A low Ru-loaded PEM water electrolysis catalyst and its preparation method and application

Abstract

The present invention provides a low-Ru-loading PEM electrolyzed water catalyst and a preparation method thereof. A substrate material is placed in a mixed solution of a non-noble metal salt, a ruthenium salt and a platinum salt, and a metal alloy is in-situ electro-deposited on the substrate material by an electrochemical deposition method to obtain a metal alloy precursor; then, through pyrolysis treatment, a low-Ru-loading PEM electrolyzed water catalyst is obtained. The preparation method has a simple process and is easy to control. The incorporation of Pt / Ru is beneficial to regulating the chemical coordination environment and valence state structure of the non-noble metal oxide, and improving the catalytic stability of the catalyst at a high current density. The low-Ru-loading PEM electrolyzed water catalyst prepared by the present invention only requires an ultra-low Ru mass loading (0.05 mg / cm<supgt;2< / supgt;), and can achieve an overpotential of only 143 mV at 10 mA / cm<supgt;2< / supgt>. At a current density of 1.0 A / cm<supgt;2< / supgt> in a PEM electrolytic cell at 1.83 V, it has broad popularization and application prospects in the aspect of electrolyzed water oxygen evolution.

Description

Technical Field

[0001] The present invention belongs to the technical field of precious metal nanocatalytic materials and proton exchange membrane water electrolysis, and specifically relates to a low Ru-loaded PEM water electrolysis catalyst and a preparation method thereof, and also relates to the application of the low Ru-loaded PEM water electrolysis catalyst in high current density acidic water electrolysis oxygen evolution. Background Art

[0002] Electrochemical water splitting driven by renewable solar and wind energy systems is considered a sustainable green hydrogen production method. Proton exchange membrane (PEM) water electrolysis has the advantages of high operating current density, low ohmic loss, high hydrogen production purity, and fast dynamic response speed, and is widely regarded as the most promising hydrogen production technology. However, the oxygen evolution reaction (OER) at the anode of proton exchange membrane water electrolysis (PEMWE) requires efficient noble metal electrocatalysts (IrO2 and RuO2) to accelerate the sluggish four-electron transfer kinetics, and the high mass loading of the anode catalyst (1.5-2.0 mgIr / cm 2 ) requires a large amount of extremely scarce and expensive Ir resources, which limits the large-scale application of PEMWE for hydrogen production. Compared with IrO2, RuO2 has lower cost and higher OER activity, but Ru has poor stability due to its easy dissolution in acidic media and high oxidation voltage conditions.

[0003] Currently available low-loaded ruthenium-based catalysts are only around 10 mA / cm 2 The low current density shows limited stability within tens of hours, which is far from meeting the requirements of industrial-grade PEM water electrolysis. Especially at high current density (≥100mA / cm 2 ), the active metal or carrier undergoes electrochemical corrosion and dissolution, resulting in the collapse of the local structure around Ru, thereby accelerating the over-oxidation of Ru substances and reducing stability. Some existing studies usually use ruthenium oxide powder as raw material, change the local structure through sintering and other treatments, or perform heterometallic doping with ruthenium oxide as the main body. These schemes still use ruthenium oxide as the skeleton and main body, and the ruthenium content is mostly still greater than 20 wt.%, and the Ru-O skeleton structure is not changed, resulting in the stability of the prepared catalyst under high current density still needs to be improved, and the cost reduction is limited.

[0004] Based on this, a low Ru-loaded PEM water electrolysis catalyst and a preparation method thereof are provided to solve the problems of the existing water electrolysis oxygen evolution catalysts, such as high precious metal content, complex preparation process and high cost, poor inherent stability of the catalyst, and inability to meet the needs of long-term operation under high current density. This is a technical problem that needs to be solved urgently. Summary of the invention

[0005] One of the purposes of the present invention is to provide a method for preparing a low Ru-loaded PEM water electrolysis catalyst.

[0006] A second object of the present invention is to provide a low Ru loading PEM water electrolysis catalyst.

[0007] The third object of the present invention is to provide a low Ru loading PEM water electrolysis catalyst for use in high current density acidic water electrolysis oxygen evolution.

[0008] The technical solution adopted by the present invention to achieve one of the purposes is: to provide a method for preparing a low Ru-loaded PEM water electrolysis catalyst, comprising the following steps:

[0009] S1. Dissolve a non-precious metal salt, a ruthenium salt and a platinum salt in water at a molar ratio of the metal elements of (25-50):(1-2):(1-2) to obtain a mixed solution;

[0010] S2, placing a substrate material in the mixed solution, and in-situ electrodepositing a metal alloy on the substrate material by an electrochemical deposition method to obtain a metal alloy precursor; in the electrochemical deposition, the deposition potential is -1.6 to -2.8 V, and the deposition time is 10-30 min;

[0011] S3. Under air atmosphere, the metal alloy precursor is subjected to pyrolysis treatment to obtain a low Ru loading PEM water electrolysis catalyst.

[0012] The overall idea and inventive principle of the present invention are as follows:

[0013] The present invention provides a low Ru loading PEM water electrolysis catalyst, which incorporates trace amounts of Pt and Ru atoms into non-precious metals by electrodeposition alloying, and then forms in-situ doped low Pt / Ru loading non-precious metal oxides in subsequent high temperature pyrolysis. The incorporation of Pt / Ru is conducive to regulating the chemical coordination environment and valence structure of non-precious metal oxides. On the one hand, it is conducive to improving electron transfer, inducing charge redistribution, and thus enhancing catalytic activity; on the other hand, it is conducive to inhibiting the corrosion and dissolution of active metals at high electro-oxidation potentials and strong acidic media, and improving the catalytic stability of the catalyst at high current density. Among them, the doping of Pt can not only optimize the coordination environment of Ru and non-precious metals; and the incorporation of Pt atoms induces electron transfer, greatly alleviates the electrochemical dissolution of Ru and non-precious metal atoms in the acidic OER process, optimizes the combination of oxygen intermediates, and thereby effectively improves the durability of acidic water decomposition at high current density. In addition, compared with other doped metals (including Ir, Rh, Pd), Pt doping is more uniform, which will strengthen electron transfer and thus improve the stability and activity of the catalyst. Preferably, in the mixed solution, the molar ratio of Pt / Ru is 1:1.

[0014] Furthermore, the present invention uses precise electrodeposition technology to control the deposition potential to be -1.6 to -2.8V, the deposition time to be 10-30min, and the metal in the metal salt solution is deposited on the substrate material in the form of an alloy as a precursor, and then pyrolyzed in the air to finally form a low Pt / Ru loading doped cobalt oxide catalyst. In the above-mentioned electrodeposition process, Pt and Ru selectively occupy the metal sites in the non-precious metal oxide, and the electrons on Pt will be transferred to Ru and the non-precious metal, so that it maintains a relatively stable valence state in the electrocatalytic oxygen evolution reaction; Ru selectively occupies the metal sites on the surface of the non-precious metal oxide, and can anchor Ru with the metal oxygen chemical bond structure of the non-precious metal, thereby achieving high electrocatalytic activity and cycle stability. In addition, high water electrolysis performance and stability at a low precious metal loading (5 wt.%) are achieved.

[0015] Furthermore, the non-precious metal in the non-precious metal salt includes one or more combinations of cobalt, manganese, titanium, and nickel. When the non-precious metal is cobalt, the non-precious metal salt is selected from one or more combinations of chloride, nitrate, and acetate of cobalt; when the non-precious metal is manganese or nickel, the non-precious metal salt is selected from one of chloride and nitrate of manganese or nickel; when the non-precious metal is titanium, the non-precious metal salt is selected from chloride of titanium.

[0016] Preferably, the non-precious metal salt uses cobalt salt as the non-precious metal salt. During the electrochemical deposition process, Pt and Ru selectively occupy the octahedral Co site in cobalt tetroxide, and the electrons on Pt are transferred to Ru and Co, keeping the valence state relatively stable in the electrocatalytic oxygen evolution reaction; Ru selectively occupies the surface octahedral site of cobalt tetroxide, and has high electrocatalytic activity and cycle stability.

[0017] Furthermore, in the mixed solution, the concentration of the non-precious metal salt is 0.01-0.5 mol / L, preferably 0.01-0.1 mol / L, and more preferably 0.05 mol / L.

[0018] Furthermore, in the mixed solution, the concentration of ruthenium salt is 0.0004-0.02 mol / L, and the concentration of platinum salt is 0.0004-0.02 mol / L; preferably, the concentrations of both are 0.0004-0.004 mol / L, more preferably 0.002 mol / L.

[0019] Preferably, the ruthenium salt is ruthenium chloride, and the platinum salt is potassium tetrachloroplatinate.

[0020] Furthermore, the mixed solution also includes an additive; the additive is selected from one of ammonium chloride, urea, and ammonium nitrate. The additive can reduce the surface tension of the electrolyte, making it easier for metal ions to diffuse to the surface of the solution, thereby improving the deposition rate and uniformity of the electrodeposition layer.

[0021] In some preferred embodiments, the additive is ammonium chloride, and its concentration in the mixed solution is 0.01-0.5 mol / L, preferably 0.05-0.2 mol / L, and more preferably 0.1 mol / L. Compared with urea solution and ammonium nitrate solution, the catalyst prepared with ammonium chloride as an additive has a lower corresponding overpotential under the same concentration and current density conditions.

[0022] Furthermore, the base material includes one of carbon fiber paper, titanium mesh, and stainless steel mesh.

[0023] Furthermore, the electrochemical deposition technology adopts a three-electrode system; the substrate material is used as the working electrode, the counter electrode is selected from one of platinum sheet, graphite, and stainless steel, and the reference electrode is selected from one of Ag / AgCl and saturated calomel electrode.

[0024] In the electrochemical deposition of step S2 of the present invention, deposition parameters of deposition potential of -1.6 to -2.8 V and deposition time of 10-30 min are used. Studies have shown that when the deposition potential and deposition time are higher or lower than the above range, the activity of the catalyst in electrolyzing water and oxygen evolution will decrease, which is specifically manifested in that a higher voltage is required to achieve the same current density, the stability will decrease and the energy consumption will increase under high voltage, and the performance will also be greatly reduced when used as an electrode in an electrolytic cell.

[0025] Preferably, in the electrochemical deposition, the deposition potential is -2 to -2.8 V, and the deposition time is 10-30 min; more preferably, the deposition potential is -2.4 V, and the deposition time is 15 min.

[0026] Furthermore, in step S3, the temperature of the pyrolysis treatment is 200-400°C, and the time is 3-6 hours; preferably, the temperature of the pyrolysis treatment is 300-400°C.

[0027] Furthermore, the heating rate of the pyrolysis treatment is 2-15°C / min; preferably 4-6°C / min.

[0028] The technical solution adopted by the present invention to achieve the second purpose is: to provide a low Ru loading PEM water electrolysis catalyst prepared by the preparation method according to one of the purposes of the present invention.

[0029] The low Ru loading PEM water electrolysis catalyst prepared by the present invention is a precious metal nanocatalytic material. Precious metal Pt / Ru doped cobalt tetroxide nanosheets are prepared by precise electrodeposition combined with a pyrolysis process. The catalytic material has a two-dimensional porous structure. The catalytic material is mainly composed of non-precious metal oxides, doped with a small amount of ruthenium and platinum, to achieve uniform loading of precious metals Pt / Ru, which helps to expose active precious metals to enhance catalytic activity. In the Pt-Ru-non-precious metal oxide system, the total loading of precious metals Ru and Pt is less than 5 wt. %; relative to the substrate material, the unit area loading of Ru is 0.01-0.5 mg / cm 2 , preferably 0.05 mg / cm 2 .

[0030] The technical solution adopted by the present invention to achieve the third purpose is: to provide an application of the low Ru loading PEM water electrolysis catalyst described in the second purpose of the present invention in high current density acidic water electrolysis oxygen evolution.

[0031] In some preferred embodiments, the low Ru loading PEM water electrolysis catalyst is applied to a current density of 100 mA / cm 2 Under the conditions of electrolysis for 24h, the voltage value increased to 12-51mV, with excellent stability; at 200 mA / cm 2 The current density can be stably operated in the PEM electrolyzer for 200 hours with a voltage fluctuation of less than 15%.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The method for preparing a low Ru-loaded PEM water electrolysis catalyst provided by the present invention uses carbon fiber paper, titanium mesh or stainless steel mesh as a substrate material, and prepares a low noble metal-loaded PEM water electrolysis catalyst with high conductivity and a two-dimensional porous nanosheet structure through electrochemical deposition technology and pyrolysis. The catalyst preparation process is simple and easy to control.

[0034] (2) The preparation method of the low Ru loading PEM water electrolysis catalyst provided by the present invention is to dope trace amounts of Pt and Ru atoms into non-precious metals by electrodeposition alloying, and then form in-situ doped low Pt / Ru loading non-precious metal oxides in the subsequent high temperature pyrolysis. The incorporation of Pt / Ru is conducive to regulating the chemical coordination environment and valence structure of non-precious metal oxides. On the one hand, it is conducive to improving electron transfer, inducing charge redistribution, and thus enhancing catalytic activity; on the other hand, it is conducive to inhibiting the corrosion and dissolution of active metals at high electro-oxidation potentials and strong acidic media, and improving the catalytic stability of the catalyst at high current density.

[0035] (3) The low Ru loading PEM water electrolysis catalyst prepared by the present invention only requires an ultra-low Ru mass loading (0.05 mg / cm 2 ), can drive 1.0 A / cm at 1.83 V 2 The current density is very high, and this low-precious metal-loaded catalyst has great promotion and application prospects in the electrolysis of water for oxygen evolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a SEM image of the low Ru loading PEM water electrolysis catalyst prepared in Example 1 of the present invention;

[0037] Figure 2 is a TEM image of the low Ru loading PEM water electrolysis catalyst prepared in Example 1 of the present invention;

[0038] Figure 3 is an X-ray diffraction pattern of the low Ru loading PEM water electrolysis catalyst prepared in Example 1 of the present invention;

[0039] Figure 4 The figure is a comparison of the low Ru-loaded PEM water electrolysis catalyst prepared in Example 1 of the present invention and the comparative catalyst in acidic water electrolysis oxygen evolution activity; (a) is a linear sweep voltammetric curve of water electrolysis oxygen evolution of different samples in 0.5M sulfuric acid aqueous solution; (b) is a comparison of the water electrolysis activity of the prepared low Ru-loaded PEM water electrolysis catalyst and the RuO2 catalyst in an acidic PEM electrolyzer;

[0040] Figure 5 This is a stability test chart of the low Ru loading PEM water electrolysis catalyst prepared in Example 1 of the present invention in an acidic PEM electrolyzer. DETAILED DESCRIPTION

[0041] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. 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 making creative work are within the scope of protection of the present invention.

[0042] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0043] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0044] Example 1

[0045] This embodiment provides a method for preparing a low-noble metal-loaded PEM water electrolysis catalyst, comprising the following steps:

[0046] Step 1: Cobalt salt CoCl2, ruthenium salt RuCl3•3H2O, platinum salt K2PtCl4 are mixed with additive NH4Cl according to a Co / Ru / Pt molar ratio of 25:1:1 and dissolved in deionized water, and stirred for 30 min to form a mixed solution; in the mixed solution, the concentration of CoCl2 is 0.05 M, the concentration of RuCl3•3H2O is 0.002 M, the concentration of K2PtCl4 is 0.002 M, and the concentration of additive NH4Cl is 0.1 M;

[0047] Step 2: Using carbon fiber paper as the substrate, the substrate material is placed in the mixed solution, and the PtRuCo alloy precursor is prepared by electrodeposition in a three-electrode system; using carbon fiber paper as the working electrode, platinum sheet and Ag / AgCl as the counter electrode and reference electrode, respectively, and electrodepositing at a constant potential of -2.4 V vs. Ag / AgCl for 15 min. After the electrodeposition is completed, wash with alcohol and deionized water for many times. Dry at room temperature to obtain a precursor, recorded as PtRu-Co;

[0048] Step 3: The PtRu-Co precursor prepared above was calcined in air at 350°C at a heating rate of 5°C / min for 6 h. After the pyrolysis reaction was completed, the temperature was cooled to room temperature. The obtained sample was washed with deionized water and ethanol several times and dried at room temperature to finally obtain a low Ru loading PEM water electrolysis catalyst, denoted as PtRu-Co3O4. In the catalyst, the total loading of precious metals Ru and Pt was less than 5 wt. %; relative to the substrate material, the unit area loading of Ru was 0.05 mg / cm 2 .

[0049] Figure 1 is a SEM image of the low Ru loading PEM water electrolysis catalyst prepared in this example; Figure 2 TEM image of the low Ru loading PEM water electrolysis catalyst prepared in this example. Figure 1 and Figure 2 It can be seen that the low-noble metal loading PEM water electrolysis catalyst PtRu-Co3O4 prepared by the present invention has a two-dimensional porous nanosheet structure, which can increase the electrolyte contact area and improve the exposure rate of catalytic active sites. It also has the advantages of being able to reduce resistance, increase electron transfer rate and gas diffusion rate.

[0050] Example 2

[0051] The difference between this embodiment and embodiment 1 is that the feed ratio of the metal salts in step 1 is adjusted so that the feed molar ratio of Co / Ru / Pt is 50:1:2, and the concentrations of the metal salts in the mixed solution are respectively 0.05 M CoCl2, 0.001 M RuCl3•3H2O, and 0.002 M K2PtCl4. The other conditions, steps, and operations remain unchanged to prepare a low Ru loading PEM water electrolysis catalyst Pt2Ru1-Co3O4-50.

[0052] Example 3

[0053] The difference between this embodiment and embodiment 1 is that the feed ratio of the metal salts in step 1 is adjusted so that the feed molar ratio of Co / Ru / Pt is 25:2:1, and the concentrations of the metal salts in the mixed solution are respectively 0.05 M CoCl2, 0.004 M RuCl3•3H2O, and 0.002 M K2PtCl4. The other conditions, steps, and operations remain unchanged to prepare a low Ru loading PEM water electrolysis catalyst Pt1Ru2-Co3O4-25.

[0054] Example 4

[0055] The difference between this embodiment and embodiment 1 is that the feed ratio of the metal salts in step 1 is adjusted so that the feed molar ratio of Co / Ru / Pt is 25:1:2, and the concentrations of the metal salts in the mixed solution are respectively: 0.05 M CoCl2, 0.002 M RuCl3•3H2O, 0.004 M K2PtCl4, and the other conditions, steps and operations remain unchanged to prepare a low Ru loading PEM water electrolysis catalyst Pt2Ru1-Co3O4-25.

[0056] Example 5

[0057] The difference between this embodiment and embodiment 1 is that the feed ratio of the metal salts in step 1 is adjusted so that the feed molar ratio of Co / Ru / Pt is 50:2:1, and the concentrations of the metal salts in the mixed solution are respectively: 0.05 M CoCl2, 0.002 M RuCl3•3H2O, 0.001 M K2PtCl4, and the other conditions, steps and operations remain unchanged to prepare a low Ru loading PEM water electrolysis catalyst Pt1Ru2-Co3O4-50.

[0058] Example 6

[0059] The difference between this embodiment and embodiment 1 is that the feed ratio of the metal salts in step 1 is adjusted so that the feed molar ratio of Co / Ru / Pt is 50:1:1, and the concentrations of the metal salts in the mixed solution are respectively: 0.05 M CoCl2, 0.001 M RuCl3•3H2O, 0.001 M K2PtCl4, and the other conditions, steps and operations remain unchanged to prepare a low Ru loading PEM water electrolysis catalyst Pt1Ru1-Co3O4-50.

[0060] Example 7

[0061] The difference between this embodiment and embodiment 1 is that the deposition potential in the electrochemical deposition of step 2 is adjusted to -1.6 V, and the other conditions, steps and operations remain unchanged to prepare a low Ru loading PEM water electrolysis catalyst PtRu-Co3O4.

[0062] Example 8

[0063] The difference between this embodiment and embodiment 1 is that the deposition potential in the electrochemical deposition of step 2 is adjusted to -2 V, and the other conditions, steps and operations remain unchanged to prepare a low Ru loading PEM water electrolysis catalyst PtRu-Co3O4.

[0064] Example 9

[0065] The difference between this embodiment and embodiment 1 is that the deposition potential in the electrochemical deposition of step 2 is adjusted to -2.8 V, and the other conditions, steps and operations remain unchanged to prepare a low Ru loading PEM water electrolysis catalyst PtRu-Co3O4.

[0066] Example 10

[0067] The difference between this embodiment and embodiment 1 is that the deposition time in the electrochemical deposition of step 2 is adjusted to 10 minutes, and the other conditions, steps and operations remain unchanged to prepare a low Ru loading PEM water electrolysis catalyst PtRu-Co3O4.

[0068] Embodiment 11

[0069] The difference between this embodiment and embodiment 1 is that the deposition time in the electrochemical deposition of step 2 is adjusted to 30 minutes, and the other conditions, steps and operations remain unchanged to prepare a low Ru loading PEM water electrolysis catalyst PtRu-Co3O4.

[0070] Example 12

[0071] The difference between this embodiment and embodiment 1 is that the type of cobalt salt in step 1 is adjusted to cobalt nitrate, and the other conditions, steps and operations remain unchanged to prepare a low Ru loading PEM water electrolysis catalyst PtRu-Co3O4.

[0072] Embodiment 13

[0073] The difference between this embodiment and embodiment 1 is that the type of cobalt salt in step 1 is adjusted to cobalt acetate, and the other conditions, steps and operations remain unchanged to prepare a low Ru loading PEM water electrolysis catalyst PtRu-Co3O4.

[0074] Embodiment 14

[0075] The difference between this embodiment and embodiment 1 is that the non-precious metal salt in step 1 is adjusted, cobalt chloride is replaced by manganese chloride MnCl2, and the other conditions, steps and operations remain unchanged to prepare a low Ru loading PEM water electrolysis catalyst PtRu-MnO X .

[0076] Embodiment 15

[0077] The difference between this embodiment and embodiment 1 is that the non-precious metal salt in step 1 is adjusted, cobalt chloride is replaced by titanium chloride TiCl4, and the other conditions, steps and operations remain unchanged to prepare a low Ru loading PEM water electrolysis catalyst PtRu-TiO X .

[0078] Example 16

[0079] The difference between this embodiment and embodiment 1 is that the non-precious metal salt in step 1 is adjusted, cobalt chloride is replaced by nickel chloride NiCl4, and the other conditions, steps and operations remain unchanged to prepare a low Ru loading PEM water electrolysis catalyst PtRu-NiO X .

[0080] Embodiment 17

[0081] The difference between this embodiment and embodiment 1 is that the conditions of the pyrolysis treatment in step 3 are adjusted to 300°C, 2h, and the other conditions, steps and operations remain unchanged to prepare a low Ru loading PEM water electrolysis catalyst PtRu-Co3O4.

[0082] Embodiment 18

[0083] The difference between this embodiment and embodiment 1 is that the conditions of the pyrolysis treatment in step 3 are adjusted to 400°C, 6h, and the other conditions, steps and operations remain unchanged to prepare a low Ru loading PEM water electrolysis catalyst PtRu-Co3O4.

[0084] Embodiment 19

[0085] The difference between this embodiment and embodiment 1 is that the additive ammonium chloride in step 1 is adjusted to urea, and the other conditions, steps and operations remain unchanged to prepare a low Ru loading PEM water electrolysis catalyst PtRu-Co3O4.

[0086] Embodiment 20

[0087] The difference between this embodiment and embodiment 1 is that the additive ammonium chloride in step 1 is adjusted to ammonium nitrate, and the other conditions, steps and operations remain unchanged to prepare a low Ru loading PEM water electrolysis catalyst PtRu-Co3O4.

[0088] Comparative Example 1

[0089] This comparative example provides a method for preparing a PEM water electrolysis catalyst with a low noble metal loading, except that the metal salt solution used for electrochemical deposition is changed to a concentration of 0.05 M CoCl2, 0.002 M RuCl3•3H2O (the molar ratio of Co / Ru / Pt is 25:1:0) and 0.1 M NH4Cl, and the prepared PEM water electrolysis catalyst with a low noble metal loading is recorded as Ru-Co3O4, and the remaining steps are the same as in Example 1.

[0090] Comparative Example 2

[0091] This embodiment provides a method for preparing a PEM water electrolysis catalyst with a low noble metal loading, except that the metal salt solution used for electrochemical deposition is changed to a concentration of 0.05 M CoCl2, 0.002 M K2PtCl4 (the molar ratio of Co / Ru / Pt is 25:0:1) and 0.1 M NH4Cl, and the prepared PEM water electrolysis catalyst with a low noble metal loading is recorded as Pt-Co3O4, and the remaining steps are the same as in Example 1.

[0092] Performance Testing

[0093] Linear sweep voltammetry was selected, and the electrochemical workstation was used as the power source. A three-electrode system (Ag / AgCl as the reference and platinum sheet as the counter electrode) was used to test the oxygen evolution performance of the catalysts prepared in Example 1, Comparative Examples 1 and 2, as well as the Co3O4 catalyst and the RuO2 catalyst in 0.5M sulfuric acid aqueous solution. The scan rate was 5 mV / S. The test results are shown in Figure 4 As shown in a.

[0094] Depend on Figure 4 It can be seen that compared with Comparative Examples 1 and 2, Co3O4 catalyst and RuO2 catalyst, the PtRu-Co3O4 prepared in Example 1 has a smaller starting potential of 10 mA / cm 2 The overpotential required for the current density is small, and the oxygen evolution catalytic current density is larger at the same potential.

[0095] Furthermore, the stability test was conducted on the catalysts prepared in the above-mentioned embodiments and comparative examples: a constant current method and a two-electrode system were used to record the change in voltage provided by the electrochemical workstation under the condition of maintaining a specific current density of the catalyst.

[0096] The catalyst prepared in Example 1-20 was heated to a current density of 10 mA / cm2 Under these conditions, the corresponding overpotential test results are shown in Table 1 below:

[0097] Table 1

[0098]

[0099] As can be seen from the above table,

[0100] The low Ru loading PEM water electrolysis catalyst prepared in Examples 1-20 of the present invention has a high conductivity at 10 mA / cm 2 Under the current density conditions, they can show good stability. Among them, the content of precious metals and the ratio between the two precious metals have a greater impact on the performance of catalyst electrolysis of water and oxygen evolution; at the same time, different preparation parameters will affect the deposition structure and morphology of the catalyst, and then affect the electrocatalytic water-to-oxygen evolution activity of the catalyst.

[0101] According to the test results of Examples 1-11, it can be seen that the stability can be further improved by optimizing and adjusting the parameters in the preparation method: when the molar ratio of Co / Ru / Pt is controlled to be (25-50): 1:1, the stability is better; when the molar ratio of Co / Ru / Pt is controlled to be 25:1:1, the potential of electrochemical deposition is -2.4V, and the deposition time is 15min, the stability is optimal. For the types of non-precious metals, in addition to cobalt, catalysts with better stability can also be prepared with manganese, titanium or nickel as the main components, but in comparison, cobalt salts, especially cobalt chloride, as non-precious metal salts have the best performance.

[0102] Further, Examples 1-6 and Comparative Examples 1 and 2 were subjected to 10 mA / cm 2 The corresponding overpotential and at 100 mA / cm 2 The test results of the voltage rise value after 24 hours of electrolysis are compared, as shown in Table 2 below.

[0103] Table 2

[0104]

[0105] From Table 2 above, we can see that

[0106] Examples 1-6 at 10 mA / cm 2 The corresponding overpotential is significantly lower than that of the comparative example 2 of single Pt doping, but not significantly different from that of the comparative example 1 of single Ru doping. 2 After 24 hours of electrolysis, the voltage values ​​of Examples 1-6 increased to 12-51 mV, while the voltage values ​​of Comparative Examples 1 and 2 increased to 123 mV and 86 mV, respectively. It can be seen that the stability of the embodiments is significantly improved.

[0107] Furthermore, by comparing the test data of Example 2 (the molar ratio of Co / Ru / Pt is 50:1:2) and Example 6 (the molar ratio of Co / Ru / Pt is 50:1:1), it can be seen that the corresponding performance is better when the doping amount of platinum and ruthenium is controlled at a molar ratio of 1:1, which shows that in the catalyst prepared by the present invention, the ruthenium component plays a role in improving the catalytic activity, while the Pt component plays a role in stabilizing the catalyst. Only when the ratio of platinum, ruthenium and non-precious metals is moderate can it help to further improve the catalytic activity and catalytic stability of the catalyst.

[0108] In summary, the present invention adopts a Pt / Ru dual-doping strategy and controls a suitable feed ratio, which is more conducive to regulating the chemical coordination environment and valence structure of non-precious metal oxides, which is not only conducive to improving electron transfer and inducing charge redistribution, thereby enhancing catalytic activity; it is also conducive to inhibiting the corrosion and dissolution of active metals at high electro-oxidation potentials and strongly acidic media, thereby improving the catalytic stability of the catalyst at high current density, and effectively improving its durability in acidic water decomposition at high current density.

[0109] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a low Ru-loaded PEM water electrolysis catalyst, characterized in that: The following steps are involved: S1. Dissolving a cobalt salt, a ruthenium salt and a platinum salt in water at a molar ratio of the metal elements of 25:(1-2):1 to obtain a mixed solution; the mixed solution contains an additive at a concentration of 0.01-0.5 mol / L, the additive being selected from one of ammonium chloride, urea and ammonium nitrate; S2, placing a substrate material in the mixed solution, and in-situ electrodepositing a metal alloy on the substrate material by an electrochemical deposition method to obtain a metal alloy precursor; in the electrochemical deposition, the deposition potential is -2 to -2.8 V, and the deposition time is 10-30 min; S3, pyrolyzing the metal alloy precursor under air atmosphere to obtain a low Ru loading PEM water electrolysis catalyst; In the low Ru loading PEM water electrolysis catalyst, the total loading of precious metals Ru and Pt is less than 5wt.%; relative to the substrate material, the unit area loading of Ru is 0.05 mg / cm 2 .

2. The preparation method according to claim 1, characterized in that: In the mixed solution, the concentration of the cobalt salt is 0.01-0.5 mol / L.

3. The preparation method according to claim 1, characterized in that: In the mixed solution, the concentration of ruthenium salt is 0.0004-0.02 mol / L, and the concentration of platinum salt is 0.0004-0.02 mol / L.

4. The preparation method according to claim 1, characterized in that: The base material includes one of carbon fiber paper, titanium mesh and stainless steel mesh.

5. The preparation method according to claim 1, characterized in that: The electrochemical deposition technology adopts a three-electrode system; the substrate material is used as the working electrode, the counter electrode is selected from one of platinum sheet, graphite, and stainless steel, and the reference electrode is selected from one of Ag / AgCl or saturated calomel electrode.

6. The preparation method according to claim 1, characterized in that: The temperature of the pyrolysis treatment is 200-400° C. and the time is 3-6 hours.

7. A low Ru loading PEM water electrolysis catalyst, characterized in that: Prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the low Ru loading PEM water electrolysis catalyst according to claim 7 in high current density acidic water electrolysis for oxygen evolution.

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