Preparation method of phosphorus-doped porous biochar and application of the phosphorus-doped porous biochar in electrocatalytic production of hydrogen peroxide

Abstract

The application discloses a preparation method of phosphorus-doped porous biochar and application of the phosphorus-doped porous biochar in electrocatalytic production of hydrogen peroxide, and belongs to the field of environmental energy. The material takes the seeds of arbor plants such as ficus microcarpa as a biomass precursor, extracts valuable fatty acids in the seeds through a phosphoric acid hydrothermal reaction, collects the remaining phosphorus-rich biomass residues, and calcines the phosphorus-rich biomass residues under high-temperature conditions to simultaneously complete heteroatom doping and etching pore-making of the biochar, and construct rich nitrogen and phosphorus double active sites in the crosslinked pore channels of the biochar. When the material is applied to an oxygen reduction reaction cathode material, H2O2 can be quickly generated with high selectivity and current efficiency. The method is simple to implement, low in cost, and high in reusability, and has a wide application prospect in the field of biomass resource utilization and environmental energy.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical water treatment technology, specifically relating to a method for preparing phosphorus-doped porous biochar and its application in the electrocatalytic production of hydrogen peroxide. Background Technology

[0002] In the field of water treatment, hydrogen peroxide (H2O2) has been widely used to remove organic pollutants and pathogenic microorganisms from water. Its decomposition end products are H2O and O2, making it a clean and environmentally friendly oxidant. However, current traditional hydrogen peroxide production methods suffer from high energy consumption, severe environmental pollution, and complex equipment. Furthermore, high concentrations of H2O2 pose potential safety risks during storage, transportation, and use, presenting a serious challenge to the water treatment industry.

[0003] In recent years, the electrochemical method has been considered a highly promising way to produce H2O2, where oxygen can be selectively reduced at the electrode surface (2e2O2). - The oxygen reduction reaction (ORR) produces H₂O₂. However, a key challenge of this method is finding an efficient and stable ORR catalyst to improve the selectivity and yield of hydrogen peroxide. Currently, using noble metals such as platinum and palladium as catalysts is a common method to achieve efficient ORR. However, the high price of noble metals limits their widespread application, and the ORR selectivity and activity of these noble metal catalysts are severely affected by the reaction environment, resulting in low applicability of noble metal-based ORR catalysts in water treatment fields with complex water quality conditions. Against this backdrop, carbon-based materials are widely considered a promising 2e⁻ catalyst due to their abundant sources, low cost, and excellent electrochemical performance. - ORR electrode materials. Through reasonable physical and chemical regulation, the porosity and surface functional group content of carbon materials can be effectively improved, thereby enhancing their ORR activity and selectivity. However, carbon materials generally face instability issues after long-term operation; changes in surface functional groups and the collapse of pore structures lead to a decrease in the efficiency of H2O2 electrocatalytic production. Therefore, as electrode materials are consumables, developing stable, controllable, economical, and environmentally friendly porous carbon material preparation processes is crucial for promoting the application of carbon materials in the field of H2O2 electrocatalytic production.

[0004] Biomass, as a renewable resource, is rich in carbon and other elements, making it an ideal precursor for carbon-based electrode materials. Developing economical and efficient biomass resource utilization methods is crucial for the practical application of biochar. *Firmiana simplex*, belonging to the Malvaceae family, has seeds rich in fatty acids such as palmitic acid, oleic acid, and linoleic acid, with an oil content exceeding 50%, making it a promising new oilseed. However, both chemical and physical extraction processes for fatty acids from *Firmiana simplex* seeds have low utilization rates of the biomass solid residue, reducing the overall bioavailability of the seeds. Acid hydrolysis of biomass can not only extract valuable fatty acid resources, but the biomass waste enriched with heteroatoms can also serve as a precursor for biochar. By controlling porosity and surface functional groups, heteroatom-doped porous biochar can be produced, showing promise as a highly efficient 2e-electrode biochar. - ORR electrode materials can significantly improve the comprehensive utilization rate of biomass resource utilization processes, and have strong feasibility and practical application value. Summary of the Invention

[0005] To address the aforementioned problems, this invention discloses a method for preparing phosphorus-doped porous biochar and its application in the electrocatalytic production of hydrogen peroxide. The method utilizes phosphoric acid hydrolysis to release fatty acids from *Pterocarya stenoptera* seeds. After recovering the fatty acids from the hydrolysate using an organic extractant, the separated solid residue is further calcined. Phosphorus enriched in biomass is used as a pore-forming agent and heteroatom precursor to prepare phosphorus-doped porous biochar material, which is then used as a 2e... - ORR electrode materials efficiently produce H2O2, thereby enabling the rapid generation and utilization of H2O2.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for preparing phosphorus-doped porous biochar, the specific steps of which are as follows:

[0008] (1) Hydrothermal treatment of dried sycamore seeds: The dried sycamore seeds were immersed in phosphoric acid solution and then heated in a sealed hydrothermal reactor for hydrolysis. After separating the solid, a phosphorus-rich biomass precursor was obtained.

[0009] (2) Extraction of fatty acids: The hydrolysate in step (1) is centrifuged, and the supernatant is placed in a vacuum drying oven. Then, the supernatant is extracted with an organic solvent. After standing, an organic solvent layer containing fatty acids is obtained. Finally, the organic solvent is evaporated to obtain concentrated fatty acids.

[0010] (3) Preparation of phosphorus-doped porous biochar: The phosphorus-rich biomass precursor obtained in step (1) was dried in a vacuum drying oven, then placed in a tube furnace for calcination, and after cooling, it was repeatedly washed with ethanol and deionized water to obtain phosphorus-doped porous biochar.

[0011] As an improvement of the present invention, the moisture content of the dried sycamore seeds in step (1) is 10%~80%.

[0012] As an improvement of the present invention, in step (1), the mass ratio of dried tung seeds to phosphoric acid solution is 0.2~4:1, and the concentration of phosphoric acid solution is 5g / L~20g / L.

[0013] As an improvement of the present invention, the hydrothermal reaction heating and hydrolysis temperature in step (1) is 120~200℃, and the heating and hydrolysis reaction time is 8~20h.

[0014] As an improvement of the present invention, in step (2), the centrifugation speed of the hydrolysate is 2000~8000 rpm, the vacuum drying time is 2~12 h, and the vacuum drying temperature is 45~80℃.

[0015] As an improvement of the present invention, the extractant in step (2) includes, but is not limited to, chloroform, n-hexane, petroleum ether, etc., the volume ratio of extractant to hydrolysate is 2~10:1, and the evaporation temperature is 50~80℃.

[0016] As an improvement of the present invention, the vacuum drying temperature in step (3) is 45~80℃ and the vacuum drying time is 6~20h.

[0017] As an improvement of the present invention, the calcination temperature in step (3) is 500~1000℃ and the calcination time is 0.5~4h.

[0018] This invention also provides an application of phosphorus-doped porous biochar prepared by any of the above methods in the electrocatalytic production of hydrogen peroxide.

[0019] As an improvement of the present invention, the phosphorus-doped porous biochar can be used as a cathode material for oxygen reduction reaction to generate hydrogen peroxide in situ, and can be applied to the removal of organic pollutants in water and the elimination of pathogens in water.

[0020] The beneficial effects of this invention are as follows:

[0021] Compared with traditional biomass-based biochar preparation methods, this invention utilizes phosphoric acid hydrolysis to extract natural fatty acid resources from biomass while simultaneously using phosphorus enriched in the natural pores of biomass residue as a pore-forming agent. This makes it an ideal precursor for biochar preparation, resulting in phosphorus-doped porous biochar with excellent 2e... - ORR activity enables the diversified resource utilization of biomass, and its specific advantages are as follows:

[0022] 1. This invention utilizes novel biomass as a precursor for both fatty acid oilseeds and biochar electrode materials, significantly improving the comprehensive utilization rate of biomass and the added value of the products.

[0023] 2. During the process of extracting fatty acids from tung seeds by phosphate hydrolysis, phosphate is also fully absorbed by biomass, providing both a pore-forming agent and a heteroatom precursor for subsequent heteroatom-doped porous carbon materials;

[0024] 3. Phosphorus-doped porous biochar prepared from biomass residue can be finely controlled by adjusting the concentration of phosphoric acid, hydrolysis time, and calcination temperature to finely regulate the pore structure and surface functional groups of the material, thereby improving the yield and current efficiency of the electrocatalytic production of H2O2. Attached Figure Description

[0025] Figure 1 The effects of different phosphoric acid concentrations on the electrocatalytic production of H2O2 by phosphorus-doped porous biochar in Examples 2-6 of this invention are shown.

[0026] Figure 2 This invention relates to the effect of different calcination temperatures in Examples 4 and 7-10 on the electrocatalytic production of H2O2 from phosphorus-doped porous biochar. Detailed Implementation

[0027] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0028] Example 1: Preparation of phosphorus-doped porous biochar (HPC / 0.5 / 700)

[0029] (1) Hydrothermal treatment of dried sycamore seeds: 1 g of dried sycamore seeds and 0.5 g of phosphoric acid were mixed in 80 mL of deionized water and hydrolyzed in a hydrothermal reactor at 180 °C for 12 h.

[0030] (2) Extraction of fatty acids: After cooling the above hydrolysate, centrifuge at 2000 rpm, place the supernatant in a vacuum drying oven and dry for 24 h, then use 100 mL of n-hexane as the extractant to extract and separate the dried supernatant and recover the fatty acids.

[0031] (3) Preparation of phosphorus-doped porous biochar: Phosphorus-rich biomass residue was vacuum dried and placed in a tube furnace, calcined at 700℃ for 3 h under an argon flow. After cooling, it was repeatedly washed with ethanol and deionized water, and finally dried to obtain HPC / 0.5 / 700. In HPC / 0.5 / 700, the suffixes 0.5 and 700 represent the mass ratio of phosphoric acid to tung seeds and the calcination temperature, respectively.

[0032] Example 2: Electrocatalytic production of H2O2 from phosphorus-doped porous biochar (HPC / 0.5 / 700)

[0033] (1) The preparation steps of phosphorus-doped porous biochar are the same as in Example 1.

[0034] (2) Online production of H2O2 by oxygen reduction was carried out in a 25 mL gas electrode reactor. 10 mg HPC / 0.5 / 700 was loaded onto the surface of carbon cloth as the working electrode. The reaction was run in a three-electrode system with a saturated calomel electrode as the reference electrode and a platinum mesh as the counter electrode, E = -0.5 (vs SCE). O2 was introduced into the gas chamber of the reactor at a flow rate of 50 mL / min. 0.05 mM Na2SO4 was used as the supporting electrolyte, and the reaction was carried out under neutral conditions. The accumulation of H2O2 in the reactor over time is shown in the figure. Figure 1 As shown.

[0035] Example 3: Electrocatalytic production of H2O2 from phosphorus-doped porous biochar (HPC / 1 / 700)

[0036] The difference between this embodiment and Embodiment 2 is that the mass ratio of phosphoric acid to tung oil seeds is 1:1 during the preparation of phosphorus-doped porous biochar, and the accumulation of H2O2 in the reactor over time is as follows. Figure 1 As shown.

[0037] Example 4: Electrocatalytic production of H2O2 from phosphorus-doped porous biochar (HPC / 2 / 700)

[0038] The difference between this embodiment and Embodiment 2 is that the mass ratio of phosphoric acid to tung oil seeds is 1:2 during the preparation of phosphorus-doped porous biochar, and the accumulation of H2O2 in the reactor over time is as follows. Figure 1 As shown, the accumulation of H2O2 in the reactor over time is as follows: Figure 2 As shown.

[0039] Example 5: Electrocatalytic production of H2O2 from phosphorus-doped porous biochar (HPC / 3 / 700)

[0040] The difference between this embodiment and Embodiment 2 is that the mass ratio of phosphoric acid to tung oil seeds is 1:3 during the preparation of phosphorus-doped porous biochar, and the accumulation of H2O2 in the reactor over time is as follows. Figure 1 As shown.

[0041] Example 6: Electrocatalytic production of H2O2 from phosphorus-doped porous biochar (HPC / 4 / 700)

[0042] The difference between this embodiment and Embodiment 2 is that the mass ratio of phosphoric acid to tung oil seeds is 1:4 during the preparation of phosphorus-doped porous biochar, and the accumulation of H2O2 in the reactor over time is as follows. Figure 1 As shown.

[0043] Example 7: Electrocatalytic production of H2O2 from phosphorus-doped porous biochar (HPC / 2 / 500)

[0044] The difference between this embodiment and Embodiment 4 is that the calcination temperature in the preparation process of phosphorus-doped porous biochar is 500℃, and the accumulation of H2O2 in the reactor over time is as follows. Figure 2 As shown.

[0045] Example 8: Electrocatalytic production of H2O2 from phosphorus-doped porous biochar (HPC / 2 / 600)

[0046] The difference between this embodiment and Embodiment 4 is that the calcination temperature in the preparation process of phosphorus-doped porous biochar is 600℃, and the accumulation of H2O2 in the reactor over time is as follows. Figure 2 As shown.

[0047] Example 9: Electrocatalytic production of H2O2 from phosphorus-doped porous biochar (HPC / 2 / 800)

[0048] The difference between this embodiment and Embodiment 4 is that the calcination temperature in the preparation process of phosphorus-doped porous biochar is 800℃, and the accumulation of H2O2 in the reactor over time is as follows. Figure 2 As shown.

[0049] Example 10: Electrocatalytic production of H2O2 from phosphorus-doped porous biochar (HPC / 2 / 900)

[0050] The difference between this embodiment and Embodiment 4 is that the calcination temperature in the preparation process of phosphorus-doped porous biochar is 900℃, and the accumulation of H2O2 in the reactor over time is as follows. Figure 2 As shown.

[0051] It should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. For those skilled in the art, several improvements and modifications can be made on the basis of the above embodiments without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing phosphorus-doped porous biochar, characterized in that, The specific steps are as follows: (1) Hydrothermal treatment of dried sycamore seeds: The dried sycamore seeds were immersed in phosphoric acid solution and then heated in a sealed hydrothermal reactor for hydrolysis. After separating the solid, a phosphorus-rich biomass precursor was obtained. (2) Extraction of fatty acids: The hydrolysate in step (1) is centrifuged at a speed of 2000-8000 rpm. The supernatant is placed in a vacuum drying oven for 2-12 hours at a temperature of 45-80°C. The supernatant is then extracted with an organic solvent, which can be any one of chloroform, n-hexane, or petroleum ether. The volume ratio of the extractant to the hydrolysate is 2-10:

1. The mixture is allowed to stand to obtain an organic solvent layer containing fatty acids. Finally, the organic solvent is evaporated to obtain concentrated fatty acids at a temperature of 50-80°C. (3) Preparation of phosphorus-doped porous biochar: The phosphorus-rich biomass precursor obtained in step (1) was dried in a vacuum drying oven, then placed in a tube furnace for calcination, and after cooling, it was repeatedly washed with ethanol and deionized water to obtain phosphorus-doped porous biochar.

2. The method for preparing phosphorus-doped porous biochar according to claim 1, characterized in that: In step (1), the moisture content of the dried sycamore seeds is 10%~80%.

3. The method for preparing phosphorus-doped porous biochar according to claim 1, characterized in that: In step (1), the mass ratio of dried sycamore seeds to phosphoric acid solution is 0.2~4:1, and the concentration of phosphoric acid solution is 5g / L~20g / L.

4. The method for preparing phosphorus-doped porous biochar according to claim 1, characterized in that: In step (1), the hydrothermal reaction heating and hydrolysis temperature is 120~200℃, and the heating and hydrolysis reaction time is 8~20h.

5. The method for preparing phosphorus-doped porous biochar according to claim 1, characterized in that: In step (3), the vacuum drying temperature is 45~80℃ and the vacuum drying time is 6~20h.

6. The method for preparing phosphorus-doped porous biochar according to claim 1, characterized in that: In step (3), the calcination temperature is 500~1000℃ and the calcination time is 0.5~4h.

7. The application of phosphorus-doped porous biochar prepared by any one of claims 1-6 in the electrocatalytic production of hydrogen peroxide.

8. The application of the phosphorus-doped porous biochar according to claim 7 in the electrocatalytic production of hydrogen peroxide, characterized in that: The phosphorus-doped porous biochar is used as a cathode material for the oxygen reduction reaction to generate hydrogen peroxide in situ. The hydrogen peroxide is then applied to the removal of organic pollutants from water and the elimination of pathogens in water.

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