Method for producing h2o2 by electrocatalytic oxidation of water using rare earth metal-containing natural plants

Abstract

The application discloses a method for producing H2O2 by electrocatalytic water oxidation with rare earth-containing natural plants, and comprises the following steps: (1) planting super-enriched plants of American commercial land in a nutrient solution containing Nd, Ce, La or Ho rare earth elements to culture, simulating the rare earth metal absorption process in the rare earth waste tailings land and the contaminated farmland; (2) drying the raw material of the cultured American commercial land, obtaining a powder-shaped solid through N2 atmosphere calcination and grinding, and loading the powder-shaped solid on the surface of a carbon paper, a Ti sheet and an FTO conductive glass to prepare an electrode material containing rare earth metals; (3) taking the electrode material as an anode, taking a carbon rod as a cathode, and taking a mixed solution of potassium carbonate and potassium bicarbonate as an electrolyte, so that water oxidation reaction can occur under the condition of normal temperature, normal pressure and constant input voltage, and high-concentration H2O2 can be stably generated in a short time.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic water oxidation technology, and in particular, it relates to a method for preparing electrode materials from plants containing rare earth elements for electrocatalytic H2O2 production. Background Technology

[0002] Phytoremediation is a technology that utilizes plants with high accumulation capacity to remove target metals from metal-contaminated soils. Several plants have been identified as high-accumulators of rare earth elements (REEs), with American pokeweed (Phytolacca americana) showing great potential for REE accumulation due to its widespread distribution and rapid growth. However, how to rationally manage or utilize these REE-accumulating plants remains a challenging issue in phytoremediation. Given that REEs contain a 4f electron layer, which can effectively regulate electron transfer and enhance catalytic effects, using American pokeweed containing REEs as a raw material for electrocatalysts is of great significance.

[0003] If these plants can be used for electrocatalytic two-electron water oxidation to produce high-value-added oxidant H2O2, then plants with high accumulation of rare earth metals can be transformed from "waste" into treasure. The two-electron water oxidation technology using rare earth metal-containing American pokeweed plants as raw materials has many advantages: (1) When American pokeweed plants absorb rare earth elements, they achieve atomic-level dispersion and unique biological coordination of rare earth elements at the cellular level through chelating proteins and organic acids such as citric acid and malic acid in their bodies. After carbonization, this natural biological structure can be transformed into highly dispersed and efficient charge-transfer rare earth-non-metal heteroatom active sites. This structure cannot be replicated by traditional artificial physical mixing or chemical impregnation methods; (2) Renewable electrical energy is used as the energy input, and the reaction occurs at normal temperature and pressure. The reaction conditions are mild, low-carbon, and energy-saving; (3) This method essentially uses H2O as a raw material and does not require oxygen participation. It is suitable for oxygen-containing environments and oxygen-deficient environments such as deep soils in rare earth mining areas. Therefore, the synthesis of H2O2 by electrocatalytic water oxidation of rare earth metal-containing American pokeweed plants has great research prospects and practical significance. Summary of the Invention

[0004] Given the urgent need for the rational treatment or utilization of plants with high accumulation of rare earth metals, this invention aims to provide a method for producing hydrogen peroxide by electrocatalytic water oxidation using natural plants containing rare earth metals. The method utilizes nutrient solution cultivation, carbonization, and other methods to obtain natural plant electrocatalysts with specific rare earth-nonmetal heteroatom active sites, achieving hydrogen peroxide production levels that cannot be achieved by traditional artificial physical mixing or chemical impregnation methods. The method of this invention has advantages such as mild reaction conditions, low carbon and energy saving, and wide application scenarios.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for producing hydrogen peroxide by electrocatalytic water oxidation using rare earth metal-containing natural plants, the method comprising the following steps: (1) The hyperaccumulating plant Phytolacca americana was cultured in a nutrient solution containing rare earth elements such as Nd, Ce, Ho or La: After pre-culturing American pokeweed seedlings in Hogland nutrient solution for four weeks, select plants of uniform size and continue culturing them for 6-12 days in nutrient solution containing 50-200 μM rare earth elements (Nd, Ce, Ho or La). At harvest, American pokeweed is divided into three parts: roots, stems and leaves. Their fresh weight is recorded, and the plants are rinsed twice with deionized water and dried. (2) Using cultivated American pokeweed as raw material to produce electrocatalysts: The roots, stems and leaves of cultivated American pokeweed were dried and calcined at 400-800 ℃ for 1-2 h in N2 atmosphere to carbonize them. They were then ground into powder. 20-50 mg of roots, stems and leaves were then mixed with PVDF, carbon powder and NMP to obtain a viscous mixture. The mixture was then coated onto the surface of substrates such as carbon paper, Ti sheet and FTO conductive glass on a heating stage at 130-150 ℃ to form electrode materials. (3) The modified material electrocatalytically oxidizes water to produce H2O2: Using the electrode material described in step (2) as the anode, the carbon rod as the cathode, and the mixture of potassium carbonate and potassium bicarbonate as the electrolyte, the solution is heated at 1.7-3.2 V. vs Electrocatalysis of 2e under RHE voltage conditions - WOR can efficiently oxidize water to produce H2O2.

[0006] Preferably, the rare earth metal elements in step (1) include Nd, Ce, Ho or La, and the parts of the American pokeweed are the roots, stems and leaves.

[0007] Preferably, the concentration of rare earth metals in the nutrient solution in step (1) is 50-200 μM.

[0008] Preferably, the calcination temperature under N2 atmosphere in step (2) is 400-800 ℃ and the time is 2 h.

[0009] Preferably, in step (2), 20-50 mg of the stem of American pokeweed containing rare earth metals (Nd, Ce, Ho or La) is thoroughly stirred with carbon powder PVDF and NMP to obtain a viscous mixture.

[0010] Preferably, the heating temperature and time of the heating table in step (3) are 130-150 ℃ and 5-20 min.

[0011] Preferably, the electrolyte used in the electrocatalytic reaction in step (3) is a mixed solution of potassium carbonate and potassium bicarbonate.

[0012] Preferably, the input voltage for the electrocatalytic reaction in step (3) is 1.7-3.2 V. vs RHE, time is 30 minutes.

[0013] Compared with the prior art, this application has the following advantages: (1) Using natural plants containing rare earth metals, such as American pokeweed, as raw materials to prepare electrocatalysts can achieve hydrogen peroxide production that cannot be achieved by traditional artificial physical mixing or chemical impregnation methods. It has the advantage of turning "waste" into treasure and can even be further used in soil remediation, energy conversion and other processes. (2) Electrocatalytic water oxidation reaction uses renewable electrical energy as energy input, does not require high temperature and high pressure, has mild reaction conditions, and is green and low carbon. (3) This method uses H2O as a reactant to generate H2O2 in situ, which can get rid of the limitations of large-scale reaction facilities, and the reaction process does not require oxygen participation, making it suitable for oxygen-deficient environments such as deep soil in rare earth mining areas. Attached Figure Description

[0014] Figure 1 X-ray diffraction (XRD) patterns of roots of American pokeweed containing rare earth metals (Nd, Ce, Ho or La) obtained by nutrient solution culture; Figure 2 The Fourier Transform Infrared (FTIR) spectra of the roots of Phytolacca americana containing rare earth metals (Nd, Ce, Ho or La) obtained by nutrient solution culture; Figure 3 The roots of *Phytolacca americana* containing rare earth metals (Nd, Ce, Ho, or La) obtained by nutrient solution culture were kept at 1.8–3.3 V. vs Linear sweep voltammetry (LSV) performance within the RHE range; Figure 4 The roots of *Phytolacca americana* containing rare earth metals (Nd, Ce, Ho, or La) obtained through artificial physical mixing and nutrient solution culture were cultured at 3.2 V. vs Concentration of H2O2 produced by electrocatalytic water oxidation at RHE potential; Figure 5 The roots of *Phytolacca americana* containing rare earth metals (Nd, Ce, Ho, or La) obtained by nutrient solution culture were subjected to 3.2 V. vs Rate graph of electrocatalytic water oxidation to H2O2 at RHE potential; Figure 6 The roots of *Phytolacca americana* containing rare earth metals (Nd, Ce, Ho, or La) obtained by nutrient solution culture were subjected to 3.2 V. vs.Faraday efficiency (FE) of RHE electrocatalytic water oxidation to H2O2 production; Figure 7 The roots of *Phytolacca americana* containing rare earth metals (Nd) obtained by nutrient solution culture were subjected to 3.2 V. vs Stability effect of electrocatalytic water oxidation to H2O2 at RHE potential; Figure 8 Stems of *Phytolacca americana* containing rare earth metals (Nd, Ce, Ho, or La) obtained by nutrient solution culture were subjected to a temperature of 3.2 V. vs Concentration of H2O2 produced by electrocatalytic water oxidation at RHE potential; Figure 9 Leaves of *Phytolacca americana* containing rare earth metals (Nd, Ce, Ho, or La) obtained by nutrient solution culture were subjected to a temperature of 3.2 V. vs Concentration of H2O2 produced by electrocatalytic water oxidation at RHE potential; The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0015] The present invention will be further described below with reference to the accompanying drawings. It should be noted that the following embodiments are based on the present technical solution and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to these embodiments. Example

[0016] Cultivating American pokeweed using nutrient solutions containing rare earth elements (Nd, Ce, Ho, or La): After pre-culturing multiple American pokeweed seedlings in Hogland nutrient solution for four weeks, plants of uniform size were selected and cultured for another 6 days in nutrient solution containing 50 μM rare earth metals (Nd, Ce, Ho or La). The roots of several American pokeweed plants were harvested, their fresh weight was recorded, and they were rinsed twice with deionized water and dried. Example

[0017] Electrocatalysts were prepared using the roots of the American pokeweed plant. Step 1: Dry the roots of American pokeweed containing rare earth metals (Nd, Ce, Ho or La), calcine them at 500℃ for 2 h under N2 atmosphere to carbonize them, and grind them for 30 min to obtain powdered solid electrocatalyst material.

[0018] Step 2: X-ray diffraction and Fourier transform infrared spectroscopy were used to detect the crystal structure, functional groups and chemical bond characteristics of the electrocatalyst made from the roots of American pokeweed.

[0019] The results are as follows Figure 1 As shown in Figure 2, it can be seen that: Electrocatalysts made from the roots of American pokeweed containing rare earth metals (Nd, Ce, Ho or La) exhibit good crystallinity and obvious infrared characteristic peaks.

[0020] Therefore, this method can successfully transform American pokeweed containing rare earth metals (Nd, Ce, Ho or La) into a valuable resource, which can be used as an electrocatalyst for the production of H2O2. Example

[0021] Electrocatalysts were prepared using the stems of the American pokeweed plant. Step 1: Dry the stems of American pokeweed containing rare earth metals (Nd, Ce, Ho or La), calcine them at 500℃ for 2 h under N2 atmosphere to carbonize them, and grind them for 30 min to obtain powdered solid electrocatalyst material. Example

[0022] Electrocatalysts were prepared using leaves of the American pokeweed plant. Step 1: Dry the leaves of American pokeweed containing rare earth metals (Nd, Ce, Ho or La), calcine them at 500℃ for 2 h under N2 atmosphere to carbonize them, and grind them for 30 min to obtain powdered solid electrocatalyst material. Example

[0023] Supporting American pokeweed electrocatalysts on carbon paper, Ti sheets, and FTO conductive glass: 20 mg of an electrocatalyst made from the roots, stems, and leaves of *Phytolacca americana* (a rare earth metal, Nd, Ce, Ho, or La) was weighed and mixed with 13 mg PVDF, 3 mg carbon powder, and 200 µL NMP to obtain a viscous mixture. This mixture was then coated onto carbon paper, Ti sheets, and FTO conductive glass surfaces on a 130 °C heating stage to form electrode materials. The heating time was 10 min, and the loading area was 1 × 1 cm². 2 Thus, an anode electrode sheet containing rare earth metals from American pokeweed was obtained. Example

[0024] Hydrogen peroxide is produced by electrocatalytic oxidation of water using the roots of rare-earth metal-containing American pokeweed as the anode. Step 1: Using an electrode plate containing rare earth metals from the roots of *Phytolacca americana* as the anode, a carbon rod as the cathode, and a mixture of potassium carbonate and potassium bicarbonate as the electrolyte, an H-type electrolytic cell separated by a naphthol membrane was selected for the reaction, at a voltage of 1.8-3.3 V. vs Electrocatalytic reactions were carried out within the RHE voltage range, and LSV curves were obtained.

[0025] Step 2: Using a rare-earth metal-containing American pokeweed electrode sheet as the anode and a carbon rod as the cathode, in the reaction cell and electrolyte described in Step 1, at 3.2 V... vs The electrocatalytic water oxidation reaction was carried out at RHE potential for 30 min. The absorbance of H2O2 produced by the rare earth metal-containing pokeweed anode was detected by UV-Vis spectrophotometry, and the corresponding concentration, yield and FE value were calculated.

[0026] Step 3: Using a rare earth metal-containing American pokeweed electrode sheet as the anode and a carbon rod as the cathode, in the reaction cell and electrolyte described in Step 1, at 3.2 V... vs At RHE potential, a cyclic electrocatalytic water oxidation reaction with 8 electrolyte replacements was carried out.

[0027] The results are as follows Figure 3-7 As shown, it can be seen that: In 1.8-3.3 V vs Within the RHE voltage range, LSV performance is highest for Nd-containing pokeweed anodes, followed by Ce, Ho, and La, with the highest performance at 3.2 V. vs Under RHE voltage, the Nd-containing pokeweed anode exhibited the best performance in H2O2 production, achieving a concentration, rate, and FE of 45.28 mM, 103.80 µmol / min, and FE of H2O2 production within 30 min, respectively. -1 cm -2 The concentration produced was 87.80%, which was 2.03 times that of ordinary commercial carbon paper (22.28 mM) and 1.79 times that of physical mixing (25.28 mM). Next, the H2O2 production from high to low was Ce, Ho, and La. More specifically, at this voltage, the anode containing Nd-containing American pokeweed roots showed superior stability in 8 cycles of electrocatalytic water oxidation. Example

[0028] Hydrogen peroxide is produced by electrocatalytic oxidation of water using the stem of rare earth metal-containing American pokeweed as the anode. Step 1: Using an electrode plate containing rare earth metals from the stem of *Phytolacca americana* as the anode, a carbon rod as the cathode, and a mixture of potassium carbonate and potassium bicarbonate as the electrolyte, an H-type electrolytic cell separated by a naphthol membrane was selected for the reaction, at 3.2 V. vs The electrocatalytic water oxidation reaction was carried out at RHE potential for 30 min. The absorbance of H2O2 produced by the anode of the rare earth metal-containing American pokeweed stem was detected by ultraviolet-visible spectrophotometry, and the corresponding concentration was calculated.

[0029] The results are as follows Figure 8 As shown, it can be seen that: At 3.2 V vsUnder RHE voltage, the anodic H2O2 production performance of Nd-containing American pokeweed stems was the best, with a concentration of 37.34 mM produced within 30 min. This concentration was 1.68 times that of ordinary commercial carbon paper and 1.48 times that of physical mixing. The H2O2 production then decreased in the following order: Ce, Ho, and La. Example

[0030] Hydrogen peroxide is produced by electrocatalytic oxidation of water using rare earth metal-containing leaves of *Phytolacca americana* as the anode. Step 1: Using an electrode plate containing rare earth metals from the leaves of *Phytolacca americana* as the anode, a carbon rod as the cathode, and a mixture of potassium carbonate and potassium bicarbonate as the electrolyte, an H-type electrolytic cell separated by a naphthol membrane was selected for the reaction, at 3.2 V. vs The electrocatalytic water oxidation reaction was carried out at RHE potential for 30 min. The absorbance of H2O2 produced by the anode of the rare earth metal-containing pokeweed leaf was detected by ultraviolet-visible spectrophotometry, and the corresponding concentration was calculated.

[0031] The results are as follows Figure 8 As shown, it can be seen that: At 3.2 V vs Under RHE voltage, the anodic H2O2 production performance of Nd-containing American pokeweed leaves was the best, with a concentration of 42.98 mM produced within 30 min. This concentration was 1.93 times that of ordinary commercial carbon paper (22.28 mM) and 1.70 times that of physical mixing. The H2O2 production then decreased in the following order: Ce, Ho, and La.

[0032] Therefore, this method uses rare earth metal-containing American pokeweed as an electrocatalyst, which can turn waste into treasure and achieve excellent electrochemical performance and efficient and stable electrocatalytic water oxidation to H2O2 production.

[0033] In summary, it can be seen that this invention uses rare earth metal-containing American pokeweed as an electrocatalyst for the electrocatalytic oxidation of two-electron water to produce high-value-added oxidant H2O2, turning a plant with high accumulation of rare earth metals into a valuable resource. It achieves H2O2 production levels that traditional artificial physical mixing or chemical impregnation methods cannot reach. It is characterized by low carbon and energy saving, and has a wide range of applications, and has great research prospects and practical significance.

[0034] For those skilled in the art, various corresponding changes and modifications can be made based on the above technical solutions and concepts, and all such changes and modifications should be included within the protection scope of the claims of this invention.

Claims

1. A method for producing H2O2 by electrocatalytic water oxidation using natural plants containing rare earth metals, the method comprising the following steps: (1) The hyperaccumulating plant Phytolacca americana was cultured in a nutrient solution containing rare earth elements such as Nd, Ce, Ho or La: After pre-culturing American pokeweed seedlings in Hogland nutrient solution for four weeks, select plants of uniform size and continue culturing them for 6-12 days in nutrient solution containing 50-200 μM rare earth elements (Nd, Ce, Ho or La). At harvest, American pokeweed is divided into three parts: roots, stems and leaves. Their fresh weight is recorded, and the plants are rinsed twice with deionized water and dried. (2) Using cultivated American pokeweed as raw material to produce electrocatalysts: The roots, stems, and leaves of cultivated American pokeweed were dried separately and calcined at 400-800 ℃ for 1-2 h under N2 atmosphere to carbonize them. They were then ground into powder solids. 20-50 mg of the roots, stems, and leaves were then mixed with the binder polyvinylidene fluoride (PVDF), carbon powder, and N-methylpyrrolidone (NMP) to obtain a viscous mixture. This mixture was then coated onto the surface of substrates such as carbon paper, Ti sheets, and FTO conductive glass on a heating stage at 130-150 ℃ to form electrode materials. The heating time was 5-20 min. (3) The modified material electrocatalytically oxidizes water to produce H2O2: Using the electrode material described in step (2) as the anode, the carbon rod as the cathode, and the electrolyte as a mixture of potassium carbonate and potassium bicarbonate, at 1.7-3.2 V... vs Electrocatalysis of 2e under RHE voltage conditions - WOR can efficiently and stably produce H2O2 through water oxidation.

2. The method for producing H2O2 by electrocatalytic water oxidation using rare earth metal-containing natural plants according to claim 1, characterized in that, The rare earth element in step (1) is selected from at least one of Nd, Ce, Ho or La.

3. The method for producing H2O2 by electrocatalytic water oxidation using rare earth metal-containing natural plants according to claim 1, characterized in that, The concentration of rare earth metals in the nutrient solution in step (1) is 50-200 μM.

4. The method for producing H2O2 by electrocatalytic water oxidation using rare earth metal-containing natural plants according to claim 1, characterized in that, The American pokeweed harvested in step (1) consists of three parts: roots, stems, and leaves.

5. The method for producing H2O2 by electrocatalytic water oxidation using rare earth metal-containing natural plants according to claim 1, characterized in that, In step (2), the calcination temperature under N2 atmosphere is 400-800 ℃ and the time is 1-2 h.

6. The method for producing H2O2 by electrocatalytic water oxidation using rare earth metal-containing natural plants according to claim 1, characterized in that, In step (2), the electrode material includes roots, stems and leaves of American pokeweed containing Nd, Ce, Ho or La and plants without rare earth metals (CK). 20-50 mg of root, stem or leaf powder is thoroughly stirred with carbon powder, PVDF and NMP to obtain a viscous mixture, which is then loaded onto the surface of substrates such as carbon paper, Ti sheet and FTO conductive glass.

7. The method for producing H2O2 by electrocatalytic water oxidation using rare earth metal-containing natural plants according to claim 1, characterized in that, The heating temperature and time of the heating table in step (2) are 130-150 ℃ and 5-20 min.

8. The method for producing H2O2 by electrocatalytic water oxidation using rare earth metal-containing natural plants according to claim 1, characterized in that, The electrolyte used in the electrocatalytic reaction in step (3) is a mixed solution of potassium carbonate and potassium bicarbonate.

9. The method for producing H2O2 by electrocatalytic water oxidation using rare earth metal-containing natural plants according to claim 1, characterized in that, The input voltage for the electrocatalytic reaction in step (3) is 1.7-3.2 V. vs RHE.

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