Method for improving the electrocatalytic activity of biomass dandelion-derived carbon
By activating dandelion stalks with ammonium oxalate, a dandelion-derived carbon catalyst with high specific surface area and nanoporous structure was prepared, which solved the problems of high cost and environmental pollution of existing carbon-based electrode materials and achieved high electrocatalytic activity and environmental protection performance of biomass-derived carbon.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ANHUI SCI & TECH UNIV
- Filing Date
- 2024-06-19
- Publication Date
- 2026-07-31
AI Technical Summary
Existing carbon-based electrode materials are costly, require complex equipment, and cause serious environmental pollution. Carbon materials used in direct biomass pyrolysis have low catalytic activity, and commonly used activators are highly corrosive, making them unsuitable for large-scale applications.
Using ammonium oxalate as an activator, dandelion-derived carbon catalysts with high specific surface area and nanoporous structure were prepared by pre-carbonization, ammonium oxalate activation, pyrolysis and acid washing of dandelion stalks.
It achieves high electrocatalytic activity of low-cost, environmentally friendly biomass-derived carbon materials, exhibiting excellent oxygen reduction reaction performance comparable to commercial Pt/C catalysts.
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Figure CN118754120B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of derived carbon technology, specifically a method for improving the electrocatalytic activity of derived carbon from biomass dandelion. Background Technology
[0002] As a heterogeneous catalytic reaction, the catalyst for the oxygen reduction reaction (ORR) needs to have a large specific surface area and a suitable pore structure to facilitate the exposure of catalytic active sites and the transport of electrolyte containing dissolved reactant and product particles.
[0003] Carbon materials have attracted widespread attention due to their large specific surface area, tunable pore structure, good electrical conductivity, abundant precursor sources, and strong mechanical properties. Conventional carbon-based electrode materials exhibit excellent catalytic performance; however, these materials are mainly synthesized from non-renewable fossil resources under demanding conditions, such as arc discharge, laser ablation, and chemical vapor deposition. This process results in high costs, low yields, and complex equipment, and also poses serious energy and environmental problems.
[0004] Biomass is a natural, abundant, and renewable carbon resource, serving as an effective carbon source for synthesizing various carbon materials. Inexpensive carbon materials can be obtained through pyrolysis. However, carbon materials obtained through direct pyrolysis typically exhibit low specific surface area, with a significant loss of active sites, making it difficult to achieve high catalytic activity. Activators can be used to form nanoporous structures during biomass pyrolysis, increasing the specific surface area of biomass carbon. Currently, KOH, ZnCl2, Na2CO3, K2CO3, NaHCO3, and H3PO4 have been used as activators in biomass carbon synthesis. However, these activators are highly corrosive, easily corroding equipment and polluting the environment during carbon material preparation, making them unsuitable for large-scale application. Therefore, developing simple, inexpensive, and environmentally friendly novel activators is a crucial approach to solving this problem. Summary of the Invention
[0005] The purpose of this invention is to provide a method for improving the electrocatalytic activity of biomass dandelion-derived carbon, so as to solve the problems mentioned in the background art.
[0006] To achieve the above objectives, the present invention provides the following technical solution:
[0007] A method for improving the electrocatalytic activity of biomass dandelion-derived carbon, the raw material of which includes dandelion stalks, and the preparation process mainly includes the following steps:
[0008] (1) Pre-carbonization of dandelion stalks: Dandelion stalks were placed in a vacuum drying oven and kept at 80°C for 12 hours to dry them. Then, an appropriate amount of dried dandelion stalks were weighed and placed in a high-pressure reactor with distilled water. The reactor was placed in an electric heating drying oven at 190°C for 12 hours to react. The dandelion stalks became shorter and dark black. After that, they were filtered and washed, and then placed in a vacuum drying oven at 80°C to dry overnight. After that, they were taken out and crushed into yellow powder by a pulverizer.
[0009] (2) Ammonium oxalate activation: Weigh an appropriate amount of ammonium oxalate and put it into a beaker. Add distilled water to dissolve it completely. Then add the yellow powder obtained in step (1) to it. Stir it magnetically for 12 hours at room temperature. Then wash and filter it with distilled water. Place the resulting dark yellow substance in a vacuum drying oven and dry it overnight at 80°C.
[0010] (3) High-temperature pyrolysis: Place an appropriate amount of dark yellow powder obtained in step (2) into a tube furnace and purge it with nitrogen. Heat the furnace to 1100°C and maintain it at this temperature for 2 hours. Then, allow the tube furnace to cool down to room temperature naturally under nitrogen purging to obtain black powder.
[0011] (4) Acid washing to obtain catalyst: Take out the black powder obtained in step (3) and add it to 0.1M hydrochloric acid aqueous solution and stir for 24 hours to remove impurities in the catalyst. Then, filter and wash with distilled water until neutral, and put it in a vacuum drying oven at 80°C overnight to obtain ammonium oxalate activated dandelion-derived carbon-based catalyst.
[0012] As a further aspect of the present invention: in step (1), 2g of dried dandelion stalks are weighed and placed into a high-pressure reactor with a volume of 100ml, and 80ml of distilled water is added.
[0013] Compared with the prior art, the beneficial effects of the present invention are: the method for improving the electrocatalytic activity of biomass dandelion-derived carbon proposed in the present invention has the advantages of simple experimental procedure, low cost and environmentally friendly materials. Attached Figure Description
[0014] Figure 1 XRD of ammonium oxalate-activated dandelion-derived carbon obtained by pyrolysis at different temperatures.
[0015] Figure 2 Scanning electron microscope (SEM) image of dandelion-derived carbon activated with ammonium oxalate.
[0016] Figure 3 Transmission electron microscopy (TEM) image of dandelion-derived carbon activated with ammonium oxalate.
[0017] Figure 4 Nitrogen adsorption-desorption isotherms and pore size distribution curves of dandelion-derived carbon activated with ammonium oxalate.
[0018] Figure 5To analyze the nitrogen content in dandelion-derived carbon obtained by pyrolysis of ammonium oxalate at different temperatures and to determine the distribution ratio of different nitrogen forms.
[0019] Figure 6 CV curves of dandelion-derived carbon activated with ammonium oxalate in N2 or O2 saturated KOH solutions.
[0020] Figure 7 Comparison of LSVs of oxygen reduction reaction between ammonium oxalate-activated dandelion-derived carbon prepared at different pyrolysis temperatures and commercial Pt / C.
[0021] Figure 8 The LSV curves of dandelion-derived carbon activated by ammonium oxalate at 1100℃ at different rotation speeds are shown (the inset shows the number of electrons transferred at different potentials). Detailed Implementation
[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0023] Example 1
[0024] A method for improving the electrocatalytic activity of biomass dandelion-derived carbon, the raw material of which includes dandelion stalks, and the preparation process mainly includes the following steps:
[0025] Step 1: Place the dandelion stalks in a vacuum drying oven and keep them at 80℃ for 12 hours to dry them. Then weigh 2g of the dried dandelion stalks and put them into a 100ml high-pressure reactor, add 80ml of distilled water, and place them in a 190℃ electric heating drying oven to react for 12 hours. The dandelion stalks will become shorter and dark black. After that, filter and wash them, and then place them in a vacuum drying oven at 80℃ to dry overnight. After taking them out, use a pulverizer to pulverize them into yellow powder.
[0026] Step 2: Weigh an appropriate amount of ammonium oxalate and put it into a beaker. Add distilled water to dissolve it completely. Then add the yellow powder obtained in Step 1. Stir it magnetically at room temperature for 12 hours. Wash it with distilled water and filter it. Place the resulting dark yellow substance in a vacuum drying oven and dry it overnight at 80°C.
[0027] Step 3: Place an appropriate amount of dark yellow powder obtained in Step 2 into a tube furnace and purge it with nitrogen. Heat the furnace to 1000°C and maintain the temperature for 2 hours. Then allow the tube furnace to cool naturally to room temperature while purging with nitrogen to obtain black powder.
[0028] Step 4: Take out the black powder obtained in Step 3 and add it to 0.1M hydrochloric acid aqueous solution and stir for 24 hours to remove impurities in the catalyst. Then, wash it with distilled water until neutral and place it in a vacuum drying oven at 80°C overnight to obtain ammonium oxalate activated dandelion-derived carbon-based catalyst.
[0029] Example 2
[0030] A method for improving the electrocatalytic activity of biomass dandelion-derived carbon, the raw material of which includes dandelion stalks, and the preparation process mainly includes the following steps:
[0031] Step 1: Place the dandelion stalks in a vacuum drying oven and keep them at 80℃ for 12 hours to dry them. Then weigh 2g of the dried dandelion stalks and put them into a 100ml high-pressure reactor, add 80ml of distilled water, and place them in a 190℃ electric heating drying oven to react for 12 hours. The dandelion stalks will become shorter and dark black. After that, filter and wash them, and then place them in a vacuum drying oven at 80℃ to dry overnight. After taking them out, use a pulverizer to pulverize them into yellow powder.
[0032] Step 2: Weigh an appropriate amount of ammonium oxalate and put it into a beaker. Add distilled water to dissolve it completely. Then add the yellow powder obtained in Step 1. Stir it magnetically at room temperature for 12 hours. Wash it with distilled water and filter it. Place the resulting dark yellow substance in a vacuum drying oven and dry it overnight at 80°C.
[0033] Step 3: Place an appropriate amount of dark yellow powder obtained in Step 2 into a tube furnace and purge it with nitrogen. Heat the furnace to 1100°C and maintain the temperature for 2 hours. Then allow the tube furnace to cool naturally to room temperature while purging with nitrogen to obtain black powder.
[0034] Step 4: Take out the black powder obtained in Step 3 and add it to 0.1M hydrochloric acid aqueous solution and stir for 24 hours to remove impurities in the catalyst. Then, wash it with distilled water until neutral and place it in a vacuum drying oven at 80°C overnight to obtain ammonium oxalate activated dandelion-derived carbon-based catalyst.
[0035] Example 3
[0036] A method for improving the electrocatalytic activity of biomass dandelion-derived carbon, the raw material of which includes dandelion stalks, and the preparation process mainly includes the following steps:
[0037] Step 1: Place the dandelion stalks in a vacuum drying oven and keep them at 80℃ for 12 hours to dry them. Then weigh 2g of the dried dandelion stalks and put them into a 100ml high-pressure reactor, add 80ml of distilled water, and place them in a 190℃ electric heating drying oven to react for 12 hours. The dandelion stalks will become shorter and dark black. After that, filter and wash them, and then place them in a vacuum drying oven at 80℃ to dry overnight. After taking them out, use a pulverizer to pulverize them into yellow powder.
[0038] Step 2: Weigh an appropriate amount of ammonium oxalate and put it into a beaker. Add distilled water to dissolve it completely. Then add the yellow powder obtained in Step 1. Stir it magnetically at room temperature for 12 hours. Wash it with distilled water and filter it. Place the resulting dark yellow substance in a vacuum drying oven and dry it overnight at 80°C.
[0039] Step 3: Place an appropriate amount of dark yellow powder obtained in Step 2 into a tube furnace and purge it with nitrogen. Heat the furnace to 1200°C and maintain the temperature for 2 hours. Then allow the tube furnace to cool naturally to room temperature while purging with nitrogen to obtain black powder.
[0040] Step 4: Take out the black powder obtained in Step 3 and add it to 0.1M hydrochloric acid aqueous solution and stir for 24 hours to remove impurities in the catalyst. Then, wash it with distilled water until neutral and place it in a vacuum drying oven at 80°C overnight to obtain ammonium oxalate activated dandelion-derived carbon-based catalyst.
[0041] Figure 1 The XRD results are for ammonium oxalate-activated dandelion-derived carbon obtained by pyrolysis at different temperatures. The results show that regardless of whether the pyrolysis is carried out at 1000℃, 1100℃ or 1200℃, the obtained samples are all graphene (PDF#75-1621).
[0042] Figure 2 , Figure 3 These are SEM and TEM images of ammonium oxalate-activated dandelion-derived carbon obtained by pyrolysis at 1100℃. The results show that the sample has an irregular morphology formed by nanoparticles agglomerated together. The particle size is between 10 and 15 nm. The particles are bonded together to form nanorods and nanosheets, and form pores of different sizes, with relatively more macropores. These structural features are conducive to the exposure of active sites and the transport of electrolyte.
[0043] Figure 4 These are the nitrogen adsorption-desorption isotherms and pore size distribution curves of dandelion-derived carbon activated with ammonium oxalate. The results show that the carbon materials obtained by pyrolysis at different temperatures all have a large specific surface area and a typical mesoporous structure. Without ammonium oxalate activation, the carbon material pyrolyzed at 1100℃ has a very low specific surface area, only 90.65 m². 2 Under ammonium oxalate activation, the specific surface area of the carbon material obtained by pyrolysis is greatly increased, and this increase is related to the pyrolysis temperature. The specific surface area at 1000℃ is 215.35 m². 2 / g, with a specific surface area of 319.96m² at 1100℃. 2 / g, with a specific surface area of 135.02m² at 1200℃. 2 / g; the pore size distribution of the three is as follows Figure 4As shown, at 1100℃, the porosity of the carbon material activated with ammonium oxalate is significantly higher than that of the carbon material without ammonium oxalate activation and at pyrolysis temperatures of 1000℃ and 1200℃, reaching a maximum of 0.312 cm⁻¹. 3 / g. These results indicate that the activation effect of ammonium oxalate effectively improves the pore structure of dandelion-derived carbon materials, generating a large number of mesopores. This has a very important promoting effect on the mass transfer process in the catalytic process and effectively improves the electrocatalytic activity of the carbon materials.
[0044] Figure 5 This study analyzes the nitrogen content and distribution ratios of different nitrogen forms in ammonium oxalate-activated dandelion-derived carbon obtained from pyrolysis at different temperatures. Nitrogen doping in carbon materials significantly affects their oxygen reduction reaction (ORR) catalytic activity. Nitrogen in nitrogen-doped carbon materials can decompose into pyridine nitrogen, pyrrole nitrogen, graphitic nitrogen, and nitrogen oxides depending on their bonding state. Research shows that pyridine nitrogen can effectively increase the onset reduction potential of the ORR and promote the conversion of the 2-electron reaction pathway to the 4-electron reaction pathway. Graphitic nitrogen can significantly increase the limiting diffusion current. Figure 5 As shown, at 1100℃, the total content of pyridine nitrogen and graphitic nitrogen in the carbon material activated by ammonium oxalate was the highest, reaching 67.5%. This will greatly improve the electrocatalytic performance of the carbon catalyst.
[0045] A working electrode was prepared using carbon material obtained from ammonium oxalate activation and pyrolysis at 1100℃. Using an Ag / AgCl electrode as the reference electrode and a platinum wire electrode as the counter electrode, and 0.1 MkOH as the electrolyte, cyclic voltammetry was applied to test the electrocatalytic oxidation of the oxygen reduction reaction under oxygen or nitrogen atmosphere. The results are as follows: Figure 6 As shown in the figure, the ammonium oxalate-activated dandelion-derived carbon produces a distinct oxygen reduction peak at 0.86 V (vs. RHE), with a peak current reaching 3.03 mA / cm². 2 It exhibits extremely excellent electrocatalytic performance in the oxygen reduction reaction.
[0046] Figure 7 In the context of Figure 6Linear voltammetric scan curves of different materials obtained by linear voltammetric scanning under the same conditions are shown in the figure. As can be seen from the figure, the initial reduction potentials of the dandelion carbon material without the activator ammonium oxalate, the carbon material with a pyrolysis temperature of 1000℃, 1100℃, 1200℃, and commercial Pt / C are 0.92V, 0.96V, 0.98V, 0.96V, and 0.98V, respectively. The dandelion-derived carbon obtained by ammonium oxalate activation all exhibited higher initial reduction potentials than the unactivated derivative carbon. The carbon material with a pyrolysis temperature of 1100℃ had the same initial reduction potential as commercial Pt / C, and its limiting diffusion current was much higher than the other carbon materials, while almost the same as commercial Pt / C, demonstrating its excellent electrocatalytic performance in the oxygen reduction reaction.
[0047] Figure 8 In the context of Figure 7 Linear voltammetric scan curves of carbon material with a pyrolysis temperature of 1100℃ at different electrode rotation speeds were obtained using linear voltammetry under the same conditions. The figures show that the initial reduction potential of the sample remains constant at different rotation speeds, but the limiting diffusion current increases with increasing rotation speed. The number of electrons transferred during the reduction reaction of oxygen molecules on the carbon catalyst surface is consistently 4, indicating that oxygen is fully reduced to OH- on its surface. - These results indicate that ammonium oxalate exhibits extremely excellent activation properties at 1100℃.
[0048] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.
[0049] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. A method for improving the electrocatalytic activity of biomass dandelion-derived carbon, characterized in that: The raw material includes dandelion stalks, and the preparation process mainly includes the following steps: (1) Pre-carbonization of dandelion stalks: Place dandelion stalks in a vacuum drying oven and keep them at 80°C for 12 hours to dry them. Then weigh an appropriate amount of dried dandelion stalks and put them into a high-pressure reactor and add distilled water. Place them in an electric heating drying oven at 190°C and react for 12 hours. The dandelion stalks will become shorter and dark black. After that, filter and wash them, and then place them in a vacuum drying oven at 80°C to dry overnight. After taking them out, use a pulverizer to pulverize them into yellow powder. (2) Ammonium oxalate activation: Weigh an appropriate amount of ammonium oxalate and put it into a beaker. Add distilled water to dissolve it completely. Then add the yellow powder obtained in step (1) to it. Stir it magnetically for 12 hours at room temperature. Then wash and filter it with distilled water. Place the resulting dark yellow substance in a vacuum drying oven and dry it overnight at 80°C. (3) High-temperature pyrolysis: Place an appropriate amount of dark yellow powder obtained in step (2) into a tube furnace and purge it with nitrogen. Heat the furnace to 1100°C and maintain it at this temperature for 2 hours. Then, allow the tube furnace to cool down to room temperature naturally under nitrogen purging to obtain black powder. (4) Acid washing to obtain catalyst: Take out the black powder obtained in step (3) and add it to 0.1M hydrochloric acid aqueous solution and stir for 24 hours to remove impurities in the catalyst. Then, filter and wash with distilled water until neutral, and put it in a vacuum drying oven at 80°C overnight to obtain ammonium oxalate activated dandelion-derived carbon-based catalyst.
2. The method for improving the electrocatalytic activity of biomass dandelion-derived carbon according to claim 1, characterized in that: In step (1), 2g of dried dandelion stalks are weighed and placed into a high-pressure reactor with a volume of 100ml, and 80ml of distilled water is added.