Copper / cobalt / sulfur modified nickel-based self-supporting catalytic material and application thereof in electrochemical detection of nitrite

Abstract

The invention relates to the field of nitrite electrochemical detection. The nitrite electrochemical detection material is prepared by a two-step synthesis method of firstly electro-depositing and then roasting. A traditional sensor often needs to use an adhesive in the material preparation process, which not only influences the conductivity of the sensor, but also possibly interferes with a detection result. The self-supporting material provided by the invention effectively avoids the use of an adhesive. The material has excellent conductivity, and has higher sensitivity and lower detection limit compared with a conventional powdery nitrite sensor.

Description

Technical Field

[0001] The invention relates to the field of nitrite electrochemical detection sensors, and in particular to a copper / cobalt / sulfur modified nickel-based self-supporting catalytic material and application thereof. Background Art

[0002] Nitrite is widely used as an additive for various meat products to maintain and enhance the color and taste of meat products. For meat products, the addition of nitrite can inhibit the reproduction of microorganisms, especially Clostridium botulinum. Under acidic conditions, nitrite can be decomposed by microorganisms into unstable nitrous acid, which can easily decompose into nitric oxide. Then, nitric oxide further reacts with myoglobin to produce bright red stable nitromyoglobin, which plays a role in protecting the color. Excessive nitrite will react with gastric acid to produce nitrogen oxides (N2O3). N2O3 will further combine with metabolites of human proteins to produce potential carcinogens n-nitrosamines. At the same time, nitrite has a strong oxidizing ability under acidic conditions, which can oxidize hemoglobin in the blood into methemoglobin, thereby reducing the oxygen transport capacity of hemoglobin and leading to methemoglobinemia. Since excessive intake of nitrite is harmful to human health, many countries have formulated corresponding standards for the content of nitrite in additives.

[0003] The detection technologies of nitrite include spectrophotometry, chromatography, chemiluminescence, capillary electrophoresis and electrochemical sensors. Spectrophotometry has the advantages of low cost and simple operation, but it also has disadvantages such as fuzzy reaction time, long sample pretreatment time, and susceptibility to ion interference. Chemiluminescence is based on the principle that the molecular luminescence intensity is linearly related to the nitrite concentration. It has the advantages of wide linear range and low cost, but the chemiluminescent reagents that can be used for detection are limited. The stability and reproducibility are poor. Gas chromatography or gas chromatography-mass spectrometry (GC-MS) has high selectivity and sensitivity, but its sample preparation procedure is complicated and the instrument cost is high. Compared with the above detection methods, electrochemical detection of nitrite has the advantages of low cost, simple operation, easy miniaturization, fast response speed and high accuracy. Electrochemical sensing of nitrite is mainly based on the electrical parameters generated by the oxidation and reduction of nitrite on the electrode surface. In neutral and weakly acidic aqueous solutions, the reaction is usually: NO2 - +H2O→NO3 - +2H + +2e - .

[0004] Therefore, a copper / cobalt / sulfur modified nickel-based self-supporting catalytic material was invented and designed for electrochemical detection of nitrite. Summary of the invention

[0005] Technical problems solved by the present invention:

[0006] The copper / cobalt / sulfur modified nickel-based self-supporting catalytic material is prepared by first electrodeposition and then calcination. It avoids the use of adhesives, making it have excellent conductivity and a lower detection limit, thus solving the problem of high detection limit of previous catalysts.

[0008] The copper / cobalt / sulfur modified nickel-based self-supporting catalytic material is first obtained by electrodeposition and then calcination. In short, clean commercial metal foam nickel is used as the working electrode, platinum sheet is used as the counter electrode, and saturated calomel electrode is used as the reference electrode, and is electrodeposited in an electrolyte containing copper / cobalt / sulfur. The final sample is then calcined. The final product is labeled Cu / Co / S-NF-x (where x=1, 2, 3 represents specific synthesis parameters)

[0009] The benefits of the present invention are:

[0010] The copper / cobalt / sulfur modified self-supporting catalytic material obtained by the present invention has excellent electrical conductivity and can identify nitrite with a minimum concentration of 2 μM in the application of electrochemical detection of nitrite. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 CV curve of Cu / Co / S-NF-x;

[0012] Figure 2 It curve of Cu / Co / S-NF-2 with continuous addition of nitrite;

[0013] Figure 3 It is the linear relationship between the it current response of Cu / Co / S-NF-2 and the amount of nitrite used; DETAILED DESCRIPTION

[0014] In order to more clearly explain the purpose, technical scheme and advantages of the embodiments of the present invention, the technical scheme in the embodiments will be described in detail below. If specific conditions are not particularly specified, the operation will be carried out according to the usual conditions or the recommendations of the manufacturer. When the manufacturer of the reagent or instrument is not particularly specified, it refers to the conventional products that can be purchased on the market.

[0015] Example

[0016] A copper / cobalt / sulfur modified nickel-based self-supporting catalytic material (Cu / Co / S-NF-x) and a preparation method thereof, comprising the following steps:

[0017] (1) Electrolyte preparation: Prepare solution A (use pure water to prepare 0.1 mol / L copper nitrate solution) and solution B (use ethanol-water mixture (the volume ratio of ethanol to water is 2:8) to prepare a mixed solution containing cobalt nitrate and thiourea (the molar concentration ratio of cobalt nitrate to thiourea is 0.1 mol / L:0.5 mol / L)). Take 30 mL of solution A and 10 mL of solution B and mix them to prepare the electrolyte required for electrodeposition.

[0018] (2) Electrodeposition: Commercial nickel foam was used as the working electrode, platinum sheet as the counter electrode, and saturated calomel electrode as the reference electrode. The voltage was set to -1 V (V vs. SCE) and the polarization time was 600-2700 seconds.

[0019] (3) Calcination: The conditions required for calcination are: the ambient temperature is set at 350°C and the calcination time is 2 hours.

[0020] The catalyst electroplated for 600 seconds was labeled Cu / Co / S-NF-1, the catalyst electroplated for 1200 seconds was labeled Cu / Co / S-NF-2, and the catalyst electroplated for 2700 seconds was labeled Cu / Co / S-NF-3.

[0021] The specific parameters for the preparation of each catalyst in the examples are shown in Table 1-2.

[0022] Table 1 Calcination treatment environment temperature and treatment time

[0023]

[0024] Table 2 Calcination treatment environment temperature and treatment time

[0025]

[0026] Test example

[0027] 1.CV and IT test

[0028] The self-supporting nanocatalytic material in the embodiment was subjected to a nitrite response test. The test process is as follows: a nitrite concentration of 4 mM was added to a 0.1 M PBS (pH = 7) electrolyte, a standard three-electrode configuration was used, Cu / Co / S-NF-x was used as the anode, a platinum electrode was used as the cathode, and a saturated calomel electrode was used as the reference electrode, and an electrochemical cyclic voltammetry (CV) test was performed on it using a Chenhua CH760E electrochemical workstation, and the voltage window was set to 0.4-1.4 V (V vs. SCE).

[0029] Figure 1This is the CV curve of Cu / Co / S-NF-x. The CV curve reflects the strength of the material's response to nitrite under different voltage conditions. Generally speaking, the higher the current signal, the more intense the nitrite oxidation. It can be seen from the figure that Cu / Co / S-NF-2 has the most obvious current response, indicating that more nitrite in Cu / Co / S-NF-2 reacts on the electrode surface.

[0030] Figure 2 This is the timing it current curve of Cu / Co / S-NF-2. The detection limit and sensitivity of the sensor were evaluated by the chronoamperometric experiment. The voltage was kept at 0.8-1.2V, and nitrite was added to the PBS electrolyte at a time interval of 30 seconds. With the addition of nitrite, the current was observed to increase in a step-by-step manner. When the control voltage was 1.0V, the detection limit was the lowest and the sensitivity was the highest.

[0031] Figure 3 The fitting curve of the current response of Cu / Co / S-NF-2 with the change of nitrite concentration when the control voltage is 1V. The fitting curve is divided into two different concentration ranges (0.2mM-0.11mM and 0.11mM-1.51mM), and both show excellent current / concentration linear relationship, and R 2 All are greater than 0.994.

[0032] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A copper / cobalt / sulfur modified nickel-based self-supporting catalytic material, characterized in that: The material is obtained by electrodeposition followed by calcination.

2. According to claim 1, when preparing the catalyst, the electrolyte required for electrodeposition is characterized by: (1) Solution A: Prepare 0.1 mol / L copper nitrate solution with pure water. (2) Solution B: A mixed solution containing cobalt nitrate and thiourea (the molar concentration ratio of cobalt nitrate to thiourea is 0.1 mol / L:0.5 mol / L) is prepared with ethanol-water (the volume ratio of ethanol to water is 2:8). (3) Take 30 mL of solution A and 10 mL of solution B and mix them to prepare the electrolyte required for electrodeposition.

3. According to claim 1, the electrodeposition conditions are: commercial nickel metal foam is used as the working electrode, platinum sheet is used as the counter electrode, saturated calomel electrode is used as the reference electrode, the voltage is set to -1V (V vs. SCE), and the polarization time is 600-2700 seconds.

4. According to claim 1, when preparing the catalyst, the conditions required for calcination are: the ambient temperature is set to 350°C and the calcination time is 2 hours.

5. Use of the copper / cobalt / sulfur modified nickel-based self-supporting catalytic material according to any one of claims 1 to 4 as a nitrite electrochemical detection sensor.

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