Atomic-scale precise preparation method of core-shell Pt-based hydrogen oxidation catalyst

Abstract

The invention provides an atomic-scale precise preparation method of a core-shell Pt-based hydrogen oxidation catalyst, which comprises the following steps: A) carrying out reaction on a metal platinum precursor and an oxidizing substance on a nitrogen-carbon carrier through atomic layer deposition to grow metal platinum, and carrying out pretreatment to obtain a nitrogen-carbon carrier loaded with platinum nanoparticles; and B) selectively coating the nitrogen-carbon carrier loaded with the platinum nanoparticles with metal ruthenium by using a metal ruthenium precursor, an oxidizing substance and a reducing substance through an atomic layer deposition technology to obtain the core-shell Pt-based hydrogen oxidation catalyst. According to the invention, the deposition controllability of the atomic layer deposition technology is utilized, the metal ruthenium Ru is accurately wrapped on the platinum nanoparticles to form a core-shell structure, the elemental Ru is not dispersed on the nitrogen-carbon carrier, the structural accuracy is ensured, and the prepared catalyst also has good hydrogen oxidation activity and CO poisoning resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and particularly relates to an atomic-precision preparation method of a core-shell Pt-based hydrogen oxidation catalyst. Background Art

[0002] In order to reduce the dependence on fossil fuels, researchers have begun to focus on the utilization of clean and efficient hydrogen energy. In hydrogen energy utilization technologies, anion exchange membrane fuel cells (AEMFCs) play a crucial role in efficient hydrogen conversion, and the hydrogen oxidation reaction (HOR) is an important anodic reaction in AEMFCs. Therefore, more and more researchers have begun to design and prepare HOR catalysts. So far, Pt-based catalysts are the most effective HOR catalysts reported. However, the hydrogen raw material gas contains impurities such as CO, and Pt has an obvious adsorption affinity for CO, which leads to the inactivation of Pt-based catalysts. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide an atomic-precision preparation method of a core-shell Pt-based hydrogen oxidation catalyst, which can accurately prepare a core-shell structured Pt-Ru catalyst, has good activity for hydrogen oxidation, and also has good CO poisoning resistance.

[0004] The present invention provides a preparation method of a core-shell Pt-based hydrogen oxidation catalyst, including the following steps:

[0005] A) Reacting a metal platinum precursor and an oxidizing substance by atomic layer deposition on a nitrogen-carbon support to grow metallic platinum, and then obtaining a nitrogen-carbon support loaded with platinum nanoparticles through pretreatment;

[0006] B) Selectively coating metallic ruthenium on the nitrogen-carbon support loaded with platinum nanoparticles by atomic layer deposition technology using a metal ruthenium precursor, an oxidizing substance, and a reducing substance to obtain a core-shell Pt-based hydrogen oxidation catalyst.

[0007] Preferably, the nitrogen-carbon support is prepared according to the following method:

[0008] Calcining urea to obtain g-C3N4;

[0009] Dispersing the g-C3N4 in an aqueous glucose solution, reacting at 150 - 300 °C for 5 - 12 h, centrifuging, washing, and drying after cooling to obtain a g-C3N4@glu precursor;

[0010] Calcining the g-C3N4@glu precursor in an Ar atmosphere to obtain a nitrogen-carbon support.

[0011] Preferably, the temperature for calcining urea is 300 - 800 °C, and the time is 3 - 10 h;

[0012] The calcination temperature of the g-C3N4@glu precursor is 500 - 1200 °C, and the time is 3 - 12 h.

[0013] Preferably, the mass ratio of g-C3N4 to glucose is (0.5 - 1):3.

[0014] Preferably, the atomic layer deposition sequence in step A) is: exposure of the metal platinum precursor; removal of the metal platinum precursor; exposure of the oxidizing substance; removal of the oxidizing substance;

[0015] The atomic layer deposition sequence in step B) is: exposure of the metal ruthenium precursor; removal of the metal ruthenium precursor; exposure of the oxidizing substance; removal of the oxidizing substance; exposure of the reducing substance; removal of the reducing substance.

[0016] Preferably, the reaction temperature in step A) is 120 - 300 °C;

[0017] The time sequence of atomic layer deposition is as follows: the exposure time of the metal platinum precursor is 100 - 500 s; the removal time of the metal platinum precursor is 100 - 500 s; the exposure time of the oxidizing substance is 300 - 1000 s; the removal time of the oxidizing substance is 100 - 500 s.

[0018] Preferably, the reaction temperature in step B) is 120 - 300 °C;

[0019] The time sequence of atomic layer deposition is as follows: the exposure time of the metal ruthenium precursor is 100 - 500 s; the removal time of the metal ruthenium precursor is 100 - 500 s; the exposure time of the oxidizing substance is 300 - 1000 s; the removal time of the oxidizing substance is 100 - 500 s; the exposure time of the reducing substance is 300 - 1000 s; the removal time of the reducing substance is 100 - 500 s.

[0020] Preferably, the reduction temperature in the pretreatment of step A) is 200 - 800 °C, and the time is 0.5 - 5 h.

[0021] Preferably, the core-shell Pt-based hydrogen oxidation catalyst includes a nitrogen-carbon support;

[0022] and a core-shell metal supported on the nitrogen-carbon support;

[0023] The core-shell metal has a core of metal platinum and a shell of metal ruthenium.

[0024] Preferably, the loading amount of metal platinum in the core-shell Pt-based hydrogen oxidation catalyst is 0.5 - 2 wt%, and the loading amount of metal ruthenium is 0.2 - 3 wt%.

[0025] The present invention provides a method for preparing a core-shell Pt-based hydrogen oxidation catalyst, comprising the following steps: A) Reacting a metal platinum precursor and an oxidizing substance by atomic layer deposition on a nitrogen-carbon support to grow metallic platinum, and then obtaining a nitrogen-carbon support loaded with platinum nanoparticles through pretreatment; B) Selectively coating metallic ruthenium on the nitrogen-carbon support loaded with platinum nanoparticles by atomic layer deposition technology using a metal ruthenium precursor, an oxidizing substance, and a reducing substance to obtain a core-shell Pt-based hydrogen oxidation catalyst. By utilizing the selective deposition characteristic of atomic layer deposition technology, the present invention precisely coats metallic ruthenium Ru on platinum nanoparticles to form a core-shell structure, without elemental Ru being dispersed on the nitrogen-carbon support. While ensuring the structural accuracy, the prepared catalyst also has good hydrogen oxidation activity and the ability to resist CO poisoning. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is the content of metallic Ru after depositing Ru with different cycle numbers on Pt / NC and the nitrogen-carbon support;

[0027] Figure 2 is the atomic resolution HAADF-stem image of the core-shell Pt-based hydrogen oxidation catalyst;

[0028] Figure 3 is the TEM image of the core-shell Pt-based hydrogen oxidation catalyst and its corresponding particle size statistics;

[0029] Figure 4 is the alkaline hydrogen oxidation polarization curve of the core-shell Pt-based hydrogen oxidation catalyst;

[0030] Figure 5 is the relative time-current response curve of the core-shell Pt-based hydrogen oxidation catalyst at 0.1 V vs RHE. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The present invention provides a method for preparing a core-shell Pt-based hydrogen oxidation catalyst, comprising the following steps:

[0032] A) Reacting a metal platinum precursor and an oxidizing substance by atomic layer deposition on a nitrogen-carbon support to grow metallic platinum, and then obtaining a nitrogen-carbon support loaded with platinum nanoparticles through pretreatment;

[0033] B) Selectively coating metallic ruthenium on the nitrogen-carbon support loaded with platinum nanoparticles by atomic layer deposition technology using a metal ruthenium precursor, an oxidizing substance, and a reducing substance to obtain a core-shell Pt-based hydrogen oxidation catalyst.

[0034] The present invention utilizes the selective deposition characteristics of atomic layer deposition technology (or atomic layer deposition method or atomic layer deposition mode) to accurately deposit metallic ruthenium on platinum nanoparticles to form a core-shell structure; compared with the traditional hydrothermal method for synthesizing core-shell structures, the present invention can ensure that metallic ruthenium (Ru) is accurately wrapped on platinum nanoparticles while ensuring that no single atomic Ru is dispersed on the carrier, thereby ensuring the accuracy of the catalyst structure; while ensuring the accuracy of the structure, it also has good hydrogen oxidation activity; and it also overcomes the disadvantage that Pt-based hydrogen oxidation catalysts are prone to adsorb CO, which causes the catalyst to be deactivated.

[0035] In the present invention, the nitrogen-carbon carrier is prepared according to the following method:

[0036] Calcinate urea to obtain g-C3N4;

[0037] The g-C3N4 is dispersed in a glucose aqueous solution, reacted at 150-300° C. for 5-12 hours, cooled, centrifuged, washed and dried to obtain a g-C3N4@glu precursor;

[0038] The g-C3N4@glu precursor is calcined in an Ar atmosphere to obtain a nitrogen-carbon carrier.

[0039] The present invention calcines urea to obtain g-C3N4. The present invention preferably performs calcination in a muffle furnace; the urea calcination temperature is 300-800°C, and the time is 3-10 hours; the present invention preferably heats the temperature to the calcination temperature at a heating rate of 5°C / min.

[0040] The present invention disperses the g-C3N4 in a glucose aqueous solution, reacts at 150-300°C for 5-12h, and obtains a g-C3N4@glu precursor after centrifugation, washing and drying after cooling. The mass ratio of g-C3N4 to glucose in the present invention is (0.5-1):3. The concentration of the glucose aqueous solution is 0.15mol / L-0.5mol / L; in a specific embodiment, the concentration of the glucose aqueous solution is 0.2mol / L, and the volume of the glucose aqueous solution is 60mL. Deionized water is used for washing. The present invention preferably disperses the g-C3N4 in the glucose aqueous solution and then fully ultrasonically disperses it at room temperature, and then places the dispersed solution in a high-temperature reactor and reacts in an oven.

[0041] After obtaining the g-C3N4@glu precursor, the present invention calcines the g-C3N4@glu precursor in an Ar atmosphere to obtain a nitrogen-carbon carrier. The calcination temperature of the g-C3N4@glu precursor is 500-1200 °C, specifically 500 °C, 550 °C, 600 °C, 650 °C, 700 °C, 750 °C, 800 °C, 850 °C, 900 °C, 950 °C, 1000 °C, 1050 °C, 1100 °C, 1150 °C or 1200 °C; the calcination time is 3-12 h, specifically 3 h, 3.5 h, 4.0 h, 4.5 h, 5.0 h, 5.5 h, 6.0 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h, 10 h, 10.5 h, 11 h, 11.5 h or 12 h.

[0042] In step A) of the present invention, the atomic layer deposition sequence is as follows: exposure of the metal platinum precursor; removal of the metal platinum precursor; exposure of the oxidizing substance; removal of the oxidizing substance; the time sequence of atomic layer deposition is as follows: the exposure time of the metal platinum precursor is 100-500 s; the removal time of the metal platinum precursor is 100-500 s, preferably 200-400 s; the exposure time of the oxidizing substance is 300-1000 s, preferably 400-900 s; the removal time of the oxidizing substance is 100-500 s. In specific embodiments, the deposition times of the platinum precursor are 300 s-300 s-600 s-300 s in sequence.

[0043] The metal platinum precursor used in the present invention can be any metal platinum precursor well-known to those skilled in the art that can be used in atomic layer deposition technology, and there is no special limitation. In the present invention, it is preferably trimethyl(methylcyclopentadienyl)platinum (MeCpPtMe3). The oxidizing substance used can be any oxidizing substance well-known to those skilled in the art, and oxygen is preferably used. The reaction temperature in step A) of the present invention is 120-300 °C; specifically 120 °C, 140 °C, 160 °C, 180 °C, 200 °C, 220 °C, 240 °C, 260 °C, 280 °C or 300 °C.

[0044] In step A) of the present invention, the temperature of the pre-treatment reduction is 200-800 °C, specifically 200 °C, 230 °C, 260 °C, 290 °C, 320 °C, 350 °C, 380 °C, 410 °C, 440 °C, 470 °C, 500 °C, 530 °C, 560 °C, 590 °C, 620 °C, 650 °C, 680 °C, 710 °C, 740 °C, 770 °C or 800 °C; the time is 0.5-5 h, specifically 0.5 h, 1.0 h, 1.5 h, 2.0 h, 2.5 h, 3.0 h, 3.5 h, 4.0 h, 4.5 h or 5.0 h. The reducing atmosphere used for the reduction is 10% H2 / Ar atmosphere.

[0045] In the present invention, a ruthenium metal precursor, an oxidizing substance, and a reducing substance are reacted through atomic layer deposition technology on a nitrogen-carbon support loaded with platinum nanoparticles to selectively coat the ruthenium metal, thereby obtaining a core-shell type Pt-based hydrogen oxidation catalyst.

[0046] In step B) of the present invention, the atomic layer deposition sequence is as follows: exposure of the ruthenium metal precursor; removal of the ruthenium metal precursor; exposure of the oxidizing substance; removal of the oxidizing substance; exposure of the reducing substance; removal of the reducing substance. The time sequence of atomic layer deposition is successively: the exposure time of the ruthenium metal precursor is 100 - 500 s, preferably 200 - 400 s; the removal time of the ruthenium metal precursor is 100 - 500 s, preferably 200 - 400 s; the exposure time of the oxidizing substance is 300 - 1000 s, preferably 400 - 800 s; the removal time of the oxidizing substance is 100 - 500 s; the exposure time of the reducing substance is 300 - 1000 s, preferably 500 - 900 s; the removal time of the reducing substance is 100 - 500 s. In a specific embodiment, the time of atomic layer deposition is successively 100 s - 300 s - 600 s - 300 s - 600 s - 300 s. In the present invention, the Pt element is distributed on the nitrogen-carbon support in the form of nanoparticles, while the Ru element is precisely coated on the Pt nanoparticles to form Ru shell layers with different thicknesses.

[0047] The ruthenium metal precursor in the present invention can be any ruthenium metal precursor well-known to those skilled in the art that can be used for atomic layer deposition, without any special limitation. In the present invention, Ru(CpEt)2 is preferably used. The reducing substance used is preferably hydrogen. The reaction temperature in step B) of the present invention is 120 - 300 °C, specifically 120 °C, 130 °C, 140 °C, 150 °C, 160 °C, 170 °C, 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, 250 °C, 260 °C, 270 °C, 280 °C, 290 °C or 300 °C; preferably 150 - 270 °C.

[0048] The present invention utilizes the selective deposition characteristic of atomic layer deposition technology. The nitrogen-carbon support prepared by a specific method is used to deposit the ruthenium metal, and it can be precisely deposited on the platinum nanoparticles. Compared with the traditional hydrothermal method for synthesizing core-shell structures, the present invention can ensure that the metal Ru is precisely coated on the platinum nanoparticles while ensuring that no Ru is dispersed on the support.

[0049] The core-shell type Pt-based hydrogen oxidation catalyst prepared by the above method in the present invention includes a nitrogen-carbon support;

[0050] and a core-shell metal supported on the nitrogen-carbon support;

[0051] The core-shell metal has a metal platinum core and a metal ruthenium shell.

[0052] In the present invention, the loading amount of metallic platinum in the core-shell type Pt-based hydrogen oxidation catalyst is 0.5 to 2 wt%, specifically the loading amounts are 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, or 2.0 wt%; the loading amount of metallic ruthenium is 0.2 to 3 wt%, and specifically the loading amounts of metallic ruthenium are 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2.0 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.7 wt%, 2.8 wt%, 2.9 wt%, or 3.0 wt%.

[0053] The catalyst prepared by the above method provided by the present invention has good hydrogen oxidation activity and overcomes the disadvantage that the Pt-based hydrogen oxidation catalyst is prone to adsorb CO, resulting in catalyst deactivation.

[0054] In order to further illustrate the present invention, the atomic-level precise preparation method of a core-shell type Pt-based hydrogen oxidation catalyst provided by the present invention will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0055] Example 1

[0056] Prepare a nitrogen-carbon support (NC):

[0057] 1.1 In a muffle furnace, heat 30 g of urea to 700 °C at a rate of 5 °C / min and maintain for 5 hours to calcine it into g-C3N4.

[0058] 1.2 Disperse a certain amount of 1.0 g of g-C3N4 in 60 ml of a 0.2 M glucose aqueous solution, ultrasonically disperse it at room temperature for 8 h, then place the dispersed solution in a 100 ml high-temperature reaction kettle, react in an oven for several hours, the temperature is 200 °C, the time is 8 hours, after cooling, centrifuge and wash with water, and dry at 80 °C to obtain a g-C3N4@glu precursor.

[0059] 1.3 In an Ar atmosphere, heat the g-C3N4@glu precursor to 700 °C at a rate of 5 °C / min and maintain at this temperature for several hours to obtain a nitrogen-carbon support (NC), and the time is 5 hours.

[0060] Example 2

[0061] An atomic layer deposition equipment (ACME (Beijing) Technology Co., Ltd.) was used, and ultra-pure N2 (99.999%) was used as the carrier gas with a flow rate of 20 sccm.

[0062] 2.1 At 180 °C, MeCpPtMe3 (Sigma-Aldrich, 98%) was reacted with oxygen (99.999%) to grow metallic Pt on the nitrogen-carbon support synthesized in Example 1, and the Pt loading was 0.7 wt%. Before introducing, MeCpPtMe3 was preheated to 70 °C. The time sequence of atomic layer deposition was t1 (exposure time of metal platinum precursor) - t2 (purge time of metal platinum precursor) - t3 (exposure time of oxygen) - t4 (purge time of oxygen), and the corresponding durations were 300 s - 300 s - 600 s - 300 s respectively.

[0063] 2.2 In a 10% H2 / Ar atmosphere, the nitrogen-carbon support deposited with platinum was heated to 600 °C at a rate of 5 °C / min and held at this temperature for 2 hours to obtain Pt nanoparticles, denoted as Pt / NC.

[0064] 2.3 At 180 °C, Ru(CpEt)2 (Sigma-Aldrich, 98%) was reacted with oxygen (99.999%) or hydrogen (99.999%) to grow Ru on Pt / NC. Before introducing, Ru(CpEt)2 was preheated to 80 °C. The time sequence of atomic layer deposition was t1 (exposure time of metal ruthenium precursor) - t2 (purge time of metal ruthenium precursor) - t3 (exposure time of oxygen) - t4 (purge time of oxygen) - t5 (exposure time of hydrogen) - t6 (purge time of hydrogen), and the corresponding durations were 100 s - 300 s - 600 s - 300 s - 600 s - 300 s respectively. Five Ru deposition cycles were carried out, denoted as Pt@Ru / NC-5c.

[0065] Example 3

[0066] An atomic layer deposition equipment (ACME (Beijing) Technology Co., Ltd.) was used, and ultra-pure N2 (99.999%) was used as the carrier gas with a flow rate of 20 sccm.

[0067] 3.1 At 180 °C, react MeCpPtMe3 (Sigma - Aldrich, 98%) with oxygen (99.999%) to grow metallic Pt on the nitrogen - carbon support synthesized in Example 1. The loading of Pt is 0.7 wt%. Pre - heat MeCpPtMe3 to 70 °C before introducing. The time sequence of atomic layer deposition is t1 (exposure time of metal platinum precursor) - t2 (purge time of metal platinum precursor) - t3 (exposure time of oxygen) - t4 (purge time of oxygen), and the corresponding durations are 300 s - 300 s - 600 s - 300 s respectively.

[0068] 3.2 In a 10% H2 / Ar atmosphere, heat the nitrogen - carbon support deposited with platinum to 600 °C at a rate of 5 °C / min and hold at this temperature for 2 hours to obtain Pt nanoparticles, denoted as Pt / NC.

[0069] 3.3 At 180 °C, react Ru(CpEt)2 (Sigma - Aldrich, 98%) with oxygen (99.999%) or hydrogen (99.999%) to grow Ru on Pt / NC. Pre - heat Ru(CpEt)2 to 80 °C before introducing. The time sequence of atomic layer deposition is t1 (exposure time of metal ruthenium precursor) - t2 (purge time of metal ruthenium precursor) - t3 (exposure time of oxygen) - t4 (purge time of oxygen) - t5 (exposure time of hydrogen) - t6 (purge time of hydrogen), and the corresponding durations are 100 s - 300 s - 600 s - 300 s - 600 s - 300 s respectively. Cycle 10 Ru deposition cycles, denoted as Pt@Ru / NC - 10c.

[0070] Example 4

[0071] Use an atomic layer deposition equipment (ACME (Beijing) Technology Co., Ltd.), with ultra - pure N2 (99.999%) as the carrier gas and a flow rate of 20 sccm.

[0072] 4.1 At 180 °C, react MeCpPtMe3 (Sigma - Aldrich, 98%) with oxygen (99.999%) to grow metallic Pt on the nitrogen - carbon support synthesized in Example 1. The loading of Pt is 0.7 wt%. Pre - heat MeCpPtMe3 to 70 °C before introducing. The time sequence of atomic layer deposition is t1 (exposure time of metal platinum precursor) - t2 (purge time of metal platinum precursor) - t3 (exposure time of oxygen) - t4 (purge time of oxygen), and the corresponding durations are 300 s - 300 s - 600 s - 300 s respectively.

[0073] 4.2 In a 10% H2 / Ar atmosphere, the nitrogen-carbon support deposited with platinum was heated to 600 °C at a rate of 5 °C / min and held at this temperature for 2 hours to obtain Pt nanoparticles, denoted as Pt / NC.

[0074] 4.3 At 180 °C, Ru(CpEt)2 (Sigma-Aldrich, 98%) was reacted with oxygen (99.999%) or hydrogen (99.999%) to grow Ru on Pt / NC. Before introduction, Ru(CpEt)2 was preheated to 80 °C. The time sequence of atomic layer deposition was t1 (exposure time of ruthenium metal precursor) - t2 (purge time of ruthenium metal precursor) - t3 (exposure time of oxygen) - t4 (purge time of oxygen) - t5 (exposure time of hydrogen) - t6 (purge time of hydrogen), and the corresponding durations were 100 s - 300 s - 600 s - 300 s - 600 s - 300 s respectively. 15 Ru deposition cycles were carried out, denoted as Pt@Ru / NC-15c.

[0075] Example 5

[0076] An atomic layer deposition equipment (ACME (Beijing) Technology Co., Ltd.) was used, and ultra-pure N2 (99.999%) was used as the carrier gas with a flow rate of 20 sccm.

[0077] 5.1 At 180 °C, MeCpPtMe3 (Sigma-Aldrich, 98%) was reacted with oxygen (99.999%) to grow metallic Pt on the nitrogen-carbon support synthesized in Example 1, and the Pt loading was 0.7 wt%. Before introduction, MeCpPtMe3 was preheated to 70 °C. The time sequence of atomic layer deposition was t1 (exposure time of platinum metal precursor) - t2 (purge time of platinum metal precursor) - t3 (exposure time of oxygen) - t4 (purge time of oxygen), and the corresponding durations were 300 s - 300 s - 600 s - 300 s respectively.

[0078] 5.2 In a 10% H2 / Ar atmosphere, the nitrogen-carbon support deposited with platinum was heated to 600 °C at a rate of 5 °C / min and held at this temperature for 2 hours to obtain Pt nanoparticles, denoted as Pt / NC.

[0079] 5.3 At 180 °C, Ru(CpEt)2 (Sigma-Aldrich, 98%) was reacted with oxygen (99.999%) or hydrogen (99.999%) to grow Ru on Pt / NC. Ru(CpEt)2 was preheated to 80 °C before introduction. The time sequence of atomic layer deposition was t1 (exposure time of ruthenium metal precursor) - t2 (purge time of ruthenium metal precursor) - t3 (oxygen exposure time) - t4 (oxygen purge time) - t5 (hydrogen exposure time) - t6 (hydrogen purge time), with corresponding durations of 100 s - 300 s - 600 s - 300 s - 600 s - 300 s respectively. 20 Ru deposition cycles were carried out, denoted as Pt@2ML-Ru / NC-20c.

[0080] Comparative example

[0081] The Pt@Ru / NC-10c catalyst obtained in Example 3 was placed in a 10% H2 / Ar atmosphere and heated to 600 °C at a rate of 5 °C / min, and held at this temperature for 2 hours to obtain a PtRu alloy, denoted as PtRu alloy / NC.

[0082] Test example

[0083] Rotating disk electrode test method

[0084] Electrochemical experiments were carried out in a three-electrode system using a Chenghua workstation. The catalyst was uniformly dispersed in 950 μL of isopropanol solution, and 50 μL of 5% Nafion solution was added to prepare the ink. After ultrasonic treatment for 30 min, the ink was dropped on a glassy carbon electrode with a diameter of 2 mm and dried. The loading of metallic Pt on the rotating disk electrode (RDE) was controlled at 15 μg·cm -2 .

[0085] Before the linear sweep voltammetry test for hydrogen oxidation, the glassy carbon electrode with the catalyst was activated by cyclic voltammetry in 0.1 M KOH solution saturated with H2 under the condition of 0 - 1.0 V vs RHE. After activation, in 0.1 M KOH solution saturated with H2, within the range of 0 V - 0.15 V vs RHE, a potential sweep was carried out at a scan rate of 5 mV·s -1 and a rotation speed of 1600 rpm to obtain the hydrogen oxidation polarization curve. All electrochemical experiments were carried out at room temperature.

[0086] Relative time current response test:

[0087] Under the conditions of 0.1 V vs RHE potential and 0.1 M KOH solution saturated with 1000 ppm CO / H2, for the catalyst in the example (loading of 10 μg Pt ·cm -2)Perform relative time current response experiments.

[0088] To ensure the precise synthesis of the core-shell structure, verification experiments were first carried out in the present invention, as Figure 1 shown. Atomic layer deposition of ruthenium metal was carried out on pure nitrogen-carbon support (NC) and nitrogen-carbon support loaded with platinum nanoparticles (Pt / NC) respectively. It was found that as the deposition cycle of ruthenium metal increased, the ruthenium loading on Pt / NC gradually increased, while the ruthenium loading on NC was almost zero, indicating that ruthenium would only wrap on platinum nanoparticles and would not be loaded on the support, ensuring the precision of the synthesis of the core-shell catalyst.

[0089] The hydrogen oxidation catalysts obtained in Examples 2-5 and the comparative examples were analyzed by transmission electron microscopy to obtain TEM images, and the particle size statistics were carried out for each example, as Figure 2 and Figure 3 shown. Among them, a) represents Pt / NC, b) represents Pt@Ru / NC-5c, c) represents Pt@Ru / NC-10c, d) represents Pt@Ru / NC-15c, e) represents Pt@-Ru / NC-20c, f) represents PtRu alloy / NC. As Figure 2 can be seen, the platinum nanoparticles are of uniform size, and as the ruthenium metal content increases, the size of the PtRu core-shell particles also increases. According to Figure 3 , the PtRu core-shell structure was well synthesized in the present invention, which is significantly different from the PtRu alloy.

[0090] Figure 4 is the alkaline hydrogen oxidation polarization curve of the PtRu core-shell catalyst, and linear sweep voltammetry was carried out in a 0.1 M KOH solution saturated with H2. Compared with Pt / NC, the HOR performance of Pt@Ru / NC-5c decreased slightly, indicating that the limited Ru shell layer would affect the HOR performance. In contrast, the HOR performance of Pt@Ru / NC-10c was better than that of Pt / NC and Pt@Ru / NC-5c, and the current density reached 2.42 mA·cm -2 . However, as the Ru shell thickness increased, the behavior of the catalyst was closer to that of pure Ru / NC.

[0091] Figure 5 is the current response curve of the PtRu core-shell catalyst with respect to time in a 0.1 M KOH solution saturated with 1000 ppm CO / H2. After continuous operation for 1 hour, the current of Pt@Ru / NC-10c remained at 80%. In contrast, after 1 hour of HOR catalysis, Pt / NC and Pt@Ru / NC-5c were completely deactivated, Pt@Ru / NC-15c maintained 70% of its initial activity, Pt@Ru / NC-20c, Ru / NC, PtRu alloyBoth / NC lost 60% of their activity.

[0092] As can be seen from the above examples, the present invention provides a method for preparing a core-shell Pt-based hydrogen oxidation catalyst, comprising the following steps: A) Reacting a metal platinum precursor and an oxidizing substance on a nitrogen-carbon support by atomic layer deposition technology to grow metal platinum, and then obtaining a nitrogen-carbon support loaded with platinum nanoparticles through pretreatment; B) Selectively coating metal ruthenium on the nitrogen-carbon support loaded with platinum nanoparticles by atomic layer deposition technology using a metal ruthenium precursor, an oxidizing substance and a reducing substance to obtain a core-shell Pt-based hydrogen oxidation catalyst. The present invention utilizes the selectivity of atomic layer deposition technology to precisely coat metal ruthenium Ru on platinum nanoparticles to form a core-shell structure, without Ru being dispersed on the nitrogen-carbon support. While ensuring the structural accuracy, the prepared catalyst also has good hydrogen oxidation activity and the ability to resist CO poisoning.

[0093] The above is only the preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for atomic-level precision preparation of a core-shell Pt-based hydrogen oxidation catalyst, comprising the following steps: A) a metal platinum precursor and an oxidizing substance are reacted and grown on a nitrogen-carbon carrier by atomic layer deposition, and then a nitrogen-carbon carrier loaded with platinum nanoparticles is obtained by pre-treatment; B) The metal ruthenium precursor, oxidizing material and reducing material are selectively coated on the nitrogen-carbon carrier loaded with platinum nanoparticles by atomic layer deposition technology to obtain a core-shell Pt-based hydrogen oxidation catalyst.

2. The preparation method according to claim 1, characterized in that: The nitrogen-carbon carrier is prepared according to the following method: Calcinate urea to obtain g-C3N4; The g-C3N4 is dispersed in a glucose aqueous solution, reacted at 150-300° C. for 5-12 hours, cooled, centrifuged, washed and dried to obtain a g-C3N4@glu precursor; The g-C3N4@glu precursor is calcined in an Ar atmosphere to obtain a nitrogen-carbon carrier.

3. The core-shell Pt-based hydrogen oxidation catalyst according to claim 2, characterized in that: The temperature of urea calcination is 300-800°C and the time is 3-10h; The calcination temperature of the g-C3N4@glu precursor is 500-1200°C and the time is 3-12h.

4. The core-shell Pt-based hydrogen oxidation catalyst according to claim 2, characterized in that: The mass ratio of g-C3N4 and glucose is (0.5~1):

3.

5. The preparation method according to claim 1, characterized in that: The atomic layer deposition sequence in step A) is: exposing a metal platinum precursor; removing a metal platinum precursor; exposing an oxidizing substance; removing an oxidizing substance; The atomic layer deposition sequence in step B) is: exposing the metal ruthenium precursor; removing the metal ruthenium precursor; exposing the oxidizing substance; removing the oxidizing substance; exposing the reducing substance; removing the reducing substance.

6. The preparation method according to claim 5, characterized in that: The reaction temperature in step A) is 120-300°C; The time sequence of atomic layer deposition is as follows: exposure time of the metal platinum precursor is 100 to 500 s; removal time of the metal platinum precursor is 100 to 500 s; exposure time of the oxidizing substance is 300 to 1000 s; removal time of the oxidizing substance is 100 to 500 s.

7. The preparation method according to claim 5, characterized in that: The reaction temperature in step B) is 120-300°C; The time sequence of atomic layer deposition is as follows: exposure time of metal ruthenium precursor is 100 to 500 s; removal time of metal ruthenium precursor is 100 to 500 s; exposure time of oxidizing substance is 300 to 1000 s; removal time of oxidizing substance is 100 to 500 s; exposure time of reducing substance is 300 to 1000 s; removal time of reducing substance is 100 to 500 s.

8. The preparation method according to claim 1, characterized in that: The reduction temperature in the pretreatment in step A) is 200-800° C. and the time is 0.5-5 h.

9. The preparation method according to claim 1, characterized in that: The core-shell Pt-based hydrogen oxidation catalyst comprises a nitrogen-carbon carrier; and a core-shell metal supported on the nitrogen-carbon support; The core-shell metal has metal platinum as the core and metal ruthenium as the shell.

10. The preparation method according to claim 9, characterized in that: The loading amount of metal platinum in the core-shell type Pt-based hydrogen oxidation catalyst is 0.5-2 wt %, and the loading amount of metal ruthenium is 0.2-3 wt %.

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