/s) of the Ce-MOF @ BT-Cu catalyst at different rotation speeds (400, 625, 900, 1225, 1600, 2025 rmp);
FIG. 9 is a K-L curve of the Ce-MOF @ BT-Cu catalyst;
FIG. 10 is a graph of stability tests of Ce-MOF @ BT-Cu catalysts and commercial Pt/C (20 wt% Pt) catalysts by potentiostatic amperometry.
Detailed Description
The invention provides a method for preparing a Ce-MOF @ BT-Cu catalyst, which comprises the following steps:
(1) firstly, preparing a Ce organic frame, weighing a certain amount of trimesic acid white powder, and dissolving the trimesic acid white powder in a certain amount of absolute ethyl alcohol, wherein the dissolved liquid is a colorless transparent solution. Weighing a certain amount of colorless transparent crystals of cerium nitrate hexahydrate, dissolving the crystals in a certain amount of deionized water, wherein the dissolved liquid is colorless transparent liquid. And slowly dripping the trimesic acid solution into cerous nitrate hexahydrate, and stirring on a magnetic stirrer to obtain a white mixture. Transferring the mixture into a water bath kettle, and oscillating the mixture at a certain temperature. Washing the sample obtained after the reaction with deionized water and ethanol for several times, and drying at a certain temperature to obtain white powder Ce-MOF;
(2) respectively dispersing 0.3g of Ce-MOF prepared in the step (1) and 0.3g of plant polyphenol in 30ml of deionized water, and after carrying out ultrasonic treatment at room temperature for 5 minutes, pouring the plant polyphenol solution into the Ce-MOF again for ultrasonic treatment for 30 minutes;
(3) dispersing 0.3g of copper nitrate hexahydrate and 0.3g of plant polyphenol in 30ml of deionized water, carrying out ultrasonic treatment at room temperature for 5 minutes, pouring the ultrasonic solution into the ultrasonic solution obtained in the step (2), and continuing ultrasonic treatment at room temperature for 30 minutes;
(4) washing and centrifuging the product obtained in the step (3) by using deionized water and an ethanol solution, and drying the product in an oven at 60 ℃ for 12 hours to obtain a Ce-MOF @ BT-Cu precursor;
(5) uniformly dispersing a proper amount of dried precursor at the bottom of the porcelain ark, putting the porcelain ark in a tube furnace for high-temperature pyrolysis in an argon or nitrogen atmosphere, directly heating the porcelain ark to 800 ℃ at a heating rate of 5 ℃/min in a pure nitrogen atmosphere, and naturally cooling the porcelain ark to room temperature to obtain the copper polyphenol supermolecular network interface modified rare earth-based organic frame cathode electrocatalyst material Ce-MOF @ BT-Cu.
The invention provides a preparation method of a copper polyphenol supermolecular network interface modified rare earth-based organic framework cathode electrocatalyst material and application of the material as an oxygen reduction catalyst.
The active substance is abbreviated as Ce-MOF @ BT-Cu, and has a uniform granular structure.
The invention uses a carbon rod as a counter electrode, a saturated silver chloride electrode (Ag/AgCl) as a reference electrode and a glassy carbon electrode as a working electrode.
The concentration of Nafion added in the preparation process of the catalyst is 5 percent, and the dosage is 15 ul.
The catalyst preparation method of the invention is to prepare the catalyst ink (ink) by weighing 4mg of the catalyst ink and dispersing the catalyst ink in 1mL of mixed solution (235 uL of deionized water, 735uL of isopropanol and 15uL of 5 wt% Nafion solution). Then, 28uL ink is gradually dripped onto the surface of the glassy carbon electrode (the catalyst loading is 0.25mg cm)-2) And carrying out electrocatalysis performance test after natural drying.
All electrocatalytic performance tests described in the present invention were performed in 0.1M KOH (pH 13.62) electrolyte, and the experimentally measured potential was converted to a potential relative to a Reversible Hydrogen Electrode (RHE) by the following formula:
E(RHE)＝E(Ag/AgCl)+0.059*pH+0.2224
the potential values referred to in the present invention are all potentials relative to the reversible hydrogen electrode.
The catalyst of the present invention requires CV activation for 3 cycles before electrochemical testing.
The catalyst is tested at normal temperature, and the influence of large temperature change difference on the performance of the catalyst is prevented.
The invention will be further illustrated with reference to the following specific examples. For a further understanding of the present invention, preferred embodiments of the present invention are described in conjunction with the examples, but it is to be understood that these descriptions are intended to further illustrate features and advantages of the present invention, and are not intended to limit the claims of the present invention. In addition, it should be understood that various changes or modifications can be made by those skilled in the art after reading the disclosure of the present invention, and such equivalents also fall within the scope of the invention.
The experimental methods used in the following examples are all conventional methods unless otherwise specified; reagents, materials and the like used in the following examples are commercially available unless otherwise specified.
Example 1:
the embodiment shows a preparation method of a copper polyphenol supramolecular network interface modified rare earth-based organic frame negative electrode electrocatalyst material Ce-MOF @ BT-Cu.
(1) Firstly, preparing a Ce-MOF @ BT-Cu polymer substrate, weighing 3.3620g of trimesic acid, dissolving the trimesic acid in 60mL of absolute ethyl alcohol, weighing 6.9480g of cerous nitrate hexahydrate, dissolving the cerous nitrate hexahydrate in 60mL of deionized water, slowly dripping the solution of trimesic acid into the cerous nitrate hexahydrate, and stirring the solution in a magnetic stirrer for 30min to obtain a white mixture. Transferring to 70 ℃ for drying to obtain white powder Ce-MOF;
(2) dispersing 0.3g of Ce-MOF prepared in the step (1) and 0.3g of plant polyphenol in 30mL of deionized water, and carrying out ultrasonic treatment at room temperature for 30 minutes;
(3) dispersing 0.3g of copper nitrate hexahydrate and 0.3g of plant polyphenol in 30mL of deionized water, carrying out ultrasonic treatment at room temperature for 5 minutes, pouring the ultrasonic solution into the ultrasonic solution obtained in the step (2), and continuing ultrasonic treatment for 30 minutes;
(4) washing and centrifuging the product obtained in the step (3) by using deionized water and an ethanol solution, and drying the product in an oven at 70 ℃ for 16 hours to obtain a Ce-MOF @ BT-Cu precursor;
(5) uniformly dispersing a proper amount of dried precursor at the bottom of the porcelain ark, putting the porcelain ark in a tube furnace for high-temperature pyrolysis in an argon or nitrogen atmosphere, directly heating the porcelain ark to 800 ℃ at a heating rate of 5 ℃/min in a pure nitrogen atmosphere, and naturally cooling the porcelain ark to room temperature to obtain the copper polyphenol supermolecular network interface modified rare earth-based organic frame cathode electrocatalyst material Ce-MOF @ BT-Cu.
Phase identification and microstructure and structure characterization of the Ce-MOF @ BT-Cu material obtained in the embodiment are carried out by using a Raman spectrometer, a Fourier transform infrared spectrometer, a powder X-ray diffractometer and an X-ray photoelectron spectrometer to carry out phase identification on the prepared material and using a scanning electron microscope to carry out microstructure and structure characterization on the obtained material.
FIG. 1 is a scanning electron micrograph of a Ce-MOF @ BT-Cu nanocomposite. As can be seen from the figure, the material presents a uniform granular structure, has uniform size and abundant pore channel structures on the surface. This indicates that the free H released from the plant polyphenols penetrates into and etches the Ce-MOF, thereby forming a porous structure inside it to expose more active sites.
FIG. 2 is an XRD pattern of Ce-MOF @ BT-Cu nanocomposite. As can be seen from the figure, a broad diffraction peak is generated at 25 ° 2 θ, which corresponds to the characteristic peak of graphitic carbon, indicating that the material has good graphitization degree after heat treatment. Ce-MOF @ BT-Cu shows strong diffraction peaks at 2 θ of 28.668 °, 33.222 °, 47.692 °, 59.358 °, 69.744 °, 77.077 ° and 79.468 °, and corresponds to (111), (200), (220), (311), (222), (400) and (420) crystal planes of the metal Ce-MOF (PDF #75-0076), respectively.
FIG. 3 is a Raman spectrum of a Ce-MOF @ BT-Cu nanocomposite. Two obvious characteristic peaks of carbon are shown on the graph and respectively belong to D bands (1314-1350 cm)-1) And G belt (1589-1609 cm)-1). Wherein the D band is a dislocation inducing band representing a series of amorphous degrees of carbon atoms such as bond angle disorder, bond length disorder, hybridization, etc., and the G band is a graphitized band corresponding to planar tensile vibration of sp2 hybridized carbon atoms. Ratio of D band to G band (I)D/IG) Was used to evaluate the degree of structural disorder and the calculated Ce-MOF @ BT-Cu strength value was about 0.93.
FIG. 4 is an XPS spectrum full spectrum (a), C spectrum (b), O spectrum (C), N spectrum (d), Ce spectrum (e) and Cu spectrum (f) of the Ce-MOF @ BT-Cu nanocomposite material. The full spectrum chart shows that the material contains elements such as C, O, N, Ce, Cu and the like, and the peak fitting is carried out on C1s, wherein the elements correspond to a carbon-carbon single bond (C-C, 284.8eV), a carbon-oxygen single bond (C-O, 286.2eV) and carboxylic carbon (O-C ═ O, 289.6 eV); the peak separation diagram of O1 s includes a carbon-oxygen single bond (C — O, 529.9eV) and a carbon-oxygen double bond (C ═ O, 532.2 eV); the corresponding peak of N1 s is pyridine nitrogen (400.06eV), wherein the pyridine nitrogen can increase the initial potential of ORR; peak-splitting fitting of Ce3dThe results show that Ce is simultaneously present on the surface of the catalyst4+、Ce3+Two valence states, 882.47eV, 889.17eV, 898.37eV corresponding to Ce3d5/2The main peaks, 901.11eV, 907.55eV and 916.76eV correspond to Ce3d3/2A main peak. The peak fitting result of the Cu 2p shows that the Cu element exists in the sample in the form of monovalent copper, wherein 929.14eV and 948.88eV respectively correspond to the Cu 2p3/2Main peak and its satellite peak and Cu 2p1/2A main peak. In the above conclusion, the formation of Ce-MOF @ BT-Cu was demonstrated.
Example 2:
the embodiment shows the electrochemical performance research of a copper polyphenol supramolecular network interface modified rare earth-based organic frame negative electrode electrocatalyst material Ce-MOF @ BT-Cu as a catalyst.
The invention uses a carbon rod as a counter electrode, saturated silver chloride electrodes (Ag/AgCl) as reference electrodes and glassy carbon electrodes as working electrodes.
The concentration of Nafion added in the preparation process of the catalyst is 5 wt%, and the dosage is 15 ul.
The electrode pretreatment in the test process of the invention is to add alpha-Al on a nylon polishing cloth base2O3Polishing the electrode polishing powder and a small amount of deionized water on a rotating disk electrode in an 8-shaped manner for 10 minutes, cleaning residual powder on the electrode with deionized water, and naturally drying to finish the treatment.
The catalyst is prepared by dispersing 4mg of the catalyst in a 1mL centrifuge tube by using a balance, adding 235uL of deionized water, 735uL of isopropanol and 15uL of 5 wt% Nafion solution, and then performing ultrasonic treatment at room temperature for 50 minutes to obtain the catalyst ink (ink). Then gradually dropping 28uL ink on the surface of the glassy carbon electrode (catalyst loading amount is 0.25mg cm)-2) And carrying out electrocatalysis performance test after natural drying.
All electrocatalytic performance tests described in the present invention were performed in 0.1M KOH (pH 13.62) electrolyte, and the experimentally measured potential was converted to a potential relative to a Reversible Hydrogen Electrode (RHE) by the following formula:
E(RHE)＝E(Ag/AgCl)+0.059*pH+0.2224
the potential values referred to in the present invention are all potentials relative to the reversible hydrogen electrode.
The catalyst of the invention requires CV activation for 3 cycles before electrochemical testing.
The catalyst is tested at normal temperature, and the influence of large temperature change difference on the performance of the catalyst is prevented.
Nafion added in the preparation process of the catalyst is produced by Aldrich sigma company, and the concentration is 5%.
The catalyst is absorbed by a pipette with 7ul and dripped on the working electrode, the step is repeated for 3 times after the catalyst is naturally aired, the working electrode is slowly immersed into 0.1M KOH electrolyte saturated by oxygen, bubbles are prevented from being generated on the working electrode in the step, and the electrolyte is continuously introduced with oxygen in the whole test process to ensure oxygen saturation.
Cyclic voltammetry and linear cyclic voltammetry tests were performed on the catalyst obtained in this example by performing cyclic voltammetry experiments using an electrochemical workstation manufactured by Pine, usa, at a test voltage sweep range of-0.9 to 0.1V and a sweep rate of 50mV/s, and during the tests, the catalyst was activated for 3 cycles with a current density of 50mV/s and then subjected to cyclic voltammetry tests. Linear cyclic voltammetry was also performed using a Pine electrochemical workstation with a test voltage sweep range of-0.9-0.1V and a sweep rate of 50 mV/s. The current density of the catalyst material under different rotating speeds can be obtained by rotating speed test, the number of transferred electrons can be obtained by utilizing a K-L equation, the test current density is 10mV/s, and the rotating speeds are 400, 625, 900, 1225, 1600 and 2025 rmp. The stability and the methanol tolerance are also important indexes of the catalyst performance, the test is also completed on an electrochemical workstation, the stability test voltage is-0.189V, and the test time length is 20000 s; the methanol tolerance test voltage was-0.189V, the test duration was 1000s, and a 3M methanol solution was dropped at 300 s.
FIG. 5 is a graph showing the cyclic voltammetry characteristics of the Ce-MOF @ BT-Cu catalyst (test voltage sweep range: -0.9-0.1V, sweep rate: 50mV/s) at O2In a saturated electrolyte at 0And a clear cathode oxygen reduction peak exists at 64V, which indicates that the catalytic oxygen reduction reaction occurs, and the response to oxygen indicates that the Ce-MOF @ BT-Cu has clear oxygen reduction catalytic activity in an alkaline solution.
FIG. 6 is a linear cyclic voltammogram of the Ce-MOF @ BT-Cu catalyst at different temperatures (test voltage range: -0.9-0.1V, scanning speed: 10mV/s), respectively, and the Ce-MOF @ BT-Cu catalyst performs optimally when the calcination temperature is 800 ℃.
FIG. 7 is Ce-MOF @ BT-Cu in O at different Cu loadings2The linear cyclic voltammogram in saturated 0.1M KOH (the scanning range is-0.9-0.1V, the scanning speed is 10mv/s), the mass ratio of Ce-MOF to copper nitrate hexahydrate is 1:2, 1:1, 2:1 and 3:1 respectively, and as can be seen from the chart, under the heat treatment temperature of 800 ℃, the oxygen reduction catalytic performance of the nano composite material is obviously improved along with the increase of Cu loading, the initial potential and the half-wave potential are obviously improved, and the limiting current density is 1.61mAcm2Increasing to 7.64mAcm2The ORR performance of the material reaches the optimum when the loading is 1: 1.
FIG. 8 is a linear cyclic voltammogram (scan rate: 10mV/s) of the Ce-MOF @ BT-Cu catalyst at different rotation speeds (400, 625, 900, 1225, 1600, 2025rmp), and it can be seen that the limiting diffusion current density of the catalyst is gradually increased with the rotation speed, because the diffusion rate of oxygen is faster with the rotation speed, which shows that the oxygen reduction catalysis process is controlled by mass transfer and conforms to the first order kinetic reaction.
FIG. 9 is a K-L curve of the Ce-MOF @ BT-Cu catalyst, and by linear fitting of the corresponding current density and rotation speed at different voltages, it can be seen that the slope of the curve remains substantially constant over the whole scanning potential range, which means that the oxygen reduction has the same number of transferred electrons at different potentials under the action of the catalyst. According to the RRDE test result, the oxygen reduction catalysis process of the Ce-MOF @ BT-Cu catalyst in the alkaline electrolyte belongs to a four-electron transfer process in a potential range of 0.2V to 0.4V.
FIG. 10 is a chronoamperometric assay of Ce-MOF300@BT-Cu300800 ℃ and Pt/C, in test 20After 000s, there was a significant 23% loss in the initial current density of the Pt/C catalyst compared to a 16% reduction in the Ce-MOF @ BT-Cu catalyst, indicating that the catalyst has better stability than the commercial Pt/C catalyst.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. A preparation method of a copper polyphenol supramolecular network interface modified rare earth-based organic frame cathode material is characterized by comprising the following steps:
(1) and (3) preparing the Ce-MOF polymer substrate, namely weighing a certain amount of trimesic acid white powder, dissolving the trimesic acid white powder in a certain amount of absolute ethyl alcohol, wherein the dissolved liquid is a colorless transparent solution. Weighing a certain amount of colorless transparent crystals of cerium nitrate hexahydrate, dissolving the crystals in a certain amount of deionized water, wherein the dissolved liquid is colorless transparent liquid. Then, the trimesic acid solution was slowly dropped into the cerium nitrate hexahydrate, and stirred on a magnetic stirrer to obtain a white mixture. Transferring the mixture into a water bath kettle, and oscillating the mixture at a certain temperature. Washing the sample obtained after the reaction with deionized water and ethanol for several times, and drying at a certain temperature to obtain white powder Ce-MOF;
(2) dispersing the Ce-MOF prepared in the step (1) and plant polyphenol in deionized water, and carrying out ultrasound at room temperature;
(3) dispersing copper nitrate hexahydrate and plant polyphenol in deionized water, carrying out ultrasonic treatment at room temperature, pouring the solution subjected to ultrasonic treatment into the solution subjected to ultrasonic treatment in the step (2), and carrying out ultrasonic reaction at room temperature;
(4) washing and centrifuging the product obtained in the step (3) by using deionized water and an ethanol solution, and drying the product in an oven to obtain Ce-MOF @ BT-Cu;
(5) and uniformly dispersing a proper amount of dried precursor at the bottom of the porcelain ark, putting the porcelain ark into a tubular furnace for high-temperature pyrolysis in an argon or nitrogen atmosphere, and naturally cooling to room temperature to obtain the copper polyphenol supermolecular network interface modified rare earth-based organic frame cathode electrocatalyst material.
2. The preparation method of the copper polyphenol supramolecular network interface modified rare earth-based organic framework negative electrode electrocatalyst material as claimed in claim 1, wherein the ultrasonic time is 5-10 minutes in step (1), the material is stirred on a magnetic stirrer for 30min, vibrated at 60 ℃ for 1h, and dried at 60-80 ℃ for 13-20 h.
3. The preparation method of the copper polyphenol supramolecular network interface modified rare earth-based organic framework negative electrode electrocatalyst material according to claim 1, wherein the mass ratio of the plant polyphenol to the Ce-MOF in the step (2) is 1:1, and the ultrasonic time is 30-40 minutes.
4. The preparation method of the copper polyphenol supramolecular network interface modified rare earth-based organic framework negative electrode electrocatalyst material according to claim 1, wherein the addition amount of the plant polyphenol in the step (3) is the same as that in the step (2), and the ultrasonic time is 30-40 minutes.
5. The preparation method of the copper polyphenol supramolecular network interface modified rare earth-based organic framework cathode electrocatalyst material according to claim 1, wherein the drying temperature in the step (4) is 60-80 ℃, and the drying time is 16 hours.
6. The preparation method of the copper polyphenol supramolecular network interface modified rare earth-based organic framework cathode electrocatalyst material according to claim 1, characterized in that the high-temperature pyrolysis in the step (5) is specifically that under the atmosphere of pure argon or nitrogen, the material is directly heated to 800 ℃ at a heating rate of 5 ℃/min, and is naturally cooled to room temperature after being kept at the temperature for 2 hours.
7. The copper polyphenol supramolecular network interface modified rare earth-based organic framework cathode electrocatalyst material prepared by the preparation method of any one of claims 1-5.
8. The application of the copper polyphenol supramolecular network interface modified rare earth-based organic frame cathode electrocatalyst material disclosed in claim 6 in a fuel cell is characterized in that the copper polyphenol supramolecular network interface modified rare earth-based organic frame electrocatalyst material is used as a part of a cathode material of the fuel cell, and the cathode material is prepared by uniformly mixing the copper polyphenol supramolecular network interface modified rare earth-based organic frame cathode material with isopropanol, deionized water and a Nifion solution.
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