Ammonia nitrogen electrochemical sensitive electrode based on platinum-zinc-copper ternary alloy and preparation method thereof

Abstract

The invention discloses an ammonia nitrogen electrochemical sensitive electrode based on a platinum-zinc-copper ternary alloy and a preparation method thereof, and belongs to the technical field of electrochemical sensing. The preparation method comprises the following steps: firstly, dissolving platinum salt, copper salt and zinc salt in deionized water according to a certain proportion to prepare a precursor solution for electrodeposition; and then, constructing a three-electrode system by taking the cleaned carbon cloth substrate as a working electrode, a platinum sheet as a counter electrode and Ag / AgCl as a reference electrode, and depositing a platinum-zinc-copper ternary nano-alloy sensitive material on the carbon cloth substrate through an electrochemical cyclic voltammetry to obtain the ammonia nitrogen electrochemical sensitive electrode based on the platinum-zinc-copper ternary alloy. Finally, the electrode is used for sensitive detection of ammonia nitrogen in water. The detection performance of the platinum-zinc-copper ternary alloy electrode on ammonia nitrogen is superior to that of a sensitive electrode of the same type, and the platinum-zinc-copper ternary alloy electrode has the advantages of low cost, high sensitivity, wide linear range, low detection limit and the like, shows good repeatability and interference resistance, and can realize rapid detection and real-time monitoring on ammonia nitrogen in water.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical sensing, and particularly relates to an ammonia nitrogen electrochemical sensitive electrode based on a platinum-zinc-copper ternary alloy and a preparation method thereof. Background Art

[0002] The enrichment of ammonia nitrogen pollutants (existing in the forms of NH4 + and NH3) in water bodies is an important inducement for water eutrophication and aquatic organism toxicity effects. In intensive aquaculture systems, the exceeding standard of ammonia nitrogen concentration will directly threaten the survival safety of economic species such as fish and shrimp. Among them, crustaceans are particularly sensitive to the toxicity of ammonia nitrogen, and long-term exposure will lead to mass death events and cause significant economic losses. Therefore, the development of efficient and accurate water ammonia nitrogen detection technology is a prerequisite for implementing pollution monitoring and control.

[0003] Current ammonia nitrogen detection technologies mainly include optical detection methods such as Nessler's reagent spectrophotometry and salicylic acid spectrophotometry, as well as analysis means such as gas-phase molecular absorption spectrometry and electrochemical detection methods. Although the optical method has the advantage of low detection limit, it generally has technical bottlenecks such as cumbersome pretreatment steps, high professional requirements for operation, and long detection cycle, and it is difficult to achieve on-site rapid detection. At the same time, some methods involve the use of highly toxic reagents, which are prone to cause secondary pollution problems. In contrast, electrochemical detection technology shows significant advantages in realizing in-situ rapid detection of water ammonia nitrogen due to its excellent sensitivity, convenient operation, and controllable cost.

[0004] The detection performance of electrochemical detection technology is mainly determined by the ammonia nitrogen sensitive electrode. The noble metal platinum (Pt) is a classic ammonia nitrogen sensitive electrode material, which can provide high detection sensitivity, a wide detection range, and a low detection limit. However, Pt still faces multiple technical obstacles in the actual application field: on the one hand, the high cost of the noble metal Pt restricts the large-scale application of ammonia nitrogen sensors; on the other hand, the pure Pt electrode has inherent defects such as weak anti-interference ability (poor selectivity to coexisting substances) and the active sites are easily poisoned by intermediate products of ammonia oxidation. Research shows that by constructing a Pt-based multi-element alloy system, the performance of the Pt-based electrode can be effectively improved by relying on the synergistic effect of geometric effect and electronic effect; in addition, alloying can effectively reduce the use of noble metal platinum and reduce the preparation cost. Therefore, the development of a Pt-based alloy sensitive electrode is considered an effective technical path to break through the performance bottleneck of the existing Pt-based electrode. Summary of the Invention

[0005] The object of the present invention is to provide an ammonia nitrogen electrochemical sensitive electrode based on a platinum-zinc-copper ternary alloy and a preparation method thereof. The present invention uses carbon cloth as a substrate, and modifies a platinum-zinc-copper nanoalloy material on its surface by an electrodeposition method to construct a high-performance ammonia nitrogen electrochemical sensitive electrode. The ammonia nitrogen sensitive electrode obtained by the present invention has the advantages of high sensitivity, low detection limit, strong anti-interference ability and good repeatability.

[0006] The present invention prepares a PtZnCu-CC working electrode by in-situ electrodepositing a platinum-zinc-copper nanoalloy modification material on a carbon cloth substrate through a one-step electrochemical deposition method, and together with an Ag / AgCl reference electrode and a platinum sheet counter electrode, forms a three-electrode test system. Using a 1M KOH solution as the electrolyte, an ammonia nitrogen electrochemical sensor in water is constructed.

[0007] The preparation method of an ammonia nitrogen electrochemical sensitive electrode based on a platinum-zinc-copper ternary alloy according to the present invention comprises the following steps:

[0008] (1) Clean the carbon cloth substrate;

[0009] (2) Use chloride salts, zinc salts and copper salts as solutes and deionized water as a solvent to prepare a precursor solution for electrodeposition;

[0010] (3) Using the carbon cloth substrate obtained in step (1) as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode, and using the precursor solution obtained in step (2) as the electrolyte, deposit a platinum-zinc-copper nanoalloy on the carbon cloth substrate by cyclic voltammetry. After rinsing the obtained carbon cloth substrate with deionized water and drying it, an ammonia nitrogen electrochemical sensitive electrode (PtZnCu-CC) based on a platinum-zinc-copper ternary alloy is obtained;

[0011] Preferably, in the process of cleaning the carbon cloth in step (1), the reagent used is one or more of ethanol, toluene, acetone, ethanol, and hydrochloric acid;

[0012] Preferably, in the process of cleaning the carbon cloth in step (1), the cleaning time of each reagent is 5-10 min, and then it is rinsed clean with deionized water;

[0013] Preferably, in step (2), the copper salt is copper sulfate pentahydrate (CuSO4·5H2O), copper sulfate (CuSO4) or copper chloride (CuCl2);

[0014] Preferably, in step (2), the zinc salt is zinc sulfate heptahydrate (ZnSO4·7H2O), zinc sulfate (ZnSO4) or zinc chloride (ZnCl2);

[0015] Preferably, in step (2), the platinum salt is chloroplatinic acid (H2PtCl6) or potassium chloroplatinate (K2PtCl6);

[0016] The concentration range of H2PtCl6 or K2PtCl6 in the precursor solution is 3 - 5 mM, the elemental molar ratio of zinc to copper is 1 - 10:1, and the elemental molar ratio of platinum to the sum of zinc and copper is 1 - 10:1;

[0017] Preferably, in step (3), the starting voltage of cyclic voltammetry is -0.6 to -0.8 V (vs. Ag / AgCl), the termination voltage is 0.6 to 0.8 V (vs. Ag / AgCl), the deposition cycle is 5 - 50 cycles, and the scanning rate is 20 - 50 mV / s.

[0018] The platinum-zinc-copper ternary nanoalloy sensitive electrode prepared by the present invention for detecting ammonia nitrogen in water has the following advantages:

[0019] 1) The present invention uses in-situ electrochemical cyclic voltammetry to deposit the platinum-zinc-copper ternary nanoalloy material on the carbon cloth substrate. The preparation process is simple, the performance is stable, and the repeatability is good; moreover, the self-supporting structure of the carbon cloth substrate eliminates the use of a binder and avoids the problem of reduced detection performance caused by the binder;

[0020] 2) In the present invention, zinc and copper elements are relatively inexpensive transition metals. The alloying of zinc and copper with platinum reduces the use of precious metal platinum and lowers the preparation cost; and due to the synergistic effect among copper, zinc, and platinum, the detection ability is effectively improved;

[0021] 3) The ammonia nitrogen electrochemical sensitive electrode based on the platinum-zinc-copper ternary alloy described in the present invention has the advantages of low detection limit, high sensitivity, wide detection range, and strong anti-interference ability. Description of the Drawings

[0022] Figure 1 Scanning electron microscope photos of carbon cloth-supported Pt and Pt-based nanoalloy electrodes; Figure 1 (a) and Figure 1 (b) correspond to the platinum electrode (Pt-CC), Figure 1 (c) and Figure 1 (d) correspond to the platinum-zinc nanoalloy electrode (PtZn-CC), Figure 1 (e) and Figure 1 (f) correspond to the platinum-copper nanoalloy electrode (PtCu-CC), Figure 1 (g) and Figure 1 (h) correspond to the platinum-zinc-copper nanoalloy electrode (PtZnCu-CC);

[0023] As Figure 1 shown, from the low-magnification photos Figure 1 (a), Figure 1 (c), Figure 1 (e) and Figure 1It can be seen from (g) that the Pt-based sensitive materials can all cover the surface of the carbon cloth substrate relatively uniformly. It can be seen from the high-magnification photos that Figure 1 (b) and Figure 1 Pt and PtZn shown in (d) both appear in the form of nanosheets, and these small nanosheets stack to form flower clusters, where the sizes of the PtZn nanosheets and nanoclusters slightly increase; Figure 1 The PtZnCu material shown in (f) stacks together in the form of irregular spherical particles; Figure 1 PtCu in (h) presents a nanospherical shape and stacks disorderly with each other. It can be seen that after alloying Cu atoms with Pt, the original surface morphology of Pt changes significantly, and it can also regulate the morphology of the PtZnCu ternary alloy, while Zn atoms have a certain regulating effect on the size of the nanomaterials. Under the combined action of Cu and Zn atoms, it is beneficial to increase the specific surface area of the PtZnCu nanoalloy, and then the electrochemically active sites can be increased.

[0024] Figure 2 (a) shows the TEM image (a), HR-TEM image (b), and EDS element mapping images (c-f) of the PtZn1Cu1-CC electrode prepared in Example 1;

[0025] As Figure 2 (a) shows, a partial spherical morphology can still be seen at the edges of the aggregated PtZnCu nanomaterials in the TEM photo, with a diameter of about 100 nm, which is similar to the Figure 1 results of the SEM photo in Figure 2 (b), it can be seen from the high-magnification TEM photo that the lattice fringes of the PtZnCu alloy are continuous and uniform, and the interplanar spacings are 0.220 nm and 1.94 nm, corresponding to the (111) and (200) crystal planes of the PtZnCu alloy respectively. It can be seen that the lattice spacings of the (111) and (200) crystal planes of the PtZnCu nanoalloy material are both smaller than those of the (111) and (200) crystal planes of Pt, which is due to the fact that the atomic radii of Zn and Cu elements are both smaller than that of Pt element. In addition, it can be seen from Figure 2 (c-f) that Pt, Zn, and Cu elements are uniformly distributed on the material surface without obvious aggregation; combined with the analysis of the TEM results in Figure b, it can be inferred that Zn and Cu atoms enter the lattice of Pt in a substitutional way to form a single-phase PtZnCu alloy.

[0026] Figure 3 Cyclic voltammograms (a-e) and response current value △I bar chart (f) of the Pt alloy electrodes prepared with different Zn and Cu ratio precursor solutions in Examples 1-5 before and after adding 10 mM ammonia nitrogen to 1 M KOH electrolyte;

[0027] AsFigure 3 In the 1M KOH electrolyte containing 10 mM ammonia, the ammonia-nitrogen response current value of the ternary PtZnCu alloy electrode is further improved compared with those of the binary PtZn and PtCu alloy electrodes. When the ratio of Zn to Cu in the precursor solution is 1:1, the PtZn1Cu1-CC electrode prepared by cyclic voltammetry has the largest response current value to ammonia-nitrogen and the highest sensitive response to ammonia-nitrogen.

[0028] Figure 4 Differential pulse voltammetry test curves (a) and peak current vs. NH4Cl concentration curves (b) of the PtZn1Cu1-CC electrode prepared in Example 1 in NH4Cl solutions with different concentrations;

[0029] Figure 4 (a) It can be seen that in the differential pulse voltammetry (DPV) curve, the peak between -0.5 V and -0.2 V increases with the increase of the NH4Cl concentration; Figure 4 (b) It can be seen that the peak current shows a two-segment linear variation relationship with the increase of the NH4Cl concentration. When the ammonia-nitrogen concentration is 0.5 - 60 μM, the linear regression equation is: I pa (μA) = 23.9x + 0.142 (R 2 = 0.998, 0.5 μM - 60 μM), and the sensitivity is 23.9 μA μM -1 cm -2 ; when the ammonia-nitrogen concentration is 60 - 1000 μM, the linear regression equation is: I pa (μA) = 4.44x + 1.36 (R 2 = 0.993, 60 μM - 1000 μM), and the sensitivity is 4.44 μA μM -1 cm -2 .

[0030] Figure 5 Test diagrams of the repeatability and anti-interference ability of the PtZn1Cu1-CC electrode prepared in Example 1; among them, Figure 5 (a) is a comparison diagram of the repeated test results of 7 PtZn1Cu1-CC electrodes, Figure 5 (b) is an anti-interference test diagram of the PtZn1Cu1-CC electrode;

[0031] As Figure 5 (a) shows, 7 PtZn1Cu1-CC electrodes were repeatedly tested 7 times, and the relative standard deviation of the peak current was 2.32%; as Figure 5 (b) shows, common interfering ions (NO2 - , SO4 2- , SO3 2- , HCO3 - , CO32- and C2O4 2- ) had no obvious effect on the ammonia nitrogen sensitive response of the PtZn1Cu1-CC electrode, indicating that the PtZn1Cu1-CC electrode has excellent anti-interference performance in ammonia nitrogen detection. Detailed implementation manners

[0032] Example 1

[0033] The preparation method of a ternary ammonia nitrogen electrochemical sensitive electrode based on a carbon cloth substrate platinum-zinc-copper nanoalloy is as follows:

[0034] a) Appropriately cut the carbon cloth substrate (CC) to a size of 1.0 cm × 0.5 cm, ultrasonically clean it successively with toluene, acetone and ethanol, then ultrasonically clean it with hydrochloric acid, and finally wash it with deionized water until neutral; the ultrasonic cleaning time for each time is 5 minutes;

[0035] b) Prepare 50 mL of a mixed deionized aqueous solution of 0.4 mM CuSO4, 0.4 mM ZnSO4 and 4 mM H2PtCl6 as a precursor solution, and the molar ratio of platinum, zinc and copper elements is 10:1:1;

[0036] c) Adopt a three-electrode system, use the carbon cloth substrate obtained in step (1) as the working electrode, a platinum sheet (1.0 cm × 1.0 cm) as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Use the precursor solution obtained in step (2) as the electrolyte, and deposit the platinum-zinc-copper nanoalloy on the carbon cloth substrate by cyclic voltammetry. The potential range is -0.8 to 0.6 V (vs. Ag / AgCl), the deposition cycle is 25 cycles, and the scanning rate is 50 mV / s; rinse the obtained carbon cloth substrate with deionized water and then dry it to obtain an ammonia nitrogen electrochemical sensitive electrode based on a platinum-zinc-copper ternary alloy, denoted as PtZn1Cu1-CC;

[0037] d) Use the obtained PtZn1Cu1-CC as the working electrode, a platinum sheet (1.0 cm × 1.0 cm) as the counter electrode, and a Hg / HgO electrode as the reference electrode. Use 1 M KOH solution as the electrolyte to construct an electrochemical sensor and conduct an electrochemical ammonia nitrogen detection test (using ammonium chloride as the ammonia nitrogen source). Use cyclic voltammetry (CV) to test the CV curves of the PtZn1Cu1-CC electrode before and after adding 10 mM ammonia nitrogen, and the potential range is -0.8 V to -0.2 V (vs. Hg / HgO) (as Figure 3 shown). Before the test, use the CV method to activate the electrode, and the potential range is -0.8 V to -0.2 V (vs. Hg / HgO). The number of cycling is 30 cycles, and the scanning speed is 50 mv s -1 . The CV test results show that: the response current value of the electrode prepared by the method of the present invention to 10 mM ammonia nitrogen is 5.216 mA.

[0038] The test was carried out by differential pulse voltammetry (DPV), and the potential range was -0.8 V to -0.1 V (vs. Hg / HgO). The DPV test results showed that the maximum sensitivity of the sensor prepared by the method of the present invention for ammonia nitrogen detection was 23.9 μA / μM -1 cm -2 , the detection range was 0.5 - 250 μM, and when the signal / noise = 3 (S / N = 3), the detection limit was 8.6 nM (as Figure 4 shown). In addition, the sensor prepared by the method of the present invention had good repeatability and anti-interference ability (as Figure 5 shown);

[0039] Example 2

[0040] a) The cleaning process of the carbon cloth was the same as that in Example 1;

[0041] b) 50 mL of a mixed deionized aqueous solution of 0.2 mM CuSO4, 0.6 mM ZnSO4, and 4 mM H2PtCl6 was prepared as the precursor solution, and the molar ratio of zinc to copper elements was 3:1;

[0042] c) The process of electro-depositing platinum-zinc-copper nanoalloy on the carbon cloth substrate to prepare the PtZn3Cu1-CC electrode was the same as that in Example 1;

[0043] d) The CV test process was the same as that in Example 1, and the test results showed that the response current value of the electrode prepared by the method of the present invention to 10 mM ammonia nitrogen was 4.635 mA.

[0044] Example 3

[0045] a) The cleaning process of the carbon cloth was the same as that in Example 1;

[0046] b) 50 mL of a mixed deionized aqueous solution of 0.6 mM CuSO4, 0.2 mM ZnSO4, and 4 mM H2PtCl6 was prepared as the precursor solution, and the molar ratio of zinc to copper elements was 1:3;

[0047] c) The process of electro-depositing platinum-zinc-copper nanoalloy on the carbon cloth substrate to prepare the PtZn1Cu3-CC electrode was the same as that in Example 1;

[0048] d) The CV test process was the same as that in Example 1, and the test results showed that the response current value of the electrode prepared by the method of the present invention to 10 mM ammonia nitrogen was 4.210 mA.

[0049] Example 4

[0050] a) The cleaning process of the carbon cloth was the same as that in Example 1;

[0051] b) Prepare 50 mL of a mixed deionized aqueous solution containing 0.7 mM of CuSO4, 0.1 mM of ZnSO4, and 4 mM of H2PtCl6 as the precursor solution, with the molar ratio of zinc to copper being 1:7;

[0052] c) The process of electro-depositing platinum-copper nanoalloy on the carbon cloth substrate to prepare the PtCu-CC electrode is the same as in Example 1;

[0053] d) The CV test process is the same as in Example 1. The test results show that the response current value of the electrode prepared by the method of the present invention to 10 mM ammonia nitrogen is 4.018 mA.

[0054] Example 5

[0055] a) The cleaning process of the carbon cloth is the same as in Example 1;

[0056] b) Prepare 50 mL of a mixed deionized aqueous solution containing 0.1 mM of CuSO4, 0.7 mM of ZnSO4, and 4 mM of H2PtCl6 as the precursor solution, with the molar ratio of zinc to copper being 7:1;

[0057] c) The process of electro-depositing platinum-copper nanoalloy on the carbon cloth substrate to prepare the PtZn-CC electrode is the same as in Example 1;

[0058] d) The CV test process is the same as in Example 1. The test results show that the response current value of the electrode prepared by the method of the present invention to 10 mM ammonia nitrogen is 4.118 mA.

Claims

1. A preparation method of an ammonia nitrogen electrochemical sensitive electrode based on a platinum-zinc-copper ternary alloy, the steps are as follows: (1) Clean the carbon cloth substrate; (2) Use chloride salts, zinc salts and copper salts as solutes and deionized water as a solvent to prepare a precursor solution for electrochemical deposition; (3) Use the carbon cloth substrate obtained in step (1) as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Use the precursor solution obtained in step (2) as the electrolyte, and deposit platinum-zinc-copper nanoalloy on the carbon cloth substrate by cyclic voltammetry. After rinsing the obtained carbon cloth substrate with deionized water and drying it, an ammonia nitrogen electrochemical sensitive electrode based on a platinum-zinc-copper ternary alloy is obtained.

2. The preparation method of an ammonia nitrogen electrochemical sensitive electrode based on a platinum-zinc-copper ternary alloy as described in claim 1, characterized in that: During the carbon cloth cleaning process in step (1), the reagent used is one or more of ethanol, toluene, acetone, ethanol, and hydrochloric acid; the cleaning time for each reagent is 5-10 minutes, and then it is rinsed clean with deionized water.

3. The preparation method of an ammonia nitrogen electrochemical sensitive electrode based on a platinum-zinc-copper ternary alloy as described in claim 1, characterized in that: In step (2), the copper salt is copper sulfate pentahydrate (CuSO4·5H2O), copper sulfate (CuSO4), or copper chloride (CuCl2); the zinc salt is zinc sulfate heptahydrate (ZnSO4·7H2O), zinc sulfate (ZnSO4), or zinc chloride (ZnCl2); the platinum salt is chloroplatinic acid (H2PtCl6) or potassium chloroplatinate (K2PtCl6).

4. The preparation method of an ammonia nitrogen electrochemical sensitive electrode based on a platinum-zinc-copper ternary alloy according to claim 1, characterized in that: In the precursor solution in step (2), the concentration range of H2PtCl6 or K2PtCl6 is 3-5 mM, the elemental molar ratio of zinc to copper is 1-10:1, and the elemental molar ratio of platinum to the sum of zinc and copper is 1-10:

1.

5. The preparation method of an ammonia nitrogen electrochemical sensitive electrode based on a platinum-zinc-copper ternary alloy as described in claim 1, characterized in that: In step (3), the starting voltage of cyclic voltammetry is -0.6 to -0.8 V (vs. Ag / AgCl), the termination voltage is 0.6 to 0.8 V (vs. Ag / AgCl), the deposition cycle is 5 to 50 cycles, and the scanning rate is 20 to 50 mV / s.

6. A preparation method of an ammonia nitrogen electrochemical sensitive electrode based on a platinum-zinc-copper ternary alloy, characterized in that: It is prepared by the method described in any one of claims 1 to 5.

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