CN115343338A

CN115343338A - FeOOH/CC and nitrite electrochemical sensor and application thereof

Info

Publication number: CN115343338A
Application number: CN202210573236.9A
Authority: CN
Inventors: 苏小东; 徐春丽; 贾振福; 张燕; 刘恩余; 黄瑶瑶; 高渝萌; 张珊
Original assignee: Chongqing University of Science and Technology
Current assignee: Chongqing University of Science and Technology
Priority date: 2022-05-24
Filing date: 2022-05-24
Publication date: 2022-11-15

Abstract

The invention discloses FeOOH/CC, and a preparation method thereof comprises the following steps: placing the carbon cloth substrate in H ₂ SO ₄ Carrying out electrochemical oxidation treatment in the aqueous solution to obtain pretreated carbon cloth; and then depositing FeOOH material on the pretreated carbon cloth to obtain the FeOOH/CC electrode. The invention also discloses a nitrite electrochemical sensor containing the FeOOH/CC electrode and application thereof. The FeOOH/CC electrode provided by the invention adopts a potentiostatic method electrochemical deposition method which is simple to operate and short in time consumption to directly deposit a fluffy ball-shaped FeOOH material on the CC substrate, thereby constructing a self-supporting adhesive-free FeOOH/CC nitrite electrochemical sensor; the electrochemical sensor prepared from the FeOOH/CC self-supporting electrode has the advantages of high sensitivity, wide linear range, excellent detection limit, good stability and reproducibility and the like in a system containing nitrite.

Description

FeOOH/CC and nitrite electrochemical sensor and application thereof

Technical Field

The invention belongs to the technical field of electrical materials, and particularly relates to an FeOOH/CC and nitrite electrochemical sensor and application thereof.

Background

Due to the development of industry and agriculture and the pollution of domestic wastewater, the content of nitrite in natural water is increased, excessive nitrite can cause the overgrowth of water plants, dissolved oxygen in water is reduced, animals in water die due to insufficient oxygen or nitrite poisoning, and finally the ecological system of the water is damaged. Therefore, the method has profound significance for maintaining the balance of the ecological system and protecting the environment by regularly, quantitatively, quickly and accurately detecting the nitrite content in the water body.

At present, methods for measuring nitrous acid include an optical analysis method, a chromatography method and an electrochemical detection method, wherein the electrochemical detection method has the characteristics of high efficiency, high speed, low cost, high portability and the like, so that the method is rapidly developed and becomes a research hotspot. The wide application of platinum (Pt), gold (Au), copper (Cu), silver (Ag), glassy Carbon (GCE) and the like in nitrite electrochemical sensors is limited due to the low electron transfer efficiency, poor long-term stability and the like of the electrode materials. The carbon material has the advantages of unique chemical/physical stability, strong heat resistance and corrosion resistance, wide electrochemical window, large specific surface area, high conductivity and the like, and is the most widely researched material in the nitrite electrochemical sensor. Liu et al constructed an electrochemical sensor based on Graphene Oxide (GO) nanosheets by improving the conductivity of the electrode by covalently grafting (4-ferroceneyne) aniline on the surface of GO, thereby improving the sensitivity and selectivity of the sensor, and being used for detecting nitrite in a tap water sample. Zhu et al can obtain oxidized carbon fiber paper electrode materials directly used in electrochemical nitrite sensors by treating carbon fiber paper through a simple air annealing process.

As a commercialized carbon-based material, carbon fiber cloth (CC) has recently attracted attention as a base material for supporting electrocatalysis, fuel cells, supercapacitors and electrochemical analysis due to its electrical conductivity, 3D macropore, flexibility and stable carbon skeleton structure. The catalyst material directly grows on the CC substrate, so that the reduction of the conductivity caused by the use of an adhesive is avoided, more catalytic active sites are exposed, and the development of the catalyst material in electrochemical sensing is further promoted. ZHE et al, by using a concentrated acid heating reflux process, heat-treat CC in 120 deg.C concentrated acid for 2h to enhance the hydrophilicity of CC. Then FeSe nano particles are loaded on CC through an in-situ synthesis method, and the self-supporting electrode of FeSe NR/CC is prepared and used for detecting the nitrite content in the pickle. However, the method adopts a concentrated acid heating reflux process to carry out hydrophilic treatment on the CC, so that the pollution is large, the process is complicated and the time consumption is long, the CC surface cannot be fully oxidized, and the adhesion and growth of an active material are hindered.

Disclosure of Invention

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. To this end, the primary object of the present invention is to provide a FeOOH/CC for use in the manufacture of an electrochemical nitrite sensor by depositing FeOOH material having a textured ball shape on a CC substrate to create a self-supporting binderless FeOOH/CC nitrite electrochemical sensor.

The purpose of the invention is realized by the following technical scheme:

the preparation method of the FeOOH/CC comprises the following steps: placing the carbon cloth substrate in H ₂ SO ₄ Carrying out electrochemical oxidation treatment in the aqueous solution to obtain pretreated carbon cloth; and then depositing FeOOH material on the pretreated carbon cloth to obtain the FeOOH/CC electrode.

In certain embodiments, the electrochemical oxidation treatment is specifically: taking the carbon cloth substrate after washing and drying as a working electrode, taking a saturated calomel electrode as a reference electrode, taking a platinum sheet electrode as an auxiliary electrode, and performing electrochemical reaction on the carbon cloth substrate H ₂ SO ₄ And carrying out electrochemical oxidation reaction in the aqueous solution, washing and drying after the reaction to obtain the pretreated carbon cloth.

Further, said H ₂ SO ₄ The molar concentration of the aqueous solution is 0.05-0.15 mol/L, the voltage of the electrochemical oxidation reaction is 1.0-3.0V, and the treatment time is 10-60min.

In certain embodiments, wherein the wash drying is: and (3) sequentially placing the carbon cloth substrate in absolute ethyl alcohol, distilled water, acetone and distilled water for washing, and placing the washed carbon cloth substrate in a vacuum drying oven for drying for later use.

Further: immersing the carbon cloth substrate in absolute ethyl alcohol for ultrasonic cleaning for 0.5-10min, taking out the carbon cloth, basically washing the carbon cloth by distilled water, then putting the carbon cloth into acetone for continuous ultrasonic cleaning for 0.5-10min, finally washing the carbon cloth by distilled water for a plurality of times to remove insoluble grease, dust and other impurities on the surface of the carbon cloth substrate, and then putting the carbon cloth substrate which is washed clean into a vacuum drying oven for drying at 60 ℃ to be used as a subsequent electrode for standby.

In certain specific embodiments, the depositing is specifically: taking a mixed solution of ferrous sulfate and sodium nitrate as an electrolyte, taking the pretreated carbon cloth as a working electrode, taking a platinum sheet as an auxiliary electrode and taking an Ag/AgCl electrode as a reference electrode to perform constant potential electrodeposition, washing and drying to obtain the FeOOH/CC electrode.

Further, the molar concentration of the ferrous sulfate is 0.05-0.3mol/L, the molar concentration of the sodium nitrate is 0.05-0.3mol/L, and the process parameters of the constant potential electrodeposition are as follows: the working voltage is-0.8 to-1.2V, and the deposition time is 5 to 25min.

Further, the water washing is carried out by adopting distilled water for washing for a plurality of times, and the drying is carried out by putting into a vacuum drying oven for drying at 60 ℃.

The principle of depositing the FeOOH material on the pretreated carbon cloth to prepare the FeOOH/CC material is as follows:

Fe ²⁺ -e ^- →Fe ³⁺

Fe ³⁺ +3OH ^- →FeOOH+H ₂ O

in some casesIn the specific examples, to prevent Fe ²⁺ Oxidizing, and removing oxygen from the distilled water by using a nitrogen drum for 20-40min.

The invention also aims to provide a nitrite electrochemical sensor containing the FeOOH/CC.

Specifically, the electrochemical oxidation mechanism of nitrite on FeOOH/CC is that firstly,

undergoes a complexation reaction with FeOOH/CC to form

Then, at

Formation of nitrogen dioxide (NO) after loss of one electron of the complex ₂ ). Next, by NO ₂ Is generated by a disproportionation reaction

And

finally, the process is carried out in a batch,

is obtained by

The only possible product of electrocatalytic oxidation of (a), the reaction equation of which is as follows:

further, a nitrite detection device in the water body comprising the nitrite electrochemical sensor is also provided. In particular, a nitrite detection device in a body of water containing a nitrite electrochemical sensor may be used to monitor water pollution conditions.

The invention aims to further provide a method for detecting the content of nitrite in the water body, which is to use any previous nitrite electrochemical sensor or any previous nitrite detection device to carry out i-t detection on the water body and measure the content of nitrite in the water body according to a current value obtained by detection.

Further, the detection potential of the detection method is 0.70-0.85V, and preferably, the detection potential is set to 0.80V for maximum current response, and for relatively sensitive and stable signals and relatively small noise values.

In some specific embodiments, the FeOOH/CC electrode is used as a working electrode, a platinum wire electrode is used as an auxiliary electrode, and a saturated calomel electrode is used as a reference electrode to form a nitrite electrochemical sensor for detection.

Compared with the prior art, the invention has at least the following advantages:

the FeOOH/CC electrode provided by the invention directly deposits the fluffy ball-shaped FeOOH material on the CC substrate by adopting a potentiostatic electrochemical deposition method which is simple to operate and short in time consumption, thereby constructing the self-supporting adhesive-free FeOOH/CC nitrite electrochemical sensor. The electrochemical sensor prepared from the FeOOH/CC self-supporting electrode has the advantages of high sensitivity, wide linear range, excellent detection limit, good stability and reproducibility and the like in a system containing nitrite.

Drawings

In order to more clearly illustrate the embodiments of the present invention, reference will now be made briefly to the embodiments or to the accompanying drawings that are needed in the description of the prior art.

FIG. 1 is an XRD characterization analysis diagram of an FeOOH/CC electrode provided by the invention;

FIG. 2 is an SEM image of a FeOOH/CC electrode provided by the present invention;

FIG. 3 is an XPS characterization analysis chart of the FeOOH/CC electrode provided by the invention;

FIG. 4 is a CV diagram of the FeOOH/CC electrode and the bare CC electrode provided by the present invention (a), and a histogram of the peak current density and the peak potential of the FeOOH/CC electrode and the bare CC electrode (b);

FIG. 5 is a CV diagram of 0-10 mM nitrite concentration at a scanning rate of 50mV/s for an FeOOH/CC electrode provided in the present invention (a), and a linear relationship diagram of peak current density and nitrite concentration for the FeOOH/CC electrode (b);

FIG. 6 is an i-t curve (a) of FeOOH/CC electrode added with nitrite of different concentrations under 0.80V (vs. SCE) and a linear relationship (b) of current density and nitrite concentration of the FeOOH/CC electrode;

FIG. 7 is an i-t curve of the FeOOH/CC electrode provided by the present invention when different interferents are added under 0.80V (vs. SCE);

FIG. 8 is a CV diagram (a) of FeOOH/CC electrode provided by the present invention in 1 to 30 days, and a comparison histogram of peak current density thereof;

FIG. 9 is a CV diagram (a) of 6 FeOOH/CC electrodes provided by the present invention, and a comparison histogram of peak current density thereof.

Detailed Description

The present invention will be further described with reference to the following drawings and examples, which are illustrative only and not intended to be limiting, and the scope of the present invention is not limited thereby. The examples, in which specific conditions are not specified, were carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

In the following examples, the carbon cloth used was purchased from carbon technologies, inc.

EXAMPLE 1 preparation of FeOOH/CC electrode

Embodiment mode 1

1) Immersing the carbon cloth substrate in absolute ethyl alcohol for ultrasonic cleaning for 1min, taking out the carbon cloth substrate, washing the carbon cloth substrate with distilled water, putting the carbon cloth substrate into acetone for continuous ultrasonic cleaning for 1min, and finally washing the carbon cloth substrate with distilled water for a plurality of times to remove insoluble grease, dust and other impurities on the surface of the carbon cloth substrate. And (3) putting the cleaned carbon cloth substrate into a vacuum drying oven to be dried at 60 ℃ to be used as a subsequent electrode for later use.

2) Washing the dried CC (1X 1 cm) ² ) As a working electrode, a Saturated Calomel Electrode (SCE) is used as a reference electrode, a platinum sheet electrode is used as an auxiliary electrode, and the concentration of H is 0.05mol/L ₂ SO ₄ Carrying out electrochemical oxidation treatment in the solution. Treating for a certain time (0 min, 10min, 30min, 60 min) at a voltage of 1.0V by adopting a constant potential method, taking out, fully washing the treated carbon cloth substrate by using distilled water, and drying the cleaned carbon cloth substrate in a vacuum drying oven at 60 ℃ to obtain the pretreated carbon cloth serving as a subsequent electrode for later use.

3) And depositing FeOOH material on the pretreated carbon cloth substrate by adopting a constant potential electrochemical deposition method. The electrodeposition process was carried out in a conventional three-electrode reaction system, pretreating the carbon cloth (1X 1 cm) ² ) Is a working electrode, a platinum sheet is an auxiliary electrode, and Ag/AgCl is a reference electrode. The electrolyte consists of 0.05mol/L ferrous sulfate and 0.05mol/L sodium nitrate, and distilled water for preparing the electrolyte is subjected to deoxygenation by nitrogen bubbling for 40min to prevent Fe ²⁺ And (4) oxidizing. Electrodepositing for 25min under the constant voltage of-0.8V (relative to Ag/AgCl), then washing for a plurality of times by using distilled water, and finally drying in a vacuum drying oven at 60 ℃ to obtain the FeOOH/CC electrode.

Embodiment mode 2

1) Immersing the carbon cloth substrate in absolute ethyl alcohol for ultrasonic cleaning for 2min, taking out the carbon cloth substrate, washing the carbon cloth substrate with distilled water, putting the carbon cloth substrate into acetone for continuous ultrasonic cleaning for 2min, and finally washing the carbon cloth substrate with distilled water for a plurality of times to remove insoluble grease, dust and other impurities on the surface of the carbon cloth substrate. And (3) putting the cleaned carbon cloth substrate into a vacuum drying oven for drying at 60 ℃ to serve as a subsequent electrode for later use.

2) Washing the dried CC (1X 1 cm) ² ) As a working electrode, a Saturated Calomel Electrode (SCE) is used as a reference electrode, a platinum sheet electrode is used as an auxiliary electrode, and the concentration of H is 0.1mol/L ₂ SO ₄ Carrying out electrochemical oxidation treatment in the solution. Treating for a certain time (0 min, 10min, 30min and 60 min) at 2.0V by adopting a constant potential method, taking out, fully washing the treated carbon cloth substrate by using distilled water, and drying the washed carbon cloth substrate in a vacuum drying box at 60 ℃ to obtain the pretreated carbon cloth serving as a subsequent electrode for later use.

3) And depositing FeOOH material on the pretreated carbon cloth substrate by adopting a constant potential electrochemical deposition method. The electrodeposition process is carried out in a conventional three-electrode reaction system, and the carbon cloth (1X 1 cm) is pretreated ² ) Is a working electrode, a platinum sheet is an auxiliary electrode, and Ag/AgCl is a reference electrode. The electrolyte consists of 0.1mol/L ferrous sulfate and 0.1mol/L sodium nitrate, wherein distilled water for preparing the electrolyte is subjected to deoxygenation by bubbling nitrogen for 20-40min to prevent Fe ²⁺ And (4) oxidizing. Electrodepositing for 10min under the constant voltage of-1.0V (relative to Ag/AgCl), then washing for a plurality of times by using distilled water, and finally drying in a vacuum drying oven at 60 ℃ to obtain the FeOOH/CC electrode.

Embodiment 3

1) Immersing the carbon cloth substrate in absolute ethyl alcohol for ultrasonic cleaning for 10min, taking out the carbon cloth substrate, washing the carbon cloth substrate with distilled water, putting the carbon cloth substrate into acetone for continuous ultrasonic cleaning for 5min, and finally washing the carbon cloth substrate with distilled water for a plurality of times to remove insoluble grease, dust and other impurities on the surface of the carbon cloth substrate. And (3) putting the cleaned carbon cloth substrate into a vacuum drying oven for drying at 60 ℃ to serve as a subsequent electrode for later use.

2) Washing the dried CC (1X 1 cm) ² ) As a working electrode, a Saturated Calomel Electrode (SCE) is used as a reference electrode, a platinum sheet electrode is used as an auxiliary electrode, and the concentration of H is controlled at 0.15mol/L ₂ SO ₄ Carrying out electrochemical oxidation treatment in the solution. Treating at 3.0V for 0min, 10min, 30min, 60min by constant potential method, taking out, washing with distilled water, and standing at 60 deg.CAnd drying in a vacuum drying box to obtain the pretreated carbon cloth serving as a subsequent electrode for later use.

3) And depositing FeOOH material on the pretreated carbon cloth substrate by adopting a constant potential electrochemical deposition method. The electrodeposition process is carried out in a conventional three-electrode reaction system, and the carbon cloth (1X 1 cm) is pretreated ² ) Is a working electrode, a platinum sheet is an auxiliary electrode, and Ag/AgCl is a reference electrode. The electrolyte consists of 0.3mol/L ferrous sulfate and 0.3mol/L sodium nitrate, wherein distilled water for preparing the electrolyte is used for deoxidizing by bubbling nitrogen for 20min so as to prevent Fe ²⁺ And (4) oxidizing. And (3) performing electrodeposition for 5min under the constant voltage of-1.2V (relative to Ag/AgCl), washing with distilled water for several times, and finally drying in a vacuum drying oven at 60 ℃ to obtain the FeOOH/CC electrode.

[ example 2 ] Performance detection

Example 2 taking the FeOOH/CC electrode prepared in example mode 2 of example 1 as an example, a performance test was performed as follows:

1. material characterization

(1) Measuring the crystal structure by using an X-ray diffractometer (XRD) at a scanning speed of 5 degrees/min within a scanning range of 10 degrees to 80 degrees; as a result, as shown in FIG. 1, the broad diffraction peaks at 25.2 ℃ and 43.03 ℃ of the Carbon Cloth (CC) corresponded to the diffraction peaks at the (002) and (101) planes of graphitic carbon. Characteristic diffraction peaks corresponding to crystal planes of FeOOH (PDF # 73-2326) (020), (021), (130), (150) (151) and (200) appear at 14.1 degrees, 27.1 degrees, 36.4 degrees, 46.9 degrees, 52.8 degrees and 60.5 degrees, which indicates that the FeOOH/CC electrode is successfully prepared.

(2) Using an SU-8100 field emission scanning electron microscope to observe and analyze the surface structure and the morphology state of the FeOOH/CC electrode material under the acceleration voltage of 10 kV; as shown in FIG. 2, it is clear from FIG. 2 that FeOOH/CC electrode material has a regular rod-like network structure and FeOOH having different shapes and sizes grows on the fibers of CC as shown in FIGS. 2 (a) and (b). Further magnification, as shown in fig. 2 (c) (d), feOOH is similar in shape to dandelion seeds and appears as pompon, with individual pompon growing in rows on CC. The results of the combined XRD tests show that FeOOH/CC has been successfully prepared. Compare to untreated CC (FIG. 2 (a) ₁ ) Growth of FeOOH expands the electrodeThe specific surface area of the electrode increases the reactive active sites of the electrode, thereby improving the electrocatalytic oxidation capability of FeOOH/CC to nitrite.

(3) An ESCALAB 250Xi type X-ray photoelectron spectrometer is used, and Al is used as an excitation source to analyze chemical composition and element valence state. As shown in FIG. 3 (a), the XPS survey shows characteristic peaks of three elements, fe, C and O, indicating that the prepared FeOOH/CC electrode material contains the three elements. In addition, the valence state and functional group of Fe and O are further analyzed. First, as shown in FIG. 3 (b), for the Fe2p orbital, two characteristic peaks appearing at the binding energies of 711.7eV and 725.3eV, respectively, correspond to Fe2p of the Fe element, respectively _3/2 And Fe2p _1/2 And two wider satellite peaks. An XPS spectrum of O1 s of FeOOH is shown in FIG. 3 (c). At a band energy of 531.5eV, a product peak of O1 s is observed, further corresponding to three different types of O element, which are oxygen in the metal oxide formed by metal bonding, hydroxyl oxygen, and oxygen in the adsorbed water, respectively. The characterization and analysis results of the SEM and the XRD are combined, so that the FeOOH/CC electrode is successfully prepared.

2. Electrochemical performance test of nitrite electrochemical sensor containing FeOOH/CC

(1) Electrocatalytic activity on nitrite

The electrocatalytic activity of FeOOH/CC electrode on nitrite is studied in the voltage range of 0.6-1.2V by CV method. The results are shown in FIG. 4, and it can be seen from FIGS. 4 (a) (b) that there is no significant electrochemical signal for the CC electrode system in nitrite-free solution. When 1.0mM nitrite is present in the solution, the CC electrode has an oxidation peak current density of 0.960mA cm at 0.865V (vs. SCE) ^-2 For FeOOH/CC electrodes, the system has no obvious electrochemical response when no nitrite is contained, while in the solution containing 1.0mM nitrite, the oxidation peak current density of the FeOOH/CC electrode at 0.803V (vs. SCE) is larger and reaches 1.299mA cm ^-2 . Compared with a naked CC electrode, the FeOOH/CC electrode has lower oxidation peak potential and higher oxidation current density when detecting nitrite. SEM results of the combined FeOOH/CC electrode revealed that the velvetThe spherical FeOOH grows on the CC, so that the FeOOH/CC electrode has larger active specific surface area and more catalytic active sites, and the diffusion distance from an electrolyte substance to the surface active sites is shortened, thereby improving the transfer capacity of electrons. Therefore, the FeOOH/CC electrode system has higher electrocatalytic activity and lower oxidation potential on nitrite. In addition, there was NO reduction peak in the CV diagrams for both the CC electrode and FeOOH/CC electrode systems, indicating that the electrocatalytic oxidation of nitrite is irreversible, which is not reversible with NO ₂ ^- To NO ₃ ^- One two-electron oxidation process mechanism of conversion is consistent:

adopting CV method, the scanning speed is 50mV s in the range of 0.6-1.1V ^-1 Under the conditions of (1), the electrochemical response of the FeOOH/CC electrode in 0.1M PBS solution (pH = 7.00) containing different concentrations of nitrite (0-10 mM) was determined.

As can be seen from fig. 5 (a), as the nitrite concentration increases, the oxidation peak potential gradually shifts to the positive direction, and the oxidation peak current (Ip) also gradually increases. FIG. 5 (b) shows that the oxidation peak current of the system has a good linear relationship with nitrite concentration in the range of 0-10 mM, and the calibration formula is: ip (mA cm) ^-2 ) =0.751+0.811C (mM), correlation coefficient R ² 0.9994, indicating that the FeOOH/CC electrode has a significant current response to nitrite over a wide range of nitrite concentrations.

(2) Linear range, detection limit and sensitivity

In order to obtain the performance values of the constructed FeOOH/CC nitrite electrochemical sensor, such as detection linear range, sensitivity, detection Limit (LOD) and the like, for detecting nitrite, different amounts of nitrite are added to 0.1M PBS solution (pH = 7.00) at a detection voltage of 0.85V (vs. SCE) by using the i-t method, and the current increases in a step manner along with the increase of the concentration in response to the increase of the concentration, and the result is shown in FIG. 6 (a). FIG. 6 (b) shows the current density in the nitrite concentration range of 0.1-16000. Mu.MThe degree and the nitrite concentration have a good linear relation, and the linear regression equation is as follows: ip (mA cm) ^-2 ) =26.084+0.2564C (mM), correlation coefficient R ² Is 0.9992. In the range of low nitrite concentration of 0.1-1200 mu M, the oxidation current response and the nitrite concentration have better linear relation, and the linear regression equation is as follows: ip (mA cm) ^-2 ) =65.949+0.3061C (mM), correlation coefficient R ² Is 0.9997. The sensitivity of the FeOOH/CC nitrite electrochemical sensor is 306.1 mu A mM according to calculation ^-1 cm ^-2 LOD (S/N = 3) was 0.07 μ M.

(3) Anti-interference performance

In the actual detection process, the detection background of the detected sample is complex, and other substances are usually contained, which may affect the determination result of the nitrite. In the experiment, substances commonly found in the background of a detected water sample, such as NaNO, are added into a 0.1M PBS solution (pH = 7.00) through an i-t method under a detection voltage of 0.85V to serve as interferences ₃ 、Al(NO ₃ ) ₃ 、Zn(NO ₃ ) ₂ 、C ₆ H ₁₂ O ₆ 、Na ₂ CO ₃ 、Fe(NO ₃ ) ₃ 、MgSO ₄ 、CO(NH ₂ ) ₂ 、 CH ₃ COONa、CaCl ₂ And KCl. As shown in FIG. 7, after adding 10. Mu.M, a significant response current appeared, and then 1mM of the interfering substance was added at intervals of 50s in sequence, the FeOOH/CC electrochemical sensor did not have any response current appeared, and when 10. Mu.M of nitrite was added again to the solution, a response current signal appeared again in the FeOOH/CC electrochemical sensor. The result shows that the constructed FeOOH/CC nitrous acid electrochemical sensor has good anti-interference capability and can detect actual samples.

(4) Reproducibility and stability

The stability of the FeOOH/CC nitrite electrochemical sensor provided by the application adopts a CV method, and CV graphs and oxidation peak current values on FeOOH/CC electrodes of 1, 6, 12, 18, 24 and 30 days are respectively measured in a 0.1M PBS (pH = 7.00) solution in which 1.0mM nitrite exists. As shown in fig. 8 (a) (b), the oxidation peak current value and the oxidation peak potential did not change significantly over a one-month period, and the Relative Standard Deviation (RSD) of the measurement results for different standing times was 1.68%, indicating that the FeOOH/CC nitrite electrochemical sensor has good long-term stability.

The reproducibility of the constructed FeOOH/CC nitrite electrochemical sensor was evaluated, 6 FeOOH/CC electrodes were prepared under the same conditions, and CV graphs and oxidation peak current values on the 6 FeOOH/CC electrodes were determined in 0.1M PBS (pH = 7.00) solution in the presence of 1.0 nitrite by CV method. As can be seen from the results in FIG. 9 (a) (b), the RSD of the prepared 6-counts FeOOH/CC nitrite electrochemical sensor for nitrite determination is 2.54%, which indicates that the FeOOH/CC nitrite electrochemical sensor has good reproducibility.

The FeOOH/CC nitrite electrochemical sensor prepared by the method is used for testing the nitrite content in water, and specifically comprises the following steps: filtering a newly-taken Linghu water sample by using a 0.45 mu M filter membrane to remove suspended matters and particle impurities in a water body, and then determining nitrite in Linghu water by ion chromatography according to the test requirement of GB/T39305-2020 on nitrite in natural lake water, wherein the determination result is 0.35 mu M. Respectively adding 0.5, 1 and 3 mu M of nitrite into the Ling lake water sample to carry out standard addition recovery experiments, wherein the standard addition recovery experiments are specifically shown in Table 1;

TABLE 1 Standard recovery test results of nitrite in natural lake water

The result of the standard addition recovery experiment in Table 1 shows that the nitrite standard addition recovery rate of the FeOOH/CC nitrite electrochemical sensor in Ling lake water is between 96.81 and 106.94 percent, and the FeOOH/CC nitrite electrochemical sensor prepared by the experiment has good accuracy in detection of nitrite ions in an actual sample, which indicates that the sensor can be applied to detection of nitrite in the actual sample.

In conclusion, the FeOOH/CC electrode provided by the invention directly deposits a fluffy ball-shaped FeOOH material on the CC which is not subjected to any hydrophilic treatment by a constant potential electrochemical method, so that the conductivity of the CC substrate and the good contact between active FeOOH/CC nanosheets are ensured, and the rapid charge transmission in the electrochemical reaction process is promoted; effectively avoids the charge transfer resistance increase and active site loss caused by using substances such as adhesive, conductive additive and the like. The conductive CC substrate is beneficial to improving the conductivity and charge transfer of the electrode, thereby effectively overcoming the defect of poor conductivity of FeOOH; and secondly, the pompon structure of the FeOOH/CC electrode provides rich catalytic active sites and high electrochemical activity specific surface area, and shortens the diffusion distance from the electrolyte substance to the surface active sites, thereby accelerating the electrochemical dynamics and improving the analysis performance of nitrite.

The prepared FeOOH/CC electrode has excellent sensing performance on nitrite. The sensitivity of the FeOOH/CC nitrite electrochemical sensor is 256.4 muA mM within the nitrite concentration range of 0.1-16000 muM ^- ¹ cm ^-2 Coefficient of correlation R ² Is 0.9992. While in the low concentration range of 0.1-1200 MuM nitrite, the sensitivity of the FeOOH/CC nitrite electrochemical sensor is 306.1 MuA mM ^-1 cm ^-2 LOD was 0.07. Mu.M. In the detection of an actual sample (campus lake water-Ling lake water), the standard recovery rate of the FeOOH/CC nitrite electrochemical sensor is between 96.81 and 106.94 percent, and the electrochemical sensor has good repeatability and long-term stability.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the embodiments of the present invention, and they should be construed as being covered by the appended claims and their equivalents.

Claims

FeOOH/CC, a feature thereofCharacterized in that the preparation method comprises the following steps: placing the carbon cloth substrate in H ₂ SO ₄ Carrying out electrochemical oxidation treatment in the aqueous solution to obtain pretreated carbon cloth; and then depositing FeOOH material on the pretreated carbon cloth to obtain the FeOOH/CC electrode.
2. An FeOOH/CC according to claim 1, wherein said electrochemical oxidation treatment is specifically: taking the carbon cloth substrate after washing and drying as a working electrode, taking a saturated calomel electrode as a reference electrode, taking a platinum sheet electrode as an auxiliary electrode, and performing electrochemical reaction on the carbon cloth substrate H ₂ SO ₄ And carrying out electrochemical oxidation reaction in the aqueous solution, washing and drying after the reaction to obtain the pretreated carbon cloth.
3. FeOOH/CC according to claim 1, wherein said deposition is in particular: taking a mixed solution of ferrous sulfate and sodium nitrate as an electrolyte, taking the pretreated carbon cloth as a working electrode, taking a platinum sheet as an auxiliary electrode and taking Ag/AgCl as a reference electrode, and carrying out constant potential electrodeposition, washing and drying to obtain the FeOOH/CC electrode.
4. FeOOH/CC according to claim 4, characterized in that the H is ₂ SO ₄ The molar concentration of the aqueous solution is 0.05-0.15 mol/L, the voltage of the electrochemical oxidation reaction is 1.0-3.0V, and the treatment time is 10-60min.
5. A FeOOH/CC according to claim 4, wherein the ferrous sulfate has a molarity of 0.05-0.3mol/L, the sodium nitrate has a molarity of 0.05-0.3mol/L, and the potentiostatic electrodeposition process parameters are: the working voltage is-0.8 to-1.2V, and the deposition time is 5 to 25min.
6. FeOOH/CC according to claim 2, characterized in that the washing and drying are: and (3) sequentially placing the carbon cloth substrate in absolute ethyl alcohol, distilled water, acetone and distilled water for washing, and placing the washed carbon cloth substrate in a vacuum drying oven for drying for later use.
7. Nitrite electrochemical sensor comprising FeOOH/CC according to any of claims 1 to 6.
8. A nitrite detection apparatus in a body of water comprising the nitrite electrochemical sensor of claim 7.
9. A method for detecting the content of nitrite in water body, characterized in that the nitrite electrochemical sensor as claimed in claim 7 or the nitrite detection device as claimed in claim 8 is used for i-t detection of water body, and the nitrite content in water body is measured according to the detected current value.
10. The detection method according to claim 9, wherein the detection potential of the detection method is 0.70 to 0.85V.