Method for preparing glyceric acid through oxidation of ethylene glycol under photoelectrocatalysis

Abstract

The invention provides a method for preparing glyceric acid through oxidation of ethylene glycol under photoelectrocatalysis, and belongs to the technical field of photoelectrocatalysis. Firstly, a photoelectrode is prepared, then an ethylene glycol aqueous solution added with potassium chloride and potassium sulfate is used as a reaction solution, after the pH value is adjusted by sodium hydroxide, a photoelectrocatalysis ethylene glycol oxidation reaction is carried out, and C3 products such as glyceric acid are prepared. According to the invention, preparation of C3 products such as glyceric acid from a C2 raw material (ethylene glycol) is realized innovatively based on a broken bond coupling process of ethylene glycol, and development and application of ethylene glycol oxidation reaction in the photoelectric field are greatly broadened; compared with a thermocatalysis mode, ethylene glycol is adopted as a single raw material for the first time, catalysis under the conditions of high temperature, high pressure, precious metal or strong alkalinity is not needed, and an innovative solution is provided for efficient and high-selectivity value-added conversion of ethylene glycol and green synthesis of glyceric acid; and a new technical route is provided for realizing preparation of a long-chain compound by increasing a carbon chain.

Description

Technical Field

[0001] The invention relates to the technical field of photoelectrocatalysis, and in particular to a method for preparing glyceric acid by photoelectrocatalytic oxidation of ethylene glycol. Background Art

[0002] Polyethylene terephthalate (PET) ranks among the most produced polyester materials globally. Its recycling primarily relies on acid-base catalysis or high-temperature, high-pressure hydrothermal degradation processes, with ethylene glycol as one of its primary products. As a basic chemical, subsequent high-value-added conversions of ethylene glycol often face challenges such as high energy consumption and complex processes. This is why the environmentally friendly photoelectrocatalytic (PEC) ethylene glycol upgrading technology has emerged.

[0003] At present, the products of photoelectrocatalytic ethylene glycol oxidation upgrading are mostly C1 products. For example, the literature published by Luo Jingshan's team reported a BiVO4 / NiCo-LDH photoanode that can oxidize ethylene glycol to formate through photoelectrocatalytic technology under strong alkaline conditions (0.1M KOH) (Dong C, Lin C, Li P, et al. Surface Coverage Tuning for Suppressing Over-Oxidation: ACase of Photoelectrochemical Alcohol-to-Aldehyde / Ketone Conversion[J]. Angewandte Chemie, 2025, 137(12): e202423730.); there are also a few reports on the photoelectrocatalytic ethylene glycol oxidation upgrading to C2 products. For example, the literature published by Zhang Kan's team reported a photoelectrochemical polarization strategy using bismuth vanadate to suppress the over-oxidation of alcohols, and to photoelectrochemically upgrade ethylene glycol to ethanolaldehyde under acidic, high ethylene glycol concentration and low bias conditions (Kang F, Wang Q, Du D, et al. Photoelectrochemical Ethylene Glycol Oxidization Coupled with Hydrogen Generation Using Metal Oxide Photoelectrodes[J]. Angewandte Chemie International Edition, 2025, 64(5): e202417648.). The two reaction pathways for generating C1 and C2 products are as follows: Path 1: The C-C bond in the ethylene glycol molecule breaks to generate a transient C1 intermediate (such as CH2OH), which is then oxidized to form formic acid; Path 2: The ethylene glycol molecule is selectively oxidized to glycolaldehyde through a two-electron transfer process, and glycolaldehyde is further oxidized to glycolic acid or glyoxal. In this process, the C2 skeleton is retained, and a portion of the C2 intermediates (including glycolaldehyde, glycolic acid, and glyoxal) desorb on the catalyst surface to avoid subsequent C-C bond breakage and accumulate as the final C2 product. The remaining C2 intermediates are further oxidized to the C1 product formic acid through C-C bond breakage.

[0004] Currently, there are no reports on the photoelectrocatalytic oxidation of ethylene glycol to C3 products. C3 products, such as glyceric acid, have higher scientific and economic value than C1 or C2 products. Currently, the dehydrogenative cross-coupling of ethylene glycol with methanol is often used to generate C3 products from ethylene glycol. This method is widely used in the field of thermal catalysis, but it requires high temperature and high pressure reaction conditions, and the cross-coupling process is often accompanied by dehydration, resulting in lactic acid rather than the more economically valuable glyceric acid. In addition, this method introduces methanol as a reactant, rather than simply a self-bond cleavage coupling process of ethylene glycol. The difficulty in using photoelectrocatalytic oxidation of ethylene glycol to glyceric acid lies in how to control the self-bond cleavage process of ethylene glycol and achieve the coupling process of C1 and C2 intermediates while avoiding product dehydration to form the more valuable glyceric acid product. Therefore, the use of green and environmentally friendly photoelectrocatalytic technology to actively explore and expand the ethylene glycol oxidation reaction pathway and prepare C3 products with greater scientific and economic value based on the coupling pathway is of great significance in this field. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing glyceric acid by photoelectrocatalytic oxidation of ethylene glycol. Based on a coupling pathway, this method unprecedentedly uses C3 products such as glyceric acid as the main products of the photoelectrocatalytic ethylene glycol oxidation reaction. Common photoanodes in photoelectrocatalysis, such as BiVO4, TiO2, WO3, and Fe2O3, especially bismuth vanadate photoanode, are used, and metal hydroxide oxide (MOOH) is used as a surface co-catalyst through a simple impregnation method, which significantly improves the selectivity and yield of C3 products such as glyceric acid, providing a highly promising technical method for achieving high-value-added conversion and upgrading of ethylene glycol.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for preparing glyceric acid by photoelectrocatalytic oxidation of ethylene glycol comprises the following steps:

[0008] Step 1, preparing a photoanode, wherein the photoanode is selected from one of bismuth vanadate (BiVO4) photoanode, titanium dioxide (TiO2) photoanode, tungsten oxide (WO3) photoanode, iron oxide (Fe2O3) photoanode or a composite photoanode loaded with a promoter.

[0009] Step 2, photoelectrocatalytic oxidation of ethylene glycol to C3 product: add appropriate amounts of potassium chloride and potassium sulfate to the ethylene glycol aqueous solution, and use sodium hydroxide to adjust the solution pH to 10-14, as the reaction solution, the concentration of potassium chloride in the reaction solution is 0.01-0.25M, the concentration of potassium sulfate is 0.1-0.25M, and the concentration of ethylene glycol is 0.1-2M; the photoanode prepared in step 1 is used as the working electrode, the platinum wire is used as the counter electrode, and Hg / HgO is used as the reference electrode. The applied voltage is 0.8-1.4V vs. RHE. Under room temperature, under simulated sunlight light (300W xenon lamp, light intensity of 100mW / cm 2 ) was subjected to photoelectrocatalytic ethylene glycol oxidation reaction for 1 to 4 hours to prepare C3 products including glyceric acid.

[0010] Furthermore, in step 1, the composite photoanode is preferably a metal oxyhydroxide bismuth vanadate composite photoanode (MOOH / BVO), wherein the metal is selected from one or more of iron, nickel, and cobalt.

[0011] Furthermore, the preparation method of the metal hydroxide oxybismuth vanadate composite photoanode is as follows: first, the bismuth vanadate photoanode is prepared by electrochemical deposition; then the metal hydroxide oxybismuth vanadate photoanode is loaded on the surface of the bismuth vanadate photoanode by impregnation to obtain the metal hydroxide oxybismuth vanadate composite photoanode.

[0012] The present invention uses a photoanode to carry out a photoelectrocatalytic ethylene glycol oxidation reaction, and efficiently converts it into C3 products such as glyceric acid. The mechanism is that the photoanode generates electron-hole pairs under light. For the intrinsic photoanode with serious electron-hole pair recombination, the electron-hole separation efficiency is improved by loading a co-catalyst, so that more unrecombined photogenerated holes migrate to the surface of the photoanode to participate in the ethylene glycol oxidation reaction. The most important processes in the present invention are the C-C bond cleavage and C-C bond coupling of ethylene glycol, which are specifically as follows: ethylene glycol first undergoes C-C bond cleavage under the joint action of the photoanode and hydroxide ions to generate a C1 intermediate. In this process, the hydroxy oxide loaded on the surface of the bismuth vanadate photoanode acts as a co-catalyst to promote the C-C bond cleavage process and increase the generation of the C1 intermediate. By adjusting the pH of the solution, sufficient hydroxide ions are present in the solution, which also accelerates the C-C bond cleavage and increases the generation rate of the C1 intermediate. At the same time, the ethylene glycol molecule is selectively oxidized to ethanolaldehyde through a double electron transfer process, and the addition of chloride ions promotes the activation of the α-H of ethanolaldehyde, and the resulting C2 intermediate undergoes a coupling reaction with the C1 intermediate to generate glyceraldehyde. The hydroxide ions obtain holes on the surface of the photoanode to generate hydroxyl radicals, and glyceraldehyde either reacts with the hydroxyl radicals to generate glyceric acid or undergoes an isomerization reaction under the action of hydroxide ions to generate dihydroxyacetone, thereby generating different C3 products, such as Figure 1 shown.

[0013] Compared with the prior art, the present invention has at least the following beneficial effects:

[0014] (1) The MOOH / BVO photoanode prepared in the present invention exhibits high selectivity for C3 products such as glyceric acid in the ethylene glycol oxidation reaction. In addition, compared with the existing photoelectrocatalytic ethylene glycol oxidation reaction that produces C1 and C2 products, the present invention innovatively realizes the preparation of C3 products such as glyceric acid from C2 raw materials (ethylene glycol) based on the bond-breaking coupling process of ethylene glycol itself, greatly broadening the development and application of ethylene glycol oxidation reactions in the photoelectric field.

[0015] (2) Compared with the existing thermal catalytic method, the method for oxidizing ethylene glycol to produce C3 products provided by the present invention uses ethylene glycol as the single raw material for the first time, avoiding product dehydration and generating products such as glyceric acid with higher economic value than lactic acid (the product of glyceraldehyde dehydration).

[0016] (3) The present invention not only provides a new green method for preparing C3 products such as glyceric acid, but also provides a new technical route for the preparation of long-chain compounds by extending carbon chains. Compared with other routes, the present invention does not require high temperature, high pressure, noble metals or strong alkaline conditions for catalysis, which is of great significance for solving energy and environmental problems and accelerating energy transformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The diagram shows the reaction mechanism of photoelectrocatalytic oxidation of ethylene glycol to glyceric acid.

[0018] Figure 2 This is a diagram of the Faradaic efficiency and yield of the reaction product at different potassium chloride concentrations obtained in Example 1.

[0019] Figure 3 This is the liquid phase mass spectrum of glyceric acid obtained in Example 1.

[0020] Figure 4 This is the liquid chromatography-mass spectra of glyceraldehyde and dihydroxyacetone obtained in Example 1.

[0021] Figure 5 This is a comparison chart of the Faraday efficiency and yield of the reaction products under the intrinsic bismuth vanadate (BVO) photoanode obtained in Example 3 and different composite photoanodes.

[0022] Figure 6 This is a comparison chart of the reaction product selectivity of the intrinsic bismuth vanadate (BVO) photoanode obtained in Example 3 and different composite photoanodes. DETAILED DESCRIPTION

[0023] In order to further understand the implementation method of the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described. At the same time, the examples described below are only part of the present invention and are not exhaustive. The following description is only intended to further illustrate the advantages and features of the present invention, and is not intended to limit the claims of the present invention. Other embodiments obtained by those of ordinary skill in the art without creative work are all within the scope of protection of the present invention.

[0024] The conditions for HPLC detection of ethylene glycol oxidation products are as follows:

[0025] The HPLC model used in the following examples was Agilent 1260 Infinity II Prime, the chromatographic column model used was Hi-plex H (300×d-7 mm, 8 μm), an ultraviolet detector (UV detector, VWD), 5 mM H 2 SO 4 as the mobile phase, a flow rate of 0.8 mL / min, and a temperature of 55° C. The products were quantitatively analyzed using an external standard curve.

[0026] Example 1

[0027] This embodiment provides a method for preparing glyceric acid by photoelectrocatalytic oxidation of ethylene glycol, which is achieved by the following steps:

[0028] Step 1, prepare a cobalt-iron bimetallic bismuth hydroxide vanadate (CoFeOOH / BVO) composite photoanode: use fluorine-doped tin oxide conductive glass (FTO) as a conductive substrate, and cut it to a size of 1 cm×2 cm, ultrasonically treat it in deionized water, acetone, and ethanol for 60 minutes, then dry it at 60°C for 60 minutes, and finally treat it in an O2 plasma cleaner for 60 minutes to obtain a treated conductive substrate; dissolve bismuth nitrate pentahydrate and potassium iodide in deionized water, stir evenly, and then use nitric acid to adjust the pH of the solution to 1.7 to prepare solution A, wherein the concentration of bismuth salt is 0.04M and the concentration of iodine salt is 0.4M; dissolve p-benzoquinone in ethanol to prepare solution B, wherein the concentration of p-benzoquinone is 0.4M; solutions A and B are mixed in a volume ratio of 5:2 to obtain an electrodeposition solution. A bismuth iodate (BiOI) precursor electrode was prepared using a conductive substrate as the working electrode. A bismuth iodate precursor (BiOI) was deposited at a constant potential of -0.1 V versus Ag / AgCl at room temperature for 200 s using an electrodeposition solution. Vanadyl acetylacetonate was dissolved in dimethyl sulfoxide to obtain solution C, where the vanadyl acetylacetonate concentration was 0.2 M. 50 μL of solution C was placed on the bismuth iodate precursor electrode, annealed at 450°C for 2 h, and then immersed in a 1 M sodium hydroxide solution for 40 min. The solution was then rinsed with deionized water and dried to obtain a BiVO4 photoanode. Ferric chloride and cobalt chloride were dissolved in an ethylene glycol solution, adjusted to pH 8, to obtain an impregnation solution. The ferric chloride and cobalt chloride concentrations in the impregnation solution were 0.02 M, and the ethylene glycol concentration was 1 M. The BiVO4 photoanode was then immersed in the impregnation solution and placed in an oven at 160°C for 4 h. Finally, the solution was rinsed with deionized water and ethanol, and dried to obtain a CoFeOOH / BVO composite photoanode.

[0029] Step 2: An ethylene glycol aqueous solution containing 0.1 M potassium chloride and 0.25 M potassium sulfate was used as the reaction solution, and the pH of the solution was adjusted to 12 with sodium hydroxide. The concentration of ethylene glycol in the reaction solution was 1 M. A CoFeOOH / BVO composite photoanode was used as the working electrode, a platinum wire was used as the counter electrode, and Hg / HgO was used as the reference electrode. The applied voltage was 1.2 V vs. RHE. At room temperature, under a simulated sunlight light source (300 W xenon lamp, light intensity of 100 mW / cm 2 ) was used to perform photoelectrocatalytic ethylene glycol oxidation. After 3 hours of reaction, the reaction solution was collected and analyzed by high-performance liquid chromatography to determine the Faradaic efficiency, selectivity, and yield of the generated glyceric acid, glyceraldehyde, and dihydroxyacetone. Under these reaction conditions, the Faradaic efficiency of ethylene glycol oxidation to glyceric acid reached 25%, and the glyceric acid yield reached 94.33 mmol·m -2 ·h -1 , and the total C3 yield was as high as 159.17 mmol·m -2 ·h -1Finally, the C3 products such as glyceric acid in the reaction products were further detected and identified by liquid chromatography-mass spectrometry (e.g. Figure 3-4 ), the results confirmed the formation of C3 species in the product.

[0030] Comparative Example 1

[0031] The same CoFeOOH / BVO composite photoanode as in Example 1 was used to carry out photoelectrocatalytic oxidation of ethylene glycol to produce C1 product. Specifically:

[0032] An ethylene glycol aqueous solution containing 0.1 M KOH was used as the reaction solution, wherein the ethylene glycol concentration was 1 M, a CoFeOOH / BVO composite photoanode was used as the working electrode, a platinum wire was used as the counter electrode, and Hg / HgO was used as the reference electrode. The applied voltage was 1.2 V vs. RHE. At room temperature, under a simulated sunlight light source (300 W xenon lamp, light intensity of 100 mW / cm 2 ) was used to carry out photoelectrocatalytic oxidation of ethylene glycol. After 3 hours of reaction, the reaction liquid was collected and tested by high performance liquid chromatography. The results showed that no C3 product was detected. Formic acid was the main product among the products, and the Faradaic efficiency reached 86%.

[0033] Comparative Example 2

[0034] The same CoFeOOH / BVO composite photoanode as in Example 1 was used to carry out photoelectrocatalytic oxidation of ethylene glycol to produce C2 products. Specifically:

[0035] An ethylene glycol aqueous solution containing 0.1 M potassium chloride and 0.25 M potassium sulfate was used as the reaction solution, and concentrated sulfuric acid was used to adjust the solution pH to 2. The concentration of ethylene glycol in the reaction solution was 1 M. The CoFeOOH / BVO composite photoanode was used as the working electrode, the platinum wire was used as the counter electrode, and the Ag / AgCl was used as the reference electrode. The applied voltage was 1.2 V vs. RHE. Under room temperature, under simulated sunlight light (300 W xenon lamp, light intensity of 100 mW / cm 2 ) was used to carry out photoelectrocatalytic ethylene glycol oxidation reaction. After 3 hours of reaction, the reaction liquid was collected and tested by high performance liquid chromatography. The results showed that no C3 product was detected. Among the products, ethanolaldehyde was the main product, and the Faradaic efficiency reached 69%.

[0036] Compared with Comparative Example 1, Example 1 and Comparative Example 1 both exhibit the presence of hydroxide ions in their reaction solutions. Ethylene glycol undergoes C-C bond cleavage under the combined action of the photoanode and hydroxide ions, generating a C1 intermediate. Simultaneously, the ethylene glycol in both reaction solutions is oxidized to a C2 intermediate, glycolaldehyde, via a two-electron transfer process. The difference in the final products between the two is due to the absence of potassium chloride in Comparative Example 1, which prevents the C2 intermediate from retaining its C2 skeleton and further undergoing C-C bond cleavage. This demonstrates that chloride ions can activate the C2 intermediate, making it easier for it to couple with the C1 intermediate and reducing the bond cleavage process of the C2 intermediate to generate the C1 intermediate.

[0037] Compared with Comparative Example 2, Example 1 differs in the reaction conditions in that the pH of the solution is changed. In other words, in Comparative Example 2, due to the lack of hydroxide ions, ethylene glycol in Comparative Example 2 is selectively oxidized to glycolaldehyde through a two-electron transfer process, and is unable to promote the cleavage of the C-C bond to accumulate the C1 intermediate. Although potassium chloride is added in Comparative Example 2, α-H activation of glycolaldehyde can occur. However, due to the lack of the C1 intermediate in Comparative Example 2, it is unable to undergo a coupling reaction to produce glyceraldehyde. Furthermore, due to the lack of hydroxide ions, glyceraldehyde cannot further produce C3 products such as glyceric acid or dihydroxyacetone under the action of hydroxide ions. This demonstrates that at a high pH value, sufficient hydroxide ions in the solution can promote the cleavage of the C-C bond of ethylene glycol, ensuring sufficient C1 intermediates for the coupling process. At the same time, hydroxide ions promote the α-H activation of glycolaldehyde to produce a coupling reaction, and under the synergistic effect of chloride ions, further produce C3 products.

[0038] In order to further analyze whether chloride ions have a significant effect on the formation of C3 products, the concentration of potassium chloride in the reaction solution was continuously adjusted while keeping other conditions unchanged, and the Faradaic efficiency and yield of the reaction products under different potassium chloride concentrations were obtained (see Figure 2). Figure 2 As can be seen from the figure, when the potassium chloride concentration increases from 0.01M to 0.05M, the Faradaic efficiency of C3 products such as glyceric acid increases significantly, indicating that chloride ions play an important mediating role in the formation of C3 products. At the same time, it can be found that with the increase of potassium chloride concentration, the total Faradaic efficiency of the products decreases slightly, which may be accompanied by the occurrence of other side reactions.

[0039] Example 2

[0040] This embodiment provides a method for preparing glyceric acid by photoelectrocatalytic oxidation of ethylene glycol, which is basically the same as that of Example 1, except that a BiVO4 photoanode (BVO) is used as the photoanode in this embodiment, and its preparation method is similar to step 1 in Example 1. The photoelectrocatalytic oxidation of ethylene glycol is carried out using the BiVO4 photoanode. After 3 hours of reaction, the reaction solution is collected and tested by high-performance liquid chromatography. The results show that the Faradaic efficiency of glyceric acid is 5%, and the glyceric acid yield reaches 14.71 mmol·m -2 ·h -1 , and the total C3 yield reached 55.86 mmol·m -2 ·h -1 .

[0041] In addition, based on the BiVO4 photoanode prepared in this embodiment, different MOOH / BVO composite photoanodes such as nickel cobalt bimetallic oxyhydroxide bismuth vanadate (NiCoOOH / BVO) composite photoanode, nickel oxyhydroxide bismuth vanadate (NiOOH / BVO) composite photoanode, iron oxyhydroxide bismuth vanadate (FeOOH / BVO) composite photoanode and cobalt oxyhydroxide bismuth vanadate (CoOOH / BVO) composite photoanode were prepared by changing the type of metal salt using an impregnation method. The reaction results of the BiVO4 photoanode in this embodiment were compared with those in Example 1. Figure 5 and Figure 6 As shown, it can be seen that: compared with the intrinsic bismuth vanadate photoanode, the Faradaic efficiency of the composite photoanode loaded with metal hydroxide oxide almost all reached more than 20%, among which the Faradaic efficiency of glyceric acid of the CoFeOOH / BVO composite photoanode reached 25%, and the total selectivity of C3 products also exceeded 50%. From this, it can be judged that the composite photoanode promotes the breakage of the CC bond and increases the formation of C1 intermediates, providing sufficient C1 intermediates for the coupling reaction, thereby greatly improving the Faradaic efficiency and selectivity of the ethylene glycol oxidation reaction to produce C3 products such as glyceric acid. This shows that the preparation of the composite photoanode greatly improves the selectivity of the ethylene glycol oxidation reaction to produce C3 products such as glyceric acid.

[0042] Example 3

[0043] This embodiment provides a method for preparing glyceric acid by photoelectrocatalytic oxidation of ethylene glycol, which is achieved by the following steps:

[0044] Step 1, prepare titanium dioxide (TiO2) photoanode: using the hydrothermal method, first 3mL of tetrabutyl titanate is mixed with 50mL of hydrochloric acid and 100mL of water, stirred for 3h, then 60mL of the solution is taken out and poured into a 100mL hydrothermal kettle; fluorine-doped tin oxide conductive glass (FTO) is used as the conductive substrate and cut to a size of 1cm×2cm, then the FTO is placed in the hydrothermal kettle filled with the solution, and finally the hydrothermal kettle is placed in a 220℃ oven for 24h, then taken out and rinsed with deionized water, dried at room temperature and placed in a 400℃ muffle furnace for annealing for 4h, and the TiO2 photoanode is obtained after annealing.

[0045] Step 2: 0.01M potassium chloride and 0.1M potassium sulfate in ethylene glycol aqueous solution were used as the reaction solution, and the pH of the solution was adjusted to 10 with sodium hydroxide. The concentration of ethylene glycol in the reaction solution was 0.1M. The TiO2 photoanode prepared in step 1 was used as the working electrode, the platinum wire was used as the counter electrode, and the Hg / HgO was used as the reference electrode. The applied voltage was 0.8V vs. RHE. At room temperature, the photoanode was subjected to a simulated sunlight light source (300W xenon lamp with a light intensity of 100mW / cm 2 ) was used for photoelectrocatalytic oxidation of ethylene glycol. After 3 h of reaction, the reaction solution was collected and subjected to high performance liquid chromatography to analyze the Faradaic efficiency and yield of the generated glyceric acid. The Faradaic efficiency of glyceric acid was 9%, and the glyceric acid yield was 5.7 mmol·m -2 ·h -1 .

[0046] Example 4

[0047] This embodiment provides a method for preparing glyceric acid by photoelectrocatalytic oxidation of ethylene glycol, which is achieved by the following steps:

[0048] Step 1, prepare tungsten oxide (WO3) photoanode: first, add 1g of ammonium metatungstate to 24mL of deionized water, stir for 10 minutes, add 2mL of HCl and 2mL of H2O2 in sequence and stir for 4h, then take 20mL of the solution and pour it into a 50mL reactor, use fluorine-doped tin oxide conductive glass (FTO) as the conductive substrate, and cut it to a size of 1cm×2cm, then put the FTO into the reactor containing the solution, and finally put the hydrothermal reactor into a 200℃ oven for 12h, then take it out and rinse it with deionized water, dry it at room temperature, and then anneal it in a 600℃ muffle furnace for 4h. After annealing, the WO3 photoanode is obtained.

[0049] Step 2: A 0.25 M potassium chloride and 0.25 M potassium sulfate ethylene glycol aqueous solution was used as the reaction solution, and the pH of the solution was adjusted to 12 using sodium hydroxide. The concentration of ethylene glycol in the reaction solution was 2 M. The WO3 photoanode prepared in step 1 was used as the working electrode, the platinum wire was used as the counter electrode, and the Hg / HgO was used as the reference electrode. The applied voltage was 1.2 V vs. RHE. At room temperature, the reaction was carried out under a simulated sunlight light source (300 W xenon lamp, light intensity of 100 mW / cm 2 ) was used for photoelectrocatalytic (PEC) oxidation of ethylene glycol. After 1 h of reaction, the reaction solution was collected and subjected to high performance liquid chromatography to analyze the Faradaic efficiency and yield of the generated glyceric acid. The Faradaic efficiency of glyceric acid was 10%, and the glyceric acid yield was 12.5 mmol·m -2 ·h -1 .

[0050] Example 5

[0051] This embodiment provides a method for preparing glyceric acid by photoelectrocatalytic oxidation of ethylene glycol. This embodiment uses an iron oxide (Fe2O3) photoanode and is implemented by the following steps:

[0052] Step 1, prepare iron oxide (Fe2O3) photoanode: first, add ferric chloride and urea to 40mL deionized water and stir thoroughly for 5h. The concentration of ferric chloride in the mixed solution is 0.4M and the concentration of urea is 0.3M. Then, take 20mL of the mixed solution and pour it into a 50mL reactor. Use fluorine-doped tin oxide conductive glass (FTO) as the conductive substrate and cut it to a size of 1cm×2cm. Then place FTO into the reactor containing the solution. Finally, place the hydrothermal reactor in a 200℃ oven for 24h, then take it out and rinse it with deionized water. After drying at room temperature, place it in a 600℃ muffle furnace for annealing for 3h. After annealing, the Fe2O3 photoanode is obtained.

[0053] Step 2: An ethylene glycol aqueous solution containing 0.13 M potassium chloride and 0.13 M potassium sulfate was used as the reaction solution, and the pH of the solution was adjusted to 14 using sodium hydroxide. The concentration of ethylene glycol in the reaction solution was 1 M. The photoanode prepared in step 1 was used as the working electrode, the platinum wire was used as the counter electrode, and the Hg / HgO was used as the reference electrode. At room temperature, the photoanode was used as the working electrode, the platinum wire was used as the counter electrode, and the Hg / HgO was used as the reference electrode. 2 ) was used for the photoelectrocatalytic (PEC) oxidation of ethylene glycol at an applied voltage of 1.4 V vs. RHE. After 4 h of reaction, the reaction solution was collected and analyzed by high-performance liquid chromatography. The Faradaic efficiency and yield of glyceric acid were analyzed, and the Faradaic efficiency of glyceric acid was 8%, and the glyceric acid yield was 6.8 mmol·m -2 ·h -1 .

[0054] The above-described embodiments merely represent implementation methods of the present invention and should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art may make various modifications and improvements without departing from the scope of the present invention, all of which fall within the scope of protection of the present invention.

Claims

1. A method for preparing glyceric acid by photoelectrocatalytic oxidation of ethylene glycol, characterized in that: The steps include: Step 1, preparing a photoanode; Step 2: Photoelectrocatalytic oxidation of ethylene glycol to C3 product: Add appropriate amounts of potassium chloride and potassium sulfate to an ethylene glycol aqueous solution, and adjust the solution pH to 10-14 with sodium hydroxide to prepare the reaction solution. Use the photoanode prepared in step 1 as the working electrode, platinum wire as the counter electrode, and Hg / HgO as the reference electrode. Apply a voltage of 0.8-1.4 V vs. RHE. At room temperature, carry out photoelectrocatalytic oxidation of ethylene glycol under simulated sunlight to prepare C3 product.

2. The method for preparing glyceric acid by photoelectrocatalytic oxidation of ethylene glycol according to claim 1, characterized in that: In step 1, the photoanode is selected from one of bismuth vanadate photoanode, titanium dioxide photoanode, tungsten oxide photoanode, iron oxide photoanode or a composite photoanode loaded with a promoter.

3. The method for preparing glyceric acid by photoelectrocatalytic oxidation of ethylene glycol according to claim 1 or 2, characterized in that: The photoanode is a metal hydroxide oxide bismuth vanadate composite photoanode.

4. The method for preparing glyceric acid by photoelectrocatalytic oxidation of ethylene glycol according to claim 3, characterized in that: The metal in the metal hydroxide oxyvanadate bismuth composite photoanode is selected from one or more of iron, nickel and cobalt.

5. The method for preparing glyceric acid by photoelectrocatalytic oxidation of ethylene glycol according to claim 3, characterized in that: The preparation method of the metal hydroxide oxybismuth vanadate composite photoanode is as follows: first, the bismuth vanadate photoanode is prepared by an electrochemical deposition method; and then the metal hydroxide oxybismuth vanadate photoanode is loaded on the surface of the bismuth vanadate photoanode by an impregnation method to obtain the metal hydroxide oxybismuth vanadate composite photoanode.

6. The method for preparing glyceric acid by photoelectrocatalytic oxidation of ethylene glycol according to claim 1, characterized in that: In step 2, the concentration of potassium chloride in the reaction solution is 0.01~0.25M, the concentration of potassium sulfate is 0.1~0.25M, and the concentration of ethylene glycol is 0.1~2M.

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