Lignite-derived porous carbon supported iron-cobalt-nickel electrocatalyst and preparation method and application thereof
Patent Information
- Application Number
- CN202611332989.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-31
- Publication Date
- 2026-11-03
AI Technical Summary
When lignite-based porous carbon materials are used as electrocatalysts for the oxygen evolution reaction (OER), their intrinsic electrocatalytic activity is low, their overpotential is high, and their reaction kinetics are slow, making it difficult to meet the needs of practical applications. Furthermore, existing metal-supported methods suffer from problems such as easy aggregation of metal nanoparticles, uneven particle size distribution, and difficulty in precisely controlling the loading amount, which restricts the improvement of catalytic activity.
Transition metals Fe, Co, and Ni were loaded onto a porous carbon support using a solvothermal method. Combined with the high conductivity and large specific surface area of lignite, the active components were highly dispersed and stably anchored, and a Fe-Co-Ni multi-metal synergistic system was constructed to optimize the adsorption/desorption energy barrier of OER intermediates.
The electrocatalytic activity of lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalysts was significantly improved, the overpotential was reduced, and the reaction kinetics were accelerated, thus realizing the efficient and clean utilization of lignite.
Smart Images
Figure CN123027616A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of coal-based porous carbon materials technology, specifically relating to lignite-derived porous carbon supported iron-cobalt-nickel electrocatalysts, and also to the preparation method and application of lignite-derived porous carbon supported iron-cobalt-nickel electrocatalysts. Background Technology
[0002] Lignite, a low-rank coal, is abundant and inexpensive in my country. However, its low calorific value, high ash content, and susceptibility to weathering and spontaneous combustion limit the feasibility of traditional combustion utilization. Therefore, exploring clean and high-value-added utilization pathways for lignite is of great significance. Lignite naturally possesses a high carbon content and abundant oxygen-containing functional groups, making it an ideal precursor for preparing functional carbon materials. Through processes such as KOH activation and catalytic pyrolysis, lignite can be transformed into porous carbon materials with high specific surface area and well-developed pore structure.
[0003] Although lignite-based porous carbon materials possess natural pore structures and abundant surface functional groups, their intrinsic electrocatalytic activity is low when directly used as electrocatalysts for the oxygen evolution reaction (OER), mainly manifested by high overpotential and sluggish reaction kinetics, making it difficult to meet practical application requirements. Therefore, modification of the carbon matrix is necessary to improve its OER performance. Common modification strategies include elemental doping, defect engineering, co-catalyst loading, and surface treatment. Among these strategies, loading transition metals is considered one of the most effective means to enhance the OER catalytic activity of carbon-based materials. Transition metals such as iron (Fe), cobalt (Co), and nickel (Ni) are widely used to construct metal / carbon composite catalysts due to their excellent redox reversibility, abundant d-orbital electrons, and suitable hydroxyl adsorption energy. However, existing metal loading methods mostly employ impregnation-thermal reduction processes, which suffer from problems such as easy aggregation of metal nanoparticles, uneven particle size distribution, and difficulty in precisely controlling the loading amount, leading to insufficient exposure of active sites. Furthermore, the weak interfacial electronic coupling effect between carbon supports and metal particles restricts further improvement of catalytic activity, and there is an urgent need to develop more efficient loading strategies to achieve synergistic enhancement between carbon supports and multiple metals.
[0004] Based on this, the present invention loads transition metals onto porous carbon supports via solvothermal methods. On the one hand, the high conductivity and large specific surface area of carbon materials can be used to achieve high dispersion and stable anchoring of active components. On the other hand, by constructing a multi-metal synergistic system such as Fe-Co-Ni, the electronic structure of active sites can be regulated, and the adsorption / desorption energy barrier for OER intermediates can be optimized, thereby significantly improving electrocatalytic activity. Summary of the Invention
[0005] The purpose of this invention is to provide a lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst, which solves the problems of low resource utilization of lignite and limited activity of lignite-based porous carbon material electrocatalysts.
[0006] The second objective of this invention is to provide a method for preparing a lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst.
[0007] A third objective of this invention is to provide the application of lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalysts.
[0008] The technical solution adopted in this invention is a method for preparing a lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst, comprising the following steps: Step 1: Mix lignite powder and KOH evenly in a solvent, then dry and grind to obtain precursor powder; Step 2: The precursor powder is subjected to a Joule heating reaction in an inert gas atmosphere to obtain the carbonized product; Step 3: The carbonization products are acid-washed, water-washed and dried to obtain lignite-derived porous carbon materials; Step 4: Mix lignite-derived porous carbon material with Fe, Co, and Ni sources in a solvent and undergo a solvothermal reaction to obtain a lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst.
[0009] The invention is further characterized by: In step 1, the lignite powder is the powder product obtained by high-energy ball milling of raw lignite for 3-6 hours; the solvent is deionized water; and the mass ratio of lignite powder to KOH is 1:1.
[0010] Step 1 is as follows: The ball-milled lignite powder and KOH are dispersed in deionized water, ultrasonically dispersed for 10-60 min, and then magnetically stirred at room temperature for 6-12 h. Subsequently, it is placed in a vacuum oven and dried at 70-90℃. Finally, the dried product is ground into powder to obtain the precursor powder.
[0011] In step 2, the inert gas is argon; the Joule heating reaction is carried out in a Joule heating device, the precursor powder is transferred to a graphite boat and placed in the Joule heating device; the temperature of the Joule heating reaction is 850~950℃, the reaction time is 1~6min, and the reaction is naturally cooled to room temperature after the reaction is completed.
[0012] Step 3 is as follows: the carbonization product is added to 0.5~2 mol / L dilute hydrochloric acid and stirred at room temperature for 1.5~3 h to remove residual KOH in the product; then centrifugation is performed at a speed of 8000~10000 rpm for 3~6 min; after centrifugation, the product is washed repeatedly with deionized water 3~10 times; finally, it is vacuum dried at 65~75℃ for 6~12 h to obtain lignite-derived porous carbon material.
[0013] In step 4, the solvent is ethylene glycol, and the pH is adjusted to 9-11 with KOH; the Fe source is ferric nitrate nonahydrate, the Co source is cobalt nitrate hexahydrate, and the Ni source is nickel nitrate hexahydrate; the temperature of the solvothermal reaction is 140-180℃, and the reaction time is 5-8h.
[0014] In step 4, the mass ratio of lignite-derived porous carbon, ferric nitrate nonahydrate, nickel nitrate hexahydrate, and cobalt nitrate hexahydrate is 1:0.3~0.5:0.2~0.4:0.2~0.4.
[0015] Step 4 specifically involves ultrasonically dispersing lignite-derived porous carbon, ferric nitrate nonahydrate, nickel nitrate hexahydrate, and cobalt nitrate hexahydrate in 15-30 ml of ethylene glycol solution, adjusting the pH to 9-11 with KOH, magnetically stirring for 20-40 min, transferring the mixture to a reaction vessel, and reacting at 140-180℃ for 5-8 h. After the reaction is complete, the product is removed, repeatedly washed with cyclohexane, ethanol, and deionized water, and finally dried in a vacuum oven to obtain the lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst.
[0016] The second technical solution adopted in this invention is a lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst, prepared using the above-mentioned preparation method for lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst, with the electrocatalyst operating at 10 mA / cm². 2 The overpotential at the given current density is 243 mV, and the Tafel slope is 62.8 mV / dec.
[0017] The third technical solution adopted in this invention is the application of lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst in the electrocatalytic oxygen evolution reaction.
[0018] The beneficial effects of this invention are: This invention relates to a lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst, its preparation method, and its application. It combines the advantages of lignite's rich pore structure, KOH-mediated pore structure control of carbon products, and transition metal element loading to form a simple and rapid method for synthesizing porous carbon materials supported on transition metals. KOH activation effectively etches the carbon framework, constructing numerous micropores and mesopores. A rapid carbothermal shock synthesis method shortens the synthesis time to the minute level, while ultra-fast heating and cooling effectively prevents over-etching of the activator. Furthermore, a solvothermal method is used to load the transition metal FeCoNi, regulating the electronic structure of active sites and optimizing the catalytic activity of the material, providing a reliable method for the efficient and clean utilization of lignite. Attached Figure Description
[0019] Figure 1 This is a SEM image of the porous carbon support sample prepared by heating at 900℃ for 1 min in an embodiment of the present invention. Figure 2This is a SEM image of a porous carbon support sample prepared by heating at 900°C for 2 min in an embodiment of the present invention; Figure 3 This is a SEM image of a porous carbon support sample prepared by heating at 900°C for 6 min in an embodiment of the present invention; Figure 4 These are the XRD patterns of porous carbon supports prepared using the same method but with different heating times in the embodiments of the present invention; Figure 5 These are Raman spectra of porous carbon supports prepared using the same method but with different heating times in the embodiments of the present invention; Figure 6 This is a specific surface area diagram of porous carbon supports prepared by the same method but with different heating times in the embodiments of the present invention; Figure 7 This is a pore size distribution diagram of porous carbon supports prepared by the same method but with different heating times in the embodiments of the present invention; Figure 8 This is a SEM image of FeCoNi supported on porous carbon based on lignite in an embodiment of the present invention; Figure 9 This is the EDS spectrum of C element in the lignite-based porous carbon-supported FeCoNi in the embodiments of the present invention; Figure 10 This is the EDS spectrum of Co element in the lignite-based porous carbon-supported FeCoNi in the embodiments of the present invention; Figure 11 This is the EDS spectrum of Fe element in the lignite-based porous carbon-supported FeCoNi in the embodiments of the present invention; Figure 12 This is the EDS spectrum of Ni element in the lignite-based porous carbon-supported FeCoNi in the embodiments of the present invention; Figure 13 This is the EDS spectrum of O element in the lignite-based porous carbon-supported FeCoNi in the embodiments of the present invention; Figure 14 This is an elemental composition spectrum of FeCoNi supported on lignite-based porous carbon in an embodiment of the present invention; Figure 15 This is the C 1s high-resolution XPS spectrum of FeCoNi supported on lignite-based porous carbon in an embodiment of the present invention; Figure 16 This is the high-resolution XPS spectrum of Fe 2p of FeCoNi supported on porous carbon in lignite-based materials in this embodiment of the invention; Figure 17 This is a high-resolution XPS image of Co 2p of FeCoNi supported on porous carbon in lignite-based materials in an embodiment of the present invention; Figure 18 This is the Ni 2p high-resolution XPS spectrum of FeCoNi supported on lignite-based porous carbon in an embodiment of the present invention; Figure 19 This is the overpotential for preparing lignite-derived porous carbon-supported FeCoNi in an embodiment of the present invention; Figure 20 This is a Tafel slope diagram of the preparation of lignite-derived porous carbon-supported FeCoNi in an embodiment of the present invention. Detailed Implementation
[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.
[0021] The preparation method of the lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst provided by the present invention includes the following steps: Step 1: Mix lignite powder and KOH evenly in a solvent, then dry and grind to obtain precursor powder; In step 1, the lignite powder is the powder product obtained by high-energy ball milling of raw lignite for 3-6 hours; the solvent is deionized water; the mass ratio of lignite powder to KOH is 1:1. Step 1 is as follows: the ball-milled lignite powder and KOH are dispersed in deionized water, ultrasonically dispersed for 10-60 min, magnetically stirred at room temperature for 6-12 h, and then dried in a vacuum oven at 70-90℃. Finally, the dried product is ground into powder to obtain precursor powder. Step 2: The precursor powder is subjected to a Joule heating reaction in an inert gas atmosphere to obtain the carbonized product; In step 2, the inert gas is argon; the Joule heating reaction is carried out in a Joule heating device, the precursor powder is transferred to a graphite boat and placed in the Joule heating device; the temperature of the Joule heating reaction is 850~950℃, the reaction time is 1~6min, and the reaction is naturally cooled to room temperature after the reaction is completed. Step 3: The carbonization products are acid-washed, water-washed and dried to obtain lignite-derived porous carbon materials; Step 3 specifically involves: adding the carbonization product to 0.5-2 mol / L dilute hydrochloric acid and stirring at room temperature for 1.5-3 hours to remove residual KOH from the product; then centrifuging at 8000-10000 rpm for 3-6 minutes; washing repeatedly with deionized water 3-10 times after centrifugation; and finally vacuum drying at 65-75℃ for 6-12 hours to obtain lignite-derived porous carbon material. Step 4: Mix lignite-derived porous carbon material with Fe, Co, and Ni sources in a solvent and undergo a solvothermal reaction to obtain a lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst. In step 4, the solvent is ethylene glycol, and the pH is adjusted to 9-11 with KOH; the Fe source is ferric nitrate nonahydrate, the Co source is cobalt nitrate hexahydrate, and the Ni source is nickel nitrate hexahydrate; the temperature of the solvothermal reaction is 140-180℃, and the reaction time is 5-8h. In step 4, the mass ratio of lignite-derived porous carbon, ferric nitrate nonahydrate, nickel nitrate hexahydrate, and cobalt nitrate hexahydrate is 1:0.3~0.5:0.2~0.4:0.2~0.4; Step 4 specifically involves ultrasonically dispersing lignite-derived porous carbon, ferric nitrate nonahydrate, nickel nitrate hexahydrate, and cobalt nitrate hexahydrate in 15-30 ml of ethylene glycol solution, adjusting the pH to 9-11 with KOH, magnetically stirring for 20-40 min, transferring the mixture to a reaction vessel, and reacting at 140-180℃ for 5-8 h. After the reaction is complete, the product is removed, repeatedly washed with cyclohexane, ethanol, and deionized water, and finally dried in a vacuum oven to obtain the lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst.
[0022] The lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst provided by this invention is prepared using the above-mentioned method for preparing lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalysts. The electrocatalyst operates at 10 mA / cm². 2 The overpotential at the given current density is 243 mV, and the Tafel slope is 62.8 mV / dec.
[0023] The application of the lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst provided by this invention in the electrocatalytic oxygen evolution reaction.
[0024] Example 1 The preparation method of the lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst proposed in this embodiment includes the following steps: 4 g of ball-milled lignite powder and 4 g of potassium hydroxide were dispersed in 30 ml of deionized water, ultrasonically dispersed for 30 min, and then magnetically stirred at room temperature for 8 h. The homogeneous solution was then vacuum dried and ground to obtain precursor powder. The precursor powder was placed in a graphite boat and heated at 900°C for 1 minute in an argon atmosphere using a Joule heating device. After cooling to room temperature, the black powder was collected. The collected black powder was first washed with 1 mol / L dilute hydrochloric acid for 2 h, then repeatedly washed with deionized water, and finally dried at 70℃ for 12 h to obtain lignite-derived porous carbon support. SEM images of lignite-derived porous carbon under the reaction conditions are shown below. Figure 1 As shown, it exhibits a distinct porous structure, such as Figure 6 As shown, the specific surface area is 532.50 m². 2 / g, such as Figure 4As shown, XRD results indicate that the product is still dominated by disordered carbon, such as... Figure 5 As shown, the Raman spectrum indicates that the product has characteristic peaks attributable to carbon.
[0025] Example 2 The preparation method of the lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst proposed in this embodiment includes the following steps: 4 g of ball-milled lignite powder and 4 g of potassium hydroxide were dispersed in 30 ml of deionized water, ultrasonically dispersed for 30 min, and then magnetically stirred at room temperature for 8 h. The homogeneous solution was then vacuum dried and ground to obtain precursor powder. The precursor powder was placed in a graphite boat and heated at 900°C for 2 minutes in an argon atmosphere using a Joule heating device. After cooling to room temperature, the black powder was collected. The collected black powder was first washed with 1 mol / L dilute hydrochloric acid for 2 h, then repeatedly washed with deionized water, and finally dried at 70℃ for 12 h. SEM images of lignite-derived porous carbon under these reaction conditions, such as... Figure 2 As shown, it exhibits a distinct porous structure, such as Figure 6 As shown, the specific surface area is 805.37 m². 2 / g, XRD results show that the product is still dominated by disordered carbon, such as Figure 5 As shown, the Raman spectrum indicates that the product has characteristic peaks attributable to carbon.
[0026] Example 3 The preparation method of the lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst proposed in this embodiment includes the following steps: 4 g of ball-milled lignite powder and 4 g of potassium hydroxide were dispersed in 30 ml of deionized water, ultrasonically dispersed for 30 min, and then magnetically stirred at room temperature for 8 h. The homogeneous solution was then vacuum dried and ground to obtain precursor powder. The precursor powder was placed in a graphite boat and then heated at 900°C for 6 minutes in an argon atmosphere using a Joule heating device. After cooling to room temperature, the black powder was collected. The collected black powder was first washed with 1 mol / L dilute hydrochloric acid for 2 h, then repeatedly washed with deionized water, and finally dried at 70℃ for 12 h. SEM images of lignite-derived porous carbon under these reaction conditions, such as... Figure 3 As shown, it exhibits a distinct porous structure, which increases with Joule heating time, as... Figure 6 As shown, it has the largest specific surface area of 1014.52 m². 2 / g, pore size distribution as follows Figure 7As shown, the product exhibits a hierarchical porous structure of micropores, mesopores, and macropores. XRD results indicate that the product is still dominated by disordered carbon. Furthermore, as shown... Figure 5 As shown, Raman analysis results indicate that the product has characteristic peaks attributed to carbon. Its Ig... D / I G Characterizing the defects of the product revealed that the ID / IG ratio of the product gradually decreased with the extension of heating time, indicating that extending the heating time is beneficial to reducing the degree of defects in the product.
[0027] Example 4 The preparation method of the lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst proposed in this embodiment includes the following steps: 1 g of lignite-derived porous carbon prepared in Example 3, 0.4 g of ferric nitrate nonahydrate, 0.29 g of nickel nitrate hexahydrate, and 0.29 g of cobalt nitrate hexahydrate were ultrasonically dispersed in an ethylene glycol solution, and the pH was adjusted to 10 with KOH. After magnetic stirring for 30 min, the mixture was transferred to a reaction vessel and reacted at 160 °C for 6 h. Finally, the product was removed and repeatedly washed with cyclohexane, ethanol, and deionized water. The product was then dried in a vacuum oven to obtain the final product FeCoNi@LPC-1-1-360s.
[0028] The SEM and EDS spectra of the products under these reaction conditions are as follows: Figure 8 As shown, this indicates that the catalyst can still maintain a loose and porous morphology after solvothermal treatment. (EDS energy dispersive spectroscopy, such as...) Figures 9-13 As shown, Co, Fe, and Ni are uniformly distributed on the carbon support; XPS spectra, as shown... Figures 15-18 As shown, FeCoNi exists in the form of oxides. The high-resolution C spectrum shows that the oxides of Fe, Co, and Ni are anchored on a carbon-based support, as... Figure 14 As shown, the content of all three elements is between 3% and 4%. Electrochemical performance tests indicate that FeCoNi@LPC-1-1-360s exhibits the best performance at 10 mA / cm². 2 At the current density, its overpotential is 243mV, such as Figure 19 As shown, the Tafel slope is 62.8 mV / dec, as... Figure 20 As shown, this demonstrates that the catalyst possesses good catalytic activity and reaction kinetics; Furthermore, a comparison between LPC-1-1-360s (Example 3) and FeCoNi@LPC-1-1-360s (Example 4) revealed that the electrocatalytic performance was greatly improved after loading FeCoNi. In summary, by loading FeCoNi onto lignite-derived porous carbon for electrocatalytic OER reaction, high-value-added clean utilization of lignite was achieved.
[0029] Example 5 The preparation method of the lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst proposed in this embodiment includes the following steps: Step 1: Preparation of precursor powder; 4 g of ball-milled lignite powder and 4 g of potassium hydroxide were ultrasonically dispersed and dissolved in deionized water, and then stirred at room temperature for 8 h to obtain a precursor solution. The precursor solution was then placed in a vacuum oven at 80°C for drying. Finally, the dried product was ground into powder to obtain the final precursor powder. Step 2: Rapid carbothermal shock reaction synthesis; The precursor powder obtained in Step 1 is transferred to a graphite boat, which is then placed in a Joule heating device and heated at 900°C in an argon atmosphere for 1-6 minutes. After the reaction is completed, the mixture is allowed to cool naturally to room temperature. Step 3: Post-processing of the product; The obtained solid product was added to 1 mol / L dilute hydrochloric acid and stirred at room temperature for 2 h to remove KOH from the product. Then it was separated by centrifugation at a speed of 9000 rpm for 4 min. It was washed repeatedly with deionized water 5 times and finally vacuum dried at 70℃ for 6-12 h to obtain lignite-derived porous carbon material. Step 4: Preparation of FeCoNi supported on lignite-derived porous carbon; 1 g of lignite-derived porous carbon, 0.4 g of ferric nitrate nonahydrate, 0.29 g of nickel nitrate hexahydrate, and 0.29 g of cobalt nitrate hexahydrate were ultrasonically dispersed in 20 ml of ethylene glycol solution, and the pH was adjusted to 10 with KOH. After magnetic stirring for 30 min, the mixture was transferred to a reaction vessel and reacted at 160℃ for 6 h. Finally, the product was taken out and repeatedly washed with cyclohexane, ethanol, and deionized water. Finally, it was placed in a vacuum oven to dry and obtain the final product FeCoNi@LPC. Step 5: Material Characterization; The materials obtained in steps 3 and 4 were subjected to SEM, BET, XRD, Raman, and XPS characterization tests to analyze their pore structure, specific surface area, and composition. SEM and BET tests revealed that the materials possess a rich pore structure and a specific surface area reaching a maximum of 10¹⁴.52 m². 2 / g, combined with XRD and Raman test results, indicates that lignite-derived porous carbon with high specific surface area was successfully prepared; EDS and XPS show that Fe, Co, and Ni are uniformly distributed on the carbon support, further proving the successful preparation of lignite-derived porous carbon loaded with FeCoNi. Step 6: Electrochemical performance testing; The materials obtained in steps 3 and 4 are subjected to electrochemical performance testing; Take 100 mg of the ground catalyst and add it to a mixture of 1 ml ethanol, 1 ml deionized water, and 20 μl of Nafion solution. Disperse by sonication for 30 min. Take 20 μl of the dispersion each time, adding it dropwise 10 times to a 1 cm³ solution. 2On carbon cloth, used for oxygen evolution testing in water electrolysis; A three-electrode system was constructed using catalyst-supported carbon cloth as the working electrode, a platinum sheet as the counter electrode, and a mercuric oxide electrode as the reference electrode, with 1M KOH solution as the electrolyte. The OER performance of the catalyst was evaluated by linear sweep voltammetry. The electrochemical testing platform used was the Shanghai Chenhua 760E electrochemical workstation. Before testing, the three-electrode testing system was assembled, and the voltage testing range was set to (0.64-1.64 (vs. RHE)). A CV scan was performed at a scan rate of 100 mV / s for 40 cycles to activate the sample. Then, LSV testing was performed at 0.94-1.64 V.
[0030] Example 6 The preparation method of the lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst proposed in this embodiment includes the following steps: Step 1: Preparation of precursor powder: Raw lignite was placed in a high-energy ball mill and milled at 400 rpm for 4 hours to obtain ball-milled lignite powder. 4g of the ball-milled lignite powder and 4g of KOH (the mass ratio of lignite powder to KOH was 1:1) were weighed and dispersed in 30ml of deionized water. After ultrasonic dispersion for 30 minutes, the mixture was magnetically stirred at room temperature for 8 hours. Subsequently, it was dried in a vacuum oven at 80℃. Finally, the dried product was thoroughly ground into powder in an agate mortar to obtain the precursor powder. Step 2, Rapid carbothermal shock reaction synthesis: The precursor powder obtained in Step 1 was uniformly transferred into a graphite boat, which was then placed in a Joule heating device. The Joule thermal reaction was then carried out at 900°C in an argon atmosphere for 4 minutes. After the reaction was completed, the mixture was allowed to cool naturally to room temperature, and the black solid product was collected. Step 3, Product post-processing: The black solid product obtained in Step 2 was added to 1 mol / L dilute hydrochloric acid and stirred at room temperature for 2 h to remove residual KOH in the product; then centrifuged at 9000 rpm for 4 min; after centrifugation, it was washed repeatedly with deionized water 5 times; finally, it was vacuum dried at 70℃ for 12 h to obtain lignite-derived porous carbon material. Step 4: Preparation of FeCoNi supported on lignite-derived porous carbon: 1g of lignite-derived porous carbon obtained in Step 3, 0.4g of ferric nitrate nonahydrate, 0.29g of nickel nitrate hexahydrate, and 0.29g of cobalt nitrate hexahydrate (mass ratio of lignite-derived porous carbon, ferric nitrate nonahydrate, nickel nitrate hexahydrate, and cobalt nitrate hexahydrate is 1:0.4:0.29:0.29) were ultrasonically dispersed in 20ml of ethylene glycol solution, and the pH was adjusted to 10 with KOH. After magnetic stirring for 30min, the mixture was transferred to a reaction vessel and reacted at 160℃ for 6h. After the reaction, the product was removed and repeatedly washed with cyclohexane, ethanol, and deionized water. Finally, it was dried in a vacuum oven to obtain the lignite-derived porous carbon supported on FeCoNi electrocatalyst, denoted as FeCoNi@LPC-1-1-240s (where "1-1" represents the mass ratio of lignite to KOH as 1:1, and "240s" represents the Joule heating reaction time as 4min). Material characterization and performance testing: The lignite-derived porous carbon material obtained in step 3 was characterized by SEM, BET, XRD, and Raman spectroscopy. SEM images showed that the lignite-derived porous carbon, heated at 900℃ for 4 min, exhibited a distinct three-dimensional interconnected porous structure. As the Joule heating time increased from 1 min to 4 min, the etching of the carbon skeleton deepened, and the pore development became more complete. BET surface area measurements indicated that the specific surface area of the lignite-derived porous carbon under these conditions was 912.38 m² / g, falling between that of Example 2 (805.37 m² / g) and Example 3 (1014.52 m² / g). The pore structure was predominantly micropores and mesopores, with the proportion of mesopores gradually increasing with heating time. XRD patterns showed that the product was still dominated by disordered carbon, with broad diffuse diffraction peaks belonging to carbon appearing near 2θ = 24° and 43°. Raman spectroscopy showed that the product possessed characteristic D and G peaks belonging to carbon. The Ig value was calculated. D / I G A value of 1.08 indicates that the carbon material has a certain degree of graphitization structural defects; The FeCoNi@LPC-1-1-240s obtained in step 4 was characterized by SEM and EDS. SEM images showed that after solvothermal loading, the product maintained its loose and porous morphology, with nanoscale particles uniformly distributed on the surface of the lignite-derived porous carbon support. EDS analysis indicated that Fe, Co, and Ni were uniformly distributed on the carbon support surface, with no obvious elemental segregation observed. Their elemental contents were all between 1% and 3%, indicating that FeCoNi was successfully loaded onto the lignite-derived porous carbon support via a solvothermal method. XPS spectra further confirmed that FeCoNi existed on the carbon support surface in the form of oxides / hydroxides. The FeCoNi@LPC-1-1-240s obtained in step 4 was subjected to electrochemical performance testing. 100 mg of the ground catalyst was added to a mixture of 1 ml ethanol, 1 ml deionized water, and 20 μl Nafion solution, and ultrasonically dispersed for 30 min. 20 μl of the dispersion was taken dropwise 10 times and added to a 1 cm² sheet of carbon cloth, which was then allowed to air dry before being used as the working electrode. A three-electrode system was constructed using a platinum sheet as the counter electrode, a mercuric oxide electrode as the reference electrode, and 1 M KOH solution as the electrolyte. On a Shanghai Chenhua 760E electrochemical workstation, a CV scan was performed at a scan rate of 100 mV / s for 40 cycles to activate the sample, followed by LSV testing within the potential range of 0.94–1.64 V. Electrochemical tests showed that FeCoNi@LPC-1-1-240s exhibited a high overpotential of 258 mV and a Tafel slope of 65.2 mV / dec at a current density of 10 mA / cm², demonstrating excellent OER electrocatalytic activity. Compared with LPC-1-1-360s (unloaded metal) obtained in Example 3, the electrocatalytic performance was significantly improved after loading FeCoNi, which is attributed to the synergistic effect among the multi-metal components of FeCoNi and the strong interaction between the carbon support and the metal active sites.
[0031] This embodiment further verifies the effectiveness of lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst in the electrocatalytic oxygen evolution reaction (OER). By adjusting the Joule heating reaction time, the pore structure and specific surface area of the lignite-derived porous carbon support can be controlled, thereby affecting the dispersion and electrocatalytic performance of the supported metal active components. Compared with Examples 1-3, the carbon support obtained in this embodiment under a Joule heating reaction time of 4 min possesses both a higher specific surface area and a suitable pore structure. After solvothermal loading of FeCoNi, the active metal is uniformly distributed on the carbon support, fully leveraging the synergistic catalytic effect among the three metals. This embodiment achieves high-value-added clean utilization of lignite, providing a feasible technical solution for the conversion of low-rank coal into functional carbon materials.
Claims
1. A method for preparing a lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst, characterized in that, Includes the following steps: Step 1: Mix lignite powder and KOH evenly in a solvent, then dry and grind to obtain precursor powder; Step 2: The precursor powder is subjected to a Joule heating reaction in an inert gas atmosphere to obtain the carbonized product; Step 3: The carbonization products are acid-washed, water-washed and dried to obtain lignite-derived porous carbon materials; Step 4: Mix lignite-derived porous carbon material with Fe, Co, and Ni sources in a solvent and undergo a solvothermal reaction to obtain a lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst.
2. The preparation method of the lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst according to claim 1, characterized in that, In step 1, the lignite powder is the powder product obtained by high-energy ball milling of raw lignite for 3-6 hours; the solvent is deionized water; and the mass ratio of lignite powder to KOH is 1:
1.
3. The preparation method of the lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst according to claim 2, characterized in that, Step 1 specifically involves dispersing the ball-milled lignite powder and KOH in deionized water, ultrasonically dispersing for 10-60 minutes, magnetically stirring at room temperature for 6-12 hours, then drying in a vacuum oven at 70-90°C, and finally grinding the dried product into powder to obtain the precursor powder.
4. The preparation method of the lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst according to claim 1, characterized in that, In step 2, the inert gas is argon; the Joule heating reaction is carried out in a Joule heating device, the precursor powder is transferred to a graphite boat and placed in the Joule heating device; the temperature of the Joule heating reaction is 850~950℃, the reaction time is 1~6min, and the reaction is naturally cooled to room temperature after the reaction is completed.
5. The method for preparing the lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst according to claim 1, characterized in that, Step 3 specifically involves: adding the carbonization product to 0.5-2 mol / L dilute hydrochloric acid and stirring at room temperature for 1.5-3 hours to remove residual KOH from the product; then centrifuging at 8000-10000 rpm for 3-6 minutes; washing repeatedly with deionized water 3-10 times after centrifugation; and finally vacuum drying at 65-75°C for 6-12 hours to obtain lignite-derived porous carbon materials.
6. The method for preparing the lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst according to claim 1, characterized in that, In step 4, the solvent is ethylene glycol, and the pH is adjusted to 9-11 with KOH; the Fe source is ferric nitrate nonahydrate, the Co source is cobalt nitrate hexahydrate, and the Ni source is nickel nitrate hexahydrate; the temperature of the solvothermal reaction is 140-180℃, and the reaction time is 5-8h.
7. The method for preparing the lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst according to claim 6, characterized in that, In step 4, the mass ratio of lignite-derived porous carbon, ferric nitrate nonahydrate, nickel nitrate hexahydrate, and cobalt nitrate hexahydrate is 1:0.3~0.5:0.2~0.4:0.2~0.
4.
8. The method for preparing the lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst according to claim 7, characterized in that, Step 4 specifically involves ultrasonically dispersing lignite-derived porous carbon, ferric nitrate nonahydrate, nickel nitrate hexahydrate, and cobalt nitrate hexahydrate in 15-30 ml of ethylene glycol solution, adjusting the pH to 9-11 with KOH, magnetically stirring for 20-40 min, transferring the mixture to a reaction vessel, and reacting at 140-180℃ for 5-8 h. After the reaction is complete, the product is removed, repeatedly washed with cyclohexane, ethanol, and deionized water, and finally dried in a vacuum oven to obtain the lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst.
9. A lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst, characterized in that, The lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst was prepared using the method described in any one of claims 1-8, wherein the electrocatalyst operates at 10 mA / cm². 2 The overpotential at the given current density is 243 mV, and the Tafel slope is 62.8 mV / dec.
10. The application of the lignite-derived porous carbon-supported iron-cobalt-nickel electrocatalyst according to claim 9 in the electrocatalytic oxygen evolution reaction.