CN112853379A

CN112853379A - Preparation method and application of supported metal monatomic catalyst

Info

Publication number: CN112853379A
Application number: CN202110177916.4A
Authority: CN
Inventors: 朱英; 王兴谱
Original assignee: Beihang University
Current assignee: Beihang University
Priority date: 2021-02-08
Filing date: 2021-02-08
Publication date: 2021-05-28
Anticipated expiration: 2041-02-08
Also published as: CN112853379B

Abstract

The invention relates to a preparation method and application of a supported metal monatomic catalyst. The catalyst takes nitrogen-doped carbon as a framework, and metal single atoms are anchored on the framework; the mass percentage of the metal single atom in the catalyst is 0.1 wt% -36 wt%. The method comprises the following steps: 1) ball milling nitrogenous organic matter, metal salt and template salt; 2) heating the powder obtained by ball milling, and cooling to obtain MN_xSA/NC catalyst, where M is the metal element of the metal salt in step 1), 2. ltoreq. x.ltoreq.5, SA denotes the abbreviation for a single atom and NC denotes nitrogen-doped carbon. The prepared catalyst is applied to electrocatalysis of carbon dioxide. The invention reduces the problem of environmental pollution and cost, and effectively adjustsThe pore structure of the catalyst is controlled, and MN is controlled in a targeted manner_xThe method is simple, and the monoatomic, diatomic and polyatomic catalysts with different loads and metals can be prepared on a large scale.

Description

Preparation method and application of supported metal monatomic catalyst

Technical Field

The invention belongs to the field of catalysts, and particularly relates to a preparation method and application of a supported metal monatomic catalyst.

Background

With the development of society, energy shortage and environmental pollution are now the problems of human production and life and social development. Therefore, the development of highly efficient catalyst materials for energy and substance conversion is imminent. Transition metal nanoparticles are widely used due to their superior catalytic properties, such as transition metals like Fe, Co, Ni, Mn, Cu, Mo, Ru, Rh, Pd, Ag, Ir, Pt, and Au. However, the high cost of metals has severely hampered their widespread use in energy and material conversion technologies. Therefore, the search for a catalyst material which is cheap and easy to prepare on a large scale has become one of the hot spots in the field of energy and substance conversion.

At present, atomically dispersed monatomic metal catalysts have attracted increasing attention. Due to the maximized atom utilization rate, the monatomic catalyst shows excellent catalytic performance in the aspects of oxidation, reduction, water gas shift, electrocatalysis and the like. However, due to the high surface energy, mobility, and easy agglomeration of the monoatomic atoms, it is a significant challenge to maintain the stability of the monoatomic catalyst during the catalytic reaction. Nitrogen-anchoring of transition metal monoatomic atoms (MN) using nitrogen-doped carbon materials_xSA/NC) which effectively improves the performance of the active site on the catalytic reaction. Conventional MN_xthe-SA/NC preparation methods mainly include pyrolysis methods, wet chemical synthesis, physical and chemical vapor deposition, electrochemical deposition, and the like, and research on the preparation of monatomic catalysts has been greatly advanced. However, the MN_xThe low load of single atoms in the SA/NC catalyst results in low current density, which affects the practical application. Increasing the loading inevitably faces migration and agglomeration of the metal atoms, resulting in a decline in the catalytic performance. Furthermore, MN_xThe coordination number of the metal atom and nitrogen of the SA/NC catalyst determines the performance of the catalyst, but the coordination number of the metal atom and nitrogen is difficult to control. In addition, MN_xThe preparation method of the SA/NC catalyst is complex in process and faces the problem of difficult large-scale preparation. Therefore, the MN with high load and controllable coordination number of metal monoatomic atoms and nitrogen is developed_xThe scale production method of the-SA/NC catalyst is realizedThe key point of use.

The high-energy ball milling method is an effective dispersion method, firstly, the method does not need the participation of a solvent, and the content of a product is accurately controlled by the material ratio, thereby not only avoiding the waste of raw materials, but also reducing the environmental pollution. Meanwhile, mechanical energy can be used for inducing chemical solid-phase reaction in the ball milling process, so that the structure and the performance of the material are changed. Importantly, the solid-phase ball milling method is simple to operate, the composition is easy to control, and large-scale mass production is easy to realize. The spinel lithium manganate material is prepared by high-energy ball milling in the Chinese patent with the application number of 201510470335.4. It utilizes MnSO₄Preparation of MnCO for the base solution₃Then adding MnCO₃The method comprises the steps of roasting to form manganese oxide, adding hydrogen peroxide to obtain a precursor, and performing ball milling and calcination to obtain the spinel lithium manganate. Chinese patent No. 201610476098.7 reports a method for preparing CuI nanopowder by one-pot ball milling solid phase method, in which a mixed raw material consisting of cupric salt, iodide and sodium sulfite is mechanically ball milled at room temperature to initiate solid phase reaction, and CuI nanopowder is prepared by one-pot method. Chinese patent with application number CN201811528753.4 discloses a boron-doped mesoporous carbon catalyst prepared by a ball milling method, a preparation method and application thereof, wherein tannic acid, a block copolymer, a boron-containing compound and a nitrogen-containing compound are put into a ball milling tank together for ball milling to obtain a solid viscous product; and (3) washing the obtained solid viscous product by using a washing liquid, dispersing the solid viscous product in the washing liquid, performing suction filtration, drying a filter cake, and roasting to obtain the boron-doped mesoporous carbon catalyst. The boron-doped mesoporous carbon catalyst can effectively overcome the defects of Pd-Hg and PtHg₄Synthesis of H for catalyst₂O₂Large energy consumption, complex process, high cost, impossible large-scale production and the like. However, no report has been made to date on the preparation of high-loading, controlled metal and nitrogen coordination number monatomic catalysts.

Disclosure of Invention

The invention aims to provide supported gold aiming at the defects in the existing preparation of monatomic catalystBelongs to a preparation method and application of a monatomic catalyst. In the catalyst, the metal atom has high load, the coordination number of the metal and nitrogen is controllable, and the metal single atom is anchored on a nitrogen-doped carbon-based Material (MN)_x-SA/NC), wherein M is a metal element selected from one, two or more of Fe, Co, Ni, Mn, Cu, Mo, Ru, Rh, Pd, Ag, Ir, Pt and Au, x is the coordination number of the metal to N (2. ltoreq. x.ltoreq.5), SA is an abbreviation for a single atom, and NC is nitrogen-doped carbon.

The purpose of the invention is realized by the following technical scheme:

a supported metal monatomic catalyst having a nitrogen-doped carbon skeleton with metal monatomics anchored to the skeleton; the mass percentage of metal single atoms in the catalyst is 0.1-36 wt% based on the total mass of the catalyst; preferably, the content of the metal single atom by mass is 4.6-34.2 wt%; preferably, the content of the metal single atom by mass is 6.4 wt% -33.2 wt%; preferably, the content of the metal single atom by mass is 16.5 wt% to 21.2 wt%.

Further, the metal is selected from one, two or more of Fe, Co, Ni, Mn, Cu, Mo, Ru, Rh, Pd, Ag, Ir, Pt and Au.

A process for preparing a catalyst as described above, characterized in that it comprises the following steps:

1) loading nitrogen-containing organic matters, metal salt and template salt into a ball milling tank, and carrying out ball milling for 30 min-10 h at the rotating speed of 100-500 r/min; wherein, the metal element in the metal salt is selected from one, two or more of Fe, Co, Ni, Mn, Cu, Mo, Ru, Rh, Pd, Ag, Ir, Pt and Au;

2) heating the powder obtained by ball milling in a tube furnace, wherein the heating rate is 1-5 ℃/min, the heating is carried out to 500-1000 ℃, the heat preservation time is 30-300 min, and the protective gas is N₂Or Ar gas, and finally cooling to obtain MN_xSA/NC catalyst, where M is the metal element of the metal salt in step 1), 2. ltoreq. x.ltoreq.5, SA denotes the abbreviation for a single atom and NC denotes nitrogen-doped carbon.

Further, in step 1), the nitrogen-containing organic matter is selected from one or more of urea, melamine, dicyandiamide, polyaniline and polypyrrole.

Further, in step 1), the template salt is selected from one or more of NaCl, KCl and LiCl.

Further, the adding amount of the nitrogen-containing organic matter, the metal salt and the template salt in the step 1) is calculated by weight parts: 5-50 parts of nitrogen-containing organic matter, 1-5 parts of metal salt and 45-90 parts of template salt.

Use of a catalyst as described in any of the above or a catalyst prepared by a method as described in any of the above in electrocatalytic carbon dioxide.

The invention has the following advantages:

1) the high-energy ball milling adopted by the project obtains and prepares MN_xThe precursor powder of SA/NC avoids the loss of metal ions due to no participation of solvent, reduces the problem of environmental pollution caused by the metal ions, also reduces the cost of the catalyst, and controls MN targetedly_xX in (1). 2) Using different salts as templates effectively regulates and controls MN_xThe pore structure of SA/NC, and this salt template is recyclable. 3) MN (Mobile node)_xThe precursor powder material of the-SA/NC is obtained by high-energy ball milling, the method is simple, the cost is low, and the large-scale preparation can be realized. 4) MN (Mobile node)_xM in the catalyst can be effectively controlled by the added metal, and the catalyst with different loading capacity and different metals, namely monoatomic, diatomic and polyatomic catalysts, can be prepared.

Drawings

FIG. 1 shows a CuN of the present invention₂-transmission electron and spherical aberration electron micrographs of SA/NC;

FIG. 2 shows a CuN of the present invention₂-map of synchrotron radiation sum electrocatalytic carbon dioxide reduction performance of SA/NC.

Detailed Description

The technical solution of the present invention will be further described with reference to the following examples.

The invention provides a method for preparing a high-capacity metal-nitrogen coordination number-controllable metal monatomic anchored nitrogen-doped carbon-based Material (MN)_xPreparation method and application of catalyst of-SA/NC)。

MN of the present invention_xSA/NC, where M is a single metal, a double metal or a multiple metal, x is the coordination number of the metal to N (2. ltoreq. x.ltoreq.5), SA is the abbreviation for monoatomic, NC is nitrogen-doped carbon, and the raw materials comprise, in parts by weight:

5-50 parts of nitrogen-containing organic matter, 1-5 parts of metal salt and 45-90 parts of template salt.

MN in accordance with the present invention_xSA/NC, wherein said nitrogenous inorganic substance can be, but is not limited to, urea, melamine, dicyandiamide, polyaniline, polypyrrole.

MN in accordance with the present invention_xSA/NC, wherein the metal element in the metal salt can be, but is not limited to, Fe, Co, Ni, Mn, Cu, Mo, Ru, Rh, Pd, Ag, Ir, Pt, and Au, and mixtures of 2 or more of the above salts can also be used to prepare monatomic, diatomic, and polyatomic catalysts for practical applications.

MN in accordance with the present invention_xSA/NC, where the template salts can be, but are not limited to, NaCl, KCl and LiCl, or mixtures of 2 or more of the above salts can be used in practice.

The invention also includes any of the above-mentioned MNs_x-a method for the preparation of SA/NC comprising the steps of:

1) nitrogen-containing inorganic substances, metal salts and template salts. Putting the mixture into a ball milling tank according to the parts by weight, and ball milling for 30min to 10h at the rotating speed of 100 to 500 r/min;

2) heating the powder obtained by ball milling in a tube furnace, wherein the heating speed is 1-5 ℃/min, the heating temperature range is 500-900 ℃, the heat preservation time is 30-300 min, and the protective gas can be but is not limited to N₂Or Ar gas, and finally cooling to obtain MN_x-SA/NC catalyst.

The invention also provides any MN_xUse of SA/NC in electrocatalytic carbon dioxide.

The invention is described in detail below with reference to the figures and the embodiments. The following examples are only for explaining the present invention, the scope of the present invention shall include the full contents of the claims, and the full contents of the claims of the present invention can be fully realized by those skilled in the art through the following examples.

Example 1:

CuN₂-a method for the preparation of SA/NC comprising the steps of:

1) 5% by weight of Cu (NO)₃)₂Ball-milling 25% dicyandiamide and 70% KCl by using a high-energy ball mill, wherein the mass ratio of ball materials is 25:1, the ball-milling speed is 350r/min, and ball-milling is carried out for 4 hours to obtain uniform powder.

2) Placing the powder obtained in the step 1) in a temperature-programmed tubular furnace, heating to 600 ℃ at a heating rate of 5 ℃/min under the nitrogen atmosphere, preserving heat for 1 hour, and naturally cooling to room temperature to obtain CuN₂-SA/NC nanomaterials; the CuN₂the-SA/NC nanomaterial is a three-dimensional network with a loading of Cu of 33.2 wt%.

Example 2:

FeN₃-a method for the preparation of SA/NC comprising the steps of:

1) 3% by weight of Fe (NO)₃)₃And carrying out ball milling on 27% of melamine and 70% of NaCl by using a high-energy ball mill, wherein the mass ratio of ball materials is 25:1, the ball milling speed is 350r/min, and the ball milling is carried out for 4 hours to obtain uniform powder.

2) Placing the powder obtained in the step 1) in a temperature-programmed tubular furnace, heating to 650 ℃ at a heating rate of 5 ℃/min in a nitrogen atmosphere, preserving heat for 1 hour, and naturally cooling to room temperature to obtain FeN₃-SA/NC nanomaterials; the FeN₃the-SA/NC nanomaterial is a three-dimensional network with a Fe loading of 21.2 wt%.

Example 3:

NiN₄-a method for the preparation of SA/NC comprising the steps of:

1) 1% by weight of Ni (NO)₃)₂And ball milling the mixture of 29 percent dicyandiamide and 35 percent KCl and 35 percent LiCl by using a high-energy ball mill, wherein the mass ratio of ball materials is 25:1, the ball milling speed is 350r/min, and the ball milling is carried out for 4 hours to obtain uniform powder.

2) Placing the powder obtained in the step 1) in a program temperature control modeIn a tubular furnace, in the nitrogen atmosphere, the heating rate is 3 ℃/min, the temperature is increased to 800 ℃, the temperature is kept for 1 hour, and the NiN is obtained after natural cooling to the room temperature₄-SA/NC nanomaterials; the NiN₄the-SA/NC nanomaterial is a three-dimensional network with a loading of Ni of 6.4 wt%.

Example 4:

CoN₅-a method for the preparation of SA/NC comprising the steps of:

1) 1% by weight of Co (NO)₃)₂14.5 percent of dicyandiamide, 14.5 percent of melamine and 70 percent of KCl are ball-milled by a high-energy ball mill, the mass ratio of ball materials is 25:1, the ball-milling speed is 450r/min, and the ball-milling is carried out for 5 hours, so as to obtain uniform powder.

2) Placing the powder obtained in the step 1) in a temperature-programmed tubular furnace, heating to 900 ℃ at a heating rate of 2 ℃/min under a nitrogen atmosphere, preserving heat for 1 hour, and naturally cooling to room temperature to obtain CoN₅-SA/NC nanomaterials; the CoN₅the-SA/NC nanomaterial is a three-dimensional network with a Co loading of 4.6 wt%.

Example 5:

AgN₄-a method for the preparation of SA/NC comprising the steps of:

1) 2% by weight of AgNO₃And carrying out ball milling on 14% dicyandiamide, 14% urea, 35% KCl and 35% NaCl by using a high-energy ball mill, wherein the mass ratio of ball materials is 25:1, the ball milling speed is 300r/min, and the ball milling is carried out for 4 hours to obtain uniform powder.

2) Placing the powder obtained in the step 1) in a temperature-programmed tubular furnace, heating to 700 ℃ at a heating rate of 4 ℃/min under an argon atmosphere, preserving heat for 1 hour, and naturally cooling to room temperature to obtain AgN₄-SA/NC nanomaterials; the AgN₄the-SA/NC nanomaterial is a three-dimensional network structure with a Ag loading of 16.5 wt%.

Example 6:

PtN₄-a method for the preparation of SA/NC comprising the steps of:

1) 4% by weight of K₂PtCl₆13% dicyandiamide + 13% urea and 20% KCl + 50% NaCl high-energy ballBall milling is carried out by a mill, the mass ratio of ball materials is 25:1, the ball milling speed is 350r/min, and ball milling is carried out for 4 hours, so as to obtain uniform powder.

2) Placing the powder obtained in the step 1) in a temperature-programmed tubular furnace, heating to 500 ℃ at a heating rate of 5 ℃/min in a nitrogen atmosphere, preserving heat for 5 hours, and naturally cooling to room temperature to obtain PtN₄-SA/NC nanomaterials; the PtN₄the-SA/NC nanomaterial is a three-dimensional network with a Pt loading of 34.2 wt%.

Example 7:

RuN₃-a method for the preparation of SA/NC comprising the steps of:

1) RuCl 3% by weight₃And carrying out ball milling on 13.5% of melamine, 13.5% of urea, 20% of KCl, 20% of NaCl and 30% of LiCl by using a high-energy ball mill, wherein the mass ratio of ball materials is 25:1, the ball milling speed is 350r/min, and the ball milling is carried out for 4 hours to obtain uniform powder.

2) Placing the powder obtained in the step 1) in a temperature-programmed tubular furnace, heating to 700 ℃ at a heating rate of 5 ℃/min under an argon atmosphere, preserving heat for 3 hours, and naturally cooling to room temperature to obtain RuN₃-SA/NC nanomaterials; the RuN₃the-SA/NC nanomaterial is a three-dimensional network structure with a Ru loading of 34.2 wt%.

Example 8:

CuN₂use of SA/NC catalysts for electrocatalytic carbon dioxide reduction to C1 product

The CuN prepared in example 1₂SA/NC catalyst at 0.5M KHCO₃The method comprises the following steps of (1) carrying out electrocatalysis on carbon dioxide to be reduced into a C1 product, and testing the types of the generated products and the corresponding Faraday efficiency, wherein the testing method comprises the following steps:

the Faraday efficiency testing device is a CHI-760E electrochemical workstation of Shanghai Chenghua apparatus, Inc., and the testing conditions are as follows: h-type electrochemical reactor under three-electrode system, CO₂The volume of the reaction cavity is 35mL, 0.5M KHCO₃As an electrolyte, 1atm CO₂Room temperature, CO₂The flow rate was 20cc/min, and the electrode area was 1cm²The catalyst loading on the electrode was 5mg/cm²At-0.76 vsChronoamperometric tests were performed at RHE. CO 2₂The reduced product was analyzed by gas chromatography using GC-2014 from SHIMADZU, Japan, and by NMR using AV-400 from Bruker, Germany. The test results are shown in b) of fig. 2. The CuN₂SA/NC at 0.5M KHCO₃The selectivity of the medium electrocatalytic carbon dioxide reduction to the C1 product is higher than 90%, and the medium electrocatalytic carbon dioxide has good stability and can be commercially applied.

FIG. 1 a) shows CuN₂Transmission Electron microscopy of SA/NC Material (JEOL Equipment, type JEM-2100F, voltage 200kV used in the test), b) shows CuN₂Spherical aberration electron microscopy of SA/NC material (JEOL equipment, model ARM200F, voltage used for the test 200 kV). In FIG. 2, a) is a graph showing the pair of CuN₂-extended edge X-ray fine structure spectrogram of Cu K-edge in SA/NC material (8.0 beam line source from Lawrence Berkeley National Lab, data fitting using Athena software) obtained in R space after fourier transformation 3 times in K space, wherein the abscissa has a weighting function and fitting function thereof

Information of the coordinate atoms in different positions in R space, ordinate

And the intensities corresponding to coordination atoms at different positions of a weighting function obtained in an R space after Fourier transform is carried out on an extended edge X-ray fine structure spectrogram of a Cu K-edge for 3 times in a K space. B) in FIG. 2 shows CuN₂Application of SA/NC materials to electrocatalytic CO₂The kind of product formed after reduction and the corresponding Faraday efficiency, the abscissa of the graph refers to electrocatalytic CO₂The kind of the product obtained during reduction, and the ordinate indicates the faradaic efficiency corresponding to the obtained product.

It should be noted that, according to the above embodiments of the present invention, those skilled in the art can fully implement the full scope of the present invention as defined by the independent claims and the dependent claims, and implement the processes and methods as the above embodiments; and the invention has not been described in detail so as not to obscure the present invention.

The above description is only a part of the embodiments of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.

Claims

1. A supported metal monatomic catalyst, characterized in that the catalyst has nitrogen-doped carbon as a framework, and a metal monatomic is anchored to the framework; the mass percentage of metal single atoms in the catalyst is 0.1-36 wt% based on the total mass of the catalyst; preferably, the content of the metal single atom by mass is 4.6-34.2 wt%; preferably, the content of the metal single atom by mass is 6.4 wt% -33.2 wt%; preferably, the content of the metal single atom by mass is 16.5 wt% to 21.2 wt%.

2. The catalyst of claim 1 wherein the metal is selected from one, two or more of Fe, Co, Ni, Mn, Cu, Mo, Ru, Rh, Pd, Ag, Ir, Pt and Au.

3. A method of preparing the catalyst of claim 1, comprising the steps of:

2) heating the powder obtained by ball milling in a tube furnace, wherein the heating rate is 1-5 ℃/min, the heating is carried out to 500-1000 ℃, the heat preservation time is 30-300 min, and the protective gas is N₂Or Ar gas, and finally cooling to obtain MN_xSA/NC catalyst, in which M is in the metal salt of stage 1)2 is less than or equal to x is less than or equal to 5, SA is the abbreviation of single atom, and NC represents nitrogen-doped carbon.

4. The method according to claim 3, wherein in step 1), the nitrogen-containing organic compound is selected from one or more of urea, melamine, dicyandiamide, polyaniline and polypyrrole.

5. The method according to claim 3, wherein in step 1), the template salt is selected from one or more of NaCl, KCl and LiCl.

6. The method according to claim 3, wherein the nitrogen-containing organic substance, the metal salt and the template salt are added in the step 1) in the following amounts by weight: 5-50 parts of nitrogen-containing organic matter, 1-5 parts of metal salt and 45-90 parts of template salt.

7. Use of the catalyst of any one of claims 1-2 or prepared by the process of any one of claims 3-6 for electrocatalytic carbon dioxide.