A method of measuring the ph of an aqueous solution

Abstract

The application relates to a method for measuring the pH of an aqueous solution, comprising the following steps: taking a hydrophilic electrode coated with nano TiO2 as a photo-anode, taking a cleaned conductive electrode as a photo-cathode, placing a solution to be measured between the two electrodes, measuring the photo-induced potential difference between the two electrodes under a standard sunlight illumination condition, and converting the pH value of the solution to be measured according to the relationship between the open-circuit voltage V and the pH value; the relationship is y=0.0262x+0.0922; wherein y is the open-circuit voltage V, and x is the pH value of the solution. The application proposes a method for measuring the pH of an aqueous solution by taking a hydrophilic electrode as a working electrode of a photoelectric sensor, and the method has the advantages of simple and economical preparation of the hydrophilic electrode, simple and easy-to-operate solution pH measurement, high sensitivity, wide application range, simple electrode maintenance and the like.

Description

Technical Field

[0001] This invention belongs to the field of photoelectric sensor technology, and specifically relates to a method for measuring the pH of an aqueous solution. Background Technology

[0002] Traditional methods for measuring the pH of aqueous solutions include pH test strips, pH indicators, and pH meters. pH test strips and pH indicators use color to indicate the pH value, but neither method can accurately determine the specific pH value; they only provide an approximate pH range, resulting in poor precision. Using a pH meter often requires a large volume of solution, and the pH value takes time to stabilize, failing to meet the requirements for high-precision real-time recording. Furthermore, pH meters require regular maintenance of the glass electrode to ensure their accuracy. Summary of the Invention

[0003] To address the problems of existing aqueous solution pH measurement techniques, this invention provides a pH measurement method that is highly accurate, widely applicable, simple to test and maintain, and requires minimal solution. A hydrophilic electrode is fabricated as the photoanode of a photoelectric sensor, and the pH value of the solution is calculated based on the potential difference between the photoanode and photocathode after illumination.

[0004] The specific method is as follows:

[0005] 1. Preparation of hydrophilic electrodes

[0006] First, the conductive substrate (such as conductive glass, conductive film, metal, etc.) is cleaned. Then, a nano-TiO2 precursor solution is spin-coated onto the conductive substrate or a simple hydrothermal method is used to prepare a hydrophilic electrode with nano-TiO2 particles on the surface.

[0007] 2. Solution pH Measurement Method

[0008] like Figure 1 As shown, a hydrophilic electrode coated with nano-TiO2 was used as the photoanode. Figure 1 In part 1), cleaned electrodes such as conductive glass, conductive film, and metal are used as photocathodes. Figure 1 3) The solution to be tested ( Figure 1 2) Place it between the two electrodes and measure the photogenerated potential difference (i.e., open circuit voltage V) between the two electrodes under standard sunlight illumination conditions. Calculate the pH value of the solution to be tested based on the relationship between open circuit voltage V and pH value.

[0009] The application has the advantages that the application provides a method for measuring pH of aqueous solution by using a hydrophilic electrode as working electrode of photoelectric sensor, the method has the advantages of simple and economical preparation method of hydrophilic electrode, simple and easy operation of solution pH measurement method, high sensitivity, wide application range, simple electrode maintenance, etc. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 Figure 1 is a schematic diagram of the method for measuring pH of solution;

[0011] Figure 2 Figure 4 is a scanning electron microscope image of the hydrophilic electrode;

[0012] Figure 3 Figure 5 is a water contact angle of the hydrophilic electrode;

[0013] Figure 4 Figure 6 is a photogenerated potential difference between the hydrophilic electrode and the photo-cathode in different standard pH solutions;

[0014] Figure 5 Figure 7 is a relationship between open circuit voltage and solution pH value. DETAILED DESCRIPTION

[0015] (1) The preparation method of the hydrophilic electrode is as follows:

[0016] The preparation method of the hydrophilic electrode coated with nano-TiO2(anatase phase) is as follows: a layer of anatase titanium dioxide nanoparticles is prepared on a fluorine-doped SnO2FTO conductive substrate or an indium-doped SnO2ITO conductive substrate by spin coating (the electron microscope result is shown in Figure 4). Figure 2 Specific preparation method is as follows: titanium diisopropylate(acetylpropionate) (75wt%, isopropyl alcohol) is dissolved in 1-butanol (99.8%) solution to obtain a titanium dioxide precursor solution, a small amount of the precursor solution is spin coated on a cleaned FTO conductive glass at 600 rpm for 6 seconds, and then spin coated at 2000 rpm for 30 seconds. Finally, the hydrophilic electrode containing anatase titanium dioxide nanoparticles on the surface is obtained by calcining at 450°C for 30 minutes, and the water contact angle is shown in Figure 5, which is 9.6°. Figure 3

[0017] ​The method for preparing the hydrophilic electrode coated with nano-TiO2(rutile phase) is as follows: a layer of rutile phase titanium dioxide nanorod is prepared on the FTO conductive substrate of fluorine-doped SnO2 by using hydrothermal method. The specific preparation method is described as follows: firstly, deionized water and 36% hydrochloric acid solution are mixed according to the volume ratio of 1:1, and then tetrabutyl titanate solution is added, and the volume ratio of the tetrabutyl titanate solution to the above-mentioned deionized water and hydrochloric acid mixed solution is 0.016:1; after stirring for 30 min, a precursor solution is prepared, then the FTO conductive glass which is washed thoroughly is put into a reaction kettle containing the above-mentioned titanium dioxide precursor solution, and hydrothermal reaction is carried out at 150°C for 5h, after the hydrothermal reaction is completed, the FTO conductive glass is taken out, and is annealed at 550°C for 3h in air atmosphere, thereby obtaining the hydrophilic electrode containing rutile phase nano-titanium dioxide rod on the surface, and the water contact angle of which is 11.2°.

[0018] (2) The test method of the solution pH value is described as follows:

[0019] Firstly, the hydrophilic electrode (coated with nano-TiO2 anatase phase) is used as the photoanode (with a size of 2*3 cm), the conductive electrode is used as the photocathode (with a size of 2*3 cm), the photoanode and the photocathode are placed in a pH standard solution, under the illumination of a standard sunlight, the photogenerated potential difference between the photoanode and the photocathode (i.e. the open circuit voltage V, generally the open circuit voltage can be stable after 10s of illumination) is read by using a voltmeter. By measuring the open circuit voltage of the photoanode and the photocathode in the pH standard solution (the solution pH values are 2, 4, 6, 8, 10, 12 and 14 respectively) under illumination, the relationship formula between the open circuit voltage V( Figure 4 ) and the pH value is determined. Figure 5 ) The relationship formula is y=0.0262x+0.0922; wherein y is the open circuit voltage V, and x is the solution pH value.

[0020] Then, the photoanode and the photocathode are washed with deionized water, and then the solution to be measured (the minimum solution volume required for testing is 70μL, and the maximum volume is 20mL) is added between the two electrodes, under illumination, the photogenerated potential difference U between the photoanode and the photocathode is read by using a voltmeter.

[0021] Finally, the photogenerated potential difference U measured in the above step is brought into the relationship formula between the open circuit voltage V and the solution pH value obtained in the first step, thereby the pH value of the solution to be measured can be calculated.

[0022] In addition, the relationship formula between the open circuit voltage V and the pH value of the hydrophilic electrode (coated with nano-TiO2 rutile phase) used as the photoanode is y=0.0296x+0.0732; wherein y is the open circuit voltage V, and x is the solution pH value.

[0023] (3) The electrode long-term stability test is explained as follows:

[0024] The prepared hydrophilic electrode is placed in a dry fresh-keeping box and stored at room temperature for 7 days, 14 days and 28 days, and then the measured pH values of the standard pH solution are compared (Table 1). The experimental results show that the water solution pH measurement method has high sensitivity, and the storage and maintenance of the hydrophilic electrode are relatively simple, which only needs to be cleaned with deionized water before use to ensure the stability of the measurement results.

[0025] Table 1 Results of hydrophilic electrode stability test (n = 5)

[0026] pH value 2.0 4.0 6.0 8.0 10.0 12.0 7 days 1.98 4.02 6.05 7.89 10.06 12.01 14 days 2.03 4.05 5.97 8.06 10.03 11.96 28 days 2.01 3.99 6.03 8.05 10.05 12.03

[0027] The above only describes the preferred embodiments of the present application, and any equivalent changes and modifications made within the scope of the patent application of the present application shall be included in the scope of the present application.

Claims

1. A method of measuring the pH of an aqueous solution, characterized by, The surface of the hydrophilic electrode is coated with nano-TiO2, and the cleaned conductive electrode is used as the photo-cathode; the solution to be measured is placed between the two electrodes, and the photo-induced potential difference between the two electrodes is measured under standard sunlight; the pH value of the solution to be measured is calculated according to the relationship between the open circuit voltage V and the pH value; the TiO2 includes an anatase phase and a rutile phase; the relationship when the anatase phase of TiO2 is used as the hydrophilic electrode is y=0.0262x+0.0922; the relationship when the rutile phase of TiO2 is used as the hydrophilic electrode is y=0.0296x+0.0732; wherein y is the open circuit voltage V, and x is the pH value of the solution; The preparation method of the hydrophilic electrode coated with the nano-TiO2 anatase phase is as follows: a layer of anatase phase titanium dioxide nanoparticles is prepared on a fluorine-doped SnO2 FTO conductive substrate or an indium-doped SnO2 ITO conductive substrate by using a spin coating method; The preparation method of the hydrophilic electrode coated with the nano-TiO2 anatase phase specifically includes the following steps: 0.15M titanium isopropoxide is dissolved in a 1-butanol solution to prepare a titanium dioxide precursor solution; a small amount of the precursor solution is spin-coated on the cleaned FTO conductive glass at 600rpm for 6 seconds, and then spin-coated at 2000rpm for 30 seconds; finally, the sample is calcined at 450℃ for 30 minutes; The preparation method of the hydrophilic electrode coated with the nano-TiO2 rutile phase is as follows: a layer of rutile phase titanium dioxide nanorods is prepared on a fluorine-doped SnO2 FTO conductive substrate by using a hydrothermal method; The preparation method of the hydrophilic electrode coated with the nano-TiO2 rutile phase specifically includes the following steps: first, deionized water and 36% hydrochloric acid solution are mixed according to a volume ratio of 1:1, and then tetrabutyl titanate solution is added; after stirring for 30min, a precursor solution is prepared; then, the fully cleaned FTO conductive glass is placed in a reaction kettle containing the aforementioned precursor solution, and the hydrothermal reaction is carried out at 150℃ for 5h; after the hydrothermal reaction is completed, the FTO conductive glass is taken out and annealed at 550℃ for 3h in an air atmosphere, thereby obtaining a hydrophilic electrode containing rutile phase nano-titanium dioxide rods on the surface.

2. The method of measuring the pH of an aqueous solution according to claim 1, wherein, The conductive electrode includes conductive glass, conductive film or metal electrode.

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