A method for synergistically increasing oxygen vacancies of cobalt oxide, a cobalt oxide electrode prepared by the method, and applications thereof

Abstract

The application belongs to the field of electrochemical catalysis, and discloses a method for synergistically increasing oxygen vacancies of cobalt oxide, a cobalt oxide electrode prepared by the method and application of the electrode. The application uses cyclic voltammetry to electrodeposit cobalt oxide on an electrode, controls the upper limit potential of a deposition scan of cyclic voltammetry reduction electrodeposition, so as to realize deposition of cobalt oxide with different ratios of oxygen vacancies and lattice oxygen. With negative shift of the upper limit potential of the scan, the cobalt oxide obtains a higher ratio of oxygen vacancies and lattice oxygen, a larger ratio of trivalent cobalt and divalent cobalt, and presents outstanding electrocatalytic activity for oxygen evolution reaction and glucose oxidation. The control method not only has the characteristics of simple operation and low cost, but also can reduce the overpotential of oxygen evolution by water decomposition through the added glucose, and has a wide application prospect in the field of hydrogen production by water electrolysis.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical catalysis, specifically relating to a method for synergistically increasing oxygen vacancies in cobalt oxide, the prepared cobalt oxide electrode, and its applications. Background Technology

[0002] In the process of water electrolysis, the oxygen evolution reaction (OER) involves multiple steps and exhibits a large overpotential and slow kinetics, resulting in significant energy loss. Therefore, metals and their oxides are commonly used as commercial catalysts to promote the OER, thereby reducing the cost of hydrogen production. Cobalt-based catalysts, as non-noble metal-based electrocatalysts, demonstrate high OER activity in both acidic and alkaline media and show great promise.

[0003] To enhance the catalytic activity of cobalt oxides in the oxygen evolution reaction (OER), modifying their structure and increasing oxygen vacancies have become key directions for improving the materials. Numerous studies have designed and synthesized a series of high-performance cobalt-based electrocatalysts, including cobalt oxides / chalcogenides and cobalt layered double hydroxides, focusing on controllable synthesis strategies, structural characteristics, ligand effects, defects, oxygen vacancies, and supporting materials. However, methods involving the tunable use of oxygen vacancies to improve OER activity are still under investigation. Summary of the Invention

[0004] To overcome the shortcomings and deficiencies of existing technologies, and to reduce oxygen evolution overpotential, promote hydrogen production, and improve the electrocatalytic activity of metal, metal oxide, and metal hydroxide electrodes, the primary objective of this invention is to provide a method for synergistically increasing oxygen vacancies in cobalt oxides. This method involves electrodepositing non-noble metal hydroxides in a neutral electrolyte using cyclic voltammetry, and controlling different upper limits of the cyclic voltammetric scan to increase the oxygen vacancies in the material.

[0005] Another object of the present invention is to provide a cobalt oxide oxygen electrode prepared by the above method.

[0006] Another object of the present invention is to provide an application of the above-mentioned cobalt oxide oxygen electrode; since the electrode increases the number of cobalt oxide oxygen vacancies, it enhances the activity of catalytic oxygen evolution reaction and glucose oxidation, thereby promoting hydrogen production.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for synergistically increasing oxygen vacancies in cobalt oxide includes the following steps:

[0009] (1) An ITO electrode was immersed in a mixed electroplating solution containing cobalt sulfate as the working electrode, a saturated calomel electrode as the reference electrode, and a titanium sheet as the counter electrode to construct a three-electrode system. Cyclic voltammetry was performed on an electrochemical workstation. Cobalt ions in the cobalt sulfate solution were deposited on the surface of the ITO electrode in the form of cobalt oxide through negative scan reduction and positive scan oxidation to obtain a cobalt oxide electrode. In the cyclic voltammetry, the starting potential of 1.3V and the lower limit potential of -1.3V were kept constant to control the deposition amount. Different upper scan potentials were changed within the range of 1.3V to -0.7V (vs. SCE). The number of cycles was 1, and the scan rate was 0.05V / s.

[0010] (2) The cobalt oxide electrode obtained in step (1) is placed in a 1 mol / L KOH solution and continuously cyclically treated by cyclic voltammetry to activate and enhance the stability of the electrode. The cobalt oxide electrode after cyclic treatment is washed and then dried under an infrared lamp to fix the cobalt oxide structure, and finally a cobalt oxide electrode with increased oxygen vacancies is obtained.

[0011] The mixed electroplating solution in step (1) contains sodium sulfate with a concentration of 0.1 mol / L and cobalt sulfate with a concentration of 0.005 mol / L.

[0012] The upper limit potential of the scan in step (1) is -0.7V.

[0013] The cyclic range of the cyclic voltammetry method in step (2) is 0.2V-0.5V (vs. SCE), and the number of cycles is 20.

[0014] A cobalt oxide electrode with increased oxygen vacancies prepared by the above method.

[0015] The aforementioned cobalt oxide electrodes with increased oxygen vacancies in cobalt oxides can be used in catalytic hydrogen evolution, catalytic glucose oxidation to reduce hydrogen evolution overpotential, or in the preparation of glucose sensors.

[0016] Compared with the prior art, the present invention has the following advantages and effects:

[0017] (1) The electrode prepared by the present invention controls the same lower limit potential to control the same deposition amount. By controlling different upper limit potentials, the purpose of changing the oxygen vacancies and lattice oxygen ratio in the cobalt oxide electrode can be achieved.

[0018] (2) The electrode prepared by the present invention exhibits good oxygen evolution reaction catalytic performance in alkaline environment. The cobalt oxide electrode with a scanning upper limit potential of -0.7V has the smallest overpotential and the largest current density in the same series.

[0019] (3) The electrode prepared by the present invention exhibits electrocatalytic performance for glucose in an alkaline environment, introduces glucose oxidation to promote oxygen production, and reduces the overpotential of the oxygen evolution reaction. Attached Figure Description

[0020] Figure 1 This is a diagram showing the reduction electrodeposition of cobalt oxides with different oxygen vacancies.

[0021] Figure 2 The O spectrum of a cobalt oxide electrode XPS prepared with an upper limit potential of -0.7V is shown. The peaks in the figure, from left to right, represent adsorbed oxygen, oxygen vacancies, and lattice oxygen, respectively.

[0022] Figure 3 Linear scan voltammetry of cobalt oxides prepared for different upper scan potentials in 1 mol / L KOH.

[0023] Figure 4 Cyclic voltammetry of cobalt oxides prepared for different upper scan limits in 1 mol / L KOH and glucose solutions of different concentrations. Detailed Implementation

[0024] The present invention will be further described below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0025] According to the design purpose of this invention, simple substitution of similar substances and changes in size and shape, such as changing the concentration of electrodeposition electrolyte, the specifications and size of the preparation device, the deposition potential, the electrode type, or the pH value of the solution, should all fall within the scope of this invention; unless otherwise specified, the experimental methods used in the following examples are conventional methods existing in this technical field; unless otherwise specified, the materials and reagents used can be obtained commercially.

[0026] Example 1: Fabrication of cobalt oxide electrodes with different oxygen vacancies and lattice oxygen ratios

[0027] (1) Prepare conductive glass electrodes, mark the conductive surfaces, then ultrasonically treat the conductive glass electrodes, wash them with deionized water, anhydrous ethanol and deionized water for 20 minutes respectively, and then dry them for later use.

[0028] (2) Using sodium sulfate as the supporting electrolyte, a mixed electroplating solution containing sodium sulfate at a concentration of 0.1 mol / L and cobalt sulfate at a concentration of 0.005 mol / L was prepared.

[0029] (3) The electrode treated in step (1) is immersed in the mixed electroplating solution obtained in step (2) as the working electrode, the saturated calomel electrode as the reference electrode, and the titanium sheet as the counter electrode to construct a three-electrode system; cyclic voltammetry is performed on an electrochemical workstation, and cobalt ions in the cobalt sulfate solution are deposited on the electrode surface in the form of cobalt oxides through negative scan reduction and positive scan oxidation. In the cyclic voltammetry, the starting potential of 1.3V and the lower limit potential of -1.3V are kept constant to control the deposition amount. Different upper scan potentials, i.e., the termination potentials, are changed to 1.3V, 0.8V, 0V, and -0.7V (vs. SCE), with one cycle and a scan rate of 0.05V / s, to obtain cobalt oxide electrodes with different oxygen vacancies; the reduction electrodeposition diagram of the cobalt oxide electrodes with different oxygen vacancies is shown in the figure. Figure 1 As shown.

[0030] (4) Freshly prepared cobalt oxide electrodes with different oxygen vacancies were placed in a 1 mol / L KOH solution and continuously cyclically treated by cyclic voltammetry. The cyclic range was 0.2 V-0.5 V (vs. SCE) and the number of cycles was 20 to activate and enhance the stability of the electrodes. The cobalt oxide electrodes after cyclic treatment were washed and then dried under an infrared lamp for 2 minutes to fix the cobalt oxide structure, and finally cobalt oxide electrodes with different oxygen vacancies were obtained.

[0031] Example 2 XPS characterization of cobalt oxide electrode

[0032] The cobalt oxide electrode prepared in Example 1 was subjected to XPS analysis, and the O spectrum was peaked. The results are as follows: Figure 2 As shown, the cobalt oxide electrode prepared at a low upper limit scanning potential has a higher proportion of oxygen vacancies and a larger ratio of oxygen vacancies to lattice oxygen.

[0033] Example 3: Oxygen Evolution Reaction Performance Test of Cobalt Oxide Electrodes with Different Oxygen Vacancy and Lattice Oxygen Ratios

[0034] The cobalt oxide electrode prepared in Example 1 was used as the working electrode, a titanium sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, forming a three-electrode system in 1 mol / L KOH. An electrochemical workstation was connected, and linear sweep voltammetry was performed to measure the relationship between current and voltage.

[0035] The results are as follows Figure 3 As shown, the cobalt oxide electrode with the largest number of oxygen vacancies and an upper limit scanning potential of -0.7V exhibits the smallest initiation potential and the largest current density, demonstrating good catalytic oxygen evolution activity.

[0036] Example 4: Performance Testing of Cobalt Oxide Electrodes with Different Oxygen Vacancy and Lattice Oxygen Ratios for Glucose Oxidation

[0037] The cobalt oxide electrode prepared in Example 1 was used as the working electrode, a titanium sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, forming a three-electrode system in 1 mol / L KOH and glucose solutions of different concentrations. An electrochemical workstation was connected to perform cyclic voltammetry tests to measure the relationship between current and voltage.

[0038] The results are as follows Figure 4 As shown, the cobalt oxide electrode with a scan upper limit potential of -0.7V exhibits good catalytic activity for glucose oxidation in cyclic voltammetry tests, with the current density increasing with increasing glucose concentration. This electrode demonstrates a lower potential and higher current density for glucose oxidation compared to the oxygen evolution reaction, which is beneficial for anodic oxidation and thus promotes hydrogen production at the cathode.

[0039] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent application should be determined by the appended claims.

Claims

1. A method for synergistically increasing oxygen vacancies in cobalt oxide, characterized in that... The following steps are included: (1) An ITO electrode was immersed in a mixed electroplating solution containing cobalt sulfate as the working electrode, a saturated calomel electrode as the reference electrode, and a titanium sheet as the counter electrode to construct a three-electrode system. Cyclic voltammetry was performed on an electrochemical workstation. Cobalt ions in the cobalt sulfate solution were deposited on the surface of the ITO electrode in the form of cobalt oxide through negative scan reduction and positive scan oxidation to obtain a cobalt oxide electrode. In the cyclic voltammetry, the starting potential of 1.3 V and the lower limit potential of -1.3 V were kept constant to control the deposition amount. Different upper scan potentials were changed within the range of 1.3 V to -0.7 V. The number of cycles was 1, and the scan rate was 0.05 V / s. (2) The cobalt oxide electrode obtained in step (1) is placed in a 1 mol / L KOH solution and the electrode is continuously cyclically treated by cyclic voltammetry to activate and enhance the stability of the electrode. The cobalt oxide electrode after the recycling process is washed and then dried under an infrared lamp to fix the cobalt oxide structure, finally obtaining a cobalt oxide electrode with increased oxygen vacancies.

2. The method for synergistically increasing oxygen vacancies in cobalt oxide according to claim 1, characterized in that: The mixed electroplating solution in step (1) contains sodium sulfate with a concentration of 0.1 mol / L and cobalt sulfate with a concentration of 0.005 mol / L.

3. The method for synergistically increasing oxygen vacancies in cobalt oxide according to claim 1, characterized in that: The upper limit potential of the scan in step (1) is -0.7 V.

4. The method for synergistically increasing oxygen vacancies in cobalt oxide according to claim 1, characterized in that: The cyclic voltammetry method described in step (2) has a cyclic range of 0.2 V to 0.5 V and a cycle count of 20.

5. A cobalt oxide electrode with increased oxygen vacancies in cobalt oxide prepared by the method of claim 1.

6. The application of the cobalt oxide electrode with increased oxygen vacancies according to claim 5 in reducing the hydrogen evolution overpotential during the catalytic oxidation of glucose.

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