Preparation method and application of MOF-derived CuAl/N-C catalyst
阅读说明：本技术 一种MOF衍生的CuAl/N-C催化剂的制备方法和应用 (Preparation method and application of MOF-derived CuAl/N-C catalyst ) 是由 王志江 单晶晶 于 2020-12-17 设计创作，主要内容包括：一种MOF衍生的CuAl/N-C催化剂的制备方法和应用,它涉及一种MOF衍生的催化剂的制备方法和应用。本发明要解决现有以MOFs为前驱体衍生的双金金属/碳化物,双金属之间掺杂很难实现原子位置的精确控制或者替代,且大多数是用于电催化还原CO-2产CO,而不能进一步还原为C-2H-4；解决现有Cu催化还原CO-2产C-2H-4时,存在C-2H-4的法拉第效率差、电流密度低及竞争析氢反应严重的问题。制备方法：一、称取；二、制备前驱体盐溶液；三、制备CuAl-MOFs；四、制备CuAl/N-C。本发明用于MOF衍生的CuAl/N-C催化剂的制备方法和应用。(A preparation method and application of a MOF derived CuAl/N-C catalyst relate to a preparation method and application of a MOF derived catalyst. The invention aims to solve the problems that the existing double-metal/carbide derived by taking MOFs as precursors is difficult to realize accurate control or substitution of atomic positions by doping between double metals, and most of the double metals are used for electrocatalytic reduction of CO 2 CO is produced but cannot be further reduced to C 2 H 4 (ii) a Solves the problem of the existing Cu catalytic reduction CO 2 Produce C 2 H 4 When there is C 2 H 4 The problems of poor Faraday efficiency, low current density and serious competitive hydrogen evolution reaction. The preparation method comprises the following steps: firstly, weighing; secondly, preparing a precursor salt solution; thirdly, preparing CuAl-MOFs; and fourthly, preparing CuAl/N-C. The invention discloses a preparation method of a CuAl/N-C catalyst for MOF derivationMethods and uses.)
1. A preparation method of MOF derived CuAl/N-C catalyst is characterized by comprising the following steps:
firstly, weighing:
weighing a deprotonation reagent, an organic solvent, a ligand, a copper salt and an aluminum salt;
the volume ratio of the substance amount of the deprotonation reagent to the organic solvent is (1.2-7.2) mmol:35 mL; the volume ratio of the substance amount of the ligand to the organic solvent is (0.3-1.2) mmol:35 mL; the molar ratio of the copper salt to the aluminum salt is (0.1-99) 1; the volume ratio of the sum of the amounts of the copper salt and the aluminum salt to the organic solvent is (1.2-2.4) mmol:35 mL;
secondly, preparing a precursor salt solution:
dissolving the ligand, copper salt and aluminum salt weighed in the step one in an organic solvent to obtain a precursor salt solution;
thirdly, preparing CuAl-MOFs:
adding the deprotonation reagent weighed in the step one into the precursor salt solution, stirring and reacting for 1-24 h under the condition that the rotating speed is 200-1000 rpm, and then separating, cleaning and drying reactants to obtain CuAl-MOFs powder;
fourthly, preparing CuAl/N-C:
placing CuAl-MOFs powder in a porcelain boat, then placing the porcelain boat in a tube furnace, heating the porcelain boat to 450-1000 ℃ at a heating rate of 2-10 ℃/min under protective gas, and then preserving heat for 1-6 h under the condition that the temperature is 450-1000 ℃ to obtain the MOF-derived CuAl/N-C catalyst.
2. The process of claim 1, wherein the deprotonating agent in step one is sodium hydroxide, triethylamine or sodium methoxide.
3. The process of claim 1, wherein the copper salt in step one is Cu (CH)3COO)2、CuCl2·2H2O or Cu (NO)3)2·3H2O。
4. The process of claim 1, wherein the aluminum salt in step one is Al (NO)3)3·9H2O、AlCl3·6H2O or Al (C)3H7O)3。
5. The process of claim 1, wherein the organic solvent in step one is DMF, DMA or DEF.
6. The process of claim 1, wherein the ligand in step one is 2-aminoterephthalic acid, 2, 5-dihydroxyterephthalic acid, or terephthalic acid.
7. The method for preparing the MOF-derived CuAl/N-C catalyst according to claim 1, wherein the washing and drying in the third step is 3 to 5 times by using DMF reagent, and then vacuum drying is carried out at a temperature of 25 to 120 ℃.
8. The method for preparing the MOF-derived CuAl/N-C catalyst according to claim 1, wherein the shielding gas in the fourth step is a mixed gas of hydrogen and argon, nitrogen or argon; the volume percentage of the hydrogen in the mixed gas of the hydrogen and the argon is 1 to 10 percent.
9. Use of a MOF-derived CuAl/N-C catalyst prepared by the process of claim 1 as a cathode catalyst for preparing a working electrode for electrocatalytic reduction of CO2System C of2H4。
10. Use of a MOF-derived CuAl/N-C catalyst according to claim 9, characterized in that the working electrode is prepared by the following steps:
suspending the MOF-derived CuAl/N-C catalyst in ethanol, adding 5 mass percent of Nafion solution, ultrasonically oscillating for 30-60 min to obtain uniform ink-like mixed solution, and uniformly spraying the uniform ink-like mixed solution on the surface of the carbon paper by using a spray gun, wherein the spraying amount of the MOF-derived CuAl/N-C catalyst is 0.05mg/cm2～3mg/cm2Drying at 25-120 deg.c to obtain the gas diffusion working electrode;
the volume ratio of the mass of the MOF-derived CuAl/N-C catalyst to the volume of the ethanol is 10mg (600-1500) mu L; the volume ratio of the mass of the MOF-derived CuAl/N-C catalyst to a Nafion solution with the mass percentage of 5% is 10mg (20-60) mu L.
Technical Field
The invention relates to a preparation method and application of a MOF derived catalyst.
Background
Electrochemical reduction of CO2The technology is that the method can be carried out at normal temperature and normal pressure and can lead CO to be generated2Conversion to valuable fuels or chemicals, e.g. CH3OH、CH4、C2H4Etc. the reaction condition is mild, high temperature and high pressure are not needed, the equipment operation is flexible, and the electrolysis condition can be simply changedTo control product selectivity and reaction rate, is believed to be CO2The transformation technology with the most development prospect in resource utilization. However, due to CO2The molecule has stable chemical property, and high energy is needed for activation and bond breaking, and the technologies such as thermal conversion, photochemistry and electrochemistry need additional catalysts to reduce energy consumption and improve reaction speed, so that the electrochemistry CO is used for preparing the catalyst for the electrochemical CO2One of the most critical technical problems in the reduction process is how to prepare an electrocatalyst with high catalytic activity.
The common catalysts at present are: metal catalysts, non-metal catalysts, and molecular catalysts. Compared with the high price and low reserves of metals, non-metals, especially carbon materials, are widely available and much cheaper, and thus attract the attention of some researchers. The metal is loaded on the nonmetal substrate, the nonmetal substrate can help to reduce the metal usage amount and improve the metal utilization rate, metal nanoparticles are stabilized and dispersed, and the electron cloud structure of the metal catalyst is changed through a support effect, so that the activity selectivity of the catalyst is improved. Recently, Metal Organic Frameworks (MOFs) with high porosity and programmable metal clusters and organic linkers have proven to be ideal templates for the fabrication of various carbon-based nanomaterials (including porous carbons) and metal/metal oxide modified porous carbons, and more research has been conducted primarily for electrocatalytic oxygen reduction or CO2Catalytic hydrogenation reduction for CO reduction by electrocatalyst2The reaction was less studied. In addition, most MOF derived materials are prepared as single metal/carbon catalysts. In order to further improve the performance of transition metal-based catalysts, designing bimetallic catalysts with synergistic effects is considered to be an important way to further improve the catalyst performance. Because of mutual coupling action between the double metals, the electrocatalytic performance of the double metals is greatly improved compared with that of single metals. However, due to the influence of the crystal structure of the conventional transition metals, their doping makes it difficult to achieve precise control or substitution of the atomic position. This results in their performance still not being regulated most efficiently. At present, the double-gold metal/carbide derived by taking MOFs as a precursor is used for reducing CO in electrocatalysis2The application of the aspect is less, and most of the aspect is used for electrocatalysisCrude CO2Producing CO which cannot be further reduced to more valuable hydrocarbons, such as C2H4。
At present, copper-based catalysts are recognized for the electrocatalytic reduction of CO with good selectivity to hydrocarbons in aqueous solution2The material of (1). But in the catalytic process, C is present2H4The problems of poor Faraday efficiency, low current density, serious competitive Hydrogen Evolution Reaction (HER), and the like. Therefore, improving the reactivity and product selectivity of copper-based catalysts is an important task for achieving efficient carbon dioxide reduction.
Disclosure of Invention
The invention aims to solve the problems that the existing double-metal/carbide derived by taking MOFs as precursors is difficult to realize accurate control or substitution of atomic positions by doping between double metals, and most of the double metals are used for electrocatalytic reduction of CO2CO is produced but cannot be further reduced to C2H4(ii) a Solves the problem of the existing Cu catalytic reduction CO2Produce C2H4When there is C2H4The problems of poor Faraday efficiency, low current density and serious competitive hydrogen evolution reaction, and provides a preparation method and application of a MOF derived CuAl/N-C catalyst.
A preparation method of an MOF-derived CuAl/N-C catalyst comprises the following steps:
firstly, weighing:
weighing a deprotonation reagent, an organic solvent, a ligand, a copper salt and an aluminum salt;
the volume ratio of the substance amount of the deprotonation reagent to the organic solvent is (1.2-7.2) mmol:35 mL; the volume ratio of the substance amount of the ligand to the organic solvent is (0.3-1.2) mmol:35 mL; the molar ratio of the copper salt to the aluminum salt is (0.1-99) 1; the volume ratio of the sum of the amounts of the copper salt and the aluminum salt to the organic solvent is (1.2-2.4) mmol:35 mL;
secondly, preparing a precursor salt solution:
dissolving the ligand, copper salt and aluminum salt weighed in the step one in an organic solvent to obtain a precursor salt solution;
thirdly, preparing CuAl-MOFs:
adding the deprotonation reagent weighed in the step one into the precursor salt solution, stirring and reacting for 1-24 h under the condition that the rotating speed is 200-1000 rpm, and then separating, cleaning and drying reactants to obtain CuAl-MOFs powder;
fourthly, preparing CuAl/N-C:
placing CuAl-MOFs powder in a porcelain boat, then placing the porcelain boat in a tube furnace, heating the porcelain boat to 450-1000 ℃ at a heating rate of 2-10 ℃/min under protective gas, and then preserving heat for 1-6 h under the condition that the temperature is 450-1000 ℃ to obtain the MOF-derived CuAl/N-C catalyst.
Application of MOF-derived CuAl/N-C catalyst in preparing working electrode by taking MOF-derived CuAl/N-C catalyst as cathode catalyst for electrocatalytic reduction of CO2System C of2H4。
The invention has the beneficial effects that:
firstly, copper-based MOFs materials are selected as research objects, main group metal Al and Cu are selected for alloying, bimetallic MOF is prepared firstly, and then the bimetallic MOF is cracked at high temperature to form CuAl/N-C materials. Finally, preparation of MOF-derived CuAl/N-C catalyst for CO2Electrocatalytic reduction of C2H4Has higher activity and selectivity.
Secondly, CuAl alloy in the MOF-derived CuAl/N-C catalyst is uniformly distributed, so that the problem that precise control or replacement of atomic positions is difficult to realize by doping between existing double metals is solved, the size of alloy particles is about 150 nm-250 nm, the particles are well combined with carbon, and the electronic transmission in the catalysis process is facilitated;
the MOF-derived CuAl/N-C catalyst prepared by the invention shows a remarkable alloy effect, and the addition of Al changes the electronic state density of Cu and can effectively improve the C-C ratio of Cu2H4While suppressing other products (e.g. H)2CO and C2H4) Generating; when the molar ratio of Cu to Al in the CuAl/N-C catalyst is 9:1, the current density is 150mA/cm2When, C2H4The highest Faraday efficiency can reach 50 percent1.35 times the MOF-derived Cu/N-C.
The invention relates to a preparation method and application of a MOF-derived CuAl/N-C catalyst.
Drawings
FIG. 1 is an SEM image of a MOF-derived Cu/N-C catalyst prepared in comparative experiment one;
FIG. 2 is an SEM image of a MOF-derived CuAl/N-C catalyst prepared in example one;
FIG. 3 is an SEM image of a MOF-derived CuAl/N-C catalyst prepared in example two;
FIG. 4 is an SEM image of a MOF-derived CuAl/N-C catalyst prepared in example three;
FIG. 5 is an EDS-Mapping plot of the MOF-derived CuAl/N-C catalyst prepared in example two, a being a STEM plot, b being a Cu element, C being an Al element, d being an N element, e being an O element, f being a C element;
FIG. 6 is an XRD pattern for 1 the MOF-derived CuAl/N-C catalyst prepared in example one, 2 the MOF-derived CuAl/N-C catalyst prepared in example two, 3 the MOF-derived CuAl/N-C catalyst prepared in example three, and 4 the MOF-derived Cu/N-C catalyst prepared in comparative experiment one;
FIG. 7 is a current density plot, 1 for the MOF-derived Cu/N-C catalyst prepared in comparative experiment one and 2 for the MOF-derived CuAl/N-C catalyst prepared in example two;
FIG. 8 is an MOF-derived Cu/N-C catalyst electrocatalytic reduction of CO prepared in comparative experiment one2Faraday efficiency-Current Density plot for each product, 1 is H22 is CO and 3 is CH4And 4 is C2H4；
FIG. 9 is an MOF-derived CuAl/N-C catalyst electrocatalytic reduction of CO prepared in example one2Faraday efficiency-Current Density plot for each product, 1 is H22 is CO and 3 is CH4And 4 is C2H4；
FIG. 10 is an MOF-derived CuAl/N-C catalyst electrocatalytic reduction of CO prepared in example two2Faraday efficiency-Current Density plot for each product, 1 is H22 is CO and 3 is CH4And 4 is C2H4；
FIG. 11 is an MOF-derived CuAl/N-C catalyst electrocatalytic reduction of CO prepared in EXAMPLE III2Faraday efficiency-Current Density plot for each product, 1 is H22 is CO and 3 is CH4And 4 is C2H4；
FIG. 12 shows electrocatalytic reduction of CO2System C of2H4Faraday efficiency vs. current density plot, 1 is the MOF-derived CuAl/N-C catalyst prepared in example one, 2 is the MOF-derived CuAl/N-C catalyst prepared in example two, 3 is the MOF-derived CuAl/N-C catalyst prepared in example three, and 4 is the MOF-derived Cu/N-C catalyst prepared in comparative experiment one.
Detailed Description
The first embodiment is as follows: the preparation method of the MOF-derived CuAl/N-C catalyst comprises the following steps:
firstly, weighing:
weighing a deprotonation reagent, an organic solvent, a ligand, a copper salt and an aluminum salt;
the volume ratio of the substance amount of the deprotonation reagent to the organic solvent is (1.2-7.2) mmol:35 mL; the volume ratio of the substance amount of the ligand to the organic solvent is (0.3-1.2) mmol:35 mL; the molar ratio of the copper salt to the aluminum salt is (0.1-99) 1; the volume ratio of the sum of the amounts of the copper salt and the aluminum salt to the organic solvent is (1.2-2.4) mmol:35 mL;
secondly, preparing a precursor salt solution:
dissolving the ligand, copper salt and aluminum salt weighed in the step one in an organic solvent to obtain a precursor salt solution;
thirdly, preparing CuAl-MOFs:
adding the deprotonation reagent weighed in the step one into the precursor salt solution, stirring and reacting for 1-24 h under the condition that the rotating speed is 200-1000 rpm, and then separating, cleaning and drying reactants to obtain CuAl-MOFs powder;
fourthly, preparing CuAl/N-C:
placing CuAl-MOFs powder in a porcelain boat, then placing the porcelain boat in a tube furnace, heating the porcelain boat to 450-1000 ℃ at a heating rate of 2-10 ℃/min under protective gas, and then preserving heat for 1-6 h under the condition that the temperature is 450-1000 ℃ to obtain the MOF-derived CuAl/N-C catalyst.
In the first step, the organic solvent is DMF (N, N-dimethylformamide), DMA (N, N-dimethylacetamide) or DEF (N, N-diethylformamide).
The embodiment adopts a simple chemical synthesis method to form the CuAl-MOFs material, and prepares the derived CuAl/N-C electrocatalyst through pyrolysis. Preparing synthesized MOF-derived CuAl/N-C material into cathode catalyst for electrocatalytic reduction of CO2System C of2H4. The synthesized MOF-derived CuAl/N-C material has simple process operation, safety, reliability and low cost, and is used for CO2Electrocatalytic reduction of C2H4The catalyst has high activity and selectivity, good stability and good popularization and application prospect.
The beneficial effects of the embodiment are as follows:
firstly, copper-based MOFs materials are selected as research objects, main group metals Al and Cu are selected for alloying, and the bimetallic MOF is prepared and then is cracked at high temperature to form CuAl/N-C materials. Finally, preparation of MOF-derived CuAl/N-C catalyst for CO2Electrocatalytic reduction of C2H4Has higher activity and selectivity.
Secondly, CuAl alloy in the MOF-derived CuAl/N-C catalyst prepared by the embodiment is uniformly distributed, so that the problem that precise control or replacement of atomic positions is difficult to realize by doping between existing double metals is solved, the size of alloy particles is about 150 nm-250 nm, the particles are well combined with carbon, and the electron transmission in a catalysis process is facilitated;
the MOF-derived CuAl/N-C catalyst prepared by the embodiment shows a remarkable alloy effect, and the addition of Al changes the electronic state density of Cu and can effectively improve the C-C ratio of Cu2H4While suppressing other products (e.g. H)2CO and C2H4) Generating; when the molar ratio of Cu to Al in the CuAl/N-C catalyst is 9:1, the current density is 150mA/cm2When, C2H4The highest Faraday efficiency can reach 50 percent, which is 1.35 times that of the MOF derived Cu/N-C.
The second embodiment is as follows: the first difference between the present embodiment and the specific embodiment is: the deprotonating reagent in the first step is sodium hydroxide, triethylamine or sodium methoxide. The rest is the same as the first embodiment.
The third concrete implementation mode: this embodiment is different from the first or second embodiment in that: the copper salt in the step one is Cu (CH)3COO)2、CuCl2·2H2O or Cu (NO)3)2·3H2And O. The other is the same as in the first or second embodiment.
The fourth concrete implementation mode: the difference between this embodiment mode and one of the first to third embodiment modes is: the aluminum salt in the first step is Al (NO)3)3·9H2O、AlCl3·6H2O or Al (C)3H7O)3. The others are the same as the first to third embodiments.
The fifth concrete implementation mode: the difference between this embodiment and one of the first to fourth embodiments is: the organic solvent in the first step is DMF, DMA or DEF. The rest is the same as the first to fourth embodiments.
The sixth specific implementation mode: the difference between this embodiment and one of the first to fifth embodiments is: the ligand in the first step is 2-amino terephthalic acid, 2, 5-dihydroxy terephthalic acid or terephthalic acid. The rest is the same as the first to fifth embodiments.
The seventh embodiment: the difference between this embodiment and one of the first to sixth embodiments is: the washing and drying in the third step is washing 3-5 times with DMF reagent and vacuum drying at 25-120 deg.c. The others are the same as the first to sixth embodiments.
The specific implementation mode is eight: the present embodiment differs from one of the first to seventh embodiments in that: the protective gas in the fourth step is a mixed gas of hydrogen and argon, nitrogen or argon; the volume percentage of the hydrogen in the mixed gas of the hydrogen and the argon is 1 to 10 percent. The rest is the same as the first to seventh embodiments.
The specific implementation method nine: in the application of the MOF-derived CuAl/N-C catalyst, the MOF-derived CuAl/N-C catalyst is used as a cathode catalyst to prepare a working electrode for electrocatalytic reduction of CO2System C of2H4。
The method for preparing the working electrode is simple to operate, the CuAl-MOFs is used as a precursor, the derived CuAl/N-C is obtained through pyrolysis, pretreatment is not needed, carbon paper is used as a catalyst carrier, strong acid and strong alkali treatment is not needed, and the consumption of raw materials is low.
The detailed implementation mode is ten: the present embodiment differs from the ninth embodiment in that: the working electrode is prepared by the following steps:
suspending the MOF-derived CuAl/N-C catalyst in ethanol, adding 5 mass percent of Nafion solution, ultrasonically oscillating for 30-60 min to obtain uniform ink-like mixed solution, and uniformly spraying the uniform ink-like mixed solution on the surface of the carbon paper by using a spray gun, wherein the spraying amount of the MOF-derived CuAl/N-C catalyst is 0.05mg/cm2～3mg/cm2Drying at 25-120 deg.c to obtain the gas diffusion working electrode;
the volume ratio of the mass of the MOF-derived CuAl/N-C catalyst to the volume of the ethanol is 10mg (600-1500) mu L; the volume ratio of the mass of the MOF-derived CuAl/N-C catalyst to a Nafion solution with the mass percentage of 5% is 10mg (20-60) mu L. The rest is the same as the embodiment nine.
The following examples were used to demonstrate the beneficial effects of the present invention:
the first embodiment is as follows:
a preparation method of an MOF-derived CuAl/N-C catalyst comprises the following steps:
firstly, weighing:
weighing a deprotonation reagent, an organic solvent, a ligand, a copper salt and an aluminum salt;
the volume ratio of the substance of the deprotonation reagent to the organic solvent is 3.6mmol:35 mL; the volume ratio of the substance amount of the ligand to the organic solvent is 0.6mmol:35 mL; the molar ratio of the copper salt to the aluminum salt is 17: 1; the volume ratio of the sum of the amounts of the copper salt and the aluminum salt to the organic solvent is 1.8mmol:35 mL;
secondly, preparing a precursor salt solution:
dissolving the ligand, copper salt and aluminum salt weighed in the step one in an organic solvent to obtain a precursor salt solution;
thirdly, preparing CuAl-MOFs:
adding the deprotonation reagent weighed in the step one into the precursor salt solution, stirring and reacting for 3.5 hours under the condition that the rotating speed is 600rpm, and then separating, cleaning and drying reactants to obtain CuAl-MOFs powder;
fourthly, preparing CuAl/N-C:
placing CuAl-MOFs powder in a porcelain boat, then placing in a tube furnace, heating to 800 ℃ at the heating rate of 4 ℃/min under protective gas, and then preserving heat for 3h under the temperature of 800 ℃ to obtain the MOF-derived CuAl/N-C catalyst.
The deprotonating reagent in step one is triethylamine.
The copper salt in the step one is Cu (NO)3)2·3H2O。
The aluminum salt in the first step is Al (NO)3)3·9H2O。
The organic solvent in the first step is DMF (N, N-dimethylformamide).
The ligand in the first step is 2-amino terephthalic acid.
The washing and drying in the third step are carried out for 4 times by using a DMF reagent, and then the vacuum drying is carried out under the condition that the temperature is 80 ℃; the protective gas in the fourth step is nitrogen.
Example two: the difference between the present embodiment and the first embodiment is: the molar ratio of the copper salt to the aluminum salt is 9: 1. The rest is the same as the first embodiment.
Example three: the difference between the present embodiment and the first embodiment is: the molar ratio of the copper salt to the aluminum salt is 5.6: 1. The rest is the same as the first embodiment.
Comparison experiment one:
a preparation method of an MOF-derived Cu/N-C catalyst is carried out according to the following steps:
firstly, weighing:
weighing a deprotonation reagent, an organic solvent, a ligand and copper salt;
the volume ratio of the substance of the deprotonation reagent to the organic solvent is 3.6mmol:35 mL; the volume ratio of the substance amount of the ligand to the organic solvent is 0.6mmol:35 mL; the volume ratio of the substance of the copper salt to the organic solvent is 1.8mmol:35 mL;
secondly, preparing a precursor salt solution:
dissolving the ligand and the copper salt weighed in the step one in an organic solvent to obtain a precursor salt solution;
thirdly, preparing CuAl-MOFs:
adding the deprotonation reagent weighed in the step one into the precursor salt solution, stirring and reacting for 3.5 hours under the condition that the rotating speed is 600rpm, and then separating, cleaning and drying reactants to obtain Cu-MOFs powder;
fourthly, preparing Cu/N-C:
placing Cu-MOFs powder in a porcelain boat, then placing the porcelain boat in a tube furnace, heating the porcelain boat to 800 ℃ at a heating rate of 4 ℃/min under protective gas, and then preserving heat for 3h under the condition that the temperature is 800 ℃ to obtain the MOF-derived Cu/N-C catalyst.
The deprotonating reagent in step one is triethylamine.
The copper salt in the step one is Cu (NO)3)2·3H2O。
The organic solvent in the first step is DMF (N, N-dimethylformamide).
The ligand in the first step is 2-amino terephthalic acid.
The washing and drying in the third step are carried out for 4 times by using a DMF reagent, and then the vacuum drying is carried out under the condition that the temperature is 80 ℃; the protective gas in the fourth step is nitrogen.
FIG. 1 is an SEM image of a MOF-derived Cu/N-C catalyst prepared in comparative experiment one; as can be seen, the MOF-derived Cu/N-C catalyst has nanoscale metal particles uniformly dispersed on a carbon matrix, with an average size of about 350 nm.
FIG. 2 is an SEM image of a MOF-derived CuAl/N-C catalyst prepared in example one; it can be seen from the figure that, after Al is added, in the MOF-derived CuAl/N-C catalyst prepared in example one, the size of the metal alloy particles is significantly reduced, the particles are more uniform, about 200nm, the smaller the particle size, the more active sites are exposed by the catalyst, and the better the performance is;
FIG. 3 is an SEM image of a MOF-derived CuAl/N-C catalyst prepared in example two; as can be seen from the figure, the MOF-derived CuAl/N-C catalyst prepared in example two has uniform combination of metal alloy particles with nanometer scale and carbon matrix, the size of the particles is significantly reduced, about 150nm, and the particles have good dispersibility, which is beneficial to the transmission of electrons in the catalytic process;
FIG. 4 is an SEM image of a MOF-derived CuAl/N-C catalyst prepared in example three; it is seen from the figure that the MOF-derived CuAl/N-C catalyst prepared in example three has a nano-sized metal alloy particle size that is increased to about 250nm relative to examples one and two.
FIG. 5 is an EDS-Mapping plot of the MOF-derived CuAl/N-C catalyst prepared in example two, a being a STEM plot, b being a Cu element, C being an Al element, d being an N element, e being an O element, f being a C element; as can be seen from the figure, the distribution ranges of Cu (yellow), aluminum (blue), N (red), O (green), and C (violet) almost completely overlap and are uniformly distributed.
XRD testing was performed on the MOF-derived CuAl/N-C catalysts prepared in examples one to three and the MOF-derived Cu/N-C catalyst prepared in comparative experiment one, and the results are shown in FIG. 6 below, where FIG. 6 is an XRD pattern, 1 is the MOF-derived CuAl/N-C catalyst prepared in example one, 2 is the MOF-derived CuAl/N-C catalyst prepared in example two, 3 is the MOF-derived CuAl/N-C catalyst prepared in example three, and 4 is the MOF-derived Cu/N-C catalyst prepared in comparative experiment one. As can be seen from the figure, the diffraction peaks of all the prepared catalysts correspond to the (111), (200) and (220) crystal planes of Cu (PDF: 04-0836). In addition, the crystallinity of the MOF-derived CuAl/N-C catalyst becomes smaller with the change of CuAl feeding of the sample, which shows that the crystallinity of Cu nano particles is changed with the addition of aluminum, and the introduction of Al is proved to change the crystal structure of Cu. In addition, since the doping amount of aluminum is small, no diffraction peak related to aluminum is observed in the pattern.
An application of a MOF-derived CuAl/N-C catalyst, namely a working electrode prepared by taking the MOF-derived CuAl/N-C catalyst prepared in the first to third examples and the MOF-derived Cu/N-C catalyst prepared in the first comparative experiment as cathode catalysts for electrocatalytic reduction of CO2；
The specific preparation method of the working electrode is as follows:
suspending 10mg of MOF-derived CuAl/N-C catalyst in 1250 muL of ethanol, then adding 40 muL of Nafion solution with the mass percent of 5%, ultrasonically oscillating for 30min to obtain uniform ink-shaped mixed solution, uniformly spraying the uniform ink-shaped mixed solution on the surface of carbon paper by using a spray gun, and drying at the temperature of 80 ℃ to obtain a gas diffusion working electrode;
the area of the carbon paper is 2.5cm multiplied by 2.5 cm.
The electrocatalytic reduction of CO2System C of2H4The specific process is as follows:
1. assembling: a three-electrode system of a gas diffusion electrolytic cell is adopted, wherein a nickel net is used as a counter electrode and is placed in an anode chamber, an Hg/HgO reference electrode is used as a reference electrode and is placed in a cathode liquid chamber, a cathode chamber and an anode chamber are separated by a proton exchange membrane, and a gas area and a liquid area of a cathode are separated by a gas diffusion electrode. In the experiment, the pools of the cathode and the anode are filled with 80mL of KOH (99.9%) electrolyte with the concentration of 1 mol/L; the test voltage is converted into a Reversible Hydrogen Electrode (RHE), and the conversion formula is as follows: e (vs rhe) ═ E (vs Hg/HgO) +0.098V +0.059 × pH; an aqueous KOH solution (pH 14) having a concentration of 1mol/L was used as an electrolyte, and the liquid was flowed through the cathode and anode chambers using a peristaltic pump at a rate of 20 mL/min. Sealing the gas diffusion device by adopting a sealing element, and sealing the contact positions of the working electrode and the reference electrode with the sealing element to obtain the electro-catalytic reduction CO2A device;
2. electrocatalytic reduction: CO injection via digital gas flow controller2The gas passes through the gas chamber and passes through the cathode gas chamber with the gas flow rate of 10mL/min to 30 mL/min. CO is carried out at different current densities2And (3) carrying out electrocatalysis reduction, directly flowing into a gas sampling ring of the gas chromatography through a cathode region gas outlet to carry out online gas product analysis, and carrying out the analysis once every 10 minutes.
FIG. 7 is a current density plot, 1 for the MOF-derived Cu/N-C catalyst prepared in comparative experiment one and 2 for the MOF-derived CuAl/N-C catalyst prepared in example two; as can be seen, the high current density of the MOF-derived CuAl/N-C catalyst prepared in example two, as compared to the MOF-derived Cu/N-C catalyst prepared in comparative experiment one, indicates that it is useful for the electrocatalytic reduction of CO2The activity of (3) is higher.
FIG. 8 is an MOF-derived Cu/N-C catalyst electrocatalytic reduction of CO prepared in comparative experiment one2Faraday efficiency-Current Density plot for each product, 1 is H22 is CO and 3 is CH4And 4 is C2H4(ii) a FIG. 9 is an MOF-derived CuAl/N-C catalyst electrocatalytic reduction of CO prepared in example one2Faraday efficiency-Current Density plot for each product, 1 is H22 is CO and 3 is CH4And 4 is C2H4(ii) a FIG. 10 is an MOF-derived CuAl/N-C catalyst electrocatalytic reduction of CO prepared in example two2Faraday efficiency-Current Density plot for each product, 1 is H22 is CO and 3 is CH4And 4 is C2H4(ii) a FIG. 11 is an MOF-derived CuAl/N-C catalyst electrocatalytic reduction of CO prepared in EXAMPLE III2Faraday efficiency-Current Density plot for each product, 1 is H22 is CO and 3 is CH4And 4 is C2H4(ii) a As can be seen from the figure, the MOF-derived Cu/N-C catalyst electrocatalytically reduces CO2Gas phase products CO, CH are obtained4And C2H4The distribution of (A) is relatively uniform, which indicates that the MOF-derived Cu/N-C catalyst has no obvious selectivity, but the electrocatalytic reduction of CO by the MOF-derived CuAl/N-C catalyst2When compared to MOF-derived Cu/N-C catalysts, CH is produced4The efficiency of (a) is significantly reduced,CuAl/N-C of different CuAl ratios for CO and C2H4The selectivity of (a) is different.
FIG. 12 shows electrocatalytic reduction of CO2System C of2H4Faraday efficiency vs. current density plot, 1 for the MOF-derived CuAl/N-C catalyst prepared in example one, 2 for the MOF-derived CuAl/N-C catalyst prepared in example two, 3 for the MOF-derived CuAl/N-C catalyst prepared in example three, and 4 for the MOF-derived Cu/N-C catalyst prepared in comparative experiment one; as can be seen, the MOF-derived CuAl/N-C catalyst pair C prepared in example two was used as a reference for the MOF-derived Cu/N-C catalyst prepared in comparative experiment one2H4The selectivity is the highest, and the current density at the working electrode is 150mA/cm2Lower, C2H4The Faraday efficiency can reach 50%, which indicates that the compound is C2H4The best selectivity is.
- 上一篇：一种医用注射器针头装配设备
- 下一篇：一种旋转式铝制管道回收电解装置