Platinum-cobalt hydroxide composite material with cobalt vacancy and preparation method and application thereof

Abstract

The invention relates to the technical field of electrochemical sensing, in particular to a platinum-cobalt hydroxide composite material with cobalt vacancy and a preparation method and application thereof. The platinum-cobalt hydroxide composite material with the cobalt vacancies comprises foamed nickel, Pt nanoparticles and cobalt hydroxide, the cobalt hydroxide is deposited on the foamed nickel, the Pt nanoparticles are deposited on the surface of the cobalt hydroxide, and the cobalt vacancies exist in cobalt hydroxide crystal lattices. Wherein the internal electronic structure of the platinum-cobalt hydroxide composite material is changed due to the existence of the cobalt vacancy, the electron transfer rate in the platinum-cobalt hydroxide composite material is increased, and the regulation and control effect of the cobalt vacancy on the electronic structure and the synergistic catalytic effect of a platinum-cobalt hydroxide heterogeneous interface are utilized. When the platinum-cobalt hydroxide composite material with the cobalt vacancy is used as an ammonia nitrogen electrochemical detection sensitive electrode, the catalytic activity of ammoxidation reaction can be remarkably improved, so that a sensor is endowed with the detection performance of low detection limit, high sensitivity, excellent selectivity and good recovery rate.

Description

Technical Field

[0001] This invention relates to the field of electrochemical sensing technology, specifically to a platinum-cobalt hydroxide composite material with cobalt vacancies, its preparation method, and its application. Background Technology

[0002] Ammonia nitrogen is a common pollutant in water bodies. Its sources are widespread, and once it causes pollution problems, the consequences are severe. For example, in natural water bodies, excessive ammonium ions can lead to eutrophication, causing excessive algae growth; high ammonia concentrations can cause fish and shrimp to die from lack of oxygen, thus affecting the ecological balance. Furthermore, excessive ammonia nitrogen concentrations in aquaculture water bodies can cause direct economic losses. Excessive ammonia nitrogen in drinking water poses a carcinogenic risk. Therefore, detecting ammonia nitrogen concentrations in water bodies is of great significance for environmental protection, fisheries production, and human health.

[0003] The main methods for detecting ammonia nitrogen are electrochemical methods and spectrophotometry. Electrochemical methods, including nano-modified electrode methods, offer advantages such as high efficiency, sensitivity, and speed. Spectrophotometric methods, including the Nessler's reagent method, are traditional detection methods. The superior performance of electrochemical methods is primarily due to the sensitive materials used. Currently, widely used sensitive materials for ammonia nitrogen detection include conductive polymers, metal hydroxides, transition metals, and noble metals. Conductive polymers are represented by polyaniline and polypyrrole, metal hydroxides by nickel hydroxide, transition metals by copper, and noble metals by platinum, gold, and silver. From the perspective of detection principle, the detection of ammonia nitrogen by conductive polymers is based on a protonation process, accompanied by the release of hydrogen ions (H+). + The continuous release of nitrogen (N) is a concern; while the detection of ammonia nitrogen using precious metals such as gold, silver, and copper as sensitive electrodes relies on complexation reactions. However, most of these detection processes are consumable and suffer from poor stability. Although platinum has high catalytic activity, its high price increases the cost of sensitive electrode materials. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a platinum-cobalt hydroxide composite material with cobalt vacancies, its preparation method, and its applications. The composite material comprises nickel foam, Pt nanoparticles, and cobalt hydroxide. Cobalt hydroxide is deposited on the nickel foam, and the Pt nanoparticles are deposited on the surface of the cobalt hydroxide, with cobalt vacancies present in the cobalt hydroxide lattice. In this composite material, the presence of cobalt vacancies alters the internal electronic structure of the platinum-cobalt hydroxide composite, thereby accelerating the electron transfer rate within the composite. By combining electrochemical deposition with a substitution reaction strategy, cobalt hydroxide is efficiently deposited on the three-dimensional structure of nickel foam, overcoming the problem of poor electrode structure stability. Through the regulatory effect of cobalt vacancies on the electronic structure and the synergistic catalytic effect of the platinum-cobalt hydroxide heterointerface, the sensitivity of ammonia nitrogen detection is significantly improved and the detection limit is lowered, thus achieving electrochemical detection of ammonia nitrogen with low detection limit, high sensitivity, and excellent selectivity. The confinement and anchoring effect of cobalt vacancies optimizes the dispersion and stability of platinum nanoparticles, significantly reducing the amount of platinum used while ensuring catalytic activity, effectively solving the problem of excessively high cost of traditional platinum-based electrode materials.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first objective of this invention is to provide a platinum-cobalt hydroxide composite material with cobalt vacancies, the platinum-cobalt hydroxide composite material with cobalt vacancies comprising nickel foam, Pt nanoparticles and cobalt hydroxide, wherein cobalt hydroxide is deposited on the nickel foam, Pt nanoparticles are deposited on the surface of the cobalt hydroxide, and cobalt vacancies exist in the cobalt hydroxide lattice.

[0006] A second objective of this invention is to provide a method for preparing the above-mentioned platinum-cobalt hydroxide composite material with cobalt vacancies, comprising the following steps: S1. Using nickel foam as the working electrode, a three-electrode system consisting of a working electrode, a reference electrode, and a counter electrode is formed. An aqueous solution of soluble cobalt salt is used as the electrolyte. One end of the three-electrode system is immersed in the electrolyte, and the other end is electrically connected to an electrochemical workstation. Electrochemical deposition is carried out at a constant potential to form cobalt hydroxide supported by nickel foam, thus obtaining Co(OH)2-NF.

[0007] S2. Immerse Co(OH)₂-NF in a chloroplatinic acid aqueous solution. The Co in Co(OH)₂... 2+ Pt in chloroplatinic acid aqueous solution 4+ A displacement reaction occurs, during which Co 2+ Oxidized to Co 3+ Co 3+ Dissolved, forming cobalt vacancies, while Pt 4+The particles are reduced to Pt nanoparticles and deposited in situ on the surface of cobalt hydroxide to obtain a platinum-cobalt hydroxide composite material with cobalt vacancies.

[0008] Preferably, the aqueous solution of the soluble cobalt salt is a CoCl2·6H2O aqueous solution, and the mass concentration of the CoCl2·6H2O aqueous solution is 1 mg / mL to 1.33 mg / mL.

[0009] Preferably, the concentration of the chloroplatinic acid aqueous solution is 0.005 mol / L to 0.025 mol / L. Below this range, the amount of zero-valent platinum nanoparticles generated is insufficient, making it difficult to improve the detection capability of ammonia nitrogen; above this range, the reaction is too fast, platinum nanoparticles agglomerate, the number of catalytic sites decreases, and the detection activity declines.

[0010] Preferably, the chloroplatinic acid aqueous solution is prepared by mixing chloroplatinic acid solution and water at a volume ratio of 1 to 5:20, and the concentration of the chloroplatinic acid solution is 0.1 mol / L.

[0011] Preferably, the nickel foam is further subjected to ultrasonic cleaning with acetone, hydrochloric acid, ethanol and deionized water in sequence, then rinsed with deionized water until neutral and dried to obtain pretreated nickel foam.

[0012] Preferably, the electrochemical deposition conditions are: electrodeposition at a constant potential of -0.9V to -1.2V for 500s to 1500s.

[0013] Preferably, the conditions for the displacement reaction are: reaction at 25℃~50℃ for 1h~7h.

[0014] A third objective of this invention is to provide the application of the aforementioned platinum-cobalt hydroxide composite material with cobalt vacancies in the preparation of a sensitive electrode for the electrochemical detection of ammonia nitrogen.

[0015] Preferably, the application method includes the following steps: Electrochemical ammonia nitrogen detection was performed using the platinum-cobalt hydroxide composite material with cobalt vacancies as the sensitive electrode (working electrode). A three-electrode system consisting of a working electrode, a reference electrode, and a counter electrode was used, with 1 mol / L KOH solution as the electrolyte. Differential pulse voltammetry (DPV) was employed at -0.8 V to 0.2 V, and the peak current at different ammonia nitrogen concentrations was recorded. The ammonia nitrogen was quantitatively determined based on the linear relationship between the peak current and the ammonia nitrogen concentration.

[0016] Before performing the DPV test, cyclic voltammetry was used in a 1 mol / L KOH solution to activate the electrode within a potential window of -1V to 0.4V, with 30 cycles and a scan rate of 50 mV / s. In this experiment, 1 mol / L KOH was used; some reports have described tests using 0.1 mol / L, 0.5 mol / L, 1 mol / L, and 2 mol / L solutions.

[0017] Preferably, the linear range of ammonia nitrogen concentration is 5 μmol / L to 899 μmol / L, and the detection limit is 1.47 μmol / L.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides a platinum-cobalt hydroxide composite material with cobalt vacancies, comprising nickel foam, Pt nanoparticles, and cobalt hydroxide. Cobalt hydroxide is deposited on the nickel foam, and Pt nanoparticles are deposited on the surface of the cobalt hydroxide, with cobalt vacancies present in the cobalt hydroxide lattice. Based on the catalytic activity of platinum, this invention utilizes the regulatory effect of cobalt vacancies on electronic structure and the synergistic catalytic effect of the platinum-cobalt hydroxide heterointerface to significantly improve the sensitivity of ammonia nitrogen detection and lower the detection limit. Simultaneously, by optimizing the dispersion and stability of platinum nanoparticles through the confined anchoring effect of cobalt vacancies, the amount of platinum used is significantly reduced while ensuring catalytic activity, effectively solving the problem of excessively high cost of traditional platinum-based electrode materials.

[0019] 2. Using the platinum-cobalt hydroxide composite material with cobalt vacancies described in this invention as a sensitive electrode for ammonia nitrogen electrochemical detection can significantly improve the catalytic activity of the ammonia oxidation reaction, thereby endowing the sensor with detection performance of low detection limit, high sensitivity, excellent selectivity and good recovery rate.

[0020] 3. This invention provides a method for preparing a platinum-cobalt hydroxide composite material with cobalt vacancies. Using nickel foam as the working electrode, a three-electrode system consisting of a working electrode, a reference electrode, and a counter electrode is employed. An aqueous solution of CoCl₂·6H₂O is used as the electrolyte. One end of the three-electrode system is immersed in the electrolyte, while the other end is electrically connected to an electrochemical workstation. Electrochemical deposition is performed at a constant potential to form nickel foam-supported cobalt hydroxide, yielding Co(OH)₂-NF. The Co(OH)₂-NF is then immersed in a chloroplatinic acid aqueous solution. The Co in Co(OH)₂... 2+ Pt in chloroplatinic acid aqueous solution 4+ A displacement reaction occurs, during which Co 2 + Oxidized to Co 3+ Co 3+ Dissolved, forming cobalt vacancies, while Pt 4+Platinum is reduced to Pt nanoparticles and deposited in situ on the surface of cobalt hydroxide, resulting in a platinum-cobalt hydroxide composite material with cobalt vacancies. This invention employs a strategy combining electrochemical deposition and displacement reactions. First, cobalt hydroxide is efficiently deposited on a three-dimensional nickel foam surface. Then, platinum is deposited in situ via a displacement reaction, overcoming the problem of poor electrode structure stability. The formation of cobalt vacancies alters the internal electronic structure of the platinum-cobalt hydroxide composite material, thereby accelerating the electron transfer rate and enhancing its catalytic activity. Attached Figure Description

[0021] Figure 1 The cyclic voltammetry curves are for Examples 1 to 6, Comparative Example 4 (platinum-cobalt hydroxide composite material with cobalt vacancies), Comparative Example 2 (Pt-NF), and Comparative Example 1 (Co(OH)2-NF) in 1 mol / L KOH + 0.1 mol / L NH4Cl solution. (a) Examples 1 to 4, (b) Examples 2 and Examples 5 to 6, (c) Examples 5 to 6 and Comparative Example 4, and (d) Examples 5 and Comparative Examples 1 to 2.

[0022] Figure 2 The figures show the differential pulse voltammetry curves and the fitting curves of ammonia nitrogen concentration versus peak current for Pt-Co(OH)2-NF-5 in ammonia nitrogen solution in Example 5. Specifically, (a) is the differential pulse voltammetry curve for ammonia nitrogen solution concentrations of 5 μmol / L to 149 μmol / L, (c) is the differential pulse voltammetry curve for ammonia nitrogen solution concentrations of 149 μmol / L to 899 μmol / L, (b) is the fitting curve of ammonia nitrogen concentration versus peak current for ammonia nitrogen concentrations of 5 μmol / L to 149 μmol / L, and (d) is the fitting curve of ammonia nitrogen concentration versus peak current for ammonia nitrogen concentrations of 149 μmol / L to 899 μmol / L.

[0023] Figure 3 The images show the SEM image and EDS elemental distribution map of Pt-Co(OH)2-NF-5, where (a) is the SEM image of Pt-Co(OH)2-NF-5, (b) is the O element, (c) is the Co element, and (d) is the Pt element.

[0024] Figure 4 Co(OH) )2 XPS peak fitting plots and XRD spectra of -NF and Pt-Co(OH)2-NF-5, where (a) is the peak fitting plot of Co(OH)2-NF-5. )2(a) XPS peak fitting diagram of O element O 1s in Pt-Co(OH)2-NF, (b) XPS peak fitting diagram of Co element Co 2p in Co(OH)2-NF, (c) XPS peak fitting diagram of O element O 1s in Pt-Co(OH)2-NF-5, (d) XPS peak fitting diagram of Co element Co 2p in Pt-Co(OH)2-NF-5, (e) XPS peak fitting diagram of Pt element Pt 4f in Pt-Co(OH)2-NF-5, and (f) XRD patterns of Pt-Co(OH)2-NF-5 and Co(OH)2-NF. Detailed Implementation

[0025] The technical solution of the present invention will be clearly and completely described below with reference to the data in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased on the market or prepared by existing methods.

[0027] In existing technologies, sensitive materials for electrochemical detection of ammonia nitrogen are mainly divided into conductive polymers, transition metals, and noble metals. Among them, conductive polymers and gold, silver, and copper materials are based on protonation or complexation reactions for detection, which are consumable detections with poor stability. While platinum has high catalytic activity, its high price leads to excessively high costs for sensitive electrodes.

[0028] To address the problems existing in the prior art, the present invention provides a platinum-cobalt hydroxide composite material with cobalt vacancies. The platinum-cobalt hydroxide composite material with cobalt vacancies includes nickel foam, Pt nanoparticles and cobalt hydroxide. Cobalt hydroxide is deposited on the nickel foam, Pt nanoparticles are deposited on the surface of cobalt hydroxide, and cobalt vacancies exist in the cobalt hydroxide lattice.

[0029] This invention utilizes a strategy combining electrochemical deposition and displacement reaction to prepare a platinum-cobalt hydroxide composite material with cobalt vacancies. The in-situ growth method overcomes the problems of reduced activity and poor stability associated with powder materials requiring a spraying process. By regulating the electronic structure through cobalt vacancies and leveraging the synergistic catalytic effect of the platinum-cobalt hydroxide heterointerface, the invention solves the problems of insufficient sensitivity and selectivity in traditional materials, as well as the high cost and large amount of platinum required. This results in a low detection limit, high sensitivity, and excellent selectivity for the electrochemical detection of ammonia nitrogen.

[0030] To enable those skilled in the art to more clearly understand the technical solution of the present invention, the following will provide a detailed description in conjunction with specific embodiments: Example 1 A method for preparing a platinum-cobalt hydroxide composite material with cobalt vacancies includes the following steps: S1. Using nickel foam as a conductive substrate, the nickel foam is cleaned and dried to obtain pretreated nickel foam for later use.

[0031] S2. 35.7 mg of CoCl2·6H2O was added to 30 mL of deionized water and ultrasonically dispersed to obtain an aqueous solution of CoCl2·6H2O. Using a three-electrode system, with pretreated nickel foam as the working electrode, a platinum sheet (1.0 cm × 1.0 cm) as the counter electrode, Hg / HgO as the reference electrode, and the aqueous solution of CoCl2·6H2O as the electrolyte, electrochemical deposition was carried out for 1000 s at a constant potential of -1 V vs. Hg / HgO to obtain nickel foam-supported cobalt hydroxide, denoted as Co(OH)2-NF.

[0032] S3. Add 2 mL of deionized water and 0.3 mL of 0.1 mol / L chloroplatinic acid solution to a centrifuge tube. After sonication to dissolve, place Co(OH)2-NF in the centrifuge tube and place the centrifuge tube in a constant temperature water bath at 30°C for a displacement reaction for 1 h to obtain a platinum-cobalt hydroxide composite material with cobalt vacancies, denoted as Pt-Co(OH)2-NF-1.

[0033] Example 2 A method for preparing a platinum-cobalt hydroxide composite material with cobalt vacancies is the same as the preparation method in Example 1, except that the substitution reaction time in S3 is changed from 1 h to 3 h to obtain a platinum-cobalt hydroxide composite material with cobalt vacancies, denoted as Pt-Co(OH)2-NF-2.

[0034] Example 3 A method for preparing a platinum-cobalt hydroxide composite material with cobalt vacancies is the same as the preparation method in Example 1, except that the substitution reaction time in S3 is changed from 1 h to 5 h to obtain a platinum-cobalt hydroxide composite material with cobalt vacancies, denoted as Pt-Co(OH)2-NF-3.

[0035] Example 4 A method for preparing a platinum-cobalt hydroxide composite material with cobalt vacancies is the same as the preparation method in Example 1, except that the substitution reaction time in S3 is changed from 1 h to 7 h to obtain a platinum-cobalt hydroxide composite material with cobalt vacancies, denoted as Pt-Co(OH)2-NF-4.

[0036] Example 5 A method for preparing a platinum-cobalt hydroxide composite material with cobalt vacancies is the same as that in Example 1, except that the temperature of the substitution reaction in S3 is changed from 30°C to 50°C to obtain a platinum-cobalt hydroxide composite material with cobalt vacancies, denoted as Pt-Co(OH)2-NF-5.

[0037] Example 6 A method for preparing a platinum-cobalt hydroxide composite material with cobalt vacancies is the same as the preparation method in Example 5, except that the amount of chloroplatinic acid solution in S3 is replaced from 0.3 mL to 0.5 mL, and a platinum-cobalt hydroxide composite material with cobalt vacancies is obtained, denoted as Pt-Co(OH)2-NF-8.

[0038] Example 7 A method for preparing a platinum-cobalt hydroxide composite material with cobalt vacancies is the same as that in Example 5, except that the amount of chloroplatinic acid solution in S3 is replaced from 0.3 mL to 0.1 mL, thus obtaining the platinum-cobalt hydroxide composite material with cobalt vacancies. In this case, the concentration of the chloroplatinic acid aqueous solution in the system is approximately 0.0047 mol / L.

[0039] Example 8 A method for preparing a platinum-cobalt hydroxide composite material with cobalt vacancies is the same as that in Example 5, except that the amount of chloroplatinic acid solution in S3 is replaced from 0.3 mL to 0.65 mL, thus obtaining the platinum-cobalt hydroxide composite material with cobalt vacancies. In this case, the concentration of the chloroplatinic acid aqueous solution in the system is approximately 0.0245 mol / L.

[0040] Example 9 A method for preparing a platinum-cobalt hydroxide composite material with cobalt vacancies is the same as the preparation method in Example 1, except that the mass of CoCl2·6H2O in S1 is replaced from 35.7 mg to 30 mg, thus obtaining a platinum-cobalt hydroxide composite material with cobalt vacancies.

[0041] Example 10 A method for preparing a platinum-cobalt hydroxide composite material with cobalt vacancies is the same as the preparation method in Example 1, except that the mass of CoCl2·6H2O in S1 is replaced by 40 mg instead of 35.7 mg, thus obtaining a platinum-cobalt hydroxide composite material with cobalt vacancies.

[0042] Comparative Example 1 A method for preparing nickel-foamed cobalt hydroxide includes the following steps: S1. Using nickel foam as a conductive substrate, the nickel foam is cleaned and dried to obtain pretreated nickel foam for later use.

[0043] S2. 35.7 mg of CoCl2·6H2O was added to 30 mL of deionized water and ultrasonically dispersed to obtain an aqueous solution of CoCl2·6H2O. Using a three-electrode system, with pretreated nickel foam as the working electrode, a platinum sheet (1.0 cm × 1.0 cm) as the counter electrode, Hg / HgO as the reference electrode, and the aqueous solution of CoCl2·6H2O as the electrolyte, electrochemical deposition was carried out for 1000 s at a constant potential of -1 V vs. Hg / HgO to obtain nickel foam-supported cobalt hydroxide, denoted as Co(OH)2-NF.

[0044] Comparative Example 2 A method for preparing a platinum-nickel foam composite material includes the following steps: S1. Using nickel foam as a conductive substrate, the nickel foam is cleaned and dried to obtain pretreated nickel foam for later use.

[0045] S2. Add 20 mL of deionized water and 0.3 mL of 0.1 mol / L chloroplatinic acid aqueous solution to a centrifuge tube. After ultrasonic dissolution, place the pretreated nickel foam in the centrifuge tube and place the centrifuge tube in a constant temperature water bath at 50 °C for 3 h to obtain a platinum-nickel foam composite material, denoted as Pt-NF.

[0046] Comparative Example 3 A method for preparing a platinum-cobalt hydroxide composite material with cobalt vacancies is the same as the preparation method in Example 1, except that the temperature of the substitution reaction in S3 is replaced by 70°C instead of 30°C, and the reaction time is replaced by 3h instead of 1h, to obtain a platinum-cobalt hydroxide composite material with cobalt vacancies, denoted as Pt-Co(OH)2-NF-6.

[0047] Comparative Example 4 A method for preparing a platinum-cobalt hydroxide composite material with cobalt vacancies is the same as the preparation method in Example 5, except that the amount of chloroplatinic acid aqueous solution in S3 is replaced from 0.3 mL to 0.1 mL, and the reaction time is replaced from 1 h to 3 h, to obtain a platinum-cobalt hydroxide composite material with cobalt vacancies, denoted as Pt-Co(OH)2-NF-7.

[0048] Depend on Figure 3 The results show that the surface of Pt-Co(OH)2-NF-5 of the present invention is "sea urchin-shaped" nanospheres, and the Co, O and Pt elements are evenly distributed, confirming that Pt-Co(OH)2-NF-5 has been synthesized.

[0049] Depend on Figure 4From (a), (b), (c), and (d) in the figure, it is found that the XPS fitting quality of Co in Pt-Co(OH)2-NF-5 is significantly reduced, indicating that cobalt has been consumed. Figure 4 (e) shows that platinum is predominantly zero-valent, confirming that the substitution reaction has indeed occurred and platinum has been successfully reduced. Its structure lays the foundation for improving the detection performance of ammonia nitrogen.

[0050] Depend on Figure 4 As shown in (f), the present invention successfully prepared Co(OH)2-NF of Comparative Example 1 and Pt-Co(OH)2-NF-5 of the present invention.

[0051] Examples 1 to 8 of this invention all yielded platinum-cobalt hydroxide composite materials with cobalt vacancies, and the effects were parallel. The platinum-cobalt hydroxide composite materials with cobalt vacancies prepared in Examples 1 to 6, Comparative Examples 3 to 4, the nickel foam-supported cobalt hydroxide in Comparative Example 1, and the platinum-nickel foam composite material in Comparative Example 2 were used as working electrodes and applied to the electrochemical detection of ammonia nitrogen. The specific methods are as follows: Using an electrochemical workstation, a three-electrode system was constructed with platinum-cobalt hydroxide composite material with cobalt vacancies prepared in Examples 1-6 and Comparative Examples 3-4, cobalt hydroxide supported by nickel foam in Comparative Example 1, and platinum-nickel foam composite material in Comparative Example 2 as working electrodes, a platinum sheet (1.0 cm × 1.0 cm) as the counter electrode, and a saturated Hg / HgO electrode as the reference electrode, and 1 mol / L KOH solution as the electrolyte.

[0052] Cyclic voltammetry (CV) was used with a scan rate of 50 mV / s and a potential window of -1 V to 0.4 V. The ammonia source was 0.1 mol / L ammonium chloride. Before the cyclic voltammetry test, the working electrode was activated in a 1 mol / L KOH solution, and the number of scan cycles was 30. The test results are as follows: Figure 1 As shown.

[0053] Depend on Figure 1 As shown in (a), (b), (c), and (d), when using the platinum-cobalt hydroxide composite materials with cobalt vacancies from Examples 1 to 3, Comparative Examples 3 to 4, and the nickel foam-supported cobalt hydroxide from Comparative Example 1 and the platinum-nickel foam composite material from Comparative Example 2 as working electrodes, the ammonia-nitrogen electrocatalytic reaction yielded ammonia oxidation peak currents of 34.62 mA, 48.64 mA, 46.78 mA, 41.17 mA, 57.74 mA, 47.54 mA, 26.40 mA, 15.56 mA, 25.96 mA, and 16.35 mA, respectively.

[0054] Figure 1 The results showed that PtCl6 2- With Co 2+The displacement reaction process is significantly affected by reaction temperature, time, and chloroplatinic acid solution concentration: excessively high or low reaction temperatures alter reaction kinetics, leading to a mismatch in the zero-valent platinum deposition rate; deposition that is too fast or too slow is detrimental to catalytic activity. Too short a reaction time results in insufficient platinum deposition, while too long a time easily causes platinum nanoparticle aggregation, both of which weaken the performance of platinum-cobalt hydroxide composites with cobalt vacancies. Excessively high chloroplatinic acid concentrations accelerate the deposition of surface Co. 2+ Displacement and rapid platinum deposition can hinder the reaction from proceeding further, while too low a concentration will not be able to form sufficient platinum active sites and cobalt vacancies, making it difficult to achieve optimal catalytic performance.

[0055] The electrochemical detection activity of ammonia nitrogen was tested using Pt-Co(OH)₂-NF₅ as the sensitive electrode. The test method was as follows: a three-electrode system was constructed using Pt-Co(OH)₂-NF₅ as the working electrode, a platinum sheet (1.0 cm × 1.0 cm) as the counter electrode and saturated electrode, an Hg / HgO electrode as the reference electrode, 1 mol / L KOH solution as the electrolyte, and 0.1 mol / L ammonium chloride as the ammonia nitrogen source. Differential pulse voltammetry (DPV) was used for the test, with a potential window of -0.8 V vs. Hg / HgO to 0.2 V vs. Hg / HgO. Before the DPV test, the working electrode was activated in 1 mol / L KOH solution using cyclic voltammetry, with a potential window of -1 V to 0.4 V. The scan number was 30 cycles, and the scan rate was 50 mV / s. The test results are shown below. Figure 2 As shown. Figure 2 The results show that, using the Pt-Co(OH)2-NF-5 of the present invention as the ammonia nitrogen sensitive electrode, the linear range of ammonia nitrogen concentration is 5 μmol / L to 899 μmol / L, the sensitivity is 17.485 μA / (μmol / L), and the detection limit is 1.47 μmol / L.

[0056] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

Claims

1. A platinum-cobalt hydroxide composite material with cobalt vacancies, characterized in that, The platinum-cobalt hydroxide composite material with cobalt vacancies includes nickel foam, Pt nanoparticles, and cobalt hydroxide. Cobalt hydroxide is deposited on the nickel foam, the Pt nanoparticles are deposited on the surface of the cobalt hydroxide, and cobalt vacancies exist in the crystal lattice of the cobalt hydroxide.

2. A method for preparing the platinum-cobalt hydroxide composite material with cobalt vacancies as described in claim 1, characterized in that, Includes the following steps: Using nickel foam as the working electrode, a three-electrode system consisting of a working electrode, a reference electrode, and a counter electrode was formed. An aqueous solution of soluble cobalt salt was used as the electrolyte. One end of the three-electrode system was immersed in the electrolyte, and the other end was electrically connected to an electrochemical workstation for electrochemical deposition to form cobalt hydroxide supported by nickel foam, thus obtaining Co(OH)2-NF. When Co(OH)₂-NF is immersed in a chloroplatinic acid aqueous solution, the Co in Co(OH)₂... 2+ Pt in chloroplatinic acid aqueous solution 4+ A displacement reaction occurs, during which Co 2+ Oxidized to Co 3+ Co 3+ Dissolved, forming cobalt vacancies, while Pt 4+ The particles are reduced to Pt nanoparticles and deposited in situ on the surface of cobalt hydroxide to obtain a platinum-cobalt hydroxide composite material with cobalt vacancies.

3. The method for preparing the platinum-cobalt hydroxide composite material with cobalt vacancies according to claim 2, characterized in that, The aqueous solution of the soluble cobalt salt is a CoCl2·6H2O aqueous solution, and the mass concentration of the CoCl2·6H2O aqueous solution is 1 mg / mL to 1.33 mg / mL.

4. The method for preparing the platinum-cobalt hydroxide composite material with cobalt vacancies according to claim 2, characterized in that, The concentration of chloroplatinic acid aqueous solution is 0.005 mol / L to 0.025 mol / L.

5. The method for preparing the platinum-cobalt hydroxide composite material with cobalt vacancies according to claim 2, characterized in that, The electrochemical deposition conditions are: electrodeposition at a constant potential of -0.9V to -1.2V for 500s to 1500s.

6. The method for preparing the platinum-cobalt hydroxide composite material with cobalt vacancies according to claim 2, characterized in that, The conditions for the displacement reaction are: reaction at 25℃~50℃ for 1h~7h.

7. The method for preparing the platinum-cobalt hydroxide composite material with cobalt vacancies according to claim 2, characterized in that, The nickel foam was then ultrasonically cleaned with acetone, hydrochloric acid, ethanol, and deionized water in sequence, and then rinsed with deionized water until neutral and dried.

8. The application of the platinum-cobalt hydroxide composite material with cobalt vacancies as described in claim 1 in the preparation of a sensitive electrode for electrochemical detection of ammonia nitrogen.

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