An apparatus and method for electrochemically preparing an alkaline earth metal peroxide in situ

Abstract

The application discloses a device and a method for electrochemically preparing alkaline earth metal peroxides in situ. The electrochemical in-situ synthesis of alkaline earth metal peroxides can fully utilize the hydrogen peroxide generated on the cathode surface, and immediately convert it into alkaline earth metal peroxides which are difficult to decompose, easy to separate and high in purity. The electrochemical in-situ synthesis can realize a high hydrogen peroxide concentration on the surface in the case of a low yield, and reduce the energy consumption of the system. Through surface modification of a two-electron oxygen reduction electrode and process parameter control, the generated alkaline earth metal peroxides can quickly separate from the electrode surface, without affecting the reaction process of the electrode, and the stability of the electrode is greatly improved. The successful application of the synthesis system will promote the large-scale production and popular application of alkaline earth metal peroxides.

Description

Technical Field

[0001] This invention belongs to the field of materials and energy catalysis technology, specifically relating to an apparatus and method for electrochemical in-situ preparation of alkaline earth metal peroxides. Background Technology

[0002] Alkaline earth metal peroxides (AeMO2, M = Ca, Sr, Ba), as derivatives of hydrogen peroxide (H2O2), possess the basic characteristics of hydrogen peroxide—strong oxidizing properties and high reactive oxygen content. Furthermore, as a solid, AeMO2 offers several advantages over H2O2, including higher purity, less decomposition, easier storage, and easier transportation. It is widely used in agriculture, national defense, aquaculture, environmental protection, food processing, oxygenation, medical treatment, and daily life, yielding significant economic and social benefits. Currently, the synthesis of AeMO2 is highly dependent on H2O2, including the metal salt method, the metal oxide method, and the hydroxide method. These three methods share similar processes, involving mixing the corresponding metal salt, metal oxide, or hydroxide with a high concentration of H2O2 (typically 10–30%). However, high concentrations of H2O2 readily decompose, resulting in low synthesis efficiency. To improve the utilization rate of H2O2, stabilizers such as various ammonium salts, phosphates, or silicates are usually added to the reaction system. Although this improves the utilization rate of H2O2, it also increases the difficulty of purifying AeMO2 products, further limiting the large-scale production and widespread application of AeMO2.

[0003] Given the aforementioned cost issues, scientists began developing alternative air cathode methods for preparing AeMO2 in the 1980s. The air cathode method is an electrocatalytic in-situ preparation method for alkaline earth metal peroxides, characterized by low investment, low cost, low power consumption, and no pollution. This method uses electrochemically produced H2O2 to replace externally added high-concentration H2O2, thereby reducing costs. This method typically involves reducing molecular oxygen at the cathode in an alkaline electrolyte solution to obtain hydrogen peroxide. The reaction product (H2O2 + alkaline solution) is then further mixed with the corresponding alkaline earth metal hydroxide to prepare AeMO2. This electrocatalytic in-situ production method for AeMO2 reduces reaction costs, but still has many problems: (1) Due to the low selectivity and activity of the electrode catalyst, the system energy consumption is high; (2) H2O2 is easily decomposed in an alkaline environment, and diffused H2O2 is easily anoly oxidized and decomposed, resulting in low utilization in subsequent reaction processes; (3) The low H2O2 content in the reaction system leads to low H2O2 utilization. Therefore, the non-electrochemical in-situ synthesis of peroxides, namely the air cathode method, still cannot achieve a large-scale, low-cost, and highly universal method for preparing peroxides. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0006] One objective of this invention is to provide an apparatus for the electrochemical in-situ preparation of alkaline earth metal peroxides, which can achieve the advantages of high purity, high yield, low cost, and low energy consumption in the synthesis of AeMO2. It is expected to become the main method for the synthesis of AeMO2 and has great research prospects.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: an apparatus for electrochemical in-situ preparation of alkaline earth metal peroxides, comprising,

[0008] Electrolyte;

[0009] The anode comprises an electrode material that supports the OER reaction; and,

[0010] The cathode comprises an electrode material that supports a two-electron ORR reaction, a portion of which is placed in the electrolyte and the remainder of which is exposed to an oxygen source.

[0011] The electrolyte is composed of an alkaline solution and an alkaline earth metal hydroxide, wherein the concentration of the alkaline solution is 0.05–5 mol / L; and / or the concentration of the alkaline earth metal hydroxide is in the range of 0.001 mol / L to saturation.

[0012] Wherein, the current density applied to the cathode is ≥10 mA / cm -2 Under certain conditions, a two-electron oxygen reduction reaction is carried out.

[0013] In a preferred embodiment of the apparatus for the electrochemical in-situ preparation of alkaline earth metal peroxides of the present invention, the alkaline solution is sodium hydroxide and / or potassium hydroxide.

[0014] The alkaline earth metal hydroxide is calcium hydroxide and / or strontium hydroxide and / or barium hydroxide.

[0015] In a preferred embodiment of the apparatus for the electrochemical in-situ preparation of alkaline earth metal peroxides according to the present invention, the cathode is a two-electron oxygen reduction catalytic electrode and / or an electrode to which a two-electron powder catalyst is attached. In another preferred embodiment of the apparatus for the electrochemical in-situ preparation of alkaline earth metal peroxides according to the present invention, the electrode to which the two-electron powder catalyst is attached is prepared by dissolving 3 mg of two-electron powder catalyst in 1 mL of ethanol, adding 20 μL of Nafion, and uniformly spraying the solution onto a current collector (a hydrophobic electrode or an electrode with a gas diffusion layer).

[0016] In a preferred embodiment of the apparatus for electrochemical in-situ preparation of alkaline earth metal peroxides according to the present invention, the cathode has a surface modification layer, which is used to reduce the surface energy of the cathode surface.

[0017] The surface modification layer material is a fluorinated polymer material, including one or more of polytetrafluoroethylene, polyvinylidene fluoride, polychlorotrifluoroethylene, and polyvinyl fluoride.

[0018] As a preferred embodiment of the apparatus for electrochemical in-situ preparation of alkaline earth metal peroxides of the present invention, the method for preparing the surface modification layer includes immersing a two-electron oxygen reduction reaction electrode in a uniformly dispersed solution of the surface modification layer material, then removing it, drying it, and sintering it to obtain a cathode for the electrochemical reaction.

[0019] In a preferred embodiment of the apparatus for electrochemical in-situ preparation of alkaline earth metal peroxides according to the present invention, the surface modification layer material is loaded at a concentration of 0–25 wt% on the cathode surface.

[0020] As a preferred embodiment of the apparatus for the electrochemical in-situ preparation of alkaline earth metal peroxides of the present invention, it further includes an auxiliary device connected to the cathode, the auxiliary device being used to generate an inertial force and / or centrifugal force away from the cathode body on the cathode placed in the electrolyte.

[0021] In a preferred embodiment of the apparatus for electrochemical in-situ preparation of alkaline earth metal peroxides according to the present invention, the anode is an electrode capable of oxygen evolution, including one of a graphite electrode, a diamond electrode, and a ruthenium-iridium-titanium electrode.

[0022] As a preferred embodiment of the apparatus for the electrochemical in-situ preparation of alkaline earth metal peroxides of the present invention, it further includes an electrolyte circulation device, wherein the circulation rate of the electrolyte by the electrolyte circulation device is 5 to 50 mL / min.

[0023] Another object of the present invention is to provide a method for electrochemical in-situ preparation of alkaline earth metal peroxides, comprising,

[0024] The two-electron oxygen reduction reaction was carried out using the electrochemical in-situ preparation apparatus for alkaline earth metal peroxides as described above, and the generated alkaline earth metal peroxides detached from the electrode surface and entered the electrolyte.

[0025] Alkaline earth metal peroxides were separated from the electrolyte, and then filtered, separated, washed, and dried to obtain high-purity alkaline earth metal peroxides.

[0026] In a preferred embodiment of the electrochemical in-situ preparation method of alkaline earth metal peroxides of the present invention, the cleaning solution is a mixture of ethanol and water in any proportion; the drying is vacuum drying and / or freeze drying, and the drying temperature is -30 to 80°C.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] This invention discloses a universal method for the efficient in-situ electrochemical preparation of alkaline earth metal peroxides. In this method, a high concentration of H₂O₂ generated near the electrode reacts with alkaline earth metal particles (AeM₂). 2+ This method avoids problems such as anodic decomposition of H2O2 and self-decomposition in alkaline systems, enabling efficient synthesis of AeMO2 with high purity, high yield, low cost, and low energy consumption. By modifying the surface of the two-electron oxygen reduction electrode and controlling the electrode's operating state, electrolyte concentration, and reaction current density, this invention achieves rapid desorption of AeMO2 from the electrode surface without affecting further electrochemical synthesis. This method and strategy represent a significant breakthrough for the large-scale preparation and application of AeMO2. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0030] Figure 1 This is a schematic diagram of the device of the present invention.

[0031] Figure 2 The X-ray diffraction pattern of SrO2 prepared in Example 1 of this invention is shown.

[0032] Figure 3 The thermogravimetric curve of SrO2 prepared in Example 1 of this invention.

[0033] Figure 4 This refers to the overall reaction efficiency of the system in Embodiment 1 of the present invention.

[0034] Figure 5This is the stability curve of the solution in 0.4 mol / L NaOH + 0.01 mol / L Sr(OH)2 in Example 1 of the present invention.

[0035] Figure 6 The results are the Faraday efficiency test results after 6 hours of reaction in Examples 1-3 of this invention.

[0036] Figure 7 These are the performance curves of different modification methods in Examples 4 to 6 of the present invention.

[0037] Figure 8 The current density in this embodiment of the invention refers to the current density after the electrode surface has been modified with different concentrations of materials.

[0038] Figure 9 The voltage fluctuation in the embodiments of the present invention is determined by whether the electrode surface is modified with different concentrations of materials.

[0039] Figure 10 The working states of the electrodes in embodiments 9 and 10 of the present invention are shown.

[0040] Figure 11 The results are the Faraday efficiency test results after 6 hours of reaction in Examples 9 and 10 of this invention.

[0041] Figure 12 The results are the Faraday efficiency test results after 6 hours of reaction in Examples 11-12 of this invention.

[0042] Figure 13 The X-ray diffraction pattern of CaO2 prepared in Example 14 of this invention is shown.

[0043] Figure 14 This is the stability curve in 0.4 mol / L NaOH + 0.01 mol / L Ca(OH)2 solution in Example 14 of the present invention.

[0044] Figure 15 The X-ray diffraction pattern of BaO2 prepared in Example 15 of this invention.

[0045] Figure 16 This is the stability curve in 0.4 mol / L NaOH + 0.01 mol / L Ba(OH)2 solution in Example 15 of the present invention.

[0046] Figure 17 These are the stability curves of Comparative Examples 1 and 2 of the present invention under the corresponding reaction conditions;

[0047] Figure 18 In Comparative Example 3 of this invention, at 5 mA / cm -2 Stability curves under certain conditions.

[0048] Figure 19The precipitate collected in Example 16 of this invention. Detailed Implementation

[0049] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0050] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0051] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0052] Unless otherwise specified, all raw materials used in the examples are commercially available.

[0053] This invention utilizes the high concentration of H2O2 generated on the surface of a highly efficient two-electron oxygen reduction catalytic electrode to react with AeM in the reaction system. 2+ Immediately, it combines and transforms into AeMO2, making full use of the H2O2 generated at the oxygen reduction cathode. Furthermore, it was found that by modifying the electrode surface microstructure, the oxygen pathway during oxygen reduction is increased, improving electrode reaction efficiency while simultaneously reducing the surface energy of the electrode, enabling rapid desorption of the generated AeMO2 without affecting subsequent synthesis. By optimizing the reaction conditions affecting the rate of H2O2 synthesis at the cathode and the rate of peroxide formation, high-efficiency, high-yield, and low-energy-consumption synthesis of AeMO2 is achieved.

[0054] This invention uses a highly efficient two-electron oxygen reduction catalyst material with surface modification as an electrochemical reaction cathode (reaction equation 1), and prepares AeMO2 in situ in the electrolyte NaOH + AeM(OH)2 via electrochemical reaction (reaction equation 2).

[0055] The above reaction equation is:

[0056] O2 + H2O + 2e - →HO2 - +OH - (Reaction Equation 1)

[0057] HO2 - +AeM 2+ +OH -→AeMO2↓+H2O (Reaction Equation 2)

[0058] Example 1

[0059] like Figure 1 As shown, this is an apparatus for electrochemical in-situ preparation of alkaline earth metal peroxides provided in this embodiment 1, including an electrolytic cell 400, an electrolyte 100, an anode 200 and a cathode 300;

[0060] The anode 200 and cathode 300 are placed in the electrolyte 100 in the electrolytic cell 400, wherein the cathode 300 floats on the surface of the electrolyte 100, the lower half of the cathode 300 is immersed in the electrolyte 100, and the upper half of the cathode 300 is exposed to high-purity oxygen above the electrolytic cell 400.

[0061] To maintain the concentration of alkaline earth metal ions in the electrolyte 100, the entire device also includes an electrolyte circulation device 500, comprising a reaction solution tank 501 and a recovery tank 502. The reaction solution tank 501 pumps the electrolyte 100 into the electrolytic cell 400. The recovery tank 502 recovers the reacted solution from the electrolytic cell 400, replenishes the recovery tank 502 with alkaline earth metal ion solution, and then pumps it back to the reaction solution tank 501. Overall, the electrolyte 100 in the electrolytic cell 400 is maintained as a mixed solution of 0.01 mol / L Sr(OH)2 and 0.4 mol / L NaOH.

[0062] Based on the apparatus provided in Example 1, the specific preparation method is as follows:

[0063] (1) Mix 0.01 mol / L Sr(OH)2 and 0.4 mol / L NaOH evenly to serve as the electrolyte for the electrochemical two-electron oxygen reduction reaction;

[0064] (2) The two-electron oxygen reduction reaction electrode (Ni-OC electrode) was placed in a uniform dispersion of 10wt% PTFE and soaked for 5 minutes. After that, it was taken out and dried in an oven at 60°C. Finally, it was placed in a fluoropolymer furnace and treated at 350°C for 30 minutes to serve as the cathode for the electrochemical reaction. The electrode was in a floating state.

[0065] The two-electron oxygen reduction reaction electrode used in this embodiment is a Ni-OC electrode, which has good reaction performance and has been synthesized and used in existing literature. The preparation method of this electrode is as follows: nickel nitrate and urea are dissolved in methanol to form a homogeneous solution, which is then placed in a reaction vessel at 120°C for 12 hours; after drying, it is placed on 2g of polyethylene oxide and carbonized at 800°C for 3 hours under a nitrogen atmosphere, resulting in an electrode with an area of ​​approximately 5 cm². 2 The Ni-OC electrode is capable of floating on the surface of the electrolyte.

[0066] (3) Place the cathode from (2) in the electrolyte from (1), using a graphite electrode as the anode for the electrochemical reaction, and set the current density to 30 mA / cm². 2 Electrochemical in-situ synthesis of SrO2 was carried out at an electrolyte circulation rate of 15 mL / min.

[0067] (4) Wash the precipitate obtained in step (3) with ethanol:water = 1:1 until neutral, and collect the precipitate by centrifugation;

[0068] (5) Dry the precipitate from step (4), place it in a vacuum drying oven, set the drying temperature to 80°C, collect it after drying, and SrO2 is obtained.

[0069] Figure 2 The X-ray diffraction pattern of SrO2 prepared in Example 1 shows that there are no other impurities besides SrO2, and the product has extremely high purity.

[0070] Figure 3 The thermogravimetric curve of SrO2 prepared in Example 1 shows two endothermic peaks, namely the dehydration and decomposition of SrO2. No decomposition of other substances was observed in the thermogravimetric curve, which proves that the product has extremely high purity.

[0071] Figure 4 To determine the overall reaction efficiency of SrO2 synthesis in Example 1, the overall reaction efficiency was calculated using the thermogravimetric curve of the collected precipitate. The specific calculation process is as follows:

[0072] 2SrO2=2SrO+O2↑

[0073] FE%=(it / 2ZF) / (2*m*ΔTG / Mo2)*100%

[0074] Where i is the reaction current (A), t is the reaction time, Z is the amount of charge transferred in the reaction, F is the Faraday constant, m is the mass of precipitate collected at the corresponding reaction time, ΔTG is the weight loss due to SrO2 decomposition in the thermogravimetric curve, and Mo2 is the molecular weight of O2. The energy utilization rate is over 95%, reducing H2O2 waste and achieving low-energy synthesis of SrO2.

[0075] Figure 5 The figure shows the stability curve of Example 1 under long-term operation in a 0.4 mol / L NaOH + 0.01 mol / L Sr(OH)2 solution. As can be seen from the figure, during the long-term electrochemical synthesis of SrO2, the voltage did not fluctuate significantly, and the stable operation time reached 1100 h.

[0076] Example 2

[0077] The difference from Example 1 is that in step (1), 0.001 mol Sr(OH)2 and 0.5 mol / L NaOH are mixed evenly, and the other steps are the same as in Example 1.

[0078] Example 3

[0079] The difference from Example 1 is that in step (1), saturated Sr(OH)2 and 5 mol / L NaOH are mixed evenly, while the other steps are the same as in Example 1.

[0080] like Figure 6 As shown, in Examples 1-3 of this invention, alkaline earth metal peroxides can be generated with high efficiency, and the precipitates do not adhere to the electrode surface. Specifically, the overall reaction efficiencies of Examples 1, 2, and 3 are 99.42%, 98.91%, and 98.75%, respectively. This is due to the relationship between the reaction current density and the concentration of alkaline earth metal ions in the solution; under the above reaction conditions, extremely high overall reaction rates can be achieved.

[0081] Example 4

[0082] The difference from Example 1 is that in step (1), PTFE is replaced with PVDE, while the other steps are the same as in Example 1.

[0083] Example 5

[0084] The difference from Example 1 is that in step (1), PTFE is replaced with PCTFE, while the other steps are the same as in Example 1.

[0085] Example 6

[0086] The difference from Example 1 is that in step (1), PTFE is replaced with PVF, while the other steps are the same as in Example 1.

[0087] like Figure 7 As shown in Examples 4, 5, and 6, various F-containing polymer materials can increase current density by enhancing hydrophobicity, and all can achieve high reaction current densities under the reaction system conditions. Furthermore, modification can increase current density, reduce the surface energy of the electrode surface, and prevent precipitation from adhering to the electrode surface.

[0088] Example 7

[0089] The difference from Example 1 is that in step (2), the PTFE concentration is changed to 0-30 wt%, while the other steps are the same as in Example 1.

[0090] Figure 8The figure shows the current density of the electrode surface modified with different PTFE in Example 7. As can be seen from the figure, the current density of the electrode without surface modification is slightly lower than that of the electrode with surface modification. Even with a reduction in the concentration of the corresponding alkali metal ions in the electrolyte, the precipitate can still be desorbed immediately from the electrode surface, allowing the entire reaction to operate stably for a long time. After PTFE surface modification, the current density of two-electron oxygen reduction is increased. Due to the increase in electrode density, the precipitate is more easily detached from the electrode surface. Furthermore, the presence of PTFE increases the surface energy of the electrode surface, reduces the adhesion force with the solution, and reduces the nucleation sites on the electrode, making it easier to desorb the precipitate.

[0091] Figure 9 The figures for Example 7 show the initial voltage and voltage changes after one hour of reaction for the electrode surfaces modified with different PTFEs. During the reaction, a "loose layer" precipitate forms on the surface of the unmodified electrode, causing a slight voltage drop. However, as the reaction progresses, the precipitate automatically detaches without affecting the subsequent synthesis process. The PTFE-modified electrode exhibits faster immediate desorption of the precipitate from the electrode surface as the reaction proceeds, resulting in reduced voltage fluctuations and the precipitate having no impact on the electrode reaction process.

[0092] Example 9

[0093] The difference from Example 1 is that in step (2), the electrode working state is changed from floating to rotating, such as... Figure 10 As shown in (A), the other steps are the same as in Example 1.

[0094] It should be noted that, as Figure 10 In (A), a disc-shaped cathode 300 is erected with its axis parallel to the horizontal plane and its lower end immersed in the electrolyte 100. A rotator 600 is connected to the center of the cathode 300. While the two-electron oxygen reduction reaction is taking place, the rotator 600 keeps the cathode 300 rotating at a speed of 100 revolutions per minute.

[0095] Example 10

[0096] The difference from Example 1 is that in step (2), the electrode working state is changed from floating to floating-rotating, such as... Figure 10 As shown in (B), the other steps are the same as in Example 1.

[0097] It should be noted that, as Figure 10 In (B), the disc-shaped cathode 300 remains in a horizontal floating state, and a rotator 600 is connected to the center of the cathode 300. While the two-electron oxygen reduction reaction is taking place, the rotator 600 keeps the cathode 300 rotating at a speed of 100 revolutions per minute.

[0098] like Figure 11 As shown, the overall reaction efficiency of different electrode working states in Examples 9 and 10 under the reaction system can reach 98.48% and 99.13%, respectively. By utilizing gravity and centrifugal force, the desorption of precipitates on the electrode surface can be accelerated more quickly, and the mass transfer of corresponding ions in the solution can be accelerated without affecting the current density of the reaction, thus achieving a high overall reaction efficiency.

[0099] Example 11

[0100] The difference from Example 1 is that in step (3), the current density is set to 10 mA / cm². 2 The electrolyte circulation rate was 5 mL / min; all other steps were the same as in Example 1.

[0101] Example 12

[0102] The difference from Example 1 is that in step (3), the current density is set to 50 mA / cm². 2 The electrolyte circulation rate was 30 mL / min; all other steps were the same as in Example 1.

[0103] like Figure 12 As shown, the overall reaction efficiency in the reaction system under different current densities in Examples 11 and 12 can reach 98.15% and 99.32%, respectively. Within the corresponding range of this current density, not only is it ensured that the generated precipitate can be rapidly desorbed on the electrode surface without affecting the stability of the reaction, but the overall efficiency of the reaction is also guaranteed.

[0104] Example 13

[0105] The difference from Example 1 is that in step (5), vacuum drying is replaced with freeze drying and the drying temperature is set to -30°C; the other steps are the same as in Example 1.

[0106] The drying methods of the products in Example 13 are all applicable to the drying of alkaline earth metal peroxides, have no effect on the morphology of the products, and the corresponding performance and effects are not substantially different from those in Example 1, with comparable overall reaction efficiency.

[0107] Example 14

[0108] The only difference between this embodiment and Embodiment 1 is that in step (1), Sr(OH)2 is replaced with Ca(OH)2; all other steps are the same as in Embodiment 1.

[0109] Figure 13 The X-ray diffraction pattern of CaO2 prepared in Example 14 shows that the product, which contains no impurities other than CaO2, has extremely high purity.

[0110] Figure 14This is the stability curve of Example 14 under long-term operation in a 0.4 mol / L NaOH + 0.01 mol / L Ca(OH)2 solution. As shown in the figure, during the long-term electrochemical synthesis of CaO2, the voltage did not fluctuate significantly, indicating that the electrochemical in-situ synthesis of CaO2 could be stably carried out.

[0111] Example 15

[0112] The only difference between this embodiment and Embodiment 1 is that in step (1), Sr(OH)2 is replaced with Ba(OH)2; all other steps are the same as in Embodiment 1.

[0113] Figure 15 The figure shows the X-ray diffraction pattern of BaO2 prepared in Example 15. As can be seen from the figure, BaO2 was successfully prepared by the electrochemical in-situ synthesis method.

[0114] Figure 16 This is the stability curve of Example 15 under long-term operation in a 0.4 mol / L NaOH + 0.01 mol / L Ba(OH)2 solution. As shown in the figure, during the long-term electrochemical synthesis of BaO2, the voltage did not fluctuate significantly, indicating that the electrochemical in-situ synthesis of BaO2 could be carried out stably.

[0115] Comparative Example 1

[0116] The only difference between this comparative example and Example 1 is that the 0.01 mol / L Sr(OH)2 and 0.4 mol / L NaOH are replaced with saturated Sr(OH)2.

[0117] Comparative Example 2

[0118] The only difference between this comparative example and Example 1 is that in step (2), the PTFE treatment is not performed.

[0119] Figure 17 The stability curves (V = 0.2V vs. RHE) of SrO2 synthesized in situ in electrochemically in Comparative Examples 1 and 2 with saturated Sr(OH)2 electrolyte and electrodes not modified with PTFE are shown.

[0120] It can be seen that in Comparative Example 1, due to Sr 2+ Excessive concentration and low current density in the reaction system cause SrO2 generated during the electrochemical in-situ synthesis to adhere to the electrode surface, resulting in decreased electrode stability and making long-term stable synthesis impossible.

[0121] In Comparative Example 2, since the electrode was not modified, there were fewer oxygen pathways, slower electron transport, and higher surface energy on the electrode surface during the two-electron oxygen reduction process. This caused the electrochemically synthesized SrO2 to adhere to the electrode surface, blocking the active sites on the electrode surface. As a result, the reaction current density gradually decreased, leading to the failure of the electrochemical synthesis of SrO2.

[0122] Comparative Example 3

[0123] The only difference between this comparative example and Example 1 is that in step (3), the current density is changed to 5 mA / cm². -2 .

[0124] In this comparative example, due to the low current density, the H2O2 generation rate is low, and SrO2 tends to form on the electrode surface during particle diffusion, which in turn blocks the active sites in the reaction process, leading to the failure of the long-term electrochemical synthesis process.

[0125] Figure 18 For Comparative Example 3, at a low current density (5 mA / cm²) -2 The stability curves of H2O2 show that at low current densities, the synthesis efficiency of H2O2 is low, causing a large amount of SrO2 to adhere to the electrode surface, resulting in the failure of reactive active sites and thus the failure of the electrochemical synthesis of SrO2.

[0126] Example 16

[0127] To verify the practicality of this invention, a kilogram-scale scale-up experiment was also conducted. Based on Example 1, the specific implementation steps for kilogram-scale preparation are as follows:

[0128] (1) Mix 0.01 mol / L Sr(OH)2 and 0.4 mol / L NaOH evenly to serve as the electrolyte for the electrochemical two-electron oxygen reduction reaction;

[0129] (2) Take 10cm 2 The two-electron oxygen reduction reaction electrode or catalyst, after being treated with 10wt% PTFE, serves as the cathode for the electrochemical reaction, and the electrode operates in a floating state.

[0130] (3) Place the electrode from (2) in (1) and set the current density to 50 mA / cm². 2 The electrolyte circulation rate was 30 mL / min, and SrO2 was synthesized in situ by electrochemical reaction for 900 h.

[0131] (4) Wash the precipitate obtained in step (3) with ethanol:water = 1:1 until neutral, and collect the precipitate by centrifugation;

[0132] (5) Dry the precipitate from step (4), place it in a vacuum drying oven, set the drying temperature to 80°C, collect it after drying, and SrO2 is obtained.

[0133] The prepared SrO2 is as follows Figure 19 As shown, the present invention has successfully achieved large-scale preparation at the kilogram level.

[0134] By employing the technical solution of this invention, after surface modification of the two-electron oxygen reduction catalytic electrode, the electrode has a low surface energy surface. This not only ensures the gas passage during the oxygen reduction reaction and increases the current density required for the reaction, but also accelerates the desorption of precipitates on the electrode surface. It has no effect on the electrochemical reaction on the electrode surface, and can successfully achieve long-term, high-stability synthesis of AeMO2.

[0135] The technical solution of this invention successfully solves the problems of H2O2 being easily decomposed by anodic oxidation during electrolysis and its self-decomposition in alkaline systems, thus avoiding the decomposition of H2O2 in the reaction system, improving the utilization rate of H2O2, and reducing the system's reaction energy consumption. It also utilizes the high concentration of H2O2 on the electrode surface, converting it in real time into AeMO2.

[0136] By employing the technical solution of this invention, the production of H2O2 and the synthesis of AeMO2 are successfully combined. By reducing the cost of the key raw material H2O2, the yield, production rate and utilization rate of H2O2 are increased, thereby reducing the energy consumption and production cost of the final product AeMO2.

[0137] The technical solution of this invention can successfully prepare high-purity AeMO2, with an overall system utilization rate of >= 95%, achieving low-energy synthesis of AeMO2. Furthermore, no additional substances other than alkali and alkaline earth metal hydroxides need to be added to the reaction system, ensuring the high purity of the synthesized AeMO2.

[0138] The technical solution of this invention has universal applicability to the preparation of AeMO2 (CaO2 / SrO2 / BaO2). The successful realization of low-cost, high-efficiency, and high-purity preparation of AeMO2 represents a significant breakthrough for the large-scale preparation and application of AeMO2.

[0139] This invention successfully achieved long-term stable in-situ electrochemical synthesis of alkaline earth metal peroxides by modifying the electrode surface and controlling different process parameters. The synthesized products exhibit extremely high purity, with an overall reaction efficiency as high as 95%. This demonstrates the broad applicability of the electrochemical in-situ synthesis of alkaline earth metal peroxides involved in this invention, successfully achieving low-energy consumption, high-purity, and high-yield synthesis. The novel synthesis method designed in this invention will undoubtedly greatly contribute to and promote the large-scale application of alkaline earth metal peroxides.

[0140] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An apparatus for the electrochemical in-situ preparation of alkaline earth metal peroxides, characterized in that: include, Electrolyte; The anode contains the electrode material that supports the OER reaction; as well as, The cathode is a two-electron oxygen reduction catalytic electrode and / or an electrode to which a two-electron powder catalyst is attached, and has a surface modification layer. The surface modification layer is used to reduce the surface energy of the cathode surface. The surface modification layer material is a fluorine-containing polymer material, including one or more of polytetrafluoroethylene, polyvinylidene fluoride, polychlorotrifluoroethylene, and polyvinyl fluoride. The cathode floats on the surface of the electrolyte, with the lower half of the cathode immersed in the electrolyte and the upper half of the cathode exposed to high-purity oxygen above the electrolytic cell. An auxiliary device connected to the cathode, the auxiliary device being used to generate an inertial force and / or centrifugal force away from the cathode body on the cathode placed in the electrolyte; The electrolyte is composed of an alkaline solution and an alkaline earth metal hydroxide, wherein the concentration of the alkaline solution is 0.05~5 mol / L; and / or the concentration of the alkaline earth metal hydroxide is in the range of 0.001 mol / L to saturation. Wherein, the current density applied to the cathode is ≥10 mA / cm -2 Under certain conditions, a two-electron oxygen reduction reaction is carried out.

2. The apparatus for electrochemical in-situ preparation of alkaline earth metal peroxides as described in claim 1, characterized in that: The alkaline solution is sodium hydroxide and / or potassium hydroxide; The alkaline earth metal hydroxide is calcium hydroxide and / or strontium hydroxide and / or barium hydroxide.

3. The apparatus for electrochemical in-situ preparation of alkaline earth metal peroxides as described in claim 1, characterized in that: The anode is an electrode capable of oxygen evolution, including one of a graphite electrode, a diamond electrode, and a ruthenium-iridium-titanium electrode.

4. The apparatus for electrochemical in-situ preparation of alkaline earth metal peroxides as described in claim 1, characterized in that: It also includes an electrolyte circulation device, wherein the electrolyte circulation rate of the electrolyte is 5~50 mL / min.

5. A method for electrochemical in-situ preparation of alkaline earth metal peroxides, characterized in that: include, The apparatus for electrochemical in-situ preparation of alkaline earth metal peroxides as described in any one of claims 1 to 4 is used to carry out a two-electron oxygen reduction reaction, and the generated alkaline earth metal peroxides detach from the electrode surface and enter the electrolyte. Alkaline earth metal peroxides were separated from the electrolyte, and then filtered, separated, washed, and dried to obtain high-purity alkaline earth metal peroxides.

6. The method for electrochemical in-situ preparation of alkaline earth metal peroxides as described in claim 5, characterized in that: The cleaning solution is a mixture of ethanol and water in any proportion; the drying is vacuum drying and / or freeze drying at a temperature of -30 to 80°C.

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