Iron-rich transition metal selenide electrolyzed water catalyst and preparation method thereof

Abstract

The invention discloses an iron-rich transition metal selenide electrolyzed water catalyst and a preparation method thereof. The iron-rich transition metal selenide electrolyzed water catalyst comprises a carrier and an iron-rich transition metal selenide loaded on the carrier, the method comprises the following steps: ultrasonically cleaning a carrier to remove oil stains and oxides on the surface of the carrier; the preparation method comprises the following steps: adding selenium powder into a mixed solution of water and hydrazine hydrate, carrying out sufficient magnetic stirring and ultrasonic dispersion until uniform mixing so as to obtain a mixed reaction solution, and transferring the mixed reaction solution and a carrier together into a polytetrafluoroethylene reaction kettle to carry out a reaction; and washing and drying the reaction product in sequence to finally prepare the iron-rich transition metal selenide electrolyzed water catalyst. The iron-base-rich transition metal selenide electrolyzed water catalyst is synthesized through a simple one-step hydrothermal method, the cost of needed raw materials is low, the preparation method is simple and easy to operate, the overpotential in the reaction process is reduced, the energy consumption of electrolyzed water is greatly reduced, and the iron-base-rich transition metal selenide electrolyzed water catalyst is suitable for industrial large-scale production.

Description

Technical Field

[0001] The present invention belongs to the field of catalytic technology, and particularly relates to an iron-rich transition metal selenide electrocatalyst for water electrolysis and a preparation method thereof. Background Art

[0002] As a secondary energy source, hydrogen energy is regarded as the ultimate clean energy in the 21st century and has attracted much attention due to its clean, efficient and renewable characteristics. However, the acquisition of hydrogen requires an energy conversion process to extract it from resources such as coal, hydrocarbons or water. For green hydrogen production technologies, water electrolysis is considered the most promising method due to its environmental friendliness and sustainability. Among them, alkaline water electrolysis technology shows great application potential because it can use non-precious metal catalysts and the electrolyzer has a relatively long service life. During the water electrolysis process, the required voltage is mainly determined by the overpotentials of the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. However, the kinetic limitations of the OER reaction and the complexity of its catalyst preparation process seriously hinder the large-scale industrial application of water electrolysis for hydrogen production.

[0003] In the past few decades, transition metal-based materials, especially those rich in nickel, cobalt and iron, have been widely studied as candidate materials for OER catalysts because of their favorable electronic states for binding reaction intermediates. Nevertheless, the most advanced OER catalysts at present are still mainly nickel-based and cobalt-based materials, and iron usually plays a synergistic role. Compared with nickel and cobalt, iron has attracted much attention due to its abundant reserves and significant cost advantages, but the catalytic activity of iron-rich catalysts is often restricted by their poor electrical conductivity, which has become the main bottleneck for performance improvement.

[0004] In recent years, transition metal selenides have shown good application potential due to their semiconductor-like conductive properties and fast charge transfer ability. However, compared with noble metal-based catalysts, there is still a significant gap in their catalytic performance. In addition, most of the studied transition metal selenide catalysts usually only show high activity in the OER or HER reaction and are difficult to efficiently catalyze both reactions simultaneously. In the process of overall water splitting, this limitation requires different catalysts to be designed for the cathode and anode respectively, which not only increases the system complexity but also may lead to cross-contamination between the cathode and anode.

[0005] Therefore, there is an urgent need to design a bifunctional electrocatalyst that can efficiently catalyze both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) simultaneously, which can not only simplify the development of the energy system but also effectively reduce the cost of hydrogen production. In this context, how to modify iron-based transition metal selenide catalysts through effective strategies to optimize their catalytic performance during water electrolysis has become a key problem in the current research field. Summary of the Invention

[0006] In order to overcome the technical difficulties of complex preparation and insufficient catalytic activity of existing iron-rich transition metal selenide water electrolysis catalysts, the present invention provides an iron-rich transition metal selenide water electrolysis catalyst and a preparation method thereof.

[0007] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0008] 1. An iron-rich transition metal selenide water electrolysis catalyst:

[0009] The invention comprises a carrier and an iron-rich transition metal selenide loaded on the carrier.

[0010] The carrier is foamed iron copper, and the iron-rich transition metal selenide is Cu 7.16 Se4, CuFeSe2, Cu 0.74 Fe 0.26 Se 2-x One or more of , wherein x represents the coordination number.

[0011] The content of iron in the carrier is 80-85%, and the content of copper is 15-20%.

[0012] 2. A method for preparing the iron-rich transition metal selenide water electrolysis catalyst comprises the following steps:

[0013] Step S1: First, the carrier is ultrasonically cleaned to remove oil and oxides on the surface of the carrier;

[0014] Step S2: Next, add selenium powder to the mixed solution of water and hydrazine hydrate, fully stir with a magnetic stirrer, and then disperse with an ultrasonic stirrer until uniformly mixed to obtain a mixed reaction solution:

[0015] Step S3: transferring the mixed reaction solution obtained in step S2 and the carrier that has been ultrasonically cleaned to a polytetrafluoroethylene reactor for reaction to generate a product;

[0016] Step S4: The reaction product generated in step S3 is washed and dried in sequence to finally obtain an iron-rich transition metal selenide water electrolysis catalyst.

[0017] The carrier in step S1 is foamed iron copper, and the specific method of ultrasonic cleaning in step S1 is: ultrasonically clean the foamed iron copper using sufficient amounts of acetone, hydrochloric acid, ethanol and deionized water in sequence, with each cleaning solvent cleaning for no less than 10 minutes, and then wipe dry with filter paper.

[0018] The cleaning solvents are specifically acetone, hydrochloric acid, ethanol and deionized water.

[0019] In the step S2, the volume ratio of water to hydrazine hydrate in the mixed solution of water and hydrazine hydrate is 30:1 to 5:1, and the concentration of selenium powder in the mixed reaction solution is 0.01 to 0.75 mmol / mL.

[0020] In the step S3, the reaction temperature in the polytetrafluoroethylene reactor is 80 to 250 °C, and the reaction time is 1 to 60 h.

[0021] The washing method in the step S4 is to wash the reaction product successively with absolute ethanol and deionized water, and the number of washing times with absolute ethanol and deionized water is not less than 5 times; the drying method is to dry the washed reaction product in a blast environment at 40 to 80 °C for not less than 10 hours.

[0022] III. Application of the iron-rich transition metal selenide electrolyzed water catalyst obtained by the above preparation method as a bifunctional electrode in alkaline electrolyzed water for simultaneously and efficiently catalyzing OER and HER reactions.

[0023] The present invention successfully synthesizes a bifunctional selenide electrolyzed water catalyst through a simple one-step hydrothermal method. Through morphology analysis, this catalyst presents a three-dimensional cross-linked nanorod-nanoblock structure. This unique dual morphology structure effectively increases the exposed area of active sites and significantly improves the charge transfer rate, thereby enhancing the OER and HER performance of the catalyst simultaneously.

[0024] The iron-rich transition metal selenide electrolyzed water catalyst CuFe-Se / CFF obtained by the simple one-step hydrothermal reaction of the present invention has a three-dimensional cross-linked nanorod-nanoblock structure. The large surface area provides more active sites, and the cross-linked structure promotes the rapid transfer of charges, thereby efficiently and stably catalyzing the electrolyzed water process. The electronegativity difference between copper and iron causes strong electron coupling, effectively regulating the electronic structure of iron sites and optimizing the adsorption energy and d-band center of reaction intermediates of the catalyst, further improving the electrocatalytic activity of the material. In addition, the present invention overcomes the characteristics of traditional electrocatalysts such as high price, high energy consumption and poor stability, and only requires a driving voltage of 1.44 V to reach a current density of 10 mA cm -2 and has good application prospects in the aspect of hydrogen production by electrolyzed water.

[0025] The beneficial effects of the present invention are:

[0026] 1. The iron-rich transition metal selenide electrolyzed water catalyst of the present invention is synthesized by a simple one-step hydrothermal method, with low raw material cost, simple preparation method, easy to operate, and suitable for industrial scale production.

[0027] 2. The selenide electrolyzed water catalyst of the present invention is based on an iron-rich transition metal selenide system. By utilizing the electronegativity difference between copper and iron, a strong electron coupling effect is generated, thereby regulating the electronic structure of iron sites, optimizing the d-band center, reducing the overpotential during the reaction process, and greatly reducing the energy consumption of electrolyzed water.

[0028] 3. The present invention overcomes the characteristics of traditional electrocatalysts, such as high cost, high energy consumption, and poor stability, and has good application prospects in the field of hydrogen production by electrolyzing water. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is the preparation flow chart of the iron-rich transition metal selenide electrolyzed water catalyst prepared in Example 1 of the present invention;

[0030] Figure 2 It is the scanning electron microscope image of the iron-rich transition metal selenide electrolyzed water catalyst prepared in Example 1 of the present invention;

[0031] Figure 3 It is the transmission electron microscope image of the iron-rich transition metal selenide electrolyzed water catalyst prepared in Example 1 of the present invention.

[0032] Figure 4 It is the X-ray diffraction pattern of the iron-rich transition metal selenide electrolyzed water catalyst prepared in Example 1 of the present invention.

[0033] Figure 5 It is the electrochemical performance test chart of Example 1 and Comparative Examples 1-3 of the present invention.

[0034] Figure 6 It is the electrochemical performance test chart of Examples 1-2 and Examples 5-7 of the present invention.

[0035] Figure 7 It is the electrochemical performance test chart of Examples 1, 3 and Example 8 of the present invention.

[0036] Figure 8 It is the electrochemical performance test chart of Examples 1, 4 and Examples 9-11 of the present invention.

[0037] Figure 9 It is the overall water electrolysis electrochemical performance test chart of Example 1 and Comparative Example 3 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0038] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. It should be particularly noted that the following embodiments are only a part of the embodiments of the present invention, not all of the embodiments. Based on the content of the present invention, other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0039] Example 1: Preparation of CuFe-Se / CFF

[0040] In this example, commercial copper-iron foam CFF (purchased from Suzhou Taili Foam Metal Factory) was used as the carrier. The detailed preparation steps are as follows: Figure 1 as shown:

[0041] Step S1. Ultrasonic cleaning of the carrier: The cut carrier (size: 1×1.3 cm 2 ) was successively placed in 25 mL of acetone, 1 M hydrochloric acid, ethanol, and deionized water, and ultrasonically cleaned for 10 minutes one by one to remove surface oil and oxides. After cleaning, it was dried with filter paper for later use.

[0042] Step S2. Preparation of the reaction solution: Weigh 1.2 mmol of selenium powder and add it to a mixed solution of 20 mL of deionized water and 2 mL of hydrazine hydrate, mix well, and stir magnetically at 1800 rpm for 20 minutes. Subsequently, use ultrasonic dispersion at 40 kHz for 20 minutes to obtain a uniform mixed reaction solution.

[0043] Step S3. Hydrothermal reaction: The cleaned carrier and the above mixed reaction solution were placed together in a polytetrafluoroethylene reaction kettle and transferred to a forced-air drying oven, and reacted at 180 °C for 24 h.

[0044] Step S4. Post-treatment: After the reaction, take out the carrier, rinse it five times successively with deionized water and absolute ethanol, and then dry it in a forced-air drying oven at 65 °C for 12 h to obtain the CuFe-Se / CFF catalyst.

[0045] Examples 2 - 11: The preparation processes of Examples 2 - 11 are basically the same as that of Example 1, but the parameters for preparing the catalyst change. The specific differences are as follows:

[0046] Example 2: CuFe-Se / CFF - 0.9 mmol

[0047] The difference between Example 2 and Example 1 is that the amount of selenium powder used in Step S2 is changed to 0.9 mmol.

[0048] Example 3: CuFe-Se / CFF - 160 °C

[0049] The difference between Example 3 and Example 1 is that the reaction temperature in Step S3 is changed to 160 °C.

[0050] Example 4: CuFe-Se / CFF - 18 h

[0051] The difference between Example 4 and Example 1 is that the reaction time in Step S3 is changed to 18 h.

[0052] Examples 5 - 7: CuFe-Se / CFF - amount of selenium powder

[0053] Example 5 is different from Example 1 in that the amount of selenium powder in step S2 is changed to 0.3 mmol. Example 6 is different from Example 1 in that the amount of selenium powder in step S2 is changed to 0.6 mmol. Example 7 is different from Example 1 in that the amount of selenium powder in step S2 is changed to 1.5 mmol. The remaining steps are the same as those in Example 1.

[0054] Example 8: CuFe-Se / CFF - 200 °C

[0055] Example 2 is different from Example 1 in that the reaction temperature in step S3 is changed to 200 °C. The remaining steps are the same as those in Example 1.

[0056] Comparative Examples 9 - 11: CuFe-Se / CFF - reaction time

[0057] Example 9 is different from Example 1 in that the reaction time in step S3 is changed to 1 h. Example 10 is different from Example 1 in that the reaction time in step S3 is changed to 6 h. Example 11 is different from Example 1 in that the reaction time in step S3 is changed to 30 h. The remaining steps are the same as those in Example 1.

[0058] Comparative Examples 1 - 3: Comparative experiment design

[0059] Comparative Example 1: Fe-Se / FF

[0060] The preparation process of Comparative Example 1 is basically the same as that of Example 1, except that the carrier is changed from copper-iron foam CFF to iron foam FF. The remaining steps are the same as those in Example 1.

[0061] Comparative Example 2: Cu-Se / CF

[0062] The preparation process of Comparative Example 2 is basically the same as that of Example 1, except that the carrier is changed from copper-iron foam CFF to copper foam CF. The remaining steps are the same as those in Example 1.

[0063] Comparative Example 3: Preparation of Pt / C / CFF:

[0064] The preparation method is as follows: Mix 50 mg of 20% Pt / C with 60 μL of fluorosulfonic acid-based polymer and 540 μL of deionized water, and ultrasonically disperse for 60 minutes to obtain a homogeneous solution. Immerse the cleaned copper-iron foam carrier (1.3 cm × 1 cm) in the solution and then take it out, and dry it at 65 °C for 6 h to prepare a Pt / C / CFF electrode with a mass loading of 19.8 mg / cm 2 ².

[0065] Preparation of RuO₂ / CFF:

[0066] The preparation method is as follows: 50 mg of RuO2 powder is mixed with 60 μL of fluorosulfonic acid-based polymer and 540 μL of deionized water, and ultrasonically dispersed for 60 minutes to obtain a homogeneous solution. After immersing the cleaned copper-iron foam carrier (1.3 cm × 1 cm) in the solution and then taking it out, it is dried at 65 °C for 6 h to prepare a RuO2 / CFF electrode with a mass loading of 19.8 mg / cm 2 2

[0067] Experimental Results and Analysis

[0068] Figure 2 Figure 1 is the scanning electron microscope image of CuFe-Se / CFF prepared in Example 1. The cross-linked rough nanorod-rough nanoblock morphology greatly increases the electrochemically active surface area, exposes more active sites, the nanoblock structure ensures the stability of the catalyst, and the cross-linking of the nanoblock and the nanorod promotes the charge transfer during the reaction process.

[0069] Figure 3 Figure 2 is the transmission electron microscope image of CuFe-Se / CFF prepared in Example 1. It can also be observed from Figure 3 it the cross-linked nanorod-nanoblock structure, which is consistent with Figure 2 Figure 1.

[0070] Figure 4 Figure 3 is the X-ray diffraction (XRD) pattern of CuFe-Se / CFF prepared in Example 1. The characteristic diffraction peaks match the standard cards of the three phases of Cu 7.16 Se4 (PDF No. 01-071-4325), CuFeSe2 (PDF No. 00-044-1305) and Cu 0.74 Fe 0.26 Se 2-x (PDF No. 00-026-0529). Therefore, it is determined that the main active substances on the copper-iron foam carrier are Cu 7.16 Se4, CuFeSe2 and Cu 0.74 Fe 0.26 Se 2-x 3

[0071] Electrochemical testing method: All electrochemical tests were carried out at 25 °C using a standard three-electrode system powered by a Princeton electrochemical workstation (model PARSTAT 3000A-DX, Ametek) and controlled by VersaStudio v2.66.2 software. An Ag / AgCl electrode (saturated KCl) was used as the reference electrode and calibrated before and after each test to ensure data accuracy. All prepared self-supporting electrodes were loaded onto a platinum sheet electrode clamp, with an area of 1 cm × 1 cm as the working electrode, and a graphite rod was used as the counter electrode. The electrolyte was 1 mol / KOH solution with a pH of ~13.6. In addition, a two-electrode system was used, and the CuFe-Se / CFF of Example 1 was used as both the cathode and anode to study the overall water electrolysis performance, and Pt / C / CFF||RuO2 / CFF of Comparative Example 3 was used as a comparative experiment.

[0072] Figure 5 Electrochemical performance test diagrams for Example 1 and Comparative Examples 1-3. Figure 5 a is the polarization curve of OER. In Example 1, CuFe-Se / CFF showed the lowest overpotential, only requiring 330 mV at a current density of 1000 mA / cm 2 ². Figure 5 b is the Tafel slope curve of OER. In Example 1, CuFe-Se / CFF showed the lowest Tafel slope, indicating the fastest OER kinetics. Figure 5 c is the impedance spectrum diagram of OER. In Example 1, CuFe-Se / CFF showed the smallest semicircle impedance, indicating the fastest charge transfer rate. Figure 5 d is the polarization curve of HER, Figure 5 e is the Tafel curve of HER, Figure 5 f is the impedance spectrum diagram of HER. Although CuFe-Se / CFF in Example 1 showed an overpotential, Tafel slope, and electrochemical impedance only slightly inferior to those of the noble metal Pt / C / CFF, CuFe-Se / CFF in Example 1 was significantly better than Fe-Se / FF and Cu-Se / CF. Overall, this shows that CuFe-Se / CFF exhibits quite excellent OER and HER catalytic activities simultaneously.

[0073] Figure 6 Electrochemical performance test diagrams for Examples 1-2 and Examples 5-7. Figure 7 Electrochemical performance test diagrams for Examples 1, 3, and Example 8. Figure 8 Electrochemical performance test diagrams for Examples 1, 4, and Examples 9-11. At Figures 6 - 8Among them, a is the polarization curve of OER; b is the Tafel slope curve of OER; c is the impedance spectrogram of OER; d is the polarization curve of HER; e is the Tafel slope curve of HER; f is the impedance spectrogram of HER. In all tests, Example 1 showed the lowest overpotential, the lowest Tafel slope, and the smallest electrochemical impedance during both OER and HER processes, indicating that different preparation parameters (such as reactant dosage, reaction temperature, and time) have a significant impact on the performance of the catalyst, and Example 1 is the catalyst with the best performance.

[0074] Figure 9 shows the polarization curves of the overall water splitting of the CuFe-Se / CFF||CuFeSe / CFF and Pt / C / CFF||RuO2 / CFF two-electrode systems ( Figure 9 a) and the long-term stability curves ( Figure 9 b). From Figure 9 a, it can be seen that the CuFe-Se / CFF||CuFeSe / CFF only requires voltages of 1.44 V and 1.87 V to drive current densities of 10 mA / cm 2 and 100 mA / cm 2 , while the Pt / C / CFF||RuO2 / CFF requires 1.51 V and 1.88 V respectively, which indicates that the CuFe-Se / CFF||CuFeSe / CFF is significantly superior to the noble metal-based electrode in terms of overall water splitting performance. In addition, from Figure 9 b, it can be seen that the CuFe-Se / CFF||CuFeSe / CFF shows excellent long-term stability at a current density of 100 mA / cm 2 , and the voltage fluctuation amplitude is significantly smaller than that of the Pt / C / CFF||RuO2 / CFF. This further proves that the CuFe-Se / CFF||CuFeSe / CFF not only has excellent overall water splitting performance but also maintains excellent stability under high current density conditions.

[0075] In summary, the present invention provides an iron-rich transition metal selenide electrolytic water catalyst prepared by a simple one-step hydrothermal method, which significantly improves the catalytic activities of OER and HER, reduces the preparation cost at the same time, and has the potential for industrial application.

[0076] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. An iron-rich transition metal selenide water electrolysis catalyst, characterized in that: The invention comprises a carrier and an iron-rich transition metal selenide loaded on the carrier.

2. The iron-rich transition metal selenide electrolyzed water catalyst according to claim 1, wherein: The carrier described above is foamed iron copper, and the iron-rich transition metal selenide adopts Cu 7.16 Se4, CuFeSe2, Cu 0.74 Fe 0.26 Se 2-x one or more of them.

3. The electrolytic water catalyst based on iron-rich transition metal selenide according to claim 1, characterized in that: The content of iron in the carrier is 80-85%, and the content of copper is 15-20%.

4. A preparation method of the iron-rich transition metal selenide electrolyzed water catalyst as described in any one of claims 1-3, characterized in that, The following steps are involved: Step S1: First, the carrier is ultrasonically cleaned to remove oil and oxides on the surface of the carrier; Step S2: Next, add selenium powder to the mixed solution of water and hydrazine hydrate, fully stir with a magnetic stirrer, and then disperse with an ultrasonic stirrer until uniformly mixed to obtain a mixed reaction solution: Step S3: transferring the mixed reaction solution obtained in step S2 and the carrier cleaned by ultrasonication into a polytetrafluoroethylene reactor for reaction; Step S4: The reaction product generated in step S3 is washed and dried in sequence to finally obtain an iron-rich transition metal selenide water electrolysis catalyst.

5. The preparation method of an iron-rich transition metal selenide electrolyzed water catalyst according to claim 4, characterized in that: The carrier in step S1 is foamed iron copper, and the specific method of ultrasonic cleaning in step S1 is: ultrasonically clean the foamed iron copper using acetone, hydrochloric acid, ethanol and deionized water in sequence, with each solvent cleaning for no less than 10 minutes, and then wipe dry with filter paper.

6. The preparation method of an iron-rich transition metal selenide electrolyzed water catalyst according to claim 4, wherein: In the step S2, the volume ratio of water to hydrazine hydrate in the mixed solution of water and hydrazine hydrate is 30:1 to 5:1, and the concentration of selenium powder in the mixed reaction solution is 0.01 to 0.75 mmol / mL.

7. The preparation method of an iron-rich transition metal selenide electrolytic water catalyst according to claim 4, characterized in that: In the step S3, the reaction temperature in the polytetrafluoroethylene reactor is 80 to 250° C., and the reaction time is 1 to 60 hours.

8. The preparation method of an iron-rich transition metal selenide electrolyzed water catalyst according to claim 4, characterized in that: The washing method in step S4 is to wash the reaction product with anhydrous ethanol and deionized water in turn, and the washing times of anhydrous ethanol and deionized water are not less than 5 times; the drying method is to dry the washed reaction product under a blast environment of 40-80°C for not less than 10 hours.

9. Use of the iron-rich transition metal selenide water electrolysis catalyst obtained by the preparation method according to any one of claims 4 to 8 as a bifunctional electrode in alkaline water electrolysis.

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