A core-shell structure catalyst and its preparation method and application

Abstract

The present invention relates to the field of electrocatalytic water splitting technology, and in particular to a core-shell catalyst, its preparation method, and its application. The present invention provides a core-shell catalyst comprising nitrogen-doped Ru2P and Ru; the nitrogen-doped Ru2P serves as a shell, the Ru serves as a core, and the Ru2P and Ru form a heterojunction. This core-shell catalyst exhibits significantly superior catalytic performance to existing Ru-based catalysts and excellent HER stability.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalytic water decomposition, and in particular to a core-shell structure catalyst and a preparation method and application thereof. Background Art

[0002] Due to the increasingly serious problems of resource depletion and environmental degradation, the development and utilization of clean and renewable energy are urgent. Notably, the electrocatalytic hydrogen evolution reaction (HER), which has the characteristics of zero carbon emissions, is a key pathway for hydrogen production. Among them, precious metal-based catalysts (especially Pt) have shown outstanding advantages in HER due to their ultra-high intrinsic activity. However, the high cost and poor stability of precious metals have severely restricted their industrial production and application. Therefore, reducing costs and improving durability are the focus of precious metal-based catalyst research. It is worth mentioning that Ru is much cheaper than precious metals such as Pt, but it has a hydrogen binding ability comparable to Pt, which has led to Ru being considered an efficient platinum alternative. Ruthenium (Ru) is theoretically considered to be a feasible alkaline hydrogen evolution reaction (HER) electrocatalyst due to its rapid water dissociation kinetics. However, its strong affinity for adsorbed hydroxyl groups (OHad) blocks the active sites, resulting in unsatisfactory performance in actual HER processes. Summary of the Invention

[0003] The object of the present invention is to provide a core-shell structure catalyst and its preparation method and application, wherein the catalytic performance of the core-shell structure catalyst is significantly better than that of the existing Ru-based catalyst and the core-shell structure catalyst has excellent HER stability.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a core-shell structure catalyst comprising nitrogen-doped Ru2P and Ru;

[0006] The nitrogen-doped Ru2P is a shell, and the Ru is a core;

[0007] A heterojunction is formed between the Ru2P and Ru.

[0008] Preferably, the mass ratio of the nitrogen-doped Ru2P to Ru is 1:(3-6).

[0009] Preferably, the nitrogen doping amount in the nitrogen-doped Ru2P is 0 to 15 wt% and is not 0.

[0010] Preferably, the particle size of the core-shell structure catalyst is 100 to 110 nm;

[0011] The shell thickness of the core-shell structure catalyst is 0-10 nm and is not 0.

[0012] The present invention also provides a method for preparing the core-shell structure catalyst described in the above technical solution, comprising the following steps:

[0013] After mixing a soluble ruthenium salt, a surfactant and water, the mixture is heated to obtain Ru@ surfactant;

[0014] After sintering the Ru@ surfactant, the Ru@ surfactant is immediately mixed with ammonia water for nitrogen doping to obtain N-RuO2;

[0015] Mixing the N-RuO2 and the phosphating agent and calcining to obtain the core-shell structure catalyst;

[0016] The nitrogen doping time is 2 to 5 hours, and the sintering temperature is 350 to 500°C.

[0017] Preferably, the surfactant comprises polyallylamine hydrochloride and / or sodium dodecylbenzenesulfonate;

[0018] The phosphating agent includes sodium hypophosphite and / or ammonium phosphate;

[0019] The soluble ruthenium salt includes ruthenium chloride and / or ruthenium nitrate.

[0020] Preferably, the mass ratio of the soluble ruthenium salt to the surfactant is (8-8.23):(8-8.2);

[0021] The temperature of the heating treatment is 90-100° C., the time is 0-6 hours, and is not 0.

[0022] Preferably, the sintering time is 0 to 6 hours, and is not 0;

[0023] The mass concentration of the ammonia water is 25-28%.

[0024] Preferably, the mass ratio of the N-RuO2 to the phosphating agent is 1:(10-50);

[0025] The calcination temperature is 350-550° C., and the calcination time is 1-3 hours.

[0026] The present invention also provides the use of the core-shell structure catalyst described in the above technical solution or the core-shell structure catalyst prepared by the preparation method described in the above technical solution in electrocatalytic water decomposition and hydrogen evolution.

[0027] The present invention provides a core-shell structure catalyst, comprising nitrogen-doped Ru2P and Ru; the nitrogen-doped Ru2P is a shell, the Ru is a core; and a heterojunction is formed between the Ru2P and Ru. In the core-shell structure catalyst of the present invention, Ru acts as a hydrophilic material to accelerate the adsorption of H2O, and Ru2P acts as the main active center to accelerate the dissociation of water, while N doping can optimize the structure of Ru2P and cause it to exhibit a high metal-like conductivity. According to the description of the embodiment, the core-shell structure catalyst of the present invention only requires an ultra-low voltage of 154mV to generate 1A·cm in the alkaline HER process. -2 The industrial-level current density is 0.56 times that of the commercial Pt / C catalyst. -2 N-Ru2P@Ru exhibits an ultra-low overpotential of 9 mV, which is much better than the reported advanced Ru-based catalysts (at a current density of 10 mA cm -2 When the overpotential of Ru2P@Ru / CNT is 23 mV (Chin. J. Catal., 2022, 43, 1148-1155); the overpotential of RuCo alloy is 10 mV (Angew. Chem. Int. Ed., 2022, 61, e202113664); and the overpotential of Ru / C is 30 mV (Energy Environ. Mater., 2022, e12418.). At the same time, it also exhibits excellent HER stability (80 h).

[0028] The present invention also provides a method for preparing the core-shell catalyst described in the above technical solution, comprising the following steps: mixing a soluble ruthenium salt, a surfactant, and water, and then heating to obtain a Ru@ surfactant; sintering the Ru@ surfactant and immediately mixing it with ammonia for nitrogen doping to obtain N-RuO2; and mixing the N-RuO2 with a phosphating agent and calcining it to obtain the core-shell catalyst. This method innovatively utilizes residual heat from sintering to accelerate the volatilization of ammonia during quenching and controllably dope nitrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 (a) XRD pattern, (b) SEM pattern, (c) TEM pattern and (d) HTEM pattern of the catalyst described in Example 1;

[0030] Figure 2 This is the XPS graph of the catalyst described in Example 1;

[0031] Figure 3 Polarization curve of the N-Ru2P@Ru catalyst obtained in Example 1 under saturated nitrogen (a), comparison diagram at different current densities (b), and IT test diagram of N-Ru2P@Ru (c);

[0032] Figure 4 is a SEM image of the catalyst described in Example 2;

[0033] Figure 5 is a SEM image of the catalyst described in Comparative Example 1;

[0034] Figure 6 is a SEM image of the catalyst described in Comparative Example 2;

[0035] Figure 7 This is an XPS comparison chart of the catalysts described in Examples 1 and 2 and Comparative Examples 1 and 2;

[0036] Figure 8 The figure shows the contents of Ru, P and N elements in the catalysts of Examples 1 and 2 and Comparative Examples 1 and 2;

[0037] Figure 9 is a SEM image of the catalyst described in Example 3;

[0038] Figure 10 is a SEM image of the catalyst described in Comparative Example 3;

[0039] Figure 11 The XRD patterns of the catalysts of Examples 1 and 3 and Comparative Example 3 are shown;

[0040] Figure 12 Polarization curves of the catalysts obtained in Examples 1 and 2 and Comparative Examples 1 and 2;

[0041] Figure 13 CV curves (ad) of the catalysts obtained in Examples 1-2 and Comparative Examples 1-2 in 1.0M KOH electrolyte, C dl Figure (e);

[0042] Figure 14 Polarization curves of the catalysts obtained in Examples 1 and 3 and Comparative Example 3.

[0043] Figure 15 CV curves (ac) of the catalysts obtained in Examples 1 and 3 and Comparative Example 3 in 1.0 M KOH electrolyte, C dl Figure (d). DETAILED DESCRIPTION

[0044] The present invention provides a core-shell structure catalyst comprising nitrogen-doped Ru2P and Ru;

[0045] The nitrogen-doped Ru2P is a shell, and the Ru is a core;

[0046] A heterojunction is formed between the Ru2P and Ru.

[0047] In the present invention, the core-shell catalyst is preferably a nanosphere; the particle size of the core-shell catalyst is preferably 100-110 nm; the shell thickness of the core-shell catalyst is preferably 0-10 nm, and is not 0, more preferably 10 nm.

[0048] In the present invention, the mass ratio of the nitrogen-doped Ru2P to Ru is preferably 1:(3-6), more preferably 1:(4-5.5), and most preferably 1:5.

[0049] In the present invention, the nitrogen doping amount in the nitrogen-doped Ru2P is preferably 0-15 wt%, and is not 0, more preferably 2-10 wt%, and most preferably 2.42 wt%.

[0050] The present invention also provides a method for preparing the core-shell structure catalyst described in the above technical solution, comprising the following steps:

[0051] After mixing a soluble ruthenium salt, a surfactant and water, the mixture is heated to obtain Ru@ surfactant;

[0052] After sintering the Ru@ surfactant, the Ru@ surfactant is immediately mixed with ammonia water for nitrogen doping to obtain N-RuO2;

[0053] Mixing the N-RuO2 and the phosphating agent and calcining to obtain the core-shell structure catalyst;

[0054] The nitrogen doping time is 2 to 5 hours, and the sintering temperature is 350 to 500°C.

[0055] In the present invention, unless otherwise specified, all preparation raw materials are commercially available products well known to those skilled in the art.

[0056] The present invention mixes a soluble ruthenium salt, a surfactant and water, and then performs a heating treatment to obtain a Ru@ surfactant.

[0057] In the present invention, the soluble ruthenium salt preferably includes ruthenium chloride and / or ruthenium nitrate; the ruthenium chloride is preferably RuCl2·3H2O; when the soluble ruthenium salt is ruthenium chloride and ruthenium nitrate, the present invention does not have any special restrictions on the ratio of the ruthenium chloride and ruthenium nitrate, and they can be mixed in any ratio.

[0058] In the present invention, the surfactant preferably includes one or more of polyallylamine hydrochloride and / or sodium dodecylbenzenesulfonate. When the surfactant is polyallylamine hydrochloride and sodium dodecylbenzenesulfonate, the present invention has no special restrictions on the ratio of the polyallylamine hydrochloride and sodium dodecylbenzenesulfonate, and they can be mixed in any ratio.

[0059] In the present invention, the mass ratio of the soluble ruthenium salt to the surfactant is preferably (8-8.23):(8-8.2), more preferably 8.23:(8-8.15), and most preferably 8.23:8.

[0060] In the present invention, the volume ratio of the mass of the soluble ruthenium salt to water is preferably (8-8.23) mg:(3-4) mL, and more preferably 8.23 ​​mg:3 mL.

[0061] In the present invention, the mixing is preferably performed by mixing a soluble ruthenium salt with water, then adding a surfactant, and ultrasonicating. In the present invention, the mixing of the soluble ruthenium salt and water is preferably performed by mixing the soluble ruthenium salt with a portion of the water, then adding the remaining water; the volume ratio of the portion of water to the remaining water is preferably 1:2. In the present invention, the ultrasonication time is preferably 5 to 15 minutes, more preferably 8 to 12 minutes, and most preferably 10 minutes. In the present invention, the mixing is preferably performed in a sealed pressure-resistant bottle.

[0062] In the present invention, the temperature of the heat treatment is preferably 90-100°C, more preferably 93-97°C, and most preferably 95°C; the time is preferably 0-6 hours, and not 0 hours, more preferably 2-6 hours, and most preferably 4 hours. In the present invention, the heat treatment is preferably carried out under stirring conditions. The present invention does not have any particular limitation on the stirring process, and a process well known to those skilled in the art can be used.

[0063] After the heating treatment is completed, the present invention further preferably includes evaporating the solvent. The temperature of the evaporating solvent is preferably 110° C. The present invention does not have any special limitation on the time of evaporating the solvent. The time familiar to those skilled in the art can be used to ensure that the solvent is completely evaporated.

[0064] After obtaining the Ru@ surfactant, the present invention sintered the Ru@ surfactant and then immediately mixed it with ammonia water to perform nitrogen doping to obtain N-RuO2.

[0065] In the present invention, the sintering temperature is preferably 350-500°C, more preferably 380-480°C, and most preferably 450°C; the sintering time is preferably 0-6h, and not 0, more preferably 2-6h, and most preferably 2h.

[0066] In the present invention, the mass concentration of the ammonia water is preferably 25-28%, more preferably 26-27%.

[0067] In the present invention, the mixing with ammonia water is preferably carried out by mixing the sintered material with ammonia water when the material is in a high temperature state.

[0068] In the present invention, the nitrogen doping is preferably performed under sealed conditions, and the nitrogen doping process is preferably performed without additional heating, and the heat provided by the high temperature state of the material itself after the sintering treatment is used to volatilize the ammonia water.

[0069] In the present invention, the nitrogen doping time is preferably 2 to 5 hours, more preferably 4 hours.

[0070] After the nitrogen doping is completed, the present invention further preferably includes vacuum drying. The present invention does not have any special limitation on the vacuum drying process, and the process well known to those skilled in the art can be used.

[0071] After obtaining N-RuO2, the present invention mixes the N-RuO2 with a phosphating agent and calcines the mixture to obtain the core-shell structure catalyst.

[0072] In the present invention, the phosphating agent preferably includes sodium phosphate and / or ammonium phosphate; the sodium phosphate is preferably anhydrous sodium phosphate; when the phosphating agent is sodium phosphate and ammonium phosphate, the present invention has no special limitation on the ratio of sodium phosphate and ammonium phosphate, and they can be mixed in any ratio.

[0073] In the present invention, the mass ratio of N-RuO2 to the phosphating agent is preferably 1:(10-50), more preferably 1:(20-40), and most preferably 1:30.

[0074] In the present invention, the calcination temperature is preferably 350-550° C., more preferably 380-520° C., most preferably 390-410° C.; the calcination time is preferably 1-3 h, more preferably 1.5-2.5 h, most preferably 2 h.

[0075] The present invention also provides the use of the core-shell catalyst described in the above technical solution or the core-shell catalyst prepared by the preparation method described in the above technical solution in the electrocatalytic decomposition of water for hydrogen evolution. The present invention does not impose any particular limitations on the method of application, and methods well known to those skilled in the art can be used.

[0076] The core-shell structure catalyst provided by the present invention, its preparation method and application are described in detail below with reference to the examples, but they should not be construed as limiting the scope of protection of the present invention.

[0077] Example 1

[0078] Preparation of Ru@PAH:

[0079] Add 8.29 mg of RuCl2·3H2O to 1 mL of water and mix well (concentration is 40 mM). Then add 2 mL of water and add the resulting mixture to a 15 mL pressure bottle.

[0080] 8 mg of polyallylamine hydrochloride dispersion was added to the mixture, sealed, and ultrasonicated for 10 minutes to obtain a brown solution;

[0081] The brown solution was heated from room temperature to 95°C, then kept under magnetic stirring for 4 hours, and then heated to 110°C and evaporated completely to obtain a green powder (Ru@PAH);

[0082] Preparation of N-RuO2:

[0083] The green powder was placed in a crucible and placed in a muffle furnace, heated to 450°C and maintained for 2 hours. The crucible was taken out at the end of the reaction and immediately placed in a reactor containing 2 mL of 26% ammonia water, covered with a lid, and maintained for 4 hours. The obtained sample was placed in a vacuum drying oven overnight to obtain the N-RuO2;

[0084] Preparation of N-Ru2P@Ru:

[0085] 40 mg of the N-RuO2 and 1200 mg of anhydrous sodium hypophosphite were simultaneously placed in a tube furnace, and the temperature was raised to 450° C. and maintained for 2 hours to obtain the catalyst (N-Ru2P@Ru, wherein the nitrogen doping amount in N-Ru2P was 2.42%, and the mass ratio of N-Ru2P to Ru was 1:4);

[0086] Figure 1 The XRD pattern (a), SEM pattern (b), TEM pattern (c) and HTEM pattern (d) of the catalyst show that the catalyst is composed of two phases, Ru2P and Ru, as shown in the XRD pattern; the average particle size of the catalyst is 100 to 110 nm, as shown in the SEM pattern; and the TEM and HTEM patterns show that the catalyst has nanospheres with a core-shell structure and a heterogeneous interface.

[0087] Figure 2 is the XPS graph of the catalyst, Figure 2 It can be seen that there are two groups of peaks in the XPS spectrum of Ru3pXPS. The peak at 484.4eV and the peak at 462.1eV belong to Ru-P species, while the peak at 484.2eV and the peak at 462.1eV belong to Ru 0 In addition, the XPS spectrum of the N-Ru peak shows that the peak at 401.2 eV is the N-Ru peak (indicating nitrogen doping). The peaks at 129.1 eV and 129.9 eV in the P2p spectrum of N-Ru2P@Ru belong to the P-Ru species, proving the formation of Ru2P, while the peak at 133.5 eV belongs to the PO species.

[0088] Preparation of working electrode

[0089] To prepare the working electrode, the catalyst was dispersed in 5 wt% Nafion and ultrasonicated for 10 min until the mixture was uniform. 200 μL of the obtained mixed solution was dropped onto an area of ​​1 cm 2 The samples were placed on carbon paper, dried at room temperature, and then electrochemically tested in 0.1 M KOH solution.

[0090] Test results

[0091] The test was conducted in the voltage range of -1Vvs.RHE to -1.6Vvs.RHE. Figure 3 Polarization curve of N-Ru2P@Ru catalyst obtained in Example 1 under saturated nitrogen (a), comparison diagram at different current densities (b), IT test diagram of N-Ru2P@Ru (c); Figure 3 It can be seen that the N-Ru2P@Ru catalyst only requires an ultra-low voltage of 154 mV to generate 1 A·cm in the alkaline HER process. -2 The industrial-level current density is 0.56 times that of the commercial Pt / C catalyst; secondly, at a current density of 10 mA cm -2 N-Ru2P@Ru exhibits an ultra-low overpotential of 9 mV, which is much better than the reported advanced Ru-based catalysts (at a current density of 10 mA cm -2 When the overpotential of Ru2P@Ru / CNT is 23 mV (Chin. J. Catal., 2022, 43, 1148-1155); the overpotential of RuCo alloy is 10 mV (Angew. Chem. Int. Ed., 2022, 61, e202113664); and the overpotential of Ru / C is 30 mV (Energy Environ. Mater., 2022, e12418.). It also exhibits excellent HER stability (80 h).

[0092] Example 2

[0093] Preparation of Ru@PAH:

[0094] Add 8.29 mg of RuCl2·3H2O to 1 mL of water and mix well (concentration is 40 mM). Then add 2 mL of water and add the resulting mixture to a 15 mL pressure bottle.

[0095] 8 mg of polyallylamine hydrochloride dispersion was added to the mixture, sealed, and ultrasonicated for 10 minutes to obtain a brown solution;

[0096] The brown solution was heated from room temperature to 95°C, then kept under magnetic stirring for 4 hours, and then heated to 110°C and evaporated completely to obtain a green powder (Ru@PAH);

[0097] Preparation of N-RuO2:

[0098] The green powder was placed in a crucible and placed in a muffle furnace, heated to 450°C and maintained for 2 hours. The crucible was taken out at the end of the reaction and immediately placed in a reactor containing 2 mL of 26 wt% ammonia water, covered with a lid, and maintained for 2 hours. The obtained sample was placed in a vacuum drying oven overnight to obtain the N-RuO2;

[0099] Preparation of N-Ru2P@Ru-2:

[0100] 40 mg of the N-RuO2 and 1200 mg of anhydrous sodium hypophosphite were simultaneously placed in a tube furnace, and the temperature was raised to 450° C. and maintained for 2 hours to obtain the catalyst (N-Ru2P@Ru-2, wherein the nitrogen doping amount in N-Ru2P was 0.54 wt %, and the mass ratio of N-Ru2P to Ru was 1:5);

[0101] Figure 4 is the SEM image of the catalyst, Figure 4 It can be seen that the average particle size of the catalyst is 100-110 nm;

[0102] Preparation of working electrode

[0103] To prepare the working electrode, the catalyst was dispersed in 5 wt% Nafion and ultrasonicated for 10 min until the mixture was uniform. 200 μL of the obtained mixed solution was dropped onto an area of ​​1 cm 2 The samples were deposited on carbon paper and dried at room temperature, and then electrochemical tests were performed in 0.1 M KOH solution.

[0104] Comparative Example 1

[0105] Add 8.29 mg of RuCl2·3H2O to 1 mL of water and mix well (concentration is 40 mM). Then add 2 mL of water and add the resulting mixture to a 15 mL pressure bottle.

[0106] 8 mg of polyallylamine hydrochloride dispersion was added to the mixture, sealed, and ultrasonicated for 10 minutes to obtain a brown solution;

[0107] The brown solution was heated from room temperature to 95°C, then kept under magnetic stirring for 4 hours, and then heated to 110°C and evaporated completely to obtain a green powder (Ru@PAH);

[0108] Preparation of RuO2:

[0109] The green powder was placed in a crucible and placed in a muffle furnace, heated to 450° C. and maintained for 2 hours, then cooled to room temperature, and then the obtained sample was placed in a vacuum drying oven overnight to obtain the RuO2;

[0110] Preparation of Ru2P@Ru:

[0111] 40 mg of the RuO2 and 1200 mg of anhydrous sodium hypophosphite were simultaneously placed in a tube furnace, and the temperature was raised to 450° C. and maintained for 2 hours to obtain the catalyst (Ru2P@Ru, wherein the nitrogen doping amount in Ru2P was 0, and the mass ratio of Ru2P to Ru was 1:5);

[0112] Figure 5 is the SEM image of the catalyst, Figure 5 It can be seen that the average particle size of the catalyst is 100-110 nm;

[0113] Preparation of working electrode

[0114] To prepare the working electrode, the catalyst was dispersed in 5 wt% Nafion and ultrasonicated for 10 min until the mixture was uniform. 200 μL of the obtained mixed solution was dropped onto an area of ​​1 cm 2 The samples were deposited on carbon paper and dried at room temperature, and then electrochemical tests were performed in 0.1 M KOH solution.

[0115] Comparative Example 2

[0116] Preparation of Ru@PAH:

[0117] Add 8.29 mg of RuCl2·3H2O to 1 mL of water and mix well (concentration is 40 mM). Then add 2 mL of water and add the resulting mixture to a 15 mL pressure bottle.

[0118] 8 mg of polyallylamine hydrochloride dispersion was added to the mixture, sealed, and ultrasonicated for 10 minutes to obtain a brown solution;

[0119] The brown solution was heated from room temperature to 95°C, then kept under magnetic stirring for 4 hours, and then heated to 110°C and evaporated completely to obtain a green powder (Ru@PAH);

[0120] Preparation of N-RuO2:

[0121] The green powder was placed in a crucible and placed in a muffle furnace, heated to 450°C and maintained for 2 hours. The crucible was taken out at the end of the reaction and immediately placed in a reactor containing 2 mL of 26 wt% ammonia water, covered with a lid, and maintained for 6 hours. The obtained sample was placed in a vacuum drying oven overnight to obtain the N-RuO2;

[0122] Preparation of N-Ru2P@Ru-6:

[0123] 40 mg of the N-RuO2 and 1200 mg of anhydrous sodium hypophosphite were simultaneously placed in a tube furnace, and the temperature was raised to 450° C. and maintained for 2 hours to obtain the catalyst (N-Ru2P@Ru-6, wherein the nitrogen doping amount in N-Ru2P was 9.28 wt %, and the mass ratio of N-Ru2P to Ru was 1:5.5);

[0124] Figure 6 is the SEM image of the catalyst, Figure 6 It can be seen that compared with Examples 1 to 3, the nanospheres of the catalyst are broken to produce fine particles;

[0125] Figure 7 The XPS comparison chart of the catalysts described in Examples 1 and 2 and Comparative Examples 1 and 2 is shown in FIG. Figure 7 It can be seen that compared with the catalyst described in Comparative Example 1, the peaks belonging to the Ru-P species in the catalysts described in Examples 1 and 2 and Comparative Example 2 all showed obvious shifts, and the catalyst described in Example 1 showed the greatest degree of shift; Figure 8 The content of Ru, P and N elements in the catalysts of Examples 1 to 2 and Comparative Examples 1 to 2 is shown; Figure 8 It can be seen that the longer the amination time is, the higher the nitrogen atom doping content is.

[0126] Preparation of working electrode

[0127] To prepare the working electrode, the catalyst was dispersed in 5 wt% Nafion and ultrasonicated for 10 min until the mixture was uniform. 200 μL of the obtained mixed solution was dropped onto an area of ​​1 cm 2 The samples were placed on carbon paper, dried at room temperature, and then electrochemically tested in 0.1 M KOH solution.

[0128] Test results

[0129] The test was conducted in the voltage range of -1Vvs.RHE to -1.6Vvs.RHE. Figure 12 The polarization curves of the catalysts obtained in Examples 1 and 2 and Comparative Examples 1 and 2 are shown in FIG. Figure 12 It can be seen that the catalytic activity of N-Ru2P@Ru-6 is poor, which is mainly due to the long amination time, which causes the nanospheres to break and agglomerate into large pieces, thereby reducing the number of active sites. Figure 13 CV curves (ad) of the catalysts obtained in Examples 1-2 and Comparative Examples 1-2 in 1.0M KOH electrolyte, C dl Figure (e), Figure 13 Comparative Examples 1 and 2 have lower slopes and C dlThis indicates that their electrochemical active area is very small. This phenomenon intuitively reveals that the morphology fragmentation is not conducive to the exposure of active sites, and thus is not conducive to the hydrogen evolution reaction in water electrolysis.

[0130] Example 3

[0131] Preparation of Ru@PAH:

[0132] Add 8.23 ​​mg of RuCl2·3H2O to 1 mL of water and mix well (concentration is 40 mM). Then add 2 mL of water and add the resulting mixture to a 15 mL pressure bottle.

[0133] 8 mg of polyallylamine hydrochloride dispersion was added to the mixture, sealed, and ultrasonicated for 10 minutes to obtain a brown solution;

[0134] The brown solution was heated from room temperature to 95°C, then kept under magnetic stirring for 4 hours, and then heated to 110°C and evaporated completely to obtain a green powder (Ru@PAH);

[0135] Preparation of N-RuO2:

[0136] The green powder was placed in a crucible and placed in a muffle furnace, heated to 450°C and maintained for 2 hours. The crucible was taken out at the end of the reaction and immediately placed in a reactor containing 2 mL of 26 wt% ammonia water, covered with a lid, and maintained for 4 hours. The obtained sample was placed in a vacuum drying oven overnight to obtain the N-RuO2;

[0137] Preparation of N-Ru2P@Ru-350:

[0138] 40 mg of the N-RuO2 and 1200 mg of anhydrous sodium hypophosphite were simultaneously placed in a tube furnace, and the temperature was raised to 350° C. and maintained for 2 hours to obtain the catalyst (N-Ru2P@Ru-350, wherein the nitrogen doping amount in N-Ru2P was 2.52 wt %, and the mass ratio of N-Ru2P to Ru was 1:4.2);

[0139] Figure 9 is the SEM image of the catalyst, Figure 9 It can be seen that the catalyst is in the shape of nanospheres;

[0140] Preparation of working electrode

[0141] To prepare the working electrode, the catalyst was dispersed in 5 wt% Nafion and ultrasonicated for 10 min until the mixture was uniform. 200 μL of the obtained mixed solution was dropped onto an area of ​​1 cm 2 The samples were deposited on carbon paper and dried at room temperature, and then electrochemical tests were performed in 0.1 M KOH solution.

[0142] Comparative Example 3

[0143] Preparation of Ru@PAH:

[0144] Add 8.23 ​​mg of RuCl2·3H2O to 1 mL of water and mix well (concentration is 40 mM). Then add 2 mL of water and add the resulting mixture to a 15 mL pressure bottle.

[0145] 8 mg of polyallylamine hydrochloride dispersion was added to the mixture, sealed, and ultrasonicated for 10 minutes to obtain a brown solution;

[0146] The brown solution was heated from room temperature to 95°C, then kept under magnetic stirring for 4 hours, and then heated to 110°C and evaporated completely to obtain a green powder (Ru@PAH);

[0147] Preparation of N-RuO2:

[0148] The green powder was placed in a crucible and placed in a muffle furnace, heated to 450°C and maintained for 2 hours. The crucible was taken out at the end of the reaction and immediately placed in a reactor containing 2 mL of 25 wt% ammonia water, covered with a lid, and maintained for 4 hours. The obtained sample was placed in a vacuum drying oven overnight to obtain the N-RuO2;

[0149] Preparation of N-Ru2P@Ru-550:

[0150] 40 mg of the N-RuO2 and 1200 mg of anhydrous sodium hypophosphite were simultaneously placed in a tube furnace, and the temperature was raised to 550° C. and maintained for 2 hours to obtain the catalyst (N-Ru2P@Ru-550, wherein the nitrogen doping amount in N-Ru2P was 2.41 wt %, and the mass ratio of N-Ru2P to Ru was 1:3.8);

[0151] Figure 10 is the SEM image of the catalyst, Figure 10 It can be seen that when the phosphating temperature is 550 °C, the nanospheres break up to produce fine particles and reagglomerate into irregular blocks;

[0152] Figure 11 The XRD patterns of the catalysts of Examples 1 and 3 and Comparative Example 3 are shown in FIG. Figure 11 As shown, the catalysts are composed of two phases of Ru2P and Ru;

[0153] Preparation of working electrode

[0154] To prepare the working electrode, the catalyst was dispersed in 5 wt% Nafion and ultrasonicated for 10 min until the mixture was uniform. 200 μL of the obtained mixed solution was dropped onto an area of ​​1 cm 2 The samples were placed on carbon paper, dried at room temperature, and then electrochemically tested in 0.1 M KOH solution.

[0155] Test results

[0156] The test was conducted in the voltage range of -1Vvs.RHE to -1.6Vvs.RHE. Figure 14 The polarization curves of the catalysts obtained in Examples 1 and 3 and Comparative Example 3 are shown in FIG. Figure 14 It can be seen that temperature also affects the activity of the catalyst. Compared with N-Ru2P@Ru, N-Ru2P@Ru-550 has the worst HER activity, reaction kinetics and charge transfer ability. Figure 15 CV curves (ac) of the catalysts obtained in Examples 1 and 3 and Comparative Example 3 in 1.0 M KOH electrolyte, C dl Figure (d) confirms that the irregular morphology is not conducive to the exposure of its HER active site.

[0157] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A core-shell structure catalyst, characterized in that: including nitrogen-doped Ru2P and Ru; The nitrogen-doped Ru2P is a shell, and the Ru is a core; The Ru2P and Ru constitute a heterojunction; The preparation method of the core-shell structure catalyst comprises the following steps: After mixing a soluble ruthenium salt, polyallylamine hydrochloride and water, the mixture is heated to obtain Ru@polyallylamine hydrochloride; After sintering the Ru@polyallylamine hydrochloride, the Ru@polyallylamine hydrochloride is immediately mixed with ammonia water for nitrogen doping to obtain N-RuO2; Mixing the N-RuO2 and the phosphating agent and calcining to obtain the core-shell structure catalyst; The nitrogen doping time is 2-5 hours, and the sintering temperature is 350-500°C; The mass ratio of the soluble ruthenium salt to the polyallylamine hydrochloride is (8-8.23): (8-8.2); The heating temperature is 90-100°C, the time is 0-6h, and is not 0; The sintering time is 0 to 6 hours and is not 0; The mass concentration of the ammonia water is 25-28%; The mass ratio of N-RuO2 to the phosphating agent is 1:(10~50); The calcination temperature is 350-450° C. and the calcination time is 1-3 hours.

2. The core-shell structure catalyst according to claim 1, characterized in that The mass ratio of the nitrogen-doped Ru2P to Ru is 1:(3-6).

3. The core-shell structure catalyst according to claim 2, characterized in that The nitrogen doping amount in the nitrogen-doped Ru2P is 0.54-15 wt%.

4. The core-shell structure catalyst according to claim 1 or 2, characterized in that The particle size of the core-shell catalyst is 100~110nm; The shell thickness of the core-shell structure catalyst is 0-10 nm and is not 0.

5. The method for preparing the core-shell structure catalyst according to any one of claims 1 to 4, characterized in that: The following steps are involved: After mixing a soluble ruthenium salt, polyallylamine hydrochloride and water, the mixture is heated to obtain Ru@polyallylamine hydrochloride; After sintering the Ru@polyallylamine hydrochloride, the Ru@polyallylamine hydrochloride is immediately mixed with ammonia water for nitrogen doping to obtain N-RuO2; Mixing the N-RuO2 and the phosphating agent and calcining to obtain the core-shell structure catalyst; The nitrogen doping time is 2-5 hours, and the sintering temperature is 350-500°C; The mass ratio of the soluble ruthenium salt to the polyallylamine hydrochloride is (8-8.23): (8-8.2); The heating temperature is 90-100°C, the time is 0-6h, and is not 0; The sintering time is 0 to 6 hours and is not 0; The mass concentration of the ammonia water is 25-28%; The mass ratio of N-RuO2 to the phosphating agent is 1:(10~50); The calcination temperature is 350-450° C. and the calcination time is 1-3 hours.

6. The preparation method according to claim 5, wherein The phosphating agent includes sodium hypophosphite and / or ammonium phosphate; The soluble ruthenium salt includes ruthenium chloride and / or ruthenium nitrate.

7. Use of the core-shell structure catalyst according to any one of claims 1 to 4 or the core-shell structure catalyst prepared by the preparation method according to claim 5 or 6 in electrocatalytic water decomposition and hydrogen evolution.

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