Photoelectric catalyst and preparation method thereof
The dual-function catalyst of high entropy metal oxide sub-nanosheets was synthesized by solvothermal method, and the performance was improved by using light, which solved the problems of high ORR and OER reaction energy barrier and slow reaction kinetics in zinc-air batteries, and achieved improvement in battery performance.
Patent Information
- Application Number
- CN202311703965.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-12
- Publication Date
- 2025-06-13
AI Technical Summary
Existing zinc-air batteries have high reaction energy barriers and slow reaction kinetics in the ORR and OER reactions, making it difficult for battery performance to achieve high specific energy and long cycle life.
The high entropy metal oxide sub-nanosheet bifunctional catalyst was synthesized by solvothermal method, and the catalyst performance was improved by using light to solve the problems of high reaction energy barrier and slow reaction kinetics of ORR and OER.
The kinetic improvement of the ORR and OER reactions in zinc-air batteries is achieved, reducing the overpotential of the reaction, improving the specific energy and cycle life of the battery, and further improving the catalyst performance through light.
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Figure CN120149433A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of photoelectrochemical technology, and specifically relates to a photocatalyst and a preparation method thereof. Background Art
[0002] Currently, resource shortage and environmental pollution are still the most serious problems faced by mankind. Problems such as global warming and air pollution caused by the reduction of natural resources such as coal and oil and the large-scale combustion of non-renewable resources are intensifying day by day, forcing people to search for efficient, clean, green and pollution-free renewable energy to meet the growing demand for resources. Against the backdrop of carbon neutrality, renewable green energy such as wind energy, solar energy, and tidal energy has gradually gained a foothold in the energy field. However, this kind of renewable energy has problems such as uneven distribution and intermittency, and there are still huge challenges in the effective utilization of such new energy. Therefore, efficient and renewable energy conversion and storage devices have gradually attracted attention. Among them, fuel cells and metal-air batteries have become one of the key research and development goals for the development of a new generation of power batteries due to their high energy density.
[0003] Photoresponse batteries use electrons and holes generated by light to drive chemical reactions, which can effectively reduce the reaction overpotential. The effective combination of photoelectrochemistry will greatly improve the performance of the battery. The secondary zinc-air battery has gradually attracted wide attention from researchers due to its high theoretical specific energy (generally above 1000 Wh / kg) and clean pollution-free. During the charge and discharge process of the zinc-air battery, the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) alternate on the air electrode. Its electrochemical performance depends to a large extent on the reaction rates of ORR and OER. Its complex four-electron reaction makes its reaction energy barrier relatively high and the reaction kinetic process slow, which all lead to the difficulty of the battery performance to reach a high specific energy and long cycle life.
[0004] Due to the sluggish reaction kinetics of ORR and OER, catalytic materials need to be used to lower the energy barrier of the reaction. Currently, the internationally recognized most excellent ORR and OER catalysts are platinum-carbon and ruthenium dioxide respectively. However, due to their scarcity (only 9×10 -9 %) and single-functional catalytic activity, the wide application of such noble metal catalysts is limited.
[0005] Research findings show that due to the unique structure and properties of high-entropy metal oxides (such as high-entropy effect, cocktail effect, and lattice distortion), they exhibit great potential in catalysis and energy storage. Moreover, the multi-component nature of high-entropy metal oxides provides a vast design space for adjusting the electronic structure, elemental composition, and optimizing the binding energy. However, high-entropy metal oxides synthesized by conventional high-temperature and high-pressure methods are generally bulk materials, reducing the number of their active sites and greatly limiting their catalytic performance and stability.
[0006] Therefore, developing a mild synthesis method to obtain ORR and OER high-entropy metal oxide catalyst materials with abundant active sites is a very important research task. Summary of the Invention
[0007] To address the above deficiencies in the art, the present application aims to provide a photocatalyst and its preparation method. By using a solvothermal method, a bifunctional catalyst of high-entropy metal oxide sub-nanosheets with abundant active sites is synthesized, and the catalyst performance is enhanced through light irradiation means to meet the requirements of bifunctional catalysis for metal-air batteries.
[0008] On the one hand, the present application provides a photocatalyst, comprising a high-entropy metal oxide nanosheet material,
[0009] The sheet material includes: a metal oxide active component and a phosphomolybdic acid carrier:
[0010] Among them, the metal oxide active component includes: four or more of cobalt, iron, nickel, manganese, copper, and zinc;
[0011] The molar ratio of the metal oxide active component to the phosphomolybdic acid carrier is (10 - 14):1.
[0012] According to some embodiments of the present application, the thickness of the sheet material is: 0.8 - 1.2 nm.
[0013] According to some embodiments of the present application, the metal active component includes: nickel, manganese, copper, and zinc, and the mass ratio of nickel, manganese, copper, and zinc is 1:(1 - 4):(1 - 4):(1 - 4);
[0014] Or,
[0015] iron, nickel, manganese, copper, and zinc, and the mass ratio of iron, nickel, manganese, copper, and zinc is (1 - 5):1:(1 - 5):(1 - 5):(1 - 5);
[0016] Or,
[0017] cobalt, iron, nickel, manganese, copper, and zinc, and the mass ratio of cobalt, iron, nickel, manganese, copper, and zinc is (1 - 6):(1 - 6):1:(1 - 6):(1 - 6):(1 - 6).
[0018] According to some embodiments of the present application, the metal active component includes: cobalt, iron, nickel, manganese, copper, and zinc.
[0019] According to another aspect of the present application, a method for preparing a photocatalyst is provided, including: adding at least four of cobalt salt, iron salt, nickel salt, manganese salt, copper salt, and zinc salt to a solvent, and reacting with phosphomolybdic acid by a solvothermal method to obtain the photocatalyst.
[0020] The molar ratio of the metal oxide active component to the phosphomolybdic acid support is (10 - 14):1.
[0021] According to some embodiments of the present application, the solvothermal method includes:
[0022] Adding at least four of cobalt salt, iron salt, nickel salt, manganese salt, copper salt, and zinc salt to a solvent to dissolve, obtaining a mixed solution;
[0023] Adding the phosphomolybdic acid and the mixed solution to a polytetrafluoroethylene inner liner, mixing evenly, and then adding oleylamine and n - hexane for reaction.
[0024] According to some embodiments of the present application, the solvent is an ethanol solution.
[0025] According to some embodiments of the present application, the reaction is carried out in a high - pressure reaction kettle.
[0026] According to some embodiments of the present application, the reaction temperature is 140 - 180 °C, and the reaction time is 4 - 8 h.
[0027] According to some embodiments of the present application, the salt compounds include: cobalt chloride, iron nitrate, nickel chloride, manganese chloride, copper nitrate, and zinc nitrate;
[0028] Preferably, the combination of the salt compounds includes: nickel chloride, manganese chloride, copper nitrate, and zinc nitrate;
[0029] Or, iron nitrate, nickel chloride, manganese chloride, copper nitrate, and zinc nitrate;
[0030] Or, cobalt chloride, iron nitrate, nickel chloride, manganese chloride, copper nitrate, and zinc nitrate.
[0031] Compared with the prior art, the present application has at least the following beneficial effects:
[0032] This application provides a photocatalyst, which is a high-entropy metal oxide sub-nanosheet material. The catalyst material of this application can solve the problems of high reaction energy barriers and slow reaction kinetics in the ORR and OER reactions. The photocatalyst of this application has a structure with a size less than 1 nm, which enables the material to expose more active sites, and due to the entropy modulation effect of the high-entropy material, it has excellent catalytic performance.
[0033] The preparation process of this application is simple, the required raw materials are abundant, the price is low, the synthesis cycle is short, and the output is high. Description of the Drawings
[0034] Figures 1-3 It is the detection diagram of the exemplary embodiment of this application.
[0035] Figure 4 It is the detection diagram of the application example of this application.
[0036] Figure 5 It is the electron microscopy image of CFNMCZ-PMA dispersed in ethanol in the exemplary embodiment of this application.
[0037] Figure 6 It is the detection diagram of the comparative example of the example of this application. Detailed Description of the Invention
[0038] Next, the technical solutions of this application will be clearly and completely described in conjunction with the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, rather than all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of this application.
[0039] It should be particularly noted that similar substitutions and modifications made to this application are obvious to those skilled in the art, and they are all considered to be included in this application. Relevant personnel can obviously make changes or appropriate changes and combinations to the methods and applications described herein without departing from the content, spirit and scope of this application to implement and apply the technology of this application. Obviously, the described embodiments are only part of the embodiments of this application, rather than all of them.
[0040] If no specific conditions are indicated in this application, they are all carried out according to conventional conditions or conditions recommended by the manufacturer. For the raw materials or excipients used, and for the reagents or instruments used, if the manufacturer is not indicated, they are all conventional products that can be obtained through commercial purchase.
[0041] The following is a detailed description of this application.
[0042] In view of the problems of high reaction energy barrier and slow reaction kinetics caused by the complex four-electron reaction during the reaction process of zinc-air batteries, this application prepares a bifunctional catalyst with excellent performance, reduces the overpotential of the reaction, improves the reaction kinetics, and further enhances the performance by introducing light.
[0043] This application provides a high-entropy oxide sub-nanosheet material and a preparation method thereof, which solves the problems of high reaction energy barriers for ORR and OER and slow reaction kinetics. Moreover, the preparation method has the advantages of simple process, abundant raw materials, low price, short synthesis cycle, high yield, etc. At the same time, the sub-nano structure enables the material to expose more active sites, and due to the entropy modulation effect of the high-entropy material, it has excellent catalytic performance.
[0044] The technical solutions are as follows:
[0045] (1) Dissolve cobalt chloride, iron nitrate, nickel chloride, manganese chloride, copper nitrate, and zinc nitrate in an ethanol solution and ultrasonically dissolve them evenly.
[0046] (2) Put phosphomolybdic acid into a polytetrafluoroethylene inner liner, add the solution in (1), stir, and after forming a homogeneous solution, add oleylamine and n-hexane, and place it in a hydrothermal autoclave for reaction.
[0047] (3) Transfer the obtained product out of the polytetrafluoroethylene inner liner with ethanol, and wash the product twice with cyclohexane and ethanol.
[0048] (4) The synthesis processes of the five-component and four-component materials are similar to the above, the difference being that NMCZ-PMA does not add cobalt chloride and iron nitrate, and at the same time adjusts the amount of phosphomolybdic acid, and FNMCZ-PMA does not add cobalt chloride and also adjusts the amount of phosphomolybdic acid.
[0049] The following combines specific examples to introduce the technical solutions of this application in detail.
[0050] Example 1
[0051] Prepare the six-component photocatalyst of this application.
[0052] Respectively take 1 mmol of cobalt chloride, iron nitrate, nickel chloride, manganese chloride, copper nitrate, and zinc nitrate and dissolve them in 2 ml of ethanol solution, and ultrasonically dissolve them evenly to obtain a mixed solution;
[0053] Put 0.09 g of phosphomolybdic acid into a 10 ml polytetrafluoroethylene inner liner, add the mixed solution, stir for 10 min, and after forming a homogeneous solution, add 1.9 ml of oleylamine and 6 ml of n-hexane, and place it in a high-pressure autoclave for reaction at 140 °C for 4 h;
[0054] Transfer the obtained product out of the polytetrafluoroethylene liner with ethanol, and wash the product twice with cyclohexane and ethanol to obtain CFNMCZ-PMA.
[0055] Example 2
[0056] Prepare the five-component photocatalyst of the present application.
[0057] Weigh 1 mmol of iron nitrate, nickel chloride, manganese chloride, copper nitrate, and zinc nitrate respectively and dissolve them in 2 ml of ethanol solution. Ultrasonically dissolve them to obtain a mixed solution.
[0058] Put 0.072 g of phosphomolybdic acid into a 10 ml polytetrafluoroethylene liner, add the mixed solution, stir for 10 min. After forming a homogeneous solution, add 1.9 ml of oleylamine and 6 ml of n-hexane, and place it in an autoclave to react at 140 °C for 4 h.
[0059] Transfer the obtained product out of the polytetrafluoroethylene liner with ethanol, and wash the product twice with cyclohexane and ethanol to obtain the FNMCZ-PMA catalyst.
[0060] Example 3
[0061] Prepare the four-component photocatalyst of the present application.
[0062] Weigh 1 mmol of nickel chloride, manganese chloride, copper nitrate, and zinc nitrate respectively and dissolve them in 2 ml of ethanol solution. Ultrasonically dissolve them to obtain a mixed solution.
[0063] Put 0.054 g of phosphomolybdic acid into a 10 ml polytetrafluoroethylene liner, add the mixed solution, stir for 10 min. After forming a homogeneous solution, add 1.9 ml of oleylamine and 6 ml of n-hexane, and place it in an autoclave to react at 140 °C for 4 h.
[0064] Transfer the obtained product out of the polytetrafluoroethylene liner with ethanol, and wash the product twice with cyclohexane and ethanol to obtain the NMCZ-PMA catalyst.
[0065] Comparative Example 1
[0066] Prepare the photocatalyst of the present application without adding phosphomolybdic acid.
[0067] The preparation method is the same as that of Example 1, except that phosphomolybdic acid is not added, and it is named NMCZ.
[0068] Comparative Example 2
[0069] Prepare the photocatalyst of the present application without adding phosphomolybdic acid.
[0070] The preparation method is the same as that of Example 2, except that phosphomolybdic acid is not added, and it is named FNMCZ.
[0071] Comparative Example 3
[0072] Prepare the photocatalyst of the present application without adding phosphomolybdic acid.
[0073] The preparation method is the same as that of Example 3, except that phosphomolybdic acid is not added, and it is named CFNMCZ.
[0074] Experimental Example
[0075] 1. Characterize the catalyst materials of Examples 1 - 3, and the characterization results are as Figure 1 、 Figure 2 shown.
[0076] Among them, Figure 1 a - c are TEM images of NMCZ - PMA, FNMCZ - PMA, CFNMCZ - PMA; Figure 1 d - f are HAADF - STEM images of NMCZ - PMA, FNMCZ - PMA, CFNMCZ - PMA; Figure 1 g is the AFM image of NMCZ - PMA; Figure 1 h is the SAXRD image of CFNMCZ - PMA; Figure 1 i is the FT - EXAFS image of CFNMCZ - PMA; Figure 1 j - k are the EDS elemental mapping images of NMCZ - PMA, FNMCZ - PMA, CFNMCZ - PMA, Figure 2 and is the AFM image of CFNMCZ - PMA.
[0077] According to Figure 1 a - f, it can be seen that the catalyst materials prepared in the examples of the present application are uniform in shape and size, and there are almost no impurity phases.
[0078] According to Figure 1 the AFM results, the thickness of the nanosheets in Example 3 is determined to be about 1.2 nm.
[0079] According to Figure 1 h, the existence of the periodic layered structure of the catalyst material in Example 1 can be clearly reflected. At the same time, according to the Bragg equation, the interlayer spacing of the material is calculated to be 1.17 nm, which is Figure 2 consistent with the AFM results, further proving the successful preparation of the two - dimensional sub - 1nm structure.
[0080] According to Figure 1As shown in i, the local structures and chemical environments of elements Co, Fe, Ni, and Mn in CFNMCZ-PMA are similar, demonstrating that it meets the definition of high-entropy materials (the contents of Cu and Zn in CFNMCZ-PMA are too low to be accurately detected, so only the results of the other four elements are shown).
[0081] According to Figure 1 As shown in j-k, the EDS element mapping diagrams show the uniform distribution of each element in the catalysts of Examples 1-3 of this application - two-dimensional high-entropy sub-nanosheet materials.
[0082] Among them, when detecting the EDS element mapping diagrams, considering that when the high-entropy sub-nanosheet materials are dispersed in a good solvent (cyclohexane), the thickness of a single high-entropy sub-nanosheet material is too thin, resulting in a low element signal. Therefore, the materials are dispersed in a poor solvent (ethanol) to obtain aggregates of the materials to obtain a stronger element signal. As Figure 5 shown, it is the electron micrograph of CFNMCZ-PMA dispersed in ethanol.
[0083] 2. The catalyst materials of Examples 1-3 were tested, and the test results are as Figure 3 shown
[0084] Figure 3 (a) are the LSV curves of OER of NMCZ-PMA, FNMCZ-PMA, and CFNMCZ-PMA in 1M KOH electrolyte under illumination and non-illumination conditions; Figure 3 (b) is the Tafel slope corresponding to OER; Figure 3 (c) is the EPR of OH·; Figure 3 (d) is the ORR polarization curve in 0.1M KOH electrolyte; Figure 3 (e) is the Tafel slope corresponding to ORR; Figure 3 (f) are the overall polarization curves of ORR and OER and their ΔE.
[0085] In 1M KOH electrolyte, under illumination and non-illumination conditions, the linear sweep voltammetry curves of OER with a scanning rate of 5mV s -1 were tested. According to Figure 3 a, it was found that after introducing illumination, the CFNMCZ-PMA electrode showed a higher current response and had a lower overpotential at 10mAcm -2 .
[0086] At 10mA cm -2At the current density, the overpotentials of the high-entropy sub-nanosheets of Examples 1-3 under light illumination were 296, 221, and 165 mV, respectively, all lower than those under dark conditions. Compared with NMCZ-PMA and FNMCZ-PMA, CFNMCZ-PMA had the lowest overpotential.
[0087] According to Figure 3 the b Tafel curve, under light illumination, the Tafel slope of CFNMCZ-PMA (71.4 mV dec -1 ) was smaller than that of NMCZ-PMA (98.9 mV dec -1 ) and FNMCZ-PMA (137.6 mV dec -1 ), indicating faster OER kinetics.
[0088] As described above, the role of light significantly improved the catalytic performance. To verify the role of light, the electron paramagnetic resonance (EPR) results of OH· under alternating light and dark conditions were tested in this experimental example. The results showed that OH· was formed by OH - accepting highly oxidized photo-generated holes under light illumination ( Figure 3 c).
[0089] According to Figure 3 d, the ORR performance polarization curve showed that CFNMCZ-PMA had a higher half-wave potential (E 1 / 2 )(0.802 V) than NMCZ-PMA and FNMCZ-PMA.
[0090] According to Figure 3 e, the Tafel slopes of NMCZ-PMA, FNMCZ-PMA, and CFNMCZ-PMA under light illumination were 67.8, 83.7, and 130.5 mV dec -1 , respectively.
[0091] To evaluate the bifunctional activity, Figure 3 f calculated the voltage difference (ΔE) between the OER potential and the ORR half-wave potential at 10 mA cm -2 . The ΔE value of CFNMCZ-PMA under light illumination was the smallest at ≈0.591 V, much lower than that of NMCZ-PMA (0.871 V) and FNMCZ-PMA (0.696 V).
[0092] Through the above ORR and OER performance tests, the present application compared the catalytic performances of sub-nanosheet materials with four components, five components, and six components, and found that by precisely regulating the added metal elements, the catalytic performance can be improved. Moreover, on this basis, light was further introduced to further improve the material performance. The photoelectrocatalyst of the present application was tested for ORR and OER performances in an alkaline potassium hydroxide solution. The CFNMCZ-PMA catalyst material has a smaller oxygen evolution overpotential (165 mV) and a higher half-wave potential (0.802 V).
[0093] 3. Test the catalyst materials of the comparative examples, and the test results are as Figure 6 shown
[0094] Figure 6 Catalytic performance comparison of the catalyst materials NMCZ, FNMCZ, CFNMCZ and NMCZ-PMA, FNMCZ-PMA, CFNMCZ-PMA for Comparative Examples 1-3 (a) ORR, (b) OER.
[0095] Through performance comparison, the present application found that the materials with phosphomolybdic acid added have obvious advantages over the materials without phosphomolybdic acid added. It can be seen that the performance of NMCZ-PMA in the examples is slightly worse in OER, but under light, NMCZ-PMA, FNMCZ-PMA, and CFNMCZ-PMA are superior to the comparative example materials in terms of the maximum current density and the overpotential at 10 mA cm -2 . Under light, the ORR of NMCZ-PMA, FNMCZ-PMA, and CFNMCZ-PMA is also superior to the comparative materials in terms of the limiting current density and the half-wave potential.
[0096] Application Example
[0097] Prepare zinc-air batteries using the catalyst materials of the examples and comparative examples.
[0098] Among them, Figure 4 (a) Picture of charging a mobile phone by connecting four zinc-air batteries in series, Figure 4 (b) Discharge rate performance at different current densities; Figure 4 (c) Constant current charge-discharge curves under light and without light conditions at a current density of 2 mA cm -2 ; Figure 4 (d) Discharge polarization curve and corresponding power-current density curve of the zinc-air battery.
[0099] In order to explore the potential applications of zinc-air batteries in various electronic devices, in this application example, four zinc-air batteries were connected in series to achieve the charging of a mobile phone, as Figure 4 shown in a.
[0100] Figure 4 b shows the discharge rate curves of the zinc-air battery and the high-entropy sub-nanosheet material based on Pt / C + RuO -2 ) at different current densities (1 to 10 mA cm 2 . Relatively speaking, CFNMCZ-PMA has the highest discharge voltage, even higher than that of commercial Pt / C + RuO 2 , and has a stable discharge platform.
[0101] According to Figure 4 c, the charge-discharge polarization curves of the light-promoted zinc-air battery with the high-entropy sub-nanosheet material as the air electrode in the presence / absence of light mode. Under illumination, the discharge voltage of CFNMCZ-PMA significantly increases to 1.33 V, and the charge voltage significantly decreases to 1.58 V. Specifically, the charge-discharge voltage gap of CFNMCZ-PMA is small, indicating its good rechargeability and round-trip efficiency.
[0102] According to Figure 4 d, the power density test was also carried out. The peak power density of CFNMCZ-PMA is ≈102.4 mW cm -2 , higher than that of Pt / C + RuO 2 (≈63.1 mW cm -2 ).
[0103] The description of the above embodiments is only used to help understand the method and its core idea of the present application. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.
Claims
1. A photocatalyst, characterized in that, it comprises a high-entropy metal oxide nanosheet material, and the sheet material comprises: a metal oxide active component and a phosphomolybdic acid carrier: wherein, the metal oxide active component comprises: four or more of cobalt, iron, nickel, manganese, copper, and zinc; the molar ratio of the metal oxide active component to the phosphomolybdic acid carrier is (10-14):
1.
2. The photocatalyst according to claim 1, characterized in that, the thickness of the sheet material is: 0.8-1.2 nm.
3. The photocatalyst according to claim 1, characterized in that, the metal active component comprises: nickel, manganese, copper, and zinc, and the mass ratio of nickel, manganese, copper, and zinc is 1:(1-4):(1-4):(1-4); or, iron, nickel, manganese, copper, and zinc, and the mass ratio of iron, nickel, manganese, copper, and zinc is (1-5):1:(1-5):(1-5):(1-5); or, cobalt, iron, nickel, manganese, copper, and zinc, and the mass ratio of cobalt, iron, nickel, manganese, copper, and zinc is (1-6):(1-6):1:(1-6):(1-6):(1-6).
4. The photocatalyst according to claim 1, characterized in that, the metal active component comprises: cobalt, iron, nickel, manganese, copper, and zinc.
5. A preparation method of a photocatalyst, characterized in that, at least four kinds of salt compounds of cobalt salt, iron salt, nickel salt, manganese salt, copper salt, and zinc salt are taken and added to a solvent, and reacted with phosphomolybdic acid by a solvothermal method to obtain; the molar ratio of the metal oxide active component to the phosphomolybdic acid carrier is (10-14):
1.
6. The preparation method according to claim 5, characterized in that, the solvothermal method comprises: taking at least four of cobalt salt, iron salt, nickel salt, manganese salt, copper salt, and zinc salt and adding them to a solvent to dissolve to obtain a mixed solution; adding phosphomolybdic acid and the mixed solution to a polytetrafluoroethylene inner liner, mixing evenly, and then adding oleylamine and n-hexane for reaction.
7. The preparation method according to claim 6, characterized in that, the solvent is an ethanol solution.
8. The preparation method according to claim 6, characterized in that, the reaction is carried out in a high-pressure reactor.
9. The preparation method according to claim 8, characterized in that, the reaction temperature is 140-180 °C, and the reaction time is 4-8 h.
10. The preparation method according to claim 6, characterized in that, the salt compounds include: cobalt chloride, iron nitrate, nickel chloride, manganese chloride, copper nitrate, and zinc nitrate; preferably, the combination of the salt compounds includes: nickel chloride, manganese chloride, copper nitrate, and zinc nitrate; or, iron nitrate, nickel chloride, manganese chloride, copper nitrate, and zinc nitrate; or, cobalt chloride, iron nitrate, nickel chloride, manganese chloride, copper nitrate, and zinc nitrate.