A lignin-derived oxygen reduction / oxygen evolution dual-function electrocatalyst material, preparation method, and application thereof

Abstract

The present invention relates to the field of carbon-based catalysts and electrocatalysis technology, and specifically to the preparation and application of a lignin-derived oxygen reduction / oxygen evolution bifunctional electrocatalyst material. The present invention solves the problems of high cost, poor stability, and single function of catalysts formed by conventional technologies. The present invention comprises an oxygen reduction / oxygen evolution bifunctional electrocatalyst material, which is composed of sulfate lignin powder, sodium chloride, urea, and nitrate solution, wherein the mass ratio of sulfate lignin powder, sodium chloride, urea, and nitrate solution is 1:5:5:100. The present invention uses sulfate lignin as a carbon substrate, NaCl for pore formation, urea as a nitrogen source, and iron nitrate nonahydrate and nickel nitrate hexahydrate as Fe and Ni sources, respectively, to prepare a lignin-derived carbon-based bifunctional oxygen electrocatalyst that is co-doped with S and N and loaded with Fe and Ni bimetallics.

Description

Technical Field

[0001] The present invention relates to the field of carbon-based catalysts and electrocatalytic technology, and in particular to the preparation and application of a lignin-derived oxygen reduction / oxygen evolution dual-function electrocatalyst material. Background Art

[0002] Lignin, one of the three major components of wood, is the most difficult to degrade and transform due to its complex chemical structure and composition. Large quantities of this material are discharged as pulp waste in the industrial sector, causing environmental pollution and resource waste. The main components of pulp waste are sulfonate lignin and sulfate lignin. Sulfonate lignin is currently commercially available, while sulfate lignin, due to its unknown composition and structure, still lacks suitable recycling methods. Lignin-derived carbon materials, due to their high stability, high conductivity, high specific surface area, and controllability, can be applied in electrochemistry to achieve efficient utilization of lignin. This can transform industrial lignin waste into valuable resources, achieving a natural benefit. Electrochemical energy, due to its clean and efficient properties, is emerging as a promising alternative to traditional fossil fuels. Within this field, metal-air batteries (MABs) have attracted significant attention due to their exceptional high energy density and excellent energy conversion efficiency, showing great potential as an alternative to traditional secondary batteries. However, their development faces a bottleneck: the relatively slow kinetics of the ORR and OER processes. Addressing this bottleneck is crucial for promoting the commercialization of MABs.

[0003] Currently commercial precious metal-based catalysts have poor stability, single catalytic function and high cost. There is an urgent need for an oxygen electrocatalyst with bifunctional catalytic activity and low price.

[0004] Therefore, it is urgent to propose a lignin-derived oxygen reduction / oxygen evolution dual-functional electrocatalyst material and preparation method to solve the above technical problems. Summary of the Invention

[0005] The present invention was developed to address the high cost, poor stability, and limited functionality of catalysts produced using conventional techniques. A brief overview of the present invention is provided below to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to identify key or essential aspects of the present invention, nor is it intended to limit the scope of the present invention.

[0006] The technical solution of the present invention:

[0007] A lignin-derived oxygen reduction / oxygen evolution bifunctional electrocatalyst material, the oxygen reduction / oxygen evolution bifunctional electrocatalyst material comprising kraft lignin powder, sodium chloride, urea and nitrate solution;

[0008] The mass ratio of kraft lignin powder, sodium chloride, urea and nitrate solution is 1:5:5:100.

[0009] Preferably, the nitrate solution is one or more of ferric nitrate solution and nickel nitrate solution.

[0010] A method for preparing a lignin-derived oxygen reduction / oxygen evolution dual-function electrocatalyst material comprises the following steps:

[0011] Step 1: Add deionized water, Fe(NO3)3·9H2O, and Ni(NO3)2·6H2O into a beaker and stir thoroughly to obtain a nitrate solution;

[0012] Step 2: Weigh kraft lignin powder, sodium chloride and urea, add them to the nitrate solution, and stir thoroughly to dissolve the suspension;

[0013] Step 3: Evaporating the suspension to dryness by rotary evaporation, and then vacuum drying to obtain a kraft lignin precursor;

[0014] Step 4: The kraft lignin precursor is subjected to high-temperature carbonization in a tubular furnace, grinding, filtering, and drying to obtain lignin-based nanocarbon materials.

[0015] Preferably: the metal ion concentration in the nitrate solution is 0.01 mol L -1 .

[0016] Preferably, the molar ratio of Fe(NO3)3·9H2O to Ni(NO3)2·6H2O is one of 1:9, 3:7, and 5:5, or it is a ferric nitrate solution or a nickel nitrate solution.

[0017] Preferably, the rotary evaporation temperature is 65°C.

[0018] Preferably, the vacuum drying temperature is 60° C. and the time is 12 hours.

[0019] A method for preparing a lignin-derived oxygen reduction / oxygen evolution dual-functional electrocatalyst material-loaded electrode comprises the following steps:

[0020] Step 1: Take 5 mg of lignin-based nanocarbon material and put it into a 5 ml centrifuge tube, add 1 ml of isopropanol and 20 μL of naphthol, and sonicate for 90 min until the dispersion is uniformly dissolved to prepare a carbon slurry;

[0021] Step 2: For the oxygen reduction reaction, use a pipette to evenly drop the slurry onto the surface of the rotating disk electrode, dropping 5 μL at a time for a total of four times, and allow to air-dry to obtain a catalyst-loaded electrode. For the oxygen evolution reaction, use a pipette to evenly drop the slurry onto both sides of a 1 cm × 1 cm piece of carbon paper, dropping 10 μL at a time, five times on both sides, and allow to air-dry to obtain a catalyst-loaded electrode.

[0022] The invention relates to the application of a lignin-derived oxygen reduction / oxygen evolution dual-functional electrocatalyst material in a standard three-electrode system cathode oxygen reduction reaction, wherein the reference electrode of the standard three-electrode system oxygen reduction reaction is an Ag / AgCl electrode, the working electrode is a disc electrode loaded with an electrocatalyst, and the counter electrode is a Pt mesh electrode;

[0023] In the standard three-electrode system anodic oxygen evolution reaction, the reference electrode is an Ag / AgCl electrode, and the working electrode is a 1 cm2 electrocatalyst loaded anodic oxygen evolution reaction. 2 Carbon paper, the counter electrode is a Pt mesh electrode.

[0024] The present invention has the following beneficial effects:

[0025] The present invention uses kraft lignin as a carbon substrate, NaCl for pore formation, urea as a nitrogen source, ferric nitrate nonahydrate and nickel nitrate hexahydrate as Fe and Ni sources, respectively, to prepare a S, N co-doped, Fe, Ni bimetallic-loaded lignin-derived carbon-based bifunctional oxygen electrocatalyst.

[0026] The present invention uses abundant, readily available, and low-cost kraft lignin as a raw material instead of expensive precious metals, which reduces manufacturing costs and is expected to achieve the recycling of industrial papermaking waste.

[0027] The present invention adopts N, S co-doping and Ni, Fe bimetallic loading strategies to effectively improve the ORR / OER catalytic performance of lignin carbon materials and greatly simplify the production difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the specific technical roadmap of the present invention;

[0029] Figure 2 1 and 2 are XRD spectra of Examples 1 and 2 of the present invention;

[0030] Figure 3 CV curves of Example 1 and Example 2 of the present invention under N2 and O2 gases;

[0031] Figure 4 1 is a comparison diagram of the LSV polarization curves of Example 1 and Example 2 of the present invention at a rotation speed of 1600 rpm;

[0032] Figure 5 It is the ORR Tafel curve of Example 1 and Example 2;

[0033] Figure 6 1 is a comparison diagram of the LSV polarization curves of the oxygen evolution reaction of Example 1 and Example 2;

[0034] Figure 7It is the OER Tafel curve of Example 1 and Example 2;

[0035] Figure 8 Ni of Example 2 0.7 Fe 0.3 -SNC SEM and corresponding element mapping diagrams;

[0036] Figure 9 Ni in Example 2 0.7 Fe 0.3- RRDE curve of SNC at 1600 rpm and graph of electron transfer number and H2O2 yield;

[0037] Figure 10 Ni in Example 2 0.7 Fe 0.3- It curves of SNC and commercial Pt / C after 20000s;

[0038] Figure 11 Ni in Example 2 0.7 Fe 0.3- LSV comparison chart before and after 1000 SNC cycles;

[0039] Figure 12 Ni in Example 2 0.7 Fe 0.3- Schematic diagram of the Zn-air battery assembled by SNC lighting up the LED light;

[0040] Figure 13 This is a test curve chart related to the Zn-air battery assembled with Ni0.7Fe0.3-SNC in Example 2.

[0041] Figure 2 Figure a is the XRD spectra of Fe-SNC and Ni-SNC, and Figure b is the XRD spectra of Ni 0.9 Fe 0.1 -SNC, Ni 0.7 Fe 0.3 -SNC, Ni 0.5 Fe 0.5 -XRD spectrum of SNC, Figure 4 Figure a in the middle shows Ni-SNC, Fe-SNC and Ni 0.7 Fe 0.3 -Comparison of LSV polarization curves of SNC at 1600 rpm, Figure b is Ni 0.9 Fe 0.1 -SNC, Ni 0.7 Fe 0.3 -SNC, Ni 0.5 Fe 0.5 -Comparison of LSV polarization curves of SNC at 1600rpm, Figure 6 Figure a in the middle shows Fe-SNC, Ni-SNC, Ni 0.7 Fe 0.3 -SNC measured the LSV polarization curve of OER, b is Ni 0.9 Fe 0.1 -SNC, Ni 0.7 Fe 0.3 -SNC and Ni 0.5 Fe 0.5 -SNC measured the LSV polarization curve of OER, Figure 9 Figure a in the middle shows Ni at 1600rpm 0.7 Fe 0.3 -LSV curves of SNC rotating disk electrode, Figure b is Ni 0.7 Fe 0.3 -Electron transfer number and H2O2 yield of SNC-catalyzed oxygen reduction reaction, Figure 13 Figure a is the battery polarization curve and power density curve; Figure b is the open circuit voltage; Figure c is the rate charge and discharge curve; Figure d is the specific capacity test curve; Figure e is the charge and discharge cycle curve. DETAILED DESCRIPTION

[0042] To make the objectives, technical solutions, and advantages of the present invention more clearly apparent, the present invention is described below using specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely illustrative and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0043] Specific implementation method 1: Combination Figures 1-13 This embodiment describes a lignin-derived oxygen reduction / oxygen evolution bifunctional electrocatalyst material, wherein the oxygen reduction / oxygen evolution bifunctional electrocatalyst material is composed of kraft lignin powder, sodium chloride, urea, and nitrate solution;

[0044] The mass ratio of kraft lignin powder, sodium chloride, urea and nitrate solution is 1:5:5:100.

[0045] Specific implementation method 2: Combination Figures 1-13 This embodiment describes a lignin-derived oxygen reduction / oxygen evolution bifunctional electrocatalyst material, and the nitrate solution is one or more of a ferric nitrate solution and a nickel nitrate solution.

[0046] 0.2908 g of nickel nitrate hexahydrate (0.001 mol) and 0.4040 g of ferric nitrate nonahydrate (0.001 mol) were weighed separately, added into 100 mL of ultrapure water to dissolve, and stirred thoroughly to obtain nickel nitrate aqueous solution and ferric nitrate aqueous solution, respectively.

[0047] Weigh a total of 0.0001 mol of nickel nitrate hexahydrate and ferric nitrate nonahydrate, measure 100 mL of deionized water and add it to a beaker, stir thoroughly to dissolve and prepare a 100 g mixed aqueous solution of ferric nitrate and nickel nitrate, and the molar ratio of Fe(NO3)3·9H2O and Ni(NO3)2·6H2O is one of 1:9, 3:7, and 5:5.

[0048] Specific implementation method three: Combination Figures 1-13 This embodiment describes a method for preparing a lignin-derived oxygen reduction / oxygen evolution dual-functional electrocatalyst material, comprising the following steps:

[0049] Step 1: Add deionized water, Fe(NO3)3·9H2O, and Ni(NO3)2·6H2O into a beaker and stir thoroughly to obtain a nitrate solution;

[0050] Step 2: Weigh kraft lignin powder, sodium chloride and urea, add them to the nitrate solution, and stir thoroughly to dissolve the suspension;

[0051] Step 3: Evaporating the suspension to dryness by rotary evaporation, and then vacuum drying to obtain a kraft lignin precursor;

[0052] Step 4: The kraft lignin precursor is subjected to high-temperature carbonization in a tubular furnace, grinding, filtering, and drying to obtain lignin-based nanocarbon materials.

[0053] The lignin-based nanocarbon materials prepared according to the above method are sulfur-nitrogen co-doped, the single metal-loaded lignin-based catalysts Fe-SNC, Ni-SNC and sulfur-nitrogen co-doped, the bimetallic-loaded lignin-based catalyst Ni 0.9 Fe 0.1 -SNC、Ni 0.7 Fe 0.3 -SNC、Ni 0.5 Fe 0.5 -SNC.

[0054] The method for preparing the nitrate solution in step 1 is to weigh 0.001 mol of Fe(NO3)3·9H2O and Ni(NO3)2·6H2O in a beaker, measure 100 mL of deionized water and add it to the beaker, stir thoroughly to dissolve and prepare 100 g of nitrate aqueous solution.

[0055] In the filtration process in step 4, the filtration solution used is deionized water, and the drying temperature in step 4 is 60°C.

[0056] Specific implementation method four: Combination Figures 1-13 This embodiment describes a method for preparing a lignin-derived oxygen reduction / oxygen evolution dual-function electrocatalyst material. The metal ion concentration in the nitrate solution is 0.01 mol / L -1.

[0057] Specific implementation method five: Combination Figures 1-13 This embodiment describes a method for preparing a lignin-derived oxygen reduction / oxygen evolution dual-functional electrocatalyst material, wherein the rotary evaporation temperature is 65°C.

[0058] Specific implementation method six: combination Figures 1-13 This embodiment describes a method for preparing a lignin-derived oxygen reduction / oxygen evolution bifunctional electrocatalyst material, wherein the vacuum drying temperature is 60° C. and the drying time is 12 hours.

[0059] Specific implementation method seven: combination Figures 1-13 This embodiment describes a method for preparing a lignin-derived oxygen reduction / oxygen evolution dual-function electrocatalyst material. The high-temperature carbonization in a tubular furnace is carried out under an argon atmosphere at a heating rate of 5°C min -1 The temperature is 900℃ and the time is 2h.

[0060] Specific implementation method eight: combination Figures 1-13 This embodiment describes a method for preparing a lignin-derived oxygen reduction / oxygen evolution dual-functional electrocatalyst-loaded electrode, comprising the following steps:

[0061] Step 1: Take 5 mg of lignin-based nanocarbon material and put it into a 5 ml centrifuge tube, add 1 ml of isopropanol and 20 μL of naphthol, and sonicate for 90 min until the dispersion is uniformly dissolved to prepare a carbon slurry;

[0062] Step 2: During the oxygen reduction reaction, use a pipette to evenly drop the slurry onto the surface of the rotating disk electrode, 5 μL each time, for a total of 4 drops, and wait for it to dry naturally to obtain a catalyst-loaded electrode;

[0063] In the oxygen evolution reaction, the carbon paper was cut into 1 cm × 1 cm size, and the slurry was evenly applied on both sides of the carbon paper using a pipette, 10 μL each time, 5 drops on each side, and then waited for natural air drying to obtain the catalyst-loaded electrode.

[0064] Specific implementation method nine: combination Figures 1-13 This embodiment describes the application of a lignin-derived oxygen reduction / oxygen evolution bifunctional electrocatalyst material in a standard three-electrode system cathode oxygen reduction reaction, wherein the standard three-electrode system oxygen reduction reaction reference electrode is an Ag / AgCl electrode, the working electrode is a disc electrode loaded with an electrocatalyst, and the counter electrode is a Pt mesh electrode;

[0065] In the standard three-electrode system anodic oxygen evolution reaction, the reference electrode is an Ag / AgCl electrode, and the working electrode is a 1 cm2 electrocatalyst loaded anodic oxygen evolution reaction. 2Carbon paper, the counter electrode is a Pt mesh electrode.

[0066] Example 1

[0067] Step 1: Weigh 0.3 g of nickel nitrate hexahydrate (metal ion concentration of 0.001 mol) and 0.4 g of ferric nitrate nonahydrate (metal ion concentration of 0.001 mol) into two round-bottom flasks, add 100 ml of ultrapure water to each flask, and stir thoroughly to dissolve and prepare 100 ml of nitrate solution.

[0068] Step 2: Weigh 1 g of kraft lignin powder, 5 g of urea, and 5 g of NaCl respectively and add them to the above nitrate solution while stirring. The lignin-based precursor is obtained by rotary evaporation and vacuum drying. The precursor is carbonized at 900°C for 2 h in an argon atmosphere in a tube furnace. The product is filtered and dried to obtain lignin-derived carbon.

[0069] Step 3: Take 5 mg of the catalyst and place it in a 5 ml centrifuge tube, add 1 ml of isopropanol and 20 μL of naphthol, and sonicate for 90 min until the dispersion is uniformly dissolved to prepare a carbon slurry;

[0070] In the oxygen reduction reaction, the slurry was evenly dropped onto the surface of the rotating disk electrode using a pipette, 5 μL each time, for a total of 4 drops, and then allowed to air dry to obtain a catalyst-loaded electrode.

[0071] In the oxygen evolution reaction, the carbon paper was cut into 1 cm × 1 cm size, and the slurry was evenly applied on both sides of the carbon paper using a pipette, 10 μL each time, 5 drops on each side, and then waited for natural air drying to obtain the catalyst-loaded electrode.

[0072] The lignin carbon material catalysts prepared by the above schemes are named Ni-SNC and Fe-SNC respectively.

[0073] Example 2

[0074] Step 1: Measure 100 mL of ultrapure water, add nickel nitrate hexahydrate and ferric nitrate nonahydrate with a metal ion concentration of 0.001 mol, and stir while adding to prepare a mixed solution;

[0075] Step 2: Weigh 1 g of kraft lignin powder, 5 g of urea, and 5 g of NaCl respectively and add them to the above mixed solution while stirring. The lignin-based precursor is obtained by rotary evaporation and vacuum drying. The precursor is carbonized at 900°C for 2 h in an argon atmosphere in a tube furnace. The product is filtered and dried to obtain lignin-derived carbon.

[0076] Step 3: Take 5 mg of the catalyst and place it in a 5 ml centrifuge tube, add 1 ml of isopropanol and 20 μL of naphthol, and sonicate for 90 min until the dispersion is uniformly dissolved to prepare a carbon slurry;

[0077] In the oxygen reduction reaction, the slurry was evenly dropped onto the surface of the rotating disk electrode using a pipette, 5 μL each time, for a total of 4 drops, and then allowed to air dry to obtain a catalyst-loaded electrode.

[0078] In the oxygen evolution reaction, the carbon paper was cut into 1 cm × 1 cm size, and the slurry was evenly applied on both sides of the carbon paper using a pipette, 10 μL each time, 5 drops on each side, and then waited for natural air drying to obtain the catalyst-loaded electrode.

[0079] Furthermore, the molar ratios of nickel nitrate hexahydrate and iron nitrate nonahydrate are 1:9, 3:7, and 5:5, respectively.

[0080] The lignin carbon material catalysts prepared by the above scheme are named Ni 0.9 Fe 0.1 -SNC、Ni 0.7 Fe 0.3 -SNC、Ni 0.5 Fe 0.5 -SNC.

[0081] The phase composition and electrochemical performance of the lignin-based nanocarbons prepared in Example 1 and Example 2 were tested and compared.

[0082] Phase analysis

[0083] The surface crystal structure of the samples of Example 1 and Example 2 was detected by X-ray diffractometer. According to the X-ray diffraction spectrum analysis and comparison with the PDF standard card, the main phase of Ni-SNC is Ni3S2, the main phase of Fe-SNC is Fe3C, and Ni 0.9 Fe 0.1 -SNC、Ni 0.7 Fe 0.3 -SNC、Ni 0.5 Fe 0.5 The main phase of SNC is NiFe alloy, which indicates that the metal elements in Examples 1 and 2 were successfully loaded, and nickel-iron alloy was successfully synthesized in the three bimetallic carbon materials in Example 2.

[0084] Analysis of sweep voltammetry and linear voltammetry curves of oxygen reduction reaction

[0085] The oxygen reduction electrocatalytic performance of Example 1 and Example 2 was tested using a standard three-electrode system and an electrochemical workstation. As the speed increases, the maximum diffusion current of oxygen reduction gradually increases. At the same time, by comparing the LSV curves of Example 1 and Example 2, it can be found that Ni 0.7 Fe 0.3 -SNC and Fe-SNC showed better ORR kinetic activity than other catalysts. 0.7 Fe 0.3showed the best oxygen reduction catalytic performance.

[0086] Analysis of Faradaic efficiency of oxygen reduction reaction

[0087] Tafel slope analysis of oxygen reduction reaction was performed on Example 1 and Example 2. 0.7 Fe 0.3 -SNC and Fe-SNC exhibit lower Tafel slopes, further indicating that Ni 0.7 Fe 0.3 -SNC and Fe-SNC exhibited better ORR kinetic activity than other catalysts.

[0088] Analysis of oxygen evolution linear voltammetric curve

[0089] The oxygen evolution electrocatalytic performance of Example 1 and Example 2 was tested using a standard three-electrode system and an electrochemical workstation. -2 , Ni 0.7 Fe 0.3 -SNC exhibited the lowest overpotential, indicating that the Ni-Fe bimetallic supported catalyst significantly improved OER catalytic performance compared to Fe and Ni monometallic catalysts. Comparison of catalysts with different metal ratios revealed that the catalyst prepared with a Ni-Fe ratio of 7:3 exhibited the best oxygen evolution performance among the three different ratios.

[0090] Tafel slope analysis of oxygen evolution reaction

[0091] The oxygen reduction reaction Tafel slope analysis was performed on Example 1 and Example 2. Nickel-iron alloy has better oxygen evolution kinetics than Fe and Ni single metal supported catalysts. And in the bimetallic supported catalysts with different ratios, Ni 0.7 Fe 0.3 -SNC has a much smaller Tafel slope than the other four catalysts, further indicating that Ni 0.7 Fe 0.3 -SNC exhibited the best OER activity.

[0092] Observe the Ni in Example 2 0.7 Fe 0.3 -SNC mapping elemental map shows the distribution of Ni, Fe, N, and S on the surface of the carbonized lignin-based carbon material, indicating the successful incorporation of these four elements into the biochar material. The uniform distribution of Ni and Fe indicates that there was no significant agglomeration of the metal phase during the preparation process, and they are highly dispersed on the surface of the material. This effectively promotes electron transfer, increases the active sites of the nanocarbon, and enhances the material's oxygen electrocatalytic performance.

[0093] The Ni0.7 Fe 0.3 -SNC was used to detect the number of transferred electrons and H2O2 yield. 0.7 Fe 0.3 -SNC maintains an extremely low conversion rate of hydrogen peroxide throughout the entire potential range and has high selectivity. At the same time, according to calculations, the average number of transferred electrons during the reaction is 3.95, proving that an efficient four-electron reaction pathway occurs throughout the entire potential range.

[0094] The Ni in Example 2 was tested using a three-electrode system and an electrochemical workstation. 0.7 Fe 0.3 -SNC was tested for oxygen reduction reaction and oxygen evolution reaction stability. Compared with commercial Pt / C catalyst, Ni 0.7 Fe 0.3 -SNC showed excellent oxygen reduction reaction stability and could maintain a high current density after 20,000s of continuous operation. Compared with Ni before and after 1,000 cycles, 0.7 Fe 0.3 -Linear scanning curve of SNC, when the current density reaches 10mAcm -2 When the electrode potential shows only a slight increase of less than 50mV. 0.7 Fe 0.3 -SNC catalyst has certain stability in OER reaction.

[0095] In order to verify the Ni 0.7 Fe 0.3 To test whether the catalytic performance of SNC can be used in practical applications, it was assembled into a zinc-air battery. -1 KOH solution and 0.2 mol L -1 Zinc acetate was prepared into electrolyte, and Ni 0.7 Fe 0.3 -SNC loaded carbon paper as air cathode (carbon paper area 2cm 2 , catalyst loading 1 mg cm -2 ), the zinc sheet was polished smooth to serve as the metal anode. A light-emitting diode (LED) was connected in series with the two assembled zinc-air batteries, and the LED was successfully lit, indicating that the assembled battery can provide power to the LED. To further verify the working performance of the assembled MABs, the polarization curve and open circuit voltage during operation were tested, and the power density curve was calculated. 0.7 Fe 0.3- The maximum power density of the SNC zinc-air battery is 97.16 mW cm -2, and has a high open circuit voltage of 1.386V. Through the rate charge and discharge test, it can be seen that as the current density increases exponentially, the voltage can remain stable. When the current density decreases to 0, the discharge voltage can return to the initial state, indicating that the assembled Ni 0.7 Fe 0.3 -SNC zinc-air battery has good rate performance. 0.7 Fe 0.3 -SNC's Zn-Air battery was discharged at a current density of 2 mA cm -2 Under the test, its specific capacity is 828.1mA hg -1 , indicating that the battery has a large specific capacity. In order to further confirm the assembled Ni 0.7 Fe 0.3 - The SNC zinc-air battery was tested for its long-term performance and stability. After a brief activation, the battery was able to operate stably for over 200 hours, with a charge potential of approximately 2.0V and a discharge voltage of approximately 1.2V, demonstrating excellent charge and discharge efficiency and stability.

[0096] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be permuted and combined. Those skilled in the art can exhaust all possibilities based on the mathematical knowledge of permutations and combinations. Therefore, the present invention will no longer describe the technical solutions after permutations and combinations one by one, but it should be understood that the technical solutions after permutations and combinations have been disclosed by the present invention.

[0097] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a lignin-derived oxygen reduction / oxygen evolution dual-functional electrocatalyst material, characterized in that: The steps include: Step 1: Add deionized water, Fe(NO3)3·9H2O, and Ni(NO3)2·6H2O into a beaker and stir thoroughly to obtain a nitrate solution; Step 2: Weigh kraft lignin powder, sodium chloride and urea, add them to the nitrate solution, and stir thoroughly to dissolve the suspension; Step 3: Evaporating the suspension to dryness by rotary evaporation, and then vacuum drying to obtain a kraft lignin precursor; Step 4: The kraft lignin precursor is subjected to high-temperature carbonization in a tubular furnace, ground, filtered, and dried to obtain a lignin-based nanocarbon material.

2. The method for preparing a lignin-derived oxygen reduction / oxygen evolution dual-functional electrocatalyst material according to claim 1, characterized in that: The metal ion concentration in the nitrate solution is 0.01 mol L -1 .

3. The method for preparing a lignin-derived oxygen reduction / oxygen evolution dual-functional electrocatalyst material according to claim 1, characterized in that: The molar ratio of Fe(NO3)3·9H2O to Ni(NO3)2·6H2O in the nitrate aqueous solution is one of 1:9, 3:7, and 5:

5.

4. The method for preparing a lignin-derived oxygen reduction / oxygen evolution dual-functional electrocatalyst material according to claim 1, characterized in that: The rotary evaporation temperature was 65°C.

5. The method for preparing a lignin-derived oxygen reduction / oxygen evolution dual-functional electrocatalyst material according to claim 1, characterized in that: The vacuum drying temperature was 60°C and the time was 12 hours.

6. The method for preparing a lignin-derived oxygen reduction / oxygen evolution dual-functional electrocatalyst material according to claim 1, characterized in that: The high-temperature carbonization in the tube furnace was carried out under argon atmosphere with a heating rate of 5 °C min -1 The temperature is 900℃ and the time is 2h.

7. A method for preparing a lignin-derived oxygen reduction / oxygen evolution dual-functional electrocatalyst material-loaded electrode, characterized in that: The steps include: Step 1: Take 5 mg of the lignin-based nanocarbon material obtained by the preparation method according to any one of claims 1 to 6 and put it into a 5 ml centrifuge tube, add 1 ml of isopropanol and 20 μL of naphthol, and sonicate for 90 min until it is evenly dispersed and dissolved to prepare a carbon slurry; Step 2: During the oxygen reduction reaction, use a pipette to evenly drop the slurry onto the surface of the rotating disk electrode, 5 μL each time, for a total of 4 drops, and wait for it to dry naturally to obtain a catalyst-loaded electrode; In the oxygen evolution reaction, the carbon paper was cut into 1 cm × 1 cm size, and the slurry was evenly applied on both sides of the carbon paper using a pipette, 10 μL each time, 5 drops on the front and back, and then waited for natural air drying to obtain the catalyst-loaded electrode.

8. Application of a lignin-derived oxygen reduction / oxygen evolution dual-functional electrocatalyst material, characterized by: In a standard three-electrode system cathode oxygen reduction reaction, the standard three-electrode system oxygen reduction reaction reference electrode is an Ag / AgCl electrode, the working electrode is a disk electrode loaded with the electrocatalyst prepared by the method described in claim 7, and the counter electrode is a Pt mesh electrode; In the standard three-electrode system anodic oxygen reduction reaction, the standard three-electrode system oxygen evolution reaction reference electrode is an Ag / AgCl electrode, and the working electrode is a 1 cm2 electrocatalyst loaded with the preparation method described in claim 7. 2 Carbon paper, the counter electrode is a Pt mesh electrode.

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