Application of non-oxygen-evolving metal oxide MoO3 in electrocatalytic water oxidation to produce hydrogen peroxide

Abstract

The present invention discloses the use of a non-oxygen-evolving metal oxide MoO3 in water oxidation to produce hydrogen peroxide. Based on the d-band theory, with the goal of regulating the two competing reactions of hydrogen peroxide evolution and oxygen evolution in the electrocatalytic water splitting anode reaction, metal Mo without d-orbital active centers was selected from the perspectives of reaction thermodynamics and electronic structure. MoO3 material was synthesized and prepared into an anode for electrocatalytic water splitting by using an ethyl cellulose film formation method. The electrochemical performance of the anode made of MoO3 material was characterized in CH3COONa electrolyte, and the hydrogen peroxide produced by water oxidation was quantitatively determined. The results show that the MoO3 material has a good electrochemical performance in non-HCO3 ‑ The system achieves a Faradaic efficiency of 35% for water oxidation to produce hydrogen peroxide in the CH3COONa electrolyte.

Description

Technical Field

[0001] The invention belongs to the technical field of electrocatalytic water oxidation materials and relates to use of a non-oxygen-evolving metal oxide MoO3 in water oxidation to produce hydrogen peroxide. Background Art

[0002] Hydrogen peroxide, an important green inorganic chemical product, is widely used in numerous fields, including medicine, food, environmental protection, and chemical engineering. Currently, large-scale industrial production of hydrogen peroxide relies primarily on anthraquinone autoxidation, a method that is energy-intensive and environmentally unfriendly. Furthermore, the high-concentration hydrogen peroxide produced poses significant safety risks during transportation. While direct synthesis using hydrogen (H₂) and oxygen (O₂) offers an alternative, the mixture carries an explosion risk, and the precious metal catalysts required for direct synthesis hinder its practical application. While oxygen reduction offers a safer and more environmentally friendly production pathway, the high cost of oxygen reduction catalysts and the need for continuous oxygen flow during production also pose significant limitations. In contrast, electrochemical water oxidation to synthesize hydrogen peroxide is an in-situ method that avoids the explosion risk associated with direct synthesis using H₂ and O₂, nor does it require the constant flow of oxygen, making it simpler and more practical. Furthermore, the production of hydrogen peroxide from water oxidation is environmentally friendly and pollution-free, and abundant water resources also offer the potential for large-scale water oxidation production in the future.

[0003] There are two main competing reactions in the electrocatalytic water oxidation reaction: oxygen evolution reaction and hydrogen peroxide production reaction. The oxygen evolution reaction has a lower redox potential than the hydrogen peroxide production and is more likely to occur during electrocatalytic water decomposition. Therefore, to achieve efficient water oxidation to produce hydrogen peroxide, it is necessary to suppress oxygen evolution as much as possible and improve the selectivity of water oxidation to produce hydrogen peroxide. At present, researchers have predicted the selectivity of water oxidation to produce hydrogen peroxide of some materials based on density functional theory calculations and computational hydrogen electrode models, and have studied the performance of these materials through experiments, and developed a few more efficient catalytic materials for water oxidation to produce hydrogen peroxide, including BiVO4 and CaSnO3. However, the stability of BiVO4 material is poor, and the CaSnO3 material is toxic, making them difficult to use in practice. Therefore, in the research on water oxidation to produce hydrogen peroxide, there is a large gap in the development of efficient and stable catalysts, and the development of catalytic materials for efficient water oxidation to produce hydrogen peroxide remains the top priority of this research. At the same time, water oxidation to produce hydrogen peroxide is mostly in HCO3 - This is because HCO3 - The system can promote the production of hydrogen peroxide to a certain extent, but according to LeChatelier's principle, HCO3 - The system will inhibit the generation of high concentration H2O2. When H2O2 reaches a certain concentration, hydrogen peroxide will accelerate its self-decomposition and inhibit the two-electron water oxidation to produce H2O2. This means that in HCO3- The two-electron water oxidation to produce H2O2 will eventually reach a concentration threshold, making it difficult to achieve continuous accumulation of H2O2. This limitation will greatly restrict the application of electrocatalytic water oxidation to produce H2O2. Finding an electrolyte that can efficiently produce and stably store H2O2 is also one of the important research areas of electrocatalytic water oxidation to produce H2O2. Summary of the Invention

[0004] The present invention aims to provide a method for using MoO3 as a catalytic material for electrocatalytic water oxidation to produce hydrogen peroxide.

[0005] The technical solution for achieving the purpose of the present invention is as follows: a use of MoO3 in electrocatalytic water oxidation to produce hydrogen peroxide.

[0006] Preferably, MoO3 is coated on the FTO surface using an ethyl cellulose film-forming method as a catalytic material for water oxidation to produce hydrogen peroxide.

[0007] Specifically, the mass ratio of MoO3 to ethyl cellulose is 1:2.5.

[0008] Preferably, the electrocatalytic reaction system is a CH3COONa solution.

[0009] Compared with the prior art, the present invention has the following advantages:

[0010] Based on the d-band theory, the present invention selects and synthesizes MoO3 material from the perspective of thermodynamics and electronic structure, and prepares it into an anode for electrocatalytic water decomposition by ethyl cellulose film formation method, and - The performance of MoO3 in electrocatalytic water oxidation in the CH3COONa electrolyte of the system was studied. MoO3 achieved a Faradaic efficiency of 35% in the CH3COONa system for electrocatalytic water oxidation to produce hydrogen peroxide.

[0011] It should be understood that all combinations of the aforementioned concepts and the additional concepts described in more detail below, as long as such concepts are not mutually inconsistent, can be considered as part of the inventive subject matter of the present application. In addition, all combinations of the claimed subject matter are considered as part of the inventive subject matter of the present application.

[0012] The foregoing and other aspects, embodiments, and features of the present invention will be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the present invention, such as features and / or beneficial effects of the exemplary embodiments, will become apparent from the following description or through practice of specific embodiments according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Schematic diagram of the idea of ​​selecting materials for the present invention.

[0014] Figure 2 This is the XRD pattern of MoO3 synthesized in the present invention.

[0015] Figure 3 This is the SEM image of MoO3 synthesized in the present invention.

[0016] Figure 4 These are the electrochemical performance diagrams of MoO3 synthesized in the present invention in CH3COONa electrolyte with pH = 9.6, where Figure (a) is the LSV diagram; Figure (b) is the overpotential diagram; and Figure (c) is the Tafel slope diagram.

[0017] Figure 5 The selectivity diagram of water oxidation to hydrogen peroxide produced by MoO3 synthesized in the present invention at different potentials in CH3COONa electrolyte with pH=9.6, wherein Figure (a) is a concentration diagram of hydrogen peroxide produced by MoO3 electrocatalytic water oxidation at different potentials; Figure (b) is a Faraday efficiency diagram of hydrogen peroxide produced by MoO3 electrocatalytic water oxidation at different potentials.

[0018] Figure 6 Figure 3 shows the performance of water oxidation to produce hydrogen peroxide by the MoO3 of the present invention at different potentials in CH3COONa electrolytes with different pH values ​​at an optimal potential of 3.2 V vs. RHE potential, where Figure (a) shows the concentration of produced hydrogen peroxide; Figure (b) shows the Faraday efficiency of produced hydrogen peroxide.

[0019] Figure 7 The performance of the MoO3 synthesized in the present invention and other selected synthesized Nb, W, Ta, Zr, and Ti oxides in the electrocatalytic oxidation of water to produce hydrogen peroxide in a CH3COONa electrolyte with a pH of 9.6 at an optimal potential of 3.2 V vs. RHE potential is compared. Figure (a) shows the concentration comparison of the hydrogen peroxide produced by the two; Figure (b) shows the Faraday efficiency comparison of the hydrogen peroxide production by the two.

[0020] Figure 8 This is a comparison of the electrocatalytic water oxidation selectivity of MoO3 synthesized by the present invention without d-orbital active centers and metal oxides containing d-orbital active centers, wherein Figure (a) is a comparison of the concentrations of hydrogen peroxide produced by the electrocatalytic water oxidation of the two at the optimal potential; Figure (b) is a comparison of the Faraday efficiencies of hydrogen peroxide produced by the electrocatalytic water oxidation of the two at the optimal potential. DETAILED DESCRIPTION

[0021] In order to better understand the technical content of the present invention, specific embodiments are given and described below with reference to the accompanying drawings.

[0022] Various aspects of the present invention are described herein with reference to the accompanying drawings, in which a number of illustrative embodiments are shown. The embodiments of the present invention are not necessarily intended to encompass all aspects of the present invention. It should be understood that the various concepts and embodiments described above, as well as those described in more detail below, may be implemented in any of a number of ways, as the concepts and embodiments disclosed herein are not limited to any particular implementation. In addition, some aspects disclosed herein may be used alone or in any appropriate combination with other aspects disclosed herein.

[0023] like Figure 1 As shown, d-band theory is closely related to the oxygen evolution reaction (OER). Many studies have shown that transition metals with d-orbital active centers are more susceptible to the OER. Consequently, common transition metals including V, Cr, Mn, Fe, Co, Ni, and Cu, as well as more expensive transition metals such as Ru, Ir, and Pt, have been extensively studied and applied to the OER. Therefore, we investigated whether transition metals without d-orbital active centers, which are not conducive to the OER, could facilitate water oxidation to produce hydrogen peroxide. Currently, no research on water oxidation to produce hydrogen peroxide based on d-band theory has been conducted. We selected and studied six transition metals without d-orbital active centers: Mo, Nb, W, Ta, Zr, and Ti. Only Mo oxides exhibited the best performance for water oxidation to produce hydrogen peroxide, and we designate them as non-OER metal oxides. We also compared MoO3 with different morphologies. Both nanowire and nanosheet MoO3 exhibited excellent performance for water oxidation to produce hydrogen peroxide. The following detailed performance analysis focuses on the nanowire MoO3. Example

[0024] The specific method for synthesizing MoO3 is as follows: tetrahydrate ammonium heptamolybdate (NH4)6Mo7O 24 ·4H2O was calcined at 500℃ for 2 hours to remove the crystal water. 0.72 g of the calcined ammonium heptamolybdate was weighed and placed in 5 mL of hydrogen peroxide. After stirring for 5 minutes, 30 mL of methanol was added, and the mixture was fully stirred for 24 hours and ultrasonicated at room temperature for 30 minutes. The obtained mixed solution was placed in a polytetrafluoroethylene-lined reactor and placed in a hydrothermal oven at 180℃ for hydrothermal reaction for 12 hours. After natural cooling, the obtained precipitate was repeatedly washed with anhydrous ethanol and deionized water and centrifuged. The obtained material was dried at 80℃ for 10 hours and annealed at 300℃ for 2 hours to obtain MoO3 material. The MoO3 material was characterized by XRD and SEM, respectively. Figure 2 and Figure 3 As shown, it is determined that the main exposed crystal plane of the synthesized MoO3 is the (210) crystal plane, and the morphology obtained by synthesis is a nanowire morphology.

[0025] Based on the existing synthesis method, the present invention also synthesizes the corresponding oxides Nb2O5, WO3, Ta2O5, ZrO2, and TiO2 for other Nb, W, Ta, Zr, and Ti that do not contain d-orbital active centers, and synthesizes the corresponding oxides V2O5, Cr2O3, and Co3O4 for V, Cr, and Co that contain d-orbital active centers, in order to carry out subsequent material performance tests. The specific synthesis process is not described in detail here.

[0026] Application Examples

[0027] MoO3 was prepared as an anode for electrocatalytic water decomposition using the ethyl cellulose film-forming method. The specific preparation process is as follows: weigh 0.01 g of ethyl cellulose and 0.025 g of the above-mentioned MoO3 material, dissolve them in 1 mL of anhydrous ethanol, and stir thoroughly for 1 h. Then add 0.2 mL of α-pinene alcohol, stir thoroughly for 1 h and ultrasonically treat for 20 min. The resulting mixed solution was left exposed to evaporate the solvent to obtain a viscous slurry. Each time, 50 μL of the slurry was coated on the conductive surface of the conductive glass FTO, and the coating area was 1 cm 2 The coated FTO was placed under an infrared baking lamp for drying and then annealed in a muffle furnace at 350 °C for 30 min to obtain a MoO3 material electrode.

[0028] Here, the metal oxides Nb2O5, WO3, Ta2O5, ZrO2, and TiO2 are prepared into corresponding electrocatalytic water splitting anodes in the same preparation method. The specific preparation process is not described in detail here.

[0029] The electrodes prepared from the above-mentioned MoO3 materials and metal oxide materials Nb2O5, WO3, Ta2O5, ZrO2, and TiO2 were used as anodes for electrocatalytic water decomposition, and calomel electrodes were used as reference electrodes and platinum wires as counter electrodes. At the same time, in order to avoid interference from other reactions (such as possible oxygen reduction reactions at the cathode) and the decomposition of hydrogen peroxide produced by the oxidation of water at the anode by platinum wire, an H-type double-chamber electrolytic cell was used for the study, in which the MoO3 material electrode and the calomel reference electrode were placed at the anode, and the platinum wire was placed at the cathode as the counter electrode. In the selection of the electrolyte system, we chose non-HCO3 - The CH3COONa electrolyte of the system was developed, and the CH3COON electrolytes with different pH were studied.

[0030] like Figure 4 As shown in the figure, the electrochemical performance of the prepared MoO3 anode was characterized in CH3COONa electrolyte with pH = 9.6, and the current value was 14 mA·cm at a potential of 3.5 V vs. RHE. -2 , the overpotential is 2.65 V vs. RHE, and the Tafel slope is 0.37 V·dec-1 .

[0031] like Figure 5 As shown in the figure, in a CH3COONa electrolyte with a pH of 9.6, a constant potential polarization test was performed on the MoO3 material electrode starting from a potential of 2.8 V vs. RHE and at intervals of 0.2 V vs. RHE. The test time was 10 minutes, and the anolyte was taken out to quantitatively determine the hydrogen peroxide content. After measurement, from the potential value of 2.8-3.6 V vs. RHE, the MoO3 material electrode showed a certain electrocatalytic water oxidation selectivity in the CH3COONa electrolyte system. A certain concentration of hydrogen peroxide was detected in the electrolyte, and the concentration of hydrogen peroxide increased with the increase of the potential value. At the potential value of 3.6 V vs. RHE, the concentration of hydrogen peroxide produced by water oxidation by MoO3 in the CH3COONa electrolyte with a pH of 9.6 was 74.85 μmol·L -1 After calculating the Faradaic efficiency of MoO3 producing hydrogen peroxide in the CH3COONa electrolyte system, MoO3 achieved the best Faradaic efficiency of 35% at a potential of 3.2 V vs. RHE.

[0032] like Figure 6 As shown in the figure, at the optimal potential of 3.2 V vs. RHE, the performance of MoO3 in water oxidation to produce hydrogen peroxide was tested in CH3COONa electrolytes at pH = 5, pH = 7, pH = 8, pH = 9.6, and pH = 10.5. After testing, MoO3 achieved the best performance in water oxidation to produce hydrogen peroxide in CH3COONa electrolyte at pH = 9.6, and the concentration of hydrogen peroxide produced in a 10-min constant potential polarization test was 58.91 μmol·L -1 , the calculated Faradaic efficiency is 35%.

[0033] like Figure 7 As shown in Figure 2, the performance of other metal oxides, Nb2O5, WO3, Ta2O5, ZrO2, and TiO2, in water oxidation to produce hydrogen peroxide in a CH3COONa electrolyte at pH 9.6 was tested and compared with MoO3. Among these six metal oxides without d-orbital active centers, MoO3 exhibited the best selectivity for water oxidation to produce hydrogen peroxide. In the measurement, MoO3 produced the highest hydrogen peroxide concentration and also had the greatest Faradaic efficiency.

[0034] like Figure 8As shown in the figure, the performance of water oxidation to produce hydrogen peroxide was compared between MoO3 without d-orbital active centers and metal oxides V2O5, Cr2O3, and Co3O4 containing d-orbital active centers. At a potential of 3.2 V vs. RHE, the electrocatalytic water oxidation performance of the three metal oxides containing d-orbital active centers (V2O5, Cr2O3, and Co3O4) was poor, especially Co3O4, which showed no selectivity for electrocatalytic water oxidation. This further proves that based on the d-band theory, the non-oxygen-evolving metal oxide MoO3 without d-orbital active centers selected for synthesis has good electrocatalytic water oxidation selectivity.

[0035] Starting from the d-band theory, the present invention aims to control the two competing reactions of hydrogen peroxide evolution and oxygen evolution in the electrocatalytic water splitting anode reaction. From the perspective of reaction thermodynamics and electronic structure, the metal oxide MoO3 is selected and synthesized, and it is prepared into the anode of electrocatalytic water splitting by ethyl cellulose film formation method. - In the CH3COONa electrolyte of the system, a Faradaic efficiency of 35% was achieved for water oxidation to produce hydrogen peroxide.

[0036] While the present invention has been disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Persons skilled in the art will readily appreciate that various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A use of MoO3 material in electrocatalytic water oxidation to produce hydrogen peroxide, characterized in that: MoO3 material is coated on the FTO surface using an ethyl cellulose film-forming method as an anode catalyst material for water oxidation to produce hydrogen peroxide, wherein the electrocatalytic reaction system is a CH3COONa solution system.

2. The use according to claim 1, characterized in that The mass ratio of MoO3 to ethyl cellulose is 1:2.5.

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