Method for coupling aldehyde oxidation hydrogen production with hydrogen peroxide electrosynthesis

Abstract

The invention discloses a method for electrosynthesizing hydrogen peroxide by coupling anode aldehyde oxidation hydrogen production with cathode oxygen reduction, which comprises the following steps: in an electrosynthesis device provided with an anode reaction chamber and a cathode reaction chamber, adding an alkaline electrolyte containing an aldehyde group substance into an electrolytic tank, and carrying out electrocatalytic oxidation reaction at lower voltage. And electrolyte is introduced into the cathode reaction chamber, oxygen is introduced at the same time, and the reaction of oxygen reduction electrosynthesis of hydrogen peroxide is carried out. The anode reaction chamber and the cathode reaction chamber are separated by a polymer ion exchange membrane, and a fuel cell system capable of outputting electric energy is formed by anode low-potential oxidation and cathode oxygen reduction reaction. According to the invention, a reaction substrate containing an aldehyde group is subjected to high-selectivity and high-yield electrocatalytic oxidation at a low voltage into a carboxylic acid compound with a high additional value and generates hydrogen, the cathode synthesizes hydrogen peroxide through an oxygen reduction reaction, and chemicals with high additional values are generated at both the cathode and the anode of the electrocatalytic device; meanwhile, electric energy can be generated.

Description

Technical Field

[0001] This invention relates to the field of electrocatalysis and electrosynthesis technology, specifically to a method for the electrosynthesis of hydrogen peroxide by anodic aldehyde oxidation to produce hydrogen coupled with cathodic oxygen reduction. Background Technology

[0002] Hydrogen peroxide (H2O2), as an important basic chemical, is widely used in medical sterilization, wastewater treatment, chemical synthesis, papermaking, textiles, and other industries. Currently, industrial production of H2O2 mainly (>95%) relies on the energy-intensive "anthraquinone process," which requires large amounts of aromatic hydrocarbons and ester solvents for separation and purification, resulting in high energy consumption and environmental pollution from reaction byproducts. H2O2 synthesized via electrocatalytic oxygen reduction can be directly applied in medical sterilization, wastewater treatment, and other fields, achieving in-situ distributed green production and application of H2O2, reducing transportation safety risks, and representing a synthetic route with great development potential.

[0003] There are two main types of devices for synthesizing H2O2 via a two-electron oxygen reduction electrocatalytic reaction. One type is a fuel cell device capable of outputting electrical energy. This process decouples the H2 / O2 redox reaction into two half-cell reactions: two-electron oxygen reduction (ORR) and hydrogen oxidation (HOR) to synthesize H2O2. The other type is an electrolytic cell device based on the Huron-Dow process, where the cathode is the oxygen reduction reaction and the anode uses a higher-potential oxygen evolution reaction (OER). Since OER kinetics are slow and the added value of the generated O2 is low, replacing OER with an electro-oxidation reaction that has more favorable kinetics and higher added value of the reaction products has greater development potential and application value. Replacing HOR or OER with a reaction that uses the low-potential oxidation of aldehydes to carboxylic acids to generate H2 can simultaneously achieve the oxidation of aldehydes to carboxylic acids at the anode to produce hydrogen and the electrocatalytic synthesis of H2O2 at the cathode. This device is a fuel cell reaction system that can output electrical energy during the electrochemical synthesis process. This synthesis strategy is of great significance for the development of electrochemical energy storage in material conversion processes. Summary of the Invention

[0004] This invention provides a method for the electrosynthesis of hydrogen peroxide by anodic aldehyde oxidation coupled with cathodic oxygen reduction. This method allows for the electrosynthesis of high-value-added chemicals at both the anode and cathode in an electrosynthesis apparatus equipped with an anode and cathode, while simultaneously outputting electrical energy. To achieve the above objectives, the technical solution of this invention is as follows.

[0005] This invention discloses a method for the electrosynthesis of hydrogen peroxide by anodic aldehyde oxidation coupled with cathodic oxygen reduction, comprising the following steps:

[0006] An electrosynthesis device is provided, which is provided with an anode reaction chamber and a cathode reaction chamber. In the anode reaction chamber, aldehyde undergoes an oxidation reaction at a low potential in an alkaline electrolyte to produce carboxylic acid and hydrogen gas. In the cathode reaction chamber, oxygen is introduced to undergo an oxygen reduction reaction to synthesize hydrogen peroxide. The low-potential oxidation of aldehyde at the anode and the oxygen reduction reaction at the cathode constitute an electrosynthesis system capable of outputting electrical energy.

[0007] In some embodiments, the electrosynthesis device is provided with a polymer ion exchange membrane between the anode reaction chamber and the cathode reaction chamber, the electrolyte containing aldehydes is introduced into the anode reaction chamber, and air or oxygen is introduced into the cathode electrolyte.

[0008] In some embodiments, the method for electrocatalytic oxidation of aldehydes to carboxylic acids while simultaneously producing hydrogen gas, wherein the anodic catalyst material in the working electrode is a metal of copper, silver, or gold, or an electrode containing an alloy of copper, silver, or gold.

[0009] In some embodiments, the cathode oxygen reduction synthesis of hydrogen peroxide method uses a cathode catalytic material in the working electrode that is one of conductive carbon black, carbon paper, carbon cloth, carbon felt, carbon nanotubes, carbon fibers, graphene, and activated carbon.

[0010] In some embodiments, the electrolyte in the anolyte is at least one of KOH or NaOH, and the electrolyte concentration is 0.1 mol·L⁻¹. -1 ~5mol·L -1 Between these, the cathode electrolyte is the same electrolyte solution corresponding to the anolyte.

[0011] In some embodiments, the anolyte and catholyte are both introduced into the anolyte and catholyte reaction chambers respectively via peristaltic pumps, and the electrolyte is discharged after a single pass through the reaction chamber. Oxygen on the cathode side enters the catholyte reaction chamber after passing through a mass flow meter, and excess gas is discharged after a single pass through the catholyte reaction chamber.

[0012] In some embodiments, the method for electrocatalytic oxidation of aldehydes to carboxylic acids to simultaneously generate hydrogen gas, wherein the anolyte is a substrate containing an aldehyde group selected from at least one of formaldehyde, acetaldehyde, propionaldehyde, glyoxylic acid, methyl ethyl acetaldehyde, furfural, 5-methylfurfural, 5-hydroxymethylfurfural, benzaldehyde, phenylacetaldehyde, phenylpropionaldehyde, cinnamaldehyde, and vanillin.

[0013] In some embodiments, the method for electrocatalytic oxidation of aldehydes to carboxylic acids while simultaneously producing hydrogen gas has a concentration of aldehyde-containing substances in the anolyte reaction chamber of 1 mmol·L⁻¹. -1 ~500mmol·L -1 .

[0014] In some embodiments, the method of oxidizing aldehyde to carboxylic acid to generate hydrogen gas simultaneously coupled with cathode oxygen reduction to generate hydrogen peroxide, wherein the temperature of the electrolyte is 10°C to 80°C.

[0015] This invention provides a method for the electrosynthesis of hydrogen peroxide by anodic aldehyde oxidation coupled with cathodic oxygen reduction. Compared with the prior art, this invention has the following advantages:

[0016] 1. This invention enables the electrochemical oxidation of reaction substrates containing aldehyde groups into higher value-added carboxylic acid compounds at the anode with high Faradaic efficiency and high selectivity, without requiring external electrical energy. Simultaneously, hydrogen gas is generated at the anode, and oxygen can be electrochemically reduced to H₂O₂ with high Faradaic efficiency at the cathode. The cathode and anode of this electrosynthesis device can output electrical energy while simultaneously electrosynthesizing high-value-added chemicals.

[0017] 2. The method for electrosynthesizing H2O2 by anodic aldehyde oxidation to produce hydrogen coupled with cathodic oxygen reduction of the present invention has a simple apparatus, is easy to operate, and has low cost. It can be used for large-scale production. While synthesizing carboxylic acids, hydrogen and H2O2 from substances containing aldehyde groups and oxygen in the air as raw materials, it can output electrical energy. It is a green and economical self-driven electrosynthesis method. Attached Figure Description

[0018] Figure 1 The chromatogram of the oxidation products of 5-hydroxymethylfurfural electrolyzed in Example 1 at 0.3V relative to the hydrogen electrode in a three-electrode system is shown over time. The horizontal axis represents retention time (min).

[0019] Figure 2 The linear scan curves for Example 1 are obtained by using a three-electrode system before and after the addition of 5-hydroxymethylfurfural (HMF) at potentials of 0V to 0.4V; where the horizontal axis represents voltage (V) and the vertical axis represents the voltage (mA·cm). -2 ) represents the current density;

[0020] Figure 3 Example 2 shows the variation of hydrogen production from the oxidation of 5-hydroxymethylfurfural in a three-electrode system with the anode operating at 0.3V relative to the hydrogen electrode, as a function of charge transfer number. The horizontal axis, Charge (C), represents the charge transfer number.

[0021] Figure 4 Example 3: In the electrosynthesis device, at 50 mol·L⁻¹ -1 The polarization curves and power density plots of 5-hydroxymethylfurfural (HMF) during the oxidation reaction of the substrate are shown; where the horizontal axis represents the current density (mA·cm). -2The left vertical axis represents the current density; the left vertical axis represents the cell voltage (V), and the right vertical axis represents the power density (mW·cm). -2 () represents the device's output power density;

[0022] Figure 5 Examples 3, 6, and 7 describe the Faraday efficiency and yield of H2O2 electrosynthesis at the cathode in the electrosynthesis device when the output voltage is 0V, 0.2V, and 0.4V, respectively. Detailed Implementation

[0023] To facilitate understanding of the present invention, a more comprehensive description is provided below, along with preferred embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0025] This invention provides a method for the electrosynthesis of hydrogen peroxide by anodic aldehyde oxidation coupled with cathodic oxygen reduction, comprising the following steps:

[0026] An electrosynthesis device is provided, which is equipped with an anode reaction chamber and a cathode reaction chamber. It can carry out electrosynthesis reactions at an output voltage of 0V to 0.8V. In the anode reaction chamber, aldehydes undergo an oxidation reaction at a low potential in an alkaline electrolyte to produce carboxylic acid and hydrogen gas. Oxygen is introduced into the cathode reaction chamber to undergo an oxygen reduction reaction to synthesize hydrogen peroxide. The low-potential oxidation of aldehydes at the anode and the oxygen reduction reaction at the cathode constitute an electrosynthesis system that can output electrical energy.

[0027] In one embodiment, the electrosynthesis device is provided with a polymer ion exchange membrane between the anode reaction chamber and the cathode reaction chamber, the electrolyte containing aldehydes is introduced into the anode reaction chamber, and air or oxygen is introduced into the cathode electrolyte.

[0028] In one embodiment, in the method for electrocatalytic oxidation of aldehydes to carboxylic acids while simultaneously producing hydrogen, the anolyte in the working electrode is a metal such as copper, silver, or gold, or an alloy electrode containing copper, silver, or gold. Optionally, the number of intrinsic active sites on the metal catalyst electrode can be increased through chemical, electrochemical, or other treatment methods.

[0029] In one embodiment, in the method for synthesizing hydrogen peroxide by reducing oxygen at the cathode, the cathode catalytic material in the working electrode is one of conductive carbon black, carbon paper, carbon cloth, carbon felt, carbon nanotubes, carbon fibers, graphene, and activated carbon. Optionally, the selectivity of the cathode carbon material for the electrosynthesis of hydrogen peroxide by reducing oxygen at the cathode can be improved by introducing oxygen-containing functional groups through oxidation treatment.

[0030] In one embodiment, the electrolyte in the anolyte is at least one of KOH or NaOH solution, and the electrolyte concentration is 0.1 mol·L⁻¹. -1 ~5mol·L -1 Between these, the cathode electrolyte is the same electrolyte solution corresponding to the anolyte.

[0031] In one embodiment, both the anolyte and the catholyte are introduced into the anolyte and catholyte reaction chambers via peristaltic pumps, and the electrolyte is discharged after passing through the reaction chambers in a single pass; preferably, the flow rate of the peristaltic pump can be controlled at 0.5 mL / min. -1 ~30mL min -1 Within the range; oxygen on the cathode side enters the cathode reaction chamber after passing through the mass flow meter, and excess gas is discharged after passing through the cathode reaction chamber once in a single pass. Preferably, the oxygen or air flow rate can be controlled within the range of 1 sccm to 500 sccm by the mass flow meter.

[0032] In one embodiment, the cathode catalytic electrode is typically constructed by thermally spraying a carbon-based catalytic material onto carbon paper or carbon felt to form a gas diffusion electrode. Optionally, the spraying amount of the carbon-based catalytic material is 0.5 mg·cm³. -2 ~10mg·cm -2 Preferably, the coating amount of the carbon-based catalyst is 0.5 mg·cm³. -2 .

[0033] In one embodiment, the method for electrocatalytic oxidation of aldehydes to carboxylic acids to simultaneously generate hydrogen gas, wherein the anolyte is an aldehyde-containing substrate selected from at least one of formaldehyde, acetaldehyde, propionaldehyde, glyoxylic acid, methyl ethyl acetaldehyde, furfural, 5-methylfurfural, 5-hydroxymethylfurfural, benzaldehyde, phenylacetaldehyde, phenylpropionaldehyde, cinnamaldehyde, and vanillin.

[0034] In one embodiment, in the method of electrocatalytic oxidation of aldehyde to carboxylic acid while simultaneously producing hydrogen gas, the concentration of the aldehyde-containing substance in the anolyte reaction chamber is 1 mmol·L⁻¹. -1 ~500mmol·L -1 .

[0035] In one embodiment, the method for oxidizing the aldehyde to a carboxylic acid while simultaneously generating hydrogen gas, coupled with cathode oxygen reduction to generate hydrogen peroxide, wherein the temperature of the electrolyte is 10°C to 80°C. Optionally, the electrosynthesis reaction is carried out at room temperature.

[0036] The reaction mechanism of this invention, which involves the electrocatalytic oxidation of aldehydes to carboxylic acids while simultaneously producing hydrogen gas, is as follows:

[0037] Anodic reaction: R-CHO + 2OH - →R-COO - +1 / 2H₂ + H₂O + e -

[0038] The reaction mechanism of hydrogen peroxide production by cathode oxygen reduction in this invention is as follows:

[0039] Cathode reaction: O2 + H2O + 2e - →HO2-+OH -

[0040] The present invention has the following beneficial effects:

[0041] This invention enables the electrochemical oxidation of aldehyde-containing reaction substrates into higher-value-added carboxylic acid compounds at the anode with high Faradaic efficiency and high selectivity, without requiring external electrical energy. Simultaneously, hydrogen gas is generated at the anode, and oxygen can be electrochemically reduced to H₂O₂ with high Faradaic efficiency at the cathode. The cathode and anode of this electrosynthesis device can output electrical energy while simultaneously electrosynthesizing high-value-added chemicals.

[0042] The following are specific examples.

[0043] Example 1

[0044] In an H-type quartz electrolytic cell, separated by a polymer electrolyte membrane, 30 mL of KOH (1 M) electrolyte was added to both the cathode and anolyte cells. Electrocatalysis was performed using a three-electrode system. Copper nanowires (Cu NWs, electrode size: 1 cm × 1 cm) synthesized on a copper foam substrate were used as the working electrode, an Hg / HgO electrode as the reference electrode, and a carbon rod as the counter electrode. 5-hydroxymethylfurfural (HMF) was added to the anolyte cell to an initial concentration of 50 mM, and the electrolysis temperature was 20 °C. Electrolysis was carried out at a constant potential of 0.3 V vs. RHE (relative to the hydrogen electrode), with samples taken every 5 min. The electrolyte containing organic matter was diluted with water and analyzed by high-performance liquid chromatography (HPLC). Figure 1 It can be seen that in the three-electrode system, HMF is oxidized to 5-hydroxymethylfurfural (HMFCA) at a constant potential of 0.3V relative to the hydrogen electrode. Apart from this, no other types of oxidation products are generated, which shows high selectivity. Figure 2 It is a linear scan curve.

[0045] Comparative Example 1

[0046] In an H-type quartz electrolytic cell, separated by a polymer electrolyte membrane, 30 mL of KOH (1 M) electrolyte was added to both the cathode and anolyte cells. Electrocatalysis was performed using a three-electrode system, with commercial copper foam (Cu foam, electrode size: 1 cm × 1 cm) as the working electrode, an Hg / HgO electrode as the reference electrode, and a carbon rod as the counter electrode. 5-hydroxymethylfurfural (HMF) was added to the anolyte cell at an initial concentration of 50 mM, and the electrolysis temperature was 20 °C. The linear sweep curve is shown below. Figure 2 As shown.

[0047] Example 2

[0048] In an H-type quartz electrolytic cell, separated by a polymer electrolyte membrane, 30 mL of KOH (1 M) electrolyte was added to both the cathode and anolyte cells. Electrocatalysis was performed using a three-electrode system. Copper nanowires synthesized on a copper foam substrate (electrode size: 1 cm × 1 cm) served as the working electrode, an Hg / HgO electrode as the reference electrode, and a carbon rod as the counter electrode. 5-hydroxymethylfurfural (HMF) was added to the anolyte cell at an initial concentration of 100 mM, and the electrolysis temperature was 20 °C. Electrolysis was carried out at a constant potential of 0.3 VVs.RHE (relative to the hydrogen electrode). The amount of H2 generated during the electrooxidation of HMF to HMFCA was collected using a water displacement method. A graph showing the relationship between hydrogen production and charge transfer was plotted based on the amount of charge and the amount of hydrogen collected. The results are shown below. Figure 3 As shown.

[0049] Example 3

[0050] Electrochemical device performance testing

[0051] In the H-type electrolytic cell device, a polymer electrolyte membrane separates the two compartments, and the anode chamber is pumped by a peristaltic pump at a rate of 7.1 mL / min. -1 1 mol L of solution containing 50 mM HMF was pumped in uniformly. -1 KOH solution, gas diffusion electrode catalyst layer side in cathode chamber, is pumped at 2.7 mL / min by a peristaltic pump. -1 0.1 mol L was pumped in uniformly. -1 A KOH solution was used, and oxygen was introduced at 50 sccm on the gas side of the cathode gas diffusion electrode using a gas mass flow meter. Electrocatalysis was performed using two electrodes. Copper nanowires synthesized on a copper foam substrate (electrode size: 2cm × 2cm) served as the anode working electrode. Conductive carbon black, oxidized with concentrated nitric acid, was sprayed onto hydrophobic carbon paper (carbon black coating amount: 0.5 mg·cm³). -2The electrode (2cm × 2cm) was used as the cathode gas diffusion electrode. The electrolysis reaction was carried out at room temperature, and the output voltage was set to 0V. The polarization curve and power density diagram of the electrochemical device are shown below. Figure 4 As shown. Electrolyte containing organic matter at the anode outlet was sampled at fixed time intervals. After dilution with water, the samples were quantitatively analyzed by high-performance liquid chromatography (HPLC). Electrolyte at the cathode outlet was sampled at fixed time intervals, and the samples were added to acidic titanium sulfate solution for color development, followed by quantitative analysis using a UV-Vis spectrophotometer. The Faraday efficiency and yield of H₂O₂ electrosynthesis at the cathode changed with the operating time of the reaction device as shown in the figure. Figure 5 As shown.

[0052] Example 4

[0053] Example 4 is basically the same as Example 3, except that the amount of conductive carbon black sprayed onto the cathode working electrode is 2.5 mg·cm³. -2 .

[0054] Example 5

[0055] Example 5 is basically the same as Example 3, except that the amount of conductive carbon black sprayed onto the cathode working electrode is 5.0 mg·cm³. -2 .

[0056] Example 6

[0057] Example 6 is basically the same as Example 3, except that the output voltage is set to 0.2V. The Faraday efficiency and yield of cathode electrosynthesis of H2O2 change with the operating time of the reaction device as follows: Figure 5 As shown.

[0058] Example 7

[0059] Example 7 is basically the same as Example 3, except that the output voltage is set to 0.4V. The Faraday efficiency and yield of cathode electrosynthesis of H2O2 change with the operating time of the reaction device as follows: Figure 5 As shown.

[0060] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0061] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. This invention discloses a method for the electrosynthesis of hydrogen peroxide by anodic aldehyde oxidation coupled with cathodic oxygen reduction, characterized in that, Includes the following steps: An electrosynthesis device is provided, which is provided with an anode reaction chamber and a cathode reaction chamber. In the anode reaction chamber, aldehyde undergoes an oxidation reaction at a low potential in an alkaline electrolyte to produce carboxylic acid and hydrogen gas. In the cathode reaction chamber, oxygen is introduced to undergo an oxygen reduction reaction to synthesize hydrogen peroxide. The low-potential oxidation of aldehyde at the anode and the oxygen reduction reaction at the cathode constitute an electrosynthesis system capable of outputting electrical energy.

2. The electrosynthesis method as described in claim 1, characterized in that, The electrosynthesis device is equipped with a polymer ion exchange membrane between the anode reaction chamber and the cathode reaction chamber. The electrolyte containing aldehydes is introduced into the anode reaction chamber, and air or oxygen is introduced into the cathode electrolyte.

3. The method for electrocatalytic oxidation of aldehydes to carboxylic acids to simultaneously produce hydrogen gas as described in claim 1, characterized in that, The anodic catalyst material in the working electrode is one of copper, silver, or gold metals or an electrode containing copper, silver, or gold alloys.

4. The method for synthesizing hydrogen peroxide by reducing oxygen at the cathode as described in claim 1, characterized in that, The cathode catalytic material in the working electrode is one of the following: conductive carbon black, carbon paper, carbon cloth, carbon felt, carbon nanotubes, carbon fiber, graphene, and activated carbon.

5. The electrosynthesis method according to claims 1 to 4, characterized in that, The electrolyte in the anolyte is at least one of KOH or NaOH, and the electrolyte concentration is 0.1 mol·L⁻¹. -1 ~5mol·L -1 Between these, the cathode electrolyte is the same electrolyte solution corresponding to the anolyte.

6. The electrosynthesis method according to claims 1 to 4, characterized in that, Both the anolyte and catholyte are introduced into the anolyte and catholyte reaction chambers respectively via peristaltic pumps. The electrolyte is discharged after passing through the reaction chamber in a single pass. Oxygen on the cathode side enters the catholyte reaction chamber after passing through a mass flow meter, and excess gas is discharged after passing through the catholyte reaction chamber in a single pass.

7. The anode-side reaction according to any one of claims 1 to 4, characterized in that, The reaction substrate is an aldehyde-containing substrate selected from at least one of formaldehyde, acetaldehyde, propionaldehyde, glyoxylic acid, methyl ethyl acetaldehyde, furfural, 5-methylfurfural, 5-hydroxymethylfurfural, benzaldehyde, phenylacetaldehyde, phenylpropionaldehyde, cinnamaldehyde, and vanillin.

8. The method for aldehyde oxidation to simultaneously generate hydrogen gas as described in claims 1-4 and 7, characterized in that, The concentration of aldehyde-containing substances in the anolyte reaction chamber is 1 mmol·L⁻¹. -1 ~500mmol·L -1 .

9. The method for oxidizing aldehydes to carboxylic acids simultaneously to generate hydrogen gas, coupled with cathode oxygen reduction to generate hydrogen peroxide, as described in any one of claims 1 to 8, characterized in that... The operating temperature of the electrosynthesis device is 10℃~80℃.

Images