Preparation method and application of cerium-cobalt composite oxide electrocatalyst

Abstract

The present application relates to a kind of cerium cobalt composite oxide electrocatalyst preparation method, it includes the following steps: soluble cerium salt, soluble cobalt salt and urea are added to water, stirring to form mixed solution, wherein, cerium ion concentration is 4 ~ 95mmol / L, cobalt ion concentration is 40 ~ 60mmol / L, the total amount of metal of the soluble cobalt salt and soluble cerium salt and the molar ratio of urea is (0.01 ~ 0.5) : 1;The mixed solution and carbon fiber base are added to closed container, keep 2 ~ 24h at 100 ~ 160 ℃, cool to room temperature, obtain the carbon fiber base of supported catalyst precursor;The carbon fiber base of the supported catalyst precursor is dried, calcination, calcination temperature 300 ~ 500 ℃, calcination time is 1 ~ 4h, the heating rate is 1 ~ 5 ℃ / min, obtain cerium cobalt composite oxide electrocatalyst.This synthesis method is simple, low in cost, suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalysis technology, and relates to a method for preparing a cerium-cobalt composite oxide electrocatalyst and its application in the oxidation of glycerol. Background Technology

[0002] Glycerol, a C3 platform molecule, is a major byproduct of biodiesel production. Selective oxidation of glycerol yields many high-value-added products, including dihydroxyacetone, glyceric acid, tartaric acid, mesooxalic acid, glycolic acid, and formic acid. Unlike traditional thermocatalytic glycerol oxidation (GOR), electrocatalytic GOR is a promising approach that can be carried out at moderate temperatures and atmospheric pressures with low cost and high efficiency. Furthermore, by controlling the catalyst composition and reaction variables such as electrode potential, electrolyte pH, glycerol concentration, reaction temperature, and reaction time, the product formation pathway can be well controlled, improving product selectivity. Its only drawback is that the reaction often requires a high overpotential, necessitating significant energy consumption for large-scale production. However, this overpotential can be reduced by rationally designing the catalyst structure to synthesize highly active and selective catalysts with specific surface compositions and morphologies.

[0003] The key to the selective oxidation of glycerol lies in the design and development of highly efficient catalysts. To explore cleaner and more efficient methods for the oxidation and value-added conversion of glycerol, many chemical researchers have conducted extensive research and experimentation. Under typical electrolysis conditions, noble metal (Au, Pt, Pd)-based catalysts exhibit excellent adsorption capacity for glycerol. At relatively low potential environments, they can guide the electro-oxidation reaction of glycerol, greatly improving the selectivity of the reaction. Particularly noteworthy is the high selectivity of noble metals in the selective electrocatalytic oxidation of glycerol to glycolic acid, producing this high-value-added product. However, noble metals are not only expensive, but they can typically only produce high-value products at low potentials and relatively small currents. At high potentials, they are easily over-oxidized to carbon dioxide and are easily poisoned and deactivated by highly coordinated species generated during the glycerol oxidation process.

[0004] Therefore, developing resource-rich, low-cost, high-performance, and stable electrocatalysts is of great significance for the efficient electro-oxidation of glycerol to C2 products. Summary of the Invention

[0005] In view of the above-mentioned problems in the prior art, the purpose of this invention is to provide a method for preparing cerium-cobalt composite oxide electrocatalysts and their applications.

[0006] This invention provides a method for preparing a cerium-cobalt composite oxide electrocatalyst, comprising the following steps:

[0007] Soluble cerium salt, soluble cobalt salt, and urea are added to water and stirred to form a mixture, wherein the concentration of cerium ions is 4-95 mmol / L, the concentration of cobalt ions is 40-60 mmol / L, and the molar ratio of the total metal content of the soluble cobalt salt and soluble cerium salt to urea is (0.01-0.5):1.

[0008] The mixture and carbon fiber substrate were added to a sealed container and kept at 100-160°C for 2-24 hours. After cooling to room temperature, a carbon fiber substrate with a supported catalyst precursor was obtained.

[0009] The carbon fiber substrate of the supported catalyst precursor is dried and calcined at a temperature of 300–500°C for 1–4 h at a heating rate of 1–5°C / min to obtain the cerium-cobalt composite oxide electrocatalyst.

[0010] The present invention also provides the application of the cerium-cobalt composite oxide electrocatalyst obtained by the above method in the electrocatalytic oxidation of glycerol.

[0011] Compared with existing technologies, the present invention has the following beneficial effects:

[0012] (1) The electrocatalyst preparation method proposed in this invention is an in-situ growth method, which can prepare composite electrocatalysts with uniform nanofiber morphology. The synthesis method is simple and suitable for large-scale production. It solves the problem that traditional hydrothermal methods are difficult to grow cerium metal on carbon fiber substrates. Cobalt metal can be used to synergistically promote directional growth on the surface of carbon paper fibers.

[0013] (2) The carbon fiber substrate has excellent electrical conductivity. In the electrocatalysis process, good conductivity can ensure that electrons can be transported efficiently between the electrode (based on carbon fiber) and the electrocatalyst, reducing energy loss during electron transport and making it more stable and efficient.

[0014] (3) Rare earth cerium oxides have a unique 4f electronic structure. When combined with transition metal oxides, they can regulate the d-band center, improve the adsorption of the catalyst and substrate and the desorption of the product in the catalytic reaction, and increase the electron transfer rate and improve the electrolysis efficiency.

[0015] (4) This catalyst exhibits excellent electrocatalytic activity for glycerol. During the oxidation of glycerol, the catalyst requires only 1.38 V (vs. RHE) to achieve 10 mA·cm⁻¹. -2 The starting current density is lower than that of the anodic oxygen evolution reaction, reducing the overpotential by 100mV; and the analysis of the electrolysis products by chronoamperometry shows that the catalyst has high selectivity and Faraday efficiency for C2 products.

[0016] (5) The catalyst also has excellent recycling performance. After running at a potential of 1.4V (vs. RHE) for 10 hours and being recycled 3 times, the catalyst's catalytic performance did not show significant decay and its stability was good.

[0017] (6) Compared with the previously reported selectivity of precious metal catalysts such as AuCu alloy in the electrocatalytic reaction of glycerol to glycolic acid, the catalyst prepared in this invention not only exhibits higher selectivity in the reaction, but also significantly reduces costs, showing significant advantages in terms of economy and performance. Attached Figure Description

[0018] Figure 1 This is a scanning electron microscope image of the cerium-cobalt composite oxide electrocatalyst obtained in Example 1 of the present invention.

[0019] Figure 2 This is a scanning electron microscope image of the cerium-cobalt composite oxide electrocatalyst obtained in Example 2 of the present invention.

[0020] Figure 3 This is a scanning electron microscope image of the cerium-cobalt composite oxide electrocatalyst obtained in Example 3 of the present invention.

[0021] Figure 4 This is a scanning electron microscope image of the cobalt oxide electrocatalyst obtained in Comparative Example 1 of the present invention.

[0022] Figure 5 The image shows the XRD phase diagram of the cerium-cobalt composite oxide electrocatalyst of Example 1 of this invention.

[0023] Figure 6 The image shows the XRD phase diagram of the cobalt oxide electrocatalyst obtained in Comparative Example 1 of this invention.

[0024] Figure 7 This is a scanning electron microscope image of the gadolinium-cobalt composite oxide electrocatalyst obtained in Comparative Example 2 of the present invention.

[0025] Figure 8 The LSV curve of the cerium-cobalt composite oxide electrocatalyst obtained in Example 1 of this invention applied to the electrocatalytic oxidation of glycerol.

[0026] Figure 9 The diagram shows the cycle performance of the cerium-cobalt composite oxide electrocatalyst obtained in Example 1 of this invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0028] This invention provides a method for preparing a cerium-cobalt composite oxide electrocatalyst, comprising the following steps:

[0029] S01: Add soluble cerium salt, soluble cobalt salt and urea to water and stir to form a mixture, wherein the concentration of cerium ions is 4-95 mmol / L and the concentration of cobalt ions is 40-60 mmol / L, and the molar ratio of the total metal content of the soluble cobalt salt and soluble cerium salt to urea is (0.01-0.5):1.

[0030] S02: The mixture and carbon fiber substrate are added to a sealed container and kept at 100-160°C for 2-24 hours. After cooling to room temperature, a carbon fiber substrate with a supported catalyst precursor is obtained.

[0031] S03: The carbon fiber substrate of the supported catalyst precursor is dried and calcined at a temperature of 300-500℃ for 1-4 hours and a heating rate of 1-5℃ / min to obtain the cerium-cobalt composite oxide electrocatalyst.

[0032] Specifically, in step S01, the soluble cerium salt is cerium chloride or cerium nitrate, and the soluble cobalt salt is cobalt chloride or cobalt nitrate, which may or may not contain water of crystallization. Preferably, the concentration of cerium ions is 20–55 mmol / L. The molar ratio of the total metal content of the soluble cobalt salt and soluble cerium salt to urea is (0.01–0.5):1, for example, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, etc. Preferably, the molar ratio of the total metal content of the soluble cobalt salt and soluble cerium salt to urea is (0.05–0.4):1.

[0033] In step S02, the carbon fiber substrate can be carbon cloth, carbon paper, or other carbon fiber substrates. Preferably, it is carbon fiber paper. The carbon fiber substrate is cut to the required size, ultrasonically cleaned in ethanol and water for 10 minutes to remove impurities from the surface, dried in an 80°C oven, and then calcined in an air atmosphere in a muffle furnace for 2 hours to obtain a pretreated carbon paper fiber substrate. The calcination temperature of the carbon fiber substrate is 200–400°C, for example, 200°C, 250°C, 300°C, 350°C, or 400°C, preferably 250°C–300°C. The calcination time is 1–4 hours, for example, 1 hour, 2 hours, 3 hours, or 4 hours, preferably 1 hour to 2 hours.

[0034] Specifically, the mixture is transferred to a sealed container, the pretreated substrate is added, and the mixture is heated to 120-140°C for 6-12 hours to obtain a carbon fiber substrate with a supported catalyst precursor; the sealed container can be a hydrothermal reactor.

[0035] In step S03, specifically, the carbon fiber substrate of the supported catalyst precursor is calcined in an air atmosphere at 300°C to 500°C to obtain the cerium-cobalt composite oxide electrocatalyst.

[0036] The calcination temperature is 300-500℃, such as 300℃, 350℃, 400℃, 450℃, 500℃, etc. Preferably, the calcination temperature is 350-400℃, and the calcination time is 1h-4h, such as 1h, 2h, 3h, 4h, etc., preferably 1h-2h.

[0037] The present invention also provides the application of the cerium-cobalt composite oxide electrocatalyst prepared by the above method in the electrocatalytic oxidation of glycerol.

[0038] Specifically, the prepared cerium-cobalt composite oxide electrocatalyst was used as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, and a three-electrode system was assembled for glycerol oxidation.

[0039] Optionally, the electrolyte used in the electrocatalytic oxidation of glycerol is an alkaline solution of glycerol, which can be a mixed solution of glycerol and potassium hydroxide. The concentration of glycerol is 0.1–2 mol / L, for example, 0.1, 0.2, 0.3, 0.5, 0.6, 0.8, 1, 1.5, or 2 mol / L, preferably 0.3–0.5 mol / L. The concentration of potassium hydroxide is 1 mol / L.

[0040] The following specific examples illustrate the preparation method of cerium-cobalt composite oxide electrocatalysts and their application in the electrocatalytic oxidation of glycerol. The self-supporting electrodes in the examples below can be prepared directly using existing methods, or they can be purchased directly from the market; they are not limited to this method.

[0041] Example 1 :

[0042] Preparation of cerium-cobalt composite oxide electrocatalysts:

[0043] The carbon paper was cut into 1×2cm pieces, ultrasonically cleaned in ethanol and water for 10 minutes to remove impurities from the surface of the carbon paper fibers, dried in an 80℃ oven, and then calcined in an air atmosphere at 250℃ for 2 hours to obtain a pretreated carbon fiber substrate.

[0044] Weigh 0.8 mmol CeCl3 and 0.8 mmol CoCl2·6H2O into a 100 mL beaker, add 0.5 g urea and 17 mL water, and stir until a transparent pink solution is formed.

[0045] Transfer the above uniform and transparent solution to a 25mL polytetrafluoroethylene-lined stainless steel high-pressure hydrothermal reactor, add the pretreated carbon fiber paper at the same time, place it in an oven at 120℃ for 6 hours, and after the reaction is completed, place the hydrothermal reactor to cool to room temperature.

[0046] The carbon paper with the precursor was removed, rinsed repeatedly with deionized water and ethanol, dried in an 80℃ oven for 6 hours, and then calcined in a muffle furnace at a temperature of 350℃ for 2 hours with a heating rate of 2.5℃ / min to obtain a cerium-cobalt composite oxide electrocatalyst uniformly grown on the carbon paper substrate.

[0047] Electrocatalytic oxidation of glycerol:

[0048] A three-electrode system was used to evaluate the reaction performance of the prepared cerium-cobalt composite oxide electrocatalyst. The prepared electrocatalyst was used as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. The electrolyte was a 0.3 mol / L glycerol solution in 1 mol / L potassium hydroxide solution. The selective oxidation performance of the catalyst was tested at room temperature by chronoamperometry (1.4 V) with a charge of 100C. The products were detected by liquid chromatography, and the selectivity for glycolic acid was 42%, the selectivity for glyceric acid was 13%, and the selectivity for formic acid was 45%.

[0049] Example 2 :

[0050] Preparation of cerium-cobalt composite oxide electrocatalysts:

[0051] The carbon paper was cut into 1×2cm pieces, ultrasonically cleaned in ethanol and water for 10 minutes to remove impurities from the surface of the carbon paper fibers, dried in an 80℃ oven, and then calcined in an air atmosphere at 250℃ for 2 hours to obtain a pretreated carbon fiber substrate.

[0052] Weigh 0.08 mmol CeCl3 and 0.8 mmol CoCl2·6H2O into a 100 mL beaker, add 0.5 g urea and 17 mL water, and stir until a transparent pink solution is formed.

[0053] Transfer the above uniform and transparent solution to a 25mL polytetrafluoroethylene-lined stainless steel high-pressure hydrothermal reactor, add the pretreated carbon fiber paper at the same time, place it in an oven at 120℃ for 6 hours, and after the reaction is completed, place the hydrothermal reactor to cool to room temperature.

[0054] The carbon paper with the precursor was removed, rinsed repeatedly with deionized water and ethanol, dried in an 80℃ oven for 6 hours, and then calcined in a muffle furnace at a temperature of 350℃ for 2 hours with a heating rate of 2.5℃ / min to obtain a cerium-cobalt composite oxide electrocatalyst uniformly grown on the carbon paper substrate.

[0055] Electrocatalytic oxidation of glycerol:

[0056] A three-electrode system was used to evaluate the reaction performance of the prepared cerium-cobalt composite oxide electrocatalyst. The prepared electrocatalyst was used as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. The electrolyte was a 0.3 mol / L glycerol solution in 1 mol / L potassium hydroxide solution. The selective oxidation performance of the catalyst was tested at room temperature by chronoamperometry (1.4 V) with a charge of 100C. The products were detected by liquid chromatography, and the selectivity for glycolic acid was 38%, the selectivity for glyceric acid was 7%, and the selectivity for formic acid was 55%.

[0057] Example 3 :

[0058] Preparation of cerium-cobalt composite oxide electrocatalysts:

[0059] The carbon paper was cut into 1×2cm pieces, ultrasonically cleaned in ethanol and water for 10 minutes to remove impurities from the surface of the carbon paper fibers, dried in an 80℃ oven, and then calcined in an air atmosphere at 250℃ for 2 hours to obtain a pretreated carbon fiber substrate.

[0060] Weigh 1.6 mmol CeCl3 and 0.8 mmol CoCl2·6H2O into a 100 mL beaker, add 0.5 g urea and 17 mL water, and stir until a transparent pink solution is formed.

[0061] Transfer the above uniform and transparent solution to a 25mL polytetrafluoroethylene-lined stainless steel high-pressure hydrothermal reactor, add the pretreated carbon fiber paper at the same time, place it in an oven at 120℃ for 6 hours, and after the reaction is completed, place the hydrothermal reactor to cool to room temperature.

[0062] The carbon paper with the precursor was removed, rinsed repeatedly with deionized water and ethanol, dried in an 80℃ oven for 6 hours, and then calcined in a muffle furnace at a temperature of 350℃ for 2 hours with a heating rate of 2.5℃ / min to obtain a cerium-cobalt composite oxide electrocatalyst uniformly grown on the carbon paper substrate.

[0063] Electrocatalytic oxidation of glycerol:

[0064] A three-electrode system was used to evaluate the reaction performance of the prepared cerium-cobalt composite oxide electrocatalyst. The prepared electrocatalyst was used as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. The electrolyte was a 0.3 mol / L glycerol solution in 1 mol / L potassium hydroxide solution. The selective oxidation performance of the catalyst was tested at room temperature by chronoamperometry (1.4 V) with a charge of 100C. The products were detected by liquid chromatography, and the selectivity for glycolic acid was 35%, the selectivity for glyceric acid was 7%, and the selectivity for formic acid was 58%.

[0065] Example 4 :

[0066] Preparation of cerium-cobalt composite oxide electrocatalysts:

[0067] The carbon paper was cut into 1×2cm pieces, ultrasonically cleaned in ethanol and water for 10 minutes to remove impurities from the surface of the carbon paper fibers, dried in an 80℃ oven, and then calcined in an air atmosphere at 250℃ for 2 hours to obtain a pretreated carbon fiber substrate.

[0068] Weigh 0.8 mmol CeCl3 and 0.8 mmol CoCl2·6H2O into a 100 mL beaker, add 0.5 g urea and 17 mL water, and stir until a transparent pink solution is formed.

[0069] Transfer the above uniform and transparent solution to a 25mL polytetrafluoroethylene-lined stainless steel high-pressure hydrothermal reactor, add the pretreated carbon fiber paper, place it in an oven at 140℃ for 6 hours, and after the reaction is complete, place the hydrothermal reactor to cool to room temperature.

[0070] The carbon paper with the precursor was removed, rinsed repeatedly with deionized water and ethanol, dried in an 80℃ oven for 6 hours, and then calcined in a muffle furnace at a temperature of 350℃ for 2 hours with a heating rate of 2.5℃ / min to obtain a cerium-cobalt composite oxide electrocatalyst uniformly grown on the carbon paper substrate.

[0071] Electrocatalytic oxidation of glycerol:

[0072] A three-electrode system was used to evaluate the reaction performance of the prepared cerium-cobalt composite oxide electrocatalyst. The prepared electrocatalyst was used as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. The electrolyte was a 0.3 mol / L glycerol solution in 1 mol / L potassium hydroxide solution. The selective oxidation performance of the catalyst was tested at room temperature by chronoamperometry (1.4 V) with a charge of 100C. The products were detected by liquid chromatography, and the selectivity for glycolic acid was 31%, the selectivity for glyceric acid was 25%, and the selectivity for formic acid was 44%.

[0073] Example 5 :

[0074] Preparation of cerium-cobalt composite oxide electrocatalysts:

[0075] The carbon paper was cut into 1×2cm pieces, ultrasonically cleaned in ethanol and water for 10 minutes to remove impurities from the surface of the carbon paper fibers, dried in an 80℃ oven, and then calcined in an air atmosphere at 250℃ for 2 hours to obtain a pretreated carbon fiber substrate.

[0076] Weigh 0.8 mmol CeCl3 and 0.8 mmol CoCl2·6H2O into a 100 mL beaker, add 0.5 g urea and 17 mL water, and stir until a transparent pink solution is formed.

[0077] Transfer the above uniform and transparent solution to a 25mL polytetrafluoroethylene-lined stainless steel high-pressure hydrothermal reactor, add the pretreated carbon fiber paper at the same time, place it in an oven at 120℃ for 4 hours, and after the reaction is completed, place the hydrothermal reactor to cool to room temperature.

[0078] The carbon paper with the precursor was removed, rinsed repeatedly with deionized water and ethanol, dried in an 80℃ oven for 6 hours, and then calcined in a muffle furnace at a temperature of 350℃ for 2 hours with a heating rate of 2.5℃ / min to obtain a cerium-cobalt composite oxide electrocatalyst uniformly grown on the carbon paper substrate.

[0079] Electrocatalytic oxidation of glycerol:

[0080] A three-electrode system was used to evaluate the reaction performance of the prepared cerium-cobalt composite oxide electrocatalyst. The prepared electrocatalyst was used as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. The electrolyte was a 0.3 mol / L glycerol solution in 1 mol / L potassium hydroxide solution. The selective oxidation performance of the catalyst was tested at room temperature by chronoamperometry (1.4 V) with a charge of 100C. The products were detected by liquid chromatography, and the selectivity for glycolic acid was 33%, the selectivity for glyceric acid was 20%, and the selectivity for formic acid was 47%.

[0081] Example 6 :

[0082] Preparation of cerium-cobalt composite oxide electrocatalysts:

[0083] The carbon paper was cut into 1×2cm pieces, ultrasonically cleaned in ethanol and water for 10 minutes to remove impurities from the surface of the carbon paper fibers, dried in an 80℃ oven, and then calcined in an air atmosphere at 250℃ for 2 hours to obtain a pretreated carbon fiber substrate.

[0084] Weigh 0.8 mmol CeCl3 and 0.8 mmol CoCl2·6H2O into a 100 mL beaker, add 0.5 g urea and 17 mL water, and stir until a transparent pink solution is formed.

[0085] Transfer the above uniform and transparent solution to a 25mL polytetrafluoroethylene-lined stainless steel high-pressure hydrothermal reactor, add the pretreated carbon fiber paper at the same time, place it in an oven at 120℃ for 6 hours, and after the reaction is completed, place the hydrothermal reactor to cool to room temperature.

[0086] The carbon paper with the precursor was removed, rinsed repeatedly with deionized water and ethanol, dried in an 80℃ oven for 6 hours, and then calcined in a muffle furnace at a temperature of 400℃ for 2 hours with a heating rate of 2.5℃ / min to obtain a cerium-cobalt composite oxide electrocatalyst uniformly grown on the carbon paper substrate.

[0087] Electrocatalytic oxidation of glycerol:

[0088] A three-electrode system was used to evaluate the reaction performance of the prepared cerium-cobalt composite oxide electrocatalyst. The prepared electrocatalyst was used as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. The electrolyte was a 0.3 mol / L glycerol solution in 1 mol / L potassium hydroxide solution. The selective oxidation performance of the catalyst was tested at room temperature by chronoamperometry (1.4 V) with a charge of 100C. The products were detected by liquid chromatography, and the selectivity for glycolic acid was 35%, the selectivity for glyceric acid was 25%, and the selectivity for formic acid was 40%.

[0089] Example 7 :

[0090] Preparation of cerium-cobalt composite oxide electrocatalysts:

[0091] The carbon paper was cut into 1×2cm pieces, ultrasonically cleaned in ethanol and water for 10 minutes to remove impurities from the surface of the carbon paper fibers, dried in an 80℃ oven, and then calcined in an air atmosphere at 250℃ for 2 hours to obtain a pretreated carbon fiber substrate.

[0092] Weigh 0.8 mmol CeCl3 and 0.8 mmol CoCl2·6H2O into a 100 mL beaker, add 0.5 g urea and 17 mL water, and stir until a transparent pink solution is formed.

[0093] Transfer the above uniform and transparent solution to a 25mL polytetrafluoroethylene-lined stainless steel high-pressure hydrothermal reactor, add the pretreated carbon fiber paper at the same time, place it in an oven at 120℃ for 6 hours, and after the reaction is completed, place the hydrothermal reactor to cool to room temperature.

[0094] The carbon paper with the precursor was removed, rinsed repeatedly with deionized water and ethanol, dried in an 80℃ oven for 6 hours, and then calcined in a muffle furnace at a temperature of 350℃ for 2 hours with a heating rate of 2.5℃ / min to obtain a cerium-cobalt composite oxide electrocatalyst uniformly grown on the carbon paper substrate.

[0095] Electrocatalytic oxidation of glycerol:

[0096] A three-electrode system was used to evaluate the reaction performance of the prepared cerium-cobalt composite oxide electrocatalyst. The prepared electrocatalyst was used as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. The electrolyte was a 0.1 mol / L glycerol solution in 1 mol / L potassium hydroxide. The selective oxidation performance of the catalyst was tested at room temperature by chronoamperometry (1.4 V) with a charge of 100C. The products were detected by liquid chromatography, and the selectivity for glycolic acid was 37%, the selectivity for glyceric acid was 8%, and the selectivity for formic acid was 55%.

[0097] Example 8 :

[0098] Preparation of cerium-cobalt composite oxide electrocatalysts:

[0099] The carbon paper was cut into 1×2cm pieces, ultrasonically cleaned in ethanol and water for 10 minutes to remove impurities from the surface of the carbon paper fibers, dried in an 80℃ oven, and then calcined in an air atmosphere at 250℃ for 2 hours to obtain a pretreated carbon fiber substrate.

[0100] Weigh 0.8 mmol CeCl3 and 0.8 mmol CoCl2·6H2O into a 100 mL beaker, add 0.5 g urea and 17 mL water, and stir until a transparent pink solution is formed.

[0101] Transfer the above uniform and transparent solution to a 25mL polytetrafluoroethylene-lined stainless steel high-pressure hydrothermal reactor, add the pretreated carbon fiber paper at the same time, place it in an oven at 120℃ for 6 hours, and after the reaction is completed, place the hydrothermal reactor to cool to room temperature.

[0102] The carbon paper with the precursor was removed, rinsed repeatedly with deionized water and ethanol, dried in an 80℃ oven for 6 hours, and then calcined in a muffle furnace at a temperature of 350℃ for 2 hours with a heating rate of 2.5℃ / min to obtain a cerium-cobalt composite oxide electrocatalyst uniformly grown on the carbon paper substrate.

[0103] Electrocatalytic oxidation of glycerol:

[0104] A three-electrode system was used to evaluate the reaction performance of the prepared cerium-cobalt composite oxide electrocatalyst. The prepared electrocatalyst was used as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. The electrolyte was a 0.1 mol / L glycerol solution in 1 mol / L potassium hydroxide. The selective oxidation performance of the catalyst was tested at room temperature by chronoamperometry (1.3 V) with a charge of 100C. The products were detected by liquid chromatography, and the selectivity for glycolic acid was 39%, for glyceric acid was 20%, and formic acid was 41%.

[0105] Comparative Example 1 :

[0106] Preparation of cobalt oxide electrocatalysts:

[0107] The carbon paper was cut into 1×2cm pieces, ultrasonically cleaned in ethanol and water for 10 minutes to remove impurities from the surface of the carbon paper fibers, dried in an 80℃ oven, and then calcined in an air atmosphere at 250℃ for 2 hours to obtain a pretreated carbon fiber substrate.

[0108] Weigh 0.8 mmol CoCl2·6H2O into a 100 mL beaker, add 0.5 g urea and 17 mL water, and stir until a transparent pink solution is formed.

[0109] Transfer the above uniform and transparent solution to a 25mL polytetrafluoroethylene-lined stainless steel high-pressure hydrothermal reactor, add the pretreated carbon fiber paper at the same time, place it in an oven at 120℃ for 6 hours, and after the reaction is completed, place the hydrothermal reactor to cool to room temperature.

[0110] The carbon paper with the precursor was removed, rinsed repeatedly with deionized water and ethanol, dried in an 80℃ oven for 6 hours, and then calcined in a muffle furnace at a temperature of 350℃ for 2 hours with a heating rate of 2.5℃ / min to obtain a cobalt oxide electrocatalyst uniformly grown on the carbon paper substrate.

[0111] Electrocatalytic oxidation of glycerol:

[0112] A three-electrode system was used to evaluate the reaction performance of the prepared cobalt oxide electrocatalyst. The prepared electrocatalyst was used as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. The electrolyte was a 0.3 mol / L glycerol solution in 1 mol / L potassium hydroxide solution. The selective oxidation performance of the catalyst was evaluated by chronoamperometry (1.4 V) at room temperature with a charge of 100C. The products were detected by liquid chromatography, and the selectivity for glycolic acid was 20%, for glyceric acid was 27%, and formic acid was 53%.

[0113] Comparative Example 2 :

[0114] Preparation of gadolinium-cobalt composite oxide electrocatalysts:

[0115] The carbon paper was cut into 1×2cm pieces, ultrasonically cleaned in ethanol and water for 10 minutes to remove impurities from the surface of the carbon paper fibers, dried in an 80℃ oven, and then calcined in an air atmosphere at 250℃ for 2 hours to obtain a pretreated carbon fiber substrate.

[0116] Weigh 0.8 mmol GdCl3 and 0.8 mmol CoCl2·6H2O into a 100 mL beaker, add 0.5 g urea and 17 mL water, and stir until a transparent pink solution is formed.

[0117] Transfer the above uniform and transparent solution to a 25mL polytetrafluoroethylene-lined stainless steel high-pressure hydrothermal reactor, add the pretreated carbon fiber paper at the same time, place it in an oven at 120℃ for 6 hours, and after the reaction is completed, place the hydrothermal reactor to cool to room temperature.

[0118] The carbon paper with the precursor was removed, rinsed repeatedly with deionized water and ethanol, dried in an 80℃ oven for 6 hours, and then calcined in a muffle furnace at a temperature of 350℃ for 2 hours with a heating rate of 2.5℃ / min to obtain a gadolinium-cobalt composite oxide electrocatalyst uniformly grown on the carbon paper substrate.

[0119] Electrocatalytic oxidation of glycerol:

[0120] A three-electrode system was used to evaluate the reaction performance of the prepared gadolinium-cobalt composite oxide electrocatalyst. The prepared electrocatalyst was used as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. The electrolyte was a 0.3 mol / L glycerol solution in 1 mol / L potassium hydroxide solution. The selective oxidation performance of the catalyst was tested at room temperature by chronoamperometry (1.4 V) with a charge of 100C. The products were detected by liquid chromatography, and the selectivity for glycolic acid was 30%, the selectivity for glyceric acid was 20%, and the selectivity for formic acid was 50%.

[0121] Comparative Example 3 :

[0122] Preparation of Nd:cobalt composite oxide electrocatalysts:

[0123] The carbon paper was cut into 1×2cm pieces, ultrasonically cleaned in ethanol and water for 10 minutes to remove impurities from the surface of the carbon paper fibers, dried in an 80℃ oven, and then calcined in an air atmosphere at 250℃ for 2 hours to obtain a pretreated carbon fiber substrate.

[0124] Weigh 0.8 mmol NdCl3 and 0.8 mmol CoCl2·6H2O into a 100 mL beaker, add 0.5 g urea and 17 mL water, and stir until a transparent pink solution is formed.

[0125] Transfer the above uniform and transparent solution to a 25mL polytetrafluoroethylene-lined stainless steel high-pressure hydrothermal reactor, add the pretreated carbon fiber paper at the same time, place it in an oven at 120℃ for 6 hours, and after the reaction is completed, place the hydrothermal reactor to cool to room temperature.

[0126] The carbon paper with the precursor was removed, rinsed repeatedly with deionized water and ethanol, dried in an 80℃ oven for 6 hours, and then calcined in a muffle furnace at a temperature of 350℃ for 2 hours with a heating rate of 2.5℃ / min to obtain a neodymium cobalt composite oxide electrocatalyst uniformly grown on the carbon paper substrate.

[0127] Electrocatalytic oxidation of glycerol:

[0128] A three-electrode system was used to evaluate the reaction performance of the prepared Nd:cobalt composite oxide electrocatalyst. The prepared electrocatalyst was used as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. The electrolyte was a 0.3 mol / L glycerol solution in 1 mol / L potassium hydroxide. The selective oxidation performance of the catalyst was tested at room temperature by chronoamperometry (1.4 V) with a charge of 100C. The products were detected by liquid chromatography, and the selectivity for glycolic acid was 10%, for glyceric acid was 28%, and formic acid was 62%.

[0129] Comparative Example 4 :

[0130] Preparation of nickel-cobalt composite oxide electrocatalysts:

[0131] The carbon paper was cut into 1×2cm pieces, ultrasonically cleaned in ethanol and water for 10 minutes to remove impurities from the surface of the carbon paper fibers, dried in an 80℃ oven, and then calcined in an air atmosphere at 250℃ for 2 hours to obtain a pretreated carbon fiber substrate.

[0132] Weigh 0.8 mmol NiCl2 and 0.8 mmol CoCl2·6H2O into a 100 mL beaker, add 0.5 g urea and 17 mL water, and stir until a transparent pink solution is formed.

[0133] Transfer the above uniform and transparent solution to a 25mL polytetrafluoroethylene-lined stainless steel high-pressure hydrothermal reactor, add the pretreated carbon fiber paper at the same time, place it in an oven at 120℃ for 6 hours, and after the reaction is completed, place the hydrothermal reactor to cool to room temperature.

[0134] The carbon paper with the precursor was removed, rinsed repeatedly with deionized water and ethanol, dried in an 80℃ oven for 6 hours, and then calcined in a muffle furnace at a temperature of 350℃ for 2 hours with a heating rate of 2.5℃ / min to obtain a nickel-cobalt composite oxide electrocatalyst uniformly grown on the carbon paper substrate.

[0135] Electrocatalytic oxidation of glycerol:

[0136] A three-electrode system was used to evaluate the reaction performance of the prepared nickel-cobalt composite oxide electrocatalyst. The prepared electrocatalyst was used as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. The electrolyte was a 0.3 mol / L glycerol solution in 1 mol / L potassium hydroxide solution. The selective oxidation performance of the catalyst was tested at room temperature by chronoamperometry (1.4 V) with a charge of 100C. The products were detected by liquid chromatography, and the selectivity for glycolic acid was 5%, the selectivity for glyceric acid was 10%, and the selectivity for formic acid was 85%.

[0137] Comparative Example 4 :

[0138] Preparation of copper-cobalt composite oxide electrocatalysts:

[0139] The carbon paper was cut into 1×2cm pieces, ultrasonically cleaned in ethanol and water for 10 minutes to remove impurities from the surface of the carbon paper fibers, dried in an 80℃ oven, and then calcined in an air atmosphere at 250℃ for 2 hours to obtain a pretreated carbon fiber substrate.

[0140] Weigh 0.8 mmol CuCl2 and 0.8 mmol CoCl2·6H2O into a 100 mL beaker, add 0.5 g urea and 17 mL water, and stir until a transparent pink solution is formed.

[0141] Transfer the above uniform and transparent solution to a 25mL polytetrafluoroethylene-lined stainless steel high-pressure hydrothermal reactor, add the pretreated carbon fiber paper at the same time, place it in an oven at 120℃ for 6 hours, and after the reaction is completed, place the hydrothermal reactor to cool to room temperature.

[0142] The carbon paper with the precursor was removed, rinsed repeatedly with deionized water and ethanol, dried in an 80℃ oven for 6 hours, and then calcined in a muffle furnace at a temperature of 350℃ for 2 hours with a heating rate of 2.5℃ / min to obtain a copper-cobalt composite oxide electrocatalyst uniformly grown on the carbon paper substrate.

[0143] Electrocatalytic oxidation of glycerol:

[0144] A three-electrode system was used to evaluate the reaction performance of the prepared copper-cobalt composite oxide electrocatalyst. The prepared electrocatalyst was used as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. The electrolyte was a 0.3 mol / L glycerol solution in 1 mol / L potassium hydroxide solution. The selective oxidation performance of the catalyst was tested at room temperature by chronoamperometry (1.4 V) with a charge of 100C. The products were detected by liquid chromatography, and the selectivity for glycolic acid was 5%, the selectivity for glyceric acid was 10%, and the selectivity for formic acid was 85%.

[0145] Comparative Example 7:

[0146] Preparation of cerium-cobalt composite oxide electrocatalysts:

[0147] The carbon paper was cut into 1×2cm pieces, ultrasonically cleaned in ethanol and water for 10 minutes to remove impurities from the surface of the carbon paper fibers, dried in an 80℃ oven, and then calcined in an air atmosphere at 250℃ for 2 hours to obtain a pretreated carbon fiber substrate.

[0148] Weigh 0.8 mmol CeCl3 and 0.8 mmol CoCl2·6H2O into a 100 mL beaker, add 0.5 g urea and 17 mL water, and stir until a transparent pink solution is formed.

[0149] Transfer the above uniform and transparent solution to a 25mL polytetrafluoroethylene-lined stainless steel high-pressure hydrothermal reactor, add the pretreated carbon fiber paper at the same time, place it in an oven at 120℃ for 6 hours, and after the reaction is completed, place the hydrothermal reactor to cool to room temperature.

[0150] The carbon paper with the precursor was removed, rinsed repeatedly with deionized water and ethanol, dried in an 80℃ oven for 6 hours, and then calcined in a muffle furnace at a temperature of 350℃ for 2 hours with a heating rate of 2.5℃ / min to obtain a cerium-cobalt composite oxide electrocatalyst uniformly grown on the carbon paper substrate.

[0151] Electrocatalytic oxidation of glycerol:

[0152] A three-electrode system was used to evaluate the reaction performance of the prepared cerium-cobalt composite oxide electrocatalyst. The prepared electrocatalyst was used as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. The electrolyte was a 1 mol / L potassium hydroxide solution. The oxygen evolution voltage was tested by linear sweep voltammetry at room temperature, with an initial voltage of 1.62 V.

[0153] The morphology of cerium-cobalt composite oxide catalysts with different Ce additions was studied using scanning electron microscopy. Figures 1-4It can be seen that cerium cobalt oxide uniformly covers the carbon fiber surface, forming a dense nanolayer. This structure can provide more active sites during electrocatalysis. By adjusting the addition ratio of CeCl3 salt in the precursor, the Ce:Co ratio increased from 1:10 to 2:1. With the increase of Ce content, the number of spindle-shaped CeO2 nanoparticles in the composite oxide increased, and the area occupied on the carbon fiber surface also increased. This indicates that by optimizing the CeO2 and Co3O4 component ratio of the catalyst, the morphology of the heterostructure can be controlled. When the addition ratio is further increased to 2:1, the carbon fiber surface is mostly composed of spindle-shaped CeO2 structures, interspersed with Co3O4 nanowires. The actual Ce / Co molar ratios of the heterostructure catalysts obtained by changing the amount of cerium salt were measured by ICP (Table 1), which were 0.05, 0.2, and 0.25, respectively. Furthermore, XRD data shows that the characteristic diffraction peak at 26.56° in Example 1 belongs to the graphite carbon structure of carbon paper fiber, the diffraction peaks at 31.27° and 36.85° belong to the (220) and (311) crystal planes of Co3O4 (PDF#74-2120), and the diffraction peak at 28.53° belongs to the (111) crystal plane of CeO2 (PDF#89-8436). This indicates that the crystal phase structure is a composite oxide crystal phase of CeO2 and Co3O4. Figure 5 Cobalt oxide without added cerium salt is in the Co3O4 crystalline phase. Figure 6 ).

[0154] Table 1

[0155] catalyst Ce / Co ratio Example 1 0.2 Example 2 0.05 Example 3 0.25

[0156] The morphology of other rare earth metal and cobalt composite oxides was tested, from Figure 7 It can be seen that the GdCo oxides grow and disperse in a loose manner on carbon fibers, which may be due to an unsuitable co-growth environment for the rare earth metal and cobalt metal.

[0157] Such as the LSV curve ( Figure 8 As shown in the figure, Example 1, used for the electrocatalytic oxidation of glycerol, has a low onset potential, reaching 10 mA·cm at 1.38 V. -2 Current density. For example... Figure 9 As shown, the cerium-cobalt composite oxide catalyst obtained in Example 1 exhibits good cycling performance, maintaining a glycolic acid selectivity of over 40% after three cycles.

[0158] The applicant declares that the detailed method of the present invention is illustrated by the above embodiments, but the present invention is not limited to the above detailed method, that is, it does not mean that the present invention must rely on the above detailed method to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. The application of a cerium-cobalt composite oxide electrocatalyst in the electrocatalytic oxidation of glycerol, characterized in that, The preparation method of the cerium-cobalt composite oxide electrocatalyst includes the following steps: Soluble cerium salt, soluble cobalt salt, and urea are added to water and stirred to form a mixture, wherein the concentration of cerium ions is 4-95 mmol / L, the concentration of cobalt ions is 40-60 mmol / L, and the molar ratio of the total metal content of the soluble cobalt salt and soluble cerium salt to urea is (0.01-0.5):

1. The mixture and carbon fiber substrate were added to a sealed container and kept at 100-160°C for 2-24 hours. After cooling to room temperature, a carbon fiber substrate with a supported catalyst precursor was obtained. The carbon fiber substrate of the supported catalyst precursor is dried and calcined at a temperature of 300–500°C for 1–4 h at a heating rate of 1–5°C / min to obtain the cerium-cobalt composite oxide electrocatalyst.

2. The application according to claim 1, characterized in that, The concentration of cerium ions is 20–55 mmol / L.

3. The application according to claim 1, characterized in that, The total metal content of the soluble cobalt salt and soluble cerium salt, in molar ratio to urea, is (0.05–0.4):

1.

4. The application according to claim 1, characterized in that, The mixture and carbon fiber substrate are added to a sealed container and kept at 120–140°C for 6–12 hours.

5. The application according to claim 1, characterized in that, The carbon fiber substrate is carbon paper or carbon cloth.

6. The application according to claim 1, characterized in that, The calcination atmosphere is air.

7. The application according to claim 1, characterized in that, The calcination time is 1 hour to 2 hours.

8. The application according to claim 1, characterized in that, The cerium-cobalt composite oxide electrocatalyst is used as the working electrode, the platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, forming a three-electrode system for glycerol oxidation.

9. The application according to claim 1, characterized in that, The electrolyte for the electrocatalytic oxidation of glycerol is an alkaline solution of glycerol, wherein the concentration of glycerol is 0.1–2 mol / L.

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