Preparation method of Er-doped BiOBr for electrocatalytic reduction of oxygen

Abstract

The invention discloses a preparation method of Er-doped BiOBr for electrocatalytic reduction of oxygen, and relates to the technical field of electrocatalyst preparation, the preparation method comprises the following steps: S100, preparing a precursor solution: S101, accurately weighing a proper amount of a bismuth (Bi) precursor and an erbium (Er) precursor, calculating the required mass according to a target doping ratio (x%), mixing the bismuth (Bi) precursor and the erbium (Er) precursor in a proper amount of deionized water, and preparing an Er-doped BiOBr precursor solution; the Er-doped BiOBr material with high catalytic activity is successfully synthesized by accurately controlling the doping proportion of Er and the reaction conditions of the precursor, the energy band structure and electron arrangement of BiOBr are effectively adjusted by introducing the Er element, transmission and separation of charges are promoted, and the catalytic activity of the Er-doped BiOBr material is improved. Therefore, the efficiency of the material in the electrocatalytic reduction oxygen reaction is remarkably improved, and fine regulation and control on the morphology and dispersity of the product are realized by adding a proper amount of surfactant (such as polyvinylpyrrolidone) and controlling the stirring time.

Description

Technical Field

[0001] The invention relates to the technical field of electrocatalyst preparation, and in particular to a method for preparing Er-doped BiOBr for electrocatalytic reduction of oxygen. Background Art

[0002] In the current field of electrocatalytic reduction of oxygen, although a variety of catalysts have been studied and applied, their catalytic efficiency and stability still need to be improved. Although traditional BiOBr materials have certain catalytic properties, in practical applications, their efficiency in electrocatalytic reduction of oxygen is often limited due to their shortcomings such as uneven surface structure and limited active sites. In addition, BiOBr materials are prone to agglomeration and deactivation during long-term use, further reducing their catalytic performance and service life.

[0003] In response to the above problems, researchers have tried to improve the catalytic performance of BiOBr materials through different modification methods. However, some existing modification methods have the disadvantages of complex operation, high cost or insignificant modification effect, which are difficult to meet the needs of industrial applications. Therefore, developing a simple, efficient and cost-controlled BiOBr modification method to improve its efficiency and stability in electrocatalytic reduction of oxygen has become a hot topic and difficulty in current research.

[0004] Based on the above background, this paper proposes a method for preparing Er-doped BiOBr for electrocatalytic reduction of oxygen. By introducing Er element for doping modification, the aim is to optimize the surface structure of BiOBr material, increase active sites, and improve its dispersibility and stability, thereby significantly improving its efficiency and performance of electrocatalytic reduction of oxygen. Summary of the invention

[0005] The purpose of the present invention is to make up for the deficiencies of the prior art and provide a method for preparing Er-doped BiOBr for electrocatalytic reduction of oxygen. By precisely controlling the doping ratio of Er and the reaction conditions of the precursor, Er-doped BiOBr materials with high catalytic activity are successfully synthesized. The introduction of the Er element effectively regulates the energy band structure and electronic configuration of BiOBr, promotes the transfer and separation of charges, and thus significantly improves the efficiency of the material in the electrocatalytic reduction of oxygen reaction. By adding an appropriate amount of surfactant (such as polyvinyl pyrrolidone) and controlling its stirring time, fine regulation of the morphology and dispersibility of the product is achieved. The presence of the surfactant helps to reduce the agglomeration between particles and form uniformly dispersed, regular-shaped Er-doped BiOBr nanoparticles. This optimized morphology and dispersibility not only increase the specific surface area of ​​the material and increase the catalytic active sites, but also help to improve the stability and reusability of the catalyst.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A method for preparing Er-doped BiOBr for electrocatalytic reduction of oxygen, the preparation method comprising:

[0008] S100, prepare precursor solution:

[0009] S101: Accurately weigh appropriate amounts of bismuth (Bi) precursor and erbium (Er) precursor, calculate the required mass according to the target doping ratio (x%), mix the two in an appropriate amount of deionized water, and ensure that the precursors are completely dissolved and evenly dispersed by magnetic stirring or ultrasonic treatment;

[0010] S102: Select a suitable surfactant, add it to the mixed solution in a certain proportion, and continue stirring until the surfactant is completely dissolved to form a uniform solution system. The role of the surfactant is to regulate the morphology and dispersibility of the product;

[0011] S200, add bromine (Br) precursor and mix:

[0012] S201: preparing a bromine (Br) precursor solution of a certain concentration to ensure that the amount of bromide ions is sufficient to completely react with bismuth ions to form BiOBr;

[0013] S202: under continuous stirring, slowly drop the bromine precursor solution into the mixed solution containing Bi and Er precursors, and pay attention to controlling the dropping speed during the dropping process to avoid excessive local concentration;

[0014] S203: Continue stirring the mixed solution for a period of time to ensure that all ions are fully mixed and uniformly formed to form a uniform precursor solution of Bi, Er and Br;

[0015] S300, hydrothermal reaction:

[0016] S301: transferring the mixed solution to a polytetrafluoroethylene-lined reactor, sealing it and placing it in a hydrothermal reaction box;

[0017] S302: setting the reaction temperature (e.g., 120° C. to 180° C.) and the reaction time (e.g., 12 hours to 24 hours) to start the hydrothermal reaction. Under the conditions of high temperature and high pressure, the ions in the precursor solution undergo hydrolysis, polycondensation and other reactions to gradually form Er-doped BiOBr crystals.

[0018] S400, centrifugal washing and ultrasonic disruption:

[0019] S401: After the reaction is completed, the reactor is cooled naturally to room temperature, the reaction product is taken out, the solid product is separated by centrifugation, and washed with deionized water and ethanol for multiple times to remove the residual surfactant and unreacted precursor;

[0020] S402: taking an appropriate amount of Er-doped BiOBr (referred to as x% Er-dropped-BiOBr) after centrifugal washing, and dispersing it in an appropriate amount of polyvinyl pyrrolidone solution;

[0021] S403: using an ultrasonic processor to perform ultrasonic crushing on the dispersion, setting the ultrasonic time to 30 minutes and the power to 100 W to further refine the particles and improve their dispersibility;

[0022] S404: After the ultrasonic treatment, the suspension is centrifuged, and the supernatant is centrifuged and washed again to obtain purer and more dispersed Er-doped BiOBr nanoparticles, which are recorded as x% Er-dropped-BiOBr-CP-yh, where yh represents the sample after ultrasonic treatment;

[0023] S500, sintering treatment:

[0024] S501: placing the obtained x% Er-dropped-BiOBr-CP-yh in a muffle furnace or a tube furnace, and sintering in air or an inert atmosphere;

[0025] S502: setting the sintering temperature to 300°C to 600°C and the sintering time to 2 hours to 6 hours to ensure that the sample is heat treated under controlled conditions to enhance its crystallinity and stability;

[0026] S503: After the sintering is completed, the sample is cooled naturally to room temperature, taken out and washed with deionized water and ethanol to remove attached impurities, and finally the target product Er-doped BiOBr is obtained.

[0027] Furthermore, the Bi precursor is a soluble metal compound Bi(NO3)3·5H2O, the Er precursor is a soluble metal compound Er(NO3)3·6H2O, the surfactant is polyvinyl pyrrolidone, and the Br precursor is a soluble bromide salt, including potassium bromide and 1-butyl-3-methylimidazolium bromide.

[0028] Furthermore, the molar ratio of the Bi precursor to the Br precursor is 1:1 to 1:1.2, the molar ratio of the Bi precursor to the Er precursor is 1:0.05 to 1:0.105, the ratio of the Bi precursor to polyvinyl pyrrolidone is 1mmol:400mg, the ratio of the Bi precursor to deionized water is 1mmol:25ml, and the ratio of the Br precursor to deionized water is 1mmol:5ml.

[0029] Furthermore, the Bi precursor, Er precursor and polyvinyl pyrrolidone are stirred in deionized water for 30 min-60 min to achieve uniform dispersion.

[0030] Furthermore, after the Br precursor is added, the mixture is stirred for 10 min to 30 min, and then the solution is transferred to a polytetrafluoroethylene liner and placed in a stainless steel housing.

[0031] Furthermore, the precursor and the mixed solution were transferred to a polytetrafluoroethylene liner, and then covered with a stainless steel shell. They were heated in a forced air oven at 140°C for 6 h, cooled to room temperature, and then taken out. The resulting solution was centrifuged, washed several times with deionized water and ethanol, and dried at 60°C-100°C for 12h-24h to obtain x% Er-dropped-BiOBr.

[0032] Furthermore, the obtained x% Er-dropped-BiOBr is dispersed in N-methylpyrrolidone at a concentration of 0.6 g / 30 ml, crushed in an ultrasonic crusher for 3-24 hours, and after standing for 0.5h-1h, the supernatant is centrifuged to obtain solid x% Er-dropped-BiOBr-CP-yh.

[0033] Furthermore, the solid x% Er-dropped-BiOBr-CP is maintained at 200°C-600°C in air or nitrogen atmosphere for 2h-6h to obtain the product x% Er-dropped-BiOBr-CP-yh-N2 / Air.

[0034] Compared with the prior art, the method for preparing Er-doped BiOBr for electrocatalytic reduction of oxygen has the following beneficial effects:

[0035] 1. The present invention successfully synthesized Er-doped BiOBr materials with high catalytic activity by precisely controlling the Er doping ratio and the reaction conditions of the precursor. The introduction of the Er element effectively adjusted the energy band structure and electronic arrangement of BiOBr, promoted the transfer and separation of charges, and thus significantly improved the efficiency of the material in the electrocatalytic reduction of oxygen reaction. This efficient electrocatalytic performance makes Er-doped BiOBr have broad application prospects in clean energy fields such as fuel cells and hydrogen production by electrolysis of water.

[0036] 2. The present invention achieves fine control of product morphology and dispersibility by adding an appropriate amount of surfactant (such as polyvinyl pyrrolidone) and controlling its stirring time. The presence of the surfactant helps to reduce the agglomeration between particles and form Er-doped BiOBr nanoparticles with uniform dispersion and regular morphology. This optimized morphology and dispersibility not only increases the specific surface area of ​​the material and increases the catalytic active sites, but also helps to improve the stability and reusability of the catalyst, which is of great significance for practical industrial applications.

[0037] 3. The sintering step in the preparation process of the present invention is the key to improving the crystallinity and stability of the Er-doped BiOBr material. By performing heat treatment at high temperature (300°C to 600°C), the atoms inside the material are rearranged and the lattice is improved to form a highly crystalline crystal structure. At the same time, the sintering process also helps to remove residual surfactants and unreacted precursors and further purify the product. This high-crystallinity, high-purity Er-doped BiOBr material has better chemical stability and thermal stability, can maintain stable catalytic performance in harsh working environments, and extend the service life of the catalyst.

[0038] Other advantages, objectives and features of the present invention will be set forth in part in the following description and, in part, will be apparent to those skilled in the art based on an examination of the following or may be taught from the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 The X-ray diffraction pattern (XRD) of 5% Er-dropped-BiOBr prepared by the method of the present invention;

[0041] Figure 2 Scanning electron microscope image (SEM) of 5% Er-dropped-BiOBr-CP-3h-N2 prepared by the method of the present invention;

[0042] Figure 3 The selectivity diagram of the electrocatalytic reduction of oxygen to generate H2O2 by Er-doped BiOBr prepared by the method of the present invention;

[0043] Figure 4 The current density diagram of the disk-ring electrode for electrocatalytic reduction of oxygen to generate H2O2 prepared by the method of the present invention is shown;

[0044] Figure 5 The element mass ratio of 5% Er-dropped-BiOBr prepared by the method of the present invention. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] Example 1: Preparation of 5% Er-dropped-BiOBr

[0047] Step 1, prepare raw materials: Bi(NO3)3·5H2O: 0.97g, Er(NO3)3: 0.0481g, which is a doping source for erbium (Er) element, polyvinylpyrrolidone (PVP): 0.97g, as a surfactant, which helps to control the morphology and dispersibility of the product, 1-butyl-3-methylimidazolium bromide: 0.458g, dissolved in 10ml of deionized water, as a template or structure directing agent, which helps to form a specific crystal structure;

[0048] Step 2, solution preparation and mixing: Bi(NO3)3·5H2O, Er(NO3)3, PVP and a certain amount of deionized water are mixed and stirred for 30 minutes to ensure that all raw materials are fully dissolved and mixed evenly. Then, 1-butyl-3-methylimidazolium bromide solution (dissolved in 10 ml of deionized water) is slowly added to the above mixed solution and stirred for 10 minutes to allow the template to fully act.

[0049] Step 3, hydrothermal reaction: the mixed solution is transferred to a polytetrafluoroethylene-lined reactor to provide a stable reaction environment under high temperature and pressure. The reactor is placed in a blast oven with a set temperature of 140°C and a reaction time of 6 hours. During this process, a series of chemical reactions occur, including hydrolysis, polycondensation and crystallization, and finally Er-doped BiOBr is formed.

[0050] Step 4, post-treatment: After the reaction is completed, take out the reactor, wait for it to cool naturally to room temperature, open the liner, pour out the reaction liquid, centrifuge the reaction liquid to separate the solid product (Er-doped-BiOBr) and the liquid, and wash the precipitate obtained by centrifugation repeatedly with deionized water and ethanol several times to remove impurities and unreacted substances attached to the surface of the product. Finally, dry the washed product at 65°C for 12 hours to remove residual moisture and solvent to obtain the final 5% Er-dropped-BiOBr product.

[0051] Example 2: Preparation of 5% Er-dropped-BiOBr-CP-xh

[0052] Step 1, dispersion treatment: Take 0.6 g of 5% Er-dropped-BiOBr powder and add the powder into 30 ml of N-methylpyrrolidone (NMP). NMP is a good solvent that can effectively disperse and stabilize nanoparticles.

[0053] Step 2, ultrasonic crushing: place the NMP dispersion containing 5% Er-dropped-BiOBr in an ultrasonic crusher, set the power of the ultrasonic crusher to 50%, and start the ultrasonic crushing program. Note that the power and ultrasonic time here need to be adjusted according to the specific equipment model and sample characteristics. Ultrasonic crushing is performed for 3 hours to further refine the particle size and improve its dispersibility. During the ultrasonic process, the state of the solution should be checked regularly to avoid overheating or excessive foaming;

[0054] Step 3, standing and centrifugation: After the ultrasonic crushing is completed, the dispersion is allowed to stand for 0.5 hours to allow large particles to settle, while small particles and dissolved substances remain in the supernatant. Subsequently, the dispersion after standing is centrifuged using a centrifuge. The centrifugation speed and time should be adjusted according to the actual situation to separate the solid particles and the liquid;

[0055] Step 4, washing and drying: The precipitate obtained by centrifugation (i.e., 5% Er-dropped-BiOBr nanoparticles) was repeatedly washed with deionized water and ethanol for several times to remove NMP and other impurities attached to the surface of the particles. After washing, the precipitate was placed in a drying oven and dried at 65° C. for 12 hours to remove residual water and solvent;

[0056] Step 5, grinding and collection: After drying, the product is taken out and ground to further refine the particle size and improve its uniformity. Finally, the ground product is collected to obtain 5% Er-dropped-BiOBr-CP-3h product.

[0057] Example 3: Preparation of 5% Er-dropped-BiOBr-CP-3h-N2

[0058] Take 0.3 g of 5% Er-dropped-BiOBr-CP-3h, keep it at 400°C for 2 h in a nitrogen atmosphere with a heating rate of 5°C / min to obtain 5% Er-dropped-BiOBr-CP-3h-N2.

[0059] Example 4: Preparation of 5% Er-dropped-BiOBr-CP-3h-Air

[0060] Take 0.3 g of 5% Er-dropped-BiOBr-CP-3h, keep it at 400°C for 2 h in an air atmosphere with a heating rate of 5°C / min to obtain 5% Er-dropped-BiOBr-CP-3h-Air.

[0061] The product prepared in Application Example 1 was subjected to X-ray diffraction, and its spectrum was consistent with the standard card JCPDS: 73-2601. The prepared product was BiOBr crystal, such as Figure 1 As shown;

[0062] The product prepared in Application Example 3 was photographed using a scanning electron microscope. Figure 2 As shown;

[0063] The prepared BiOBr and XC-72R were mixed in a mass ratio of 3:2, dispersed in a mixed solution of isopropanol, water, and Nafion at 5 mg / ml, and ultrasonicated in a cell ultrasonic crusher at 20% power for 10 minutes to obtain a uniformly mixed ink. An appropriate amount was dropped on a glassy carbon electrode and used as a working electrode after natural drying. The test system was a three-electrode system, with an Ag / AgCl electrode as a reference electrode, a platinum mesh as a counter electrode, and a glassy carbon electrode as a working electrode. The test environment was an oxygen-saturated 0.1M KOH solution, the potential scanning range was 1.0-0V relative to a reversible hydrogen electrode, the potential scanning speed was 5mV / s, and the rotation speed of the rotating disk was 1600rpm. The test results are shown in FIG. Figure 3 , Figure 4 shown.

[0064] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for preparing Er-doped BiOBr for electrocatalytic reduction of oxygen, characterized in that: The preparation method comprises: S100, prepare precursor solution: S101: Accurately weigh appropriate amounts of bismuth (Bi) precursor and erbium (Er) precursor, calculate the required mass according to the target doping ratio (x%), mix the two in an appropriate amount of deionized water, and ensure that the precursors are completely dissolved and evenly dispersed by magnetic stirring or ultrasonic treatment; S102: Select a suitable surfactant, add it to the mixed solution in a certain proportion, and continue stirring until the surfactant is completely dissolved to form a uniform solution system. The role of the surfactant is to regulate the morphology and dispersibility of the product; S200, add bromine (Br) precursor and mix: S201: preparing a bromine (Br) precursor solution of a certain concentration to ensure that the amount of bromide ions is sufficient to completely react with bismuth ions to form BiOBr; S202: under continuous stirring, slowly drop the bromine precursor solution into the mixed solution containing Bi and Er precursors, and pay attention to controlling the dropping speed during the dropping process to avoid excessive local concentration; S203: Continue stirring the mixed solution for a period of time to ensure that all ions are fully mixed and uniformly formed to form a uniform precursor solution of Bi, Er and Br; S300, hydrothermal reaction: S301: transferring the mixed solution to a polytetrafluoroethylene-lined reactor, sealing it and placing it in a hydrothermal reaction box; S302: setting the reaction temperature to 120° C. to 180° C. and the reaction time to 12 hours to 24 hours, starting the hydrothermal reaction, where the ions in the precursor solution undergo hydrolysis, polycondensation and other reactions under high temperature and high pressure conditions, gradually forming Er-doped BiOBr crystals; S400, centrifugal washing and ultrasonic disruption: S401: After the reaction is completed, the reactor is cooled naturally to room temperature, the reaction product is taken out, the solid product is separated by centrifugation, and washed with deionized water and ethanol for multiple times to remove the residual surfactant and unreacted precursor; S402: taking an appropriate amount of Er-doped BiOBr (referred to as x% Er-dropped-BiOBr) after centrifugal washing, and dispersing it in an appropriate amount of polyvinyl pyrrolidone solution; S403: using an ultrasonic processor to perform ultrasonic crushing on the dispersion, setting the ultrasonic time to 30 minutes and the power to 100 W to further refine the particles and improve their dispersibility; S404: After the ultrasonic treatment, the suspension is centrifuged, and the supernatant is centrifuged and washed again to obtain purer and more dispersed Er-doped BiOBr nanoparticles, which are recorded as x% Er-dropped-BiOBr-CP-yh, where yh represents the sample after ultrasonic treatment; S500, sintering treatment: S501: placing the obtained x% Er-dropped-BiOBr-CP-yh in a muffle furnace or a tube furnace, and sintering in air or an inert atmosphere; S502: setting the sintering temperature to 300°C to 600°C and the sintering time to 2 hours to 6 hours to ensure that the sample is heat treated under controlled conditions to enhance its crystallinity and stability; S503: After the sintering is completed, the sample is cooled naturally to room temperature, taken out and washed with deionized water and ethanol to remove attached impurities, and finally the target product Er-doped BiOBr is obtained.

2. The method for preparing Er-doped BiOBr for electrocatalytic reduction of oxygen according to claim 1, characterized in that: The Bi precursor is a soluble metal compound Bi(NO3)3·5H2O, the Er precursor is a soluble metal compound Er(NO3)3·6H2O, the surfactant is polyvinyl pyrrolidone, and the Br precursor is a soluble bromide salt, including potassium bromide and 1-butyl-3-methylimidazolium bromide.

3. The method for preparing Er-doped BiOBr for electrocatalytic reduction of oxygen according to claim 1, characterized in that: The molar ratio of the Bi precursor to the Br precursor is 1:1 to 1:1.2, the molar ratio of the Bi precursor to the Er precursor is 1:0.05 to 1:0.105, the ratio of the Bi precursor to polyvinyl pyrrolidone is 1mmol:400mg, the ratio of the Bi precursor to deionized water is 1mmol:25ml, and the ratio of the Br precursor to deionized water is 1mmol:5ml.

4. The method for preparing Er-doped BiOBr for electrocatalytic reduction of oxygen according to claim 1, characterized in that: The Bi precursor, Er precursor and polyvinyl pyrrolidone are stirred in deionized water for 30 min-60 min to achieve uniform dispersion.

5. The method for preparing Er-doped BiOBr for electrocatalytic reduction of oxygen according to claim 1, characterized in that: After the Br precursor is added, the mixture is stirred for 10 min to 30 min, and then the solution is transferred to a polytetrafluoroethylene liner and placed in a stainless steel housing.

6. The method for preparing Er-doped BiOBr for electrocatalytic reduction of oxygen according to claim 1, characterized in that: The precursor and the mixed solution were transferred to a polytetrafluoroethylene liner, and then covered with a stainless steel shell. The mixture was heated at 140° C. for 6 h in a forced air oven, cooled to room temperature, and then taken out. The obtained solution was centrifuged, washed with deionized water and ethanol for several times, and dried at 60° C.-100° C. for 12 h-24 h to obtain x% Er-dropped-BiOBr.

7. The method for preparing Er-doped BiOBr for electrocatalytic reduction of oxygen according to claim 1, characterized in that: The obtained x% Er-dropped-BiOBr was dispersed in N-methylpyrrolidone at a concentration of 0.6 g / 30 ml, crushed in an ultrasonic crusher for 3-24 h, allowed to stand for 0.5 h-1 h, and the supernatant was centrifuged to obtain solid x% Er-dropped-BiOBr-CP-yh.

8. The method for preparing Er-doped BiOBr for electrocatalytic reduction of oxygen according to claim 1, characterized in that: The solid x% Er-dropped-BiOBr-CP is kept at 200°C-600°C in air or nitrogen atmosphere for 2h-6h to obtain the product x% Er-dropped-BiOBr-CP-yh-N2 / Air.

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