Flower-shaped Manganese Cobalt Oxide Modified Titanium Dioxide Photoanode and Its Preparation Method

Abstract

The present invention relates to the technical field of cathodic protection, in particular to a flower-shaped manganese cobalt oxide modified titanium dioxide photoanode and its preparation method and application. A flower-shaped manganese cobalt oxide modified titanium dioxide photoanode (MnCo2O4 / TiO2) is prepared. The present invention also provides a preparation method for the above composite photoanode. The composite photoanode of the present invention improves the utilization rate of sunlight, reduces the electrode potential of the metal, and prevents metal corrosion. The photoanode of the present invention promotes the separation of photo-generated carriers, and the photoanode of the present invention has a large specific surface area and excellent catalytic performance.

Description

Technical Field

[0001] The present invention relates to the technical field of cathodic protection, and particularly to a flower-shaped manganese cobaltate modified titanium dioxide photoanode, a preparation method thereof, and an application thereof. Background Art

[0002] When a semiconductor is irradiated with light, after electrons absorb energy, they will transition from the valence band to the conduction band, forming free electrons that can conduct electricity on the conduction band. At the same time, corresponding holes will be left in the valence band, and this process is the separation of electrons and holes. Among the generated free electrons, some will recombine with the holes, thus unable to play the role of cathodic protection. And another part of the electrons, under the influence of an applied electric field, will migrate to the semiconductor surface and then be transmitted to the coupled metal material through an external wire, while the photo-generated holes react with reducing substances in the environment and are consumed. If the speed of photo-generated electrons transferring to the metal is faster than its consumption speed, the photo-generated electrons will accumulate in the protected metal, thereby shifting its potential negatively and being protected.

[0003] Titanium dioxide is a material with a high dielectric constant and good electrical conductivity. Titanium dioxide has three types of crystal forms, namely rutile, anatase, and brookite. Among them, the band gaps of the anatase phase, rutile phase, and brookite phase are 3.2 eV, 3.02 eV, and 2.96 eV respectively, and the anatase and brookite phases will transform into the rutile phase at 600 - 800 °C. In actual use, due to the unstable crystal structure of the brookite crystal phase, it is rarely studied. The rutile phase and anatase phase TiO2 have different band structures and physicochemical properties due to different octahedral arrangements. Comparatively, the rutile phase TiO2 has better stability. However, the anatase phase TiO2 has a larger specific surface area and a higher Fermi level, and thus has higher photocatalytic activity.

[0004] In order to adjust the structure of TiO2, reduce the band gap, and improve energy capture, modification methods such as metal or ion doping, noble metal deposition, polymer composite, and semiconductor composite can be used to improve the utilization rate of light energy in the visible light region. However, in order to be better applied to photo-induced cathodic protection, the recombination of photo-generated electrons and holes should also be inhibited so that electrons can be transferred to the protected metal, and excellent structural design has an optimizing effect on the conduction and extraction of electrons. Summary of the Invention

[0005] The purpose of the present invention is to provide a flower-shaped manganese cobaltate modified titanium dioxide photoanode, a preparation method thereof, and an application thereof by modifying to reduce the band gap of TiO2, increase the specific surface area, have sufficient active sites, and extend the electron lifetime so as to improve the catalytic activity and stability.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] A preparation method of a flower-shaped manganese cobaltate modified titanium dioxide photoanode, on the surface of a TiO2 nanotube array, MnCo2O4 nanosheets are loaded by a hydrothermal method and then calcined to form a flower-shaped manganese cobaltate modified titanium dioxide photoanode.

[0008] Specifically

[0009] (1) Prepare a TiO2 nanotube array on the pretreated Ti substrate by anodization.

[0010] (2) Realize the loading of sheet-like MnCo2O4 on the surface of the TiO2 nanotube array by a hydrothermal method.

[0011] (3) Calcinate the hydrothermal composite material to form flower-shaped MnCo2O4 at the orifice of the TiO2 nanotube array.

[0012] In the step (1), the TiO2 nanotube array is prepared by anodizing the pretreated Ti substrate into a TiO2 nanotube array with an inner diameter of 120 - 150 nm and a tube wall thickness of 11 - 16 nm.

[0013] The pretreatment of the Ti substrate refers to polishing the titanium foil with a chemical polishing solution for 30 - 60 s, and then performing ultrasonic cleaning alternately in deionized water and ethanol; the polishing solution is a mixed solution of 0.9 g NH4F, 5 ml H2O, 12 ml HNO3 and 12 ml H2O2.

[0014] The anodization method refers to using a platinum sheet as the counter electrode, the pretreated Ti substrate as the working electrode, oxidizing in the electrolyte at a voltage of 60 V for 1 h, then calcining at 430 - 450 °C for 2 h, and cooling to room temperature with the furnace to obtain the TiO2 nanotube array.

[0015] The electrolyte is a mixed solution of 1.114 g NH4F, 30 ml H2O and 200 ml ethylene glycol.

[0016] The hydrothermal method includes:

[0017] (1) Weigh and mix manganese acetate with a manganese ion concentration of 1 - 10 mM and cobalt acetate with a cobalt ion concentration of 2 - 20 mM according to a molar ratio of 1:2.

[0018] (2) Add the above mixed powder to 30 - 40 mL of ethylene glycol containing 0.5 - 1 mL of deionized water.

[0019] (3) Then add 0.1 - 0.2 g of polyvinylpyrrolidone to the above solution and stir evenly.

[0020] (4) Transfer the mixed solution and the TiO2 nanotube array into a reaction kettle, with the TiO2 nanotube array immersed in the mixed solution; perform heat treatment at 170 - 180 °C for 11 - 12 h, air-cool to 23 - 25 °C, wash the sample with ethanol and deionized water, dry it at 70 - 80 °C for 10 - 12 h, and anneal the prepared precursor in air at 450 - 500 °C for 3 - 4 h to obtain MnCo2O4 / TiO2.

[0021] A flower-like manganese cobaltate modified titanium dioxide photoanode prepared by the method, prepare a flower-like manganese cobaltate modified titanium dioxide photoanode (MnCo2O4 / TiO2) according to the method, wherein the loaded flower-like MnFe2O4 has a particle size of 1.5 - 2.5 μm.

[0022] An application of the flower-like manganese cobaltate modified titanium dioxide photoanode, the application of the flower-like manganese cobaltate modified titanium dioxide photoanode (MnCo2O4 / TiO2) in preventing metal corrosion.

[0023] Compared with the prior art, the advantages of the present invention are:

[0024] (1) The flower-like manganese cobaltate provided by the present invention is different from one-dimensional or two-dimensional nanosheets, has a large specific surface area, the process method is simple, effectively improves the catalytic activity, and improves the protective effect of TiO2 on metals.

[0025] (2) By loading flower-like manganese cobaltate on the TiO2 nanorod array, the preparation conditions are controllable. It only needs to put the prepared TiO2 nanotube array and the MnCo2O4 mixed solution into the reaction kettle for heat treatment, and then perform drying treatment and calcination; the prepared MnCo2O4 / TiO2 heterojunction photoanode has a regular morphology.

[0026] (3) The utilization rate of sunlight by TiO2 is low, while the flower-like manganese cobaltate modified titanium dioxide of the present invention improves the absorption intensity of TiO2 in the visible light region. This photoanode can inhibit the recombination of photo-generated carriers, enhance the redox ability of the composite material, and improve the photo-generated cathodic protection performance. Description of the Drawings

[0027] Figure 1 It is a scanning electron microscope photograph of the TiO2 nanotube array obtained in Example 1 of the present invention;

[0028] Figure 2 It is a scanning electron microscope photograph of the MnCo2O4 / TiO2 photoanode obtained in Example 1 of the present invention;

[0029] Figure 3Open circuit potential diagrams of the MnCo2O4 / TiO2 photoanode obtained in Example 1 of the present invention and the TiO2 nanotube array coupled with 304 stainless steel respectively;

[0030] Figure 4 Transient photocurrent spectra of the MnCo2O4 / TiO2 photoanode obtained in Example 1 of the present invention and the TiO2 nanotube array coupled with 304 stainless steel respectively;

[0031] Figure 5 Scanning electron microscope photograph of the MnCo2O4 / TiO2 photoanode obtained in Example 2 of the present invention;

[0032] Figure 6 Open circuit potential diagrams of the MnCo2O4 / TiO2 photoanode obtained in Example 2 of the present invention and the TiO2 nanotube array coupled with 304 stainless steel respectively;

[0033] Figure 7 Transient photocurrent spectra of the MnCo2O4 / TiO2 photoanode obtained in Example 2 of the present invention and the TiO2 nanotube array coupled with 304 stainless steel respectively;

[0034] Figure 8 Scanning electron microscope photograph of the MnCo2O4 / TiO2 photoanode obtained in Example 3 of the present invention;

[0035] Figure 9 Open circuit potential diagrams of the MnCo2O4 / TiO2 photoanode obtained in Example 3 of the present invention and the TiO2 nanotube array coupled with 304 stainless steel respectively;

[0036] Figure 10 Transient photocurrent spectra of the MnCo2O4 / TiO2 photoanode obtained in Example 3 of the present invention and the TiO2 nanotube array coupled with 304 stainless steel respectively;

[0037] In the figure: ON - Turn on the light source; OFF - Turn off the light source; Detailed implementation mode

[0038] The following examples are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0039] The present invention grows TiO2 nanotubes on a titanium foil substrate and loads flower-like manganese cobaltate on the TiO2 nanotubes to form a heterojunction between titanium dioxide and manganese cobaltate. Specifically, the TiO2 nanotubes are prepared by an anodic oxidation method, the flaky MnCo2O4 is loaded by a hydrothermal method, and then the flakes are aggregated into a flower shape by calcination, so as to obtain the MnCo2O4 / TiO2 photoanode. Its morphology is complete and can be used as a photoanode. This heterojunction photoanode reduces the electrode potential of the metal, improves the response to visible light, and the flower-like manganese cobaltate can improve the electrochemical energy storage performance and provide protection for the metal in the dark state. This photoanode has stable performance, many active sites, and excellent redox performance.

[0040] Example 1

[0041] A preparation method of the MnCo2O4 / TiO2 photoanode includes the following steps:

[0042] (1) Pretreatment: Take a titanium foil with a specification of 40mm×10mm×0.1mm as the substrate, polish it in a polishing solution for 30 - 60s. The polishing solution is a mixed solution of 0.9g NH4F, 5ml H2O, 12ml HNO3, and 12ml H2O2, and then perform ultrasonic cleaning in deionized water and ethanol alternately for 5min.

[0043] (2) Preparation of TiO2 nanotubes: Weigh 1.114g of NH4F and dissolve it in 30ml of H2O, add it to 200ml of ethylene glycol electrolyte. Use the Ti foil as the anode connected to the working electrode, and the Pt plate as the cathode connected to the counter electrode. Perform anodic oxidation on the titanium foil for 1h at a voltage of 60V. Then anneal it in a muffle furnace at 450°C for 2h. Cool it to room temperature, and TiO2 nanotubes are formed on the Ti foil (see Figure 1 ).

[0044] (3) Preparation of the MnCo2O4 / TiO2 photoanode: Weigh 1mM of manganese acetate and 2mM of cobalt acetate and dissolve them in 40mL of ethylene glycol solution containing 0.5ml of deionized water, and ultrasonically vibrate for 30min to obtain a transparent solution. Then add 0.1095g of polyvinylpyrrolidone to the above transparent solution and ultrasonically vibrate for 15min. Transfer the solution and the TiO2 nanotubes to a reaction kettle, immerse the TiO2 nanotubes in the solution, react at 180°C for 12h, then cool the solution to room temperature, wash the sample with ethanol and deionized water, and dry it at 80°C for 12h. Subsequently, anneal the prepared precursor in the air at 500°C for 4h at a heating rate of 2°C / min. Thus, a MnCo2O4 / TiO2 film is formed on the titanium foil as a photoanode (see Figure 2 ).

[0045] Place the obtained TiO2 nanotube array on a scanning electron microscope for testing. From Figure 1It can be seen that the inner diameter of the TiO2 nanotubes is about 130 nm, the wall thickness is about 15 nm, and the TiO2 nanotube arrays are uniformly and closely arranged on the surface of the titanium foil.

[0046] The obtained MnCo2O4 / TiO2 photoanode was placed on a scanning electron microscope for testing. Figure 2 It can be seen that flower-like MnCo2O4 grows at the orifice of the nanotubes, and the particle size is about 1.5 μm.

[0047] The obtained MnCo2O4 / TiO2 photoanode was tested for photocathodic protection performance, and the obtained TiO2 nanotubes were used as a control. Using the MnCo2O4 / TiO2 photoanode and the TiO2 nanotube arrays as photoanodes, they were placed in a photoreactor containing a mixed solution of 0.1 M Na2S and 0.2 M NaOH. 304 stainless steel was used as the photocathode and placed in a corrosion cell containing 3.5 wt% NaCl solution. The two electrolytic cells were connected through a proton exchange membrane, and a saturated calomel electrode was used as the reference electrode and placed in the corrosion cell for open-circuit potential testing. Figure 3 It can be seen that when the TiO2 nanotubes are coupled with 304 stainless steel in the light-on state, the potential rapidly drops to a more negative position, gradually becomes stable and then reaches an equilibrium state, and the potential in the equilibrium state can drop to about -450 mV; when the MnCo2O4 / TiO2 photoanode is coupled with 304 stainless steel, the potential can drop to about -468 mV. When the dark state is restored, the electrode potential of the stainless steel begins to rise and returns to the original potential before illumination. At this time, the electrode potential of the 304 stainless steel is still lower than its self-corrosion potential. When illuminated again, the electrode potential of the stainless steel connected to the heterojunction photoanode rapidly drops to about -468 mV again, indicating that the heterojunction photoanode has good stability.

[0048] The obtained MnCo2O4 / TiO2 photoanode and TiO2 nanotubes were respectively connected to the working electrode and placed in a photoreactor containing 0.1 M Na2S solution and 0.2 M NaOH solution. 304 stainless steel was grounded and placed in a corrosion cell containing 3.5 wt% NaCl solution for transient photocurrent density curve measurement. Figure 4 It can be seen that under visible light irradiation, the photocurrent density of all samples shows a positive shift, indicating that electrons flow from the composite material to the surface of 304SS. The rapid decrease in the current density after the light is turned off is attributed to the rapid recombination of photo-generated electrons and holes. The stable value of the photocurrent generated by the MnCo2O4 / TiO2 photoanode can reach 23 μA / cm 2 , and the stable value of the photocurrent generated by the TiO2 nanotubes is only 3.4 μA / cm 2; It indicates that the photo-generated carriers of the MnCo2O4 / TiO2 photoanode can be effectively separated compared with the TiO2 nanotubes, resulting in better light response, indicating that the cathodic protection effect of this photoanode is better.

[0049] Example 2

[0050] Preparation method of MnCo2O4 / TiO2 photoanode, comprising the following steps:

[0051] (1) Pretreatment: Take a titanium foil with a specification of 40mm×10mm×0.1mm as the substrate, polish it in the polishing solution for 30 - 60s. The polishing solution is a mixed solution of 0.9g NH4F, 5ml H2O, 12ml HNO3 and 12ml H2O2, and then perform ultrasonic cleaning in deionized water and ethanol alternately for 5min.

[0052] (2) Preparation of TiO2 nanotubes: Weigh 1.114g NH4F and dissolve it in 30ml H2O, then add it to 200ml of ethylene glycol electrolyte. Use the Ti foil as the anode connected to the working electrode, and the Pt plate as the cathode connected to the counter electrode. Perform anodic oxidation on the titanium foil at 60V for 1h. Then anneal it in a muffle furnace at 450℃ for 2h. Cool to room temperature, and TiO2 nanotubes are formed on the Ti foil.

[0053] (3) Preparation of MnCo2O4 / TiO2 photoanode: Weigh 2mM manganese acetate and 4mM cobalt acetate and dissolve them in 40mL of ethylene glycol solution containing 0.5ml deionized water, and ultrasonicate for 30min to obtain a transparent solution. Then add 0.1095g of polyvinylpyrrolidone to the above transparent solution and ultrasonicate for 15min. Transfer the solution and TiO2 nanotubes to a reaction kettle, immerse the TiO2 nanotubes in the solution, react at 180℃ for 12h, then cool the solution to room temperature, wash the sample with ethanol and deionized water, and dry it at 80℃ for 12h. Subsequently, anneal the prepared precursor in air at 500℃ for 4h at a heating rate of 2℃ / min. Further, a MnCo2O4 / TiO2 film is formed on the surface of the titanium foil as the photoanode.

[0054] Place the obtained TiO2 nanotubes on a scanning electron microscope for testing. The inner diameter of the TiO2 nanotubes is about 130nm, the wall thickness is about 15nm, and the TiO2 nanotubes are uniformly and closely arranged on the surface of the titanium foil.

[0055] Place the obtained MnCo2O4 / TiO2 photoanode on a scanning electron microscope for testing. It can be seen from Figure 5 that flower-like MnCo2O4 grows at the orifice of the nanotubes, and the particle size is about 1.9μm.

[0056] The obtained MnCo2O4 / TiO2 photoanode was tested for its photocathodic protection performance, and the obtained TiO2 nanotubes were used as a control. The MnCo2O4 / TiO2 photoanode and the TiO2 nanotube array were used as photoanodes and placed in a photoreactor containing a mixed solution of 0.1 M Na2S and 0.2 M NaOH. 304 stainless steel was used as the photocathode and placed in a corrosion cell containing 3.5 wt% NaCl solution. The two electrolytic cells were connected through a proton exchange membrane, and a saturated calomel electrode was used as the reference electrode and placed in the corrosion cell for open-circuit potential measurement. From Figure 6 It can be seen that when the TiO2 nanotubes were coupled with 304 stainless steel in the light-on state, the potential rapidly decreased to a more negative position, gradually became stable and then reached an equilibrium state, and the potential at the equilibrium state could drop to about -450 mV; when the MnCo2O4 / TiO2 photoanode was coupled with 304 stainless steel, the potential could drop to about -503 mV. When the dark state was restored, the electrode potential of the stainless steel began to rise and returned to the original potential before illumination. At this time, the electrode potential of the 304 stainless steel was still lower than its self-corrosion potential. When illuminated again, the electrode potential of the stainless steel connected to the heterojunction photoanode rapidly dropped to about -503 mV again, indicating that the heterojunction photoanode had good stability.

[0057] The obtained MnCo2O4 / TiO2 photoanode and TiO2 nanotubes were respectively connected to the working electrode and placed in a photoreactor containing 0.1 M Na2S solution and 0.2 M NaOH solution. 304 stainless steel was grounded and placed in a corrosion cell containing 3.5 wt% NaCl solution for transient photocurrent density curve measurement. From Figure 7 It can be seen that under visible light illumination, the photocurrent density of all samples showed a positive shift, indicating that electrons flowed from the composite material to the surface of 304SS. The rapid decrease in the current density after the light was turned off was attributed to the rapid recombination of photo-generated electrons and holes. The stable value of the photocurrent generated by the MnCo2O4 / TiO2 photoanode could reach 14 μA / cm 2 , and the stable value of the photocurrent generated by the TiO2 nanotubes was only 3.4 μA / cm 2 ; indicating that the photo-generated carriers of the MnCo2O4 / TiO2 photoanode could be effectively separated compared with the TiO2 nanotubes, resulting in better light response, indicating that the cathodic protection effect of this photoanode was better.

[0058] Example 3

[0059] A preparation method of the MnCo2O4 / TiO2 photoanode, comprising the following steps:

[0060] (1) Pretreatment: Take a titanium foil with a specification of 40mm×10mm×0.1mm as the substrate, polish it in the polishing solution for 30 - 60s. The polishing solution is a mixed solution of 0.9g NH4F, 5ml H2O, 12ml HNO3 and 12ml H2O2. Then perform ultrasonic cleaning in deionized water and ethanol alternately for 5min.

[0061] (2) Preparation of TiO2 nanotubes: Weigh 1.114g NH4F and dissolve it in 30ml H2O, then add it to 200ml of ethylene glycol electrolyte. Use the Ti foil as the anode connected to the working electrode, and the Pt plate as the cathode connected to the counter electrode. Perform anodic oxidation on the titanium foil for 1h at a voltage of 60V. Then anneal it in a muffle furnace at 450℃ for 2h. Cool it to room temperature, and TiO2 nanotubes are formed on the Ti foil.

[0062] (3) Preparation of MnCo2O4 / TiO2 photoanode: Weigh 5mM manganese acetate and 10mM cobalt acetate and dissolve them in 40mL of ethylene glycol solution containing 0.5ml deionized water, and ultrasonicate for 30min to obtain a transparent solution. Then add 0.1095g of polyvinylpyrrolidone to the above transparent solution and ultrasonicate for 15min. Transfer the solution and TiO2 nanotubes to a reaction kettle, immerse the TiO2 nanotubes in the solution, react at 180℃ for 12h, then cool the solution to room temperature, wash the sample with ethanol and deionized water, and dry it at 80℃ for 12h. Subsequently, anneal the prepared precursor in air at 500℃ for 4h at a heating rate of 2℃ / min. Thus, a MnCo2O4 / TiO2 film is formed on the surface of the titanium foil as the photoanode.

[0063] Place the above - obtained TiO2 nanotubes on a scanning electron microscope for testing. The inner diameter of the TiO2 nanotubes is about 130nm, the wall thickness is about 15nm, and the TiO2 nanotubes are uniformly and closely arranged on the surface of the titanium foil.

[0064] Place the above - obtained MnCo2O4 / TiO2 photoanode on a scanning electron microscope for testing. It can be seen from Figure 8 that flower - shaped MnCo2O4 grows at the orifice of the nanotubes, and the particle size is about 2.3μm.

[0065] Perform the photocathodic protection performance test on the above - obtained MnCo2O4 / TiO2 photoanode, and use the above - obtained TiO2 nanotubes as a control. Use the MnCo2O4 / TiO2 photoanode and the TiO2 nanotube array as photoanodes, place them in a photolysis cell containing a mixed solution of 0.1M Na2S and 0.2M NaOH, use 304 stainless steel as the photocathode, place it in a corrosion cell containing 3.5wt% NaCl solution, connect the two electrolytic cells through a proton membrane, and use a saturated calomel electrode as the reference electrode, place it in the corrosion cell, and perform an open - circuit potential test. It can be seen fromFigure 9 It can be seen that when the TiO2 nanotubes are coupled with 304 stainless steel in the light-on state, the potential rapidly drops to a more negative position, gradually becomes stable and then reaches an equilibrium state, and the potential in the equilibrium state can drop to about -450 mV; when the MnCo2O4 / TiO2 photoanode is coupled with 304 stainless steel, the potential can drop to about -510 mV. When returning to the dark state, the electrode potential of the stainless steel starts to rise and returns to the original potential before illumination. At this time, the electrode potential of the 304 stainless steel is still lower than its self-corrosion potential. When illuminated again, the electrode potential of the stainless steel connected to the heterojunction photoanode rapidly drops to about -510 mV again, indicating that the heterojunction photoanode has good stability.

[0066] The obtained MnCo2O4 / TiO2 photoanode and TiO2 nanotubes were respectively connected to the working electrode and placed in a photolysis cell containing 0.1 M Na2S solution and 0.2 M NaOH solution, and the 304 stainless steel was grounded and placed in a corrosion cell containing 3.5 wt% NaCl solution to make a transient photocurrent density curve. Figure 10 It can be seen that under visible light illumination, the photocurrent density of all samples shows a positive shift, indicating that electrons flow from the composite material to the surface of 304SS. The rapid decrease in the current density after turning off the light is attributed to the rapid recombination of photo-generated electrons and holes. The stable value of the photocurrent generated by the MnCo2O4 / TiO2 photoanode can reach 30 μA / cm 2 , and the stable value of the photocurrent generated by the TiO2 nanotubes is only 3.4 μA / cm 2 ; indicating that the photo-generated carriers of the MnCo2O4 / TiO2 photoanode can be effectively separated compared with the TiO2 nanotubes, producing a better light response, indicating that the cathodic protection effect of this photoanode is better.

[0067] Therefore, as can be seen from the above embodiments, TiO2 nanotubes are grown on the surface of the titanium foil and flower-like manganese cobaltate is loaded on the surface of the TiO2 nanotubes to form a photoanode between titanium dioxide and manganese cobaltate. This heterojunction photoanode improves the absorption intensity of TiO2 in the visible light region and increases the utilization rate of sunlight; this photoanode inhibits the recombination of photo-generated carriers, further reduces the electrode potential of the metal, enhances the redox ability of the composite material, and improves the cathodic protection effect of TiO2; this photoanode has stable performance and is environmentally friendly; at the same time, according to the comparison of three concentrations of 1 mM MnCo2O4, 2 mM MnCo2O4 and 5 mM MnCo2O4, it can be seen that when the concentration is 5 mM, the potential drop is the lowest and the current value is the highest, which are -510 mV and 30 μA / cm 2 .

Claims

1. A preparation method of a flower-shaped manganese cobaltate modified titanium dioxide photoanode, characterized in that: MnCo₂O₄ nanosheets were loaded on the surface of TiO₂ nanotube arrays by hydrothermal method, and then calcined to form a flower-like manganese cobaltate modified titanium dioxide photoanode; The hydrothermal method and calcination include: (1) Manganese acetate with a manganese ion concentration of 1 - 10 mM and cobalt acetate with a cobalt ion concentration of 2 - 20 mM were weighed and mixed at a molar ratio of 1:2; (2) The above mixed powder was added to 30 - 40 mL of ethylene glycol containing 0.5 - 1 mL of deionized water; (3) Then 0.1 - 0.2 g of polyvinylpyrrolidone was added to the above solution and stirred evenly; (4) The mixed solution and the TiO₂ nanotube arrays were transferred to a reaction kettle, and the TiO₂ nanotube arrays were immersed in the mixed solution; heat treatment was carried out at 170 - 180 °C for 11 - 12 h, air-cooled to 23 - 25 °C, the samples were washed with ethanol and deionized water, dried at 70 - 80 °C for 10 - 12 h, and the prepared precursor was annealed in air at 450 - 500 °C for 3 - 4 h to obtain MnCo₂O₄ / TiO₂.

2. The preparation method of the flower-like manganese cobaltate modified titanium dioxide photoanode according to claim 1, characterized in that: (1) TiO₂ nanotube arrays were prepared on the pretreated Ti substrate by anodic oxidation method, (2) Flaky MnCo₂O₄ was loaded on the surface of TiO₂ nanotube arrays by hydrothermal method; (3) The hydrothermally treated composite material was calcined to form flower-like MnCo₂O₄ at the orifice of TiO₂ nanotube arrays.

3. The preparation method of the flower-shaped manganese cobaltate modified titanium dioxide photoanode according to claim 2, characterized in that: In the step (1), the TiO₂ nanotube arrays were prepared by anodic oxidation method to prepare TiO₂ nanotube arrays with an inner diameter of 120 - 150 nm and a tube wall thickness of 11 - 16 nm on the pretreated Ti substrate.

4. The flower-shaped manganese cobaltate modified titanium dioxide photoanode prepared by the method according to claim 1, characterized in that: The flower-like manganese cobaltate modified titanium dioxide photoanode MnCo₂O₄ / TiO₂ was prepared by the method according to claim 1, wherein the particle size of the loaded flower-like MnFe₂O₄ is 1.5 - 2.5 μm.

5. Application of the flower-like manganese cobaltate modified titanium dioxide photoanode according to claim 4, characterized in that: The application of the flower-like manganese cobaltate modified titanium dioxide photoanode MnCo₂O₄ / TiO₂ in preventing metal corrosion.

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