A method for electrocatalytic degradation of perfluorooctanoic acid, a modified titanium electrode and a preparation method thereof

Abstract

The application discloses a perfluorooctanoic acid electrocatalytic degradation method, a modified titanium electrode and a preparation method thereof, and belongs to the technical field of organic pollutant degradation. The modified titanium electrode is used as a working electrode for perfluorooctanoic acid electrocatalytic degradation, the modified titanium electrode comprises a titanium base body and a titanium nitride active layer located on the surface of the titanium base body, and the titanium nitride active layer is distributed with a micro-nano composite structure, the micro-nano composite structure comprises a micron-level groove array on the titanium nitride active layer and titanium nitride nano structures distributed in the grooves. The application adopts a Ti-Ti3N4 micro-nano composite structure electrode as an electrocatalytic electrode to electrocatalytically degrade perfluorooctanoic acid, so that the degradation efficiency of PFOA can be effectively improved, and the problems of limited reaction rate, high energy consumption and insufficient electrode active sites existing in the prior art electrochemical oxidation technology are solved.

Description

Technical Field

[0001] This invention belongs to the field of organic pollutant degradation technology, and more specifically, relates to a method for electrocatalytic degradation of perfluorooctanoic acid, a modified titanium electrode and its preparation method. Background Technology

[0002] Perfluorooctanoic acid (PFOA) is an organic pollutant with strong chemical stability, bioaccumulation, and environmental persistence. It exists in industrial wastewater, drinking water, and soil environments, posing a potential risk to ecological safety and human health. The CF covalent bond energy in the PFOA molecule is as high as 485 kJ / mol, making it difficult to degrade using traditional physical, chemical, or biological methods. Therefore, developing efficient and low-cost PFOA pollution control technologies has become an urgent need in the environmental field.

[0003] Electrocatalytic degradation technology has become one of the most promising PFOA treatment pathways due to its advantages such as mild reaction conditions, no secondary pollution, and strong controllability. However, existing electrochemical oxidation technologies have problems such as limited reaction rate, high energy consumption, and insufficient electrode active sites, resulting in slow PFOA electrocatalytic degradation reaction kinetics. Electrode structure design is the core key to improving electrochemical reaction efficiency. Electrodes with large reaction area and high electron transfer efficiency are urgently needed to reduce the CF bond breaking overpotential. Summary of the Invention

[0004] This invention provides a method for the electrocatalytic degradation of perfluorooctanoic acid (PFOA). By using a Ti-Ti3N4 micro-nano composite electrode as the electrocatalytic electrode, the degradation efficiency of PFOA can be effectively improved, thus solving the problems of limited reaction rate, high energy consumption and insufficient electrode active sites in existing electrochemical oxidation technologies. This invention also provides a modified titanium electrode for electrocatalytic degradation of perfluorooctanoic acid (PFOA) and its preparation method. By performing laser modification treatment on the surface of the titanium substrate, a micro-nano composite structure composed of a micron-scale groove array and titanium nitride nanostructures can be constructed on the Ti3N4 active layer. This electrode has high electrocatalytic degradation activity of PFOA and can effectively improve the degradation efficiency of PFOA.

[0005] To achieve the above objectives, the technical solution provided by the present invention is as follows: The first aspect of the present invention provides a method for electrocatalytic degradation of perfluorooctanoic acid (PFOA), using a modified titanium electrode as the working electrode to electrocatalytically degrade PFOA; wherein the modified titanium electrode comprises a titanium substrate and a titanium nitride active layer located on the surface of the titanium substrate, and the titanium nitride active layer is provided with a micro-nano composite structure, the micro-nano composite structure comprising a micron-scale groove array located on the titanium nitride active layer and titanium nitride nanostructures distributed in the grooves (or trenches).

[0006] This invention applies a modified titanium electrode to the electrocatalytic degradation of perfluorooctanoic acid (PFOA). The modified titanium electrode has a titanium nitride active layer on its surface, and the titanium nitride active layer has a micro-nano composite structure. This gives the electrode high conductivity, chemical stability, and the ability to generate hydroxyl radicals efficiently. The huge specific surface area and abundant active sites can efficiently adsorb and activate PFOA molecules, significantly reduce the activation energy of CF bond breaking, and improve the CF bond breaking efficiency. Therefore, it can effectively solve the problems of limited reaction rate and insufficient electrode active sites in existing electrochemical oxidation technologies.

[0007] Specifically, the titanium matrix provides good electrical conductivity, while the micro-nano composite structure on the surface of the titanium nitride active layer can effectively increase the specific surface area, expose more active sites, and improve the electron transfer efficiency in electrocatalysis; at the same time, the introduction of the micron-scale groove array can also construct a certain channel structure, effectively improving the mass transfer efficiency of the solid-liquid interface.

[0008] Furthermore, the micron-scale groove array is preferably distributed in parallel intervals or in a cross-shaped pattern, but other groove array structures can also be used.

[0009] Furthermore, the titanium nitride nanostructure is a nanocolumnar structure, a nanoscale particle structure, or a combination of both.

[0010] Furthermore, the groove width of the micron-scale groove array is 30-120μm, such as 30μm, 40μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, etc., and the groove depth is 6-18μm, such as 6μm, 8μm, 11μm, 13μm, 16μm, 18μm, etc.

[0011] Furthermore, the thickness of the titanium nitride active layer is 2-4 μm, for example, 2 μm, 3 μm, 3.5 μm or 4 μm.

[0012] Furthermore, the radial dimension of the titanium nitride nanostructure is 150-300 nm, exemplarily such as 150 nm, 180 nm, 200 nm, 240 nm, 260 nm, 285 nm, 300 nm, etc. However, it should be noted that the radial dimension here refers to the maximum distance between any two points on the cross-section of the titanium nitride nanostructure. For example, when the titanium nitride nanostructure is a nanoscale particle structure, the radial dimension is the particle size of the nanoparticles; when the titanium nitride nanostructure is a nanocolumnar structure and its cross-section is also circular (i.e., the titanium nitride nanostructure is essentially cylindrical), the radial dimension is the diameter of the nanocolumnar structure; when the titanium nitride nanostructure is a nanocolumnar structure and its cross-section is also square (i.e., the titanium nitride nanostructure is essentially square columnar), the radial dimension is the diagonal dimension of the cross-section of the nanocolumnar structure.

[0013] By optimizing and controlling the parameter distribution of the micro-nano composite structure, such as the width and depth of the micron-level trenches and the size of the titanium nitride nanostructures, it is beneficial to further ensure the electrocatalytic degradation effect of the modified titanium electrode on perfluorooctanoic acid.

[0014] Furthermore, titanium nitride nanostructures are also distributed on the protrusions between adjacent grooves.

[0015] A second aspect of the present invention provides a modified titanium electrode for electrocatalytic degradation of perfluorooctanoic acid, the modified titanium electrode comprising a titanium substrate and a titanium nitride active layer on the surface of the titanium substrate, wherein a micro-nano composite structure is distributed on the titanium nitride active layer, the micro-nano composite structure comprising a micron-scale groove array on the titanium nitride active layer and titanium nitride nanostructures distributed in the grooves.

[0016] The modified titanium electrode of this application exhibits high activity in degrading PFOA, which helps to ensure the removal rate and efficiency of PFOA. At the same time, the modified electrode has excellent comprehensive electrochemical performance, with high electron transfer efficiency and can maintain a high current density during long-term testing, indicating that its electron transfer efficiency is significantly improved. It can quickly adsorb and activate PFOA molecules, and the electrocatalytic reaction kinetics are better. Therefore, it can fundamentally solve the problem of limited reaction rate of existing electrodes.

[0017] Furthermore, the micron-scale groove array is distributed in a parallel, spaced-out or cross-shaped pattern.

[0018] Furthermore, the titanium nitride nanostructure is a nanocolumnar structure, a nanoscale particle structure, or a combination of both.

[0019] Furthermore, the groove width of the micron-scale groove array is 30-120 μm, and the groove depth is 6-18 μm.

[0020] Furthermore, the thickness of the titanium nitride active layer is 2-4 μm, and the radial dimension of the titanium nitride nanostructure is 150-300 nm.

[0021] A third aspect of the present invention also provides a method for preparing a modified titanium electrode for the electrocatalytic degradation of perfluorooctanoic acid, comprising: A titanium matrix is ​​provided, and the titanium matrix is ​​pretreated to remove contaminants from the matrix surface; Under a nitrogen atmosphere, a femtosecond laser is used to modify the pretreated titanium substrate to form a titanium nitride active layer on its surface, and a micro-nano composite structure is simultaneously constructed on the titanium nitride active layer. The micro-nano composite structure includes a micron-scale groove array on the titanium nitride active layer and titanium nitride nanostructures distributed within the grooves.

[0022] This invention utilizes femtosecond laser technology to modify the pretreated titanium substrate, enabling the simultaneous achievement of titanium sheet surface nitriding (generating a titanium nitride active layer) and the construction of micro / nano composite structures in a single process step. No additional nitriding or structural modification steps are required, resulting in a simple overall fabrication process that significantly shortens the electrode fabrication cycle. Furthermore, the titanium nitride active layer prepared by this process forms a strong metallurgical bond with the titanium substrate, effectively preventing issues such as easy detachment and poor stability of the electrode active layer.

[0023] Furthermore, the process parameters of the femtosecond laser include: a center wavelength of 900-1100nm, a pulse width of 100-500fs, a repetition frequency of 100-500kHz, and a spot diameter of 10-50μm; more preferably: a center wavelength of 1030nm, a pulse width of 221fs, a repetition frequency of 200kHz, and a spot diameter of 20µm.

[0024] Furthermore, when modifying the pretreated titanium substrate with femtosecond laser, the scanning galvanometer is controlled so that the laser focus scans along a preset "Z" shaped path. The process parameters during scanning include: average laser power 3.5-5W, scanning speed 50-300 mm / s, and 3-16 scans.

[0025] By optimizing and controlling the process parameters during femtosecond laser processing, especially the laser power, scanning speed, and number of scans, the size distribution of the micro-grooves and nanostructures in the resulting micro-nano composite structure can be effectively regulated, thereby ensuring the electrocatalytic degradation effect of the modified electrode on PFOA. On the other hand, it is also beneficial to further ensure the strong bonding between the titanium nitride active layer and the substrate, thus ensuring the stability of the electrocatalytic degradation effect during long-term use.

[0026] When the number of scans is too low or the scanning speed is too high, it is not conducive to the formation of micro-nano composite structures, or it may result in shallow micro-grooves and fewer nano-titanium nitride structures. When the number of scans is too high or the scanning speed is too low, it may lead to coarsening of nano-titanium nitride particles or columnar structures and a decrease in distribution uniformity. Therefore, improper control of laser scanning parameters cannot effectively improve the electrocatalytic degradation effect of PFOA.

[0027] Therefore, the scanning speed in this invention is further preferably 80-250 mm / s, even more preferably 100-200 mm / s, and even more preferably 100-160 mm / s; the number of scans is further preferably 8-16.

[0028] Furthermore, the method also includes: placing the modified sample in a nitrogen atmosphere and naturally cooling it to room temperature to obtain the modified titanium electrode for the electrocatalytic degradation of perfluorooctanoic acid. Cooling under a nitrogen atmosphere can prevent the high-temperature titanium nitride active layer from contacting oxygen in the air and oxidizing, thereby ensuring the activity and structural integrity of the electrode.

[0029] In summary, by adopting the technical solution provided by this invention, the following beneficial effects can be achieved compared with the prior art: (1) The present invention uses a modified titanium electrode as the working electrode to electrocatalytically degrade perfluorooctanoic acid. The modified titanium electrode is a titanium + titanium nitride composite system and has a micro-nano composite structure on its surface, which can effectively improve the degradation effect and efficiency of PFOA and solve the problems of limited reaction rate and insufficient electrode active sites in the existing electrochemical oxidation technology.

[0030] (2) In this invention, the micro-nano composite structure of the modified titanium electrode provides a huge specific surface area and abundant active sites, which can efficiently adsorb PFOA molecules and reduce the activation energy of CF bond breaking. The measured data show that the peak reduction current of the modified electrode in the PFOA-containing electrolyte can reach up to 310 mA, which is much higher than that of the blank titanium sheet, and the PFOA removal rate at 1h / 2h / 3h is also significantly higher than that of the blank titanium sheet.

[0031] (3) The modified titanium electrode of the present invention has excellent comprehensive electrochemical performance, high electron transfer efficiency, and can maintain high current density during long-term testing, indicating that its electron transfer efficiency is significantly improved. It can quickly adsorb and activate PFOA molecules, and has better electrocatalytic reaction kinetics, which fundamentally solves the problem of limited reaction rate of existing electrodes.

[0032] (4) The present invention also provides a process for preparing a modified titanium electrode for PFOA electrocatalytic degradation. By using femtosecond laser technology, the surface nitriding of titanium sheet (generating a titanium nitride active layer) and the construction of micro-nano composite structure can be achieved simultaneously in a single process step without additional nitriding treatment or structural modification steps. The process is simple and efficient, and the electrode preparation cycle is greatly shortened. Moreover, the titanium nitride active layer in the prepared electrode can form a metallurgical bond with the titanium matrix, and the bonding force is strong. The active layer is not easy to fall off or deactivate in long-term electrocatalytic reaction, thus effectively ensuring the long-term stability of PFOA degradation in complex water environments.

[0033] (5) By precisely controlling the power, scanning speed, and number of scans of the femtosecond laser, the morphology, depth and nitridation degree of the micro-nano composite structure can be flexibly controlled. The degradation performance of the electrode on different types of PFAS (per- and polyfluoroalkyl substances) can be optimized in a targeted manner. At the same time, it can also be adapted to the treatment needs of PFOA polluted water bodies with different concentrations and water qualities.

[0034] (6) This invention uses inexpensive and readily available commercial pure titanium sheets as the base material, without the need for precious metal doping or complex modification, which greatly reduces the cost of electrode raw materials. At the same time, the preparation process is simple and convenient to operate, and can be processed on a large scale. It solves the problem that existing high-efficiency PFOA degradation electrodes are expensive and difficult to apply industrially. It has broad application prospects in the fields of industrial wastewater treatment and polluted water body remediation.

[0035] (7) In this invention, the entire preparation process of the modified titanium electrode is carried out in a high-purity nitrogen atmosphere. No toxic or harmful chemical reagents are required. No pollutants such as wastewater, waste gas, or waste residue are discharged during the preparation process. This meets the green development requirements of environmental governance technology and is a typical environmentally friendly manufacturing technology. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the composite electrode fabrication system used in this invention; Figure 2 A scanning electron microscope (SEM) image of the modified titanium electrode A prepared in Example 1; Figure 3 is a SEM image of the modified titanium electrode B prepared in Example 2; Figure 4 is a SEM image of the modified titanium electrode C prepared in Example 3; Figure 5 is a SEM image of the modified titanium electrode D prepared in Example 4; Figure 6 The current response diagrams for electrode A prepared in Example 1 and blank titanium sheet in Comparative Example 1 in a mixed solution of 100 mg / L PFOA + 0.5 MH2SO4 are shown. Figure 7 The graph shows a comparison of the PFOA removal effects of electrode AG and blank electrode at 1h, 2h, and 3h.

[0037] Explanation of reference numerals in the attached diagram: 1. Laser; 2. Scanning galvanometer; 3. Atmosphere protection box; 4. Worktable; 5. Titanium substrate. Detailed Implementation

[0038] Embodiments of this disclosure will now be described with reference to specific examples. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of this disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of this disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure.

[0039] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0040] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0041] Example 1 This embodiment provides a method for the electrocatalytic degradation of perfluorooctanoic acid, which specifically includes the following steps: S1, Pre-processing; A 10mm × 30mm × 2mm commercially available pure titanium sheet was placed in acetone, anhydrous ethanol, and deionized water for ultrasonic cleaning for 15 minutes each to thoroughly remove surface oil, organic matter, and oxides. After cleaning, the surface of the titanium sheet was dried with 99.99% high-purity nitrogen gas to ensure its cleanliness, providing a good reaction substrate for the subsequent laser nitriding reaction and preventing impurities from affecting the formation of titanium nitride and the construction of micro / nano structures.

[0042] S2, femtosecond laser processing; The surface of the titanium sheet is modified using a femtosecond laser processing system. The femtosecond laser processing system in this embodiment is as follows: Figure 1As shown, it includes a laser 1, a scanning galvanometer 2, a worktable 4, and an atmosphere protection box 3. The laser emitted by the laser 1 is focused by the scanning galvanometer 2. The worktable 4 is located below the scanning galvanometer 2. The titanium sheet to be treated is placed on the worktable 4 through the atmosphere protection box 3 for laser modification treatment.

[0043] Specifically, the pretreated titanium substrate 5 is fixed in a sealed atmosphere protection box 3 and placed on a workbench 4. The atmosphere protection box 3 is then vented and continuously filled with high-purity nitrogen for 15 minutes. This process is repeated 3 times to ensure that the air in the atmosphere protection box 3 is fully replaced, forming a pure nitrogen reaction atmosphere and preventing impurities such as oxygen and water vapor from participating in the reaction.

[0044] A femtosecond laser processing system was used to modify the surface of a titanium sheet. The laser parameters were: center wavelength 1030 nm, pulse width 221 fs, repetition rate 200 kHz, and spot diameter 20 µm. A high-energy laser beam was focused onto the titanium sheet surface via an optical path system, with the average laser power set to 4.5 W, corresponding to a single pulse energy of 22.5 μJ. A computer numerical control platform and scanning galvanometer were used to control the laser focus to perform a continuous "Z"-shaped scan on the titanium sheet surface at a scanning speed of 150 mm / s, 12 scans, and a scanning line spacing of 100 μm. The scanning area was the bottom 1 cm. 2 The surface of the titanium sheet.

[0045] Reaction principle: The extremely high energy density of the femtosecond laser causes the surface of the titanium sheet to melt and vaporize instantly. The titanium atoms react with the nitrogen atoms in the nitrogen atmosphere to form a titanium nitride active layer. At the same time, the scanning ablation effect of the laser and the induced plasma effect work together to construct the designed micro-nano composite structure on the surface of the titanium sheet, thereby achieving the dual effect of one-step nitriding + structure construction.

[0046] S3, Post-processing; After laser scanning is completed, the sample is left to cool naturally to room temperature under a nitrogen atmosphere. Once cooled, the sample is removed and can be used directly as a PFOA degradation electrode, denoted as electrode A.

[0047] Figure 2 The image shown is a scanning electron microscope (SEM) image of the modified titanium electrode A prepared in Example 1. Figure 2 (a) is a low-power photograph showing the micrometer-scale trench array formed by laser scanning; (b) is a high-power photograph of a selected area in (a); (c) is a high-power photograph of a selected area in (b). Combined with... Figure 2The nanoscale particles and / or columnar structures distributed on the surface of the micron-grooves can be clearly displayed, directly confirming the successful construction of the micro-nano composite structure. Specifically, in this embodiment, the thickness of the titanium nitride active layer on the modified electrode surface is approximately 2 μm, the trench depth is approximately 10 μm, the spacing between adjacent trenches is approximately 67 μm, and the particle size of the nanoscale particles on the trench surface is 150-300 nm.

[0048] Comparative Example 1 A raw, untreated commercially available pure titanium sheet was used as a comparative example and designated as the blank titanium sheet.

[0049] Performance testing and results analysis: The modified titanium sheet electrode A and the blank titanium sheet electrode were used as working electrodes to test the PFOA degradation performance. The test conditions were as follows: substrate concentration 100 mg / L PFOA, electrolyte 0.5 mol / L H2SO4, counter electrode Pt sheet, voltage range -0.5V~2V (vs. Ag / AgCl), reaction time 30s, O2 flow rate 2mL / min, and effective electrode area 1cm².

[0050] (1) Morphology and composition: such as Figure 2 As shown, a regular array of micron-sized trenches was formed on the surface of electrode A, and the trenches contained abundant nano-sized particles and columnar structures, successfully constructing a micro-nano composite structure. This structure can significantly increase the specific surface area of ​​the electrode, providing sufficient active sites for PFOA adsorption and degradation, and the trench structure is conducive to the desorption of bubbles.

[0051] (2) Activity test of modified titanium sheet electrode A: In 0.5 mol / L H2SO4 electrolyte and 0.5 mol / L H2SO4 mixed electrolyte containing 100 mg / L PFOA, the absolute value of the peak reduction current of the blank titanium sheet electrode was about 180 mA, while the peak reduction current of electrode A in pure electrolyte was about 200 mA, and the peak reduction current in electrolyte containing PFOA was as high as 310 mA, and the reduction onset potential was lower, about 0.21 V vs. Ag / AgCl. The activity of modified titanium sheet electrode A was significantly higher than that of the blank titanium sheet.

[0052] (3) Electrochemical characteristics: The step current response results are as follows Figure 6As shown in Figure a, the absolute value of the peak current of the blank titanium sheet electrode is only about 2 mA, with a low current density and no obvious trend of activity improvement during long-term testing, indicating that its electron transfer efficiency is low and it is difficult to effectively activate PFOA molecules. In contrast, the absolute value of the peak current of electrode A reaches about 5 mA, with a significantly higher current density. The current changes actively in the early stage of the test, indicating that PFOA is rapidly adsorbed and activated, and can maintain a high current density for a long time. The DC current response also shows that the modified titanium sheet electrode A has a higher current density under the same test time. Both of these factors indicate that electrode A has high electron transfer efficiency, better reactivity and stability during PFOA degradation, and a significant improvement in overall electrochemical performance.

[0053] (4) Removal effect of perfluorooctanoic acid (PFOA): The removal effect of PFOA is as follows Figure 7 As shown, under the same time conditions, the modified titanium electrode A showed a significantly higher PFOA removal rate than the blank electrode at 1h, 2h, and 3h, indicating that the modified electrode of the present invention can effectively improve the removal rate of perfluorooctanoic acid (PFOA).

[0054] Example 2 The difference between this embodiment and Embodiment 1 lies only in the adjustment of parameters in the femtosecond laser processing steps: the number of laser scans is reduced to 3, the scanning speed is increased to 300 mm / s, and other conditions are exactly the same as in Embodiment 1. The resulting electrode is denoted as electrode B. Figure 3 As shown, compared with electrode A, SEM observation reveals that the micron-grooves on the surface of electrode B are shallower, and the surface has fewer protruding nanostructures and less roughness, forming a parallel micron-scale groove array with a width of about 30-40 μm, a depth of about 6 μm, and a spacing of about 58 μm between adjacent grooves. The radial dimension of the nanostructure is about 150-180 nm.

[0055] Example 3 The difference between this embodiment and Embodiment 1 lies only in the adjustment of parameters in the femtosecond laser processing step: the number of laser scans is reduced to 6, the scanning speed is reduced to 50 mm / s, and other conditions are exactly the same as in Embodiment 1. The resulting electrode is denoted as electrode C. Figure 4 As shown, compared with electrode A, SEM observation revealed that the nanopillars in the micro-grooves on the surface of electrode C are coarser, the nanostructures protruding on the surface are coarser in size and have poorer uniformity of distribution, forming a parallel micron-scale groove array with a width of about 40–60 μm, a depth of about 12 μm and a spacing of about 61 μm between adjacent grooves. The radial size of the nanostructure is about 250–300 nm, and there are local coarsening and resolidification structures.

[0056] Example 4 The main difference between this embodiment and Embodiment 1 is that, by controlling the femtosecond laser scanning process, a micro-nano composite structure composed of a cross-shaped micron-scale groove array and a titanium nitride nanostructure is formed on the titanium nitride active layer.

[0057] Specifically, in this embodiment, during femtosecond laser processing, the laser beam is focused onto the surface of the titanium sheet via an optical path system. The average laser power is set to 4.5 W, corresponding to a single pulse energy of 22.5 μJ. The computer numerical control platform and scanning galvanometer are controlled to first perform a strip-like parallel scan along the X direction of the titanium sheet surface, and then a cross-strip scan along the Y direction perpendicular to the X direction, forming a regularly distributed array of cross-shaped micron-grooves. The X and Y directions are scanned six times each, for a total of 12 scans; the scanning speed is 150 mm / s; the spacing between adjacent co-directional cross-grooves is approximately 90 μm. Each groove consists of two parallel filling scan lines, with a spacing of 10 μm between adjacent filling scan lines.

[0058] Combination Figure 5 As shown, after processing with the above parameters, a cross-shaped micro-groove network with a width of 30 μm, a spacing of about 90 μm, and a depth of about 12 μm is formed in the effective area of ​​1 cm² at the bottom of the titanium sheet; at the same time, nanoscale particles and columnar rough structures are formed at the bottom of the groove, the sidewall of the groove, and the adjacent protrusion area. The radial dimension of the titanium nitride nanostructure is 180-200 nm.

[0059] Post-processing: After laser scanning, the sample was allowed to cool naturally to room temperature under a nitrogen atmosphere. Once cooled, it was removed, yielding a cross-shaped micro / nano composite titanium nitride electrode for PFOA electrocatalytic degradation, denoted as electrode D.

[0060] Example 5 The main difference between this embodiment and embodiment 4 is that the average laser power is set to 3.5 W in this embodiment, corresponding to a single pulse energy of 17.5 μJ.

[0061] Simultaneously, during laser scanning, the X and Y directions were scanned four times each, for a total of eight scans; the scanning speed was 220 mm / s; the center-to-center distance between adjacent co-directional cross grooves was 200 μm. Each groove consisted of three parallel filling scan lines, with an adjacent filling scan line spacing of 20 μm. After processing with the above parameters, a cross-shaped microgroove network with a width of approximately 60 μm and a depth of approximately 6 μm was formed within a 1 cm² effective area at the bottom of the titanium sheet; the radial dimension of the titanium nitride nanostructures inside the grooves was 120-150 nm.

[0062] The cross-shaped micro / nano composite structure modified titanium nitride electrode obtained in this embodiment is denoted as electrode E. Compared with electrode D obtained in Example 4, electrode E has a smaller width and depth of cross-shaped groove, relatively limited surface open channels, and a relatively weaker degree of development of nano-rough structure.

[0063] Example 6 The main difference between this embodiment and embodiment 4 is that the average laser power is set to 5.0 W in this embodiment, corresponding to a single pulse energy of 25.0 μJ.

[0064] Simultaneously, during laser scanning, the X and Y directions are scanned 8 times each, for a total of 16 scans; the scanning speed is 100 mm / s; the center-to-center distance between adjacent unidirectional cross grooves is 200 μm. Each groove consists of 7 parallel filling scan lines, with an adjacent filling scan line distance of 16.7 μm.

[0065] After processing with the above parameters, a cross-shaped micro-groove network with a width of about 120 μm and a depth of about 18 μm is formed in the effective area of ​​1 cm² at the bottom of the titanium sheet; relatively abundant nanoparticles, columnar rough structures and local resolidification morphology are formed in the inside of the grooves, sidewalls and adjacent protrusions; the radial size of the titanium nitride nanostructure is about 225-250 nm.

[0066] The cross-shaped micro / nano composite structure modified titanium nitride electrode obtained in this embodiment is denoted as electrode F. Compared with electrode D obtained in Example 4, the width and depth of the cross-shaped groove of electrode F are further increased. Comparative Example 2 In this comparative example, the pretreated titanium sheet was directly placed in a nitrogen-protected environment for surface nitriding treatment, resulting in a continuous titanium nitride modified layer on the surface of the titanium sheet. However, no additional regular micron-scale trench array was constructed, nor were obvious nano-column structures or nanoparticle rough structures formed. After the treatment, a titanium nitride electrode with a titanium nitride layer on the surface and a relatively smooth overall morphology was obtained, denoted as electrode G.

[0067] Combination Figure 7It can be seen that, under the same time conditions, the removal rate of PFOA by electrode AG is higher than that of the blank electrode at 1h, 2h, and 3h. Although the titanium nitride layer on the surface of electrode G can improve the conductivity and chemical stability of the titanium substrate to a certain extent, its effective reaction area, exposure degree of active sites, and solid-liquid interface mass transfer capacity are still limited due to the lack of micron-level open channels and nano-level active structures. The modified electrode of this invention can further improve the electrocatalytic degradation effect of PFOA through the combined effect of the micro-nano composite structure on the surface of the titanium nitride active layer. At the same time, the process parameters of the femtosecond laser, especially the scanning speed, number of scans, and laser power, will affect the distribution of the micro-nano composite structure, such as the width and depth of the micron-level trenches and the size of the nano-titanium nitride structure, thereby affecting the electrocatalytic degradation effect of PFOA. Moreover, the cross-shaped groove structure has a better improvement effect than the simple parallel and spaced groove structure.

[0068] In summary, this invention modifies the surface of titanium sheets through a one-step femtosecond laser process in a nitrogen atmosphere. This process simultaneously forms a titanium nitride active layer on the surface and fabricates numerous micron-sized trenches and cauliflower-shaped nanoparticles, successfully preparing a high-performance, highly stable electrode for PFOA degradation. Furthermore, this invention features a simple, environmentally friendly, and highly controllable fabrication process, along with low electrode cost, high degradation efficiency, and good stability. It has broad industrial application prospects in areas such as the treatment of polluted water bodies containing perfluorooctanoic acid (PFOA) and industrial wastewater treatment.

Claims

1. A method for the electrocatalytic degradation of perfluorooctanoic acid, characterized in that, include: Electrocatalytic degradation of perfluorooctanoic acid was performed using a modified titanium electrode as the working electrode. The modified titanium electrode includes a titanium substrate and a titanium nitride active layer on the surface of the titanium substrate. The titanium nitride active layer has a micro-nano composite structure distributed on it. The micro-nano composite structure includes a micron-scale groove array on the titanium nitride active layer and titanium nitride nanostructures distributed in the grooves.

2. The electrocatalytic degradation method for perfluorooctanoic acid according to claim 1, characterized in that, The micron-scale groove array is distributed in parallel intervals or in a cross-shaped pattern; and / or the titanium nitride nanostructure is a nanocolumnar structure, a nanoparticle structure, or a combination of both.

3. The electrocatalytic degradation method for perfluorooctanoic acid according to claim 2, characterized in that, The groove width of the micron-scale groove array is 30-120 μm, the groove depth is 6-18 μm, and the radial dimension of the titanium nitride nanostructure is 150-300 nm.

4. The electrocatalytic degradation method for perfluorooctanoic acid according to claim 2 or 3, characterized in that, Titanium nitride nanostructures are also distributed on the protrusions between adjacent grooves.

5. The electrocatalytic degradation method for perfluorooctanoic acid according to any one of claims 1-3, characterized in that, The thickness of the titanium nitride active layer is 2-4 μm.

6. A modified titanium electrode for the electrocatalytic degradation of perfluorooctanoic acid, characterized in that, The modified titanium electrode includes a titanium substrate and a titanium nitride active layer on the surface of the titanium substrate. The titanium nitride active layer has a micro-nano composite structure distributed on it. The micro-nano composite structure includes a micron-scale groove array on the titanium nitride active layer and titanium nitride nanostructures distributed in the grooves.

7. A method for preparing a modified titanium electrode for the electrocatalytic degradation of perfluorooctanoic acid, characterized in that, include: A titanium matrix is ​​provided, and the titanium matrix is ​​pretreated to remove contaminants from the matrix surface; Under a nitrogen atmosphere, a femtosecond laser is used to modify the pretreated titanium substrate to form a titanium nitride active layer on its surface, and a micro-nano composite structure is simultaneously constructed on the titanium nitride active layer. The micro-nano composite structure includes a micron-scale groove array on the titanium nitride active layer and titanium nitride nanostructures distributed within the grooves.

8. The method for preparing the modified titanium electrode for electrocatalytic degradation of perfluorooctanoic acid according to claim 7, characterized in that, The process parameters of the femtosecond laser include: a center wavelength of 900-1100nm, a pulse width of 100-500fs, a repetition frequency of 100-500kHz, and a spot diameter of 10-50μm.

9. The method for preparing the modified titanium electrode for electrocatalytic degradation of perfluorooctanoic acid according to claim 7, characterized in that, When modifying a pretreated titanium substrate using a femtosecond laser, the scanning galvanometer is controlled to make the laser focus scan along a preset "Z" shaped path. The process parameters during scanning include: average laser power 3.5-5 W, scanning speed 50-300 mm / s, and 3-16 scans.

10. The method for preparing a modified titanium electrode for the electrocatalytic degradation of perfluorooctanoic acid according to any one of claims 7-9, characterized in that, Also includes: The modified sample was placed in a nitrogen atmosphere and naturally cooled to room temperature to obtain the modified titanium electrode for electrocatalytic degradation of perfluorooctanoic acid.

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