Electrode material doped with rare earth elements and preparation method and application thereof

Abstract

The invention discloses a rare earth element doped electrode material and a preparation method and application thereof. The preparation method of the electrode material comprises the following steps: (1) dispersing a transition metal salt, a rare earth element salt, a phosphorus source and a conductive additive in water to prepare a mixed solution; (2) constructing an electroplating reaction tank; and (3) voltage is applied to the positive electrode and the negative electrode of the electroplating reaction tank, ions in the electroplating liquid migrate under the action of an electric field and are subjected to an electrodeposition reaction on the negative electrode of the electroplating reaction tank, and transition metal phosphide doped with rare earth elements, namely the electrode material, is deposited on the conductive substrate. The preparation method of the electrode material has the advantages of universality, simple operation and controllable components. The electrode material disclosed by the invention shows excellent activity and a wide application prospect in a reaction for producing hydrogen by electrolyzing water.

Description

Technical Field

[0001] The invention relates to a preparation method of an electrode material doped with rare earth elements and application thereof in a hydrogen production reaction by electrolyzing water, and belongs to the field of catalytic materials. Background Art

[0002] Hydrogen (H2) is a clean, efficient and environmentally friendly energy source and has been widely studied as a possible alternative to traditional fossil fuels. Combining renewable energy power generation technology, the use of electrocatalytic methods to decompose water to produce hydrogen is a sustainable, zero-carbon emission green hydrogen production technology (S. Jiang et al. J. Am. Chem. Soc. 2020, 142, 6461; W. Zhang et al. Ionics. 2024, 30, 1; L. Yang et al. Adv. Funct. Mater. 2020, 30, 1909618). Commercial platinum-based electrodes have excellent hydrogen evolution performance, but their reserves are low and their prices are expensive. Therefore, it is very necessary to develop non-precious metal electrode materials with simple preparation methods, high activity and low cost to replace precious metal electrodes. Studies have shown that transition metal phosphides (TMPs) have a unique composition structure and a catalytic mechanism similar to that of hydrogenase, and show great development potential in electrolytic hydrogen production reactions (S. Yoonetal. Nanomaterials. 2023, 13, 2613; M. Guan et al. Colloids Surf., A. 2023, 671, 131688; E. Shafiee et al. CRPS. 2023, 4, 101747). The use of rare earth metal elements with special 4f electron configurations to dope and modify transition metal phosphides is expected to further improve their hydrogen evolution performance (T. Chen et al. Energy Fuels. 2021, 35, 14169; X. Wu et al. Small Struct. 2022, 4, 2200268). However, there are currently few methods for doping transition metal phosphides with rare earth elements, and the material preparation methods are cumbersome. Rare earth-doped phosphide electrode materials with clear structures, high activity and easy preparation are still to be developed. Summary of the invention

[0003] The present invention provides the following technical solutions:

[0004] A method for preparing an electrode material, the preparation method comprising the following steps:

[0005] (1) dispersing a transition metal salt, a rare earth element salt, a phosphorus source and a conductive additive in water to prepare a mixed solution;

[0006] (2) constructing an electroplating reaction cell: the conductive substrate is the negative electrode, the metal electrode is the sacrificial positive electrode, and the mixed solution of step (1) is the electroplating solution;

[0007] (3) A voltage is applied to the positive electrode and the negative electrode of the electroplating reaction cell. Under the action of the electric field, the ions in the electroplating solution migrate and undergo an electrodeposition reaction on the negative electrode of the electroplating reaction cell, and a transition metal phosphide doped with a rare earth element is deposited on the conductive substrate, which is the electrode material.

[0008] According to an embodiment of the present invention, in step (1), the transition metal of the transition metal salt is at least one of manganese, iron, cobalt, nickel, copper, zinc, and molybdenum; the transition metal salt is at least one of transition metal nitrates, transition metal sulfates, transition metal acetates, transition metal chlorides, transition metal carbonyl salts, and molybdates. Exemplarily, the transition metal salt is cobalt nitrate hexahydrate or nickel acetate hexahydrate, or sodium molybdate.

[0009] According to an embodiment of the present invention, in step (1), the rare earth element of the rare earth element salt is at least one of lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, and ytterbium. Preferably, the rare earth element salt is at least one of a nitrate of a rare earth element, a sulfate of a rare earth element, an acetate of a rare earth element, a chloride of a rare earth element, a carbonyl salt of a rare earth element, and a molybdate of a rare earth element. Exemplarily, the rare earth element salt is cerium nitrate hexahydrate, lanthanum nitrate hexahydrate, or praseodymium nitrate hexahydrate.

[0010] According to an embodiment of the present invention, in step (1), the phosphorus source is at least one of phosphoric acid, sodium phosphate, sodium hypophosphite, potassium phosphate and potassium hypophosphite.

[0011] According to an embodiment of the present invention, in step (1), the conductive additive is at least one of sodium chloride, sodium sulfate, sodium nitrate and sodium citrate.

[0012] According to an embodiment of the present invention, in step (1), the mixed solution includes transition metals and rare earth elements, and the total molar concentration of the transition metals and rare earth elements is 0.001 to 5 mol L -1 , for example, 0.01 mol L -1 , 0.1 mol L -1 , 1 mol L -1 , 2 mol L -1 , 3 mol L -1 , 4 mol L -1 .

[0013] According to an embodiment of the present invention, in step (1), in the mixed solution, the molar ratio of the rare earth element to the transition metal is 1:1000 to 1:1, for example, 1:100, 1:10.

[0014] According to an embodiment of the present invention, in step (1), in the mixed solution, the molar ratio of phosphoric acid in the phosphorus source to the transition metal in the transition metal salt is 1:10 to 10:1-10, for example, 2:1, 1:1, 1:5.

[0015] According to an embodiment of the present invention, in step (2), the material of the conductive substrate is selected from at least one of carbon paper, carbon cloth, carbon foam, nickel mesh, nickel sheet, and nickel foam.

[0016] According to an embodiment of the present invention, in step (2), the parameters of the conductive substrate are as follows: area 0.1 to 1 cm 2 , thickness is 0.1~1cm.

[0017] According to an embodiment of the present invention, in step (2), the material of the sacrificial positive electrode is selected from at least one of manganese, iron, cobalt, nickel, copper, zinc and molybdenum. Preferably, the area of ​​the sacrificial positive electrode is 0.1 to 1 cm 2 , with a thickness of 0.1 to 1 cm. Preferably, the shape of the sacrificial positive electrode is selected from a sheet or a mesh.

[0018] According to an embodiment of the present invention, in step (3), the voltage is applied by an external power source. Preferably, the current density ranges from 0.1 to 1000 mA cm -2 .

[0019] According to an embodiment of the present invention, the conditions of the electrodeposition reaction are: the electrodeposition time is 1 to 300 minutes, and the electrodeposition temperature is controlled at 5 to 80°C.

[0020] According to an embodiment of the present invention, in step (3), the metal phosphide doped with a rare earth element is in-situ grown on a conductive substrate to form an electroplating layer, and the electroplating layer is dense and structurally stable on the surface of the conductive substrate.

[0021] The present invention also provides an electrode material, which is obtained by the above preparation method.

[0022] According to an embodiment of the present invention, the electrode material includes a transition metal phosphide doped with a rare earth element.

[0023] According to an embodiment of the present invention, in the electrode material, the molar ratio of the rare earth element to the transition metal is 1:1000 to 1:1, for example, 1:100 or 1:10.

[0024] According to an exemplary embodiment of the present invention, the electrode material includes cobalt phosphide doped with rare earth elements or cobalt molybdenum phosphide doped with rare earth elements, wherein the rare earth element is selected from at least one of lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, and ytterbium.

[0025] The present invention also provides an electrode, comprising the electrode material and a conductive substrate, wherein the conductive substrate has the meaning as described above.

[0026] The present invention also provides an application of the above electrode material and / or electrode, preferably used in an electrocatalytic water decomposition hydrogen production system, for example, the cathode in the system includes the electrode material and / or electrode, and the cathode catalyzes hydrogen evolution reaction under alkaline conditions.

[0027] The present invention also provides a method for producing hydrogen by electrocatalytic decomposition of water, wherein the catalyst of the method is the above-mentioned electrode material and / or electrode.

[0028] Beneficial Effects

[0029] The present invention has the following advantages:

[0030] 1. The preparation method provided can prepare electrode materials of rare earth element-doped transition metal phosphides. This method has wide universality, easy control of conditions, easy operation, simple electrode preparation process and low cost.

[0031] 2. The element composition, content, and proportion of the prepared rare earth-doped electrode material are easily adjustable, and the coating structure morphology is controllable, and can be adjusted according to the different requirements of the catalytic reaction.

[0032] 3. The prepared rare earth-doped electrode material exhibits excellent catalytic reaction performance and structural stability in the electrocatalytic water decomposition hydrogen production system.

[0033] 4. This type of material has potential application prospects in the field of water electrolysis to produce hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The scanning electron microscope morphology diagram of the rare earth doped electrode material prepared in Example 4 and the original nickel foam conductive substrate.

[0035] Figure 2 This is a comparison diagram of the XRD structures of the rare earth-doped electrode material prepared in Example 4 and the original nickel foam conductive substrate.

[0036] Figure 3 This is the EDX element distribution diagram of the rare earth-doped electrode material prepared in Example 4.

[0037] Figure 4 It is a comparison chart of hydrogen evolution performance of the electrode materials prepared in Example 4 and Comparative Example 2 and an electrode made of commercial platinum carbon.

[0038] Figure 5 4 is a comparison chart of the hydrogen evolution performance of the electrode materials prepared in Examples 4-6.

[0039] Figure 6It is a comparison chart of the hydrogen evolution performance of the electrode materials prepared in Examples 4 and 11-13. DETAILED DESCRIPTION

[0040] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0041] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0042] The electrode materials of Examples 1-14 of the present invention were tested by the following instruments and methods:

[0043] The morphology of the electrode materials of Examples 1-14 was characterized by a scanning electron microscope (SEM), and the structure of the electrode materials prepared in the Examples was characterized by an X-ray diffractometer (XRD);

[0044] The performance of the electrode materials of Examples 1-14 in catalytically decomposing water to produce hydrogen was measured in an electrocatalytic water decomposition system.

[0045] Example 1

[0046] 1. Dissolve 0.05 mol of cobalt nitrate hexahydrate, 0.01 mol of cerium nitrate hexahydrate, 0.06 mol of sodium hypophosphite and 0.006 mol of sodium citrate in 100 mL of ultrapure water by ultrasonication, and stir to disperse uniformly to obtain a mixed solution.

[0047] 2. Use the above mixed solution as the electroplating solution, nickel foam (2×10×10mm) as the negative conductive substrate, molybdenum sheet (0.5×50×10mm) as the sacrificial anode, and connect an external power supply to build an electroplating device.

[0048] 3. At a current density of 200 mA cm -2 , the electroplating is continued for 20 minutes at a temperature of 30°C, the negative electrode is removed after the electroplating is stopped, and after cleaning and drying, a rare earth-doped electrode material is obtained. The electrode material is deposited on the negative electrode conductive substrate, specifically cobalt phosphide doped with the rare earth element Ce.

[0049] Example 2

[0050] 1. Dissolve 0.05 mol of cobalt nitrate hexahydrate, 0.05 mol of sodium molybdate, 0.02 mol of cerium nitrate hexahydrate, 0.06 mol of sodium hypophosphite and 0.006 mol of sodium citrate in 100 mL of ultrapure water by ultrasonication, and stir to disperse uniformly to obtain a mixed solution.

[0051] 2. Use the above mixed solution as the electroplating solution, nickel foam (2×10×10mm) as the negative conductive substrate, molybdenum sheet (0.5×50×10mm) as the sacrificial anode, and connect an external power supply to build an electroplating device.

[0052] 3. At a current density of 200 mA cm -2 , the electroplating is continued for 20 minutes at a temperature of 30°C. After stopping the electroplating, the negative electrode material is removed, and after cleaning and drying, a rare earth-doped electrode material is obtained. The electrode material is deposited on the negative electrode conductive substrate, specifically cobalt molybdenum phosphide doped with the rare earth element Ce.

[0053] Example 3

[0054] 1. Dissolve 0.05 mol nickel acetate hexahydrate, 0.05 mol sodium molybdate, 0.02 mol lanthanum nitrate hexahydrate, 0.06 mol sodium hypophosphite and 0.006 mol sodium citrate in 100 mL ultrapure water by ultrasonic, and stir to disperse evenly to obtain a mixed solution.

[0055] 2. Use the above mixed solution as the electroplating solution, nickel foam (2×10×10mm) as the negative conductive substrate, molybdenum sheet (0.5×50×10mm) as the sacrificial anode, and connect an external power supply to build an electroplating device.

[0056] 3. At a current density of 200 mA cm -2 , the electroplating is continued for 20 minutes at a temperature of 30°C. After stopping the electroplating, the negative electrode material is removed, and after cleaning and drying, a rare earth-doped electrode material is obtained. The electrode material is deposited on the negative electrode conductive substrate, specifically nickel molybdenum phosphide doped with the rare earth element Ce.

[0057] Example 4

[0058] 1. Dissolve 0.02 mol of cobalt nitrate hexahydrate, 0.02 mol of sodium molybdate, 0.001 mol of samarium nitrate hexahydrate, 0.06 mol of sodium hypophosphite and 0.006 mol of sodium citrate in 100 mL of ultrapure water by ultrasonication, and stir to disperse evenly to obtain a mixed solution.

[0059] 2. Use the above mixed solution as the electroplating solution, nickel foam (2×10×10mm) as the negative conductive substrate, molybdenum sheet (0.5×50×10mm) as the sacrificial anode, and connect an external power supply to build an electroplating device.

[0060] 3. At a current density of 300 mA cm -2 , the electroplating is continued for 30 minutes at a temperature of 30°C. After stopping the electroplating, the negative electrode material is removed. After cleaning and drying, the rare earth-doped electrode material is obtained. The electrode material is deposited on the negative electrode conductive substrate, specifically cobalt molybdenum phosphide doped with the rare earth element samarium.

[0061] The scanning electron microscope image of the negative electrode loaded with the electrode material of this embodiment is as follows: Figure 1 As shown in Figure 1, a rough electroplating layer grows on the surface of the prepared electrode compared to the original metal conductive substrate. The structural characterization of the electroplating layer is shown in Figure 1. Figure 2 As shown in Figure 1, XRD results show that the main body of the electrode is a nickel conductive substrate, and the doping of rare earth elements does not cause obvious composition changes, and no praseodymium phosphide is generated. Figure 3 As shown, the elements cobalt, molybdenum, and praseodymium are evenly distributed, further confirming the successful doping of the rare earth element praseodymium.

[0062] Example 5

[0063] 1. Dissolve 0.02 mol of cobalt nitrate hexahydrate, 0.02 mol of sodium molybdate, 0.02 mol of samarium nitrate hexahydrate, 0.06 mol of sodium hypophosphite and 0.006 mol of sodium citrate in 100 mL of ultrapure water by ultrasonication, and stir to disperse evenly to obtain a mixed solution.

[0064] 2. Use the above mixed solution as the electroplating solution, nickel foam (2×10×10mm) as the negative conductive substrate, molybdenum sheet (0.5×50×10mm) as the sacrificial anode, and connect an external power supply to build an electroplating device.

[0065] 3. At a current density of 300 mA cm -2 , the electroplating is continued for 30 minutes at a temperature of 30°C. After stopping the electroplating, the negative electrode material is removed. After cleaning and drying, the rare earth-doped electrode material is obtained. The electrode material is deposited on the negative electrode conductive substrate, specifically cobalt molybdenum phosphide doped with the rare earth element samarium.

[0066] Example 6

[0067] 1. Dissolve 0.02 mol of cobalt nitrate hexahydrate, 0.02 mol of sodium molybdate, 0.0005 mol of samarium nitrate hexahydrate, 0.06 mol of sodium hypophosphite and 0.006 mol of sodium citrate in 100 mL of ultrapure water by ultrasonication, and stir to disperse evenly to obtain a mixed solution.

[0068] 2. Use the above mixed solution as the electroplating solution, nickel foam (2×10×10mm) as the negative conductive substrate, molybdenum sheet (0.5×50×10mm) as the sacrificial anode, and connect an external power supply to build an electroplating device.

[0069] 3. At a current density of 300 mA cm -2 , the electroplating is continued for 30 minutes at a temperature of 30°C. After stopping the electroplating, the negative electrode material is removed. After cleaning and drying, the rare earth-doped electrode material is obtained. The electrode material is deposited on the negative electrode conductive substrate, specifically cobalt molybdenum phosphide doped with the rare earth element samarium.

[0070] The above-mentioned Examples 1-6 are examples of adjusting the types and concentrations of transition metal salts and rare earth element salts in the plating solution, indicating that under the regulation of a single variable, by changing the types and concentrations of transition metal salts and rare earth element salts, electrode materials doped with corresponding rare earth elements can be prepared. It can be seen that the preparation method involved in the present invention can realize electrode materials doped with transition metal phosphides of various rare earth elements, and the hydrogen evolution reaction performance of such materials is verified and explained in the application examples.

[0071] Example 7

[0072] 1. Dissolve 0.02 mol of cobalt nitrate hexahydrate, 0.02 mol of sodium molybdate, 0.005 mol of samarium nitrate hexahydrate, 0.06 mol of sodium hypophosphite and 0.006 mol of sodium citrate in 100 mL of ultrapure water by ultrasonication, and stir to disperse evenly to obtain a mixed solution.

[0073] 2. Use the above mixed solution as the electroplating solution, carbon paper (10×10 mm) as the negative conductive substrate, molybdenum sheet (0.5×50×10 mm) as the sacrificial anode, and connect an external power supply to build an electroplating device.

[0074] 3. At a current density of 200 mA cm -2 , the electroplating is continued for 20 minutes at a temperature of 30°C. After stopping the electroplating, the negative electrode material is removed. After cleaning and drying, the rare earth-doped electrode material is obtained. The electrode material is deposited on the negative electrode conductive substrate, specifically cobalt molybdenum phosphide doped with the rare earth element samarium.

[0075] Example 8

[0076] 1. Dissolve 0.02 mol of cobalt nitrate hexahydrate, 0.02 mol of sodium molybdate, 0.005 mol of samarium nitrate hexahydrate, 0.06 mol of sodium hypophosphite and 0.006 mol of sodium citrate in 100 mL of ultrapure water by ultrasonication, and stir to disperse evenly to obtain a mixed solution.

[0077] 2. Use the above mixed solution as the electroplating solution, nickel foam (1×10×10mm) as the negative conductive substrate, molybdenum sheet (0.5×50×10mm) as the sacrificial anode, and connect an external power supply to build an electroplating device.

[0078] 3. At a current density of 200 mA cm -2 , the electroplating is continued for 20 minutes at a temperature of 30°C. After stopping the electroplating, the negative electrode material is removed. After cleaning and drying, the rare earth-doped electrode material is obtained. The electrode material is deposited on the negative electrode conductive substrate, specifically cobalt molybdenum phosphide doped with the rare earth element samarium.

[0079] Example 9

[0080] 1. Dissolve 0.02 mol of cobalt nitrate hexahydrate, 0.02 mol of sodium molybdate, 0.005 mol of samarium nitrate hexahydrate, 0.06 mol of sodium hypophosphite and 0.006 mol of sodium citrate in 100 mL of ultrapure water by ultrasonication, and stir to disperse evenly to obtain a mixed solution.

[0081] 2. Use the above mixed solution as the electroplating solution, nickel foam (2×10×10mm) as the negative conductive substrate, molybdenum sheet (0.3×50×10mm) as the sacrificial anode, and connect an external power supply to build an electroplating device.

[0082] 3. At a current density of 200 mA cm -2 , the electroplating is continued for 20 minutes at a temperature of 30°C. After stopping the electroplating, the negative electrode material is removed. After cleaning and drying, the rare earth-doped electrode material is obtained. The electrode material is deposited on the negative electrode conductive substrate, specifically cobalt molybdenum phosphide doped with the rare earth element samarium.

[0083] Example 10

[0084] 1. Dissolve 0.02 mol of cobalt nitrate hexahydrate, 0.02 mol of sodium molybdate, 0.005 mol of samarium nitrate hexahydrate, 0.06 mol of sodium hypophosphite and 0.006 mol of sodium citrate in 100 mL of ultrapure water by ultrasonication, and stir to disperse evenly to obtain a mixed solution.

[0085] 2. Use the above mixed solution as the electroplating solution, nickel foam (2×10×10mm) as the negative conductive substrate, nickel sheet (0.5×50×10mm) as the sacrificial anode, and connect an external power supply to build an electroplating device.

[0086] 3. At a current density of 200 mA cm -2 , the electroplating is continued for 20 minutes at a temperature of 30°C. After stopping the electroplating, the negative electrode material is removed. After cleaning and drying, the rare earth-doped electrode material is obtained. The electrode material is deposited on the negative electrode conductive substrate, specifically cobalt molybdenum phosphide doped with the rare earth element samarium.

[0087] The above-mentioned Examples 7-10 are the modulation of the type and morphology of the conductive substrate and the sacrificial electrode in the electroplating device, indicating that under the regulation of a single variable, by changing the morphology and type of the conductive substrate of the negative electrode and the sacrificial electrode material of the positive electrode during the electroplating process, electrode materials doped with rare earth elements can be prepared.

[0088] Embodiment 11

[0089] 1. Dissolve 0.02 mol of cobalt nitrate hexahydrate, 0.02 mol of sodium molybdate, 0.001 mol of samarium nitrate hexahydrate, 0.06 mol of sodium hypophosphite and 0.006 mol of sodium citrate in 100 mL of ultrapure water by ultrasonication, and stir to disperse evenly to obtain a mixed solution.

[0090] 2. Use the above mixed solution as the electroplating solution, nickel foam (2×10×10mm) as the negative conductive substrate, molybdenum sheet (0.3×50×10mm) as the sacrificial anode, and connect an external power supply to build an electroplating device.

[0091] 3. At a current density of 300 mA cm -2 , the electroplating is continued for 10 minutes at a temperature of 30°C. After stopping the electroplating, the negative electrode material is removed. After cleaning and drying, the rare earth-doped electrode material is obtained. The electrode material is deposited on the negative electrode conductive substrate, specifically cobalt molybdenum phosphide doped with the rare earth element samarium.

[0092] Example 12

[0093] 1. Dissolve 0.02 mol of cobalt nitrate hexahydrate, 0.02 mol of sodium molybdate, 0.001 mol of samarium nitrate hexahydrate, 0.06 mol of sodium hypophosphite and 0.006 mol of sodium citrate in 100 mL of ultrapure water by ultrasonication, and stir to disperse evenly to obtain a mixed solution.

[0094] 2. Use the above mixed solution as the electroplating solution, nickel foam (2×10×10mm) as the negative conductive substrate, molybdenum sheet (0.3×50×10mm) as the sacrificial anode, and connect an external power supply to build an electroplating device.

[0095] 3. At a current density of 300 mA cm -2 , the electroplating is continued for 40 minutes at a temperature of 30°C. After stopping the electroplating, the negative electrode material is removed. After cleaning and drying, the rare earth-doped electrode material is obtained. The electrode material is deposited on the negative electrode conductive substrate, specifically cobalt molybdenum phosphide doped with the rare earth element samarium.

[0096] Embodiment 13

[0097] 1. Dissolve 0.02 mol of cobalt nitrate hexahydrate, 0.02 mol of sodium molybdate, 0.001 mol of samarium nitrate hexahydrate, 0.06 mol of sodium hypophosphite and 0.006 mol of sodium citrate in 100 mL of ultrapure water by ultrasonication, and stir to disperse evenly to obtain a mixed solution.

[0098] 2. Use the above mixed solution as the electroplating solution, nickel foam (2×10×10mm) as the negative conductive substrate, molybdenum sheet (0.3×50×10mm) as the sacrificial anode, and connect an external power supply to build an electroplating device.

[0099] 3. At a current density of 200 mA cm -2, the electroplating is continued for 30 minutes at a temperature of 30°C. After stopping the electroplating, the negative electrode material is removed. After cleaning and drying, the rare earth-doped electrode material is obtained. The electrode material is deposited on the negative electrode conductive substrate, specifically cobalt molybdenum phosphide doped with the rare earth element samarium.

[0100] Embodiment 14

[0101] 1. Dissolve 0.02 mol of cobalt nitrate hexahydrate, 0.02 mol of sodium molybdate, 0.005 mol of samarium nitrate hexahydrate, 0.06 mol of sodium hypophosphite and 0.006 mol of sodium citrate in 100 mL of ultrapure water by ultrasonication, and stir to disperse evenly to obtain a mixed solution.

[0102] 2. Use the above mixed solution as the electroplating solution, nickel foam (2×10×10mm) as the negative conductive substrate, molybdenum sheet (0.3×50×10mm) as the sacrificial anode, and connect an external power supply to build an electroplating device.

[0103] 3. At a current density of 200 mA cm -2 , the electroplating is continued for 30 minutes at a temperature of 50°C. After stopping the electroplating, the negative electrode material is removed. After cleaning and drying, the rare earth-doped electrode material is obtained. The electrode material is deposited on the negative electrode conductive substrate, specifically cobalt molybdenum phosphide doped with the rare earth element samarium.

[0104] The above-mentioned Examples 11-14 are examples of modulation of the current density applied during the electroplating process and the continuous electroplating time, indicating that under the regulation of a single variable, by changing the current density, electroplating time and temperature during the electroplating process, the corresponding electrode materials can be prepared, and their hydrogen evolution reaction performance is verified and explained in the following application examples.

[0105] Comparative Example 1

[0106] 1. Dissolve 0.02 mol of cobalt nitrate hexahydrate, 0.06 mol of sodium hypophosphite and 0.006 mol of sodium citrate in 100 mL of ultrapure water by ultrasonication, and stir to disperse evenly to obtain a mixed solution.

[0107] 2. Use the above mixed solution as the electroplating solution, nickel foam (2×10×10mm) as the negative conductive substrate, molybdenum sheet (0.3×50×10mm) as the sacrificial anode, and connect an external power supply to build an electroplating device.

[0108] 3. At a current density of 300 mA cm -2 , the electroplating is continued for 30 minutes at a temperature of 30°C. After stopping the electroplating, the negative electrode material is removed. After cleaning and drying, the electrode material of the single metal phosphide, i.e., cobalt phosphide, is obtained.

[0109] Comparative Example 2

[0110] 1. Dissolve 0.02 mol of cobalt nitrate hexahydrate, 0.02 mol of sodium molybdate, 0.06 mol of sodium hypophosphite and 0.006 mol of sodium citrate in 100 mL of ultrapure water by ultrasonication, and stir to disperse evenly to obtain a mixed solution.

[0111] 2. Use the above mixed solution as the electroplating solution, nickel foam (2×10×10mm) as the negative conductive substrate, molybdenum sheet (0.3×50×10mm) as the sacrificial anode, and connect an external power supply to build an electroplating device.

[0112] 3. At a current density of 300 mA cm -2 , the electroplating is continued for 30 minutes at a temperature of 30°C. After stopping the electroplating, the negative electrode material is removed. After cleaning and drying, the bimetallic phosphide electrode material, i.e., cobalt molybdenum phosphide, is obtained.

[0113] Application Example 1

[0114] The electrode materials obtained in the above Example 4 and Comparative Example 2 are used as cathode catalysts in the water electrolysis system to demonstrate the application potential of rare earth element-doped electrode materials for hydrogen production by electrolysis:

[0115] 1. Test system construction: The test device is a three-electrode system, the reference electrode is Hg / HgO (1M KOH solution), the counter electrode is a carbon rod, the working electrode is the electrode materials of Example 4 and Comparative Example 2, and the electrolyte is a 1M KOH solution. A 50mL single-cell electrolytic cell is used during the test.

[0116] 2. Catalytic performance evaluation method: The temperature of the electrolytic cell is maintained at room temperature, and the hydrogen evolution performance of the rare earth doped electrode material is evaluated by polarization curves, and the current density of the electrode material with and without rare earth element doping at the same potential is compared.

[0117] The commercial platinum carbon drop was coated on the conductive substrate nickel foam (2×10×10mm) as the control sample, and the test system was built according to the three-electrode system in step 1 above, and the working electrode was replaced with the control sample, and the catalytic performance was evaluated according to step 2. The specific test results are as follows Figure 4 shown.

[0118] By comparison, it can be seen that the hydrogen evolution performance of the electrode material doped with rare earth elements is higher than that of the electrode material not doped with rare earth elements and the control sample, which proves that the preparation of electrode materials doped with rare earth elements by electroplating is beneficial to improving the catalytic performance of cathode electrode materials for electrolysis of water, and the electrode material prepared by the present invention has better catalytic hydrogen evolution performance than commercial platinum carbon.

[0119] When the electrode materials doped with Ce in Examples 1-3 are used as cathode catalysts in a water electrolysis system, the activity of hydrogen production by electrolysis is substantially equivalent to that of the electrode materials in Examples 4-13.

[0120] Application Example 2

[0121] The electrode materials obtained in Examples 4-6 were used as cathode catalysts in a water electrolysis system to demonstrate the application potential of hydrogen production by electrolysis of electrode materials doped with rare earths at different contents:

[0122] 1. Test system construction: The test device is a three-electrode system, the reference electrode is Hg / HgO (1M KOH solution), the counter electrode is a carbon rod, the working electrode is the electrode material obtained in the above embodiment, and the electrolyte is a 1M KOH solution. A 50mL single-cell electrolytic cell is used during the test.

[0123] 2. Catalytic performance evaluation method: The temperature of the electrolytic cell is maintained at room temperature, and the hydrogen evolution performance of the rare earth doped electrode material is evaluated by polarization curve. The specific test results Figure 5 shown.

[0124] By comparison, it can be seen that the hydrogen evolution performance of the electrode material doped with rare earth elements changes with the content of rare earth elements in the electroplating solution. The present invention can adjust the content of the doped rare earth elements by modulating the content of the rare earth element salt in the electroplating solution, thereby further affecting the hydrogen evolution performance of the prepared electrode.

[0125] Application Example 3

[0126] The electrode materials obtained in Example 4 and Examples 11-13 were used as cathode catalysts in the water electrolysis system to demonstrate the application potential of rare earth doped electrode materials with different contents in hydrogen production by electrolysis:

[0127] 1. Test system construction: The test device is a three-electrode system, the reference electrode is Hg / HgO (1M KOH solution), the counter electrode is a carbon rod, the working electrode is the electrode material obtained in the above embodiment, the electrolyte is 1M KOH solution, and a 50mL single-cell electrolytic cell is used during the test.

[0128] 2. Catalytic performance evaluation method: The temperature of the electrolytic cell is maintained at room temperature, and the hydrogen evolution performance of the rare earth doped electrode material is evaluated by polarization curve. The specific test results Figure 6 shown.

[0129] By comparison, it can be seen that the hydrogen evolution performance of the electrode material doped with rare earth elements varies with the electroplating time and current density, and 300 mA cm -2 , 30 minutes of electroplating conditions are conducive to the preparation of more active electrode materials.

[0130] The above is a description of the exemplary embodiments of the present invention. However, the protection scope of the present application is not limited to the above embodiments. Any modification, equivalent substitution, improvement, etc. made by those skilled in the art within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing an electrode material, characterized in that: The preparation method comprises the following steps: (1) dispersing a transition metal salt, a rare earth element salt, a phosphorus source and a conductive additive in water to prepare a mixed solution; (2) constructing an electroplating reaction cell: the conductive substrate is the negative electrode, the metal electrode is the sacrificial positive electrode, and the mixed solution of step (1) is the electroplating solution; (3) A voltage is applied to the positive electrode and the negative electrode of the electroplating reaction cell. Under the action of the electric field, the ions in the electroplating solution migrate and undergo an electrodeposition reaction on the negative electrode of the electroplating reaction cell, and a transition metal phosphide doped with a rare earth element is deposited on the conductive substrate, which is the electrode material.

2. The preparation method according to claim 1, characterized in that: In step (1), the transition metal of the transition metal salt is at least one of manganese, iron, cobalt, nickel, copper, zinc and molybdenum. Preferably, in step (1), the rare earth element of the rare earth element salt is at least one of lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium and ytterbium.

3. The preparation method according to claim 1 or 2, characterized in that: In step (1), the phosphorus source is at least one of phosphoric acid, sodium phosphate, sodium hypophosphite, potassium phosphate and potassium hypophosphite. Preferably, in step (1), the conductive additive is at least one of sodium chloride, sodium sulfate, sodium nitrate and sodium citrate.

4. The preparation method according to any one of claims 1 to 3, characterized in that: In step (1), the mixed solution includes transition metals and rare earth elements, and the total molar concentration of the transition metals and rare earth elements is 0.001 to 5 mol / L -1 . Preferably, in step (1), in the mixed solution, the molar ratio of the rare earth element to the transition metal is 1:1000 to 1:

1. Preferably, in step (1), in the mixed solution, the molar ratio of phosphoric acid in the phosphorus source to the transition metal in the transition metal salt is 1:10 to 10:1-10.

5. The preparation method according to any one of claims 1 to 4, characterized in that: In step (2), the material of the conductive substrate is selected from at least one of carbon paper, carbon cloth, carbon foam, nickel mesh, nickel sheet, and nickel foam. Preferably, in step (2), the parameters of the conductive substrate are as follows: area 0.1 to 1 cm 2 , thickness is 0.1~1cm. Preferably, in step (2), the material of the sacrificial positive electrode is selected from at least one of manganese, iron, cobalt, nickel, copper, zinc and molybdenum.

6. The preparation method according to any one of claims 1 to 5, characterized in that: In step (3), the voltage is applied by an external power source. The current density range is 0.1 to 1000 mA cm -2 . Preferably, the conditions of the electrodeposition reaction are: the electrodeposition time is 1 to 300 minutes, and the electrodeposition temperature is controlled at 5 to 80°C. Preferably, in step (3), the metal phosphide doped with the rare earth element is grown in situ on the conductive substrate to form an electroplating layer, and the electroplating layer is dense and has a stable structure on the surface of the conductive substrate.

7. An electrode material, characterized in that: The electrode material is obtained by the preparation method according to any one of claims 1 to 6.

8. The electrode material according to claim 7, characterized in that The electrode material includes transition metal phosphide doped with rare earth elements. Preferably, in the electrode material, the molar ratio of rare earth elements to transition metals is 1:1000 to 1:

1.

9. An electrode, characterized in that: The electrode comprises the electrode material according to claim 7 or 8 and a conductive substrate.

10. Use of the electrode material according to claim 7 or 8 and / or the electrode according to claim 9 in a system for producing hydrogen by electrocatalytic decomposition of water.

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