Nanowire array composite photoelectric film for photoinduced cathodic protection and its preparation and application

Abstract

The present invention belongs to the field of photocathodic protection. Specifically, the present invention relates to a CdS / rGOQDs / TiO2 branched nanowire array composite photoelectric film, its preparation method, and application. A TiO2 nanowire array substrate film with a branched structure is constructed by a simple in-situ hydrothermal method. Then, rGO quantum dots and CdS nanoparticles are deposited thereon by constant current cathode reduction deposition and continuous ion layer adsorption reaction, thereby constructing a CdS / rGO QDs / TiO2 branched nanowire heterojunction photoelectrode with sufficient interface contact. Under simulated sunlight irradiation, the composite film can achieve photocathodic protection for a variety of metal materials (such as 316L SS and Cu) in seawater, and has the advantages of simple operation and high photoelectric conversion efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of photocathode protection, and in particular relates to a CdS / rGO QDs / TiO2 branched nanowire array composite photoelectric film for photocathode protection, and a preparation method and application thereof. Background Art

[0002] Metal materials used in marine environments, exposed to harsh, high-chloride environments, suffer from severe corrosion failure, resulting in significant economic losses, serious industrial accidents, and ecological degradation. Consequently, researchers are actively developing new technologies to mitigate and protect metal corrosion. Photocathodic protection (PCP) is a novel corrosion protection technology currently under extensive research. It leverages the excellent photoelectric conversion properties of semiconductor photoelectric conversion materials to generate photogenerated electrons under illumination. These electrons then bond to metal materials and transfer them to the metal, thereby inhibiting further corrosion. This environmentally friendly and economically viable technology relies heavily on the selection of semiconductor materials. TiO2 has been widely used in photoelectrochemical applications due to its stable performance, low cost, and environmental friendliness. However, its wide band gap, limited response to ultraviolet light, and the ease with which photogenerated electron-hole pairs recombine significantly limit its photoelectric performance. Therefore, modifying TiO2 to improve its photoelectric properties makes it feasible for PCP applications.

[0003] In recent years, research has found that micromorphology control is an effective way to improve the photoelectric properties of materials. It can provide a direct transmission path for electrons and increase the light capture area, thereby improving the efficiency of electron utilization. In addition, compounding with other semiconductors to construct a heterojunction system can also effectively promote the separation and transmission of photogenerated electrons and holes, improving photoelectric conversion performance. To further improve the electron transport performance, the use of graphene materials with extraordinary electron transport properties and a unique quasi-two-dimensional single-layer structure of sp2-bonded carbon atoms for modification can further improve the photoelectrochemical and photoinduced cathodic protection properties of the material. In summary, based on the above effective methods for improving the photoelectric properties of TiO2, its application in the protection of marine metal materials can broaden its application in the field of corrosion protection. Summary of the Invention

[0004] In response to the problem of photocathodic protection of the above-mentioned metal material corrosion, the purpose of the present invention is to provide a CdS / rGO QDs / TiO2 branched nanowire array composite photoelectric film for photocathodic protection, as well as its preparation method and application.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A CdS / rGO QDs / TiO2 branched nanowire array composite photoelectric film for photocathodic protection. The composite photoelectric film is a composite heterojunction system photoelectric material constructed by depositing rGO quantum dots and CdS nanoparticles on a TiO2 nanowire array substrate with a branched structure.

[0007] The branched TiO2 nanowire substrate is a TiO2 thin film material grown directly on a conductive substrate using an in-situ hydrothermal method by regulating the amount of initial reaction solvent. Specifically, clean FTO conductive glass is placed in an autoclave, and solution a is added for hydrothermal synthesis at 160-200°C for 8-10 hours to directly grow a branched TiO2 nanowire substrate. Solution a is a solution of potassium titanium oxalate powder dissolved in diethylene glycol (DEG) and deionized water (H2O), with a volume ratio of DEG to H2O of (2.7-3.3): (0.9-1.10), and the final concentration of potassium titanium oxalate powder in solution a is 1.9-2.1mM. After the hydrothermal reaction, the substrate is annealed in a muffle furnace to obtain an off-white TiO2 nanowire substrate.

[0008] The deposition is carried out by respectively depositing appropriate amounts of rGO quantum dots and CdS nanoparticles on a TiO2 nanowire array substrate film with a branched structure through constant current cathode reduction deposition and continuous ion layer adsorption reaction.

[0009] The constant current cathode reduction deposition is to place a TiO2 nanowire film substrate with a branched structure in solution b and perform electrodeposition under a constant cathode current; wherein solution b is 80-120 μL of graphene oxide quantum dot solution dissolved in a solution containing solution c and adjusted to a pH of 9 by solution d, and solution c is 0.9-1.1 mol·L -1 Na2HPO4 solution, solution d is 0.09-0.11mol·L -1 of NaOH solution.

[0010] The continuous ion layer adsorption reaction is to immerse the prepared photoelectric material in solution e and solution f in turn for a certain period of time, and thoroughly rinse the photoelectric material with deionized water between the two immersion steps. This immersion process is repeated 10-20 times until the required amount of CdS nanoparticles is incorporated. Wherein solution e is 2-3 mmol·L -1 Cd(NO3)2 solution, solution f is 2-3mmol·L -1 Finally, the yellow CdS / rGO QDs / TiO2 composite photoanode was obtained by drying.

[0011] A method for preparing a CdS / rGO QDs / TiO2 branched nanowire array composite photoelectric film for photoinduced cathodic protection comprises the following steps: directly growing a TiO2 branched nanowire array base film with a branched structure on a conductive substrate by an in-situ hydrothermal method; then sequentially depositing appropriate amounts of rGO quantum dots and CdS nanoparticles on the TiO2 nanowire array base film with a branched structure by constant current cathode reduction deposition and continuous ion layer adsorption reaction; the three are in full contact to form a CdS / rGOQDs / TiO2 branched nanowire heterojunction composite photoelectric film.

[0012] Specifically:

[0013] 1) Preparation of a branched TiO2 nanowire array substrate: Pretreated conductive glass was placed in the inner container of an autoclave with the conductive surface facing downward at a 45° angle to the autoclave wall. Solution a was added to the autoclave to submerge the glass substrate, and then heated at 160-200°C for 8-10 hours to directly grow a TiO2 nanowire thin film substrate with a branched structure. Solution a was prepared by dissolving potassium titanium oxalate powder in diethylene glycol (DEG) and deionized water (H2O) in a volume ratio of DEG to H2O of (2.7-3.3):(0.9-1.10). The final concentration of the potassium titanium oxalate powder in solution a was 1.98-2.02 mM.

[0014] 2) Preparation of rGO QDs / TiO2 branched nanowire composite photoelectric film: The TiO2 nanowire film substrate with branched structure prepared in step 1) was placed in solution b and electrodeposited under a constant cathode current; wherein solution b was prepared by dissolving 80-120 μL of graphene oxide quantum dot solution in a solution containing solution c and adjusting the pH to 9 by solution d, and solution c was 0.9-1.1 mol·L -1 Na2HPO4 solution, solution d is 0.09-0.11mol·L -1 of NaOH solution.

[0015] 3) Preparation of CdS / rGO QDs / TiO2 nanowire composite photoelectric film: The rGO QDs / TiO2 branched nanowire composite photoelectric film prepared in step 2) was immersed in solution e and solution f for a certain period of time. The photoanode was thoroughly rinsed with deionized water between the two immersion steps. This immersion process was repeated 10-20 times until the desired amount of CdS nanoparticles was incorporated. Wherein solution e was 2-3 mmol·L -1 Cd(NO3)2 solution, solution f is 2-3mmol·L -1 of Na2S solution.

[0016] The invention discloses an application of a CdS / rGO QDs / TiO2 branched nanowire array composite photoelectric film for photoinduced cathode protection, wherein the composite photoelectric film is used as an anti-corrosion protection photoanode for inhibiting metal corrosion.

[0017] The composite photovoltaic film is used as a photoanode. After coupling with different metals in a seawater environment (3.5wt% NaCl solution), it generates a positive photogenerated current density and a large photoinduced potential drop under the irradiation of simulated sunlight (AM1.5), thereby achieving anti-corrosion protection for different metal materials.

[0018] A CdS / rGO QDs / TiO2 branched nanowire array composite photoanode for photoinduced cathode protection, wherein the photoanode contains the CdS / rGO QDs / TiO2 branched nanowire array composite material.

[0019] Preparation of a CdS / rGO QDs / TiO2 branched nanowire array composite photoanode for photocathodic protection, wherein a portion of the CdS / rGO QDs / TiO2 branched nanowire array composite material is scraped off to leave a remaining film material area of ​​10×10 mm 2 , the scraped part was coated with insulating silicone and affixed with copper tape to prepare a photoanode for measuring the photocathodic protection performance.

[0020] The CdS / rGO QDs / TiO2 branched nanowire array composite photoanode prepared above for photocathodic protection was coupled with the metal to be protected to test its photocathodic protection performance. Specifically, a system consisting of a CdS / rGO QDs / TiO2 photocell and a corrosion electrolytic cell was used. The photocell used the CdS / rGO QDs / TiO2 photoanode as the working electrode, a Pt electrode and an Ag / AgCl electrode as the counter electrode and reference electrode, and the electrolyte solution was 0.25 mol·L -1 Na2S+0.35mol·L -1 The corrosion electrolytic cell contained a protected metal electrode and a 3.5 wt% NaCl solution. The photoanode and the protected metal electrode were connected by wires. A xenon lamp was used as the light source to simulate sunlight (AM1.5, light power density 100 mW·cm -2 ) and placed in front of the photocell so that light directly hit the CdS / rGO QDs / TiO2 photoanode. The changes in the coupled photogenerated current density and mixing potential under on / off light conditions were recorded using an electrochemical workstation (CHI 660D).

[0021] The basic principle of the present invention: First, the TiO2 nanowire array with a branched structure can provide a large number of photon absorption areas and photogenerated electron collection sites, which can serve as a direct electron transport pathway to promote the rapid collection and transfer of photogenerated electrons. The narrow bandgap CdS sensitizer broadens the light response range and improves the light utilization rate; and constructs a heterojunction electric field at the interface to improve the separation efficiency of photogenerated electrons / holes. rGO QDs have excellent conductive properties. They are uniformly deposited on the surface of the TiO2 nanowire array to form a tight interface bond, which promotes the rapid transmission and collection of photogenerated electrons between TiO2 and CdS. Under simulated sunlight, the photoelectrode is excited to generate a large number of photogenerated electrons, which are quickly transferred to the coupled metal surface, generating a positive photocurrent density, causing the protected metal potential to shift negatively, thereby putting it in a protected state and achieving efficient photocathodic protection performance.

[0022] The advantages of the present invention are:

[0023] 1. The CdS / rGO QDs / TiO2 branched nanowire array composite photoelectric film of the present invention has the characteristics of simple preparation process, significant effect, and improves the utilization of sunlight.

[0024] 2. Through a constant current cathodic reduction reaction, graphene oxide quantum dots in solution are easily reduced and deposited onto the TiO2 surface. Due to the excellent electron transport properties of graphene quantum dots, the transmission efficiency of photogenerated electrons in the photoanode can be greatly improved, and the separation of photogenerated electron-hole pairs can be promoted, thereby further improving the photoelectric performance of the photoanode and the efficiency of photoelectrochemical cathodic protection.

[0025] 3. Under simulated sunlight, the coupled 316LSS and Cu can generate 0.72 mA cm -2 and 1.45 mA·cm -2 The photoinduced current density was increased and the potential dropped by 880mV and 900mV respectively, resulting in significant cathodic polarization, which well protected 316L SS and Cu. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Comparison of the photoelectrochemical properties (It) of rGO QDs / TiO2 nanocomposite photoelectrodes prepared with different initial graphene oxide quantum dot solutions (GO QDs) added and different electrodeposition times provided in Example 1 of the present invention.

[0027] Figure 2TEM image (a) of the branched structure TiO2 nanowires provided in Example 1 of the present invention, HRTEM image (b) of the rGO QDs / TiO2 nanocomposite photoelectrode, and HRTEM image (c) of the CdS / rGO QDs / TiO2 nanocomposite photoelectrode.

[0028] Figure 3 Curves of the change of photogenerated current density over time when the prepared TiO2, rGO QDs / TiO2 (abbreviated as GT), CdS / TiO2 (abbreviated as CT) and CdS / rGO QDs / TiO2 (abbreviated as CGT) photoelectrodes provided in Example 1 of the present invention were coupled with 316L SS electrodes under intermittent simulated sunlight irradiation.

[0029] Figure 4 This is a curve showing the change of the photoinduced mixed potential over time after the prepared CT and CGT photoelectrodes provided in Example 1 of the present invention are coupled with a 316L SS electrode under intermittent simulated sunlight irradiation.

[0030] Figure 5 This is a curve showing the change in photocurrent density over time when the TiO2, GT, CT and CGT photoelectrodes prepared in Example 2 of the present invention are coupled with a Cu electrode under intermittent simulated sunlight irradiation.

[0031] Figure 6 This is a curve showing the change of the photoinduced mixing potential over time after the prepared CT and CGT photoelectrodes provided in Example 2 of the present invention are coupled with a Cu electrode under intermittent simulated sunlight irradiation. DETAILED DESCRIPTION

[0032] The specific embodiments of the present invention are further described below with reference to examples. It should be noted that the specific embodiments described here are only for illustrating and explaining the present invention, and are not intended to limit the present invention.

[0033] The present invention uses a simple in-situ hydrothermal method to construct a TiO2 nanowire array substrate film with a branched structure, and then uses constant current cathode reduction deposition and continuous ion layer adsorption reaction to deposit rGO quantum dots and CdS nanoparticles thereon (the deposition amount is regulated by controlling the initial concentration of the rGO quantum dot solution and the deposition time, as well as the number of deposition cycles of the CdS nanoparticles), to construct a CdS / rGO QDs / TiO2 branched nanowire heterojunction photoelectrode with sufficient interface contact. The successful preparation of rGO quantum dots and CdS nanoparticles can be well observed and confirmed by comparing the microscopic morphology and the photoelectric and photoelectrochemical cathodic protection performance. Under simulated sunlight irradiation, the composite film can achieve photocathodic protection of various metal materials (such as 316L SS and Cu) in seawater, and has the advantages of simple operation and high photoelectric conversion efficiency.

[0034] Example 1

[0035] Preparation of CdS / rGO QDs / TiO2 branched nanowire composite photoelectric films for photoinduced cathodic protection:

[0036] 1) Preparation of FTO conductive glass: First, cut the FTO glass into 20×10mm 2 The FTO glass was ultrasonically cleaned in analytical pure acetone for 5 minutes and then cleaned in deionized water for 5 minutes. After that, the FTO glass was dried for use.

[0037] 2) Preparation of TiO2 branched nanowire substrate: The FTO conductive glass treated in step 1) was placed in the inner container of an autoclave, with the conductive surface facing downward and at a 45° angle to the autoclave wall. Solution a was added to the autoclave to submerge the glass substrate, and then hydrothermal treatment was performed at 180°C for 9 hours. After the hydrothermal treatment, the FTO glass was removed, repeatedly rinsed with deionized water, dried, and then annealed at 450°C for 1 hour to obtain a TiO2 nanowire thin film substrate with a branched structure (see Figure 2 a). Solution a was prepared by adding 0.708 g of potassium titanium oxalate to 10 mL of deionized water, stirring the mixture under magnetic stirring for 10 minutes, and then adding 30 mL of DEG and stirring the mixture for 20 minutes.

[0038] 3) Preparation of rGO QDs / TiO2 nanowire composite photoelectric film: The TiO2 nanowire substrate with a branched structure prepared in step 2) was placed in solution b and electrodeposited for different times (20-40 minutes) at a constant cathode current; wherein solution b was prepared by dissolving different amounts (50-100 μL) of graphene oxide quantum dot solution in solution c adjusted to pH 9 by solution d, and solution c was 1 mol·L -1 Na2HPO4 solution, solution d is 0.1 mol·L -1After the deposition, the sample was taken out, rinsed with water and dried to obtain the rGO QDs / TiO2 (abbreviated as GT) branched nanowire composite material (see Figure 2 b).

[0039] 4) Preparation of CdS / rGO QDs / TiO2 nanowire composite photoelectric film: The GT composite photoelectrode prepared in step 3) was immersed in solution e and solution f for 20 seconds each, and then rinsed with deionized water. This immersion process was repeated 15 times until the desired amount of CdS nanoparticles was incorporated. The concentration of solution e was 2.5 mmol / L -1 Cd(NO3)2 solution, solution f is 2.5mmol·L -1 Finally, the impregnated sample was placed in a drying oven to dry, and a CdS / rGO QDs / TiO2 (abbreviated as CGT) nanowire composite photoelectric film was obtained (see Figure 2 c).

[0040] 5) Preparation of CdS / rGO QDs / TiO2 branched nanowire composite photoanode: Scrape off part of the CdS / rGO QDs / TiO2 branched nanowire composite material prepared on the surface of FTO conductive glass to leave an area of ​​the remaining film material of 10×10 mm 2 , the scraped part was coated with insulating silicone and affixed with copper tape to prepare a photoanode for measuring the photocathodic protection performance.

[0041] 5) Preparation of 316L SS electrodes: Embed a square 316L SS block in epoxy resin so that the exposed area is 10 × 10 mm 2 The 316L SS electrodes were then wet-ground with SiC paper to 2000 mesh and ultrasonically cleaned in analytical grade ethanol for 5 min.

[0042] The photoelectrochemical performance (It) of the CdS / rGO QDs / TiO2 branched nanowire composite photoelectrode prepared above was analyzed and compared under different initial addition amounts of graphene oxide quantum dot solution (GO QDs) and different electrodeposition times (see Figure 1 The photoelectrochemical performance (It) of rGO QDs / TiO2 nanocomposite photoelectrodes prepared with different initial GO QD addition amounts (50, 100, and 150 μL) and different electrodeposition times (20, 30, and 40 minutes) was explored. It can be seen that the rGO QDs / TiO2 photoanode prepared with an addition amount of 100 μL of graphene oxide quantum dot solution and an electrodeposition time of 30 minutes has the best performance.

[0043] And through Figure 2TEM image of the branched structure TiO2 nanowires obtained, HRTEM image (b) of the rGO QDs / TiO2 nanocomposite photoelectrode obtained with a GO QDs addition amount of 100 μL and an electrodeposition time of 30 minutes, and HRTEM image (c) of the CdS / rGO QDs / TiO2 nanocomposite photoelectrode. Figure 2 a It can be seen that the pure TiO2 photoelectrode is a large number of ultrafine nano-branch structures, each branch has a diameter of only about 10nm and a length of about hundreds of nanometers. Figure 2 b is the HRTEM image of the TiO2 photoanode modified with rGO QDs. The lattice spacing of TiO2 is 0.352nm. It can be clearly seen that there are multiple rGOQDs on the TiO2 nanowires, and the lattice spacing is 0.21nm, which also confirms the successful deposition of rGO QDs. Figure 2 The HRTEM image of CdS / rGO QDs / TiO2 in Figure c shows that in addition to rGO QDs, CdS nanoparticles with lattice spacings of 0.336 and 0.206 nm were also observed on the TiO2 nanowires. The above morphological characterization confirms the successful preparation of the ultrafine branched TiO2 nanowire-based photoanode and the successful deposition of rGO quantum dots and CdS nanoparticles.

[0044] At the same time, for comparison, TiO2 branched nanowire photoanodes (i.e., obtained in step 2 above), rGO QDs / TiO2 (i.e., GT prepared in step 3), and CdS / TiO2 (i.e., TiO2 obtained in step 2 directly subjected to step 4) photoanodes were also prepared, and the preparation methods were similar to those mentioned above.

[0045] The photocathodic protection performance of the CdS / rGO QDs / TiO2 branched nanowire composite photoelectrode and other photoelectrodes prepared above was tested using a system consisting of a CdS / rGO QDs / TiO2 photocell and a corrosion electrolytic cell. The photocell used a CdS / rGO QDs / TiO2 photoanode as the working electrode, a Pt electrode and an Ag / AgCl electrode as the counter electrode and reference electrode, and a 0.25 mol·L electrolyte solution. -1 Na2S+0.35mol·L -1 The corrosion electrolytic cell contained a protected metal electrode (316L SS) and a 3.5 wt% NaCl solution. The photoanode was connected to the protected 316L SS electrode via a wire. A xenon lamp was used as the light source to simulate sunlight (AM1.5 light with a light power density of 100 mW·cm -2 ) and placed in front of the photocell so that light directly hits the CdS / rGO QDs / TiO2 photoanode. The photocurrent intensity ( Figure 3 ) and photoinduced mixed potential ( Figure 4 )change.

[0046] Depend on Figure 3 It can be seen that under intermittent simulated sunlight irradiation, the photoinduced current intensity changes of the prepared TiO2, GT, CT and CGT photoelectrodes after coupling with 316L SS electrodes. When the light is turned on, the cathodic protection current of all the prepared photoelectrodes is positive, indicating that the photogenerated electrons are continuously transferred to the 316L SS electrode, thereby achieving cathodic protection. The photoinduced cathodic protection current density of the CGT composite photoelectrode on 316L SS is about 0.72 mA cm -2 , which is 30% higher than that of TiO2 modified with CdS alone, and is much higher than the results of TiO2 and GT samples, indicating that the composite system material modified with graphene quantum dots has good photocathodic protection performance.

[0047] Depend on Figure 4 It can be seen that under intermittent simulated sunlight irradiation, the mixed potential of the prepared CT and CGT photoelectrodes after coupling with the 316L SS electrode changes. When the light is turned on, the mixed potential shifts negatively; when the light is turned off, the potential shifts positively and slowly returns to its initial potential. This shows that the negative shift of the mixed potential under light irradiation is entirely caused by the photogenerated electrons generated by the photoelectrode. The negative potential shift indicates that the photogenerated electrons generated on the photoelectrode are transferred to the coupled 316L SS electrode, thereby providing cathodic protection for the 316L SS. This result is consistent with Figure 2 The results of the photoinduced cathodic protection current density are consistent with those shown in Figure 2. The photoinduced potential drop of CGT-316L SS (about 880 mV) is significantly greater than that of the CT sample, indicating that the graphene quantum dot modification further improves the photoinduced cathodic protection performance of the metal under light, and can achieve protection of the metal in 3.5wt% NaCl solution.

[0048] Example 2

[0049] Preparation of CdS / rGO QDs / TiO2 branched nanowire composite photoelectric films for photoinduced cathodic protection:

[0050] 1) Preparation of FTO conductive glass: First, cut the FTO glass into 20×10mm 2 The FTO glass was ultrasonically cleaned in analytical pure acetone for 5 minutes and then cleaned in deionized water for 5 minutes. After that, the FTO glass was dried for use.

[0051] 2) Preparation of TiO2 branched nanowire substrate: The FTO conductive glass treated in step 1) was placed in the inner container of an autoclave, with the conductive surface facing downward and at a 45° angle to the autoclave wall. Solution a was added to the autoclave to submerge the glass substrate, and then hydrothermal treatment was performed at 180°C for 9 hours. After the hydrothermal treatment, the FTO glass was removed, repeatedly rinsed with deionized water, dried, and then annealed at 450°C for 1 hour to obtain a TiO2 nanowire thin film substrate with a branched structure (see Figure 2 a). Solution a was prepared by adding 0.708 g of potassium titanium oxalate to 10 mL of deionized water, stirring the mixture under magnetic stirring for 10 minutes, and then adding 30 mL of DEG and stirring the mixture for 20 minutes.

[0052] 3) Preparation of rGO QDs / TiO2 nanowire composite photoelectric film: The TiO2 nanowire substrate with branched structure prepared in step 1) was placed in solution b and electrodeposited at a constant cathode current for 30 minutes; wherein solution b was prepared by dissolving 100 μL of graphene oxide quantum dot solution in solution c adjusted to pH 9 by solution d, and solution c was 1 mol·L -1 Na2HPO4 solution, solution d is 0.1 mol·L -1 After the deposition, the sample was taken out, rinsed with water and dried to obtain the rGO QDs / TiO2 (abbreviated as GT) branched nanowire composite material.

[0053] 4) Preparation of CdS / rGO QDs / TiO2 nanowire composite photoelectric film: The GT composite photoelectrode prepared in step 3) was immersed in solution e and solution f for 20 seconds each, and then rinsed with deionized water. This immersion process was repeated 15 times until the required amount of CdS nanoparticles was incorporated. The concentration of solution e was 2.5 mmol / L -1 Cd(NO3)2 solution, solution f is 2.5mmol·L -1 Finally, the impregnated sample was placed in a drying oven to dry, and a CdS / rGO QDs / TiO2 (abbreviated as CGT) nanowire composite photoelectric film was obtained.

[0054] 5) Preparation of CdS / rGO QDs / TiO2 branched nanowire composite photoanode: Scrape off part of the CdS / rGO QDs / TiO2 branched nanowire composite material prepared on the surface of FTO conductive glass to leave an area of ​​the remaining film material of 10×10 mm 2 , the scraped part was coated with insulating silicone and affixed with copper tape to prepare a photoanode for measuring the photocathodic protection performance.

[0055] 5) Preparation of Cu electrode: Embed a square Cu block in epoxy resin so that the exposed area is 10×10 mm2 The Cu electrodes were then wet-grinded with SiC paper to 2000 mesh and ultrasonically cleaned in analytical grade ethanol for 5 min.

[0056] At the same time, for comparison, TiO2 branched nanowire photoanodes (i.e., obtained in step 2 of the above embodiment), rGOQDs / TiO2 (i.e., GT prepared in step 3), and CdS / TiO2 (i.e., TiO2 obtained in step 2 is directly subjected to step 4) photoanodes were also prepared, and the preparation methods were similar to those described above.

[0057] The photocathodic protection performance of the CdS / rGO QDs / TiO2 branched nanowire composite photoelectrode prepared above was tested for the Cu electrode using the same test method as in Example 1. The photocurrent intensity ( Figure 5 ) and photoinduced mixed potential ( Figure 6 )change.

[0058] Depend on Figure 5 It can be seen that under intermittent simulated sunlight irradiation, the photoinduced current intensity of the prepared TiO2, GT, CT and CGT photoelectrodes coupled with the Cu electrode changes. Like 316L SS, the cathodic protection current of all prepared photoelectrodes showed positive under light, indicating that the photogenerated electrons were continuously transferred to the Cu electrode to achieve cathodic protection. The photoinduced cathodic protection current density of the CGT composite photoelectrode for Cu was about 1.45 mA cm -2 Compared with the CT photoanode, the performance is improved by about 30%, and the current density is much higher than the results of TiO2 and GT samples, indicating that the composite system material modified with graphene quantum dots has good photocathodic protection performance for metal Cu.

[0059] Depend on Figure 6 It can be seen that under intermittent simulated sunlight irradiation, the mixed potential of the prepared CT and CGT photoelectrodes after coupling with the Cu electrode changes. It can be seen that the potential shifts significantly negatively under light irradiation, indicating that the photogenerated electrons generated on the photoelectrode are transferred to the coupled Cu electrode, thereby providing cathodic protection for Cu. This result is consistent with Figure 4The results of the photoinduced cathodic protection current density shown are consistent with those of the CT sample. Although the self-corrosion potential of metallic Cu is more negative than that of 316L SS, its photoinduced potential drop is close to that of 316L SS. The photoinduced potential drop of CGT-Cu is also as high as 900 mV, significantly greater than that of the CT sample. This indicates that graphene quantum dot modification further improves the photoinduced cathodic protection performance of metals under illumination, achieving protection for metallic Cu with an even more negative self-corrosion potential in 3.5wt% NaCl solution. These results demonstrate that the prepared CdS / rGO QDs / TiO2 branched nanowire composite photoelectrode has great potential for practical anti-corrosion applications on various metal materials in marine environments.

[0060] The nanocomposite material described in the present invention can inhibit metal corrosion and has an excellent photoelectric conversion effect. It can act as a photoanode to provide good photocathodic protection for a variety of metals in a simulated real marine environment, thereby promoting the application of photoelectric materials in actual photocathodic protection.

Claims

1. A branched nanowire array composite photovoltaic film for photocathodic protection, characterized by: The composite photoelectric film is a composite heterojunction system CdS / rGO QDs / TiO2 branched nanowire array composite photoelectric film constructed by depositing rGO quantum dots and CdS nanoparticles on a TiO2 nanowire array substrate with a branched structure; The TiO2 nanowire array substrate with a branched structure is a TiO2 thin film material grown directly on a conductive substrate using an in-situ hydrothermal method by regulating the amount of the initial reaction solvent. Specifically, clean FTO conductive glass is placed in a high-pressure reactor with the conductive surface facing down, and solution a is added for hydrothermal synthesis at 160-200°C for 8-10 hours to directly grow a TiO2 nanowire array substrate film with a branched structure; wherein, solution a is a solution of potassium titanium oxalate powder dissolved in diethylene glycol (DEG) and deionized water, and the volume ratio of DEG to deionized water is (2.7-3.3): (0.9-1.10), and the final concentration of potassium titanium oxalate powder in solution a is 1.9-2.1mM. After the hydrothermal reaction is completed, it is annealed in a muffle furnace to obtain an off-white TiO2 nanowire substrate.

2. The branched nanowire array composite photovoltaic film for photocathodic protection according to claim 1, characterized in that: The deposition is carried out by respectively depositing rGO quantum dots and CdS nanoparticles on a TiO2 nanowire array substrate film with a branched structure through constant current cathode reduction deposition and continuous ion layer adsorption reaction.

3. The branched nanowire array composite photovoltaic film for photocathodic protection according to claim 2, characterized in that: The constant current cathode reduction deposition is to place a TiO2 nanowire film substrate with a branched structure in solution b and perform electrodeposition under a constant cathode current to obtain a photoelectric material; wherein solution b is a solution obtained by dissolving 80-120 μL of graphene oxide quantum dot solution in solution c adjusted to pH 9 by solution d, and solution c is 0.9-1.1 mol×L -1 Na2HPO4 solution, solution d is 0.09-0.11mol×L -1 of NaOH solution.

4. The branched nanowire array composite photovoltaic film for photocathodic protection according to claim 2, characterized in that: The continuous ion layer adsorption reaction is to immerse the photoelectric material prepared by constant current cathode reduction deposition in solution e and solution f in sequence, and thoroughly rinse the photoelectric material with deionized water after each immersion step. This immersion process is repeated 10-20 times until the required amount of CdS nanoparticles is incorporated, wherein solution e is 2-3 mmol×L -1 Cd(NO3)2 solution, solution f is 2-3mmol×L -1 of Na2S solution.

5. A method for preparing the branched nanowire array composite photovoltaic thin film for photoinduced cathodic protection according to claim 1, characterized in that: A TiO2 branched nanowire array base film with a branched structure is directly grown on a conductive substrate by an in-situ hydrothermal method. Then, rGO quantum dots and CdS nanoparticles are deposited on the TiO2 nanowire array base film with a branched structure by constant current cathode reduction deposition and continuous ion layer adsorption reaction respectively. The three are in full contact to form a CdS / rGOQDs / TiO2 branched nanowire heterojunction composite photoelectric film.

6. The method for preparing a CdS / rGO QDs / TiO2 branched nanowire array composite photovoltaic film for photocathodic protection according to claim 5, characterized in that: 1) Preparation of a branched TiO2 nanowire array substrate: Pretreated conductive glass was placed in the inner container of an autoclave with the conductive surface facing downward at a 45° angle to the autoclave wall. Solution a was added to the autoclave to submerge the glass substrate, and then heated at 160-200°C for 8-10 hours to directly grow a TiO2 nanowire thin film substrate with a branched structure. Solution a was a solution of potassium titanium oxalate powder dissolved in diethylene glycol (DEG) and deionized water, with a volume ratio of DEG to deionized water of (2.7-3.3):(0.9-1.10). The final concentration of the potassium titanium oxalate powder in solution a was 1.9-2.1 mM. 2) Preparation of rGO QDs / TiO2 branched nanowire composite photoelectric film: The TiO2 nanowire film substrate with branched structure prepared in step 1) was placed in solution b and electrodeposited under a constant cathode current; wherein solution b was prepared by dissolving 80-120 μL of graphene oxide quantum dot solution in solution c adjusted to pH 9 by solution d, and solution c was 0.9-1.1 mol×L -1 Na2HPO4 solution, solution d is 0.09-0.11mol×L -1 NaOH solution; 3) Preparation of CdS / rGO QDs / TiO2 nanowire composite photoelectric film: The rGO QDs / TiO2 branched nanowire composite photoelectric film prepared in step 2) was sequentially immersed in solution e and solution f. After each immersion, the photoanode was thoroughly rinsed with deionized water. This immersion process was repeated 10-20 times until the desired CdS nanoparticles were incorporated. The concentration of solution e was 2-3 mmol × L -1 Cd(NO3)2 solution, solution f is 2-3mmol×L -1 of Na2S solution.

7. An application of the CdS / rGO QDs / TiO2 branched nanowire array composite photoelectric film for photocathodic protection according to claim 1, characterized in that: The composite photovoltaic film is used as an anti-corrosion protection photoanode for inhibiting metal corrosion.

8. A CdS / rGO QDs / TiO2 branched nanowire array composite photoanode for photoinduced cathodic protection, characterized by: The photoanode is a composite photoelectric film containing the CdS / rGO QDs / TiO2 branched nanowire array according to claim 1.

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