Preparation method and application of flower-shaped ZnSe / ZnO heterojunction electrocatalyst
The ZnSe/ZnO heterojunction electrocatalyst addresses the inefficiencies of existing H2O2 synthesis methods by enhancing catalytic activity and stability, achieving high selectivity and yield through a novel two-electron oxygen reduction process.
Patent Information
- Application Number
- CN202411436326.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-15
- Publication Date
- 2025-01-03
AI Technical Summary
Current methods for synthesizing hydrogen peroxide (H2O2) face challenges such as high energy consumption, hazardous materials, and low selectivity and efficiency due to the four-electron oxygen reduction reaction, while existing catalysts like noble metals are costly and unstable, and ZnO-based catalysts lack attention in two-electron oxygen reduction processes.
A flower-shaped ZnSe/ZnO heterojunction electrocatalyst is prepared through a method involving thermal reactions and calcination, forming a heterojunction with enhanced catalytic active sites and stability, enabling efficient two-electron oxygen reduction to H2O2 synthesis.
The ZnSe/ZnO heterojunction achieves high selectivity and yield of H2O2 with low voltage requirements, providing a sustainable and efficient synthesis route with yields up to 754.4 mol L-1 g-1 cat-1 and stable performance over 12 hours.
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Figure CN119243242A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of high value-added chemicals and catalyst production, and specifically relates to a preparation method and application of a flower-shaped ZnSe / ZnO heterojunction electrocatalyst. Background Art
[0002] Hydrogen peroxide (H2O2) is one of the important chemical raw materials and has broad application prospects in the fields of chemical industry, medicine, environmental protection, fuel cells, etc. The current industrial synthesis of H2O2 is highly dependent on the anthraquinone method, which is a multi-step and energy-intensive reaction with harmful waste by-products. The direct preparation of H2O2 using hydrogen and oxygen is a feasible approach, but the hydrogen / oxygen mixture has explosion hazards and is easily diluted by inert gases, resulting in reduced product selectivity and yield. The electrocatalytic oxygen reduction reaction can directly use electrical energy to input air (the source of O2) and water to efficiently and selectively synthesize H2O2 at room temperature. It is a promising emerging preparation process that can replace the traditional high-energy anthraquinone method. However, its competitive four-electron oxygen reduction reaction greatly limits the selectivity and efficiency of H2O2 synthesis. Therefore, the development of economical, efficient, highly selective, and highly stable electrocatalytic materials to catalyze the synthesis of H2O2 is the key to solving the above problems.
[0003] At present, the reported catalysts with excellent two-electron oxygen reduction activity and selectivity mainly include noble metal-based catalysts, carbon materials and transition metal-based compounds. However, the characteristics of noble metal catalysts, such as their rarity, high price and strong catalytic effect on the self-decomposition of H2O2, limit their development in practical large-scale applications. In addition, the activity of most reported carbon nanomaterials in catalyzing the synthesis of H2O2 is lower than that of noble metal-based catalysts, and the electrocatalytic mechanism and active sites are still unclear, which greatly limits the development of high-performance electrocatalysts for preparing H2O2. Transition metal oxides are regarded as one of the two-electron oxygen reduction electrocatalysts with great application potential due to their low cost, abundant reserves and weak oxygen adsorption on the surface. From the perspective of environmental and biocompatibility, ZnO is an ideal green electrocatalyst. Although ZnO has been considered as a potential catalyst for the generation of H2O2 by light- or electricity-driven two-electron water oxidation reaction, the research on the generation of H2O2 in its two-electron oxygen reduction process has not received widespread attention. Summary of the invention
[0004] One of the purposes of the present invention is to provide a ZnSe / ZnO heterojunction electrocatalyst and a preparation method thereof.
[0005] The second object of the present invention is to provide a method for electrocatalytically synthesizing H2O2 using a ZnSe / ZnO heterojunction electrocatalyst.
[0006] The technical solution adopted by the present invention is:
[0007] A method for preparing a flower-shaped ZnSe / ZnO heterojunction electrocatalyst comprises the following steps:
[0008] 1) Dissolve Zn(NO3)2·6H2O and CO(NH2)2 in water, stir until completely dissolved, transfer the mixed solution to a Teflon-lined autoclave for thermal reaction, cool to room temperature, wash with water and ethanol several times, and dry in a vacuum drying oven at 60°C; then place the obtained solid in a quartz boat, transfer to a muffle furnace for calcination, and obtain ZnO after natural cooling;
[0009] 2) NaBH4 and Se powder were dispersed in an ethanol-water solution, ZnO was added and stirring was continued for 30 min, the mixture was transferred to a Teflon-based high-pressure reactor for thermal reaction, cooled to room temperature, washed with water and ethanol, and dried in a constant temperature drying oven at 60°C to obtain a ZnSe / ZnO heterojunction electrocatalyst.
[0010] Furthermore, in the above preparation method, in step 1), 0.297 g Zn(NO3)2·6H2O and 6 g CO(NH2)2 were dissolved in 80 mL water.
[0011] Furthermore, in the above preparation method, in step 1), the thermal reaction conditions in the high-pressure reactor are: 100° C. for 8 hours.
[0012] Furthermore, in the above preparation method, in step 1), the calcination conditions in the muffle furnace are: 500° C. for 6 hours.
[0013] Furthermore, in the above preparation method, in step 2), 0.02 g NaBH4 and 0.015 g Se powder are dispersed in 50 mL of 50% by volume ethanol aqueous solution, and then 0.8 g ZnO is added.
[0014] Furthermore, in the above preparation method, in step 2), the thermal reaction conditions in the high-pressure reactor are: 200° C. for 15 hours.
[0015] A method for preparing a ZnSe / ZnO / CF hydrophobic electrode using a ZnSe / ZnO heterojunction electrocatalyst prepared by any of the preparation methods described above, characterized in that the method is as follows: weigh 1 mg of ZnSe / ZnO heterojunction electrocatalyst and disperse it in 500 μL of water containing 5 μL of 5% Nafion solution, and ultrasonically disperse it to form a uniform dispersion; drop the dispersion onto the pretreated CF and dry it at room temperature to obtain a hydrophilic ZnSe / ZnO / CF working electrode; then spray the back of the CF with a polytetrafluoroethylene solution of 6% by mass 30 times and place it in a quartz porcelain boat, and incubate it at 5°C min under a nitrogen atmosphere. -1The temperature was raised to 350°C at a heating rate and maintained for 30 min to finally obtain a ZnSe / ZnO / CF hydrophobic electrode.
[0016] The application of the ZnSe / ZnO / CF hydrophobic electrode prepared by the above method in the electrocatalytic synthesis of H2O2.
[0017] Furthermore, the above application method is as follows: a standard three-electrode system is used in an H-type reactor with a proton exchange membrane as a diaphragm, with a ZnSe / ZnO / CF hydrophobic electrode as a working electrode, Ag / AgCl as a reference electrode, a Pt sheet as a counter electrode, and an electrolytic cell solution of an O2-saturated 0.1M KOH solution, and O2 is continuously introduced during the reaction.
[0018] Furthermore, the above application method is as follows: a standard three-electrode system is used in a flow cell reactor with a proton exchange membrane as a diaphragm, with a ZnSe / ZnO / CF hydrophobic electrode as a working electrode, Ag / AgCl as a reference electrode, a Pt sheet as a counter electrode, and an electrolytic cell solution of an O2-saturated 0.1M KOH solution, and O2 is continuously introduced during the reaction.
[0019] The beneficial effects of the present invention are:
[0020] 1. The present invention constructs a ZnSe / ZnO heterojunction electrocatalyst by in-situ selenization of three-dimensional flower-shaped ZnO, and induces dipole polarization through defect engineering and coordinated element doping to form localized electronic states and better catalytic active sites, promote mass / charge transfer, and make it have unique electronic properties and strong stability. Using the method of the present invention, under the action of a specific additional bias, the yield of H2O2 produced by catalysis within 12 hours is as high as 754.4 mol L -1 g cat -1 , providing a green synthesis route and sustainable technology for the production of H2O2.
[0021] 2. The present invention is simple, efficient, low-cost, highly selective, and requires low voltage for electrocatalysis. The prepared ZnSe / ZnO heterojunction electrocatalyst has excellent electrocatalytic two-electron oxygen reduction activity and H2O2 selectivity, faster electrochemical reaction kinetics, and more exposed active sites. The potential required for synthesizing H2O2 is low, and it has good stability and cyclic availability, and can be applied to related fields such as electrocatalytic preparation of H2O2 and degradation of organic matter. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 are scanning electron microscope (SEM) images of ZnO (a) and ZnSe / ZnO (b).
[0023] Figure 2It is the X-ray diffraction (XRD) spectra of ZnO, ZnSe and ZnSe / ZnO.
[0024] Figure 3 The rotating ring disk electrode (RRDE) curves of ZnO, ZnSe and ZnSe / ZnO (a) and the selectivity and electron transfer number curves (b).
[0025] Figure 4 The graphs are the H2O2 yield curves of electrocatalytic synthesis of ZnO, ZnSe and ZnSe / ZnO at 0.2V (a) and the corresponding ring and disk currents and H2O2 selectivity curves (b).
[0026] Figure 5 This is a graph showing the change in H2O2 production and current over time in the electrocatalytic synthesis of H2O2 by ZnSe / ZnO in a flow cell system (the electrolyte solution is replaced every 12 hours). DETAILED DESCRIPTION
[0027] Example 1 Preparation of flower-shaped ZnSe / ZnO heterojunction electrocatalyst
[0028] (I) Preparation of ZnO
[0029] Weigh 0.297g Zn(NO3)2·6H2O and 6g CO(NH2)2 and dissolve them in 80mL water, stir until completely dissolved, transfer the mixed solution to a 100mL Teflon-lined autoclave, react at 100℃ for 8h, cool to room temperature, wash with water and ethanol several times, and dry in a vacuum oven at 60℃. Then place the obtained solid in a quartz boat, transfer to a muffle furnace, heat to 500℃ in an air atmosphere and keep for 6h, and obtain ZnO after natural cooling.
[0030] (II) Preparation of ZnSe / ZnO
[0031] 0.02 g NaBH4 and 0.015 g Se powder were weighed and dispersed in 50 mL ethanol aqueous solution (the volume ratio of ethanol to water was 1:1), and then 0.8 g ZnO precursor was added and stirred for 30 min. The mixed solution was transferred to a 100 mL Teflon-lined high-pressure reactor and reacted at 200 °C for 15 h. After cooling to room temperature, it was washed with water and ethanol several times and dried at 60 °C in a constant temperature drying oven to obtain a ZnSe / ZnO heterojunction electrocatalyst.
[0032] like Figure 1 The SEM images of ZnO (a) and ZnSe / ZnO (b) are shown in Figure 2. Figure 1 As can be seen in a, ZnO is a three-dimensional flower-like structure formed by the self-assembly of a large number of nanoparticles, with a size of about 3-10μm; after partial selenization, Figure 1The ZnSe / ZnO heterojunction shown in b maintains the original three-dimensional flower-like structure. Compared with the substrate ZnO, its structure is denser, which is beneficial to improving the catalytic active sites.
[0033] like Figure 2 The XRD spectra of ZnO, ZnSe and ZnSe / ZnO are shown in Figure 2. Figure 2 It can be seen that the crystal structure of ZnO corresponds to hexagonal wurtzite (JCPDS NO.36-1451). After partial selenization, its XRD spectrum maintains the original crystal structure of ZnO, and at the same time adds diffraction peaks corresponding to the (111), (220) and (311) crystal planes of ZnSe (JCPDS NO.37-1463), confirming the successful synthesis of the ZnSe / ZnO heterojunction.
[0034] Example 2 Electrocatalytic selectivity test
[0035] Weigh 2 mg of ZnSe / ZnO heterojunction electrocatalyst and add it to 800 μL of ethanol / water mixed solution (v / v, 15 / 1) containing 2% Nafion, and ultrasonically disperse to obtain a uniform dispersion. Use a pipette to take 8 μL of the dispersion droplet and apply it to the surface of the rotating disk electrode (RRDE) (ring electrode area: 0.1866 cm 2 , disk electrode area: 0.2475cm 2 ), and then naturally dried to form a uniform film to obtain ZnSe / ZnO modified RRDE.
[0036] The selectivity test was performed using a CHI760E electrochemical workstation in a standard three-electrode system. The ZnSe / ZnO-modified RRDE was used as the working electrode, the Ag / AgCl electrode was used as the reference electrode, the Pt sheet was used as the counter electrode, and the electrolyte solution was an O2-saturated 0.1 M KOH solution, and O2 was continuously introduced during the reaction. The scanning potential range of the linear sweep voltammetry (LSV) curve was 0-1.0 V vs. RHE, the ring electrode potential was 1.2 V vs. RHE, and the scanning rate was 5 mV s -1 The rotation speed was 1600 rpm. The working potential (vs. SCE) was converted to the potential relative to the standard hydrogen electrode (vs. RHE) according to formula (1).
[0037] E RHE = E SCE + 0.0592pH + 0.1976 (1)
[0038] The calculation formula of H2O2 selectivity and the number of transferred electrons is as follows:
[0039]
[0040] Among them, I ring is the ring electrode current density, I disk is the disk electrode current density, N is the collection efficiency which is 0.37.
[0041] Depend on Figure 3 It can be seen that ZnSe / ZnO has the largest disk current density and ring current density, indicating that it has strong oxygen reduction reaction (ORR) activity and two-electron selectivity. The selectivity (%) and electron transfer number (n) calculated according to formulas (2) and (3) show that the two-electron ORR selectivity of ZnSe / ZnO in the potential range of 0.1-0.4V vs.RHE remains above 80%, and the number of transferred electrons is about 2.2, which is more conducive to the synthesis of H2O2 through two-electron ORR.
[0042] Example 3 Electrocatalytic production of H2O2
[0043] Preparation of ZnSe / ZnO / carbon felt (CF) hydrophobic electrode:
[0044] 1 mg of ZnSe / ZnO heterojunction electrocatalyst was dispersed in 500 μL of water containing 5 μL of 5% Nafion solution, and ultrasonic dispersion was performed to form a uniform dispersion. The dispersion was drop-coated on the pretreated CF (2 cm × 2 cm × 0.2 cm) and dried at room temperature to obtain a hydrophilic ZnSe / ZnO / CF working electrode. The back of the electrode was then sprayed with a 6% polytetrafluoroethylene solution (30 times) and placed in a quartz boat. The electrode was heated at 5 °C min under a nitrogen atmosphere. -1 The temperature was raised to 350°C at a heating rate and maintained for 30 min to finally obtain a ZnSe / ZnO / CF hydrophobic electrode.
[0045] (I) Performance of ZnSe / ZnO / CF electrocatalytic synthesis of H2O2 in static system
[0046] A standard three-electrode system was used in an H-type reactor with a proton exchange membrane as a diaphragm, with a ZnSe / ZnO / CF hydrophobic electrode as the working electrode, Ag / AgCl as the reference electrode, a Pt sheet as the counter electrode, and a 20 mL O2-saturated 0.1 M KOH solution in the electrolytic cell, and O2 was continuously introduced during the reaction. During the electrically driven catalytic reaction, 0.5 mL of the solution was taken out every 30 min, and the H2O2 production was detected by potassium titanium oxalate colorimetry.
[0047] The results of ORR synthesis of H2O2 using electrodes with different hydrophobicity are as follows: Figure 4As shown in the figure. Under a given bias voltage of 0.2 V, the H2O2 production first increased and then slightly decreased with time, maintaining a stable current response and selectivity. After 3.5 h of catalytic reaction, the maximum value reached was 41.1 mol L -1 g cat -1 The H2O2 yields of ZnO / CF and ZnSe / CF were 25.1 and 18.7 mol L-1 higher than those of ZnO / CF and ZnSe / CF, respectively. -1 g cat -1 .
[0048] (II) Performance of ZnSe / ZnO / CF electrocatalytic synthesis of H2O2 in a flow cell system
[0049] A standard three-electrode system was used in a flow cell reactor with a proton exchange membrane as a diaphragm, with a ZnSe / ZnO / CF hydrophobic electrode as the working electrode, Ag / AgCl as the reference electrode, a Pt sheet as the counter electrode, and a 20 mL O2-saturated 0.1 M KOH solution in the electrolytic cell, and O2 was continuously introduced during the reaction. During the electrically driven catalytic reaction, 0.5 mL of the solution was taken out every 30 min, and the H2O2 production was detected by potassium titanium oxalate colorimetry.
[0050] The results are as follows Figure 5 As shown in the figure, the H2O2 production increased with time, and the production reached 754.4 mol L after 12 h of catalytic reaction. -1 g cat -1 , while maintaining a stable current response. The electrolytic solution was replaced every 12 hours, and its output and current response still maintained good reproducibility.
Claims
1. A method for preparing a flower-shaped ZnSe / ZnO heterojunction electrocatalyst, characterized in that: The steps include: 1) Dissolve Zn(NO3)2·6H2O and CO(NH2)2 in water, stir until completely dissolved, transfer the mixed solution to a Teflon-lined autoclave for thermal reaction, cool to room temperature, wash with water and ethanol several times, and dry in a vacuum drying oven at 60°C; then place the obtained solid in a quartz boat, transfer to a muffle furnace for calcination, and obtain ZnO after natural cooling; 2) NaBH4 and Se powder were dispersed in an ethanol-water solution, ZnO was added and stirring was continued for 30 min, the mixture was transferred to a Teflon-based high-pressure reactor for thermal reaction, cooled to room temperature, washed with water and ethanol, and dried in a constant temperature drying oven at 60°C to obtain a ZnSe / ZnO heterojunction electrocatalyst.
2. The preparation method according to claim 1, characterized in that: In step 1), 0.297 g Zn(NO3)2·6H2O and 6 g CO(NH2)2 were dissolved in 80 mL water.
3. The preparation method according to claim 1, characterized in that: In step 1), the thermal reaction conditions in the high-pressure reactor are: 100° C. for 8 h.
4. The preparation method according to claim 1, characterized in that: In step 1), the calcination condition in the muffle furnace is: 500° C. for 6 hours.
5. The preparation method according to claim 1, characterized in that: In step 2), 0.02 g NaBH4 and 0.015 g Se powder were dispersed in 50 mL of 50% by volume ethanol aqueous solution, and then 0.8 g ZnO was added.
6. The preparation method according to claim 1, characterized in that: In step 2), the thermal reaction conditions in the high-pressure reactor are: 200° C. for 15 h.
7. A method for preparing a ZnSe / ZnO / CF hydrophobic electrode using a ZnSe / ZnO heterojunction electrocatalyst prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The method is as follows: 1 mg of ZnSe / ZnO heterojunction electrocatalyst is weighed and dispersed in 500 μL of water containing 5 μL of 5% Nafion solution, and ultrasonically dispersed to form a uniform dispersion; the dispersion is drop-coated on the pretreated CF and dried at room temperature to obtain a hydrophilic ZnSe / ZnO / CF working electrode; the back of the CF is then sprayed with a 6% polytetrafluoroethylene solution by mass 30 times and placed in a quartz boat, and heated at 5°C min under a nitrogen atmosphere. -1 The temperature was raised to 350°C at a heating rate and maintained for 30 min to finally obtain a ZnSe / ZnO / CF hydrophobic electrode.
8. Use of the ZnSe / ZnO / CF hydrophobic electrode prepared by the method according to claim 7 in electrocatalytic synthesis of H2O2.
9. The use according to claim 8, characterized in that: The method is as follows: a standard three-electrode system is used in an H-type reactor with a proton exchange membrane as a diaphragm, with a ZnSe / ZnO / CF hydrophobic electrode as the working electrode, Ag / AgCl as the reference electrode, a Pt sheet as the counter electrode, and an O2-saturated 0.1M KOH solution in the electrolytic cell, and O2 is continuously introduced during the reaction.
10. The use according to claim 8, characterized in that: The method is as follows: a standard three-electrode system is used in a flow cell reactor with a proton exchange membrane as a diaphragm, with a ZnSe / ZnO / CF hydrophobic electrode as the working electrode, Ag / AgCl as the reference electrode, a Pt sheet as the counter electrode, and an O2-saturated 0.1M KOH solution in the electrolytic cell, and O2 is continuously introduced during the reaction.