Nanosheet FeOOH modified Ni 3 Preparation method of B electrocatalyst and its application in alkaline oxygen evolution

Abstract

The present invention provides a preparation method of a Ni3B electrocatalyst modified with nano-sheet FeOOH and its application in alkaline oxygen evolution. Among them, during the alkaline OER reaction process of Ni3B, part of the boride surface will be transformed into metaborate. Based on the regulation of the redistribution of the surface charge of FeOOH by metaborate, the present invention changes the adsorption characteristics of surface oxygen to solve the problem of the large kinetic barrier of FeOOH. The three-dimensional self-supporting electrocatalyst material (NF / Ni3B / FeOOH) of the present invention can not only promote electron transfer through the modification of electroactive sites, thereby significantly improving the conductivity of the electrocatalyst, but also the metaborate generated during the OER reaction process can effectively optimize the adsorption energy of intermediates and reduce the kinetic barrier during the reaction process, enabling the catalyst to have excellent catalytic activity and catalytic stability under industrial conditions.

Description

Technical Field

[0001] The present invention relates to new materials, and particularly to a preparation method of a Ni 3 B electrocatalyst modified by nano-sheet FeOOH and its application in alkaline oxygen evolution. Background Art

[0002] Hydrogen fuel has the characteristics of high energy density and environmental friendliness, and is one of the most promising energy sources at present. At present, hydrogen is mainly produced from fossil resources through steam reforming processes, which accelerates the consumption of fossil fuels and the emission of carbon dioxide. Considering energy and environmental issues, electrocatalytic water splitting has become a completely renewable, clean and effective hydrogen production technology, with the advantages of producing high-purity hydrogen products and zero carbon emissions, and is of great significance in energy and environmental issues.

[0003] Generally speaking, the overall water splitting includes two half-reactions: the oxygen evolution reaction (OER) at the anode and the hydrogen evolution reaction (HER) at the cathode. Although producing pure H 2 is the main goal of electrocatalytic water splitting, OER has always been one of the bottlenecks of electrocatalytic water splitting technology. OER is a thermodynamically uphill reaction (237 kJmol@1) and there is a kinetic bottleneck due to four electron transfer steps and the formation process of oxygen-oxygen bonds, and a relatively high overpotential is required to overcome the activation barrier to achieve the desired current density. Therefore, the high overpotential of OER in the actual water electrolysis process severely limits the overall efficiency of electrocatalytic water splitting.

[0004] Electrocatalysts are important materials for improving the efficiency of water electrolysis. They improve the overall reaction rate by accelerating the reaction rate of the rate-determining step, thereby improving the catalytic efficiency and solving the problem of low energy utilization rate of the water splitting reaction to a certain extent. At present, advanced catalysts are noble metal Ir / Ru-based oxides. However, although noble metal catalysts have high catalytic activity, they have poor stability, low natural reserves and high prices, and it is difficult to achieve large-scale industrial applications. Therefore, great efforts have been made to develop non-noble metal catalysts with high OER activity, rich reserves, low cost to replace noble metal-based catalysts.

[0005] FeOOH, as a recognized catalytic active phase in the alkaline OER reaction process, has high catalytic activity; at the same time, it is inexpensive and has rich natural reserves. Fe 3+ has too strong adsorption of *OH intermediates, resulting in a large kinetic barrier in the electrocatalytic water decomposition reaction. In addition, FeOOH is a semiconductor material with a relatively wide band gap and only has 2.2×10 at a high potential greater than 400 mV -2The conductivity of mS / cm is limited by its poor conductivity and cannot meet the excellent charge transport ability required for electrocatalytic reactions. In addition, although the reported FeOOH can operate stably for a long time under the conditions of low concentration and small current density (1M KOH, 10mA cm -2 ), its catalytic stability is poor under industrial conditions (30% KOH, 1000mA cm -2 ), and it can only operate stably for about 50h. Summary of the Invention

[0006] To solve the above problems, the present invention provides a preparation method of a nano-sheet FeOOH modified Ni 3 B electrocatalyst and its application in alkaline oxygen evolution. Specifically, during the alkaline OER reaction process of Ni 3 B, part of the boride surface will be transformed into metaborate. Based on the regulation of the redistribution of surface charges of FeOOH by metaborate, the present invention changes the adsorption characteristics of surface oxygen to solve the problem of large kinetic barrier of FeOOH.

[0007] The present invention adopts the following technical scheme: A nano-sheet FeOOH modified Ni 3 B electrocatalyst, where the nano-sheet FeOOH grows vertically on the surface of massive Ni 3 B; by compounding FeOOH with Ni 3 B with metalloid properties, the present invention constructs a three-dimensional self-supporting electrocatalyst material with a heterogeneous interface (NF / Ni 3 B / FeOOH). It can not only promote electron transfer through the modification of electroactive sites, thereby significantly improving the conductivity of the electrocatalyst, but also the metaborate generated during the OER reaction process can effectively optimize the adsorption energy of intermediates, reduce the kinetic barrier during the reaction process, and make the catalyst have excellent catalytic activity and catalytic stability under industrial conditions.

[0008] The present invention also provides a preparation method of the above-mentioned nano-sheet FeOOH modified Ni 3 B electrocatalyst, including:

[0009] (1) Mix boron powder and nickel foam under an Ar 2 atmosphere, heat them to 800°C at a heating rate of 3°C / min, keep the temperature for 30min, wait for cooling to room temperature, wash them, and then dry them in a vacuum drying oven at 60°C for 8h to obtain NF / Ni 3 B;

[0010] (2) Place the previously obtained NF / Ni 3 B in 0.6mol / L FeSO 4 ·7H 2In an aqueous solution, react at 30 °C for 5 min, and the Fe adsorbed on the surface of Ni 3 B will gradually oxidize to FeOOH. After washing, dry in a vacuum drying oven at 60 °C for 8 h to obtain NF / Ni 2+ B / FeOOH. 3 B / FeOOH.

[0011] Furthermore, the pretreatment process of the nickel foam is as follows: ultrasonically treat with acetone and 3 mol / L hydrochloric acid for 10 min respectively, then ultrasonically rinse with deionized water (DI) and ethanol 3 times, ultrasonically treat for 5 min each time, take out, and dry overnight in a vacuum drying oven at 60 °C.

[0012] Furthermore, in step 1, the nickel foam is buried in boron powder. The heat treatment process is realized in a porcelain boat.

[0013] The present invention also provides the application of the above-mentioned Ni modified with nano-sheet FeOOH 3 B electrocatalyst in alkaline oxygen evolution.

[0014] The beneficial effect of the present invention is that the Ni modified with nano-sheet FeOOH prepared by the present invention 3 B electrocatalyst (NF / Ni 3 B / FeOOH) has faster reaction kinetics and a lower reaction barrier, and can thus greatly improve the catalytic activity of the electrocatalyst. The overpotential required to reach a current density of 10 mA / cm 2 is only 230 mV, and it can stably operate at least for 200 h at a current density of 100 mA / cm 2 . Description of the Drawings

[0015] Figure 1 are the Raman and XPS diagrams of the product obtained in Example 1;

[0016] Figure 2 are the SEM images (a) and elemental mapping (b) of NF / Ni 3 B / FeOOH;

[0017] Figure 3 are the stability test result diagrams of NF / Ni 3 B / FeOOH obtained in Example 1 and NF / FeOOH obtained in the comparative example under simulated industrial conditions;

[0018] Figure 4 are the LSV test result diagrams of NF / Ni 3 B / FeOOH obtained in Example 1 and NF / FeOOH obtained in the comparative example under simulated industrial conditions;

[0019] Figure 5NF / Ni obtained in Example 1 3 LSV test result diagrams of B / FeOOH obtained in Example 1 and NF / FeOOH obtained in the comparative example under experimental conditions;

[0020] Figure 6 NF / Ni obtained in Example 1 3 Impedance test result diagrams of B / FeOOH obtained in Example 1 and NF / FeOOH obtained in the comparative example under experimental conditions. Detailed implementation manners

[0021] The present invention will be further described below in conjunction with examples and the accompanying drawings of the specification, but is not limited thereto.

[0022] Example 1

[0023] 1. Cut nickel foam into strips of 1.0 cm × 4.0 cm, ultrasonically clean them with acetone and 3 mol / L hydrochloric acid for 10 min each, then ultrasonically rinse them with deionized water (DI) and ethanol three times, 5 min each time, take them out, and dry them overnight in a vacuum drying oven at 60 °C.

[0024] 2. Weigh 5.0 g of boron powder, put the weighed boron powder into a porcelain boat, then bury a cleaned nickel foam strip into the porcelain boat containing boron powder, and compact the boron powder with a medicine spoon.

[0025] 3. Put the porcelain boat into a tubular furnace, under an Ar 2 atmosphere, heat it to 800 °C at a heating rate of 3 °C / min, keep it heated for 30 min, wait until it cools to room temperature, take out the porcelain boat, and take out the nickel foam, ultrasonically clean it with ethanol three times, and then dry it in a vacuum drying oven at 60 °C for 8 h to obtain NF / Ni 3 B.

[0026] 4. Weigh 18 mmol of FeSO 4 ·7H 2 O and add it to 30 ml of DI, place it on a stirring table and stir for 10 min until the solute is completely dissolved.

[0027] 5. Place the FeSO 4 ·7H 2 O aqueous solution in a water bath at 30 °C, and put NF / Ni 3 B into it and react for 5 min. Then rinse it with DI and ethanol several times, and dry it in a vacuum drying oven at 60 °C for 8 h to obtain NF / Ni 3 B / FeOOH. The Raman and XPS tests of the product are as Figure 1 shown, and it can be seen that in this example, a 3D self-supporting high-performance electrocatalyst with a heterogeneous interface (NF / Ni 3B / FeOOH)

[0028] Figure 2 is NF / Ni 3 The SEM image of B / FeOOH and the element mapping of the corresponding area show that nanosheet-like FeOOH grows vertically on the surface of massive Ni 3 B. This nanosheet-like morphology greatly increases the electrochemical surface area of the catalyst, thereby exposing more catalytic active sites and significantly improving the catalytic performance.

[0029] Comparative Example 1

[0030] 1. Cut the nickel foam into strips of 1.0 cm × 4.0 cm, ultrasonically clean them with acetone and 3 mol / L hydrochloric acid for 10 min each, then ultrasonically rinse them with deionized water (DI) and ethanol 3 times, 5 min each time. Take them out and dry them overnight in a vacuum drying oven at 60 °C.

[0031] 2. Weigh 18 mmol FeSO 4 ·7H 2 O and add it to 30 ml of DI. Place it on a magnetic stirrer and stir for 10 min until the solute is completely dissolved.

[0032] 3. Place the FeSO 4 ·7H 2 O aqueous solution in a water bath at 30 °C, and put the NF into it and react for 5 min. Then rinse it with DI and ethanol several times and dry it in a vacuum drying oven at 60 °C for 8 h to obtain NF / FeOOH.

[0033] The NF / Ni 3 B / FeOOH obtained in Example 1 and the NF / FeOOH obtained in the comparative example were respectively subjected to a stability test under simulated industrial conditions. Specifically: during the test, a three-electrode system was used, that is, NF / Ni 3 B / FeOOH was directly used as the working electrode, the mercury / mercuric oxide electrode was used as the reference electrode, and the carbon rod was used as the counter electrode, with 30% KOH as the electrolyte; the test results are as Figure 3 , from Figure 3 it can be seen that the NF / Ni 3 B / FeOOH obtained in Example 1 maintained its catalytic activity performance above 85% after running for 200 h under industrial conditions (30% KOH, 1000 mA cm -2 ), while the NF / FeOOH obtained in the comparative example showed a sudden decrease in activity after running for 50 h, and the catalytic activity performance was only about 45% of the initial performance. It can be seen that through the composite of Ni 3 B in this application, the stability problem of iron oxyhydroxide in the industrial environment is effectively solved.

[0034] The NF / Ni 3 B / FeOOH obtained in this example and the NF / FeOOH obtained in the comparative example were respectively subjected to LSV tests under the above simulated industrial conditions, and the test results are as Figure 4 shown. It can be seen that the catalytic activity of the NF / Ni 3 B / FeOOH obtained in the example was significantly improved compared with that of the NF / FeOOH obtained in the comparative example.

[0035] The NF / Ni 3 B / FeOOH obtained in this example and the NF / FeOOH obtained in the comparative example were subjected to LSV tests under the conditions of low concentration and small current density (1M KOH, 10mA cm -2 -2). (The test adopted a three-electrode system, and the working electrode was self-supporting NF / Ni 3 B / FeOOH; reference electrode: mercury / mercuric oxide electrode; counter electrode: carbon rod); the test results are as Figure 5 , and it can be seen from Figure 5 that even under the conditions of low concentration and small current, the catalytic activity of the NF / Ni 3 B / FeOOH obtained in the example still maintained an absolute advantage.

[0036] The NF / Ni 3 B / FeOOH obtained in this example and the NF / FeOOH obtained in the comparative example were subjected to impedance tests under the conditions of low concentration and small current density (1M KOH, 10mA cm -2 -2). (The test adopted a three-electrode system, and the working electrode was self-supporting NF / Ni 3 B / FeOOH; reference electrode: mercury / mercuric oxide electrode; counter electrode: carbon rod); the test results are as Figure 6 , and it can be seen from Figure 6 that the impedance of the NF / Ni 3 B / FeOOH in Example 1 was significantly reduced. It can be seen that the heterostructure catalyst based on constructing FeOOH and metalloid Ni 3 B of the present invention can effectively improve the overall conductivity of the catalyst; at the same time, the metaborate formed on the surface of Ni 3 B during the OER reaction process can regulate the redistribution of surface charges of FeOOH and solve the problem of large kinetic barrier of FeOOH.

[0037] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A nano-sheet FeOOH-modified Ni3B electrocatalyst, characterized in that: Nanosheet-like FeOOH grows vertically on the surface of bulk Ni3B. During the alkaline OER reaction of Ni3B, the boride surface will partially transform into metaborate, regulating the redistribution of the surface charge of FeOOH.

2. The method for preparing the nano-sheet FeOOH-modified Ni3B electrocatalyst according to claim 1, characterized in that: The preparation method at least comprises: (1) The boron powder and nickel foam are heated to 800°C at a heating rate of 3°C / min in an Ar2 atmosphere, kept heated for 30 min, cooled to room temperature, washed, and dried in a vacuum drying oven at 60°C for 8 h to obtain NF / Ni3B; (2) The NF / Ni3B obtained above was placed in a 0.6 mol / LFeSO4·7H2O aqueous solution, reacted at 30°C for 5 min, and then washed and dried in a vacuum oven at 60°C for 8 h to obtain NF / Ni3B / FeOOH.

3. The preparation method according to claim 2, characterized in that: The pretreatment process of the nickel foam is as follows: ultrasonically treat with acetone and 3 mol / L hydrochloric acid for 10 min each, then ultrasonically rinse with deionized water (DI) and ethanol for 3 times, ultrasonically treat for 5 min each time, take out, and dry in a vacuum drying oven at 60° C. overnight.

4. The preparation method according to claim 2, characterized in that: Nickel foam is buried in boron powder.

5. The preparation method according to claim 2, characterized in that: The heating in step (1) is carried out in a porcelain boat.

6. Use of the nano-sheet FeOOH-modified Ni3B electrocatalyst as claimed in claim 1 in alkaline oxygen evolution.

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