阅读说明：本技术 一种Ag/Ag3PO4/TiO2纳米复合膜材料及其应用 (Ag/Ag3PO4/TiO2Nanocomposite film material and application thereof ) 是由 王宁 王静 刘梦楠 段继周 侯保荣 戈成岳 张冉 舒向泉 贺永鹏 林建康 乔泽 于 2020-12-24 设计创作，主要内容包括：本发明涉及光生阴极保护技术,尤其是涉及一种采用浸渍-沉积法和光还原法制备的纳米复合膜材料(Ag/Ag-3PO-4/TiO-2复合膜光阳极)及其应用。采用浸渍-沉积法和光还原法在TiO-2纳米线表面复合Ag-3PO-4和Ag纳米粒子,制备Ag/Ag-3PO-4/TiO-2纳米复合膜光阳极材料。本发明复合膜作为光阳极材料进行阴极保护时,相比纯TiO-2材料而言,显著提高了TiO-2对可见光的利用率和光生电子-空穴对的分离率,不仅降低了304不锈钢的电极电位,也降低了腐蚀速率,有效提升了TiO-2对304不锈钢的光生阴极保护性能。(The invention relates to a photo-generated cathode protection technology, in particular to a nano composite film material (Ag/Ag) prepared by adopting a dipping-deposition method and a photo-reduction method 3 PO 4 /TiO 2 Composite membrane photoanode) and applications thereof. By dipping-deposition and photo-reduction on TiO 2 Nano wire surface composite Ag 3 PO 4 And Ag nanoparticles, preparation of Ag/Ag 3 PO 4 /TiO 2 A nano composite film photo-anode material. When the composite film is used as a photo-anode material for cathodic protection, compared with pure TiO 2 For materials, the TiO content is obviously improved 2 The utilization rate of visible light and the separation rate of photo-generated electron-hole pairs not only reduce the electrode potential of 304 stainless steel, but also reduce the corrosion rate, and effectively improve TiO 2 Photoproduction cathodic protection performance on 304 stainless steel.)

1. Ag/Ag₃PO₄/TiO₂The nano composite film material is characterized in that: by dipping-deposition and photo-reduction on TiO₂Nano wire surface composite Ag₃PO₄And Ag nanoparticles, preparation of Ag/Ag₃PO₄/TiO₂A nano composite film photo-anode material.

2. Ag/Ag according to claim 1₃PO₄/TiO₂The nano composite film material is characterized in that: the TiO is loaded by adopting an immersion-deposition method₂Sequentially dipping the titanium sheet of the nanowire in AgNO₃Solution and NaH₂PO₄Repeatedly dipping and depositing in the solution, drying to obtain Ag₃PO₄/TiO₂A nanocomposite; wherein, AgNO₃The concentration of the solution is 0.1-0.2M, NaH₂PO₄The concentration of the solution is 0.3-0.6M.

3. Ag/Ag according to claim 2₃PO₄/TiO₂The nano composite film material is characterized in that: the supported TiO₂Dipping the titanium sheet of the nanowire in AgNO₃Depositing in the solution for 30-60 min, and depositing TiO₂Impregnation of nanowires in NaH₂PO₄Depositing in the solution for 5-10 min; the dipping-deposition times are 2-8 times, drying is carried out for 0.5-1 h at the temperature of 60-100 ℃, and natural cooling is carried out, thus obtaining the Ag₃PO₄/TiO₂A nanocomposite material.

4. Ag/Ag according to claim 1 or 2₃PO₄/TiO₂The nano composite film material is characterized in that: irradiating Ag nanoparticles by ultraviolet light for 0.5-1 h by a photoreduction method to modify the Ag nanoparticles₃PO₄/TiO₂A nanocomposite surface.

5. Ag/Ag according to claim 1₃PO₄/TiO₂The nano composite film material is characterized in that: the TiO is₂The nanowire is prepared by a one-step anodic oxidation method, a traditional double-electrode system is adopted, a titanium sheet is used as a working electrode, a platinum electrode is used as a counter electrode, the counter electrode is clamped by an electrode clamp and then placed in 2-3M NaOH solution, and TiO is obtained on a titanium sheet substrate by the one-step anodic oxidation method₂A nanowire.

6. Ag/Ag according to claim 1₃PO₄/TiO₂The application of the nano composite film photo-anode material is characterized in that: the Ag/Ag₃PO₄/TiO₂The nano composite film is used as a photo-anode material and is applied to photo-generated cathodic protection.

7. Ag/Ag according to claim 1₃PO₄/TiO₂The application of the nano composite film photo-anode material is characterized in that: the Ag/Ag₃PO₄/TiO₂The nano composite film material is applied to inhibiting metal corrosion as an anti-corrosion protective film.

Technical Field

The invention relates to a photo-generated cathode protection technology, in particular to a nano composite film material (Ag/Ag) prepared by adopting a dipping-deposition method and a photo-reduction method₃PO₄/TiO₂Composite membrane photoanode) and applications thereof.

Background

The problem of material corrosion is a major global challenge, of which the most serious is marine corrosion. Due to the complexity of the marine environment, high salt concentration, high chloride ion content, high oxygen content, a large amount of microorganisms in the marine environment and the influence of sea waves and strong light, the electrochemical corrosion of the marine steel structure is particularly serious, serious damage is generated, unexpected disasters and accidents can be caused, the environmental pollution is caused, the life and property safety of people is endangered, and even more, the national safety can be threatened. In marine and oceanographic engineering, stainless steel is widely used, and the corrosion resistance of stainless steel in the marine environment is far lower than that of the atmospheric environment. Researches find that compared with the traditional steel structure anticorrosion means, the novel photoelectrochemistry cathodic protection technology has the advantages of strong operability, high cleanliness, no energy consumption in material protection and the like in the aspect of material anticorrosion, and is more beneficial to the development of navigation industry.

The photo-generated cathodic protection method is a novel cathodic protection technology, can utilize the electrons produced by photo-excited semiconductor to attain the goal of metal protection, and the electrons produced by photo-excitation on the photo-anode semiconductor material can be transferred onto the metal connected with it, so that the open-circuit potential value of the metal is more negative than its corrosion potential, and the electrons can be collected on the surface of the protected metal so as to inhibit metal corrosion. The process only needs sunlight green energy, does not need to consume other energy, and does not produce environmental pollution emission.

The application of semiconductor materials in the field of photo-generated cathode protection needs to meet certain conditions. Firstly, the conduction band potential of the semiconductor must be lower than the self-etching potential in the same solution; secondly, the forbidden bandwidth of the semiconductor material cannot be too wide; third, the photocarrier pairs of the semiconductor are easy to separate and have low recombination rates. TiO 2₂The material has high photoelectric conversion efficiency, stable chemical performance, no toxicity and harmlessness, and is widely applied to the field of photo-generated cathodic protection. However, TiO₂Has a wide band gap (3.2eV), and the photoelectrochemical performance of the material is limited to an ultraviolet region, but at the same time, the high recombination rate of photogenerated electrons and holes leads to low current density and low photoelectric conversion efficiency, so that the application range of the material is greatly limited, and under the dark condition, TiO has a wide range₂It cannot generate photo-generated electrons and provide photoelectrochemical cathodic protection for metals. Therefore, finding a material with a narrow band gap to compound with it is to enhance TiO₂The important research direction of photoelectric conversion performance.

Disclosure of Invention

The invention aims to provide Ag/Ag prepared by dipping-deposition and photoreduction₃PO₄/TiO₂A nano composite film photo-anode material and application thereof.

In order to achieve the purpose, the invention adopts the technical scheme that:

Ag/Ag₃PO₄/TiO₂The nano composite film material is prepared by adopting a dipping-deposition method and a photoreduction method on TiO₂Nano wire surface composite Ag₃PO₄And Ag nanoparticles, preparation of Ag/Ag₃PO₄/TiO₂A nano composite film photo-anode material.

The TiO is loaded by adopting an immersion-deposition method₂Sequentially dipping the titanium sheet of the nanowire in AgNO₃Solution and NaH₂PO₄Repeatedly dipping and depositing in the solution, drying to obtain Ag₃PO₄/TiO₂A nanocomposite; wherein, AgNO₃The concentration of the solution is 0.1-0.2M, NaH₂PO₄The concentration of the solution is 0.3-0.6M.

The supported TiO₂Dipping the titanium sheet of the nanowire in AgNO₃Depositing in the solution for 30-60 min, and depositing TiO₂Impregnation of nanowires in NaH₂PO₄Depositing in the solution for 5-10 min; repeatedly dipping and depositing for 2-8 times, drying at 60-100 ℃ for 0.5-1 h, and naturally cooling to obtain the Ag₃PO₄/TiO₂A nanocomposite material.

Irradiating Ag nanoparticles by ultraviolet light for 0.5-1 h by a photoreduction method to modify the Ag nanoparticles₃PO₄/TiO₂A nanocomposite surface.

Further, the following steps are carried out:

(1) 0.1-0.2M AgNO₃Solution and 0.3-0.6M NaH₂PO₄The solutions were poured into two 10mL beakers, respectively, after which the supported TiO was placed₂The titanium sheet of the nanowire is obliquely placed in the AgNO₃Soaking the titanium plate in a beaker of the solution for 30-60 min, clamping the upper end of the titanium plate by using a pair of tweezers, slightly clamping the titanium plate, obliquely suspending the titanium plate, and allowing the redundant liquid to flow into a waste liquid cylinder; then put the titanium sheet into the container with NaH₂PO₄Soaking the titanium sheet in a beaker of the solution for 5-10 min, taking out the titanium sheet by using tweezers in the same way, and washing the titanium sheet by using deionized water for later use;

(2) placing the circulated titanium sheet into a porcelain boat, setting the temperature in an oven at 60-100 ℃, drying for 0.5-1 h, and naturally cooling to obtain the Ag₃PO₄/TiO₂A nanocomposite material.

Ag nano particles are loaded on Ag by adopting a photo-reduction method₃PO₄/TiO₂The surface of the nano composite film is prepared by mixing Ag₃PO₄/TiO₂The nano composite materials are respectively placed in 0.01-0.2 MAGNO₃In the solution, irradiating the solution for 0.5 to 1 hour by using ultraviolet light, taking out a sample, washing the surface of the sample by using deionized water, and naturally drying the sample to obtain the Ag/Ag₃PO₄/TiO₂A nanocomposite film.

The TiO is₂The nanowire is prepared by a one-step anodic oxidation method, a traditional double-electrode system is adopted, a titanium sheet is used as a working electrode, a platinum electrode is used as a counter electrode, the counter electrode is clamped by an electrode clamp and then placed in 2-3M NaOH solution, and TiO is obtained on a titanium sheet substrate by the one-step anodic oxidation method₂A nanowire.

Rapid preparation of TiO on the surface of a titanium sheet by a one-step anodic oxidation method₂The one-step anodic oxidation method comprises the steps of providing 1.3-2.5A direct current by a direct current power supply, anodizing for 180-240 min under the condition that the temperature of a solution is kept at 80-100 ℃, taking out a titanium sheet, sequentially cleaning with acetone, absolute ethyl alcohol and distilled water, naturally airing, placing the titanium sheet into a muffle furnace at the temperature of 450-600 ℃, calcining for 120-180 min, and naturally cooling to obtain TiO₂A nanowire.

Ag/Ag₃PO₄/TiO₂Application of nano composite film photo-anode material, Ag/Ag₃PO₄/TiO₂The nano composite film is used as a photo-anode material and is applied to photo-generated cathodic protection.

Ag/Ag₃PO₄/TiO₂Application of nano composite film photo-anode material, Ag/Ag₃PO₄/TiO₂The nano composite film material is applied to inhibiting metal corrosion as an anti-corrosion protective film.

For the Ag/Ag prepared above₃PO₄/TiO₂The nano composite film photo-anode material is used for carrying out photoelectric performance and photoelectrochemical cathode protection tests, and a double electrolytic cell system consisting of a photo electrolytic cell and a corrosion electrolytic cell is adopted. 304 stainless steel and prepared Ag/Ag₃PO₄/TiO₂The nano composite material is respectively placed in the corrosion pool and the photo-anode pool. 3.5 wt% NaCl solution was placed in the corrosion cell, and 0.25M Na was placed in the photoelectrolysis cell₂SO₃As a hole trap, the naphthol film separates the electrolytes in the two cells and forms a closed loop. The reference electrode used in the experiment is a saturated calomel electrode, the electrochemical workstation is a P4000+, USA, PLS-SXE300C xenon lamp is used as a light source, and a 420 cut-off sheet is arranged at the outlet of the light source to obtain visible lightAnd (5) irradiating to the surface of the anode. And (3) testing open circuit potential: before the experiment, a 304 stainless steel electrode is placed in 3.5 wt% NaCl solution to be soaked for 2 hours to reach an electrochemical stable state, the 304 stainless steel electrode is connected with a photoanode through a lead and then connected to a working electrode clamp of an electrochemical workstation, a saturated calomel electrode is connected with a reference electrode clamp, and the potential change of the 304 stainless steel relative to the saturated calomel electrode is observed by switching on and off light. Testing the photocurrent density: placing an ammeter with zero resistance on the surfaces of the photo-anode and the 304 stainless steel, short-circuiting the reference electrode and the counter electrode, testing the real current density of the reference electrode and the counter electrode under a non-polarized condition, connecting the 304 stainless steel electrode to the ground wire position of an electrochemical workstation, connecting the photo-anode with a working electrode clamp, and observing the change of the photo-current density on the surface of the 304 stainless steel by switching on and off light.

For the Ag/Ag prepared above₃PO₄/TiO₂And carrying out an ultraviolet-visible diffuse reflection test on the nano composite film photo-anode material to obtain an ultraviolet-visible diffuse reflection spectrum.

The basic principle of the invention is as follows:

Ag₃PO₄is a narrow forbidden band width semiconductor material, has a forbidden band width of 2.4eV, has high utilization rate of visible light, and is a composite TiO₂The ideal material of the material. It is compounded to TiO₂The surface of the nano wire can effectively reduce pure TiO₂The forbidden band width of the film can enlarge the response range to visible light, increase the utilization rate of light and effectively improve the separation rate of photo-generated electrons and holes. The deposition of noble metal Ag can not only improve TiO due to its surface Schottky effect₂The utilization rate of light can also effectively reduce the recombination rate of photo-generated electrons and holes, improve the photoelectric conversion capability and effectively improve the photo-generated cathode protection performance of the nano composite material.

Firstly, Ag is processed by adopting a dipping-deposition method₃PO₄Compounding of nanoparticles to TiO₂The Ag nano particles are compounded on the surface of the nano material by adopting a photo-reduction method, so that the TiO is greatly enhanced₂The cathode protection effect on 304 stainless steel. When light irradiates Ag/Ag₃PO₄/TiO₂When the surface of the nano composite material is coated, the surface is coated with the coating material Ag nano particles have surface plasma resonance effect and can rapidly generate photo-generated electrons, TiO₂And Ag₃PO₄The photo-generated electrons rapidly transit from the valence band to the conduction band position due to the excitation of light. The Ag surface has a lower Schottky barrier and the conduction band potential is negative to Ag₃PO₄The potential of the conduction band is increased, so that electrons on the conduction band of the Ag nano-particles can rapidly transit to Ag₃PO₄On the guide belt; in the same way, Ag₃PO₄The potential of the conduction band is negative to TiO₂Conduction band potential, so Ag₃PO₄And electrons on Ag conduction band are rapidly enriched to TiO₂On the conduction band of (a), the photogenerated electrons finally pass through the regular TiO₂The nanowires reach the surface of the 304 stainless steel, and enriched electrons participate in the cathode oxygen reduction process of the 304 stainless steel, so that the cathode reaction is reduced, the 304 stainless steel anode dissolution reaction is simultaneously inhibited, and the purpose of protecting the 304 stainless steel cathode is achieved. In the presence of Na in the reaction system₂SO₃Hole traps, Ag₃PO₄Nanoparticles and TiO₂The holes generated in the valence band can rapidly form polysulfides with the hole traps. Due to the existence of the hole trapping agent, the probability of recombination of photogenerated electrons and holes is reduced, the capability of generating electrons by the nano composite material is further improved, and good cathodic protection can be provided for 304 stainless steel coupled with the nano composite material. Thus, Ag/Ag under visible light irradiation₃PO₄/TiO₂The photo-anode effectively reduces the corrosion rate of 304 stainless steel and shows good photo-cathode protection effect, namely through Ag and Ag₃PO₄With TiO₂The formed nano composite film can effectively improve the photoproduction cathode protection effect of the film on metal.

The invention has the advantages that:

in the invention, Ag is mixed with₃PO₄And Ag nanoparticles with TiO₂Nanowire recombination enlarges TiO₂The response range to light effectively improves the utilization rate of sunlight, reduces the recombination rate of photo-generated electrons and holes, reduces the electrode potential of metal, and obviously improves TiO₂To the cathode of 304 stainless steelThe effect of extreme protection. The method specifically comprises the following steps:

1. the Ag/Ag of the invention₃PO₄/TiO₂The nano composite film photo-anode material passes through a narrow forbidden band width Ag₃PO₄The compounding of nano particles reduces TiO₂The surface energy barrier improves the utilization efficiency of light; ultraviolet-visible diffuse reflection shows that the absorption range of the nanocomposite material to light extends from the ultraviolet region to the visible region; deposition of Ag nanoparticles improves Ag₃PO₄The optical stability of (1).

2. The Ag/Ag of the invention₃PO₄/TiO₂Nano composite film photo-anode material, Ag₃PO₄Immersion-deposition times 6 times, AgNO₃Compared with a saturated calomel electrode, the nano composite material prepared when the photo-reduction concentration is 0.1M has the protection potential reaching-900 mV and the protection current reaching 130 muA/cm²This condition provides the best cathodic protection for the 304 stainless steel to which it is coupled.

X-ray photoelectron spectroscopy test proves that the composite Ag₃PO₄And Ag nano particles have high purity and no other impurities are introduced. After the silver phosphate and silver nano particles are compounded on the surface of the titanium dioxide nano wire, the optical absorption performance of the nano wire is obviously enhanced, the absorption range of light is expanded from an ultraviolet region to a visible region, and the utilization rate of the light is improved. In conclusion, the Ag/Ag prepared by adopting the dipping-deposition method and the photoreduction method₃PO₄/TiO₂When the nano composite film is used as a photo-anode, the TiO is greatly improved₂The cathode protection effect on 304 stainless steel is an excellent anticorrosion protection material.

Drawings

FIG. 1 is a schematic diagram of Ag/Ag preparation according to example 1 of the present invention₃PO₄/TiO₂Schematic process of nanocomposite.

Fig. 2 is a schematic diagram of an experimental apparatus for testing a change in a photoelectric potential in embodiment 1 of the present invention.

Fig. 3 is a schematic view of an experimental apparatus for testing the photo-induced current density in embodiment 1 of the present invention.

FIG. 4 shows an embodiment of the present inventionExample 1 provides Ag under visible light irradiation and dark conditions₃PO₄304 stainless steel coupling Ag with different dipping-deposition times₃PO₄/TiO₂Nanocomposite film (a) and AgNO₃304 stainless steel coupling Ag/Ag with different concentrations₃PO₄/TiO₂Open circuit potential change pattern of the nanocomposite film (b). Wherein the abscissa is time(s), the ordinate is electrode potential (V vs. sce), on indicates turning on the power supply, and off indicates turning off the light source.

FIG. 5 shows Ag in the dark state under irradiation of visible light according to example 1 of the present invention₃PO₄304 stainless steel coupling Ag with different dipping-deposition times₃PO₄/TiO₂Nanocomposite film (a) and AgNO₃304 stainless steel coupling Ag/Ag with different concentrations₃PO₄/TiO₂Graph of photocurrent density change of the nanocomposite film (b). Wherein the abscissa is time(s) and the ordinate is current density (. mu.A/cm)²) On means power on and off means light off.

FIG. 6 shows pure TiO provided in example 1 of the present invention₂Nanowire, composite Ag under optimum conditions₃PO₄Ag nanoparticles Scanning Electron Microscopy (SEM), in which pure TiO was used₂Nanowires (a, b), Ag₃PO₄Ag prepared when dipping-depositing times are 6 times₃PO₄/TiO₂Nanocomposite (c, d), Ag₃PO₄Immersion-deposition times of 6 times, AgNO₃Ag/Ag prepared at a concentration of 0.1M₃PO₄/TiO₂Nanocomposite (e, f).

FIG. 7 shows Ag in example 1 of the present invention₃PO₄Immersion-deposition times of 6 times, AgNO₃Ag/Ag prepared at a concentration of 0.1M₃PO₄/TiO₂The nanocomposite material has a distribution of Ti (b), O (c), P (d), and Ag (e) elements on the surface.

FIG. 8 shows Ag as provided in example 1 of the present invention₃PO₄Immersion-deposition times of 6 times, AgNO₃Ag/Ag prepared at a concentration of 0.1M₃PO₄/TiO₂Of nanocompositesAn X-ray photoelectron spectrum (a) and high resolution spectrograms of Ti2P (b), O1s (c), P2P (d) and Ag3d (e).

FIG. 9 shows the prepared TiO provided in example 1 of the present invention₂Nanowire (Curve a), Ag prepared under optimal conditions₃PO₄/TiO₂Nanocomposite (Curve b), Ag/Ag₃PO₄/TiO₂Uv-visible diffuse reflectance pattern of the nanocomposite (curve c).

FIG. 10 shows Ag/Ag provided in example 1 of the present invention₃PO₄/TiO₂A photoelectrochemical corrosion resistance mechanism diagram of the nano composite material under the irradiation of visible light.

Detailed Description

The invention is further illustrated with reference to the following examples and figures, without thereby restricting the content of the invention.

The composite film structure of the invention is Ag₃PO₄And Ag nanoparticles deposited on TiO₂On the surface of the nano-wire, obtaining Ag/Ag₃PO₄/TiO₂Nano composite film photo-anode material to make TiO₂The absorption range of light is expanded from ultraviolet region to visible region, and when the material is used as photoanode material for cathodic protection, the material is compared with TiO₂In terms of materials, the separation rate of photo-generated electrons and holes is greatly improved, the photoelectric conversion capability is enhanced, the utilization rate of sunlight is effectively improved, the electrode potential of 304 stainless steel is obviously reduced, the corrosion rate is reduced, and the photo-generated cathode protection effect is enhanced.

Furthermore, the invention uses Ag₃PO₄Narrow band gap, surface Schottky effect of Ag nano particle and photogenerated carrier in TiO₂The characteristic of fast transmission in the nanotube is combined, so that not only TiO is expanded₂The response range to light effectively improves the utilization rate of sunlight, obviously reduces the recombination rate of photo-generated electrons and holes, reduces the electrode potential of metal, and obviously improves TiO₂The cathode protection effect on 304 stainless steel can be used in the field of cathode protection of metal materials.

Example 1

Ag/Ag₃PO₄/TiO₂The preparation of the nano composite film photo-anode material (see figure 1) comprises the following steps:

pretreatment of a titanium substrate: firstly, cutting a titanium sheet with the purity of 99.9 percent and the thickness of 0.1mm into the size of 30mm multiplied by 10mm, and then polishing each surface for 100 times by 2500-mesh sand paper to be used as a growth substrate of the composite film; secondly, ultrasonically cleaning the sample by using acetone, absolute ethyl alcohol and distilled water in sequence for 10min, 10min and 30min respectively, and drying for later use; thirdly, the titanium sheet is put into the mixed solution (the volume ratio is NaOH: Na) at the temperature of 85 DEG C₂CO₃:H₂Soaking in O-5: 2:100) for 90min, taking out, and cleaning with distilled water; finally, in HF solution (volume ratio of HF: H)₂Etching for 1min in the ratio of O to 1:5), taking out, sequentially cleaning with acetone, absolute ethyl alcohol and distilled water, and drying for later use.

TiO₂Preparing the nano wire: rapid preparation of TiO on the surface of a titanium sheet by a one-step anodic oxidation method₂A nanowire. The anode oxidation adopts a traditional double-electrode system, a titanium sheet is used as an anode, and a platinum electrode is used as a counter electrode. Firstly, a titanium sheet is clamped by an electrode clamp and put into 400mL of 2M NaOH solution, the current of a direct current power supply is regulated to be stabilized at about 1.3A, the temperature of the solution is kept at 80 ℃, the anode is oxidized for 180min, then the titanium sheet is taken out, washed by acetone, absolute ethyl alcohol and distilled water in sequence, naturally dried for later use, finally put into a muffle furnace, the temperature is set to be 450 ℃, calcined for 120min, taken out and put into a dust-free dryer for later use, and TiO can be obtained on the surface of the titanium sheet₂A nanowire.

Ag₃PO₄/TiO₂Preparing a nano composite film: first, 0.1M AgNO was mixed₃Solution and 0.3M NaH₂PO₄The solutions were poured into two 10mL beakers, respectively, after which the supported TiO was placed₂The titanium sheet of the nanowire is obliquely placed in the AgNO₃Soaking the titanium plate in the solution beaker for 30min, clamping the upper end of the titanium plate by using a pair of tweezers, slightly clamping the titanium plate, and obliquely suspending the titanium plate to allow the redundant liquid to flow into a waste liquid cylinder; secondly, put the titanium sheet into the container with NaH₂PO₄Soaking in the solution beaker for 5min, and soaking with tweezersThe titanium sheet was taken out and washed with deionized water, which was a cycle, and the above experiment was repeated at different dipping-deposition cycle times, which were set to 2, 4, 6 and 8 times; finally, the titanium sheet after circulation is put into a porcelain boat, the temperature in an oven is set to be 60 ℃, the drying is carried out for 1 hour, and the natural cooling is carried out, thus obtaining the Ag prepared under different dipping-deposition cycle times₃PO₄/TiO₂A nanocomposite material.

Ag prepared under different dipping-deposition cycle times₃PO₄/TiO₂The nano composite material is subjected to performance characterization, and the result shows that the Ag is obtained when₃PO₄When the dipping-deposition times is 6 times, the obtained Ag₃PO₄/TiO₂The nano composite material has the best effect on the cathode protection of 304 stainless steel; then in Ag₃PO₄The next operation was carried out under the condition that the number of dipping-depositing times was 6.

Ag/Ag₃PO₄/TiO₂Preparing a nano composite film: ag nano particles are loaded on Ag by adopting a photo-reduction method₃PO₄/TiO₂The surface of the nano composite film is to be Ag₃PO₄Ag prepared when the number of medium immersion-deposition times is 6₃PO₄/TiO₂Placing the nano composite material in AgNO with different concentrations₃In solution, AgNO₃The concentration of the solution was set to 0.01M, 0.05M, 0.1M and 0.2M. Irradiating with ultraviolet light for 30min, taking out sample, washing with deionized water, and naturally air drying to obtain different AgNO₃Ag/Ag prepared at concentration₃PO₄/TiO₂A nanocomposite film.

For different AgNO₃Ag/Ag prepared at concentration₃PO₄/TiO₂The performance of the nano composite film is characterized, and the result shows that when AgNO is used₃Ag/Ag prepared at a solution concentration of 0.1M₃PO₄/TiO₂The nanocomposite can provide the best cathodic protection for 304 stainless steel coupled thereto; then in AgNO₃The next operation was carried out at a concentration of 0.1M.

For Ag/Ag₃PO₄/TiO₂And (3) characterizing the nano composite film: for Ag/Ag₃PO₄/TiO₂Characterization of the nanocomposite films mainly includes field emission scanning electron microscopy (FSEM), energy spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis). Wherein, the field emission scanning electron microscope adopts NOVANANOSE EM 450 produced by FEI company of America, the accelerating voltage is 1kV, the spot size is 2.0, a CBS probe is selected, and secondary electrons and back scattering electrons are received to analyze the appearance; the energy spectrum adopts OxFORD X-MaxN50 produced by Oxford instruments science and technology Limited, the accelerating voltage is 15kV, the spot size is 3.0, and qualitative and quantitative analysis is carried out by characterizing characteristic X rays; the X-ray photoelectron spectrum adopts ESCALB 250Xi produced by Thermo Fisher Scientific company in America, the analysis adopts contaminated carbon (-284.8 eV) as sample binding energy to charge correction, the excitation power is 150W, the excitation source is monochromatic Al K alpha (1486.6eV), a fixed energy-passing mode is adopted, the full-scanning range is 0-1600eV, the energy-passing is 50eV, the step width is 1.0eV, the narrow scanning energy-passing is 20eV, and the step width is 0.05 eV; UV-visible diffuse reflectance Cary 5000, manufactured by Varian, USA, as BaSO₄As background, the scan range is 10 ° -80 ° (see fig. 3, 4, 5, 6).

For Ag/Ag₃PO₄/TiO₂And (3) carrying out photoelectric performance test on the nano composite film:

pretreatment of 304 stainless steel: the 304 stainless steel used for the experiment had a composition (wt.%) of 0.08C, 1.86Mn, 0.72Si, 0.035P, 0.029S, 18.25Cr, 8.5Ni, and the remainder was Fe. 304 stainless steel of 10mm × 10mm × 10mm was cut out and sealed in epoxy resin, and the working surface of the electrode was 10mm × 10 mm. And (3) polishing the surface of the substrate by using 2400-mesh silicon carbide abrasive paper until the surface is smooth, cleaning the surface by using absolute ethyl alcohol, then carrying out ultrasonic treatment in water for 5min, and putting the substrate into a drying dish for later use.

Open circuit potential and photocurrent density testing: 304 stainless steel and prepared Ag/Ag₃PO₄/TiO₂The nano composite material is respectively placed in the corrosion pool and the photo-anode pool. 3.5 wt% NaCl solution was placed in the corrosion cell, and 0.25M Na was placed in the photoelectrolysis cell₂SO₃As a hole trapping agent, a naphthol film separates the electrolysis in two cellsThe liquids separate and form a closed loop. The reference electrode used in the experiment was a saturated calomel electrode, the electrochemical workstation was a P4000+, USA, PLS-SXE300C xenon lamp as the light source, and a 420 cut-off sheet was placed at the exit of the light source to capture visible light to the anode surface. Open circuit potential test (see fig. 2): before the experiment, a 304 stainless steel electrode is placed in 3.5 wt% NaCl solution to be soaked for 2 hours to reach an electrochemical stable state, the 304 stainless steel electrode is connected with a photoanode through a lead and then connected to a working electrode clamp of an electrochemical workstation, a saturated calomel electrode is connected with a reference electrode clamp, and the potential change of the 304 stainless steel relative to the saturated calomel electrode is observed by switching on and off light. Photocurrent density test (see fig. 3): and placing an ammeter with zero resistance on the surfaces of the photo-anode and the 304 stainless steel, short-circuiting the reference electrode and the counter electrode, and testing the real current density of the reference electrode and the counter electrode under the electrodeless condition. Then the 304 stainless steel electrode is connected to the ground wire position of the electrochemical workstation, the photo anode is connected with the working electrode clamp, and the change of the photocurrent density on the 304 stainless steel surface is observed by switching on and off light.

For Ag/Ag in example 1₃PO₄/TiO₂The cathodic protection performance of the nanocomposites was analyzed and fig. 4 shows a graph of the open circuit potential change of 304 stainless steel coupled nanocomposites under visible illumination and dark conditions. Wherein, the diagram (a) shows Ag₃PO₄The influence of the dip-deposition times on the open circuit potential, and the graph (b) shows AgNO during photoreduction₃Influence of concentration on open circuit potential. As can be seen from the graph (a), Ag is observed at the moment of opening₃PO₄/TiO₂The open circuit potential of the 304 stainless steel to which the nanocomposite was coupled was significantly reduced, indicating that Ag₃PO₄Is compounded to improve TiO₂The cathodic protection effect of (1). However, in the on-state, Ag₃PO₄The potential of 304 stainless steel coupled thereto is in an unstable state, which may be in contact with Ag₃PO₄Is easily decomposed by light. When Ag is present₃PO₄When the dipping-deposition times are 6 times, the potential of the saturated calomel electrode reaches-550 mV, and the open-circuit potential is obviously more negative than other deposition times, so that the dipping-deposition times are shownIs Ag obtained at 6 times₃PO₄/TiO₂The nanocomposite can provide the best cathodic protection for 304 stainless steel coupled thereto. As can be seen from the graph (b), Ag/Ag is observed at the moment of opening₃PO₄/TiO₂The open circuit potential of the nano composite material is obviously reduced, and after Ag nano particles are deposited on the surface, the open circuit potential is obviously higher than that of pure TiO₂Nanowire, Ag₃PO₄/TiO₂The potential of the nano composite material is more negative, and the deposition of Ag nano particles obviously improves TiO₂The cathodic protection effect of (1). In the light-on stage, the potential is maintained in a relatively stable state, which shows that the deposition of Ag nano particles improves Ag₃PO₄The optical stability of (1). At the moment of keeping out of the sun, the open circuit potential rises rapidly, but the potential is obviously lower than the open circuit potential of 304 stainless steel, and compared with a saturated calomel electrode, the maximum open circuit potential can reach minus 680mV and is obviously lower than the open circuit potential of 304 stainless steel (-180mV), which shows that under the dark state condition, the composite material has the energy storage function and can provide cathode protection of nearly 500mV for 304 stainless steel. Panel (b) shows AgNO at the same time₃Influence of concentration on the open-Circuit potential when AgNO₃At a concentration of 0.1M, the potential reached-900 mV relative to the saturated calomel electrode, from which it can be seen that AgNO when used in the presence of a solution of₃Ag/Ag obtained at a concentration of 0.1M₃PO₄/TiO₂The nanocomposite can provide the best cathodic protection for 304 stainless steel coupled thereto. TiO with increasing number of deposition cycles₂Nanowire surface Ag₃PO_{4 of}The deposition amount is gradually increased, and when visible light irradiates the surface of the composite material, more Ag is available₃PO₄The more the active sites are excited, the more the photo-potential drop; however, when excessive Ag is deposited on the surface₃PO₄Nano-particle, excited Ag₃PO₄But rather, decrease, adversely affecting light absorption. After Ag particles are compounded, electrons generated by light excitation can be rapidly transferred to the surface of 304 stainless steel due to the plasma resonance effect generated on the surface of the Ag particles, so that a very good cathode protection effect is achieved; however, when too many Ag particles are deposited on the surface, a combination of photogenerated electrons and holes is generatedAnd the sites, thereby reducing the photoproduction cathodic protection effect of the nanocomposite. In summary, when Ag is used₃PO₄Immersion-deposition times of 6 times, AgNO₃At a concentration of 0.1M, Ag/Ag₃PO₄/TiO₂The nanocomposite can provide the best cathodic protection for 304 stainless steel coupled thereto.

For Ag/Ag in example 1₃PO₄/TiO₂The cathodic protection performance of the nanocomposite was analyzed, and fig. 5 shows a graph of the change in photocurrent density between 304 stainless steel and the nanocomposite under visible light irradiation and dark state conditions, wherein the graph (a) shows Ag₃PO₄The influence of the number of dip-depositions on the photocurrent density, graph (b) shows AgNO during photoreduction₃The effect of concentration on photocurrent density. As can be seen from the graph (a), Ag is observed at the moment of opening₃PO₄/TiO₂The photocurrent density of the nanocomposite rose rapidly and was positive, indicating that electrons flowed from the nanocomposite through the electrochemical workstation to the surface of 304 stainless steel. In the composite Ag₃PO₄The photocurrent density was then compared to pure TiO₂The nanowires are significantly larger. FIG. (a) shows Ag at the same time₃PO₄Influence of silver impregnation-deposition times on photocurrent density when Ag₃PO₄When the dipping-deposition times are 6 times, the photocurrent density reaches 70 mu A/cm²Is pure TiO with obviously higher deposition times than other deposition times₂Nanowire generated photocurrent density (32 muA/cm)²) 2.2 times of the open circuit potential, which is in full agreement with the test results for open circuit potential. As can be seen from the graph (b), Ag/Ag is observed at the moment of opening₃PO₄/TiO₂The photocurrent density between the nanocomposite and 304 stainless steel is significantly higher than that of pure TiO₂And Ag₃PO₄/TiO₂A nanocomposite material. When AgNO₃At a concentration of 0.1M, the photocurrent density reached 130. mu.A/cm²Is TiO₂Nanowire generated photocurrent density (32 muA/cm)²) 4 times of the total weight of the product. In summary, when Ag is used₃PO₄Immersion-deposition times of 6 times, AgNO₃At a concentration of 0.1M, Ag/Ag₃PO₄/TiO₂The photocurrent density between the nano composite material and 304 stainless steel reaches 130 mu A/cm²The potential reached-900 mV relative to the saturated calomel electrode, which provides the best cathodic protection for 304 stainless steel coupled thereto.

For Ag/Ag in example 1₃PO₄/TiO₂The surface topography of the nanocomposite was analyzed and FIG. 6 shows pure TiO₂Nanowire, composite Ag under optimum conditions₃PO₄And scanning electron microscope images of the Ag nanoparticles. The diagrams (a) and (b) show pure TiO prepared by one-step anodic oxidation₂Nanowire, visible TiO₂The nanowire structures are mutually closed, and the pore diameters are uniform; in the diagrams (c) and (d), Ag₃PO₄Ag with 6 dipping-depositing times₃PO₄/TiO₂The electron micrograph shows that Ag is₃PO₄By complexing to TiO₂The surface, but relatively not very homogeneous, is observed by differences in deposition on electron micrographs, where the TiO still appears on the larger scale₂Closed pores of the nanowires; the graphs (e) and (f) are AgNO₃Complexing to Ag at a concentration of 0.1M₃PO₄/TiO₂Comparing the electron microscope images of the nano composite material with the images (c) and (d), the Ag nano particles are obviously deposited on the surface of the composite material, the distribution of the particles is relatively uniform, and the diameter is about 10 nm. In conclusion, Ag₃PO₄Ag nano particles are successfully compounded to TiO₂In a nanowire structure.

For Ag/Ag in example 1₃PO₄/TiO₂The surface morphology of the nanocomposite was analyzed and FIG. 7 shows Ag₃PO₄Immersion-deposition times of 6 times, AgNO₃The concentration is 0.1M to obtain Ag/Ag₃PO₄/TiO₂Elemental areal distribution profile of the nanocomposite. As can be seen from the element surface distribution, the existence of Ti, O, P and Ag elements is detected by the energy spectrum; from the content point of view, the elements Ti and O are present in the largest amounts, P and Ag are present in approximately the same amounts, but the contents are significantly lower than the Ti and O contents, and the surface distribution of P and Ag elements is not very uniform, which can be concluded that Ag₃PO₄And Ag nano particles are not uniformly compounded on the surface.

For Ag/Ag in example 1₃PO₄/TiO₂The surface state of the nanocomposite was analyzed, and FIG. 8 shows that when Ag is used₃PO₄6 times of dipping-deposition, AgNO₃The Ag/Ag is obtained at a concentration of 0.1M₃PO₄/TiO₂X-ray photoelectron spectrum of the nanocomposite. Wherein, the graph (a) is a full spectrum, and the rest is a high resolution spectrum of elements. As can be seen from the full spectrogram of the graph (a), the nano composite material detects absorption peaks of Ti, O, P and Ag elements, and proves that the four elements exist, and the detection result is consistent with the energy spectrum detection. Wherein the excess peak is carbon as a sample binding energy charge correction; FIG. b is a high resolution energy spectrum of Ti, the absorption peaks of 2p orbitals of Ti are respectively at 459.32 and 465eV, and the two absorption peaks correspond to Ti2p_3/2And Ti2p_1/2Can prove that the compound state of Ti is Ti⁴⁺Corresponding to the study for TiO₂Ti in (1); FIG. d is a high resolution spectrum of P, in which only one absorption peak in the 2P orbital is present, and the absorption peak at 132.56eV is P⁵⁺Should be Ag in this study₃PO₄P in (1); FIG. e shows the high resolution spectrum of Ag, with four absorption peaks in the 3d orbital of Ag, and two absorption peaks at 368.2 and 374.5eV corresponding to Ag3d_5/2And Ag3d_3/2The two peaks can prove that the Ag nano particles exist in the state of simple substance silver, and the absorption peaks at 367.6 and 375.1eV are Ag⁺Absorption peak of (1), corresponding to Ag₃PO₄Ag ion in the middle proves that Ag₃PO₄Is present. In conclusion, the components of the composite compound are mainly Ag and Ag through X-ray photoelectron spectroscopy test₃PO₄And TiO₂From this, Ag can be further confirmed₃PO₄And Ag nanoparticles to TiO₂The surface of the nanowire.

For Ag/Ag in example 1₃PO₄/TiO₂The optical absorption of the nanocomposite was analyzed, and fig. 9 shows the prepared TiO₂Nanowires, Ag prepared under optimal conditions₃PO₄/TiO₂Nanocomposite material, Ag/Ag₃PO₄/TiO₂Ultraviolet-visible diffuse reflectance pattern of the nanocomposite. As can be seen from the figure, composite Ag₃PO₄After addition of Ag nanoparticles, TiO₂The absorption of the nano-wire to light is expanded to a visible region, and meanwhile, the absorption of the nano-composite material to ultraviolet light is also obviously enhanced; in Ag₃PO₄/TiO₂After the Ag nano particles are compounded on the surface, the absorption intensity and wavelength of light are not obviously increased, mainly because the surface of the Ag nano particles has a plasma resonance effect and is not like compounded Ag₃PO₄The TiO can be obviously improved as the same as the nano particles with narrow forbidden band width₂The absorption wavelength of (1). As described above, in TiO₂Nano wire surface composite Ag₃PO₄And after Ag nano particles are used, the optical absorption performance of the Ag nano particles is obviously enhanced, the absorption range of light is expanded from an ultraviolet region to a visible region, and the utilization rate of light is improved.

For Ag/Ag in example 1₃PO₄/TiO₂The action mechanism of the nanocomposite was analyzed, and FIG. 10 shows Ag/Ag₃PO₄/TiO₂A photoelectrochemical corrosion resistance mechanism diagram of the nano composite material under the irradiation of visible light. According to Ag, Ag₃PO₄And TiO₂The conduction and valence band potential distributions present a possible corrosion mechanism diagram. When light irradiates Ag/Ag₃PO₄/TiO₂When the surface of the nano composite material is coated, the Ag nano particles have surface plasma resonance effect and can quickly generate photoproduction electrons, TiO₂And Ag₃PO₄The photo-generated electrons rapidly transit from the valence band to the conduction band position due to the excitation of light. The Ag surface has a lower Schottky barrier and the conduction band potential is negative to Ag₃PO₄The potential of the conduction band is increased, so that electrons on the conduction band of the Ag nano-particles can rapidly transit to Ag₃PO₄On the guide belt; in the same way, Ag₃PO₄The potential of the conduction band is negative to TiO₂Conduction band potential, so Ag₃PO₄And electrons on Ag conduction band are rapidly enriched to TiO₂Of a guide beltThe photo-generated electrons finally pass through the regular TiO₂The nanowires reach the surface of the 304 stainless steel, and enriched electrons participate in the cathode oxygen reduction process of the 304 stainless steel, so that the cathode reaction is reduced, the 304 stainless steel anode dissolution reaction is simultaneously inhibited, and the purpose of protecting the 304 stainless steel cathode is achieved. In the presence of Na in the reaction system₂SO₃Hole traps, Ag₃PO₄Nanoparticles and TiO₂The holes generated in the valence band can rapidly form polysulfides with the hole traps. Due to the existence of the hole trapping agent, the probability of recombination of photogenerated electrons and holes is reduced, the capability of generating electrons by the nano composite material is further improved, and good cathodic protection can be provided for 304 stainless steel coupled with the nano composite material. Thus, Ag/Ag under visible light irradiation₃PO₄/TiO₂The photo-anode effectively reduces the corrosion rate of 304 stainless steel and shows good photo-cathode protection effect, namely through Ag and Ag₃PO₄With TiO₂The formed nano composite film can effectively improve the photoproduction cathode protection effect of the film on metal.

Ag/Ag according to the invention₃PO₄/TiO₂Making TiO from nano composite film photo-anode material₂The light absorption range of the photo-anode is enlarged from an ultraviolet region to a visible region, so that the photo-anode not only can inhibit the corrosion of metal, but also has excellent photoelectric conversion effect, and can play a good photo-generated cathode protection effect on 304 stainless steel as a photo-anode.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.