Supported metal atom catalyst as well as preparation method and application thereof

Abstract

The invention provides a supported metal atom catalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: preparing nitrogen-doped nano-porous graphene; a first metal monatomic catalyst is prepared using underpotential deposition and galvanic replacement. Pyridine nitrogen defect sites on the surface of nitrogen-doped nano-porous graphene are used as sites for underpotential deposition of metal monatomic, and the metal monatomic catalyst is obtained through first-step underpotential deposition. Furthermore, a first metal and second metal double-atom catalyst can be prepared by adopting underpotential deposition and electric replacement, namely, the metal monatomic in the first step can be used as a site of underpotential deposition in the second step to further prepare the metal monatomic, and a metal double-atom structure is formed. The strong interaction between metal and a carrier and the difference of electronic structures between metal and metal are utilized to regulate and control the electronic structures of metal atoms with catalytic activity, so that the metal atoms show different catalytic activities in different electrolytes.

Description

Technical Field

[0001] The present invention relates to the field of catalytic technology, and in particular to a supported metal atom catalyst and a preparation method and application thereof. Background Art

[0002] There is a growing interest in hydrogen as a clean chemical energy source to replace fossil fuels and avoid carbon dioxide emissions. The electrocatalyst hydrogen evolution reaction (HER) based on renewable energy is a promising, safe, scalable and low-cost green hydrogen production method. The precious metal platinum is considered to be the most effective catalyst in HER. However, due to its high cost, further consideration is needed on how to maximize the utilization efficiency of precious metals and improve the activity of catalysts by adjusting their electronic structure.

[0003] Single-atom catalysts can minimize catalytic structures with clear active sites, and their uniform atomic coordination environment makes them an ideal simplified model system for studying the mechanism of catalytic reactions. Supported nanocatalysts are fixed on carriers, and the electronic structure of the catalyst active sites can be effectively regulated by strong metal-carrier electronic interactions. Strong electronic interactions can not only stabilize single atoms by forming thermodynamically favorable metal-carrier bonds, but also regulate the electronic structure of single atoms through electron transfer. However, the regulation results only through metal-carrier electronic interactions are relatively simple, and the existing methods for synthesizing single atoms are often complicated and often require the introduction of high temperature, high pressure and other conditions, which is a great waste of energy.

[0004] Therefore, developing a highly active metal atom catalyst with a simple preparation method, mild preparation conditions, reduced use of precious metals, and adjustable performance is a technical problem that needs to be urgently solved by those skilled in the art. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for preparing a supported metal atom catalyst, comprising the following steps:

[0006] Step 1, preparing nitrogen-doped nanoporous graphene: first growing nitrogen-doped graphene on the surface of a nanoporous nickel template by chemical vapor deposition, and then corroding the nanoporous nickel template on which the nitrogen-doped graphene is grown to obtain self-supporting nitrogen-doped nanoporous graphene;

[0007] Step 2, preparing the first metal single atom by underpotential deposition and electrical replacement: first, depositing the metal single atom to be replaced on the surface of the nitrogen-doped nanoporous graphene by underpotential deposition to obtain the nitrogen-doped nanoporous graphene loaded with the metal single atom to be replaced; then placing the nitrogen-doped nanoporous graphene loaded with the metal single atom to be replaced in a first metal precursor solution, standing at an open circuit voltage, replacing the metal single atom to be replaced loaded on the nitrogen-doped nanoporous graphene with the first metal single atom, and obtaining the first metal single atom catalyst loaded on the nitrogen-doped nanoporous graphene;

[0008] Preferably, the method for preparing the supported metal atom catalyst further comprises:

[0009] Step three, prepare the first metal and the second metal diatoms by underpotential deposition and electrical replacement: first, underpotentially deposit the metal single atom to be replaced on the nitrogen-doped nanoporous graphene loaded with the first metal single atom to obtain the nitrogen-doped nanoporous graphene loaded with the first metal and the metal diatoms to be replaced; then, place the nitrogen-doped nanoporous graphene loaded with the first metal and the metal diatoms to be replaced in a second metal precursor solution, let it stand at an open circuit voltage, replace the metal single atom to be replaced loaded on the nitrogen-doped nanoporous graphene with the second metal single atom, and obtain the first metal and the second metal diatomic catalyst loaded on the nitrogen-doped nanoporous graphene.

[0010] Preferably, the method for preparing the nanoporous nickel template comprises:

[0011] The nickel-based alloy sheet is immersed in a weak acid solution formed by a strong acid and a weak base salt, and other metal elements except nickel in the nickel-based alloy sheet are removed to obtain a nanoporous nickel template.

[0012] Preferably, the nickel-based alloy sheet is Ni 30 Mn 70 , the strong acid and weak base salt is ammonium sulfate.

[0013] Preferably, the step of growing nitrogen-doped graphene on the nanoporous nickel template by chemical vapor deposition in step 1 comprises:

[0014] The nanoporous nickel template is placed in a heating treatment device, and nitrogen-doped graphene is grown on the nanoporous nickel template by vapor deposition using a carbon source and a carbon source.

[0015] Preferably, the nitrogen source and carbon source are melamine, and the area (cm 2 ) and the melamine dosage (mg) are in a ratio of 1:10 to 1:100, the protective gas in the heating treatment equipment is 20 to 200 sccm argon and 20 to 200 sccm hydrogen, and the growth temperature of the nitrogen-doped graphene is 700°C to 1000°C.

[0016] Preferably, the step of corroding the nanoporous nickel template on the surface of which the nitrogen-doped graphene is grown to obtain self-supporting nitrogen-doped nanoporous graphene comprises:

[0017] The nanoporous nickel template with nitrogen-doped graphene grown on the surface is immersed in a HCl solution containing FeCl3 to corrode the nanoporous nickel and obtain self-supporting nitrogen-doped nanoporous graphene.

[0018] Preferably, the step 2 of depositing the metal single atom to be replaced on the surface of the nitrogen-doped nanoporous graphene at an underpotential to obtain the nitrogen-doped nanoporous graphene loaded with the metal single atom to be replaced comprises:

[0019] A metal precursor solution to be replaced is added, a platinum sheet is used as a counter electrode, a silver / silver chloride electrode is used as a reference electrode, and the nitrogen-doped nanoporous graphene is used as a working electrode. Single-atom underpotential deposition of the metal to be replaced is performed on the surface of the nitrogen-doped nanoporous graphene to obtain nitrogen-doped nanoporous graphene loaded with single-atom metal to be replaced;

[0020] The step 3 of underpotentially depositing a metal single atom to be replaced on the nitrogen-doped nanoporous graphene loaded with a first metal single atom to obtain nitrogen-doped nanoporous graphene loaded with a first metal and a metal double atom to be replaced comprises:

[0021] A metal precursor solution to be replaced is added, a platinum sheet is used as a counter electrode, a silver / silver chloride electrode is used as a reference electrode, and a nitrogen-doped nanoporous graphene loaded with a first metal single atom is used as a working electrode. The first metal single atom underpotential deposition is performed on the surface of the nitrogen-doped nanoporous graphene loaded with a first metal single atom to obtain nitrogen-doped nanoporous graphene loaded with diatomic amounts of the first metal and the metal to be replaced.

[0022] Preferably, the metal to be replaced is lead, iron, cobalt, nickel or copper, and correspondingly, the metal precursor solution to be replaced is a nitric acid solution of lead nitrate, a sulfuric acid solution of ferrous sulfate, a sulfuric acid solution of cobalt sulfate, a sulfuric acid solution of nickel sulfate or a sulfuric acid solution of copper sulfate.

[0023] Preferably, in the copper sulfate sulfuric acid solution, the sulfuric acid solution is 0.1 mol / L to 0.5 mol / L, and the concentration of the added copper sulfate is 2 mmol / L to 20 mmol / L; the underpotential deposition voltage is 0 V to 0.3 V relative to the silver / silver chloride electrode, and the deposition time is 30 s to 600 s.

[0024] Preferably, in step 2, the first metal precursor solution is a sulfuric acid solution containing chloroauric acid or potassium chloroplatinate, and correspondingly, the first metal is gold or platinum.

[0025] Preferably, in the sulfuric acid solution containing chloroauric acid, the sulfuric acid solution is 5mmol / L to 50mmol / L, the concentration of chloroauric acid is 1mmol / L to 10mmol / L; and the standing time at open circuit voltage in step 2 is 1min to 30min.

[0026] Preferably, in step three, the second metal precursor solution is a sulfuric acid solution containing potassium tetrachloropalladate, ruthenium chloride, rhodium chloride or potassium tetrachloroplatinate, and correspondingly, the second metal is palladium, ruthenium, rhodium or platinum.

[0027] Preferably, in the sulfuric acid solution containing potassium tetrachloroplatinate, the sulfuric acid solution is 5mmol / L to 50mmol / L, the concentration of potassium tetrachloroplatinate is 1mmol / L to 10mmol / L, and the standing time at open circuit voltage in step 3 is 1min to 30min.

[0028] The present invention also provides a supported metal atom catalyst prepared according to the above method, comprising a gold-platinum diatomic catalyst supported on nitrogen-doped nanoporous graphene.

[0029] The present invention also provides a supported metal atom catalyst, which is used as a water electrolysis catalyst. Compared with the prior art, the technical solution of the embodiment of the present invention has the following beneficial effects:

[0030] The present invention provides a supported metal atom catalyst and a preparation method and application thereof, wherein the preparation method comprises: preparing nitrogen-doped nanoporous graphene; preparing a first metal single-atom catalyst by underpotential deposition and electroreplacement. The present invention utilizes pyridine nitrogen defect sites on nitrogen-doped nanoporous graphene as specific sites for underpotential deposition of single atoms, and prepares a variety of catalysts with single-atom structures by underpotential deposition combined with electroreplacement reaction. The present invention deposits metal single atoms at specific sites by underpotential deposition and electroreplacement to obtain a metal single-atom structure, and the preparation conditions are mild and simple. The electronic structure of the metal atom with catalytic activity is regulated by utilizing the difference in the electronic structure of the strong interaction between the metal and the carrier, so that the metal atom exhibits different catalytic activities in different electrolytes, which provides a new idea for designing catalysts for use under different conditions.

[0031] Furthermore, in the preparation method of the supported metal atom catalyst of the present invention, the metal single atom site of the first step is further used as the site of the second step underpotential deposition to further obtain a catalyst with a diatomic structure. The present invention deposits metal single atoms at specific sites by a stepwise underpotential deposition and electrical replacement method to obtain a metal diatomic structure. The preparation conditions are mild and simple. The electronic structure of the metal atom with catalytic activity is regulated by utilizing the difference in electronic structure between metals, so that the metal atom exhibits different catalytic activities in different electrolytes. This provides a new idea for designing catalysts for use under different conditions.

[0032] Furthermore, the platinum-supported single-atom catalyst, platinum-supported diatomic catalyst and gold-platinum-supported diatomic catalyst provided by the present invention exhibit excellent catalytic activity in the electrolysis of water and hydrogen evolution reaction under acidic and alkaline conditions, respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0034] Figure 1 This is a scanning electron microscope image of the np-NG sample in Example 1 of the present invention.

[0035] Figure 2 This is a scanning transmission electron microscopy image of the np-NG / PtPt diatomic catalyst in Example 3 of the present invention.

[0036] Figure 3 This is a scanning transmission electron microscopy image of the np-NG / AuPt diatomic catalyst in Example 4 of the present invention.

[0037] Figure 4 It is the XPS spectrum of the N1s peak of each sample described in Examples 1-4 of the present invention and Comparative Examples 2-3.

[0038] Figure 5 is the Cu 2p of each sample described in Examples 1-3 of the present invention and Comparative Example 1 3 / 2 XPS spectrum of peaks;

[0039] Figure 6 The XPS spectra of the Pt 4f peaks of the samples described in Examples 2-4 of the present invention;

[0040] Figure 7Polarization curves of the hydrogen evolution reaction of water electrolysis under 0.5M H2SO4 for each sample in Examples 2 and 3 of the present invention and Comparative Examples 2 and 3;

[0041] Figure 8 Polarization curves of hydrogen evolution reaction of water electrolysis under 1.0M KOH conditions for samples in Examples 2 and 4 of the present invention and Comparative Examples 2 and 3;

[0042] Fig. 9 It is a constant voltage underpotential deposition curve diagram in Example 2 of the present invention and Comparative Example 3. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0045] The present invention provides a method for preparing a supported metal atom catalyst, comprising the following steps:

[0046] Step 1, preparing nitrogen-doped nanoporous graphene: first growing nitrogen-doped graphene on the surface of a nanoporous nickel template by chemical vapor deposition, and then corroding the nanoporous nickel template on which the nitrogen-doped graphene is grown to obtain self-supporting nitrogen-doped nanoporous graphene;

[0047] Step 2: Prepare the first metal single atom by underpotential deposition and electrical replacement: first, deposit the metal single atom to be replaced on the surface of the nitrogen-doped nanoporous graphene underpotential deposition to obtain the nitrogen-doped nanoporous graphene loaded with the metal single atom to be replaced; then, place the nitrogen-doped nanoporous graphene loaded with the metal single atom to be replaced in a first metal precursor solution, let it stand at an open circuit voltage, replace the metal single atom to be replaced loaded on the nitrogen-doped nanoporous graphene with the first metal single atom, and obtain the first metal single atom loaded on the nitrogen-doped nanoporous graphene.

[0048] The present invention utilizes pyridine nitrogen defect sites on nitrogen-doped nanoporous graphene as specific sites for underpotential deposition of single atoms, and prepares a variety of catalysts with single-atom structures by underpotential deposition combined with galvanic replacement reaction. The present invention deposits metal single atoms at specific sites by underpotential deposition and galvanic replacement to obtain metal single-atom structures, and the preparation conditions are mild and simple. The electronic structure of metal atoms with catalytic activity is regulated by utilizing the difference in the electronic structure of the strong interaction between the metal and the carrier, so that the metal atoms exhibit different catalytic activities in different electrolytes, which provides a new idea for designing catalysts used under different conditions.

[0049] Furthermore, the method for preparing the supported metal atom catalyst further comprises:

[0050] Step three, prepare the first metal and the second metal diatoms by underpotential deposition and electrical replacement: first, underpotentially deposit the metal single atom to be replaced on the nitrogen-doped nanoporous graphene loaded with the first metal single atom to obtain the nitrogen-doped nanoporous graphene loaded with the first metal and the metal diatoms to be replaced; then, place the nitrogen-doped nanoporous graphene loaded with the first metal and the metal diatoms to be replaced in a second metal precursor solution, let it stand at an open circuit voltage, replace the metal single atom to be replaced loaded on the nitrogen-doped nanoporous graphene with the second metal single atom, and obtain the first metal and the second metal diatomic catalyst loaded on the nitrogen-doped nanoporous graphene.

[0051] The present invention can also use the metal single atom site in the first step as a site for the second step of underpotential deposition to further obtain a catalyst with a diatomic structure. The present invention deposits metal single atoms at specific sites by a stepwise underpotential deposition and electrical replacement method to obtain a metal diatomic structure. The preparation conditions are mild and simple. The electronic structure of metal atoms with catalytic activity is regulated by utilizing the difference in electronic structure between metals, so that the metal atoms exhibit different catalytic activities in different electrolytes. This provides a new idea for designing catalysts for use under different conditions.

[0052] The present invention does not impose any specific restrictions on the metal to be replaced, the first metal and the second metal. For example, the metal to be replaced may be lead, iron, cobalt, nickel or copper, the first metal may be gold or platinum, and the second metal may be palladium, ruthenium, rhodium or platinum.

[0053] Since the preparation method of the nanoporous nickel template belongs to the conventional technical means in the art, the present invention does not make specific restrictions on this. As an embodiment, the preparation method of the nanoporous nickel template includes:

[0054] The nickel-based alloy sheet is immersed in a weak acid solution formed by a strong acid and a weak base salt, and other metal elements except nickel in the nickel-based alloy sheet are removed to obtain a nanoporous nickel template.

[0055] Furthermore, the nickel-based alloy sheet is Ni 30 Mn 70 , the strong acid and weak base salt is ammonium sulfate.

[0056] As an embodiment, the step 1 of growing nitrogen-doped graphene on the nanoporous nickel template by chemical vapor deposition includes:

[0057] The nanoporous nickel template is placed in a heating treatment device, and nitrogen-doped graphene is grown on the nanoporous nickel template by vapor deposition using a carbon source and a carbon source.

[0058] The nitrogen source and carbon source are pyridine or melamine. Taking melamine as an example, the area (cm 2 ) and the melamine dosage (mg) are in a ratio of 1:10 to 1:100, the protective gas in the heating treatment equipment is 20 to 200 sccm argon and 20 to 200 sccm hydrogen, and the growth temperature of the nitrogen-doped graphene is 700°C to 1000°C.

[0059] As an embodiment, the step of corroding the nanoporous nickel template on the surface of which the nitrogen-doped graphene is grown to obtain self-supporting nitrogen-doped nanoporous graphene comprises:

[0060] The nanoporous nickel template with nitrogen-doped graphene grown on the surface is immersed in a HCl solution containing FeCl3 to corrode the nanoporous nickel and obtain self-supporting nitrogen-doped nanoporous graphene.

[0061] As an embodiment, the step 2 of depositing the metal single atom to be replaced on the surface of the nitrogen-doped nanoporous graphene at an underpotential to obtain the nitrogen-doped nanoporous graphene loaded with the metal single atom to be replaced includes:

[0062] A metal precursor solution to be replaced is added, a platinum sheet is used as a counter electrode, a silver / silver chloride electrode is used as a reference electrode, and the nitrogen-doped nanoporous graphene is used as a working electrode. Single-atom underpotential deposition of the metal to be replaced is performed on the surface of the nitrogen-doped nanoporous graphene to obtain nitrogen-doped nanoporous graphene loaded with single-atom metal to be replaced;

[0063] The step 3 of underpotentially depositing a metal single atom to be replaced on the nitrogen-doped nanoporous graphene loaded with a first metal single atom to obtain nitrogen-doped nanoporous graphene loaded with a first metal and a metal double atom to be replaced comprises:

[0064] A metal precursor solution to be replaced is added, a platinum sheet is used as a counter electrode, a silver / silver chloride electrode is used as a reference electrode, and a nitrogen-doped nanoporous graphene loaded with a first metal single atom is used as a working electrode. The first metal single atom underpotential deposition is performed on the surface of the nitrogen-doped nanoporous graphene loaded with a first metal single atom to obtain nitrogen-doped nanoporous graphene loaded with diatomic amounts of the first metal and the metal to be replaced.

[0065] The above-mentioned metal to be replaced can be lead, iron, cobalt, nickel or copper, and correspondingly, the metal precursor solution to be replaced is a nitric acid solution of lead nitrate, a sulfuric acid solution of ferrous sulfate, a sulfuric acid solution of cobalt sulfate, a sulfuric acid solution of nickel sulfate or a sulfuric acid solution of copper sulfate. For example: a sulfuric acid solution with copper sulfate added is configured, a platinum sheet is used as a counter electrode, a silver / silver chloride electrode is used as a reference electrode, the nitrogen-doped nanoporous graphene is used as a working electrode, and copper single atom underpotential deposition is performed on the surface of the nitrogen-doped nanoporous graphene to obtain nitrogen-doped nanoporous graphene loaded with copper single atoms; in this step, the sulfuric acid solution of copper sulfate is replaced with a nitric acid solution of lead nitrate, and lead single atom underpotential deposition is performed on the surface of the nitrogen-doped nanoporous graphene to obtain nitrogen-doped nanoporous graphene loaded with lead single atoms; in this step, sulfuric acid is added to replace the sulfuric acid solution of copper sulfate .... Copper is replaced by ferrous sulfate, and single-atom underpotential deposition of iron is performed on the surface of the nitrogen-doped nanoporous graphene to obtain nitrogen-doped nanoporous graphene loaded with single iron atoms; in this step, copper sulfate is replaced by cobalt sulfate, and single-atom underpotential deposition of cobalt is performed on the surface of the nitrogen-doped nanoporous graphene to obtain nitrogen-doped nanoporous graphene loaded with single cobalt atoms; in this step, copper sulfate is replaced by nickel sulfate, and single-atom underpotential deposition of nickel is performed on the surface of the nitrogen-doped nanoporous graphene to obtain nitrogen-doped nanoporous graphene loaded with single nickel atoms.

[0066] In step 2, the first metal precursor solution is a sulfuric acid solution containing chloroauric acid or potassium chloroplatinate, and correspondingly, the first metal is gold or platinum.

[0067] In step three, the second metal precursor solution is a sulfuric acid solution containing potassium tetrachloropalladate, ruthenium chloride, rhodium chloride or potassium tetrachloroplatinate, and correspondingly, the second metal is palladium, ruthenium, rhodium or platinum.

[0068] As an embodiment, in step 2, single gold atoms are prepared by underpotential deposition and electrical replacement, including: preparing a sulfuric acid solution with copper sulfate added, using a platinum sheet as a counter electrode, a silver / silver chloride electrode as a reference electrode, and the nitrogen-doped nanoporous graphene as a working electrode, performing underpotential deposition of single copper atoms on the surface of the nitrogen-doped nanoporous graphene to obtain nitrogen-doped nanoporous graphene loaded with single copper atoms; then placing the nitrogen-doped nanoporous graphene loaded with single copper atoms in a sulfuric acid solution containing chloroauric acid, and standing at an open circuit voltage to replace the single copper atoms loaded on the nitrogen-doped nanoporous graphene with single gold atoms, thereby obtaining single gold atoms loaded on the nitrogen-doped nanoporous graphene.

[0069] In step three, gold-platinum diatoms are prepared by underpotential deposition and electrical replacement, including: preparing a sulfuric acid solution with copper sulfate added, using a platinum sheet as a counter electrode, a silver / silver chloride electrode as a reference electrode, and nitrogen-doped nanoporous graphene supported by gold single atoms as a working electrode, and performing copper single atom underpotential deposition on the surface of the nitrogen-doped nanoporous graphene supported by the gold single atoms to obtain nitrogen-doped nanoporous graphene supported by gold-copper diatoms; and then placing the nitrogen-doped nanoporous graphene supported by the gold-copper diatoms in a sulfuric acid solution containing potassium tetrachloroplatinate, and standing at an open circuit voltage to replace the copper single atoms supported on the nitrogen-doped nanoporous graphene with platinum single atoms, thereby obtaining a gold-platinum diatomic catalyst supported on the nitrogen-doped nanoporous graphene.

[0070] Furthermore, in the copper sulfate sulfuric acid solution, the sulfuric acid solution is 0.1 mol / L to 0.5 mol / L, and the concentration of the added copper sulfate is 2 mmol / L to 20 mmol / L; the underpotential deposition voltage is 0 V to 0.3 V relative to the silver / silver chloride electrode, and the deposition time is 30 s to 600 s.

[0071] In the sulfuric acid solution containing chloroauric acid, the sulfuric acid solution is 5mmol / L to 50mmol / L, and the concentration of chloroauric acid is 1mmol / L to 10mmol / L; the standing time under open circuit voltage in step 2 is 1min to 30min.

[0072] In the sulfuric acid solution containing potassium tetrachloroplatinate, the sulfuric acid solution is 5mmol / L to 50mmol / L, the concentration of potassium tetrachloroplatinate is 1mmol / L to 10mmol / L, and the standing time at the open circuit voltage in step 3 is 1min to 30min.

[0073] In the present invention, the copper single atom-loaded nitrogen-doped nanoporous graphene described in step 2 is placed in a sulfuric acid solution containing chloroauric acid, and allowed to stand at an open circuit voltage to replace the copper single atom loaded on the nitrogen-doped nanoporous graphene with a gold single atom, thereby obtaining a gold single atom loaded on the nitrogen-doped nanoporous graphene. Wherein, chloroauric acid and potassium chloroplatinate are used to replace chloroauric acid, respectively, so that the copper single atom loaded on the nitrogen-doped nanoporous graphene can be replaced with a gold single atom and a platinum single atom, respectively.

[0074] In step 3, the nitrogen-doped nanoporous graphene loaded with gold-copper diatoms is placed in a sulfuric acid solution containing potassium tetrachloroplatinate, and allowed to stand at an open circuit voltage to replace the copper single atom loaded on the nitrogen-doped nanoporous graphene with a platinum single atom, thereby obtaining a gold-platinum diatomic catalyst loaded on the nitrogen-doped nanoporous graphene. Potassium tetrachloropalladate, ruthenium chloride, and rhodium chloride are used to replace potassium tetrachloroplatinate, respectively, so that the copper single atom loaded on the nitrogen-doped nanoporous graphene can be replaced with palladium, ruthenium, and rhodium single atoms, respectively.

[0075] In order to make the above-mentioned purposes, features and beneficial effects of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0076] Embodiment 1:

[0077] This embodiment provides a method for preparing a supported single-atom catalyst, comprising the following steps:

[0078] (1) Take an area of ​​4 cm 2 , Ni with a thickness of 150μm 30 Mn 70 Alloy sheet, use #400, #1200, #2000 sandpaper to grind the surface oxide scale of the alloy sheet, and then 30 Mn 70 The sheets were chemically dealloyed in 1.0 M (NH4)2SO4 aqueous solution at 50°C for 5 h, then rinsed thoroughly with deionized water and ethanol, and dried in a vacuum oven at room temperature to obtain a nanoporous nickel template (np-Ni).

[0079] (2) The nanoporous nickel template (np-Ni) is loaded into a quartz tube of a three-zone heating furnace, and nitrogen-doped graphene (NG) is grown on the nanoporous nickel template (np-Ni) by chemical vapor deposition.

[0080] Melamine is used as a carbon source and a nitrogen source when growing nitrogen-doped graphene (NG). The specific steps of preparing nitrogen-doped graphene (NG) on a nanoporous nickel template (np-Ni) by chemical vapor deposition process include:

[0081] About 200 mg of melamine powder and 4 cm 2 The nanoporous nickel template (np-Ni) was loaded into a porcelain boat and placed in the central heating zone and the adjacent downstream heating zone. In an atmosphere of a mixed gas of Ar (200 sccm) and H2 (200 sccm), the downstream heating zone was first heated from room temperature to 800°C within 30 minutes to anneal the nanoporous nickel. At the same time, the central heating zone was gradually heated to 200°C within 30 minutes. During the 5-minute pre-reduction annealing process, the melamine powder was further heated to 300°C. When the temperature of the central heating zone approached 300°C, the melamine powder began to evaporate and formed a continuous graphene film on the nickel substrate. The furnace was opened immediately after 7 minutes of graphene growth and cooled to room temperature with a fan to obtain nanoporous nickel (np-Ni / NG) with nitrogen-doped graphene grown on the surface.

[0082] (3) The nanoporous nickel (np-Ni / NG) was corroded with a 2.0 M HCl solution containing 5 mM FeCl 3 at 50°C for 12 h and then rinsed with deionized water five times. Figure 1 The figure shows the nitrogen-doped nanoporous graphene (np-NG) finally obtained by freeze-drying technology.

[0083] (4) Nitrogen-doped nanoporous graphene (np-NG) was mixed with 0.5% Nafion ethanol solution and subjected to ultrasonic treatment to form an ink with a concentration of 4 mg / mL. The glassy carbon electrode was polished, cleaned in ethanol for a short time with ultrasound, and then dried at room temperature. 5 μL of np-NG ink was dropped on the glassy carbon electrode and dried under an infrared lamp to make a working electrode. ) is the reference electrode, with 1×1cm 2 A platinum sheet was used as the counter electrode, and single atoms were prepared on np-NG by underpotential deposition.

[0084] (5) In a 0.1 M H2SO4 saturated Ar solution containing 2 mM CuSO4, underpotential deposition of copper atoms was performed on np-NG for 120 s by controlling the potential at +0.10 V to obtain nitrogen-doped nanoporous graphene loaded with copper single atoms (np-NG / Cu).

[0085] Embodiment 2:

[0086] This embodiment provides a method for preparing a supported single-atom catalyst. Based on Embodiment 1, this embodiment further comprises:

[0087] (6) Based on the np-NG / Cu obtained in step (5) of Example 1, the np-NG / Cu was washed with deionized water and then transferred to an Ar-saturated solution of 50 mM H2SO4 containing 5 mM H2PtCl4 and allowed to stand for 5 minutes. Copper atoms were used to replace Pt(II) to obtain three-dimensional nanoporous nitrogen-doped graphene (np-NG / Pt) loaded with platinum single atoms.

[0088] np-NG / Pt in 0.5M H2SO4 and 1.0M KOH electrolyte at 10mA / cm 2 The overpotentials at the current densities are 47mV and 182mV respectively.

[0089] Embodiment 3:

[0090] This embodiment provides a method for preparing a supported diatomic catalyst. Based on Embodiment 2, this embodiment further comprises:

[0091] (7) Based on the np-NG / Pt obtained in step (6) of Example 2, a second step of underpotential deposition of copper atoms is performed. The operation is similar to the underpotential deposition of copper atoms on np-NG, that is, in a 0.1M H2SO4 saturated Ar solution containing 2mM CuSO4, by controlling the potential at +0.10V, copper atoms are underpotentially deposited on np-NG / Pt for 120 seconds to obtain nitrogen-doped nanoporous graphene supported by platinum-copper diatoms (np-NG / PtCu). Then, after washing the np-NG / PtCu with deionized water, it is transferred to an Ar saturated solution of 50mM H2SO4 containing 5mM K2PtCl4, and allowed to stand at an open circuit voltage for 5 minutes to replace Pt(II) with copper atoms, thereby obtaining a platinum-platinum diatomic catalyst supported on nitrogen-doped nanoporous graphene (np-NG / PtPt), whose structure is as follows: Figure 2 shown.

[0092] Figure 7 Electrochemical hydrogen evolution performance of np-NG / PtPt in 0.5M H2SO4 electrolyte at a current density of 10mA / cm 2 and 100mA / cm 2 The overpotentials are 37 mV and 103 mV, respectively, which are better than 39 mV and 127 mV of commercial Pt / C.

[0093] Embodiment 4:

[0094] This embodiment provides a method for preparing a supported diatomic catalyst. Based on Embodiment 1, this embodiment further comprises:

[0095] (6) Based on the np-NG / Cu obtained in step (5) of Example 1, the np-NG / Cu was washed with deionized water and then transferred to an Ar saturated solution of 50 mM H2SO4 containing 1 mM HAuCl4, and allowed to stand at an open circuit voltage for 5 minutes to allow the copper atoms to replace Au(III) to obtain nitrogen-doped nanoporous graphene (np-NG / Au) loaded with gold single atoms.

[0096] (7) The second step of underpotential deposition of copper atoms was performed on np-NG / Au. The operation was similar to that of underpotential deposition of copper atoms on np-NG / Pt. That is, in a 0.1M H2SO4 saturated Ar solution containing 2mM CuSO4, copper atoms were underpotentially deposited on np-NG / Au for 120 seconds by controlling the potential at +0.10V to obtain nitrogen-doped nanoporous graphene (np-NG / AuCu) loaded with gold-copper diatoms. Then, after washing np-NG / AuCu with deionized water, it was transferred to a 50mM H2SO4 saturated Ar solution containing 5mM K2PtCl4 and allowed to stand at an open circuit voltage for 5 minutes to replace the copper atoms with Pt(II). Thus, a gold-platinum diatomic catalyst (np-NG / AuPt) loaded on nitrogen-doped nanoporous graphene was obtained. Its structure is shown in FIG. Figure 3 shown.

[0097] Figure 4 The nanoporous graphene is nitrogen-doped (np-NG), nitrogen-doped nanoporous graphene supported by a single copper atom (np-NG / Cu), nitrogen-doped nanoporous graphene supported by a single platinum atom (np-NG / Pt), nitrogen-doped nanoporous graphene supported by two platinum and copper atoms (np-NG / PtCu), nitrogen-doped nanoporous graphene supported by two platinum and platinum atoms (np-NG / PtPt), nitrogen-doped nanoporous graphene supported by a single gold atom (np-NG / Au), and nitrogen-doped nanoporous graphene supported by two gold and platinum atoms (np-NG / Au). From the XPS spectrum of the N1s peak in graphene (np-NG / AuPt), it can be seen that the original np-NG has the most pyridinic nitrogen sites in the low-energy direction. After the gradual growth of single atoms, the signal intensity of the pyridinic nitrogen gradually decreases, and the signal of the metal-nitrogen site in the high-energy direction gradually increases, indicating that under this condition, the pyridinic nitrogen site in np-NG is a specific site for underpotential deposition; after further generation of diatoms, the peak position further shifts to the high-energy direction, indicating a stronger metal-nitrogen interaction, indicating the formation of diatoms.

[0098] Figure 5Cu2p in Cu nanoparticles (Cu bulk), np-NG / Cu, np-NG / Pt, np-NG / PtCu and np-NG / PtPt 3 / 2 In the XPS spectra of the peaks, there is no obvious Cu signal in np-NG / Pt and np-NG / PtPt, indicating that a substitution reaction has occurred; compared with single atoms (np-NG / Cu), diatomic atoms (np-NG / PtCu) and nanoparticles (Cu bulk), the more the number of atoms is, the more the energy of Cu shifts toward the low energy direction, indicating that different methods can obtain different atomic structures.

[0099] Figure 6 The XPS graphs of the Pt 4f peak of np-NG / Pt, np-NG / PtCu, np-NG / PtPt and np-NG / AuPt. Compared with single platinum atoms, the energy of platinum changes after forming diatomic structures with different metals, indicating that there is interaction between metals.

[0100] Figure 8 Electrochemical hydrogen evolution performance of np-NG / AuPt in 1.0 M KOH electrolyte at a current density of 10 mA / cm 2 The potential is 104mV.

[0101] Comparative Example 1:

[0102] The difference compared with Example 1 is that after the working electrode is prepared in step (4) of Example 1, this comparative example does not perform underpotential deposition, but instead performs bulk copper deposition on np-NG for 120 seconds in a 0.1M H2SO4 saturated Ar solution containing 2mM CuSO4 by controlling the potential at -0.10V to obtain nitrogen-doped nanoporous graphene (Cu bulk) loaded with copper nanoparticles.

[0103] Comparative Example 2:

[0104] The difference from Example 4 is that after step (5) of Example 1, step (6) is not performed in this comparative example to obtain np-NG / Au. In the absence of Pt, np-NG / Au exhibits poor electrochemical hydrogen evolution performance under both acidic and alkaline conditions. 2 The overpotentials of np-NG / Au in 0.5M H2SO4 and 1.0M KOH electrolytes are 260mV and 541mV, respectively.

[0105] Comparative Example 3:

[0106] The difference compared with Examples 1 and 2 is that the precursor for growing graphene in step (2) of Example 1 is changed to toluene in this comparative example. After np-Ni is pre-reduced and annealed at 800°C for 5 minutes, toluene gas is introduced into the furnace, and the reaction is continued at 800°C for 5 minutes. Then the furnace is immediately opened and cooled to room temperature with a fan to obtain np-Ni / G. The np-Ni / G sheet is etched at 50°C with a 2.0M HCl solution containing 5mM FeCl3 for 12 hours, and then rinsed with deionized water five times. Then, nanoporous graphene (np-G) without nitrogen doping is obtained by freeze drying technology.

[0107] The difference compared with Example 1 is that in this comparative example, np-G is used instead of np-NG in step (5) of Example 1 to perform electrodeposition for 120 seconds at +0.10 V, and then the electrodeposition is carried out in an Ar saturated solution of 50 mM H2SO4 containing 5 mM K2PtCl4 for 5 minutes. The final product is a platinum single atom loaded nanoporous graphene (np-G / Pt) single atom catalyst. Fig. 9 is a curve diagram of underpotential deposition on np-G under constant voltage conditions. Compared with np-NG in Example 1, the amount of copper that can be underpotentially deposited on np-G is very small, and the current density during underpotential deposition is almost maintained at 0 mA / cm 2 .

[0108] np-G / Pt exhibited poor catalytic activity under both acidic and alkaline conditions. 2 The overpotentials of np-G / Pt in 0.5M H2SO4 and 1.0M KOH electrolytes are 211mV and 324mV, respectively.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a supported metal atom catalyst, characterized in that: It includes the following steps: Step 1, preparing nitrogen-doped nanoporous graphene: first growing nitrogen-doped graphene on the surface of a nanoporous nickel template by chemical vapor deposition, and then corroding the nanoporous nickel template on which the nitrogen-doped graphene is grown to obtain self-supporting nitrogen-doped nanoporous graphene; Step 2: Prepare the first metal single atom by underpotential deposition and electrical replacement: first, deposit the metal single atom to be replaced on the surface of the nitrogen-doped nanoporous graphene underpotential deposition to obtain the nitrogen-doped nanoporous graphene loaded with the metal single atom to be replaced; then, place the nitrogen-doped nanoporous graphene loaded with the metal single atom to be replaced in a first metal precursor solution, let it stand at an open circuit voltage, replace the metal single atom to be replaced loaded on the nitrogen-doped nanoporous graphene with the first metal single atom, and obtain the first metal single atom catalyst loaded on the nitrogen-doped nanoporous graphene.

2. The method for preparing a supported metal atom catalyst according to claim 1, characterized in that: Also includes: Step three, prepare the first metal and the second metal diatoms by underpotential deposition and electrical replacement: first, underpotentially deposit the metal single atom to be replaced on the nitrogen-doped nanoporous graphene loaded with the first metal single atom to obtain the nitrogen-doped nanoporous graphene loaded with the first metal and the metal diatoms to be replaced; then, place the nitrogen-doped nanoporous graphene loaded with the first metal and the metal diatoms to be replaced in a second metal precursor solution, let it stand at an open circuit voltage, replace the metal single atom to be replaced loaded on the nitrogen-doped nanoporous graphene with the second metal single atom, and obtain the first metal and the second metal diatomic catalyst loaded on the nitrogen-doped nanoporous graphene.

3. The method for preparing a supported metal atom catalyst according to claim 1, characterized in that: The preparation method of the nanoporous nickel template comprises: The nickel-based alloy sheet is immersed in a weak acid solution formed by a strong acid and a weak base salt, and other metal elements except nickel in the nickel-based alloy sheet are removed to obtain a nanoporous nickel template.

4. The method for preparing a supported metal atom catalyst according to claim 3, characterized in that: The nickel-based alloy sheet is Ni 30 Mn 70 , the strong acid and weak base salt is ammonium sulfate.

5. The method for preparing a supported metal atom catalyst according to claim 1, characterized in that: The step of growing nitrogen-doped graphene on the nanoporous nickel template by chemical vapor deposition in step 1 comprises: The nanoporous nickel template is placed in a heating treatment device, and nitrogen-doped graphene is grown on the nanoporous nickel template by vapor deposition using a carbon source and a carbon source.

6. The method for preparing a supported metal atom catalyst according to claim 5, characterized in that: The nitrogen source and carbon source are melamine, and the area of ​​the nanoporous nickel template (cm 2 ) and the melamine dosage (mg) are in a ratio of 1:10 to 1:100, the protective gas in the heating treatment equipment is 20 to 200 sccm argon and 20 to 200 sccm hydrogen, and the growth temperature of the nitrogen-doped graphene is 700°C to 1000°C.

7. The method for preparing a supported metal atom catalyst according to claim 1, characterized in that: The step of further corroding the nanoporous nickel template on the surface of which the nitrogen-doped graphene is grown to obtain self-supporting nitrogen-doped nanoporous graphene comprises: The nanoporous nickel template with nitrogen-doped graphene grown on the surface is immersed in a HCl solution containing FeCl3 to corrode the nanoporous nickel and obtain self-supporting nitrogen-doped nanoporous graphene.

8. The method for preparing a supported metal atom catalyst according to claim 2, characterized in that: The step 2 of depositing the metal single atom to be replaced on the surface of the nitrogen-doped nanoporous graphene at an underpotential to obtain the nitrogen-doped nanoporous graphene loaded with the metal single atom to be replaced comprises: A metal precursor solution to be replaced is added, a platinum sheet is used as a counter electrode, a silver / silver chloride electrode is used as a reference electrode, and the nitrogen-doped nanoporous graphene is used as a working electrode. Single-atom underpotential deposition of the metal to be replaced is performed on the surface of the nitrogen-doped nanoporous graphene to obtain nitrogen-doped nanoporous graphene loaded with single-atom metal to be replaced; The step 3 of underpotentially depositing a metal single atom to be replaced on the nitrogen-doped nanoporous graphene loaded with a first metal single atom to obtain nitrogen-doped nanoporous graphene loaded with a first metal and a metal double atom to be replaced comprises: A metal precursor solution to be replaced is added, a platinum sheet is used as a counter electrode, a silver / silver chloride electrode is used as a reference electrode, and a nitrogen-doped nanoporous graphene loaded with a first metal single atom is used as a working electrode. The first metal single atom underpotential deposition is performed on the surface of the nitrogen-doped nanoporous graphene loaded with a first metal single atom to obtain nitrogen-doped nanoporous graphene loaded with diatomic amounts of the first metal and the metal to be replaced.

9. The method for preparing a supported metal atom catalyst according to claim 8, characterized in that: The metal to be replaced is lead, iron, cobalt, nickel or copper, and correspondingly, the metal precursor solution to be replaced is a nitric acid solution of lead nitrate, a sulfuric acid solution of ferrous sulfate, a sulfuric acid solution of cobalt sulfate, a sulfuric acid solution of nickel sulfate or a sulfuric acid solution of copper sulfate.

10. The method for preparing a supported metal atom catalyst according to claim 9, characterized in that: In the copper sulfate sulfuric acid solution, the sulfuric acid solution is 0.1 mol / L to 0.5 mol / L, and the concentration of the added copper sulfate is 2 mmol / L to 20 mmol / L; the underpotential deposition voltage is 0 V to 0.3 V relative to the silver / silver chloride electrode, and the deposition time is 30 s to 600 s.

11. The method for preparing a supported metal atom catalyst according to claim 1, characterized in that: In step 2, the first metal precursor solution is a sulfuric acid solution containing chloroauric acid or potassium chloroplatinate, and correspondingly, the first metal is gold or platinum.

12. The method for preparing a supported metal atom catalyst according to claim 11, characterized in that: In the sulfuric acid solution containing chloroauric acid, the sulfuric acid solution is 5mmol / L to 50mmol / L, and the concentration of chloroauric acid is 1mmol / L to 10mmol / L; the standing time under open circuit voltage in step 2 is 1min to 30min.

13. The method for preparing a supported metal atom catalyst according to claim 2, characterized in that: In step three, the second metal precursor solution is a sulfuric acid solution containing potassium tetrachloropalladate, ruthenium chloride, rhodium chloride or potassium tetrachloroplatinate, and correspondingly, the second metal is palladium, ruthenium, rhodium or platinum.

14. The method for preparing a supported metal atom catalyst according to claim 13, characterized in that: In the sulfuric acid solution containing potassium tetrachloroplatinate, the sulfuric acid solution is 5mmol / L to 50mmol / L, the concentration of potassium tetrachloroplatinate is 1mmol / L to 10mmol / L, and the standing time at the open circuit voltage in step 3 is 1min to 30min.

15. A supported metal atom catalyst prepared by the method according to any one of claims 1 to 14, comprising a gold-platinum diatomic catalyst supported on nitrogen-doped nanoporous graphene.

16. Use of the supported metal atom catalyst according to claim 15 as a water electrolysis catalyst.

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