阅读说明：本技术 一种可同时检测亚硫酸盐和亚硝酸盐的纳米多孔钴镍复合电极及其制备方法 (Nano-porous cobalt-nickel composite electrode capable of simultaneously detecting sulfite and nitrite and preparation method thereof ) 是由 奚亚男 胡淑锦 于 2020-05-29 设计创作，主要内容包括：本发明提供了一种可同时检测亚硫酸盐和亚硝酸盐的纳米多孔钴镍复合电极及其制备方法。本发明通过缓冲层法以及碱性体系去合金法,以多孔的碳纤维纸为基底,构建了纳米多孔钴复合电极,该复合电极兼具碳纤维纸的大孔结构以及金属钴的纳米孔结构,极大的提高了氧化还原反应过程中离子传输和电子转移的速度,而且金属钴与镍的协同作用,共同促进了反应物的催化,表现了对污染物亚硫酸盐和亚硝酸盐检测较高的传感响应性能。(The invention provides a nano porous cobalt-nickel composite electrode capable of detecting sulfite and nitrite simultaneously and a preparation method thereof. According to the invention, the porous carbon fiber paper is used as a substrate through a buffer layer method and an alkaline system dealloying method, the nano porous cobalt composite electrode is constructed, the composite electrode has a macroporous structure of the carbon fiber paper and a nano porous structure of metal cobalt, the ion transmission and electron transfer speeds in the oxidation-reduction reaction process are greatly improved, the metal cobalt and nickel have synergistic effect, the catalysis of reactants is promoted together, and the sensing response performance for detecting pollutants sulfite and nitrite is high.)

1. The nano porous cobalt-nickel composite electrode capable of simultaneously detecting sulfite and nitrite comprises an electrode substrate and an electrode modification layer, and is characterized in that the electrode substrate is porous carbon fiber, and the electrode modification layer is a nano porous cobalt-nickel modification layer.

2. The composite electrode of claim 1, wherein the modified layer is prepared by modifying a nickel buffer layer on the electrode substrate, modifying a cobalt-tin alloy, and removing the alloy to obtain the nanoporous cobalt.

3. The nano-porous cobalt-nickel composite electrode capable of simultaneously detecting sulfite and nitrite as claimed in claim 1, wherein the nano-porous cobalt-nickel modification layer has a composite structure of macropores and a combination of nanopores and nano ligaments, wherein the width of the nano ligaments is 30-50nm, and the diameter of the nanopores is 50-100 nm.

4. The method for preparing the nano-porous cobalt-nickel composite electrode capable of simultaneously detecting sulfite and nitrite according to any one of claims 1 to 3, characterized by comprising the following steps:

s1, preparing a nickel buffer layer by adopting an electrodeposition method;

and S2, constructing the nano porous cobalt-nickel composite electrode by taking the nickel buffer layer as a substrate and adopting an electrodeposition-dealloying method.

5. The method for preparing a nano-porous cobalt-nickel composite electrode capable of simultaneously detecting sulfite and nitrite according to claim 4, wherein the electrodeposition method in the step S1 specifically comprises: preparing an electrodeposited nickel solution, and adjusting the pH to 4.0-4.5; placing carbon fiber paper in front of the paperAfter treatment, a double-electrode constant current mode is adopted, a titanium mesh electrode is used as an anode, carbon fiber paper is used as a cathode, the set temperature is 50-70 ℃, and the current density is 0.3-0.8A/dm²And performing electrodeposition treatment for 15-25min to obtain the nickel buffer layer.

6. The method for preparing the nano-porous cobalt-nickel composite electrode capable of simultaneously detecting sulfite and nitrite according to claim 5, wherein the electrodeposited nickel solution comprises the following components: 200.0-300.0g/L of nickel sulfate hexahydrate, 40.0-80.0g/L of nickel hydride hexahydrate, 20.0-40.0g/L of boric acid, 0.1-0.3g/L of sodium dodecyl sulfate, 0.4-0.6g/L of saccharin and 0.1-0.3g/L of 1, 4-butynediol.

7. The preparation method of the nanoporous cobalt-nickel composite electrode capable of simultaneously detecting sulfite and nitrite according to claim 5, wherein the pretreatment method of the carbon fiber paper comprises the following specific steps: placing the carbon fiber paper in concentrated HNO₃Treating at 80-120 deg.C for 60-100min, soaking in 1-3M NaOH solution for 1-2 hr, washing with deionized water, and oven drying at 50-80 deg.C.

8. The method for preparing a nano-porous cobalt-nickel composite electrode capable of simultaneously detecting sulfite and nitrite according to claim 4, wherein the electrodeposition-dealloying method in the step S2 comprises: the electrode with the nickel buffer layer prepared in the step S1 is placed in cobalt-tin alloy plating solution at 50-60 ℃ for electrodeposition, specifically, a double-electrode constant current mode is adopted, a titanium mesh electrode is used as an anode, an electrode with the nickel buffer layer is used as a cathode, and the current density is set to be 0.5-0.8A/dm²Performing electrodeposition treatment for 10-15 min; after washing with deionized water, the electrodes were placed in 5-8M KOH and 0.1M H₂O₂The mixed solution is subjected to alloy removal for 1 to 2 days to obtain the nano porous cobalt-nickel composite electrode.

9. The method for preparing the nano-porous cobalt-nickel composite electrode capable of simultaneously detecting sulfite and nitrite according to claim 8, wherein the cobalt-tin alloy plating solution comprises the following components: 17-20g/L of cobalt nitrate hexahydrate, 180g/L of stannous sulfate, 580g/L of potassium citrate, 30-50g/L of sodium citrate, 200g/L of p-toluenesulfonic acid and 3-6g/L of antimony potassium tartrate.

10. The use of the nano-porous cobalt-nickel composite electrode capable of simultaneously detecting sulfite and nitrite as claimed in any one of claims 1 to 3, wherein the nano-porous cobalt-nickel composite electrode can be used for the instant detection of sulfite and nitrite in food and water.

Technical Field

The invention belongs to the field of electrochemical sensors, and relates to a nano porous cobalt-nickel composite electrode capable of detecting sulfite and nitrite simultaneously and a preparation method thereof.

Background

The sulfite is a food additive which is widely used in the world for a long time and can be used as a food bleaching agent and a preservative. Sulfites have many practical uses, for example, calcium hydrogen sulfite is used in large quantities in the paper industry, i.e., it dissolves wood to make pulp, sodium sulfite and sodium bisulfite are used in large quantities in the dye industry, and also as a dehydrogenating agent in bleaching fabrics. In addition, sodium bisulfite is used as an inhibitor in agriculture to promote the yield increase of crops such as rice, wheat, rape, cotton and the like. Meanwhile, sulfite has been used for food cleaning and preservation, as an antioxidant and an antibacterial agent, and is widely used in the wine industry.

In 2017, 10 and 27, the list of carcinogens published by the international agency for research on cancer of the world health organization, sulfite belongs to the category 3 carcinogens. When the intake of sulfite reaches 4-6 g/day, chronic poisoning may occur, with symptoms of headache, severe diarrhea, gastrointestinal disorders, renal disorders, red blood cell and hemoglobin reduction, etc. Sulfite readily forms sulfur trioxide anion free radicals (SO) through electron oxidation after entering the body₃ ^-)，SO₃ ^-Can be reacted with O₂Rapidly react to generate superoxide anion free radical O₂ ^-. In addition, sulfites can cause damage to chromosomes and DNA. The chromosome type distortion is caused at a high concentration. Although the mechanism of these genetic effects is not clear and remains to be studied, there is a new understanding of the sulfite damage. Therefore, the boiler and process water must be monitored periodically for sulfite concentrations.

Nitrite, mainly sodium nitrite, is white to light yellow powder or granular, has slight salty taste and is easy to dissolve in water. Widely existing in human environment, is the most common nitrogen-containing compound in nature. Nitrate in human body can be reduced into nitrite, precursor substance of N-nitroso compound under the action of microbe. The appearance and taste are similar to common salt, and the common salt is widely used in industry and building industry, and the meat product is allowed to be used as a color former in a limited amount. The probability of food poisoning caused by nitrite is high, and 0.3-0.5g of nitrite can cause poisoning and 3g of nitrite can cause death. In the list of carcinogens published by international cancer research institute in 2017, day 10 and 27, world health organization, nitrite taken under conditions that lead to endogenous nitrosation is on the list of class 2A carcinogens.

Therefore, it is important to develop a sensing electrode for rapidly detecting sulfite and nitrite in water pollutants. On a conventional solid electrode, the oxidation potentials of two organic small molecules, namely sulfite and nitrite are close to each other, so that mutual distinguishing and quantitative detection are difficult. At present, various nano materials are modified on electrodes to improve the performance of sensors, such as Au, Pt, Pd, and the like. However, the nanomaterial used for modification easily falls off from the electrode and the presence of an interface between the nanomaterial and the electrode hinders the transport of electrons. The invention adopts the electrochemical in-situ modification method to prepare the nano porous metal electrode, which consists of a nano pore channel and a nano ligament, and is an ideal material for constructing the electrochemical sensor due to the larger specific surface area, excellent electron transmission performance and the nano pore channel structure beneficial to liquid mass transmission, simple preparation process and good coating binding force.

Disclosure of Invention

The invention aims to solve the technical problems that the existing nano material modified electrode is easy to fall off and has poor stability, and the nano material modified electrode is used for detecting sulfite and nitrite.

The invention aims to provide a nano porous cobalt-nickel composite electrode capable of detecting sulfite and nitrite simultaneously, which comprises an electrode substrate and an electrode modification layer, wherein the electrode substrate is porous carbon fiber, and the electrode modification layer is a nano porous cobalt-nickel modification layer and can be used for food safety detection and water environment detection.

The nano porous cobalt-nickel modified layer of the electrode is formed by modifying a nickel buffer layer on an electrode substrate, modifying cobalt-tin alloy, and removing alloy to obtain nano porous cobalt.

The nano porous cobalt-nickel composite electrode provided by the invention is a composite structure with macropores and a combination of a nanopore and a nano ligament, wherein the width of the nano ligament is 30-50nm, and the diameter of the nano pore is 50-100 nm. The structure provides more channels for electron transfer and ion transmission, greatly increases the surface active area of the electrode, and improves the sensing characteristic. Meanwhile, the three-dimensional skeleton structure of the composite electrode enhances the stability of the electrode and can avoid the material inactivation caused by the agglomeration of nano particles, so that the nano porous cobalt-nickel composite electrode can be recycled.

The invention also aims to provide a preparation method of the nano porous cobalt-nickel composite electrode capable of detecting sulfite and nitrite simultaneously.

The method specifically comprises the following steps:

and S1, preparing the nickel buffer layer by adopting an electrodeposition method.

And S2, constructing the nano porous cobalt-nickel composite electrode by taking the nickel buffer layer as a substrate and adopting an electrodeposition-dealloying method.

Further, the electrodeposition method in step S1 specifically includes: preparing an electrodeposited nickel solution, and adjusting the pH to 4.0-4.5; after the carbon fiber paper is pretreated, a double-electrode constant current mode is adopted, a titanium mesh electrode is used as an anode, carbon fiber paper is used as a cathode, the temperature is set to be 50-70 ℃, and the current density is 0.3-0.8A/dm²And performing electrodeposition treatment for 15-25min to obtain the nickel buffer layer.

Carbon fiber is a carbon material having excellent electrical conductivity. However, if the cobalt-tin alloy is electrodeposited directly on the carbon fiber, the resulting film is rough and easily peeled off from the substrate. Therefore, a nickel film is required to be pre-deposited on the carbon fiber in the electrodeposition process, and nano-porous cobalt is constructed on the carbon fiber by taking metallic nickel as a transition layer. While nickel still has very good stability under alkaline conditions. Therefore, nickel is used as a buffer layer, and the operation of removing the alloy is easier to realize the loading of the nano-porous cobalt on the carbon fiber.

Further, the electrodeposited nickel solution is composed of: 200.0-300.0g/L of nickel sulfate hexahydrate, 40.0-80.0g/L of nickel hydride hexahydrate, 20.0-40.0g/L of boric acid, 0.1-0.3g/L of sodium dodecyl sulfate, 0.4-0.6g/L of saccharin and 0.1-0.3g/L of 1, 4-butynediol.

Further, the pretreatment method of the carbon fiber paper specifically comprises the following steps: placing the carbon fiber paper in concentrated HNO₃Treating at 80-120 deg.C for 60-100min, soaking in 1-3M NaOH solution for 1-2 hr, washing with deionized water, and oven drying at 50-80 deg.C.

Further, the electrodeposition-dealloying method in step S2 specifically includes: the electrode with the nickel buffer layer prepared in the step S1 is placed in cobalt-tin alloy plating solution at 50-60 ℃ for electrodeposition, specifically, a double-electrode constant current mode is adopted, a titanium mesh electrode is used as an anode, an electrode with the nickel buffer layer is used as a cathode, and the current density is set to be 0.5-0.8A/dm²Performing electrodeposition treatment for 10-15 min; after washing with deionized water, the electrodes were placed in 5-8M KOH and 0.1M H₂O₂The mixed solution is subjected to alloy removal for 1 to 2 days to obtain the nano porous cobalt-nickel composite electrode.

Further, the cobalt-tin alloy plating solution comprises the following components: 17-20g/L of cobalt nitrate hexahydrate, 180g/L of stannous sulfate, 580g/L of potassium citrate, 30-50g/L of sodium citrate, 200g/L of p-toluenesulfonic acid and 3-6g/L of antimony potassium tartrate.

The invention also aims to provide application of the nano-porous cobalt-nickel composite electrode.

The nano porous cobalt nickel electrode prepared by the invention can be used for simultaneously detecting pollutants such as sulfite and nitrite in food safety and water environment.

Nano-porous cobalt-nickel composite electrode for detecting sodium sulfite (Na)₂SO₃) The sensitivity of (a) was 52.18. mu.g/L, and the detection limit was 0.97 mM; electrode detection of sodium nitrite (NaNO)₂) The sensitivity of (2) was 10.55. mu.g/L, and the detection limit was 2.63 mM.

The nano porous cobalt-nickel composite electrode prepared by the method can be directly connected with electrochemical detection equipment, realizes the on-site real-time detection of sulfite and nitrite, can specifically detect sulfite and nitrite in food and water, and does not need complex treatment procedures during laboratory examination of samples. Particularly for portable rapid detection sensors.

Scanning and observing the nano porous cobalt-nickel composite electrode prepared by the invention by adopting an SEM electron microscope.

FIG. 1 is an SEM topography of a nanoporous cobalt nickel composite electrode obtained in the preparation process of example 1. Wherein FIG. 1(a) is an SEM image of an electrode having a nickel modification layer; fig. 1(b) is an SEM image of the nanoporous cobalt nickel composite electrode. As can be seen from fig. 1(a), the nickel thin film layer is closely and completely distributed on the carbon fiber paper substrate. And then carrying out electrodeposition dealloying treatment to obtain the nano-porous cobalt-nickel composite electrode shown in the figure 1 (b). The electrode consists of bicontinuous nano structures and mutually communicated ligaments, and the continuous network structure is favorable for full contact between the electrode and electrolyte and improves the oxidation-reduction reaction speed of the electrode.

The nano porous cobalt-nickel composite electrode prepared by the method is subjected to sulfite and nitrite response performance test by adopting methods such as cyclic voltammetry scanning, timing current detection and the like.

FIG. 2 shows that the nano-porous cobalt-nickel composite electrode prepared by the invention tests Na with different concentrations (1-5mM)₂SO₃(a) And NaNO₂(b) Cyclic voltammogram of (a). It can be seen from the graph that the characteristic peak current gradually increases as the concentration of the two species increases, and the portion of the dotted frame in the graph is the oxidation peak of the electrode. The nano porous cobalt nickel composite electrode prepared by the method can realize the independent detection of sodium sulfite and sodium nitrite.

FIG. 3 shows that the nano-porous cobalt-nickel composite electrode prepared by the invention is applied to Na with the concentration of 3mM and 5mM₂SO₃And NaNO₂Cyclic voltammogram in PBS solution (c). As can be seen in the figure, in Na₂SO₃And NaNO₂The characteristic current peaks of the mixed solution (2) were detected, and the oxidation peaks of the electrodes are shown by the dotted line frame. The nano porous cobalt nickel composite electrode prepared by the method can realize the simultaneous detection of sodium sulfite and sodium nitrite.

FIG. 4 shows that Na is continuously dropped into 0.1M PBS buffer solution by the nano-porous cobalt-nickel composite electrode prepared by the invention₂SO₃Ampere-timing test pattern. It can be seen from the figure that Na is accompanied by₂SO₃Concentration ofGradually increasing in response to the electrode; inset is electrode at low concentration of Na₂SO₃The response curve in (1) shows that Na is added at 10. mu.M₂SO₃Later, the response current of the electrode shows an ascending step, which shows that the nano porous cobalt-nickel composite electrode prepared by the invention can react on Na under lower concentration₂SO₃An electrochemical response is generated, i.e. the electrode can detect a low concentration of sodium sulfite.

FIG. 5 shows that the nano-porous cobalt-nickel composite electrode prepared by the invention is Na with the concentration of 3mM₂SO₃The response curve (a) in PBS solution (pH 6.5) as a function of scan speed, and the linear fit curve (b) of peak current to scan speed. The dotted line frame portion in the figure indicates the oxidation peak of the electrode. As can be seen from the figure, Na increases with the scanning speed₂SO₃The peak current of the electrode is gradually enhanced, and the fitted curve of the electrode shows good linear relation, which shows that the nano porous cobalt-nickel composite electrode is applied to Na₂SO₃The electrocatalytic oxidation process is a diffusion-controlled process, the conduction of electrons at the liquid-contact interface is very rapid, and Na₂SO₃The diffusion of molecules from the bulk of the solution to the surface of the electrode is a speed-determining step, that is, concentration polarization is an important factor influencing the sensitivity of the electrode, and the nano-porous cobalt-nickel composite electrode prepared by the invention has excellent response performance to sodium sulfite.

The nano porous cobalt nickel composite electrode prepared by the invention has higher sensitivity and lower detection limit on the detection of water pollutants sodium sulfite and sodium nitrite, and can realize Na₂SO₃And NaNO₂Simultaneous detection and individual point-of-care detection.

The invention has the beneficial effects that:

(1) the composite electrode constructed by the nano-porous cobalt has larger specific surface area, excellent electron transmission performance and a structure combining macropores and nanopores which are beneficial to liquid mass transmission. The metal cobalt and nickel can generate synergistic action and jointly promote the catalysis of reactants. Meanwhile, the electrode material is cheap and has excellent sensitive response characteristics to the detected object.

(2) The electrode preparation process is simple, the method for modifying the nano porous metal in situ can effectively avoid agglomeration and inactivation of nano particles, the cost is low, and the method is suitable for industrial application.

(3) The electrode provided by the invention can realize simultaneous detection of sulfite and nitrite pollutants in food safety and water environment, and promotes popularization and application of a sensor for rapidly detecting sulfite and nitrite.

Drawings

The invention is further illustrated by means of the attached drawings, but the embodiments in the drawings do not constitute any limitation to the invention, and for a person skilled in the art, other drawings can be obtained on the basis of the following drawings without inventive effort.

Fig. 1 is an SEM image (a) of an electrode with a nickel buffer layer and a nano-porous cobalt-nickel composite electrode prepared according to the present invention (b);

FIG. 2 shows that the nano-porous cobalt-nickel composite electrode prepared by the invention tests Na with different concentrations (1-5mM)₂SO₃(a) And NaNO₂(b) Cyclic voltammogram of (a);

FIG. 3 shows that the nano-porous cobalt-nickel composite electrode pair prepared by the invention is applied to Na with the concentration of 3mM and 5mM₂SO₃And NaNO₂Cyclic voltammogram in PBS solution of (a);

FIG. 4 shows that Na is continuously dripped into 0.1M PBS by the nano-porous cobalt-nickel composite electrode prepared by the invention₂SO₃An ampere-hour test chart of (a);

FIG. 5 shows that the nano-porous cobalt-nickel composite electrode prepared by the invention is at 3mM Na₂SO₃The change curve (a) with scan speed in PBS solution (pH 6.5), and the linear fit curve (b) of peak current to scan speed.

Detailed Description

In order that the objects, aspects and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the following detailed description and the accompanying drawings.