Zinc-based gas diffusion electrode, preparation method and application thereof

Abstract

The invention discloses a zinc-based gas diffusion electrode material, and a preparation method and application thereof, and the preparation method comprises the following steps: dissolving zinc acetate powder and glycerin in an ethanol solution, and carrying out a hydrothermal reaction to generate zinc glycerate; and calcining the dried zinc glycerate powder in a natural air atmosphere to obtain the gas diffusion electrode material containing a certain proportion of crystal pore cavities. The material is loaded on a carbon substrate and treated to obtain the zinc-based gas diffusion electrode. When the electrode is applied to a cathode of an electrolytic tank, excellent performance of synthesizing hydrogen peroxide through electro-catalysis air reduction is shown, the proportion of crystal holes in the electrode can be regulated and controlled by regulating and controlling experimental parameters, a crystal hole-crystal type homojunction structure is formed, the conductivity of the material is increased, and the capturing capacity of oxygen in air is enhanced; ultrahigh gas mass transmission efficiency and oxygen utilization rate are realized, and high energy loss caused by the fact that traditional oxygen is used as reaction gas of a gas diffusion electrode is avoided.

Description

Technical Field

[0001] The invention relates to a zinc-based gas diffusion electrode, belonging to the technical field of electrode preparation. Background Art

[0002] In the context of reducing carbon emissions and achieving carbon neutrality, the production of hydrogen peroxide by oxygen electrolysis is a clean and green production method. The theoretical research on oxygen electrolysis is relatively mature and can achieve relatively ideal yields. The development of liquid flow electrolysis cells is an important milestone in promoting the transformation of oxygen electrolysis equipment and the industrialization of electrocatalytic production of hydrogen peroxide. As a type of advanced commercializable reaction system developed in recent years, it is highly favored in the field of electrocatalytic oxygen reduction. Compared with traditional H-type electrolysis cells, the core component of liquid flow electrolysis cells, the gas diffusion electrode (GDE), can assist in the construction of a three-phase reaction interface of catalyst / electrolyte / reaction gas, thereby improving the catalytic reaction efficiency and the yield of hydrogen peroxide. Although the gas diffusion electrode improves the oxygen utilization rate to a certain extent, its improvement is ultimately limited. Improving the kinetics alone cannot solve the fundamental problem. The unreacted oxygen in the electrolysis process also causes additional energy consumption.

[0003] The high cost of preparing, storing and transporting pure oxygen has greatly limited the industrial development of oxygen electrolysis to produce hydrogen peroxide. Compared with pure oxygen electrolysis, direct air electrolysis technology is superior. The main challenge at present is that the hydrogen peroxide production and efficiency are low in the air electrolysis cathode system. In addition, compared with pure oxygen, the oxygen content in natural air is not sufficient, and there are a large amount of nitrogen and other impurity gases. Due to the above challenges, the kinetic and thermodynamic activities of the catalyst are limited. In this case, the excess nitrogen flows into the electrolytic cell, which not only hinders the mass transfer of oxygen, but also occupies the active catalytic surface, further reducing the activity of the catalyst, the hydrogen peroxide yield and the electrolysis efficiency. Under industrial production conditions, achieving ideal hydrogen peroxide production and efficiency at a higher diffusion current density plays a vital role, which is also an important limiting factor restricting the application of air electrolysis in the industrial production of hydrogen peroxide. Summary of the invention

[0004] The object of the present invention is to provide a zinc-based gas diffusion electrode material and a preparation method thereof, and application thereof in rapid electrocatalytic air reduction to synthesize hydrogen peroxide.

[0005] The technical solution to achieve the purpose of the present invention is:

[0006] A method for preparing a zinc-based sub-nanocrystalline gas diffusion electrode material comprises the following steps:

[0007] Step 1: dissolving zinc acetate and glycerol in ethanol and stirring to form a uniform mixed solution;

[0008] Step 2: placing the mixed solution obtained in step 1 in a sealed environment and heating it for a period of time;

[0009] Step 3: calcining the material obtained in step 2 in an air atmosphere for a period of time to obtain a zinc-based gas diffusion electrode material.

[0010] Furthermore, in step 1, the ratio of zinc acetate, glycerol and ethanol is 1 g:10 mL:50 mL to 1 g:50 mL:500 mL.

[0011] Furthermore, in step 2, the heating temperature is 60-200° C. in a closed environment, and the reaction is carried out for 5-40 hours.

[0012] Furthermore, in step three, the calcination temperature is 200-600° C., and the calcination time is 0.5-4 h.

[0013] The invention provides a zinc-based sub-nanocrystalline pore gas diffusion electrode material, which has sub-nanoscale crystal pores.

[0014] In addition, the present invention also provides a zinc-based sub-nanocrystalline pore gas diffusion electrode. The zinc-based sub-nanocrystalline pore gas diffusion electrode material, the adhesive Nafion, and the conductive agent carbon black are evenly dispersed with isopropanol to prepare a catalyst dispersion liquid, which is then dripped onto a carbon substrate and dried naturally; and then assembled with a polytetrafluoroethylene film to form a zinc-based sub-nanocrystalline pore gas diffusion electrode.

[0015] Finally, the present invention also provides a use of a zinc-based sub-nanocrystalline pore gas diffusion electrode material as a catalyst for rapid electrocatalytic air reduction to synthesize hydrogen peroxide.

[0016] Compared with the prior art, the advantages of the present invention are as follows: (1) the electrode is composed of zinc-based sub-nanocrystalline porous materials to form an air diffusion electrode, the preparation method is simple, and large-scale industrial production can be carried out; (2) the sub-nanocrystalline pores are conducive to the exposure of more active sites, providing abundant active sites; (3) the gas source of the air diffusion electrode is natural air, eliminating the high cost of pure oxygen production and transportation and the waste of oxygen in the reaction process; (4) the current density is close to the theoretical limit current condition (300mAcm -2 ) At this time, the Faraday efficiency of air electrolysis to produce hydrogen peroxide can still be maintained at around 90%, which has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the synthesis route for preparing the zinc-based gas diffusion electrode of the present invention.

[0018] Figure 2These are TEM images of Example 1 and Comparative Example 1 of the present invention, wherein (a) is the overall morphology of the particles of Example 1, (b) is a high-resolution TEM local image of Example 1, (c) is the overall morphology of the particles of Comparative Example 1, and (d) is a high-resolution TEM local image of Comparative Example 1.

[0019] Figure 3 The present invention is the sub-nanometer scale pore sites (b) marked in the high-resolution TEM image of Example 1, and the pore site size measurement (c).

[0020] Figure 4 (a) is the full spectrum image of X-ray photoelectron spectroscopy (XPS) of comparative example 1 of the present invention, wherein (b) is the full spectrum image of XPS of Example 1 of the present invention, (c) is the characteristic spectrum of Zn element 2p of Example 1 of the present invention and comparative example 1d, and (d) is the characteristic spectrum of O1s element of Example 1 of the present invention and comparative example 1.

[0021] Figure 5 (a) is the X-ray diffraction pattern (XRD) of Example 1 of the present invention and Comparative Example 1, and (b) is the electron paramagnetic resonance spectrum (EPR) of Example 1 of the present invention and Comparative Example 1.

[0022] Figure 6 It is the RRDE data diagram of Example 1 of the present invention, wherein (a) is the CV curve of Example 1 in argon, air, and oxygen, (b) is the LSV polarization curve of Example 1 tested in air, and the corresponding selectivity (c) and the number of transferred electrons (d).

[0023] Figure 7 1 is a test data graph of a liquid flow cell in air of Example 1 of the present invention, wherein (a) is the LSV polarization curve of Example 1 in argon and air, and (b) is the yield and Faraday efficiency of producing hydrogen peroxide by air electrolysis in a liquid flow cell of Example 1.

[0024] Figure 8 1 is a curve of the potential change of the electrode of Example 1 of the present invention at different currents (a), the inset shows the absorbance of the product hydrogen peroxide after color development at different currents, and the stability test of the material of Example 1 in air (b).

[0025] Fig. 9 The electrode performance data (a), RRDE test curve (b), selectivity (c) and number of transferred electrons (d) constructed by Zn-based-CH-1 in Example 2 of the present invention are shown.

[0026] Fig.10 The electrode performance data (a), RRDE test curve (b), selectivity (c) and number of transferred electrons (d) constructed by Zn-based-CH-3 in Example 3 of the present invention are shown.

[0027] Fig.11 The electrode performance data (a), RRDE test curve (b), selectivity (c) and number of transferred electrons (d) constructed by Zn-based-CH-4 in Example 4 of the present invention are shown.

[0028] Fig.12 The electrode performance data (a), RRDE test curve (b), selectivity (c) and number of transferred electrons (d) constructed by Zn-based-CH-6 in Example 5 of the present invention are shown.

[0029] Fig.13 The electrode performance data (a), RRDE test curve (b), selectivity (c) and number of transferred electrons (d) constructed by Zn-based-CH-8 in Example 6 of the present invention are shown.

[0030] Fig.14 The electrode performance data (a), RRDE test curve (b), selectivity (c) and number of transferred electrons (d) constructed by Zn-based-CH-10 in Example 7 of the present invention are shown.

[0031] Fig.15 The electrode performance data (a), RRDE test curve (b), selectivity (c) and number of transferred electrons (d) constructed by the zinc-based amorphous porous material Zn-based-NCH in comparative example 1 of the present invention are shown.

[0032] Fig.16 1 is a data graph of economic analysis of Example 1 of the present invention in oxygen and air, wherein (a) is a single factor analysis in oxygen, (b) is the cost proportion in oxygen, (c) is a single factor analysis in air, (d) is the cost proportion in air, (e) is the cost of producing hydrogen peroxide by Zn-based-CH in air and oxygen and Zn-based-NCH in air, and (f) is a comparative analysis of the cumulative net present value of producing hydrogen peroxide in oxygen and air.

[0033] Fig.17 The invention discloses a synthesis route and a schematic diagram of the zinc-based sub-nanocrystalline gas diffusion electrode material. DETAILED DESCRIPTION

[0034] Oxygen electrolysis to produce hydrogen peroxide is a green, clean and sustainable production method. However, the high preparation and transportation costs of pure oxygen have curbed the industrial application of oxygen electrolysis to produce hydrogen peroxide. The gas diffusion electrode has an upper limit to the improvement of oxygen utilization. A large amount of oxygen will also be wasted during the electrolysis process, resulting in energy waste, which is not conducive to the further application of hydrogen peroxide in the treatment of wastewater and organic pollutants. Therefore, reducing production costs is the focus of expanding the downstream application of hydrogen peroxide and making it enter industrialization. Inspired by the above phenomenon, on this basis, we innovatively proposed a zinc-based sub-nanocrystalline porous material (Zn-based-CH), which can be used to construct a gas diffusion electrode for rapid catalytic air production of hydrogen peroxide. The structure of the sub-nanocrystalline pores can be effectively regulated by the content of glycerol in the reactants, thereby forming a gas diffusion electrode with rich catalytic active sites, stable structure and simple preparation. The gas diffusion electrode constructed using the above electrode can be produced in a liquid flow device. It is worth noting that the zinc-based sub-nanocrystalline porous material is expected to achieve record hydrogen peroxide production performance in air electrolysis oxygen reduction, with excellent activity, selectivity and durability, and improve the economic benefits of electrochemical production of hydrogen peroxide.

[0035] Embodiment 1:

[0036] Step 1: Dissolve 0.26 g zinc acetate and 2 mL glycerol in 29.6 mL ethanol and stir for 30 min to form a uniform mixed solution;

[0037] Step 2: Heat the mixed solution obtained in step 1 at 180° C. in a sealed environment for 24 hours;

[0038] Step 3: calcining the material obtained in step 2 at 400°C for 1h in natural air atmosphere to obtain zinc-based sub-nanocrystalline porous material Zn-based-CH, the XPS quantitative analysis of which is shown in Table 1;

[0039] Step 4: The zinc-based sub-nanocrystalline pore catalytic material obtained in step 3 is combined with Nafion, carbon black, carbon substrate, and polytetrafluoroethylene film to form a zinc-based sub-nanocrystalline pore gas diffusion electrode.

[0040] Embodiment 2:

[0041] Step 1: Dissolve 0.26 g zinc acetate and 1 mL glycerol in 29.6 mL ethanol and stir for 30 min to form a uniform mixed solution;

[0042] Step 2: Heat the mixed solution obtained in step 1 at 180° C. in a sealed environment for 24 hours;

[0043] Step 3: calcining the material obtained in step 2 at 400°C for 1 h in a natural air atmosphere to obtain Zn-based-CH-1;

[0044] Step 4: The Zn-based-CH-1 catalytic material obtained in step 3 is combined with Nafion, carbon black, carbon substrate, and polytetrafluoroethylene film to form a zinc-based sub-nanocrystalline pore gas diffusion electrode.

[0045] Embodiment 3:

[0046] Step 1: Dissolve 0.26 g zinc acetate and 3 mL glycerol in 29.6 mL ethanol and stir for 30 min to form a uniform mixed solution;

[0047] Step 2: Heat the mixed solution obtained in step 1 at 180° C. in a sealed environment for 24 hours;

[0048] Step 3: calcining the material obtained in step 2 at 400°C for 1 h in a natural air atmosphere to obtain Zn-based-CH-3;

[0049] Step 4: The Zn-based-CH-3 catalytic material obtained in step 3 is combined with Nafion, carbon black, carbon substrate, and polytetrafluoroethylene film to form a zinc-based sub-nanocrystalline pore gas diffusion electrode.

[0050] Embodiment 4:

[0051] Step 1: Dissolve 0.26 g zinc acetate and 4 mL glycerol in 29.6 mL ethanol and stir for 30 min to form a uniform mixed solution;

[0052] Step 2: Heat the mixed solution obtained in step 1 at 180° C. in a sealed environment for 24 hours;

[0053] Step 3: calcining the material obtained in step 2 at 400°C for 1 h in a natural air atmosphere to obtain Zn-based-CH-4;

[0054] Step 4: The Zn-based-CH-4 catalytic material obtained in step 3 is combined with Nafion, carbon black, carbon substrate, and polytetrafluoroethylene film to form a zinc-based sub-nanocrystalline pore gas diffusion electrode.

[0055] Embodiment 5:

[0056] Step 1: Dissolve 0.26 g zinc acetate and 6 mL glycerol in 29.6 mL ethanol and stir for 30 min to form a uniform mixed solution;

[0057] Step 2: Heat the mixed solution obtained in step 1 at 180° C. in a sealed environment for 24 hours;

[0058] Step 3: calcining the material obtained in step 2 at 400°C in a natural air atmosphere for 1 h to obtain Zn-based-CH-6;

[0059] Step 4: The Zn-based-CH-6 catalytic material obtained in step 3 is combined with Nafion, carbon black, carbon substrate, and polytetrafluoroethylene film to form a zinc-based sub-nanocrystalline pore gas diffusion electrode.

[0060] Embodiment 6:

[0061] Step 1: Dissolve 0.26 g zinc acetate and 8 mL glycerol in 29.6 mL ethanol and stir for 30 min to form a uniform mixed solution;

[0062] Step 2: Heat the mixed solution obtained in step 1 at 180° C. in a sealed environment for 24 hours;

[0063] Step 3: calcining the material obtained in step 2 at 400°C for 1 h in a natural air atmosphere to obtain Zn-based-CH-8;

[0064] Step 4: The Zn-based-CH-8 catalytic material obtained in step 3 is combined with Nafion, carbon black, carbon substrate, and polytetrafluoroethylene film to form a zinc-based gas diffusion electrode.

[0065] Embodiment 7:

[0066] Step 1: Dissolve 0.26 g zinc acetate and 10 mL glycerol in 29.6 mL ethanol and stir for 30 min to form a uniform mixed solution;

[0067] Step 2: Heat the mixed solution obtained in step 1 at 180° C. in a sealed environment for 24 hours;

[0068] Step 3: calcining the material obtained in step 2 at 400° C. for 1 h in a natural air atmosphere to obtain Zn-based-CH-10;

[0069] Step 4: The Zn-based-CH-10 catalytic material obtained in step 3 is combined with Nafion, carbon black, carbon substrate, and polytetrafluoroethylene film to form a zinc-based sub-nanocrystalline pore gas diffusion electrode.

[0070] Comparative Example 1:

[0071] Step 1: Dissolve 0.26 g zinc acetate in 29.6 mL ethanol and stir for 30 min to form a uniform mixed solution;

[0072] Step 2: Heat the mixed solution obtained in step 1 at 180° C. in a sealed environment for 24 hours;

[0073] Step 3: calcining the material obtained in step 2 at 400°C for 1h in a natural air atmosphere to obtain a zinc-based amorphous porous gas diffusion electrode material Zn-based-NCH, the XPS quantitative analysis of which is shown in Table 1;

[0074] Step 4: The Zn-based-NCH catalytic material obtained in step 3 is combined with Nafion, carbon black, carbon substrate, and polytetrafluoroethylene film to form a zinc-based amorphous porous gas diffusion electrode.

[0075] Table 1 shows the atomic content and sub-nanocrystalline pore ratio of Example 1 and Comparative Example 1 quantitatively analyzed by XPS.

[0076] Material Zinc atomic ratio % Oxygen atomic ratio% Sub-nanopore ratio% Zn-based-NCH 49.62 50.38 1.51 Zn-based-CH 47.72 52.28 8.72

[0077] Figure 1 (a) is a schematic diagram of the assembly of the zinc-based sub-nanocrystalline gas diffusion electrode of the present invention, in which the catalyst material is loaded on the hydrophobic side of the carbon substrate, and a polytetrafluoroethylene film (PTFE) is covered on the side where the catalyst material is not loaded, forming a gas diffusion electrode, which is assembled into an electrolytic cell to become a cathode, and a cationic membrane is used to separate the cathode and the anode. Figure 1 (b) shows a real picture of the gas diffusion electrode assembled into an electrolytic cell.

[0078] The TEM image of the zinc-based sub-nanocrystalline gas diffusion electrode material obtained in Example 1 (Zn-based-CH) is as follows: Figure 2 As shown in (a), compared with Comparative Example 1 (Zn-based-NCH) ( Figure 2 Compared with (c) in Figure 2, the overall morphology of the material has not changed significantly, and Zn-based-CH basically retains the particle size of Zn-based-NCH. When the local part of the material is further magnified, the high-resolution TEM ( Figure 2 The image (b) shows uniformly dispersed sub-nanometer pore sites, and the pore sizes are basically the same, while the image of Zn-based-NCH ( Figure 2 (d)) in the figure shows relatively regular lattice fringes, and the crystal structure of the material has not changed.

[0079] In order to further determine the specific characteristics of the defects in Zn-based-CH, we further magnified the high-resolution TEM image and found that the lattice fringes of the Zn-based-CH material had dislocation fractures, such as Figure 2 In the lower left corner of (b), two different crystal planes (101) and (100) appear on both sides of the fracture surface. However, more crystal holes appear in the form of point crystal holes, which we will also Figure 2 The local magnification of the crystal hole site in (b) is further observed. Figure 3 In (a), two crystal holes are clearly marked and their sizes are measured, such as Figure 3 (b) We found that the size of the pores reached the sub-nanometer scale of about 0.25nm.

[0080] Figure 4 (a) and (b) clearly show the X-ray photoelectron spectra of the materials of Example 1 (Zn-based-CH) and Comparative Example 1 (Zn-based-NCH). By comparing the full XPS spectra of Zn-based-CH and Zn-based-NCH, it is found that there is almost no difference between the two, indicating that Zn-based-CH has relatively intactly retained the characteristics of Zn-based-NCH while introducing sub-nano pores, which indirectly proves that the size of the pore site is small. Figure 4 (c) and (d) in the figure show the characteristic orbital spectra of Zn and O elements in Zn-based-CH and Zn-based-NCH. By comparison, it is found that the intensity of the Zn 2p characteristic peak of Zn-based-CH is slightly weaker than that of Zn-based-NCH, indicating that the Zn content is lower than that of Zn-based-NCH; at the same time, the peaks at ~530eV and ~531eV in the O1s characteristic spectrum of Zn-based-CH increase in intensity compared with those of Zn-based-NCH, which is attributed to the nucleation changes and surface energy changes caused by the formation of crystal pores.

[0081] In addition, according to the characteristic peaks of Zn and O in the XPS spectrum, we analyzed the element content of Zn-based-CH and Zn-based-NCH. The atomic percentages of the elements and the pore ratios are shown in Table 1. The fact that there are more O atoms than Zn atoms in Zn-based-NCH may be due to water or other oxygen-containing impurities on the surface of the material during the test. The sub-nano pore ratio of Zn-based-CH reached 8.72%, and combined with TEM and other data, it was shown that Zn-based-CH introduced abundant sub-nano pores without causing drastic changes in the crystal structure.

[0082] In addition, X-ray diffraction analysis (XRD) was used to further study the crystal structures of Zn-based-CH and Zn-based-NCH, such as Figure 5 As shown in (a) in the figure. By comparison, it is found that the peak intensity of Zn-based-CH is weaker than that of Zn-based-NCH, but the positions of the peaks are consistent, indicating that the crystal planes in Zn-based-CH have not changed, only the number of crystal planes has decreased, and the introduction of sub-nano pores has not caused significant changes in the crystals. Figure 5 (b) shows the electron paramagnetic resonance spectra of Zn-based-CH and Zn-based-NCH. It can be clearly seen that the EPR signal of Zn-based-CH material at g = 2.0040 is stronger than that of Zn-based-NCH, proving the existence of sub-nanocrystalline holes in Zn-based-CH.

[0083] For the rotating disk electrode, CVs were collected at 1600 rpm in Ar, air, and O2-saturated electrolyte. Figure 6 (a) in the figure shows that within the set potential range, Zn-based-CH can achieve a higher current density in an O2 atmosphere, but also has a relatively ideal current response in air, which is a significant improvement over the results in an Ar environment. In addition, Figure 6 In (b), (c) and (d), we collected the LSV curves of Zn-based-CH in air and calculated the hydrogen peroxide selectivity and the number of transferred electrons in the catalytic process based on the disk-ring current. The results show that Zn-based-CH can achieve a selectivity of up to 90% in air, and the number of transferred electrons is also between 2-2.5, proving that Zn-based-CH has a high selectivity for 2-electron oxygen reduction to produce hydrogen peroxide.

[0084] In order to better quantify the hydrogen peroxide production capacity of Zn-based-CH, we used a liquid flow electrolysis cell for further testing. Figure 7 In (a), LSV test was performed in a liquid flow cell using air as the reaction gas. It was found that Zn-based-CH could achieve 250 mA cm within the test potential range. -2 The current density is further tested in the performance test ( Figure 7 In (b), we found that Zn-based-CH at 300 mA cm -2 The mass yield can reach 24.4 mol g cat -1 h -1 , the Faradaic efficiency is 87.2%, achieving efficient catalysis almost at the limiting diffusion current density of air electrolysis.

[0085] like Figure 8 As shown in (a), Zn-based-CH is in the range of 50-300 mA cm -2 The potential change diagram of the constant current test shows that at 300mAcm -2 Within the test time, the potential of Zn-based-CH hardly fluctuates. Figure 8 The UV absorbance curve of the colored hydrogen peroxide in the illustration (a) shows that the potential / product concentration increases with the increase of the current density gradient, which is consistent with Figure 7 The performance test results in (b) are consistent. Figure 8 (b) shows that Zn-based-CH can continue to work stably for more than 15 hours in the long-term stability test.

[0086] Fig. 9(a) shows the performance data of the electrode constructed by Zn-based-CH-1 in Example 2, which shows a good yield at the test current density of 300mAcm -2 The mass yield can reach 22.20 mol g cat -1 h -1 But at 150mAcm -2 When the Faraday efficiency is above 300mAcm, the Faraday efficiency decreases. -2 79.4% when RRDE test curve ( Fig. 9 (b)) and selectivity ( Fig. 9 (c)) and the number of transferred electrons ( Fig. 9 (d)) shows that the selectivity remains between 60% and 70% during the reaction, and the number of transferred electrons is between 2.5 and 2.75.

[0087] Fig.10 (a) shows the performance data of the electrode constructed by Zn-based-CH-3 in Example 3, which shows good yield at the test current density of 300mAcm -2 The mass yield can reach 22.08 mol g cat -1 h -1 But at 200mAcm -2 When the Faraday efficiency is above 300mAcm, the Faraday efficiency shows a significant downward trend. -2 78.9% when RRDE test curve ( Fig.10 (b)) and selectivity ( Fig.10 (c)) and the number of transferred electrons ( Fig.10 (d)) shows that the selectivity remains between 60% and 65% during the reaction, and the number of transferred electrons is close to 2.75.

[0088] Fig.11 (a) shows the performance data of the electrode constructed by Zn-based-CH-4 in Example 4, which shows good yield at the test current density of 300mAcm -2 The mass yield can reach 21.37 mol g cat -1 h -1 But at 100mA cm -2 When the Faraday efficiency is above 300 mA cm, the Faraday efficiency shows a significant downward trend. -2 76.4% when RRDE test curve ( Fig.11 (b)) and selectivity ( Fig.11 (c)) and the number of transferred electrons ( Fig.11 (d)) shows that the selectivity remains between 55% and 60% during the reaction, and the number of transferred electrons is close to 2.75-2.9.

[0089] Fig.12 (a) shows the performance data of the electrode constructed by Zn-based-CH-6 in Example 5, which shows good yield at the test current density of 300mA cm -2 The mass yield can reach 22.59 mol g cat -1 h -1 . Also at 150mA cm -2 When the Faraday efficiency is above 300 mA cm, the Faraday efficiency shows a clear downward trend. -2 When the Faraday efficiency is above 80%, it is 80.7%. RRDE test curve ( Fig.12 (b)) and selectivity ( Fig.12 (c)) and the number of transferred electrons ( Fig.12 (d)) shows that the selectivity remains between 50% and 58% during the reaction, and the number of transferred electrons is close to 2.75-3.

[0090] Fig.13 (a) shows the performance data of the electrode constructed by Zn-based-CH-8 in Example 6, which shows good yield at the test current density of 300mA cm -2 The mass yield can reach 19.96 mol g cat -1 h -1 At 100mA cm -2 When the Faraday efficiency is above 300 mA cm, the Faraday efficiency shows a significant downward trend. -2 The Faraday efficiency is only 71.3%. RRDE test curve ( Fig.13 (b)) and selectivity ( Fig.13 (b)) and the number of transferred electrons ( Fig.13 (b) shows that the selectivity remains at around 60% during the reaction and the number of transferred electrons is close to 2.75.

[0091] Fig.14 (a) shows the performance data of the electrode constructed by Zn-based-CH-10 in Example 7, which shows good yield at the test current density of 300mAcm -2 The mass yield can reach 22.96 mol g cat -1 h -1 . Also at 100mA cm-2 When the Faraday efficiency is above 300 mA cm, the Faraday efficiency decreases. -2 The Faraday efficiency remains above 80%, at 82.1%. RRDE test curve ( Fig.14 (b)) and selectivity ( Fig.14 (c)) and the number of transferred electrons ( Fig.14 (d)) shows that the selectivity during the reaction remains at around 60%-70%, and the number of transferred electrons is between 2.5-2.75.

[0092] Fig.15 (a) shows the performance data of the electrode constructed by Zn-based-NCH in Comparative Example 1. The yield is significantly lower than that of each electrode in the embodiment at the test current density, 300mAcm -2 The mass yield can be only 14.41 mol g at a current density of cat -1 h -1 At 100mAcm -2 When the Faraday efficiency is above 300mAcm, the Faraday efficiency decreases rapidly. -2 The Faraday efficiency is only 51.5%. RRDE test curve ( Fig.15 (b)) and selectivity ( Fig.15 (c)) and the number of transferred electrons ( Fig.15 (d)) shows that the selectivity during the reaction is only about 50%-60%, the number of transferred electrons is close to 3, and a strong four-electron oxygen reduction competition reaction occurs.

[0093] Fig.16 The figure shows the economic analysis of Zn-based-CH2O2 production in air and O2. (a) is the single factor analysis in oxygen, (b) is the cost ratio in oxygen, (c) is the single factor analysis in air, and (d) is the cost ratio in air. The data shows that by using air electrolysis, the oxygen cost accounting for 24.2% can be completely eliminated, and the electricity consumption accounting for a large proportion of the cost is completely acceptable in the context of clean energy power generation. Fig.16 (e) shows a comparative analysis of the cost of producing hydrogen peroxide by Zn-based-CH in air and oxygen and by Zn-based-NCH in air. The higher the current density, the lower the production cost of Zn-based-CH in air, and it is always lower than the production cost of Zn-based-CH in oxygen and Zn-based-NCH in air. Fig.16 (f) shows the cumulative net present value analysis of Zn-based-CH electrolysis in oxygen and air. The data show that with the increase of time, the profit gap between air electrolysis and oxygen electrolysis will gradually widen, and the advantage of air electrolysis will become more and more prominent.

[0094] Fig.17 The invention discloses the synthesis path of the zinc-based sub-nanocrystalline gas diffusion electrode material, explains the synthesis path and material characteristics of the zinc-based sub-nanocrystalline gas diffusion electrode material, and the in-situ synthesis of sub-nanocrystalline pores.

Claims

1. A method for preparing a zinc-based sub-nanocrystalline gas diffusion electrode material, characterized in that: The following steps are involved: Step 1: dissolving zinc acetate and glycerol in ethanol and stirring to form a uniform mixed solution; Step 2: placing the mixed solution obtained in step 1 in a sealed environment and heating it for a period of time; Step 3: calcining the material obtained in step 2 in an air atmosphere for a period of time to obtain a zinc-based gas diffusion electrode material.

2. The method according to claim 1, characterized in that In step 1, the ratio of zinc acetate, glycerol and ethanol is 1 g: 10-50 mL: 50-500 mL.

3. The method according to claim 1, characterized in that In step 2, the heating temperature in a closed environment is 60-200°C, and the reaction time is 5-40 h.

4. The method according to claim 1, wherein: In step 3, the calcination temperature is 200-600°C, and the calcination time is 0.5-4 h.

5. The zinc-based sub-nanocrystalline gas diffusion electrode material prepared by the method according to any one of claims 1 to 4, characterized in that: It has sub-nanometer crystalline pores.

6. Use of the zinc-based sub-nanocrystalline gas diffusion electrode material prepared by the method according to any one of claims 1 to 4 as a catalyst for rapid electrocatalytic air reduction to synthesize hydrogen peroxide.

7. A zinc-based sub-nanocrystalline pore gas diffusion electrode, characterized in that: The zinc-based sub-nanocrystalline porous gas diffusion electrode material prepared by the method described in any one of claims 1 to 4 is evenly dispersed with an adhesive Nafion and a conductive agent carbon black using isopropanol to prepare a catalyst dispersion, which is then dropped onto a carbon substrate and dried naturally; and then assembled with a polytetrafluoroethylene film to form a zinc-based sub-nanocrystalline porous gas diffusion electrode.

8. An air battery, characterized in that: It comprises the zinc-based sub-nanocrystalline pore gas diffusion electrode as claimed in claim 7.

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