Preparation method of nitrogen-doped porous carbon catalytic electrode and application of nitrogen-doped porous carbon catalytic electrode in electrosynthesis of hydrogen peroxide
By preparing a nitrogen-doped porous carbon catalytic electrode, the problem of insufficient 2e-ORR performance of carbon-based materials was solved, and efficient and stable hydrogen peroxide production was achieved. The catalyst exhibited excellent electrochemical performance in an acidic environment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-06
- Publication Date
- 2026-03-10
AI Technical Summary
Existing carbon-based materials have insufficient performance in the electrochemical catalysis of the two-electron oxygen reduction reaction (2e-ORR), especially in terms of electrochemical activity, selectivity and stability, and there is room for improvement. Noble metal catalysts are difficult to commercialize on a large scale due to reserves and cost limitations.
Using melamine resin as a precursor, a nitrogen-doped porous carbon catalyst was prepared by chemical polymerization. After calcination, a nitrogen-doped porous carbon catalytic electrode was formed, constructing a nitrogen-doped carbon defect structure for efficient electrosynthesis of hydrogen peroxide.
The production of hydrogen peroxide with high selectivity and high stability was achieved. The catalyst maintained high activity for a long time under acidic conditions, with H2O2 selectivity reaching 97.9%, and 2wt% hydrogen peroxide solution was continuously produced in a flow reactor.
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Figure CN121629451A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electrocatalysis technology, specifically to a method for preparing a nitrogen-doped porous carbon catalytic electrode and its application in the electrosynthesis of hydrogen peroxide. Background Technology
[0002] Hydrogen peroxide (H2O2), one of the world's 100 most important chemicals, is widely used in energy, healthcare, chemical industries, and environmental remediation through its aqueous solution, hydrogen peroxide. However, traditional hydrogen peroxide production primarily relies on energy-intensive anthraquinone recycling processes, which require significant energy and land investment and generate substantial amounts of organic pollutants. Furthermore, the storage and transportation costs associated with these centralized production methods are also considerable. In recent years, electrochemical catalysis of the two-electron oxygen reduction reaction (2e⁻) has been developing… - ORR (Organic Recombinant Hydrogenation) has been widely studied as a green and efficient H2O2 synthesis technology.
[0003] Experiments and theoretical calculations show that noble metals and their alloys possess excellent 2e properties. - While ORR exhibits activity and selectivity, its large-scale commercial application is hampered by limitations in reserves and cost. Therefore, abundant, inexpensive, and structurally diverse and tunable carbon-based materials have garnered widespread attention from researchers. Currently, the 2e... - ORR performance modulation techniques include hierarchical porous carbon, defect construction, and heteroatom doping. Nevertheless, the performance of carbon-based materials still urgently needs improvement in terms of electrochemical activity, selectivity, and stability. To address the shortcomings of existing carbon-based materials' electrochemical performance, we propose a method for preparing a nitrogen-doped porous carbon catalytic electrode and its application in the electrosynthesis of hydrogen peroxide. Specifically, a nitrogen-doped porous carbon catalyst is obtained by calcination of melamine resin as a precursor, and then used as a catalytic electrode for the efficient electrosynthesis of hydrogen peroxide. Summary of the Invention
[0004] To address the aforementioned shortcomings of existing technologies, this invention provides a method for preparing a nitrogen-doped porous carbon catalytic electrode and its application in the electrosynthesis of hydrogen peroxide. This nitrogen-doped porous catalyst possesses a variety of rich nitrogen-doped carbon defect structures, thereby enabling the production of hydrogen peroxide with high selectivity and high stability through electrochemical technology.
[0005] The objective of this invention is achieved through the following technical solution:
[0006] In a first aspect, the present invention provides a method for preparing a nitrogen-doped porous carbon catalytic electrode, comprising the following steps:
[0007] S1. Melamine is mixed with formaldehyde solution, and a crosslinking agent is added for polymerization; the solvent is removed by washing with sodium hydroxide-ethanol solution to obtain melamine resin;
[0008] S2. Calcining the melamine resin in step S1 yields a nitrogen-doped porous carbon catalyst.
[0009] S3. Prepare a nitrogen-doped porous carbon catalytic electrode from the nitrogen-doped porous carbon catalyst in step S2.
[0010] Preferably, the concentration of the sodium hydroxide-ethanol solution is 0.1–3 mol / L. -1 .
[0011] In some embodiments, after washing with a sodium hydroxide-ethanol solution, the solvent is removed by heating / rotary evaporation; then, the resin is washed several times with water and ethanol, with each wash followed by heating / rotary evaporation to remove the solvent, until the pH is neutral. In this invention, alkaline washing of the melamine resin increases the oxygen content in the resin, thereby giving the nitrogen-doped porous carbon catalyst excellent electrocatalytic performance. In this invention, heating / rotary evaporation is used to remove the solvents water and ethanol; the purpose of alkaline washing is to allow -OH groups to combine with the resin, increasing the oxygen content in the resin and the calcined catalyst; and the subsequent repeated washing with water and ethanol is to achieve a neutral pH, with the surfactant mainly removed during the calcination process in step S2.
[0012] Preferably, the crosslinking agent includes a surfactant.
[0013] Preferably, the surfactant includes (but is not limited to) at least one of hexamethylenetetramine, poloxamer (Pluronic F127), cetyltrimethylammonium bromide (CTAB), and polyvinylpyrrolidone (PVP). The use of surfactants in this invention transforms the prepared melamine resin from a disordered chain structure into a porous nitrogen-doped carbon nanotube structure.
[0014] Preferably, the formaldehyde solution has a mass concentration of 10-60%.
[0015] Preferably, the mass ratio of melamine to formaldehyde solution is 1:4 to 4:1.
[0016] Preferably, the polymerization temperature is 60-90°C.
[0017] Preferably, the mass ratio of the surfactant to melamine is 1:10 to 1:1000.
[0018] In some embodiments, the method for removing the solvent includes at least one of heating evaporation and rotary evaporation.
[0019] Preferably, the calcination temperature in step S2 is 300-900℃.
[0020] Preferably, the preparation in step S3 includes: mixing the catalyst, binder, and solvent to prepare a uniformly dispersed catalyst slurry, which is then loaded onto a porous electrode substrate.
[0021] Preferably, the mixing method includes at least one of ultrasound and stirring.
[0022] Preferably, the loading method includes at least one of drip coating and spray coating.
[0023] Preferably, the mass ratio of the catalyst, binder, and solvent is 1:2.5:1000-30:20:1000.
[0024] In some embodiments, the porous electrode substrate includes (but is not limited to) at least one of carbon paper, carbon felt, and titanium felt that has undergone hydrophobic pretreatment.
[0025] Secondly, the present invention provides a nitrogen-doped porous carbon catalytic electrode prepared by the above-described preparation method.
[0026] Thirdly, the present invention provides an application of the above-mentioned nitrogen-doped porous carbon catalytic electrode in the electrosynthesis of hydrogen peroxide.
[0027] In some embodiments, the method of application includes characterizing the electrochemical hydrogen peroxide synthesis performance of the catalytic electrode in a rotating disk test, an H-type electrolyzer, and a flow gas diffusion electrolyzer, respectively.
[0028] Compared with the prior art, the present invention has the following beneficial effects:
[0029] 1. This invention uses chemical polymerization to prepare nitrogen-doped carbon-based catalyst precursors, obtaining a stable nitrogen-doped carbon-based polymer bulk phase structure, which lays the structural foundation for the high activity and high stability of the catalyst in a long-term electrochemical oxygen reduction environment.
[0030] 2. The nitrogen-doped carbon-based porous catalyst proposed in this invention has an active site structure and its proportion that are easy to control, thus providing a theoretical basis for the efficient and precise functionalization synthesis of subsequent high-efficiency nitrogen-doped carbon-based catalysts.
[0031] 3. Compared to most catalysts that only exhibit better 2e under alkaline conditions... - Regarding ORR performance, the nitrogen-doped carbon-based porous catalytic electrode proposed in this invention can also stably perform high-activity and high-selectivity 2e ... - ORR reaction. Attached Figure Description
[0032] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:
[0033] Figure 1 This is a high-resolution transmission electron microscope image of the nitrogen-doped porous carbon catalyst in Example 1;
[0034] Figure 2 The results of the H2O2 selectivity test in Example 1 are shown.
[0035] Figure 3 The results are from the long-term stability test in the flow reactor in Example 1;
[0036] Figure 4 The results of H2O2 selectivity testing using a rotating disk in Comparative Example 1;
[0037] Figure 5 The results of H2O2 selectivity testing using a rotating disk in Comparative Example 2 are shown.
[0038] Figure 6 The results of H2O2 selectivity testing using a rotating disk in Comparative Example 3;
[0039] Figure 7 This is a schematic diagram of the preparation method of the nitrogen-doped porous carbon catalyst of the present invention. Detailed Implementation
[0040] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.
[0041] Example 1
[0042] Figure 7 This is a schematic diagram of the preparation method of the nitrogen-doped porous carbon catalyst of the present invention, as shown below. Figure 7 As shown, a melamine and formaldehyde solution (37 wt%) with a mass ratio of 2:3 and surfactant F127 (mass ratio of F127 to melamine 1:32) were added to a 100 mL round-bottom flask. The mixture was refluxed and stirred at 80 °C for 1 h to obtain a melamine resin solution. After cooling to room temperature, it was dissolved in 100 mL of 1 M NaOH ethanol solution. The solvent water and ethanol were removed by rotary evaporation. The mixture was then washed with water and ethanol sequentially, repeated three times. After each washing, the solvent was removed by rotary evaporation until the pH was neutral, which was the melamine resin. A tube furnace was used to heat the resin at 1 °C for 1 min. -1 The temperature was increased to 600℃ at a certain rate and held for 3 hours to obtain the nitrogen-doped porous carbon catalyst.
[0043] A catalyst slurry was prepared by ultrasonication and stirring of catalyst, binder, and solvent in a mass ratio of 1:2.5:1000. The slurry was then ultrasonically sprayed at a concentration of 0.25 mg / L. 催化剂 cm -2 The loading amount (referring to 0.25 mg of catalyst in the slurry loaded on each square centimeter of electrode) was loaded onto a rotating disk electrode (d = 5 mm) and a pre-treated carbon paper electrode with a gas diffusion layer (1.6 cm * 1.6 cm). Rotating disk (RRDE) tests, basic electrochemical tests in an H-type electrolytic cell, and long-term stability tests in a flow cytometry tank were conducted in an H2SO4 electrolyte solution with a pH of 1. Figure 1 This is a high-resolution transmission electron microscope (TEM) image of the nitrogen-doped porous carbon catalyst in this embodiment. The prepared nitrogen-doped porous carbon catalyst has a layered structure and a certain degree of graphitization; for example... Figure 2 As shown, the H2O2 selectivity of the catalyst is expressed by the formula The calculated value is 97.9% (0V). RHE In the formula, Ir represents the ring current, Id represents the disk current, and N represents the electron trapping rate; for example... Figure 3 As shown, the catalytic electrode operates at approximately 500 mA cm⁻¹. -2 Operating at a current density in a flow reactor, it can continuously and stably produce hydrogen peroxide solution with a concentration of approximately 2 wt% for 100 hours.
[0044] Example 2
[0045] Figure 7 This is a schematic diagram of the preparation method of the nitrogen-doped porous carbon catalyst of the present invention, as shown below. Figure 7 As shown, a melamine and formaldehyde solution (37 wt%) with a mass ratio of 1:4 and surfactant PVP (mass ratio of PVP to melamine 1:1000) were added to a 100 mL round-bottom flask. The mixture was refluxed and stirred at 60 °C for 1 h to obtain a melamine resin solution. After cooling to room temperature, the solution was dissolved in 100 mL of 1 M NaOH ethanol solution. The solvent water and ethanol were removed by rotary evaporation. The mixture was then washed three times with water and ethanol, with the solvent removed by rotary evaporation after each wash, until the pH was neutral. This was the melamine resin. The solution was then heated using a tube furnace at 1 °C for 1 min. -1 The temperature was raised to 300℃ at a certain rate and held for 3 hours to obtain the nitrogen-doped porous carbon catalyst. The catalyst, binder, and solvent were mixed in a 1:2.5:1000 (mass ratio) and ultrasonically stirred to prepare a uniformly dispersed catalyst slurry. This slurry was then applied by drop-coating at doses of 0.25 mg / L. 催化剂 cm -2The load was applied to a rotating disk electrode (d = 5 mm) and a carbon felt electrode (1.6 cm * 1.6 cm) that had undergone hydrophobic pretreatment, and was used for rotating disk (RRDE) tests, basic electrochemical tests in an H-type electrolytic cell, and long-term stability tests in a flow cytometry cell.
[0046] Example 3
[0047] Figure 7 This is a schematic diagram of the preparation method of the nitrogen-doped porous carbon catalyst of the present invention, as shown below. Figure 7 As shown, a melamine and formaldehyde solution (10 wt%) with a mass ratio of 4:1 and a surfactant CTAB (CTAB to melamine mass ratio of 1:10) were added to a 100 mL round-bottom flask. The mixture was refluxed and stirred at 90 °C for 1 h to obtain a melamine resin solution. After cooling to room temperature, the solution was dissolved in 100 mL of 0.1 M NaOH ethanol solution. The solvent water and ethanol were removed by rotary evaporation. The mixture was then washed three times with water and ethanol, with the solvent removed by rotary evaporation after each wash, until the pH was neutral. This was the melamine resin. The solution was then heated using a tube furnace at 1 °C for 1 min. -1 The temperature was raised to 900℃ at a rate of [missing information] and held for 3 hours to obtain the nitrogen-doped porous carbon catalyst. The catalyst, binder, and solvent were mixed in a 30:20:1000 mass ratio and ultrasonically stirred to prepare a uniformly dispersed catalyst slurry. This slurry was then applied by drop-coating at a rate of 0.25 mg / L. 催化剂 cm -2 The load was applied to a rotating disk electrode (d = 5 mm) and a titanium felt electrode (1.6 cm * 1.6 cm) that had undergone hydrophobic pretreatment, and was used for rotating disk (RRDE) tests, basic electrochemical tests in an H-type electrolytic cell, and long-term stability tests in a flow cytometry cell.
[0048] Example 4
[0049] Figure 7 This is a schematic diagram of the preparation method of the nitrogen-doped porous carbon catalyst of the present invention, as shown below. Figure 7 As shown, a melamine and formaldehyde solution (60 wt%) with a mass ratio of 2:3 and the surfactant hexamethylenetetramine (mass ratio of hexamethylenetetramine to melamine) were added to a 100 mL round-bottom flask. The mixture was refluxed and stirred at 80 °C for 1 h to obtain a melamine resin solution. After cooling to room temperature, the solution was dissolved in 100 mL of 3M NaOH ethanol solution. The solvents, water and ethanol, were removed by rotary evaporation. The mixture was then washed three times with water and ethanol, with the solvent removed by rotary evaporation after each wash, until the pH was neutral. Finally, the solvent was removed by heating and evaporation, yielding the melamine resin. A tube furnace was used to heat the solution at 1 °C for 1 min. -1The temperature was raised to 600℃ at a rate of [missing information] and held for 3 hours to obtain the nitrogen-doped porous carbon catalyst. The catalyst, binder, and solvent were mixed in a 1:2.5:1000 (mass ratio) and ultrasonically stirred to prepare a uniformly dispersed catalyst slurry. This slurry was then applied by drop-coating at doses of 0.25 mg / L. 催化剂 cm -2 The load was applied to a rotating disk electrode (d = 5 mm) and a pre-treated carbon paper electrode (1.6 cm * 1.6 cm) with a gas diffusion layer, and subjected to rotating disk (RRDE) tests, basic electrochemical tests in an H-type electrolytic cell, and long-term stability tests in a flow cytometry cell.
[0050] Comparative Example 1
[0051] This comparative example is basically the same as Example 1, except that no surfactant is added when preparing the melamine resin. The results are as follows: Figure 4 As shown, the H2O2 selectivity of the catalyst is expressed by the formula The calculated value is 15.7% (0V). RHE From Example 1 and Comparative Example 1, it can be concluded that the surfactant, as a crosslinking agent, significantly improves the H2O2 selectivity of the nitrogen-doped porous carbon catalyst.
[0052] Comparative Example 2
[0053] This comparative example is basically the same as Example 1, except that the melamine resin was used directly as a catalyst without calcination. The results are as follows: Figure 5 As shown, the H2O2 selectivity of the catalyst is expressed by the formula The calculated value is 8.2% (0V). RHE From Example 1 and Comparative Example 2, it can be concluded that calcination is one of the key factors in improving the H2O2 selectivity of nitrogen-doped porous carbon catalysts.
[0054] Comparative Example 3
[0055] This comparative example is basically the same as Example 1, except that it was not washed with 100 mL of 1M NaOH ethanol solution, but was washed directly with water and ethanol in sequence, repeated three times. The results are as follows: Figure 6 As shown, the H2O2 selectivity of the catalyst is expressed by the formula The calculated value is 9.3% (0V). RHE ).
[0056] In summary, this invention discloses a method for preparing a nitrogen-doped porous carbon catalytic electrode and its application in the electrosynthesis of hydrogen peroxide. The method includes the following steps: polymerizing melamine and formaldehyde using a surfactant as a crosslinking agent, cleaning and removing the solvent, and then calcining to obtain a nitrogen-doped porous carbon catalyst; preparing the catalyst into a slurry and loading it onto an electrode substrate to obtain a catalytic electrode, which is then applied to the electrosynthesis of hydrogen peroxide. This invention uses a chemical polymerization method to prepare a nitrogen-doped porous carbon catalyst, constructing a layered porous carbon structure rich in various nitrogen-containing active sites. After being prepared into a catalytic electrode, it achieves an H2O2 selectivity of up to 97.9%, and at 500 mA cm⁻¹... -2 Operating at a current density in a flow reactor, it can continuously and stably produce a 2wt% hydrogen peroxide solution within 100 hours.
[0057] It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in these embodiments can be arbitrarily combined with each other.
Claims
1. A method for preparing a nitrogen-doped porous carbon catalytic electrode, characterized by, The method comprises the following steps: S1, mixing melamine with formaldehyde solution and adding a crosslinking agent for polymerization; cleaning with sodium hydroxide-ethanol solution, removing the solvent, and obtaining melamine resin; S2, calcining the melamine resin in step S1 to obtain a nitrogen-doped porous carbon catalyst; S3, preparing the nitrogen-doped porous carbon catalyst in step S2 into a nitrogen-doped porous carbon catalytic electrode.
2. The production method according to claim 1, characterized by, The concentration of the sodium hydroxide-ethanol solution is 0.1-3 mol L -1 .
3. The preparation method according to claim 1, characterized in that, The crosslinking agent comprises a surfactant, and the mass ratio of the surfactant to melamine is 1:10-1:1000.
4. The production method according to claim 3, characterized by, The surfactant comprises at least one of urotropin, poloxamer, cetyltrimethylammonium bromide, and polyvinylpyrrolidone.
5. The preparation method according to claim 1, characterized in that, The mass concentration of the formaldehyde solution is 10-60%, and the mass ratio of melamine to the formaldehyde solution is 1:4-4:
1.
6. The method of claim 1, wherein, The polymerization temperature is 60-90°C.
7. The preparation method according to claim 1, characterized in that, The calcination temperature in step S2 is 300-900°C. And / or, the preparation in step S3 comprises mixing the catalyst, a binder, and a solvent to prepare catalyst slurry and loading the catalyst slurry on a porous electrode substrate.
8. The preparation method according to claim 7, characterized in that, The mixing method comprises at least one of ultrasonic and stirring; And / or, the loading method comprises at least one of drop coating and spray coating; And / or, the mass ratio of the catalyst, the binder, and the solvent is 1:2.5:1000-30:20:1000.
9. A nitrogen-doped porous carbon catalytic electrode prepared by the method according to any one of claims 1-8.
10. Use of the nitrogen-doped porous carbon catalytic electrode according to claim 9 in electro-synthesizing hydrogen peroxide.