[0070] Example 2
[0071] Preparation method and performance test of cyclodextrin porous carbon-based nitrogen reduction catalyst:
[0072] (1) Weigh 2g of β-cyclodextrin, 120ml of deionized water, mix and stir, place it in 50ml of polytetrafluoroethylene lining for hydrothermal pretreatment, and treat at a hydrothermal temperature of 220°C for 6 hours, and wait for the reaction to end After the reaction system temperature is lowered to room temperature, the pretreated cyclodextrin-based carbon material is obtained;
[0073] (2) According to CoCl 3 mixed with the pretreated cyclodextrin-based carbon material in a mass ratio of 1:1, in N 2 Heating at a heating rate of 5 °C/min to a constant temperature of 800 °C for 2 h in an atmosphere to obtain a carbonized cyclodextrin-based carbon material;
[0074] (3) when cooling to room temperature, remove the metal compound in the cyclodextrin-based carbon material with HCl with a concentration of 2M, and use deionized water to wash 5 times, and dry to obtain a cyclodextrin porous carbon-based nitrogen reduction catalyst;
[0075] Performance test of cyclodextrin porous carbon-based nitrogen reduction catalyst:
[0076] (4) Mix the cyclodextrin-based carbon material and the anhydrous ethanol dispersant in a 10ml strain bottle and ultrasonicate for 30min, then add 50μl of the film-forming agent Nafion and ultrasonicate for 20min to obtain a nitrogen reduction catalyst suspension;
[0077] (5) Use a pipette to measure 10 μl of the nitrogen reduction catalyst suspension prepared in proportion and evenly drop it on the cutting area of 1*1cm -2 On the commercial carbon cloth, bake with infrared light for 1-2min, using Na concentration of 0.05M 2 SO 4 The solution was used as the electrolyte to prepare a three-electrode system. The linear sweep voltammetry curve of the prepared cyclodextrin porous carbon-based nitrogen reduction catalyst was tested under the condition of potential window of 0.4~-0.8V and scanning speed of 5mV/s.
[0078] (6) Take 2ml of the electrolyte after the cyclodextrin porous carbon-based nitrogen reduction catalyst has been operated for 2h, add 2ml of 1mol/L sodium hydroxide solution (which contains 5wt% salicylic acid and 5wt% sodium citrate dihydrate), and then add 1ml of 0.05mol/L sodium hypochlorite solution, finally add 0.2ml of 5wt% sodium nitroprusside dihydrate solution, stand for 2 hours at room temperature and dark for color development, and then use a UV-Vis spectrophotometer to perform spectral scanning in the wavelength range of 550-750nm, and Record the absorbance value at 655nm and combine it with the working curve to finally get the ammonia concentration. After data processing and calculation, the ammonia production rate and Faradaic efficiency of electrocatalytic ammonia production are obtained.
[0079] figure 1 and image 3 The scanning electron microscope images of the chitin porous carbon-based nitrogen reduction catalyst and the cyclodextrin porous carbon-based nitrogen reduction catalyst prepared in Example 1 and Example 2, respectively, are represented by figure 1 It can be seen that the chitin porous carbon-based nitrogen reduction catalyst after adding the pore-forming agent contains a large number of micropores and mesopores; image 3 It can be seen that the cyclodextrin porous carbon-based nitrogen reduction catalyst prepared in Example 2 is carbon spherical, but because no pore-forming agent is added, it cannot be seen that there are micropores and mesopores in the cyclodextrin porous carbon-based nitrogen reduction catalyst. .
[0080] figure 2 and Figure 4 The linear sweep voltammetry curves of the chitin porous carbon-based nitrogen reduction catalyst and the cyclodextrin porous carbon-based nitrogen reduction catalyst prepared in Example 1 and Example 2 under nitrogen and argon atmospheres, respectively. Figure 5 Linear sweep voltammograms of commercial Pt/C catalysts under nitrogen and argon atmospheres. from figure 2 , Figure 4 as well as Figure 5 It can be seen that the prepared chitin porous carbon-based nitrogen reduction catalyst and cyclodextrin porous carbon-based nitrogen reduction catalyst have larger initial potential and limit under nitrogen and argon atmosphere compared to the existing commercial Pt/C catalysts. current density. However, the initial potential and limiting current density of the chitin porous carbon-based nitrogen reduction catalyst were better than those of the cyclodextrin porous carbon-based nitrogen reduction catalyst due to the addition of a pore-forming agent.
[0081] Image 6 with ammonium chloride as the standard reagent in 0.05M Na 2 SO 4 The solution was prepared with 0, 0.25, 0.5, 1 μg/ml ammonium chloride standard solution, respectively, and the ultraviolet spectrum of the test after color reaction. Figure 7 It is a standard curve obtained by plotting the absorbance at 655nm with the concentration of 0, 0.25, 0.5, 1μg/ml ammonium chloride standard solution after color reaction.
[0082] Figure 8 These are the UV spectra of the chitin porous carbon-based nitrogen reduction catalyst prepared in Example 1 and Example 2, the cyclodextrin porous carbon-based nitrogen reduction catalyst and the commercial Pt/C catalyst after running for 2 hours. Figure 9 The ammonia production rate and Faradaic efficiency of the chitin porous carbon-based nitrogen reduction catalyst and the cyclodextrin porous carbon-based nitrogen reduction catalyst prepared in Example 1 and Example 2, as well as the commercial Pt/C catalyst. from Figure 9 It can be seen that, after calculation, the ammonia production rate and Faradaic efficiency of the chitin porous carbon-based nitrogen reduction catalyst and the cyclodextrin porous carbon-based nitrogen reduction catalyst prepared in Example 1 and Example 2 are compared with those of the commercial Pt/C catalyst. higher. Among them, the chitin porous carbon-based nitrogen reduction catalyst has an ammonia production rate of up to 26ug due to the addition of a pore-forming agent. NH3 h -1 mg -1 cat , the Faraday efficiency is 9%.
[0083] To sum up, the present invention discloses a preparation method and application of a porous carbon-based nitrogen reduction catalyst. The preparation method includes pretreating a macromolecular raw material containing glucose units to obtain a pretreated macromolecular material; After the pretreated polymer material is mixed with a pore-forming agent and a catalyst, carbonization is carried out under the protection of an inert gas to obtain a porous carbon material; the porous carbon material is washed with acid and deionized water in sequence, and then dried by blasting , a carbon-based nitrogen reduction catalyst was obtained. In the invention, the macromolecule containing glucose unit is used as the raw material, and the transition metal is coordinatively anchored to form a single atom to obtain multiple active centers; the pore-forming agent is calcined and carbonized to obtain a high specific surface area porous carbon-based nitrogen reduction catalyst, which enhances the non-toxicity of the carbon material. The nitrogen reduction performance of the noble metal catalyst enables the preparation of a low-cost, high catalytic activity nitrogen reduction catalyst under relatively mild, safe and environmentally friendly conditions.
