Preparation method and detection method of a self-powered photoelectrochemical hydrogen peroxide sensor

Abstract

The present invention relates to the field of sensor technology, and specifically discloses a preparation method and a detection method of a self-powered photoelectrochemical hydrogen peroxide sensor. The sensor of the present invention uses Fe2O3 / NiO as the negative electrode and a platinum sheet as the positive electrode, and forms a closed loop through a H2O2 solution of a certain concentration, realizes the release of electrical energy under light conditions, and realizes the detection of H2O2 by monitoring the dependence of the maximum discharge power generated by the sensor on the H2O2 concentration. The results show that the detection sensitivity of the self-powered enzyme-free hydrogen peroxide sensor for H2O2 in the concentration range of 0.2 to 3.2 mmol / L is 36.19 μWcm ‑2 mM ‑1 , and the linear correlation coefficient is 0.998. The self-powered photoelectrochemical hydrogen peroxide sensor designed by the invention has high sensitivity, convenient operation, low cost, environmental friendliness, and good stability and selectivity.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and in particular to a preparation method and a detection method of a Fe2O3 / NiO photoanode-based self-powered photoelectrochemical hydrogen peroxide sensor. Background Art

[0002] The determination of H2O2 has gradually attracted attention due to its diverse applications in food production, environmental monitoring, industrial analysis and other fields. Traditional detection methods such as fluorescence and chromatography generally have problems such as long cycles and cumbersome steps. Photoelectrochemical sensors are easy to miniaturize, simple in equipment and easy to operate, which greatly reduces time and price costs. In the context of advocating energy conservation and environmental protection, self-powered photoelectrochemical sensors not only have the advantages of high sensitivity, economical and simple operation of photoelectrochemical sensors, but also can generate electricity by themselves, without the need for external power input. The electricity generated by their own chemical reactions can be used to determine H2O2, so they have a very broad application prospect.

[0003] Hematite has a narrow band gap (2.1eV) and has the advantages of being non-toxic, low cost, highly plastic, environmentally friendly and stable, and is widely used in photoelectrochemical analysis. Although Fe2O3 has great application potential in photoelectrochemical sensors, its low carrier concentration and short hole diffusion length (LD~2-4nm) lead to problems such as strong photogenerated electron-hole recombination, poor charge separation and transport capacity. Co-catalysts can reduce the reaction energy barrier and improve the efficiency of surface catalytic reactions, which is of great significance for the development of efficient catalytic systems. At present, there is no self-powered photoelectrochemical sensor based on Fe2O3 electrodes for the detection of H2O2. Summary of the invention

[0004] In view of the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a preparation method and detection method of a self-powered photoelectrochemical hydrogen peroxide sensor, which does not require additional voltage input and is more intelligent and energy-saving than conventional photoelectrochemical sensors. The light source and the electrochemical detection instrument are independent of each other, the sample preparation steps are simple, and the equipment is small, which gives it the advantages of high sensitivity, extreme economy and convenient operation. After actual investigation, it also has good stability and selectivity.

[0005] In order to achieve the above-mentioned purpose, the present invention discloses a self-powered photoelectrochemical hydrogen peroxide sensor based on Fe2O3 / NiO photoanode, which comprises a two-electrode system consisting of Fe2O3 / NiO electrode as a negative electrode and a Pt sheet or Pt wire as a positive electrode, which is inserted into an electrolyte to form a closed loop, and the discharge signal is detected by an electrochemical workstation to determine the H2O2 concentration.

[0006] In addition, the present invention also discloses a detection method of the above-mentioned Fe2O3 / NiO photoanode self-powered photoelectrochemical hydrogen peroxide sensor, which includes inserting a two-electrode system consisting of an Fe2O3 / NiO electrode as a negative electrode and a Pt sheet or a Pt wire as a positive electrode into an electrolyte containing H2O2 to form a closed loop, and detecting the discharge signal through an electrochemical workstation, recording the maximum discharge power under light conditions, and determining the concentration of H2O2 based on the maximum discharge power value.

[0007] Furthermore, the electrolyte is a sodium hydroxide solution; the concentration of the sodium hydroxide solution is 0.05-1.0 mol / L.

[0008] Furthermore, the concentration of H2O2 in the electrolyte is 0.2-3.2 mmol / L; the detection sensitivity of the self-powered photoelectrochemical hydrogen peroxide sensor to H2O2 is 36.19 μW cm -2 mM -1 , the detection linear correlation is 0.998.

[0009] Furthermore, the self-powered photoelectrochemical hydrogen peroxide sensor has a stability of more than 14 days and has good anti-interference properties against interferents such as ascorbic acid, uric acid, dopamine and conventional inorganic salts.

[0010] Furthermore, the self-powered photoelectrochemical hydrogen peroxide sensor has good detection and recovery capabilities for actual samples.

[0011] Furthermore, the Fe2O3 / NiO electrode comprises a FTO conductive substrate and a Fe2O3 / NiO film composited on the surface of the FTO.

[0012] Furthermore, the preparation of the Fe2O3 / NiO electrode comprises the following steps:

[0013] (1) taking the pre-treated FTO conductive substrate and placing it in a precursor solution, first reacting it at 80-100°C for 2-8h, taking out the obtained reaction intermediate, rinsing it with deionized water and drying it, then heating it to 300-600°C at a rate of 5-15°C / min and calcining it for 2-5h, and then calcining it at 750-850°C for 10-30min to obtain a Fe2O3 film covering the surface of the FTO; the precursor solution is an aqueous solution containing urea and ferric chloride hexahydrate, the concentration of ferric chloride hexahydrate (FeCl3·6H2O) in the precursor solution is 0.1-0.3 mol / L, and the molar ratio of ferric chloride hexahydrate (FeCl3·6H2O) to urea (Urea) is 1:4-2:1, preferably, the molar ratio of ferric chloride hexahydrate (FeCl3·6H2O) to urea (Urea) is 4:3;

[0014] (2) Spin coating a 0.01-1 mol / L nickel nitrate solution at a speed of 2000-6000 r / min for 5-60 s on the Fe2O3 thin film electrode obtained in (1), let it stand for 5-30 min after spin coating, then put it into a 0.5-1.5 mol / L NaOH solution and soak it for 4-20 min, take it out, rinse it with deionized water and dry it, then heat it to 300-400°C at a speed of 5-15°C / min and anneal it for 1-5 h to obtain a Fe2O3 / NiO electrode.

[0015] Furthermore, the pretreatment step of the FTO conductive substrate in step (1) includes: ultrasonically cleaning it with an organic solvent and deionized water before use.

[0016] Furthermore, the annealing step in step (2) is: heating to 320-380°C at a rate of 5-15°C / min and then annealing for 1-5h; more preferably, the annealing step is: heating to 340-360°C at a rate of 5-15°C / min and then annealing for 2-3h; most preferably, the annealing step is: heating to 350°C at a rate of 5-15°C / min and then annealing for 2h.

[0017] Furthermore, the Fe2O3 / NiO film includes a Fe2O3 layer vertically arranged in a nanorod array on a conductive substrate and a NiO layer with nanoparticles attached to the surface of Fe2O3. The thickness of the FTO conductive substrate is 400-500nm, and the thickness of the Fe2O3 / NiO film is 500-550nm, preferably 510-530nm.

[0018] Furthermore, the size of the FTO conductive glass is 1-10 cm×1-10 cm.

[0019] Compared with the prior art, the technical solution of the present invention has the following advantages and beneficial technical effects:

[0020] 1. Compared with conventional photoelectrochemical hydrogen peroxide sensors, the self-powered photoelectrochemical hydrogen peroxide sensor of the present invention does not require additional voltage input when detecting H2O2, which is more intelligent and energy-saving.

[0021] 2. The present invention firstly applies Fe2O3 / NiO electrode to construct a self-powered photoelectrochemical sensor. By modifying the NiO layer on the Fe2O3 electrode, on the one hand, the Fe2O3 photoanode carrier recombination efficiency is reduced and the carrier separation efficiency is improved. On the other hand, NiO itself can electro-oxidize H2O2, thereby promoting the excellent detection performance of the sensor, which is specifically manifested as: the sensitivity is 36.19μW cm in the range of 0.2-3.2mM H2O2 concentration -2 mM -1 .

[0022] 3. The Fe2O3 / NiO electrode material used in the self-powered photoelectrochemical hydrogen peroxide sensor of the present invention is easy to prepare, low in cost, environmentally friendly, and has good stability and selectivity.

[0023] In summary, the self-powered photoelectrochemical hydrogen peroxide sensor proposed in the present invention introduces the photocatalytic fuel cell reaction into the field of H2O2 detection. It has novel subject matter and has the advantages of simple preparation method, strong sensitivity, low cost, good stability and good selection, opening up a new way for H2O2 detection and analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The front morphology image (a) of the Fe2O3 electrode prepared in Example 1 of the present invention under a scanning electron microscope (SEM), the front morphology image (b) of Fe2O3 / NiO, and the side morphology image (c) of the Fe2O3 / NiO electrode.

[0025] Figure 2 : (a) is the X-ray diffraction (XRD) pattern of Fe2O3 and Fe2O3 / NiO electrodes prepared in Example 1 of the present invention, and (b) is the high-resolution X-ray photoelectron spectroscopy (XPS) pattern of Ni 2p.

[0026] Figure 3 The current density-voltage (JV) curve (a), the current density-power density (JP) curve (b), the linear fitting curve of the maximum power density varying with the H2O2 concentration (c) of the self-powered photoelectrochemical hydrogen peroxide sensor prepared in Example 1 of the present invention, and the linear fitting curve of the maximum power density varying with the H2O2 concentration of the self-powered photoelectrochemical hydrogen peroxide sensor based on pure Fe2O3 electrode (d). DETAILED DESCRIPTION

[0027] The applicant will further describe the technical solution of the present invention below in conjunction with specific embodiments and drawings, but the scope of protection requested by the present invention is not limited to these embodiments.

[0028] Example 1

[0029] This embodiment discloses a method for preparing a self-powered photoelectrochemical hydrogen peroxide sensor based on Fe2O3 / NiO photoanode, and the specific preparation steps are as follows:

[0030] (1) First, use laundry detergent to remove dust from the surface of the FTO conductive substrate (size: 1 cm × 3 cm), then use deionized water and ethanol ultrasonic cleaning for 15 min respectively, and blow dry with a hair dryer for later use.

[0031] (2) Take 15 mL of 0.2 mol / L ferric chloride hexahydrate (FeCl3·6H2O) aqueous solution, add 0.135 g of urea to the solution to make its concentration 0.15 mol / L, and stir at 600 rpm for about 15 min to form a brown-yellow clear precursor solution.

[0032] (3) The solution in (2) was transferred to a 30 mL glass bottle with a lid. The dry and clean FTO was then placed in the glass bottle at an angle of about 30°. The bottle cap was tightly closed and placed in a 100°C oven for 4 h. After cooling, the FTO was rinsed with deionized water and placed in a ventilated place to dry. The FTO was then placed in a muffle furnace and heated to 500°C at 5°C / min for 3 h for calcination. After the sample cooled, it was directly placed in a 800°C oven for 13 min. After cooling, the Fe2O3 film covering the surface of the FTO was obtained.

[0033] (4) A 0.1 mol / L nickel nitrate solution was spin coated on the Fe2O3 thin film electrode at a speed of 4000 r / min for 10 s, and then allowed to stand for 5 min. The electrode was then placed in a 1 mol / L NaOH solution and soaked for 4 min. The electrode was then taken out and rinsed with deionized water and dried with a hair dryer. Finally, the prepared sample was placed in a muffle furnace and heated to 350°C at 5°C / min for annealing for 2 h to obtain a Fe2O3 / NiO electrode.

[0034] (5) The Fe2O3 / NiO electrode prepared in step (4) is used as the negative electrode, and the Pt sheet is used as the positive electrode to form a two-electrode system, wherein the electrolyte is 1 mol / L sodium hydroxide, thereby obtaining a self-powered photoelectrochemical hydrogen peroxide sensor.

[0035] Example 2

[0036] This example discloses the morphology and structural characterization of the Fe2O3 and Fe2O3 / NiO electrodes prepared in Example 1.

[0037] First, the front and side morphologies of Fe2O3 and Fe2O3 / NiO electrodes were observed using field emission SEM. Figure 1 As shown in (a) and (c), Fe2O3 presents a smooth surface with a round top and a narrow bottom nanorod structure, which grows vertically on the FTO conductive substrate. After being modified by the NiO layer, Figure 1 As shown in (b), the surface is obviously rough, and NiO is attached to Fe2O3 in granular form. Figure 1 (c) is the SEM side morphology of the Fe2O3 / NiO film. The results show that the height of the Fe2O3 / NiO film is about 523nm and the thickness of the FTO conductive substrate is about 409nm.

[0038] Then the phases of Fe2O3 and Fe2O3 / NiO electrodes were investigated by XRD. Figure 2 (a), according to the standard card JCPDS#33-0664, the XRD diffraction peaks at 35.7° and 64.1° are attributed to the (110) and (300) crystal planes of α-phase Fe2O3. Due to the small amount of NiO modification, no characteristic peaks related to NiO were observed in the XRD spectrum.

[0039] Then, the chemical valence states of Ni 2p on Fe2O3 and Fe2O3 / NiO electrodes were analyzed by X-ray photoelectron spectroscopy (XPS). Figure 2 (b) is the Ni 2p XPS high-resolution spectrum. Obviously, the Ni 2p signal can be detected on the Fe2O3 / NiO electrode, but not on the α-Fe2O3 electrode. Further analysis shows that the XPS peaks at 873.1 and 855.38 eV correspond to Ni 2p1 / 2 and Ni 2p3 / 2, respectively. The difference in spin-orbit splitting energy is 17.72 eV, which can be inferred to be the characteristic peak of NiO, indicating that NiO is successfully modified on the α-Fe2O3 electrode. In addition, the XPS peaks at 861.43 and 879.64 eV are a pair of satellite peaks of Ni 2p.

[0040] Example 3

[0041] This embodiment discloses a detection method of a self-powered photoelectrochemical hydrogen peroxide sensor based on Fe2O3 / NiO photoanode, wherein the self-powered photoelectrochemical hydrogen peroxide sensor comprises the following detection steps: a two-electrode system consisting of a Fe2O3 / NiO electrode as a negative electrode and a Pt sheet as a positive electrode is placed in a 1 mol / L NaOH electrolyte containing a certain concentration of H2O2, and connected to a Shanghai Chenhua CHI660D electrochemical workstation. In simulated sunlight (light source: AM1.5G solar simulator, light intensity: 100mW / cm 2 ) irradiation, the linear scanning technique was used to collect the current density-voltage (JV) signal curve. Figure 3 (a) is a series of JV curves collected when 0.2mmol / LH2O2 is gradually added to the electrolyte solution. It can be seen that as the concentration of H2O2 in the electrolyte increases, the discharge voltage and current increase significantly. The current density-power curve (JP) curve is obtained by the P=JV formula, as shown in Figure 3 (b), it can be seen that in the range of 0.2~3.2mmol / LH2O2 concentration, the discharge power increases with the increase of H2O2 concentration. A scatter plot is made with H2O2 concentration as the horizontal axis and the maximum discharge power density of Fe2O3 / NiO as the vertical axis, as shown in Figure 3 (c) By fitting the scattered points, the linear regression equation is obtained as P max / μW cm -2=36.19C / mM+(-1.92), and the linear correlation coefficient is 0.998, which indicates that the Fe2O3 / NiO photoanode self-powered photoelectrochemical hydrogen peroxide sensor has a very good linear sensing ability for H2O2 in the concentration range of 0.2-3.2mmol / L, and the detection sensitivity of H2O2 is 36.19μW cm -2 mM -1 .

[0042] As a comparison, this example investigates the detection performance of a pure Fe2O3 electrode as a self-powered photoelectrochemical hydrogen peroxide sensor. Figure 3 (d), the linear regression equation between the H2O2 concentration and the maximum discharge power density of the pure Fe2O3 electrode is P max / μW cm -2 =17.31C / mM+3.69, the linear correlation coefficient is 0.980, and the detection sensitivity of H2O2 in the concentration range of 0.2-3.2mmol / L is 17.31μW cm -2 mM -1 , which is only 1 / 2 of that of Fe2O3 / NiO electrode. In addition, the linear correlation coefficient of H2O2 detection of Fe2O3 electrode modified by NiO is improved, and the discharge performance is increased to nearly 2 times of that of pure Fe2O3 electrode.

[0043] Example 4

[0044] This embodiment discloses a method for detecting actual samples by a self-powered photoelectrochemical hydrogen peroxide sensor based on a Fe2O3 / NiO photoanode. In order to investigate the application capability of the sensor for detecting actual H2O2 samples, the present invention carried out a recovery experiment on three Fe2O3 / NiO electrode samples obtained according to the preparation method of Example 1. First, we added a certain amount of H2O2 to the electrolyte (1mol / LNaOH) to make the concentration known, which were 0.8, 1.6, 2.4 and 3.2mol / L respectively. Taking 0.8mol / LH2O2 as an example, the detection steps are as follows: Fe2O3 / NiO electrode is used as the negative electrode and Pt sheet is used as the positive electrode to form a two-electrode system, which is inserted into an electrolyte containing a known 0.8mol / LH2O2, and connected to Shanghai Chenhua CHI660D electrochemical workstation, and under illumination (light source: AM1.5G solar simulator, light intensity: 100mW / cm 2 ) and the maximum discharge power of Fe2O3 / NiO photoelectrode was collected according to the linear regression equation P max / μW cm -2=36.19C / mM+(-1.92) to calculate the actual measured H2O2 concentration. The test results are shown in Table 1, which shows the recovery experimental results of H2O2 by the self-powered photoelectrochemical hydrogen peroxide sensor prepared in Example 1 of the present invention. For H2O2 solutions with concentrations of 0.8, 1.6, 2.4 and 3.2 mol / L, the average recovery rates of the three samples were 100.76%, 100.97% and 95.53%, respectively, which shows that the self-powered photoelectrochemical hydrogen peroxide sensor prepared by us has high accuracy in the actual detection process.

[0045] Table 1

[0046]

[0047] In summary, the Fe2O3 / NiO photoanode-based self-powered photoelectrochemical hydrogen peroxide sensor designed in the present invention combines the advantages of both photoelectrochemical sensors and fuel cells. It is not only highly sensitive and easy to miniaturize, but also self-powered and low-cost. In addition, it also has good selectivity and stability.

[0048] The above embodiments are only the best examples, and are not intended to limit the implementation of the present invention. In addition to the above embodiments, the present invention has other implementations. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A detection method based on Fe2O3 / NiO photoanode self-powered photoelectrochemical hydrogen peroxide sensor, characterized in that: The self-powered photoelectrochemical hydrogen peroxide sensor comprises: inserting a two-electrode system consisting of a Fe2O3 / NiO electrode as a negative electrode and a Pt sheet or a Pt wire as a positive electrode into an electrolyte containing 0.2-3.2 mmol / L H2O2 to form a closed loop, detecting a discharge signal through an electrochemical workstation, recording the maximum discharge power under light conditions, and determining the concentration of H2O2 according to the maximum discharge power value; The Fe2O3 / NiO electrode comprises a conductive substrate and a Fe2O3 / NiO film composited on the surface of the conductive substrate; The Fe2O3 / NiO film comprises a Fe2O3 layer vertically arranged in a nanorod array on a conductive substrate and a NiO layer with nanoparticles attached to the surface of the Fe2O3; The preparation of the Fe2O3 / NiO electrode comprises the following steps: (1) The pre-treated conductive substrate is placed in a precursor solution, first reacted at 80-100°C for 2-8 h, the obtained reaction intermediate is taken out, rinsed with deionized water and air-dried, then heated to 300-600°C and calcined for 2-5 h, and then calcined at 750-850°C for 10-30 min to obtain a Fe2O3 film covering the surface of the conductive substrate; the precursor solution is an aqueous solution containing urea and ferric chloride hexahydrate, the concentration of ferric chloride hexahydrate in the precursor solution is 0.1-0.3 mol / L, and the molar ratio of ferric chloride hexahydrate to urea is 1:4-2:1; (2) Spin coat 0.01~1 mol / L nickel nitrate solution at 2000~6000 r / min for 5~60 s on the Fe2O3 thin film electrode obtained in (1). Let it stand for 5~30 min after spin coating. Then soak it in 0.5~1.5 mol / L NaOH solution for 4~20 min, rinse it with deionized water and dry it. Then heat it to 300~400 ℃ and anneal it for 1~5 h to obtain Fe2O3 / NiO electrode.

2. The detection method according to claim 1, characterized in that: The Fe2O3 / NiO film has a thickness of 500-550 nm.

3. The detection method according to claim 2, characterized in that: The thickness of the Fe2O3 / NiO film is 510-530nm.

4. The detection method according to any one of claims 1 to 3, characterized in that: The electrolyte is a sodium hydroxide solution.

5. The detection method according to claim 4, characterized in that: The concentration of the sodium hydroxide solution is 0.05-1.0 mol / L.

6. The detection method according to claim 1, characterized in that: The annealing step in step (2) is: heating to 320-380°C and then annealing for 1-5 hours.

7. The detection method according to claim 6, characterized in that: The annealing step is: heating to 340-360°C and then annealing for 2-3 hours.

8. The detection method according to claim 7, characterized in that: The annealing step is: heating to 350°C and then annealing for 2 hours.

9. The detection method according to claim 1, characterized in that: The conductive substrate in step (1) is FTO conductive glass.

10. The detection method according to claim 1, characterized in that: The pretreatment step of the conductive substrate in step (1) includes: ultrasonically cleaning the conductive substrate with an organic solvent and deionized water before use.

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