Preparation method and application of Se defect induced Zn1-Co / CoSe2-x catalyst

Abstract

The invention relates to a preparation method and application of a Se defect induced Zn1-Co / CoSe2-x catalyst. The preparation method comprises the following steps: firstly, preparing Se-defective orthorhombic phase cobalt selenide o-CoSe2-x powder, weighing a certain amount of zinc salt and o-CoSe2-x powder, mixing, adding absolute ethyl alcohol, stirring for 12 hours, standing for 12 hours, drying to obtain Zn-doped CoSe2-x powder, and roasting the Zn-doped CoSe2-x powder in a quartz boat and a tube furnace to obtain the Zn-doped CoSe2-x-doped cobalt selenide. According to the method, Zn monatomic atoms are anchored and formed on defect type CoSe2-x through simple hydrothermal, dipping and roasting methods, and the Zn monatomic atoms and Co form relatively long-distance Zn-Co para-sites, so that an electronic structure of active sites is modulated, the selectivity of a Co-based catalyst to a two-electron oxygen reduction reaction under an acidic condition is improved, and the Co-based catalyst can be applied to the field of catalytic reduction. And the catalyst has high yield and excellent stability, and can solve the problems of high price, low efficiency and the like of a catalyst for producing hydrogen peroxide under an acidic condition at present.

Description

Technical Field

[0001] The present invention relates to the field of electrochemistry technology, and specifically to a preparation method and application of a Se-defect-induced Zn1-Co / CoSe catalyst containing Zn-Co pair sites. 2-x Background Art

[0002] As a green, clean and environmentally friendly oxidant, hydrogen peroxide is widely used in industries such as medical disinfection, wastewater treatment, papermaking and textile, aerospace, metallurgy, and electronics industry. At present, most hydrogen peroxide (>95%) is produced by a process based on industrial anthraquinone, involving a series of cumbersome steps (such as hydrogenation reaction, oxidation, purification, transportation and storage), consuming a large amount of energy. Although this method can produce hydrogen peroxide on a large scale at the industrial level, this preparation process has problems such as high energy consumption, high cost, and transportation hazards, which hinder its practical application. As a method for producing hydrogen peroxide by oxygen reduction, the electrochemical method has the advantages of high efficiency, relatively low energy consumption, and safe operation. The synthesized hydrogen peroxide solution has no impurities and high purity, so it is considered to have good development prospects.

[0003] However, there is currently a lack of an oxygen reduction electrocatalyst that combines high activity and high selectivity and is cheap and easily available. In particular, a high-performance catalyst that can electrocatalytically reduce oxygen to synthesize hydrogen peroxide under acidic conditions is scarce. Fenton's reagent is mainly used in organic synthesis and wastewater treatment, and its most suitable pH range is 2.5–3.5. The currently developed commercial proton exchange membranes are also more suitable for acidic environments. Therefore, the study of electrocatalytic synthesis of H2O2 in acidic media is more meaningful for future large-scale industrial applications.

[0004] Currently, the research on cobalt-based and transition metal selenides has been widely applied to the two-electron oxygen reduction reaction (2e - ORR). However, the active centers regulated by single metal sites are difficult to balance the activity and selectivity of the catalyst, and it is difficult to meet commercial applications. At present, a large number of studies have proved that the strong affinity of cobalt metal particles for *O contributes to the adsorption and activation of O2 molecules (O2 + 2H + + 2e - → *OOH), and cobalt-based catalysts are also considered to be 2e - ​The high metal activity of transition metal selenides is a good catalyst for ORR. However, its high metal activity makes the adsorption force of active intermediate *OOH too strong, which easily causes the breakage of O-OH, thereby reducing the selectivity for H2O2. The physicochemical properties of transition metal selenides are stable and not easily corroded under acidic conditions. At the same time, the larger atomic radius of selenium helps to optimize the adsorption configuration of O2 molecules. A large number of studies have shown that the end-to-end adsorption of active sites and O helps to improve the selectivity. However, the yield of H2O2 reported by transition metal selenides is low and cannot meet the needs of large-scale production and practical applications. In addition, some ORR catalysts that are widely believed to have excellent performance (such as carbon materials and precious metal-based materials) are unstable in acidic media. For example, carbon materials are easily corroded by acids, and precious metal-supported catalysts are prone to metal ion dissolution after a long redox reaction cycle, which limits their potential application in H2O2 production.

[0005] Therefore, a high 2e - Electrocatalytic materials with ORR catalytic performance are urgently needed. Solving the above-mentioned problems in the process of electrocatalytic synthesis of H2O2 is also one of the problems that many forward-looking researchers in this field need to solve urgently. Summary of the invention

[0006] In order to solve the above problems, the present invention aims to provide a Se-deficient induced Zn1-Co / CoSe containing Zn-Co pair sites. 2-x Preparation method and application of catalyst, through simple hydrothermal, impregnation and calcination method, on defective CoSe 2-x The Zn single atom (denoted as Zn1) is anchored and formed on the surface of Co. The Zn single atom forms a long-range Zn-Co pair site with Co. The formation of the pair site effectively improves the selectivity of the catalyst by optimizing the adsorption configuration of the active site to *O without reducing the activity of Co. In addition, the formation of the pair site greatly reduces the energy barrier of the subsequent hydrogenation step, significantly improving the H2O2 yield compared to general transition metal selenide-based materials.

[0007] The present invention is specifically implemented by the following technical scheme: according to a Se defect-induced Zn1-Co / CoSe containing Zn-Co pair sites proposed in the present invention, 2-x The preparation method of the catalyst specifically comprises:

[0008] (1) Weigh a certain amount of selenium powder and add it to a beaker containing NaOH solution, then stir vigorously to obtain a mixed material A; weigh a certain amount of metal cobalt salt and add it to a beaker containing 0.25M EDTA-2Na solution, then stir vigorously to obtain a mixed material B; add the mixed material B to the mixed material A and stir to obtain a mixed material C; transfer the mixed material C to a hydrothermal reaction kettle for hydrothermal reaction, the temperature of the hydrothermal reaction is 200 °C, and the reaction time is 6 h; after the hydrothermal reaction is completed, naturally cool the reaction kettle to room temperature, centrifuge and separate the product in the reaction kettle, collect the precipitate, ultrasonically wash the precipitate with HCl solution 3 times, then centrifuge and separate, and then centrifuge and wash with ultrapure water until neutral, collect the precipitate and place it in a blast drying oven to dry at 60 °C for 12 h to obtain Se-deficient orthorhombic cobalt selenide powder, denoted as o-CoSe 2-x powder;

[0009] (2) Weigh a certain amount of metal zinc salt and a certain amount of o-CoSe 2-x powder obtained in step (1), mix them, then add absolute ethanol thereto, stir for 12 h, let stand for 12 h, and then transfer the mixture into a blast drying oven to dry at 60 °C for 12 h to obtain Zn-doped CoSe 2-x powder;

[0010] (3) Grind the Zn-doped CoSe 2-x powder prepared in step (2) in a mortar, then put it into a quartz boat, and place the quartz boat in a tubular furnace for roasting, the roasting temperature is 350 °C, and the roasting time is 2 h to obtain a Se-defect-induced Zn1-Co / CoSe catalyst containing Zn-Co pair sites 2-x catalyst.

[0011] Further, the metal cobalt salt described in step (1) is one of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, and cobalt acetate tetrahydrate.

[0012] Further, the molar ratio of selenium powder to metal cobalt salt in step (1) is 1.65 - 1.85:1.

[0013] Further, the concentration of the NaOH solution in step (1) is 3.33 mol / L, and the concentration of the HCl solution is 0.1 - 1 mol / L.

[0014] Further, in step (2), a certain amount of metal zinc salt and a certain amount of o-CoSe 2-x powder obtained in step (1) are weighed according to the Zn / Co molar ratio of 0.001 - 0.05:1.

[0015] Preferably, the Zn / Co molar ratio is 0.03:1.

[0016] Furthermore, in the above preparation method, the heating rates of the tubular furnace and the blast drying oven are both 5 °C / min.

[0017] Another object of the present invention is to provide a Se defect-induced Zn1-Co / CoSe containing Zn-Co pair sites prepared by the above method 2-x catalyst and its application in electrocatalytic oxygen reduction to hydrogen peroxide under acidic conditions. The Zn1-Co / CoSe 2-x catalyst has a nanorod morphology, the diameter of the nanorods is 30-50 nm, and its selectivity is as high as 95% when used for electrocatalytic oxygen reduction to hydrogen peroxide in acidic media.

[0018] Furthermore, when the Zn1-Co / CoSe 2-x catalyst is used for electrocatalytic oxygen reduction to hydrogen peroxide, the specific operation includes:

[0019] Take 5 mg of Zn1-Co / CoSe 2-x catalyst and 1 mg of conductive carbon (VXC-72RC), add 875 μL of isopropanol and 125 μL of ultrapure water, then add 10 μL of 5% Nafion solution and ultrasonicate until the catalyst is uniformly dispersed to obtain a catalyst dispersion. Spray 200 μL of the catalyst dispersion on a 2.5 cm × 2.5 cm gas diffusion carbon paper to obtain a working electrode sheet. A graphite rod and a saturated silver chloride electrode are respectively used as the counter electrode and the reference electrode, and electrocatalytic oxygen reduction to hydrogen peroxide is tested in a flow electrolytic cell. The test electrolyte is 0.1 mol / L HClO4 solution.

[0020] The beneficial technical effects of the present invention:

[0021] (1) In the present invention, Zn single atoms (denoted as Zn1) are anchored and formed on defective CoSe 2-x by a simple hydrothermal, impregnation, and calcination method. The Zn single atoms and Co form distant Zn-Co pair sites. The formation of the pair sites effectively improves the selectivity of the catalyst by optimizing the adsorption configuration of *O on the active sites without reducing the activity of Co. The unique Zn-O-O-Co adsorption configuration contributes to the adsorption of *O and the optimization of ΔG *OOH , breaking the trade-off effect between activity and selectivity. In addition, the formation of Zn-Co pair sites can effectively regulate the binding energies of oxygen-containing intermediates (*OH, *O, and *OOH), reduce the Gibbs free energy barrier, accelerate the ORR reaction kinetics, and contribute to the synthesis of H2O2, resulting in a significant increase in the H2O2 yield compared to general transition metal selenide-based materials.

[0022] (2) By constructing single-atom sites on transition metal selenide, the present invention effectively improves the selectivity of Co-based catalysts for the two-electron oxygen reduction reaction. The preparation process is simple, with low cost and easy for industrial application. Experiments show that the Zn1-Co / CoSe catalyst with Se defects inducing Zn-Co pair sites prepared by the present invention 2-x exhibits good electrocatalytic oxygen reduction performance for producing H2O2 in acidic media. At 0.65 V (versus the standard hydrogen electrode), the selectivity of H2O2 is up to 95%, and at 0.25 - 0.65 V (versus the standard hydrogen electrode), the selectivity is greater than 80%. At a large current density of 250 mA cm -2 the hydrogen peroxide yield is 2.26 mol g cat. -1 h -1 , which is much higher than the reported yields of electrocatalytic oxygen reduction to hydrogen peroxide by two-electron oxygen reduction catalysts based on non-precious metal compounds under acidic conditions. Meanwhile, this catalyst can stably electrocatalytically reduce oxygen to produce H2O2 in acidic media at a large current density for more than 30 hours, with high yield and excellent stability, which can solve the problems of high price and low efficiency of current catalysts for producing hydrogen peroxide under acidic conditions. Description of the Drawings

[0023] Figure 1 Figure (a) is the high-resolution transmission electron microscopy image, figure (b) is the transmission electron microscopy image, figure (c) is the selected area electron diffraction pattern, and figure (d) is the selected area intensity distribution pattern of the Zn1-Co / CoSe catalyst prepared in Example 1; 2-x Figure (a) is the high-resolution transmission electron microscopy image, figure (b) is the transmission electron microscopy image, figure (c) is the selected area electron diffraction pattern, and figure (d) is the selected area intensity distribution pattern of the Zn1-Co / CoSe catalyst prepared in Example 1;

[0024] Figure 2 Figure is the XRD pattern of the catalysts prepared in Example 1 and Comparative Examples 1 - 2;

[0025] Figure 3 Figure is the Raman pattern of the catalysts prepared in Example 1 and Comparative Examples 1 - 2;

[0026] Figure 4 Figure is the XPS pattern of the catalysts prepared in Example 1 and Comparative Examples 1 - 2;

[0027] Figure 5 Figure is the EPR pattern of the catalysts prepared in Example 1 and Comparative Examples 1 - 2;

[0028] Figure 6 Figure is the electrochemical impedance test pattern of the catalysts prepared in Example 1 and Comparative Examples 1 - 2;

[0029] Figure 7 Figure is the polarization curve of the catalysts prepared in Example 1 and Comparative Examples 1 - 2 for the two-electron oxygen reduction reaction;

[0030] Figure 8 It is a graph of the selectivity and electron transfer number of the catalysts prepared in Example 1 and Comparative Examples 1-2 for electrocatalytic oxygen reduction to hydrogen peroxide;

[0031] Figure 9 It is a Tafel slope graph of the catalysts prepared in Example 1 and Comparative Examples 1-2;

[0032] Figure 10 It is a double-layer capacitance graph of the catalysts prepared in Example 1 and Comparative Examples 1-2;

[0033] Figure 11 It is the cyclic stability graph of the Zn1-Co / CoSe 2-x catalyst prepared in Example 1;

[0034] Figure 12 It is the yield graph of the Zn1-Co / CoSe 2-x catalyst prepared in Example 1 for electrocatalytic oxygen reduction to hydrogen peroxide;

[0035] Figure 13 It is the degradation graph of hydrogen peroxide obtained by electrocatalytic oxygen reduction of the Zn1-Co / CoSe 2-x catalyst prepared in Example 1 on Rhodamine B, where (a) is the graph of the absorbance of Rhodamine B in the solution changing with the degradation time, and (b) is the change curve of the ratio of the remaining concentration of Rhodamine B to the initial concentration changing with the degradation time.

[0036] Figure 14 It is the Gibbs free energy and density of states graph of the Zn1-Co / CoSe 2-x catalyst prepared in Example 1.

[0037] Among them: The catalyst prepared in Example 1 is denoted as Zn1-Co / CoSe 2-x , the catalyst prepared in Comparative Example 1 is denoted as CoSe2-350, and the catalyst prepared in Comparative Example 2 is denoted as Zn c -Co / CoSe 2-x . Detailed implementation manners

[0038] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0039] In the following examples, those without specific conditions noted are carried out according to conventional conditions or conditions recommended by the manufacturer. For raw materials and reagents without the manufacturer indicated, they are all conventional products that can be obtained by purchasing in the market.

[0040] Example 1:

[0041] (1) Weigh 3.3 mmol of selenium powder and add it to a beaker containing 30 mL of NaOH (4 g, Sinopharm) solution, and stir vigorously for 15 - 30 min to obtain a mixed material A; weigh 2 mmol of cobalt nitrate hexahydrate and add it to a beaker containing 10 mL of 0.25 mol / L EDTA-2Na solution, and stir vigorously for 15 - 30 min to obtain a mixed material B; add the mixed material B to the mixed material A and stir for 15 - 30 min to obtain a mixed material C. Transfer the mixed material C to a hydrothermal reaction kettle for hydrothermal reaction. The temperature of the hydrothermal reaction is 200 °C, and the reaction time is 6 h. After the hydrothermal reaction is completed, cool the reaction kettle naturally to room temperature. Centrifuge the product in the reaction kettle to collect the precipitate. Ultrasonically wash the precipitate with about 40 mL of 0.1 mol / L HCl solution for 2 - 3 min, and then centrifuge. Wash the black precipitate by centrifugation with HCl solution in this way 3 times (40 mL of 0.1 mol / L HCl solution each time), and then wash it by centrifugation with ultrapure water 3 times (washed to neutral). The centrifuge speed is 9000 rmp, and the centrifugation time for each time is 5 min. After that, collect the black precipitate and place it in a blast drying oven to dry at 60 °C for 12 h to obtain Se-deficient orthorhombic cobalt selenide (o-CoSe 2-x ) powder.

[0042] (2) According to the Zn / Co molar ratio of 0.03:1, weigh 0.00446 g (0.015 mmol) of zinc nitrate hexahydrate and 0.0945 g of the o-CoSe 2-x powder prepared in step (1) (the theoretical molecular weight of o-CoSe 2-x is about 189). After mixing the two, add 5 mL of absolute ethanol, stir for 12 h, then let it stand for 12 h. Subsequently, transfer the mixture to a blast drying oven and dry at 60 °C for 12 h to obtain Zn-doped CoSe 2-x powder.

[0043] (3) Grind the Zn-doped CoSe 2-x powder prepared in step (2) in a mortar, then put it into a quartz boat, and place the quartz boat in a tube furnace for roasting. The roasting temperature is 350 °C, and the roasting time is 2 h. Finally, obtain a Se-defect-induced Zn1-Co / CoSe catalyst containing Zn-Co pair sites 2-x .

[0044] Zn1-Co / CoSe2-x Electrochemical performance test process:

[0045] Weigh 5 mg of Zn1-Co / CoSe 2-x and 1 mg of conductive carbon black, add 875 μL of isopropanol and 125 μL of ultrapure water, then add 10 μL of 5% Nafion solution and ultrasonicate until the catalyst is evenly dispersed to obtain a catalyst dispersion. Spray 2.5 μL of the catalyst dispersion on a rotating ring-disk electrode. A graphite rod and a saturated silver chloride electrode are respectively used as the counter electrode and the reference electrode, and are connected to a rotating ring-disk instrument of Chenhua CHI760e electrochemical workstation for testing. The test electrolyte is 0.1 mol / L HClO4 solution. Before the electrochemical test of ORR, the electrolyte is purged with Ar gas for 30 min for CV activation, and then purged with oxygen for 30 min. The polarization curve is obtained at a scan rate of 10 mV / s at a rotation speed of 1600 rpm in the voltage range where the ring voltage is 1.3 V (relative to the standard hydrogen electrode) and the disk voltage is -0.35 to 0.55 V (relative to the silver chloride electrode). The data is collected after the scanning current is stable. The electrochemical impedance (EIS) measurement is carried out at a voltage of 0.68 V (relative to the silver chloride electrode) in the frequency range of 0.01 - 10 5 Hz.

[0046] Zn1-Co / CoSe 2-x Test for electrocatalytic oxygen reduction to hydrogen peroxide:

[0047] Prepare the Zn1-Co / CoSe 2-x catalyst dispersion according to the aforementioned method. Spray 200 μL of the Zn1-Co / CoSe 2-x catalyst dispersion on a 2.5 cm × 2.5 cm gas diffusion carbon paper to obtain a working electrode sheet. A graphite rod and a saturated silver chloride electrode are respectively used as the counter electrode and the reference electrode, and the electrocatalytic oxygen reduction to hydrogen peroxide test is carried out in a flow electrolytic cell. The test electrolyte is 0.1 mol / L HClO4 solution. Under the oxygen-saturated state, the hydrogen peroxide yield diagram at different current densities is obtained. And test the stability of the prepared Zn1-Co / CoSe 2-x catalyst during the electrocatalytic oxygen reduction to hydrogen peroxide, and obtain the stability curve diagram at a voltage of 0 V (relative to the standard hydrogen electrode).

[0048] Comparative Example 1:

[0049] (1). The same as step (1) of Example 1.

[0050] (2). The o-CoSe obtained in step (1) 2-xThe powder was placed in a quartz boat, and the quartz boat was put into a tubular furnace for calcination. The calcination temperature was 350 °C, and the calcination time was 2 h. The finally obtained catalyst was denoted as CoSe 2-x -350.

[0051] CoSe 2-x The process for testing the electrochemical performance of the -350 catalyst was the same as that of Zn1-Co / CoSe in Example 1 2-x For the process of testing the electrochemical performance of the catalyst, only Zn1-Co / CoSe 2-x The catalyst was replaced with CoSe 2-x The -350 catalyst will not be elaborated here.

[0052] Comparative Example 2:

[0053] (1). The same as step (1) of Example 1.

[0054] (2). 0.00744 g (0.025 mmol) of zinc nitrate hexahydrate and 0.0945 g of o-CoSe prepared in step (1) were weighed according to the Zn / Co molar ratio of 0.05:1 2-x powder, and the remaining operations were the same as those in step (2) of Example 1.

[0055] (3). The same as step (3) of Example 1, and finally, Zn-Co / CoSe containing Zn clusters was obtained 2-x catalyst, denoted as Zn c -Co / CoSe 2-x .

[0056] Zn c -Co / CoSe 2-x The process for testing the electrochemical performance of the Zn-Co / CoSe catalyst was the same as that of Zn1-Co / CoSe in Example 1 2-x For the process of testing the electrochemical performance of the catalyst, only Zn1-Co / CoSe 2-x The catalyst was replaced with Zn c -Co / CoSe 2-x The catalyst will not be elaborated here.

[0057] Figure 1 are the high-resolution transmission electron microscopy (HRTEM) image (a), transmission electron microscopy (TEM) image (b), selected area electron diffraction (SAED) pattern (c), and selected area intensity distribution pattern (d) of the powdered Zn1-Co / CoSe catalyst prepared in Example 1. Among them, the TEM image shows Zn1-Co / CoSe 2-x 2-x ​The catalyst presents a nanorod morphology, and the diameter of the nanorods is approximately 30 - 150 nm. The HRTEM image shows a clear lattice spacing of 0.253 nm attributed to the (111) crystal plane of o-CoSe2 ( Figure 1 in c), and some defect sites are formed. The selected area electron diffraction (SAED) pattern shows its polycrystalline characteristics. The corresponding intensity profiles along the selected rectangular region also indicate the presence of Se defects in Zn1-Co / CoSe 2-x ( Figure 1 in d).

[0058] Figure 2 is the XRD pattern of the catalysts prepared in Example 1 and Comparative Examples 1 - 2. The XRD peak positions of Zn1-Co / CoSe 2-x , Zn c -Co / CoSe 2-x , CoSe 2-x -350 correspond well to the standard PDF card of orthorhombic CoSe2 at the bottom. Therefore, in Example 1 and Comparative Examples 1 - 2, mainly orthorhombic o-CoSe 2-x is formed.

[0059] Figure 3 is the Raman spectrum of the catalysts prepared in Example 1 and Comparative Examples 1 - 2. The characteristic peaks of all samples at around 168 cm -1 and 668 cm -1 respectively indicate the A g and A 1g stretching modes of o-CoSe2. Compared with Zn c -Co / CoSe 2-x and CoSe 2-x -350, Zn1-Co / CoSe 2-x shows a more obvious A 1g red shift, indicating that the introduction of Zn leads to lattice expansion of the CoSe 2-x substrate.

[0060] Figure 4 is the XPS spectrum of the catalysts prepared in Example 1 and Comparative Examples 1 - 2. It can be seen that compared with Comparative Example 1 and Comparative Example 2, the Co 2p band of Zn1-Co / CoSe 2-x shifts negatively, indicating that Co becomes an electron-rich center after charge redistribution, which may be caused by the strong interaction between the anchored Zn atoms and Co atoms. The Se 3d band of Zn1-Co / CoSe 2-x shifts towards a lower binding energy direction, while that of Zn c -Co / CoSe 2-x shifts towards a higher binding energy direction, suggesting an antagonistic relationship between Se vacancies and Zn doping. In particular, Zn 2p3 / 2 The band moves towards the direction of higher binding energy, confirming its electron loss process.

[0061] Figure 5 are the EPR diagrams of the catalysts prepared in Example 1 and Comparative Examples 1-2. It can be seen that all samples exhibit symmetric EPR signals. g = 2.004 is due to the unpaired electrons at the selenium defect sites. Compared with Zn1-Co / CoSe 2-x and Zn c -Co / CoSe 2-x , CoSe 2-x -350 shows the lowest signal intensity of selenium vacancies, indicating the least amount of defects; while Zn c -Co / CoSe 2-x shows a higher EPR signal intensity than Zn1-Co / CoSe 2-x , indicating that Zn atoms have successfully replaced some Co atoms through substitution reaction to form Zn single atoms and formed Zn-Co pair sites with adjacent Co. And Zn c -Co / CoSe 2-x forms more clusters on the substrate surface.

[0062] Figure 6 are the electrochemical impedance spectroscopy (EIS) diagrams of the catalysts prepared in Example 1 and Comparative Examples 1-2. The equivalent circuit diagrams fitted from the electrochemical impedance spectroscopy (EIS) curves show that the R2 and R3 values of Zn1-Co / CoSe 2-x are the lowest, indicating that under the condition of appropriate Zn doping, the electron transfer kinetics of Zn1-Co / CoSe 2-x is higher.

[0063] Figure 7 are the polarization curves of the catalysts prepared in Example 1 and Comparative Examples 1-2 for two-electron oxygen reduction (2e - ORR). It can be seen that among the three catalysts, the ring current density of Zn1-Co / CoSe 2-x is significantly the highest, indicating that its two-electron oxygen reduction ability is the largest and the selectivity is the best.

[0064] Figure 8 are the selectivity and electron transfer number diagrams of the catalysts prepared in Example 1 and Comparative Examples 1-2 for electrocatalytic oxygen reduction to hydrogen peroxide. It can be seen that the selectivity of the Zn1-Co / CoSe 2-x catalyst for electrocatalytic oxygen reduction to hydrogen peroxide is the highest, reaching up to 95% at 0.65 V (versus standard hydrogen electrode), and greater than 80% at 0.25 - 0.65 V (versus standard hydrogen electrode). Figure 8 also shows that Zn1-Co / CoSe 2-xCatalyst, Zn c -Co / CoSe 2-x Catalyst and CoSe 2-x The electron transfer numbers of the Zn1-Co / CoSe 2-x -350 catalysts are 2.48, 3.13, and 3.12, respectively. Among them, the electron transfer number of the Zn1-Co / CoSe

[0065] Figure 9 Figure is the Tafel slope diagram of the catalysts prepared in Example 1 and Comparative Examples 1-2. It can be seen that for Zn1-Co / CoSe 2-x , Zn c -Co / CoSe 2-x , CoSe 2-x -350, the Tafel slopes are 143 mV dec -1 , 193 mV dec -1 , 186 mV dec -1 , respectively. Therefore, the Tafel slope of Zn1-Co / CoSe 2-x is the lowest, indicating a faster kinetic process.

[0066] Figure 10 Figure is the double-layer capacitance diagram of the catalysts prepared in Example 1 and Comparative Examples 1-2. It can be seen that for Zn1-Co / CoSe 2-x , Zn c -Co / CoSe 2-x , CoSe 2-x -350 catalysts, the double-layer capacitances are 0.26 mF cm -2 , 0.24 mF cm -2 , 0.23 mF cm -2 , respectively. Therefore, the Zn1-Co / CoSe 2-x catalyst has a relatively high double-layer capacitance, indicating that the Zn1-Co / CoSe 2-x catalyst has high electrochemcial activity, which is beneficial to the 2e - ORR process.

[0067] Figure 11 Figure is the stability diagram of the electrocatalytic oxygen reduction to hydrogen peroxide over the Zn1-Co / CoSe 2-x catalyst prepared in Example 1. During the stability test, 200 μL of the Zn1-Co / CoSe 2-x catalyst dispersion (Zn1-Co / CoSe 2-xUsing the gas diffusion carbon paper prepared by the method for preparing the catalyst dispersion as described above as the working electrode sheet, a graphite rod and a silver chloride electrode are used as the counter electrode and the reference electrode respectively, and the test is carried out in a flowing electrolytic cell. The cathode and anode electrolytes are 1000 mL of 0.1 mol / L HClO4 solution and 40 mL of 0.1 mol / L HClO4 solution respectively. Chronopotentiometry is used at a current density of 100 mA cm -2 The stability test is carried out at a current density and a voltage of 0 V (relative to the standard hydrogen electrode). The cathode electrolyte is replaced every 5 hours. 50 μL of the cathode electrolyte is sampled and mixed with 3.95 μL of the cerium sulfate solution to test the cumulative production of hydrogen peroxide and calculate the Faraday efficiency, and the Zn1-Co / CoSe 2-x catalyst sample's stability diagram of electrocatalytic oxygen reduction to hydrogen peroxide is as Figure 11 shown. It can be seen that after 30 h of the stability test, Zn1-Co / CoSe 2-x has not been deactivated, and the Faraday efficiency can be stabilized above 70%, indicating that Zn1-Co / CoSe 2-x catalyst has good stability.

[0068] Figure 12 is the production rate diagram and the Faraday efficiency diagram of the Zn1-Co / CoSe 2-x catalyst prepared in Example 1 for electrocatalytic oxygen reduction to hydrogen peroxide. Among them, the bar graph represents the production rate of hydrogen peroxide, and the line graph represents the Faraday efficiency. It can be seen that at a current density of 50 mA cm -2 , the Faraday efficiency can be close to 100%. At a large current density of 250 mA cm -2 , the hydrogen peroxide production rate is 2.26 mol g cat. -1 h -1 , which is much higher than the hydrogen peroxide production rate of the two-electron oxygen reduction catalyst based on non-precious metal compounds reported at present for electrocatalytic oxygen reduction to hydrogen peroxide under acidic conditions.

[0069] Figure 13 is the degradation diagram of the hydrogen peroxide electrocatalytically produced by the Zn1-Co / CoSe 2-x catalyst prepared in Example 1 for rhodamine B (RhB). The experiment of electro-Fenton degradation of rhodamine B is carried out in a flowing electrolytic cell. The volume of the cathode electrolyte is 40 mL, and its composition is 50 ppm of rhodamine B, 0.5 M Na2SO4 and 0.5 mM FeSO4, and the pH of the electrolyte is 2.85. The cathode electrode is Zn1-Co / CoSe 2-x / CP, Zn1-Co / CoSe 2-xThe loading amount on the carbon paper (CP) is 1 mg, and the effective working area is 1 cm × 1 cm. During the test of electro-Fenton degradation of rhodamine B, 100 μL of the outer circulation electrolyte was taken out from the cathode chamber of the flow electrolytic cell at intervals, diluted with 3.0 mL of 0.5 M Na2SO4 solution with a pH of 2.85, and the absorbance of rhodamine B in the diluted solution was detected with a UV spectrophotometer. The absorbance of rhodamine B at different degradation times was plotted against the degradation time to obtain the change curve of the absorbance of rhodamine B in the solution with the degradation time, as shown in Figure 13 (a) in. The absorbance of rhodamine B measured at different degradation times was substituted into the standard linear equation of the absorbance of rhodamine B against the concentration to obtain the remaining concentration C of rhodamine B in the solution at different degradation times t`RhB , with C t`RhB / C 0`RhB as the ordinate (C 0`RhB is the initial concentration of rhodamine B), and the degradation time as the abscissa was plotted, as shown in Figure 13 (b) in. It can be seen from Figure 13 that most (90%) of RhB was degraded after 160 min, indicating that this is a rapid electro-Fenton process. At the same time, a small amount of RhB was adsorbed in the pores of the carbon paper, making it not easily degraded.

[0070] Figure 14 is the Gibbs free energy and density of states diagram of the Zn1-Co / CoSe 2-x catalyst prepared in Example 1. It can be seen that compared with other models, due to the effective hybridization of the p y orbital of the proximal O of *OOH and the d yz orbital of Co near the Fermi level, the Co atoms around the Zn-Co pair sites in Zn1-Co / CoSe 2-x have the best Gibbs adsorption energy for the *OOH intermediate, around 4.228 eV (ΔG *OOH ~4.228 eV), which is very close to the ideal value of 4.2 eV.

[0071] The above are only examples of the present invention and do not impose any formal restrictions on the present invention. The present invention can also have other forms of embodiments based on the above structure and function, which will not be listed one by one. Therefore, any person skilled in the art, without departing from the scope of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A preparation method of a Se-defect-induced Zn1-Co / CoSe catalyst containing Zn-Co pair sites, characterized in that 2-x Specifically, it includes the following steps: ​ (1) Weigh a certain amount of selenium powder and add it to a beaker containing NaOH solution, and stir vigorously to obtain a mixed material A; weigh a certain amount of metal cobalt salt and add it to a beaker containing 0.25M EDTA-2Na solution, and stir vigorously to obtain a mixed material B; add the mixed material B to the mixed material A and stir to obtain a mixed material C; transfer the mixed material C to a hydrothermal reaction kettle for hydrothermal reaction, the temperature of the hydrothermal reaction is 200°C, and the reaction time is 6h; After the hydrothermal reaction was completed, the reaction kettle was naturally cooled to room temperature. The products in the reaction kettle were centrifuged, and the precipitate was collected. The precipitate was ultrasonically washed 3 times with HCl solution, then centrifuged, and then centrifugally washed with ultrapure water until neutral. The precipitate was collected and placed in a blast drying oven and dried at 60 °C for 12 h to obtain Se-deficient orthorhombic cobalt selenide powder, denoted as o-CoSe 2-x powder; (2) Weigh a certain amount of metal zinc salt and a certain amount of the o-CoSe powder obtained in step (1), mix them, then add absolute ethanol thereto, stir for 12 h, let stand for 12 h, and subsequently transfer the mixture into a forced-air drying oven and dry at 60 °C for 12 h to obtain Zn-doped CoSe powder; 2-x 2-x powder; (3) Grind the Zn-doped CoSe prepared in step (2) in a mortar, then put it into a quartz boat, place the quartz boat in a tube furnace for roasting at a roasting temperature of 350 °C for 2 h to obtain a Se defect-induced Zn1-Co / CoSe catalyst containing Zn-Co pair sites. 2-x 2-x catalyst.

2. The preparation method of the Se defect-induced Zn1-Co / CoSe catalyst containing Zn-Co dual sites as described in claim 1, characterized in that 2-x The metal cobalt salt described in step (1) is one of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, and cobalt acetate tetrahydrate. ​ 3. The preparation method of the Se defect-induced Zn1-Co / CoSe catalyst containing Zn-Co pair sites as described in claim 1 2-x , characterized in that In step (1), the molar ratio of selenium powder to metal cobalt salt is 1.65 - 1.85:

1.

4. Preparation method of Se defect-induced Zn1-Co / CoSe catalyst containing Zn-Co pair sites as described in claim 1, characterized in that 2-x In step (1), the concentration of the NaOH solution is 3.33mol / L, and the concentration of the HCl solution is 0.1 - 1mol / L. ​ 5. Preparation method of Se defect-induced Zn1-Co / CoSe catalyst containing Zn-Co pair sites as described in claim 1 2-x , characterized in that In step (2), a certain amount of metal zinc salt and a certain amount of o-CoSe powder obtained in step (1) are weighed according to a Zn / Co molar ratio of 0.001 to 0.05:1 2-x powder.

6. The preparation method of the Se defect-induced Zn1-Co / CoSe catalyst containing Zn-Co pair sites as described in claim 1 or 5, characterized in that 2-x In step (2), a certain amount of metal zinc salt and a certain amount of o-CoSe powder obtained in step (1) are weighed according to a Zn / Co molar ratio of 0.03:1 2-x powder. ​ 7. The Se defect-induced Zn1-Co / CoSe catalyst containing Zn-Co pair sites obtained by the preparation method according to claim 1 2-x catalyst.

8. The Se defect-induced Zn1-Co / CoSe catalyst containing Zn-Co pair sites according to claim 7 2-x , characterized in that It has a nanorod morphology, and the diameter of the nanorods is 30 - 50nm.

9. Application of the Se defect-induced Zn1-Co / CoSe catalyst containing Zn-Co pair sites obtained by the preparation method according to claim 1 in electrocatalytic oxygen reduction for hydrogen peroxide production. 2-x ​ 10. The application according to claim 9, characterized in that, The Zn1-Co / CoSe 2-x catalyst is used for electrocatalytic oxygen reduction to hydrogen peroxide in acidic media.

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