Medium-entropy Prussian blue analogue derivative sulfide catalyst and preparation method thereof

Abstract

The invention is suitable for the technical field of catalysts for hydrogen production through electrolysis of water, and provides a medium-entropy Prussian blue analogue derivative sulfide catalyst and a preparation method thereof.The preparation method comprises the following steps that Ni (NO3) 2.6 H2O and C6H5Na3O7. 2H2O are dissolved in deionized water, and a solution A is formed through magnetic stirring; dissolving K3 [Co (CN) 6] and K3 [Fe (CN) 6] in deionized water, and magnetically stirring to form a solution B; adding the solution B into the solution A, and stirring at room temperature to obtain a mixed solution; heating the mixed solution in a water bath and stirring; carrying out centrifugal treatment on the mixed solution, separating to obtain a precipitate, washing for multiple times, and carrying out vacuum drying overnight to obtain a FeCoNi-PBA precursor; the FeCoNi-PBA precursor and excessive sulfur powder are placed in two porcelain boats respectively, the two porcelain boats are placed on the downstream and the upstream of a tubular furnace, in the argon atmosphere, the temperature is increased, heat preservation treatment is conducted, and the medium-entropy sulfide named as FeCoNi-S is obtained. The bifunctional catalyst with rich defects and high specific surface area is prepared, and efficient and stable hydrogen production and oxygen production through water electrolysis are achieved.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology for hydrogen production by water electrolysis, and particularly relates to a medium-entropy Prussian blue analogue-derived sulfide catalyst and its preparation method. Background Technology

[0002] Electrolysis of water to produce hydrogen is a sustainable and clean energy technology that generates hydrogen through the electrochemical splitting of water, involving two key half-reactions: the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Highly efficient catalysts are crucial for reducing reaction overpotential and improving energy conversion efficiency. Noble metal catalysts (such as Pt for the HER and IrO2 for the OER) exhibit excellent performance, but their high cost and limited resources restrict their large-scale application.

[0003] Transition metal compound catalysts (such as sulfides, phosphides, and oxides) have been widely studied due to their low cost and abundant resources. Among them, metal sulfides (such as FeS2, CoS2, and NiS2) have good electrical conductivity and catalytic activity, but the activity and stability of single-component sulfides are limited, and they tend to have excessive crystallinity and few defects during preparation, which is not conducive to the exposure of catalytic sites.

[0004] Prussian blue analogues are derived from the structure of Prussian blue (PB) and are transition metal compound materials with a three-dimensional rigid open framework structure, often referred to as Prussian blue analogues (PBA). The molecular formula of Prussian blue analogues can be expressed as A. x M[M'(CN)6] y □ 1-y ·zH₂O (0≤x≤2,0≤y≤1), where A represents an alkali metal or alkaline earth metal, M and M' represent transition metals, and □ represents an M'(CN)₆ vacancy, possesses high specific surface area, tunable composition, and easy derivatization, making it suitable as a precursor for preparing derivatized materials (such as sulfides). By introducing multiple metal elements (such as Fe, Co, Ni), medium-entropy or multi-entropy materials can be constructed, utilizing the entropy effect to optimize electronic structure and enhance conductivity and catalytic activity. However, existing low-entropy PBA-derived sulfides exhibit weak entropy effects and insufficient synergistic effects of metal elements, resulting in limited improvement in catalytic performance. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a medium-entropy Prussian blue analogue-derived sulfide catalyst, aiming to solve the problems mentioned in the background art.

[0006] The present invention is implemented as follows: a method for preparing a medium-entropy Prussian blue analogue-derived sulfide includes the following steps: Step 1: Dissolve Ni(NO3)2·6H2O and C6H5Na3O7·2H2O in deionized water and stir magnetically to form solution A; Step 2: Dissolve K3[Co(CN)6] and K3[Fe(CN)6] in deionized water and stir magnetically to form solution B; Step 3: Add solution B to solution A and stir at room temperature to obtain a mixed solution; Step 4: Heat the mixed solution in a water bath while stirring; Step 5: Centrifuge the mixed solution to separate the precipitate, wash it several times, and then vacuum dry it overnight to obtain the FeCoNi-PBA precursor; Step 6: Place the FeCoNi-PBA precursor and excess sulfur powder in two ceramic boats, respectively, and place them downstream and upstream of a tube furnace. Under an argon atmosphere, heat the furnace and then hold it at that temperature to obtain a medium-entropy sulfide, named FeCoNi-S.

[0007] Another objective of this invention is to provide a medium-entropy Prussian blue analogue-derived sulfide, which is prepared using the above-described preparation method.

[0008] Another objective of this invention is to provide a medium-entropy Prussian blue analogue-derived sulfide catalyst, the catalyst comprising the aforementioned medium-entropy Prussian blue analogue-derived sulfide.

[0009] This invention introduces multiple metal elements (such as Fe, Co, and Ni) through medium-entropy design, optimizes the electronic structure using the entropy effect, and enhances the conductivity and catalytic activity of the material. At the same time, through a simple precipitation method and sulfidation process, a bifunctional catalyst with abundant defects and high specific surface area is prepared, achieving efficient and stable hydrogen and oxygen production by water electrolysis. Attached Figure Description

[0010] Figure 1 XRD patterns of FeCoNi-PBA, CoFe-PBA, FeNi-PBA and CoNi-PBA provided for embodiments of the present invention; Figure 2 XRD patterns of FeCoNi-S, CoFe-S, FeNi-S, and CoNi-S provided in embodiments of the present invention; Figure 3 SEM image of FeCoNi-S provided in an embodiment of the present invention; Figure 4 Oxygen evolution LSV curves of FeCoNi-S, CoFe-S, FeNi-S, and CoNi-S provided for embodiments of the present invention; Figure 5Oxygen evolution Tafel slope diagrams of FeCoNi-S, CoFe-S, FeNi-S, and CoNi-S provided for embodiments of the present invention; Figure 6 Hydrogen evolution LSV curves of FeCoNi-S, CoFe-S, FeNi-S, and CoNi-S provided for embodiments of the present invention; Figure 7 The hydrogen evolution Tafel slope diagrams of FeCoNi-S, CoFe-S, FeNi-S, and CoNi-S provided for embodiments of the present invention. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0012] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0013] Example 1: A medium-entropy Prussian blue analogue-derived sulfide catalyst, the preparation method of which includes the following steps: Step 1: Dissolve 6 mmol of Ni(NO3)2·6H2O (1.74474 g) and 9 mmol of C6H5Na3O7·2H2O (2.6469 g) in 50 mL of deionized water and stir magnetically for 10 min to form solution A; Step 2: Dissolve 2 mmol of K3[Co(CN)6] (0.66466 g) and 2 mmol of K3[Fe(CN)6] (0.6585 g) in 50 mL of deionized water and stir magnetically for 10 min to form solution B; Step 3: Slowly and regularly add solution B to solution A, stir at room temperature for 10 minutes to obtain a mixed solution; Step 4: Stir the mixed solution in a water bath at 60°C for 12 hours; Step 5: Centrifuge the mixed solution to separate the precipitate, wash it several times, and then vacuum dry it overnight at 60°C to obtain the FeCoNi-PBA precursor. Step Six: Place 0.08 g of FeCoNi-PBA precursor and excess sulfur powder in two separate ceramic boats, and place them downstream and upstream of a tube furnace. In an argon atmosphere, incubate at 5°C for 1 minute. -1 The temperature was increased to 500℃ at a heating rate and held at this high temperature for 2 h to obtain a medium-entropy sulfide, named FeCoNi-S. Step 7: Place 5 mg FeCoNi-S sample, 760 μL deionized water, 200 μL anhydrous ethanol, and 40 μL 5% naphthol solution in a vial, sonicate for 30 min, and then use a pipette to drop 5 μL of the slurry onto the working electrode to obtain the electrode material.

[0014] A three-electrode system was used: the counter electrode, reference electrode, and working electrode were used to test the oxygen evolution and hydrogen evolution performance at the Chenhua electrochemical workstation.

[0015] Comparative Example 1, CoFe-S catalyst, is prepared by the following steps: Step 1: Dissolve 6 mmol of Fe(NO3)3·9H2O (1.74474 g) and 9 mmol of C6H5Na3O7·2H2O (2.6469 g) in 50 mL of deionized water and stir magnetically for 10 min to form solution A; Step 2: Dissolve 4 mmol of K3[Co(CN)6] (1.3293 g) in 50 mL of deionized water and stir magnetically for 10 min to form solution B; Steps three, four, five, and six are the same as in Example 1, except that the only difference is that the obtained products are CoFe-PBA precursor and CoFe-S catalyst.

[0016] Comparative Example 2, FeNi-S catalyst, is prepared by the following steps: Step 1: Dissolve 6 mmol of Ni(NO3)2·6H2O (1.74474 g) and 12 mmol of C6H5Na3O7·2H2O (3.5292 g) in 50 mL of deionized water and stir magnetically for 10 min to form solution A; Step 2: Dissolve 4 mmol of K3[Fe(CN)6] (1.317 g) in 50 mL of deionized water and stir magnetically for 10 min to form solution B; Steps three, four, five, and six are the same as in Example 1, except that the FeNi-PBA precursor and FeNi-S catalyst are obtained.

[0017] Comparative Example 3, CoNi-S catalyst, is prepared by the following steps: Step 1: Dissolve 6 mmol of Ni(NO3)2·6H2O (1.74474 g) and 10 mmol of C6H5Na3O7·2H2O (2.941 g) in 50 mL of deionized water and stir magnetically for 10 min to form solution A; Step 2: Dissolve 4 mmol of K3[Co(CN)6] (1.3293 g) in 50 mL of deionized water and stir magnetically for 10 min to form solution B; Steps three, four, five, and six are the same as in Example 1, except that the only difference is that the obtained products are CoNi-PBA precursor and CoNi-S catalyst.

[0018] The FeCoNi-PBA, CoFe-PBA, FeNi-PBA, CoNi-PBA, FeCoNi-S, CoFe-S, FeNi-S, and CoNi-S prepared in Example 1 and Comparative Examples 1-3 were characterized, and the X-ray diffraction (XRD) patterns were obtained as follows: Figure 1 and Figure 2 As shown, where Figure 1 The diffraction peaks of the four PBA precursors correspond to those of the standard card (JCPDS card No. 01-0239) for Fe4[Fe(CN)6], and there are no other obvious diffraction peaks, indicating that the above-mentioned PBA precursors were successfully synthesized using this method; from Figure 2 It can be seen that the diffraction peaks of FeCoNi-S correspond to the standard card of FeS2 (JCPDS card No. 79-0617), indicating that a single-phase FeCoNi-S medium-entropy material was formed during the sulfidation process; the diffraction peaks of CoNi-S correspond to the standard card of NiS2 (JCPDS card No. 03-0734), indicating that a single-phase CoNi-S was formed during the sulfidation process; the diffraction peaks of CoFe-S correspond to the standard cards of CoS2 and FeS2 (JCPDS card No. 03-0772 and 79-0617), indicating that a mixed-phase CoFe-S was formed during the sulfidation process; the diffraction peaks of FeNi-S correspond to the standard cards of FeS2 and NiS2 (JCPDS card No. 79-0617 and 03-0734), indicating that a mixed-phase FeNi-S was formed during the sulfidation process. Scanning electron microscope (SEM) image of FeCoNi-S as follows: Figure 3 As shown, FeCoNi-S micron particles are composed of a large number of uniformly sized nanoparticles, exhibiting a rough surface and a large specific surface area, thus demonstrating good catalytic performance in water electrolysis. The linear sweep voltammetry (LSV) curves of the oxygen evolution reaction of FeCoNi-S, CoFe-S, FeNi-S, and CoNi-S prepared in Examples 1 and Comparative Examples 1-3 are shown below. Figure 4 As shown, it can be seen that at 10 mA cm -2 At the given current density, the overpotentials of FeCoNi-S, CoFe-S, FeNi-S, and CoNi-S were 232, 267, 263, and 289 mV, respectively. This indicates that FeCoNi-S has the lowest overpotential and exhibits the best performance in oxygen evolution during water electrolysis. The Tafel slope diagrams of the oxygen evolution reaction of FeCoNi-S, CoFe-S, FeNi-S, and CoNi-S prepared in Example 1 and Comparative Examples 1-3 are shown below. Figure 5 As shown, the Tafel slopes of FeCoNi-S, CoFe-S, FeNi-S, and CoNi-S are 107, 114, 109, and 133 mV dec, respectively. -1 This indicates that FeCoNi-S has the smallest Tafel slope and the fastest oxygen evolution reaction kinetics.

[0019] The LSV curves of the hydrogen evolution reaction of FeCoNi-S, CoFe-S, FeNi-S and CoNi-S prepared in Example 1 and Comparative Examples 1-3 are shown below. Figure 6 As shown, it can be seen that at 10 mA cm -2 At the given current density, the overpotentials of FeCoNi-S, CoFe-S, FeNi-S, and CoNi-S were 164, 377, 243, and 353 mV, respectively. This indicates that FeCoNi-S has the lowest overpotential and exhibits the best performance in hydrogen evolution through water electrolysis. The Tafel slope diagrams of the hydrogen evolution reaction of FeCoNi-S, CoFe-S, FeNi-S and CoNi-S prepared in Example 1 and Comparative Examples 1-3 are shown below. Figure 7 As shown, the Tafel slopes of FeCoNi-S, CoFe-S, FeNi-S, and CoNi-S are 112, 259, 123, and 145 mV dec, respectively. -1 This indicates that FeCoNi-S has the smallest Tafel slope and the fastest hydrogen evolution reaction kinetics.

[0020] In summary, the medium-entropy sulfides prepared in the embodiments of this invention possess abundant active sites and optimized electronic structures, significantly reducing the overpotential of hydrogen evolution and oxygen evolution reactions. These bifunctional medium-entropy sulfides are suitable for both hydrogen evolution and oxygen evolution reactions, simplifying the design of water electrolyzers. Furthermore, these medium-entropy Prussian blue analogue-derived sulfides utilize non-precious metals, have abundant raw materials, and employ a simple preparation process, facilitating large-scale production. The entire process generates no toxic emissions, meeting the requirements of green chemistry.

[0021] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a medium-entropy Prussian blue analogue-derived sulfide, characterized in that, Includes the following steps: Step 1: Dissolve Ni(NO3)2·6H2O and C6H5Na3O7·2H2O in deionized water and stir magnetically to form solution A; Step 2: Dissolve K3[Co(CN)6] and K3[Fe(CN)6] in deionized water and stir magnetically to form solution B; Step 3: Add solution B to solution A and stir at room temperature to obtain a mixed solution; Step 4: Heat the mixed solution in a water bath while stirring; Step 5: Centrifuge the mixed solution to separate the precipitate, wash it several times, and then vacuum dry it overnight to obtain the FeCoNi-PBA precursor; Step 6: Place the FeCoNi-PBA precursor and excess sulfur powder in two ceramic boats, respectively, and place them downstream and upstream of a tube furnace. Under an argon atmosphere, heat the furnace and then hold it at that temperature to obtain a medium-entropy sulfide, named FeCoNi-S.

2. The method for preparing intermediate-entropy Prussian blue analogue-derived sulfides according to claim 1, characterized in that, In step one, the molar ratio of Ni(NO3)2·6H2O and C6H5Na3O7·2H2O is 2:

3.

3. The method for preparing intermediate-entropy Prussian blue analogue-derived sulfides according to claim 1, characterized in that, In step two, the molar ratio of K3[Co(CN)6] to K3[Fe(CN)6] is 1:

1.

4. The method for preparing intermediate-entropy Prussian blue analogue-derived sulfides according to claim 1, characterized in that, In step four, the mixed solution is heated in a water bath and stirred. The specific process is as follows: the mixed solution is stirred in a water bath at 60°C for 12 hours.

5. The method for preparing intermediate-entropy Prussian blue analogue-derived sulfides according to claim 1, characterized in that, In step six, the process of heating and holding the temperature under an argon atmosphere is as follows: Under an argon atmosphere, the temperature is increased to 5°C per minute. -1 The temperature was increased to 500℃ at a certain rate and held at 500℃ for 2 hours.

6. A medium-entropy Prussian blue analogue-derived sulfide, characterized in that, It is prepared using any of the preparation methods described in claims 1-5.

7. A medium-entropy Prussian blue analogue-derived sulfide catalyst, characterized in that, The catalyst comprises the medium-entropy Prussian blue analogue-derived sulfide as described in claim 6.

8. The medium-entropy Prussian blue analogue-derived sulfide catalyst according to claim 7, characterized in that, The catalyst preparation method includes the following steps: mixing the medium-entropy Prussian blue analogue-derived sulfide, deionized water, anhydrous ethanol, and 5% naphthol solution, followed by ultrasonic treatment to obtain a slurry, and then drop-coating the slurry onto the working electrode.

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