Alkaline system electrolyzed water anode catalyst and preparation method thereof

Abstract

The invention relates to an alkaline system electrolyzed water anode catalyst and a preparation method thereof, foamed nickel is soaked in an aqueous solution containing thiourea and ferrous chloride, a reaction is carried out at 70-100 DEG C, a mixed layer rich in sulfide-oxide nanoparticles is formed on a foamed nickel substrate through vulcanization and wet chemical processes, and the composite catalyst S-NiFeOxHy / NF is prepared. The S-doped NiFe (oxygen) hydroxide self-supporting anode oxygen evolution reaction catalyst is prepared by adopting a simple, convenient and efficient method, and the S-doped NiFe (oxygen) hydroxide self-supporting anode oxygen evolution reaction catalyst has excellent electrochemical reaction activity and stability as an alkaline system electrolyzed water anode catalyst.

Description

Technical Field

[0001] The present invention relates to a catalyst for water electrolysis anode, and in particular to a water electrolysis anode catalyst in an alkaline system and a preparation method thereof. The catalyst of the present invention can be used for electrochemical catalytic oxidation of oxygen evolution reaction in hydrogen production by water electrolysis. Background Art

[0002] As the cleanest energy carrier, hydrogen is essential to building a carbon-free and sustainable ecological energy system. By combining intermittent electricity such as wind power and photovoltaic power with electrocatalytic whole water electrolysis (OWS) technology, green hydrogen can be produced on a large scale using the abundant water resources on the earth. This strategy shows great development potential.

[0003] The OWS process consists of the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. The OER involves a four-electron transfer process, which is kinetically slower than the HER, severely limiting the overall energy efficiency of the OWS. In recent years, researchers have been committed to developing efficient OER catalysts, such as transition metal (oxy)hydroxides, selenides, phosphides, and nitrides. It is gratifying that the performance of some new catalysts has surpassed that of traditional iridium dioxide (IrO 2 ) and ruthenium dioxide (RuO 2 ) Standard base catalyst.

[0004] Currently, transition metal-based (oxy)hydroxides, especially NiFe-based (oxy)hydroxides, are the most effective OER catalysts among all candidates to date. A large amount of research work is devoted to further improving the OER activity of NiFe-based (oxy)hydroxide catalysts through various strategies, including designing catalyst morphology to increase the number of active sites, introducing non-metallic doping to adjust the catalyst electronic structure, and constructing overall electrodes to improve the catalyst electron transfer efficiency.

[0005] Ma et al. (Short-time potentiostatic assisted borate to induce the generation of ultrathin NiFe LDH active phase for industrial-level water oxidation, Chem. Eng. J ., 2024, 490: 151490) By preparing B-doped NiFe LDH nanosheets with rich wrinkled structures, the OER catalytic performance of the material was significantly improved, and 100 mA cm-2 was achieved with an overpotential of only 290 mV. -2 This is mainly due to the fact that B doping optimizes the adsorption capacity of oxygen-containing intermediates and improves the intrinsic activity of the catalyst.

[0006] Lee et al. (Engineering durable anion exchange membrane water electrolyzers through suppressed electrochemical corrosion of a NiFe-Graphitic carbon shell anode catalyst, ACS Catalysis , 2024, 14: 9969-9984) prepared a catalyst by introducing graphitic carbon layers (GCLs) to coat NiFe catalytic nanoparticles, and the prepared catalyst showed extremely high stability for OER and could continuously operate for 1100 h. Its excellent stability stems from the strong interaction between the catalyst and the carbon support.

[0007] The above highly efficient OER catalyst has significantly promoted the development of large-scale water electrolysis hydrogen production technology. However, people often overlook the energy and time consumption in the catalyst synthesis process, which is equally important as catalytic activity. For example, one of the most active HER catalysts reported currently is MoNi 4 / MoO 2 , which only requires an overpotential of 15 mV at a current density of 10 mA cm -2 , and only 70 mV at 500 mA cm -2 . However, the synthesis process of this catalyst is complex and time-consuming, requiring multi-step long-time reactions under high-temperature conditions and even the use of high-purity hydrogen, so it is not suitable for large-scale applications. And this problem also exists in most reported NiFe-based OER catalysts.

[0008] Wu et al. (Tracking the structural evolution and activity origin of Co-doped NiFe layered double hydroxide for enhanced oxygen evolution reaction, Chem. Eng. J , 2024, 488: 151086) prepared a ternary NiFeCo-0.6 composite with a unique nanosheet-nanowire hybrid morphology by reacting at 120 °C for 6 h in an autoclave. This composite showed excellent activity for OER and only required an overpotential of 261 mV to reach 100 mA cm -2Current density. Li et al. (Cl modulation on boron-rich carbon embedded with NiFe alloys for efficient oxygen evolution reaction, Chem. Eng. J . 2023, 462: 142267) prepared the Fe1Ni2@ClBC composite by grinding combined with high-temperature pyrolysis (calcination at 900 °C for 2 h), which has excellent activity for OER and can reach a current density of 10 mA cm -2 with an overpotential of only 259 mV. However, the synthesis process of these catalysts often requires multiple steps under high-temperature / high-pressure conditions, which not only significantly increases the consumption of time and energy but also becomes an important factor restricting their wide application.

[0009] In view of this, to accelerate the development of hydrogen energy technology, it is particularly urgent to explore an economical, efficient, simple, and feasible method for synthesizing NiFe-based OER catalysts. Summary of the Invention

[0010] The purpose of the present invention is to provide an anode catalyst for alkaline water electrolysis and its preparation method, to prepare a composite anode catalyst for water electrolysis through a low-temperature rapid reaction, and to improve the activity and stability of the catalyst.

[0011] The anode catalyst for alkaline water electrolysis described in the present invention uses nickel foam as the substrate and nickel source, ferrous chloride as the iron source, and thiourea as the sulfur source. The nickel foam is impregnated in an aqueous solution containing thiourea and ferrous chloride and reacted at 70-100 °C. Through a sulfidation and wet chemical process, a mixed layer rich in sulfide-oxide nanoparticles is formed on the nickel foam substrate to prepare the composite catalyst S-NiFeO x H y / NF.

[0012] Among them, further, the molar ratio of the raw materials thiourea and ferrous chloride is preferably 1:0.1-10.

[0013] Furthermore, the molar ratio of thiourea to ferrous chloride is more preferably 1:1.

[0014] Furthermore, the present invention also provides a specific preparation method for the anode catalyst for alkaline water electrolysis, which is to first dissolve thiourea and ferrous chloride in deionized water to obtain a mixed solution, then impregnate the nickel foam in the mixed solution, and heat it to 70-100 °C for reaction to prepare the S-NiFeO x H y / NF composite catalyst.

[0015] Among them, more specifically, the reaction time is preferably 3 to 60 minutes.

[0016] The present invention adopts a simple, efficient and brand-new synthesis method. At a short time and a relatively low temperature, a self-supported OER catalyst of S-doped NiFe (oxy) hydroxide is prepared by one-step sulfidation and a wet chemical process. During this process, nickel foam reacts rapidly with S 2- , Fe 2+ and dissolved O 2 in the solution, and a sulfide-oxide mixed layer rich in nanoparticles is formed on the nickel foam substrate. This structure not only promotes the rapid transfer of electrons, but also significantly enhances the stability of the catalyst. Using the S-NiFeO x H y / NF composite catalyst prepared by the present invention as the anode catalyst for electrolytic water in an alkaline system has excellent electrochemically reactive activity.

[0017] The S-NiFeO x H y / NF composite catalyst prepared by the present invention can be directly used as the working electrode for OER without further treatment.

[0018] By doping heteroatom S into the anode catalyst for electrolytic water, the present invention regulates the electronic structure of the catalyst and further improves the catalytic activity of the S-NiFeO x H y / NF composite catalyst. The oxygen evolution reaction activity of the composite catalyst prepared by the present invention is tested by linear sweep voltammetry. At a scanning rate of 1 mV / s, the overpotential required to reach a current density of 10 mA cm -2 in 1 M KOH electrolyte is only 204 mV, showing an obvious catalytic effect on the oxygen evolution reaction. At the same time, at a current density of 100 mA cm -2 , after 500 h of constant current (CP) test, the potential growth rate is only 7.0%. Description of the Drawings

[0019] Figure 1 is the X-ray diffraction pattern of the S-NiFeO x H y / NF composite catalyst prepared in Example 1.

[0020] Figure 2 is the X-ray photoelectron spectroscopy pattern of the S-NiFeO x H y / NF composite catalyst prepared in Example 1.

[0021] Figure 3 is the S-NiFeO prepared in Example 1 x H ySEM-EDS-mapping images of the S-NiFeO₂ / NF composite catalyst.

[0022] Figure 4 It is the S-NiFeO₂ prepared in Example 1 x H y LSV graph of the S-NiFeO₂ / NF composite catalyst in 1 M KOH solution.

[0023] Figure 5 It is the S-NiFeO₂ prepared in Example 1 x H y 500 h CP test graph of the S-NiFeO₂ / NF composite catalyst. Embodiment

[0024] The following further describes the specific embodiments of the present invention in detail in conjunction with the drawings and examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention, so that those skilled in the art can well understand and make full use of the present invention.

[0025] However, the present invention can be implemented in many other ways different from those described in the following examples, and those skilled in the art can also make similar improvements without departing from the connotation of the present invention. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0026] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art. The terms used in the specification of the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0027] The term "and / or" used in the present invention includes any and all combinations of one or more of the related listed items.

[0028] The terms "multiple", "diverse", "multiple times", "multiple groups", etc. used in the present invention, unless otherwise specified, refer to a quantity greater than or equal to 2; "above" includes the number itself, such as "two or more" includes two, three or more.

[0029] The term "preferred" used in the present invention is only for describing embodiments or examples with better effects and does not constitute a limitation on the protection scope of the present invention.

[0030] The production processes, experimental methods or detection methods involved in the embodiments of the present invention, unless otherwise specified, are all conventional methods in the prior art, and their names and / or abbreviations are all conventional names in the art and are very clear and definite in the relevant application fields. Those skilled in the art can understand the conventional process steps according to the name and apply the corresponding equipment, according to the conventional conditions or the conditions recommended by the manufacturer, or refer to the experimental methods known in the art for implementation.

[0031] There are no special restrictions on the sources of various instruments, equipment, raw materials or reagents used in the embodiments of the present invention. They are all conventional products that can be obtained through regular commercial channels, and can also be prepared according to conventional methods well-known to those skilled in the art.

[0032] The specific preparation method of the alkaline system electrolyzed water anode catalyst of the present invention includes:

[0033] 1) Dissolve thiourea and ferrous chloride in deionized water to obtain a mixed solution;

[0034] 2) Immerse nickel foam in the mixed solution and react at 70-100 °C for 3-60 min to prepare the S-NiFeO x H y / NF composite catalyst.

[0035] In a specific embodiment, the thiourea and ferrous chloride are dissolved at room temperature to obtain a mixed solution.

[0036] In a more specific embodiment, the content of thiourea in the mixed solution is preferably 0.05-20 mol / L, and the content of ferrous chloride is preferably 0.05-20 mol / L.

[0037] In a specific embodiment, the reaction is carried out under a water bath condition.

[0038] In the above preparation method of the present invention, after the reaction is completed, the color of the nickel foam will change from the original metallic luster to yellowish-brown. Take it out of the solution, wash it repeatedly with deionized water and ethanol, and dry it in the air, then it can be directly used as a working electrode.

[0039] Unless otherwise specified, for the dosage of raw material components and measurement parameters such as temperature and time involved in the embodiments of the present invention, there may be slight deviations within the weighing or measurement accuracy range, and acceptable deviations caused by the instrument test accuracy or operation accuracy are allowed. Examples

[0040] Example 1

[0041] Add 8 mmol of ferrous chloride and 8 mmol of thiourea to 10 mL of deionized water respectively, dissolve evenly to obtain a mixed solution.

[0042] Add a piece of commercial nickel foam (NF) with a specification of 1×2 cm 2 to the mixed solution, heat it to 90 °C in a water bath and react for 10 min to prepare the S-NiFeO x H y / NF composite catalyst.

[0043] Figure 1The X-ray diffraction pattern of the prepared composite catalyst was given and compared with the standard card Ni (PDF#04-0850) of the Joint Committee on Powder Diffraction Standards. The composite catalyst only showed three strong diffraction peaks of the NF substrate and did not show other diffraction peaks, which was due to the low contents of Fe and S.

[0044] Furthermore, X-ray photoelectron spectroscopy was used to determine the element distribution in the composite catalyst, and the results are as Figure 2 , proving the successful introduction of S and Fe. And Figure 3 SEM-EDS was further used to determine the element distribution in the composite catalyst, once again proving the successful introduction of S and Fe.

[0045] The above characterization results confirmed the successful synthesis of the S-NiFeO x H y / NF composite catalyst.

[0046] Example 2

[0047] 4 mmol of ferrous chloride and 8 mmol of thiourea were respectively added to 10 mL of deionized water and dissolved uniformly to obtain a mixed solution.

[0048] A piece of commercial nickel foam (NF) with a size of 1×2 cm 2 was added to the mixed solution, and the mixture was heated to 90 °C in a water bath and reacted for 10 min to prepare the S-NiFeO x H y / NF composite catalyst.

[0049] Example 3

[0050] 12 mmol of ferrous chloride and 8 mmol of thiourea were respectively added to 10 mL of deionized water and dissolved uniformly to obtain a mixed solution.

[0051] A piece of commercial nickel foam (NF) with a size of 1×2 cm 2 was added to the mixed solution, and the mixture was heated to 90 °C in a water bath and reacted for 10 min to prepare the S-NiFeO x H y / NF composite catalyst.

[0052] Example 4

[0053] 8 mmol of ferrous chloride and 4 mmol of thiourea were respectively added to 10 mL of deionized water and dissolved uniformly to obtain a mixed solution.

[0054] A piece of commercial nickel foam (NF) with a size of 1×2 cm 2 was added to the mixed solution, and the mixture was heated to 90 °C in a water bath and reacted for 10 min to prepare the S-NiFeOx H y S-NiFeO₂H / NF composite catalyst.

[0055] Example 5

[0056] 8 mmol of ferrous chloride and 12 mmol of thiourea were respectively added to 10 mL of deionized water and dissolved evenly to obtain a mixed solution.

[0057] A piece of commercial nickel foam (NF) with a size of 1×2 cm was added to the mixed solution, and the mixture was heated to 90 °C in a water bath and reacted for 10 min to prepare S-NiFeO₂H / NF composite catalyst. 2 x H y / NF composite catalyst.

[0058] Application example

[0059] Using the S-NiFeO₂H / NF composite catalyst prepared in Example 1 as the working electrode directly, a 1 cm×1 cm Pt sheet as the counter electrode, and a Hg / HgO electrode as the reference electrode, a three-electrode system was adopted, and the electrochemical performance of the composite catalyst was characterized by linear sweep voltammetry (LSV). x H y / NF composite catalyst, a 1M KOH solution was used as the electrolyte solution, and an OER activity test was carried out using a Shanghai Chenhua CHI 660E electrochemical workstation.

[0060] As shown in the test results, in a 1M KOH solution, when the scanning rate was 1 mV / s and the current density reached 10 / 100 mA cm⁻², the S-NiFeO₂H / NF composite catalyst only required an overpotential of 204 / 236 mV, indicating that the composite catalyst had an obvious catalytic effect on OER.

[0061] Furthermore, Figure 4 in a 1M KOH solution, after 500 h of CP test, that is, the change trend of the potential with time was investigated at a current density of 100 mA cm⁻², and the potential increase rate in 500 h was only 7.0%, indicating that the composite catalyst had good stability. -2 x H y / NF composite catalyst.

[0062] Furthermore, Figure 5 in a 1M KOH solution, after 500 h of CP test, that is, the change trend of the potential with time was investigated at a current density of 100 mA cm⁻², and the potential increase rate in 500 h was only 7.0%, indicating that the composite catalyst had good stability. -2

[0063] The preparation methods and processes of traditional OER catalysts are complex, which directly affect their OER electrochemistry reaction activity. Table 1 below gives the S-NiFeO₂H / NF composite catalysts prepared in Examples 1 to 5 of the present invention at 10 / 100 mA cm⁻². x H y / NF composite catalyst at 10 / 100 mA cm⁻². -2 ​​​The overpotential at a current density was presented, and the performance of some reported OER catalysts in the literature was listed for comparison.

[0064]

[0065] According to the data in Table 1, it can be seen that at a current density of 10 mA cm -2 −2, the overpotentials required for the catalysts in the cited literature are all relatively high, indicating their low activity towards OER; meanwhile, the stability of the catalysts in the literature is also poor. In comparison, the composite catalyst prepared in the present invention significantly improves the catalytic activity and stability of OER.

[0066] [1]. J. Li, K. Zheng, C. Zhang, L. Jiao, Z. Dong, X. Tao, R. Su, H. Xie, C. Xu, Cl modulation on boron-rich carbon embedded with NiFe alloys for efficient oxygen evolution reaction, Chem. Eng. J. 462 (2023). https: / / doi.org / 10.1016 / j.cej.2023.142267.

[0067] [2]. Y. Ma, J.-J. Wang, X.-H. Liu, N. Xu, X. Li, Y.-H. Wang, L.-M. Zhao, Y.-M. Chai, B. Dong, Short-time potentiostatic assisted borate to induce the generation of ultrathin NiFe LDH active phase for industrial-level water oxidation, Chem. Eng. J. 490 (2024). https: / / doi.org / 10.1016 / j.cej.2024.151490.

[0068] [3]. Y. Wu, Y. Li, Z. Xie, Y. Wang, Y. Wang, B. Wei, Tracking thestructural evolution and activity origin of Co-doped NiFe layered doublehydroxide for enhanced oxygen evolution reaction, Chem. Eng. J. 488 (2024).https: / / doi.org / 10.1016 / j.cej.2024.151086.

[0069] The technical features of the above embodiments of the present invention can be combined arbitrarily. For the sake of brevity of description, all possible combinations of the technical features in the embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in the specification of the present invention.

[0070] The above embodiments represent several relatively specific and detailed implementation manners of the present invention, but should not be construed as a limitation on the protection scope of the present invention. It should be noted that those of ordinary skill in the art can make several substitutions, deformations or improvements without departing from the principle and purpose of the present invention, and all of them should be included in the protection scope of the present invention.

Claims

1. An alkaline system water electrolysis anode catalyst, which is a composite catalyst S-NiFeO prepared by immersing the nickel foam as a substrate and a nickel source, ferrous chloride as an iron source, and thiourea as a sulfur source in an aqueous solution containing thiourea and ferrous chloride and reacting at 70-100°C x H y / NF.

2. The alkaline system water electrolysis anode catalyst according to claim 1, characterized in that The molar ratio of thiourea to ferrous chloride is 1:0.1-10.

3. The method for preparing the alkaline system water electrolysis anode catalyst according to claim 1 is to first dissolve thiourea and ferrous chloride in deionized water to obtain a mixed solution, then immerse the nickel foam in the mixed solution, heat it to 70-100° C. for reaction, and prepare the S-NiFeO x H y / NF composite catalyst.

4. The preparation method according to claim 3, characterized in that The content of ferrous chloride in the mixed solution is 0.05-20 mol / L, and the content of thiourea is 0.05-20 mol / L.

5. The preparation method according to claim 3, characterized in that The reaction time is 3 to 60 minutes.

6. Application of the alkaline system water electrolysis anode catalyst as claimed in claim 1 directly as a working electrode for the water electrolysis anode oxygen evolution reaction.

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