A method for photoelectrocatalytic cathode carbon dioxide reduction coupled with anodic glucose oxidation to simultaneously produce formic acid

Abstract

This invention discloses a method for photocatalytic carbon dioxide reduction coupled with glucose oxidation at the anode to simultaneously generate formic acid, belonging to the fields of photocatalytic technology and resource utilization of lead-containing waste batteries. The method uses lead formate recovered from lead-containing waste batteries as the lead source. A lead-modified layer with a coverage of 85%~95% and a preferred orientation of (111) crystal plane is constructed on the surface of a silicon electrode by photoelectrodeposition to obtain a Si-Pb photocathode. Pb3O4 anode material is obtained by calcining lead formate in an air atmosphere. The cathode and anode are placed in the cathode chamber and anode chamber of a two-chamber gas-phase flow photoelectrorea, respectively. Under AM 1.5 G standard sunlight irradiation, a photocatalytic coupling system is constructed. CO2 is continuously introduced into the cathode chamber for reduction, while glucose oxidation occurs in the anode chamber, achieving a dual-function synergistic preparation of formic acid. This invention realizes the green recycling and high-value utilization of lead resources from lead-containing waste batteries, possessing both resource recycling and energy conversion value.

Description

Technical Field

[0001] This invention belongs to the field of photoelectrocatalysis and resource recycling technology, specifically relating to a method for photoelectrocatalytic cathode carbon dioxide reduction coupled with anodic glucose oxidation to simultaneously generate formic acid. Background Technology

[0002] The greenhouse effect and energy crisis caused by excessive carbon dioxide (CO2) emissions have become major global challenges. Electrochemical reduction of CO2 (CO2RR) into high-value-added chemicals is one of the important pathways to achieving carbon neutrality. However, existing CO2RR technologies generally suffer from bottlenecks such as high cathode overpotential, poor product selectivity, and severe competing hydrogen evolution reaction (HER), which restricts their practical application. In recent years, researchers have proposed replacing the traditional anodic oxygen evolution reaction (OER) with organic oxidation reactions with lower thermodynamic potentials, constructing a bifunctional reaction system of cathode CO2 reduction coupled with anodic oxidation. Among them, glucose oxidation (GOR) has become an ideal alternative to OER due to its low theoretical oxidation potential (E° ≈ 0.05 V vs. RHE), mild reaction conditions, and wide availability of raw materials. This coupling strategy not only reduces the overall reaction voltage and energy consumption but also obtains high-value products simultaneously at both the cathode and anode, significantly improving the system's energy efficiency and economy.

[0003] Despite this, existing CO2RR systems still face many limitations: First, highly efficient catalysts often rely on precious metals such as gold and silver or complex nanotechnology synthesis processes, resulting in high costs and difficulty in scaling up. Second, anodic reactions are mostly limited to water oxidation, failing to fully utilize carbon-rich resources such as biomass. Third, the recycling of waste resources has not been effectively integrated, lacking environmentally friendly technological routes. Meanwhile, the industrial application of lead-acid batteries and perovskite solar cells has generated a large amount of lead-containing waste. Improper disposal of lead from waste batteries will cause serious soil and water pollution; traditional recycling processes are energy-intensive and cause significant secondary pollution. How to achieve safe and efficient recovery and high-value conversion of lead has become an urgent problem to be solved in the field of environmental governance and resource recycling. Existing research has attempted to recycle lead-containing waste using a composite system of citric acid (patent number CN101573461B), acetic acid, and sodium citrate (patent number CN113677812A). However, the systems used in these studies are complex and require additional separation and purification processes. In contrast, the lead formate extraction process developed in this application is simple, and the recovered liquid can be directly used for photoelectrode preparation. Furthermore, although existing research has attempted to utilize waste materials in the field of electrocatalysis (Sustainable Energy Fuels, 2024, 8, 3104–3112), no research has been reported on simultaneously achieving the synergistic production of formic acid from cathode CO2 reduction and anolyte biomass oxidation in a photoelectrocatalytic system, and converting waste lead resources from perovskite batteries into high-performance photoelectrodes. Therefore, developing a low-cost, low-energy-consumption, and sustainable photoelectrocatalytic system that can drive the conversion of CO2 into high-value chemicals such as formic acid, and synergistically process biomass feedstocks such as glucose and achieve high-value utilization of perovskite battery waste, has significant scientific and application value for promoting carbon neutrality goals and the development of a circular economy. Summary of the Invention

[0004] This invention provides a method for photocatalytic cathode carbon dioxide reduction coupled with anode glucose oxidation to simultaneously produce formic acid. The method includes: mechanically crushing lead-containing waste batteries to obtain mixed particles; immersing the mixed particles in an acid solution for a period of time; recovering and concentrating the mixture to obtain a lead salt solution; modifying the lead salt solution onto the surfaces of silicon and conductive glass electrode sheets using physicochemical methods to obtain a cathode and anode for the photoelectrochemical process; placing the cathode and anode materials in a two-chamber reactor with an optical window and separated by an ion-exchange membrane; applying light and potential; and performing glucose oxidation at the anode and carbon dioxide reduction at the cathode to jointly produce the final product, formic acid.

[0005] The lead-containing waste batteries mentioned are one or more of the following: perovskite batteries, lead-acid batteries, or lead-containing lithium-ion batteries. These batteries share the common characteristic of using lead as the primary raw material, making lead recycling necessary.

[0006] The mechanical crushing methods described include extrusion, impact, grinding, and ball milling. These methods are characterized by their ability to sufficiently destroy the encapsulation layer of the battery structure. In Comparative Example 1-1, the sample that was not mechanically crushed showed virtually no lead extraction effect.

[0007] In the acid leaching method for extracting lead, formic acid exhibits better selective extraction than aqua regia. Preferably, the formic acid concentration is 11–22 M. Comparative Examples 1-2 showed that formic acid had better selectivity than aqua regia. Comparative Examples 1-3 showed that even at formic acid concentrations below 11 M, good selective extraction was still achieved.

[0008] The preferred acid leaching time is 1–3 days, and the concentration of the concentrated lead salt solution after dissolution is 0.05–0.15 mM. In Comparative Examples 1–4, if the acid leaching time is less than 1 day, the dissolution concentration is too low, while if the acid leaching time is greater than 3 days, the byproduct Cu ions begin to dissolve.

[0009] The silicon-lead photocathode is prepared using a photoelectrochemical method. The preferred photoelectrode deposition potential is −0.5–−0.8V vs. Ag / AgCl, the illumination intensity is AM 1.5, and the total charge during the deposition process is 0.01–0.20 C. As shown in Example 1, the feature is that lead nanoparticles with a preferred orientation of (111) crystal planes are modified on the silicon surface, and the surface morphology has a coverage of 85%–95%.

[0010] The lead oxide photoanode is prepared on an electrode substrate by pyrolysis. The substrate is one of FTO conductive glass, ITO conductive glass, or carbon paper, and the loading method is one of drop coating, spin coating, or electrodeposition. Preferably, it is drop-coated on FTO conductive glass, and the concentration of the drop coating solution is 10 mg·mL⁻¹. −1 The drop volume was 100 μL. As shown in Example 2, the lead tetroxide prepared by this method consisted of nanoparticles with a particle size of approximately 150 nm. Preferably, the lead oxide photoanode was composed of lead tetroxide. As shown in Comparative Examples 2-1 and 2-2, the lead tetroxide photoanode exhibited the highest photoelectrocatalytic activity for the oxidation of glucose to formic acid.

[0011] The method for preparing formic acid using a silicon-based photocathode and a Pb3O4 photoanode includes using a silicon photoelectrode as the working electrode and a lead anode as the counter electrode in an H-type reactor. Preferably, the cathode chamber solution is a 0.2 M potassium bicarbonate solution saturated with carbon dioxide, continuously fed at a flow rate of 10–60 sccm. The anode chamber electrolyte is 0.2 M potassium bicarbonate; preferably, the glucose mixed solution concentration is 0.1 M. The H-type reactor is separated by an ion-exchange membrane. The reaction is conducted under AM 1.5 G standard sunlight, and the products are collected and analyzed. As shown in Example 3, this method successfully achieves the simultaneous production of formic acid from both the photocathode and photoanode.

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] 1. The Si-Pb photocathode prepared in this invention has lead nanoparticles with a surface coverage of 85%–95% and a crystal orientation of (111) loaded at its interface. By precisely controlling the experimental parameters, the photoelectrocatalytic performance can be optimized. At potentials as low as −0.4 V vs. RHE, this photocathode can achieve a Faraday efficiency of up to 100%, which is higher than the typical efficiency range (usually 40%–90%) of similar silicon-based photocathodes reported in the literature at similar potentials. This demonstrates a breakthrough performance improvement, reduces the reaction potential window, and achieves near-complete selectivity.

[0014] 2. The FTO-Pb3O4 photoanode prepared by this invention achieves a high Faradaic efficiency of 88% at a potential of +1.6 V vs. Ag / AgCl.

[0015] 3. This invention achieves closed-loop recycling and high-value reuse of valuable lead from waste lead-acid batteries, reducing catalyst raw material costs and resulting in significant economic benefits. It avoids the heavy metal pollution risks associated with direct lead mining and waste disposal, aligning with the development direction of green chemistry and a circular economy, and demonstrating outstanding environmental benefits.

[0016] 4. This invention constructs a symmetrical catalytic system in which formic acid can be produced at both the cathode and anode. The cathode produces formic acid by CO2 reduction, and the anode produces formic acid by glucose oxidation. The products have high added value, and the overall energy utilization rate of the system is better than that of the traditional water electrolysis system at the anode.

[0017] 5. Compared with pure electrocatalytic systems, which rely on external bias voltage to drive the reaction and have high energy consumption, the photoelectrocatalytic system used in this invention promotes efficient carrier separation through light energy excitation. While ensuring a high conversion rate, it reduces the power consumption in the reaction process, achieving synergistic optimization of energy utilization efficiency and catalytic performance, and demonstrating excellent energy-saving characteristics and green application potential. Attached Figure Description

[0018] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0019] Figure 1 The image shows a SEM image of the material obtained in Example 1. As can be seen from the image, the surface of the obtained Si-Pb photocathode consists of uniform lead micron-sized particles with a particle size of 1–2.5 μm.

[0020] Figure 2 The image shows the XRD pattern of the material obtained in Example 1. As can be seen from the image, the surface of the obtained Si-Pb photocathode has characteristic peaks corresponding to the silicon and lead (111) crystal planes, which proves that lead grows with a preferred orientation on the (111) crystal plane.

[0021] Figure 3 The bar chart shows the Faraday efficiency of various products when a gradient bias voltage is applied to the material obtained in Example 1. As can be seen from the figure, the obtained silicon-based photocathode exhibits excellent performance in the synthesis of formic acid, achieving a formic acid Faraday efficiency of 100% at a potential of −0.4 V vs. RHE.

[0022] Figure 4 The H-NMR spectrum of the Si-Pb cathode reaction product obtained in Example 1 confirms the formation of formic acid.

[0023] Figure 5 The extraction effect of lead and copper from waste perovskite batteries in Example 1 after soaking in formic acid for 2 days demonstrates that formic acid soaking can achieve highly selective extraction of lead.

[0024] Figure 6 The results of lead and copper extraction from waste perovskite batteries in Examples 1-2 after soaking in aqua regia for 2 days demonstrate that the selectivity of lead extraction by soaking in aqua regia is not as good as that of formic acid.

[0025] Figure 7 The results show the trend of lead and copper extraction efficiency with acid leaching time, indicating that the optimal acid leaching time is 1-3 days.

[0026] Figure 8 This is a TEM image of Pb3O4 obtained in Example 2. As can be seen from the image, the obtained Pb3O4 powder consists of nano-sized particles.

[0027] Figure 9 The image shows the XRD pattern of Pb3O4 obtained in Example 2, confirming that the prepared material is Pb3O4.

[0028] Figure 10 The H-NMR spectrum of the liquid phase product obtained from the FTO-Pb3O4 anode in Example 2 after 1 hour of reaction confirms the formation of formic acid.

[0029] Figure 11 The XRD pattern of PbO obtained in Comparative Example 2-1 confirms that the prepared material is PbO.

[0030] Figure 12 The XRD pattern of PbO2 obtained in Comparative Example 2-2 confirms that the prepared material is PbO2.

[0031] Figure 13 This is a comparison of the Faradaic efficiencies of the anolyte materials PbO, PbO2, and Pb3O4 obtained in Example 2, Comparative Example 2-1, and Comparative Example 2-2 for the target product formic acid. The graph shows that Pb3O4 exhibits the highest glucose oxidation activity (FE = 88%), superior to PbO and PbO2. This indicates that the mixed valence states of Pb(II) and Pb(IV) are favorable for the selective oxidation of glucose to formic acid.

[0032] Figure 14 This is a schematic diagram of the reaction system for the simultaneous production of formic acid using a silicon lead photocathode and a lead tetroxide photoanode as described in Example 3.

[0033] Figure 15 The analysis results of formic acid products from the simultaneous production of formic acid using the lead silicon photocathode and lead tetroxide photoanode described in Example 3 prove that the simultaneous production of formic acid using the photocathode and photoanode has been successfully achieved. Detailed Implementation

[0034] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. 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. These all fall within the scope of protection of the present invention.

[0035] Example 1

[0036] This embodiment relates to the recovery of lead from spent perovskite batteries and the preparation of a Si-Pb photocathode, and tests its photoelectrocatalytic CO2 reduction performance. The method includes the following steps:

[0037] (1) Recycling of lead from waste perovskite batteries: Cut waste perovskite batteries into pieces with an area of ​​approximately 1 cm². 2 Small pieces of lead were soaked in 50 mL of formic acid for 2 days at room temperature, and the resulting lead formic acid solution was recovered with a concentration of 0.05 mM ~ 0.15 mM.

[0038] (2) Preparation of Si-Pb photocathode: The p-type silicon wafer was ultrasonically cleaned with acetone, ethanol, and deionized water for 15 min each, then soaked in 5 wt% hydrofluoric acid for 10 min to remove the surface oxide layer, and dried with nitrogen gas for later use. The pretreated silicon electrode was placed in the lead formate solution obtained in step (1), and a three-electrode system was used (silicon electrode as working electrode, Ag / AgCl as reference electrode, and platinum wire as counter electrode). The electrode was kept at a constant potential of −0.5 V vs. Ag / AgCl and 100 mW·cm⁻¹. −2 Photoelectrodeposition was performed under simulated sunlight (AM 1.5G) irradiation, with the deposition charge controlled at 0.1875C, resulting in a loading of 0.45 mg·cm⁻¹. −2 Si-Pb cathode.

[0039] (3) Photoelectrocatalytic CO2 reduction performance test: The Si-Pb cathode obtained in step (2) was used as the working electrode, the saturated silver / silver chloride electrode as the reference electrode, and the platinum wire electrode as the counter electrode to build a three-electrode reaction system in an H-type reactor. 50 mL of 0.2 M potassium bicarbonate solution saturated with carbon dioxide was continuously introduced into the cathode chamber at a flow rate of 30 sccm; 50 mL of 0.2 M potassium bicarbonate solution was added to the anode chamber. The H-type reactor was separated by a proton exchange membrane. Under AM1.5 G standard sunlight irradiation, a constant potential current-time test was performed at −0.4 V vs. RHE potential for 1 h. The products in the cathode chamber were collected and analyzed.

[0040] Figure 1 The image shows a SEM image of the Si-Pb cathode obtained in Example 1. As can be seen from the image, lead particles are uniformly distributed on the surface of the obtained silicon-based photocathode, with a coverage of approximately 85%, and the particle size is in the micrometer range. Figure 2 The image shows the XRD pattern of the Si-Pb cathode obtained in Example 1. As can be seen from the image, the surface of the obtained silicon-based photocathode has characteristic peaks corresponding to the silicon and lead (111) crystal planes, which proves that lead grows with a preferred orientation on the (111) crystal plane. Figure 3 The bar chart shows the Faraday efficiency of various products when a gradient bias voltage is applied to the material obtained in Example 1. As can be seen from the figure, the obtained silicon-based photocathode exhibits excellent performance in the synthesis of formic acid, achieving a formic acid Faraday efficiency of 100% at a potential of −0.4 V vs. RHE. Figure 4 The H-NMR spectrum of the Si-Pb cathode reaction product obtained in Example 1 confirms the formation of formic acid. Figure 5 This study investigated the extraction efficiency of lead and copper from spent perovskite batteries after soaking them in formic acid for two days. The results showed a lead-to-copper concentration ratio of 3.9, indicating that formic acid can selectively extract lead.

[0041] Comparative Example 1-1

[0042] The comparative method is the same as in Example 1, except that the waste perovskite battery in step (1) was not mechanically crushed. The results show that there is basically no lead extraction effect.

[0043] Comparative Examples 1-2

[0044] The comparative method is the same as in Example 1, except that in step (1), the waste perovskite battery after cutting is soaked in aqua regia. Figure 6 The extraction efficiency of lead and copper from waste perovskite batteries after soaking in aqua regia for 2 days was investigated. The results showed a lead-to-copper concentration ratio of 1.7, indicating that aqua regia was less selective for lead extraction than formic acid.

[0045] Comparative Examples 1-3

[0046] The comparative method is the same as in Example 1, except that in step (1), the cut waste perovskite batteries were soaked in formic acid at a concentration of 5 M. The results show that even when the formic acid concentration is below 11 M, it still exhibits good selective extraction.

[0047] Comparative Examples 1-4

[0048] The comparative method is the same as in Example 1, except that the soaking time in step (1) is 11 days. Figure 7 The extraction efficiency of lead and copper varies with acid leaching time. The results show that when the acid leaching time is less than 1 day, the lead leaching concentration is too low, while when the acid leaching time is greater than 3 days, the leaching of the byproduct Cu increases.

[0049] Example 2

[0050] This embodiment relates to the preparation of an FTO-Pb3O4 photoanode and tests its photocatalytic glucose oxidation performance. The method includes the following steps:

[0051] (1) Preparation of Pb3O4 powder: Commercial lead formate powder was placed in a tube furnace and heated at 4℃·min under air atmosphere. −1 The temperature was increased to 470 °C at a certain rate, held for 2 h, and then naturally cooled to room temperature to obtain Pb3O4 powder.

[0052] (2) Preparation of FTO-Pb3O4 photoanode: The catalyst powder prepared in step (1) was dispersed in ethanol to prepare a 10 mg·mL⁻¹ solution. −1 The suspension was ultrasonically dispersed for 30 min. 100 μL was dropped onto the surface of FTO conductive glass (1 cm × 2 cm) and dried at room temperature to obtain an FTO-Pb3O4 photoanode.

[0053] (3) Photocatalytic glucose oxidation performance test: The FTO-Pb3O4 anode obtained in step (2) was used as the working electrode, the Ag / AgCl electrode as the reference electrode, and the platinum wire electrode as the counter electrode to build a three-electrode reaction system in an H-type reactor. 50 mL of a mixed solution of 0.2 M potassium bicarbonate and 0.1 M glucose was added to the anode chamber; 50 mL of 0.2 M potassium bicarbonate solution was added to the cathode chamber. The H-type reactor was separated by a proton exchange membrane. Under AM 1.5 G standard sunlight irradiation, a constant potential current-time test was performed at a potential of +1.4 V to +1.8 V vs. Ag / AgCl for 1 h. The product in the anode chamber was collected and analyzed.

[0054] Figure 8 The image shows a TEM image of Pb3O4 obtained in Example 2. As can be seen from the image, the obtained Pb3O4 powder consists of nanoparticles with a particle size of approximately 150 nm. Figure 9 The image shows the XRD pattern of Pb3O4 obtained in Example 2, confirming that the prepared material is Pb3O4. Figure 10 The image shows the 1H NMR spectrum of the liquid phase product obtained from the FTO-Pb3O4 anode in Example 2 after 1 hour of reaction, confirming the formation of formic acid.

[0055] Comparative Example 2-1

[0056] The comparative method is the same as in Example 2, except that the calcination temperature in step (1) is 500℃. This yields lead oxides (PbO) in different oxidation states, and the effect of lead oxidation state on the photoelectrocatalytic oxidation performance of glucose is investigated.

[0057] Figure 11 The XRD pattern of PbO obtained in Comparative Example 2-1 confirms that the prepared material is PbO.

[0058] Comparative Example 2-2

[0059] The comparative method is the same as in Example 2, except that commercially available PbO2 powder is used directly in step (1). This yields lead oxides (PbO2) in different oxidation states, and the effect of lead oxidation state on the photoelectrocatalytic oxidation performance of glucose is investigated.

[0060] Figure 12 The XRD pattern of PbO2 obtained in Comparative Example 2-2 confirms that the prepared material is PbO2. Figure 13This is a comparison of the Faradaic efficiencies of the PbO, PbO2, and Pb3O4 anode materials obtained in Example 2, Comparative Example 2-1, and Comparative Example 2-2 for the target product formic acid. The graph shows that Pb3O4 exhibits the highest glucose oxidation activity (FE = 88%), superior to PbO and PbO2. This indicates that the mixed valence states of Pb(II) and Pb(IV) are favorable for the selective oxidation of glucose to formic acid.

[0061] Example 3

[0062] This embodiment relates to a method for preparing formic acid by jointly using a silicon-based photocathode and a Pb3O4 photoanode through a photocatalytic full-reaction process. The method includes the following steps:

[0063] (1) Using the Si-Pb photocathode obtained in Example 1 as the working electrode and the FTO-Pb3O4 anode obtained in Example 2 as the counter electrode, a two-electrode reaction system was constructed in an H-type reactor. 50 mL of a mixed solution of 0.2 M potassium bicarbonate and 0.1 M glucose was added to the anode chamber; 50 mL of CO2-saturated 0.2 M potassium bicarbonate solution was added to the cathode chamber, and CO2 was continuously introduced at 10-60 sccm. The H-type reactor was separated by a proton exchange membrane. Both the photoelectrode and photoanode were irradiated with AM 1.5 G standard sunlight, and a constant potential current-time test was performed for 10 h at a bias voltage of −2.6 V. The products in the cathode and anode chambers were collected every hour, and the products were analyzed.

[0064] Figure 14 This is a schematic diagram of the reaction system in Example 3. Figure 15 The photocurrent density and total Faraday efficiency of the formic acid products in the entire reaction process of Example 3 are given.

[0065] Product analysis methods

[0066] The specific steps for determining formic acid by ¹H-NMR are as follows:

[0067] (1) Take 600 μL of the test solution after the reaction, and add 60 μL of solution containing 1 μmol·mL⁻¹ −1 The dimethyl sulfoxide (DMSO) deuterium water (D2O) solution was used as an internal standard and mixed thoroughly.

[0068] (2) Transfer the mixed solution to an NMR tube and test it using an NMR spectrometer.

[0069] (3) The concentration of formic acid was calculated by combining the peak area at the characteristic chemical shift of formic acid (approximately 8.33 ppm) with the peak area of ​​the internal standard DMSO and the standard curve.

[0070] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for photocatalytic cathode carbon dioxide reduction coupled with anodic glucose oxidation to simultaneously generate formic acid, characterized in that, include: Lead-containing waste batteries are mechanically crushed to obtain mixed particles, which are then soaked in an acid solution for a period of time. The resulting lead salt solution is recovered and concentrated. This lead salt solution is then modified onto the surfaces of silicon and conductive glass electrode sheets using physicochemical methods to obtain cathodes and anodes for photoelectrochemical processes. The cathode and anode materials are then placed in a two-chamber reactor with an optical window and separated by an ion-exchange membrane. Irradiation and potential are applied, and the anode realizes the glucose oxidation process, while the cathode realizes the carbon dioxide reduction process, jointly producing the final product formic acid.

2. The method for photocatalytic cathode carbon dioxide reduction coupled with anodic glucose oxidation to simultaneously generate formic acid according to claim 1, characterized in that, The lead-containing waste batteries are one or more of perovskite batteries, lead-acid batteries, or lead-containing lithium-ion batteries, and the mechanical crushing methods include extrusion, impact, grinding, ball milling, etc.

3. The method for photocatalytic cathode carbon dioxide reduction coupled with anode glucose oxidation to simultaneously generate formic acid according to claim 1, characterized in that, The acid solution can selectively dissolve lead, with formic acid being the preferred result, whereas aqua regia of the same concentration cannot selectively dissolve lead.

4. The method for photocatalytic cathode carbon dioxide reduction coupled with anodic glucose oxidation to simultaneously generate formic acid according to claim 3, characterized in that, The formic acid concentration is 11–22 M, the acid leaching time is 1–3 days, and the concentration of the recovered lead salt solution is 0.05–0.15 mM.

5. The method for photocatalytic cathode carbon dioxide reduction coupled to anode glucose oxidation to simultaneously generate formic acid according to claim 1, characterized in that, The silicon-lead photocathode is prepared by photoelectrodeposition. The photoelectrodeposition potential is preferably −0.5–−0.8 V vs. Ag / AgCl, the light intensity is AM 1.5 G, and the total charge during the deposition process is 0.01–0.20 C. Preferably, the lead crystal surface exposed by the electrode is (111).

6. The method for photocatalytic cathode carbon dioxide reduction coupled to anode glucose oxidation to simultaneously generate formic acid according to claim 1, characterized in that, The lead anode is prepared on an electrode substrate by pyrolysis. The substrate is one of FTO conductive glass, ITO conductive glass or carbon paper, and the precursor is loaded by one of drop coating, spin coating or electrodeposition.

7. The method for preparing a lead anode according to claim 6, characterized in that, Preferably, the solution is drop-coated onto FTO conductive glass, and the concentration of the drop-coating solution is 10 mg·mL. −1 The drop volume was 100 μL, the pyrolysis temperature was 450℃ – 500℃, and the pyrolysis atmosphere was air.

8. The method for photocatalytic cathode carbon dioxide reduction coupled to anode glucose oxidation to simultaneously generate formic acid according to claim 1, characterized in that, Under AM 1.5 G standard sunlight, a two-chamber gas-phase flow photoreactor was used with a two-electrode reaction system. The cathode chamber electrode was a silicon lead photocathode, and the electrolyte was a 0.2 M potassium bicarbonate solution saturated with continuously introduced carbon dioxide. The anode chamber electrode was a lead oxide anode, and the electrolyte was a mixed solution of 0.2 M potassium bicarbonate and 0.1 M glucose.

9. The method for photocatalytic cathode carbon dioxide reduction coupled to anode glucose oxidation to simultaneously generate formic acid according to claim 8, characterized in that, The rate at which carbon dioxide is continuously introduced into the electrolyte in the cathode chamber is 10-60 sccm, and the introduction continues after the carbon dioxide reaches saturation.

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