Method for roughening the surface of a coated titanium electrode base and use thereof

Abstract

The application discloses a rough titanium substrate and a preparation method and application thereof, and the preparation method comprises the following steps: cutting an initial titanium sheet and then performing alkali washing and oil removal treatment to obtain a cut titanium sheet; a double electrode system is formed by taking NaBr as an electrolyte, taking the cut titanium sheet as a working electrode, and taking the initial titanium sheet as a counter electrode; the double electrode system is electrified; first, a constant current of 180 mA·cm ‑2 Once etching is performed on the cut titanium sheet, and then the constant current of 500 mA·cm ‑2 Second etching is performed on the cut titanium sheet to obtain the rough titanium substrate. The rough titanium substrate obtained through electrochemical etching has higher electrocatalytic activity and electrochemical active area under the condition of the same active oxide load, and the rough titanium substrate prepared by the application is more beneficial to the adhesion of a coating and the stability of an electrode.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coated titanium electrode, in particular to a roughening method of coated titanium electrode substrate surface and application. BACKGROUND

[0002] The titanium substrate roughened can form a concave-convex surface, which has a larger surface area and can remove the surface oxide film, thereby improving the electrochemical performance of the electrode. The commonly used roughening treatment method is generally acid treatment, and different etching treatment methods have a great influence on the surface morphology and performance of the titanium substrate. For example, 10% H2C2O4 is used for treatment for 2-3h under micro-boiling conditions, 20% H2SO4 solution is used for treatment for 2-3h at 95℃ or above, and 30% HCl can also be used for treatment for 2-3h at 90℃ or above. The advantage of oxalic acid treatment compared with other acids is that the surface structure of the product titanium substrate is stable and can be stored for several days in the air. In addition, no toxic and harmful substances are generated during the experiment, which is green and safe, so oxalic acid etching is widely used in the research of various titanium anodes. However, a large amount of oxalic acid is required when using oxalic acid, which leads to high cost.

[0003] The surface morphology of the titanium substrate can affect the crystal type and crystallization amount of the coated oxide, thereby affecting the electrocatalytic activity of the coated titanium anode. A suitable surface morphology can also improve the adhesion of the oxide coating to the substrate, and good adhesion is beneficial to improve the service life of the electrode. In order to compare the influence of titanium substrate surface treatment on the performance and service life of titanium anode, this study compares the titanium anodes treated by oxalic acid, electrochemical treatment and without roughening treatment, aiming to explore the influence of different pretreatment methods on the morphology of titanium substrate, and further compare the electrochemical performance and electrolysis life of the titanium anodes prepared by them. SUMMARY

[0004] In view of the shortcomings of the prior art, the purpose of the present application is to provide a roughening method of coated titanium electrode substrate surface and application, which aims to solve the problems of poor surface roughness of the existing titanium substrate, poor electrochemical performance of the titanium anode prepared from the titanium substrate and poor electrolysis life.

[0005] The technical scheme of the present application is as follows:

[0006] A roughening method of coated titanium electrode substrate surface, comprising the following steps:

[0007] After the initial titanium sheet is cut, it is subjected to alkali washing and oil removal treatment to obtain a cut titanium sheet;

[0008] A double-electrode system is formed by using NaBr as an electrolyte, using the cut titanium sheet as a working electrode and using an initial titanium sheet as a counter electrode, and the double-electrode system is powered on. First, a constant current of 180mA·cm -2The cutting titanium sheet is etched once, and then the constant current 500 mA·cm -2 The cutting titanium sheet is etched twice to obtain the surface roughened coated titanium electrode base.

[0009] The surface roughening method of the coated titanium electrode base, wherein the size of the cutting titanium sheet is 10 mm x 15 mm x 0.2 mm or 10 mm x 20 mm x 0.2 mm.

[0010] The surface roughening method of the coated titanium electrode base, wherein the cutting of the initial titanium sheet is followed by alkali washing and oil removal treatment, comprising:

[0011] Na3PO4·12H2O, Na2CO3, NaOH are dissolved in deionized water in a mass ratio of 105:25:4 to prepare 0.3% alkali washing and oil removal liquid, and heated to boiling for standby;

[0012] After the initial titanium sheet is cut, it is added to the boiling alkali washing and oil removal liquid and kept for a predetermined time;

[0013] After the initial titanium sheet is taken out, it is rinsed with deionized water and ultrasonically cleaned in deionized water to complete the alkali washing process, and the cutting titanium sheet is obtained.

[0014] The surface roughening method of the coated titanium electrode base, wherein the predetermined time is 40-80 min.

[0015] The surface roughening method of the coated titanium electrode base, wherein after the cutting titanium sheet is etched twice, it further comprises:

[0016] The flocculent impurities on the surface of the cutting titanium sheet are removed by using an ultrasonic cleaning machine, and then the cutting titanium sheet is cleaned with acid etching liquid for 1-2 min;

[0017] Then, the cutting titanium sheet is rinsed with deionized water for 3-4 times, and finally rinsed with ethanol once, and the cleaned rough titanium base is stored in anhydrous ethanol and standby.

[0018] A coated titanium electrode base, characterized in that it is prepared by the surface roughening method of the coated titanium electrode base.

[0019] Application of a coated titanium electrode base, wherein the coated titanium electrode base is used to prepare a coated titanium electrode.

[0020] Beneficial effects: the present application carries out electrochemical test after preparing the titanium substrate prepared by EE (electrochemical etching), CE (chemical etching) and NE (non-etching) into a coated titanium electrode respectively, and the results show that whether the roughening of the titanium substrate has a great influence on the OER performance, and also affects the stability of the coated titanium electrode; the titanium anode prepared by the titanium substrate without roughening has lower catalytic activity and poorer service life; the rough titanium substrate obtained by electrochemical etching has higher electrocatalytic activity and electrochemical active area under the same active oxide load; through the strengthening electrolysis life experiment and the electrode failure diagram, it can be speculated that appropriate etching directly affects the service life of the electrode, the protruding titanium of the CE electrode is more likely to protrude the coating due to the relatively sharp protruding peaks of the micro-morphology of the titanium substrate, and the electrolyte is more likely to invade the titanium substrate to cause the corrosion and oxidation of the substrate; and the EE electrode has longer strengthening electrolysis life due to the larger hilly undulation and higher roughness of the surface, which shows that the electrochemical etching is more conducive to the adhesion of the coating and the stability of the electrode. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a surface roughening method flow chart of a coated titanium electrode substrate of the present application.

[0022] Figure 2 In a and b, SEM images of the oxalic acid treated titanium substrate and the coating are respectively shown; in c and d, SEM images of the electrochemically treated titanium substrate and the coating are respectively shown; in e and f, SEM images of the titanium substrate without roughening treatment and the coating are respectively shown.

[0023] Figure 3 In a, XRD images of the titanium substrates prepared by different pretreatment methods are shown; in b, XRD images of the coated titanium anodes prepared by different pretreatment methods are shown.

[0024] Figure 4 In a, polarization curve images of the coated titanium anodes with different pretreatments are shown; in b, Tafel curve images of the coated titanium anodes with different pretreatments are shown.

[0025] Figure 5 In a, cyclic voltammetry curve images of the coated titanium anodes with different pretreatments are shown; in b, voltammetry charge images of the coated titanium anodes with different pretreatments are shown.

[0026] Figure 6 It is the chronoamperometry of the coated titanium anodes with different pretreatments.

[0027] Figure 7 In a, EIS images of the titanium anodes with different pretreatments are shown; in b, EIS fitting images and equivalent circuit images of the electrochemically etched titanium anode are shown.

[0028] Figure 8 It is the change curve of the cell voltage of the electrochemically and chemically pretreated anodes with the electrolysis time.

[0029] Figure 9 The figure of the reinforced electrolysis life results of different pretreated anodes.

[0030] Figure 10 Wherein, a, b and c are respectively the EE electrode failure figure, the CE electrode failure figure and the NE electrode failure figure. DETAILED DESCRIPTION

[0031] The application provides a surface roughening method of a coated titanium electrode substrate and application, in order to make the purpose, technical scheme and effect of the application more clear and definite, the application is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the application and not to limit the application.

[0032] Figure 1 A surface roughening method of a coated titanium electrode substrate provided by the application is shown in the flow chart, which comprises the following steps:

[0033] S10, after the initial titanium sheet is cut, the alkali washing and oil removal treatment are performed, so that the cut titanium sheet is prepared;

[0034] S20, a double electrode system is formed by taking NaBr as an electrolyte, taking the cut titanium sheet as a working electrode and taking an initial titanium sheet as a counter electrode, the double electrode system is powered on, first, a constant current of 180 mA·cm -2 The cut titanium sheet is etched once, and then a constant current of 500 mA·cm -2 The cut titanium sheet is etched twice, so that the surface-roughened coated titanium electrode substrate is prepared.

[0035] The application performs electrochemical testing on the coated titanium electrode prepared by the titanium substrate prepared by EE (electrochemical etching), CE (chemical etching) and NE (non-etching) respectively. It is found that whether the titanium substrate is roughened or not has a great influence on the OER performance and also affects the stability of the coated titanium electrode. The titanium anode catalytic activity prepared by the titanium substrate without roughening is low, and the service life is poor. The rough titanium substrate obtained by electrochemical etching has higher electrocatalytic activity and electrochemical active area under the same active oxide load. Through the reinforced electrolysis life experiment and the electrode failure figure, it can be inferred that appropriate etching directly affects the service life of the electrode. The CE electrode has relatively sharp protruding peaks in the micro-morphology of the titanium substrate, which causes the protruding titanium to protrude more easily, and the electrolyte is more likely to invade the titanium substrate, resulting in substrate corrosion and oxidation. The EE electrode has larger hilly undulations and higher roughness on the surface, which can maintain a longer reinforced electrolysis life, indicating that electrochemical etching is more conducive to the adhesion of the coating and the stability of the electrode.

[0036] In some embodiments, the size of the cut titanium sheet is 10mm x 15mm x 0.2mm or 10mm x 20mm x 0.2mm, but is not limited thereto.

[0037] In some embodiments, after the initial titanium sheet is cut, the titanium sheet is subjected to alkali washing and oil removal treatment, including: dissolving Na3PO4·12H2O, Na2CO3 and NaOH in deionized water at a mass ratio of 105:25:4 to prepare 0.3% alkali washing and oil removal liquid, and heating to boiling for standby; after the initial titanium sheet is cut, the titanium sheet is added to the boiling alkali washing and oil removal liquid and kept for 40-80min; after the initial titanium sheet is taken out, the titanium sheet is rinsed with deionized water and subjected to ultrasonic cleaning treatment in deionized water to complete the alkali washing process, thereby obtaining the cut titanium sheet.

[0038] In some embodiments, after the cut titanium sheet is subjected to secondary etching, the method further includes: removing flocculent impurities on the surface of the cut titanium sheet by using an ultrasonic cleaning machine, and then cleaning the cut titanium sheet with acid etching liquid for 1-2min; then rinsing the cut titanium sheet with deionized water for 3-4 times, and finally rinsing the cut titanium sheet with ethanol once, so as to obtain the cleaned rough titanium substrate which is stored in anhydrous ethanol for standby.

[0039] In some embodiments, a coated titanium electrode substrate is provided, which is prepared by the surface roughening method of the coated titanium electrode substrate.

[0040] In some embodiments, the coated titanium electrode substrate is used to prepare a coated titanium electrode.

[0041] The surface morphology of the titanium substrate can affect the crystal type and crystallization amount of the coated oxide, thereby affecting the electrocatalytic activity of the coated titanium anode. A suitable surface morphology can also improve the adhesion of the oxide coating to the substrate, and good adhesion is conducive to improving the service life of the electrode. In order to compare the influence of the titanium substrate on the performance and service life of the titanium anode, the present application compares the titanium substrates treated by oxalic acid, electrochemical treatment and without roughening treatment, in order to explore the influence of different pretreatment methods on the morphology of the titanium substrate, and further compare the electrochemical performance and reinforced electrolysis life of the titanium anodes prepared by them.

[0042] Example 1

[0043] A surface roughening method of a coated titanium electrode substrate includes the following steps:

[0044] The electrochemical etching uses 1mol·L -1 NaBr as the electrolyte, and a N8352D direct current power supply of Enzhi is used as the power supply; the cut titanium sheet is used as the working electrode, a large-area titanium sheet is used as the counter electrode to form a two-electrode system, and the magnetic stirring speed is 800rpm; the constant current is 180mA·cm -2After a while, 500 mA-cm -2 After etching for a while, two-stage electrochemical etching was completed; the surface flocculation impurities were removed by using an ultrasonic cleaning machine, and then the titanium substrate was cleaned with acid etching solution (1% HF + 10% HNO3) for 1-2 min, rinsed with deionized water for 3-4 times, and finally rinsed with ethanol once. The cleaned rough titanium substrate was stored in anhydrous ethanol and used as needed.

[0045] Comparative Example 1

[0046] A method for roughening the surface of a coated titanium electrode substrate, comprising the steps of:

[0047] The chemical etching solution was 10% H2C2O4. The cut TA2 titanium sheet was placed in the acid etching solution and heated to a micro-boiling state in a water bath for 2-3 h to obtain a chemically etched titanium substrate. The titanium substrate was rinsed with deionized water for 3 times, ultrasonically cleaned in deionized water for 10 min, and finally the prepared rough titanium substrate was placed in anhydrous ethanol for standby. The principle of chemical etching is that a micro-battery is formed on the titanium sheet in the etching solution. In the hot oxalic acid solution, the titanium oxide on the surface of the titanium sheet is first reacted, and then the colorless transparent solution gradually changes to brown turbid solution, which indicates that the anode undergoes oxidation reaction: Ti→Ti 3+ +3e, which causes the oxalic acid solution to change from colorless to brown, and the cathode undergoes reduction reaction: 2H + +2e→H2. The surface of the etched titanium sheet no longer has a gray metallic luster, but appears gray and rough.

[0048] Example 2

[0049] The rough titanium substrates in Example 1 and Comparative Example 1 were prepared into coated titanium anodes by the following method:

[0050] In the experiment of preparing titanium anodes by thermal decomposition method, if the metal salt particles in the coating solution are insoluble or unevenly dispersed, it will directly affect the surface morphology and crystallization of the oxide coating, thereby changing the electrochemical performance of the electrode. Therefore, in this example, the tantalum source in the coating solution is a tantalum ethoxide solution, the iridium source is H2IrCl6·6H2O, and the solvent is n-butanol, which is configured into a coating precursor solution with an iridium-tantalum molar ratio of 7:3. The prepared coating precursor solution is brushed onto the surface of the rough titanium substrate prepared in different ways using a fine brush. The brushed rough titanium substrate is placed under an infrared lamp for baking for 30 s until there is no visible solvent on the surface. Then the preliminarily dried rough titanium substrate is placed in a drying oven for further drying at 100℃ for 10 min, which aims to evaporate the solvent to prevent the coating from being combined loosely due to the sintering process. The completely dried titanium sheet is placed in a low-temperature muffle furnace and heated at a sintering temperature of 500℃ for 10 min to fully oxidize the coating, and the program heating rate is 10℃·min -1The coating liquid is repeatedly applied until the coating liquid is applied completely, and the last coating is sintered at the same temperature rising rate, and the holding time at 500℃ is changed to 60min, the coating of the oxide active layer is completed, and the coated titanium anode is prepared.

[0051] 1. Phase and micro-morphology characterization:

[0052] The titanium substrate after roughening treatment presents a certain pitted surface state, and too shallow or too deep will affect the quality of the coating. If the surface pits of the substrate are too deep, the coating liquid and the coating are easy to pile up in the pits, resulting in less oxide covering the higher protruding part, and the titanium substrate at this part is more easily corroded and oxidized by the electrolyte; if the surface pits are too shallow, the adhesion of the coating to the substrate is weak, and the coating is easy to fall off, which also leads to shorter service life of the titanium anode. The suitable rough surface combined with the subsequent process can more favorably play the catalytic activity of the active layer, and is also more conducive to the combination of the coating and the improvement of the service life. The catalytic activity and stability of three kinds of titanium substrates with different surface morphologies prepared by the present application are compared, and it is found that different micro-morphologies have a great influence on the oxygen evolution activity and the strengthening electrolysis life of the electrode, especially on the stability of the electrode and the adhesion of the coating.

[0053] The titanium sheet is treated by chemical etching and electrochemical etching, and an iridium-tantalum coating is applied to obtain a chemical etching titanium anode (CE) and an electrochemical etching titanium anode (EE), which are compared with a titanium anode without etching (NE) in performance. First, the influence of etching on the micro-morphology of the titanium substrate is explored by SEM characterization, Figure 2 In a, the surface morphology of the titanium substrate without any etching, the surface of the TA2 titanium plate is smooth, which is very unfavorable for the adsorption of the coating, and is easy to cause the coating to fall off, thereby having a great influence on the service life. Figure 2 In b, the SEM image of the titanium substrate after coating with an iridium-tantalum oxide coating, it can be observed that the coating does not appear the classic mud crack path, which may be due to the low amount of metal coating and the thin coating. However, the surface coating has poor crystallinity, and the smooth surface is easy to cause the coating to fall off, which ultimately leads to lower service life.

[0054] The surface of the new titanium substrate after oxalic acid chemical etching is composed of a large number of pits (as shown in Figure 2 c), the roughness is obviously higher than that of the titanium substrate without any etching, however, there are a large number of sharp peaks on the edge of the pits, and the higher sharp peaks of the titanium substrate are more likely to protrude the oxide coating, leading to the invasion of the electrolyte and the corrosion of the titanium substrate, thereby reducing the service life of the titanium electrode. Figure 2 d is obtained by coating the chemically etched titanium substrate, and the surface roughness of the coated titanium anode is still high. This rough micro-morphology can provide more active sites, i.e. good electrocatalytic activity, and can reduce the falling off.

[0055] The titanium sheets obtained by electrochemical etching have an undulating, hilly surface (such as...). Figure 2 As shown in Figure e), this design ensures a larger number of active sites, a more uniform roughness distribution which is more conducive to the adhesion of the oxide coating, and gentler peak-valley undulations which are more beneficial for protecting the titanium substrate from electrolyte infiltration and subsequent oxidation failure. Figure 2 As can be seen from the SEM images, the coating covers the titanium substrate well, with a rough and undulating surface. Furthermore, compared to the chemically etched titanium anode, the coating distribution on its surface is more uniform. These SEM characterization results indicate that electrochemical etching can not only facilitate coating adhesion but also more effectively protect the titanium substrate.

[0056] The surface roughness of the titanium substrate and coating was tested using a roughness tester to further investigate the effects of chemical etching and electrochemical etching on the substrate surface. Table 1 shows that the electrochemically etched titanium substrate had the highest roughness Ra = 2.522 μm, while the roughness of the chemically etched titanium substrate (Ra = 1.674 μm) was also significantly higher than that of the untreated titanium substrate (Ra = 0.112 μm). After coating with an oxide layer, the roughness of all samples decreased, but the EE sample still had the highest roughness (Ra = 2.368 μm). This indicates that, for the same area, the electrochemically etched titanium substrate implies a larger actual surface area and also possesses more active sites.

[0057] Table 1 Surface roughness of titanium substrates and coatings under different pretreatment methods

[0058]

[0059] 2. Phase analysis of titanium substrate and coating

[0060] XRD analysis was used to investigate the phase composition of titanium substrates with different pretreatments. Figure 3 As can be easily seen from the XRD patterns of the titanium substrates shown in Figure a, all three samples exhibit characteristic diffraction peaks of titanium. The oxalic acid-treated titanium substrate shows an additional characteristic peak of titanium hydride, which is attributed to the presence of residual titanium hydride on the substrate surface after the oxalic acid etching reaction. This indicates that the main components of the titanium substrate were not altered during chemical or electrochemical etching, and all samples exist in the form of elemental titanium.

[0061] Figure 3Figure 3 shows XRD patterns of titanium anodes with applied IrTa oxide coating. After applying IrTa oxide coating on roughened titanium substrates, the XRD characteristic peaks of the coated titanium anodes from different roughening methods were compared. It was found that the IrO2 diffraction peaks appeared at 27.5°, 34.6° and 53.6° of 2θ, respectively. Since the metal oxide coating was thin and the X-ray penetration ability was strong, the diffraction peaks of the titanium substrate after applying the coating were still obvious. The IrO2 peaks of the oxalic acid treated coated titanium anode were not sharp, while the IrO2 peaks of the other two samples were relatively narrow and had higher intensity, indicating that the rutile phase IrO2 on the electrochemically etched and unetched titanium substrates had better crystallinity. At this sintering temperature, Ta2O5 was basically amorphous

[93] , so there were no characteristic peaks in the XRD pattern. It was also found that the titanium hydride peak of the oxalic acid treated titanium substrate had disappeared, which was due to the decomposition of the titanium hydride layer during high temperature sintering.

[0062] 3. Electrochemical characterization

[0063] By testing the OER performance and stability of the titanium anode, the potential of the titanium anode for use in the electrolytic copper foil industry was explored. Electro-catalytic activity is a main parameter for evaluating electrode performance and directly affects the energy consumption and efficiency of the reaction. Since the consumed electric energy of the anode reaction in the oxygen evolution environment accounts for about 50-60%, the current density of the oxygen evolution reaction at a certain potential is often compared to compare the electro-catalytic activity of different anodes. EE, CE, and NE titanium anodes were used as working electrodes in a three-electrode system, and the electrolyte was 0.5 mol·L -1 H2SO4, with a scan rate of 1 mV·s -1 . Figure 4 Figure 4 shows the polarization curves of the coated titanium anodes obtained under different pretreatments. It can be seen that within the potential range of 1-2 V, the titanium anode obtained by electrochemical etching has a higher current density than the commonly used chemical etching and unetched titanium substrate. The EE anode requires a lower potential to reach the same current density, indicating that the titanium substrate obtained by electrochemical etching has higher electro-catalytic activity. At 1.3 V-1.4 V, the curves of the NE anode and the CE anode are almost coincident, but above 1.4 V, the current density of the unetched titanium anode gradually decreases. By comparing the electro-catalytic OER performance of EE, CE, and NE, it can be inferred that electrochemical etching is more conducive to the catalytic performance of the iridium tantalum oxide coating.

[0064] Figure 4The Tafel slope curve obtained by linear fitting is shown in FIG. b, and the abscissa is the logarithm of the current density. The figure can more intuitively indicate the size of the catalytic activity by the size of the slope value. The oxygen evolution activity of the electrode is closely related to the pretreatment method of the electrode surface, thereby causing the formation and arrangement of the crystals in the active layer to be different. A large Tafel slope value represents that the electron transfer process in the oxygen evolution reaction of the electrode is slow, which indicates poor oxygen evolution performance. The Tafel value of EE is 129.7 mV·dec -1 , the Tafel value of CE is 140.4 mV·dec -1 , and the Tafel value of NE is 161.0 mV·dec -1 . The oxygen evolution activity reflected by the Tafel value is consistent with the LSV curve trend in FIG. a. The coated titanium anode obtained by electrochemical etching has the highest electrocatalytic activity, the chemical etching is the second, and the titanium plate without etching has the worst activity. Figure 4

[0065] 4. Cyclic voltammetry and electrocatalytic activity

[0066] The catalytic activity and electrochemical active area of the titanium anode can be tested by cyclic voltammetry. Figure 5 FIG. a shows the CV curves of the coated titanium anode under different pretreatments. The curve shown in the figure includes the area reflecting the size of the voltammetric quantity, and the voltammetric quantity is directly related to the electrochemical active area of the coating. Therefore, the value of the voltammetric quantity can represent the size of the active area of the coated anode surface. During the brushing process, the dispersion of the coating liquid brushed on the different surfaces will be directly affected by the surface morphology of the titanium substrate, thereby affecting the crystallization of the coating oxide. Therefore, under the same coating amount, the cyclic voltammetric quantities of the anodes with different roughness treatments are different. From Figure 5 FIG. b, it can be obtained that the voltammetric quantity value EE>CE>NE, the voltammetric quantities of EE and CE are higher, and the voltammetric quantity of the NE titanium anode is the lowest, which is only 49.1% of the electrode CE and 33.6% of EE after etching treatment of the titanium substrate. From Figure 5 FIG. a, it can be clearly seen that the EE sample contains the largest area, which indicates that the catalytic active area is higher than that of other anodes. The reason may be that the sample obtained by electrochemical etching has higher roughness and larger real surface area, so it has more active sites.

[0067] 5. Chronoamperometry:

[0068] Chronoamperometry is used to record the current density value at a constant potential for a period of time, so as to explore the electrochemical stability of EE, CE and NE electrodes. Figure 6 ​For the chronopotentiometry curve at 1.4 V potential, the trend of the chronopotentiometry curve of the coated titanium anode prepared under EE and CE roughness is basically the same, indicating that similar electrode reactions occur. The coated titanium anode without any roughening treatment, i.e. NE electrode, tends to be stable after a large number of values are attenuated at 100 s, indicating that its electrochemical stability is not as good as EE and NE. The current density after the chronopotentiometry is stable and basically consistent with the electrode activity trend shown by the polarization curve. The current density corresponding to EE sample at 1800 s can still reach 17.0 mA·cm -2 , which is much higher than the 7.8 mA·cm -2 of NE, indicating that electrochemical etching also has important significance for the electrochemical stability of the coated titanium anode.

[0069] 6. Electrochemical impedance spectroscopy

[0070] Electrochemical impedance spectroscopy can reflect the electron transfer rate of EE, CE and NE electrodes. Figure 7 In the electrochemical impedance spectrogram of the coated titanium anode prepared by different pretreatment methods in 0.5 mol·L -1 H2SO4 solution at 1.35 V, we can further understand the electrocatalytic performance of the titanium anode from the impedance graph. The electrochemical impedance spectrogram of the coated titanium anode after different roughening treatments under this condition is a semicircular capacitive arc shown in the figure. This is mainly due to the OER reaction. The radius of the semicircle as the first approximation corresponds to the charge transfer resistance of OER. The impedance spectrogram of the oxygen evolution reaction is usually fitted with the equivalent circuit R S (R ct Q dl ), in which Rs is the contact resistance of the liquid-solid interface, R ct is the charge transfer resistance, Q dl is the double-layer capacitance of the electrode surface, and R ct Q dl is the impedance of the coating and solution interface. The equivalent circuit diagram and the data fitting graph of the electrochemically etched titanium anode are shown in b of Figure 7 , it can be seen that the experimental data of the capacitive arc of the electrochemically etched titanium anode can be very consistent with the fitting data using this equivalent circuit.

[0071] Table 2 is the fitting results of the electrochemical impedance spectrogram of the titanium anode prepared by different pretreatment methods. The Q dl data is related to the number of active sites on the coating surface. The Q dl of EE electrode is the highest, indicating that the coating contains more surface active sites and has better catalytic activity.

[0072] Table 2 Fitting results of electrochemical impedance spectrogram of titanium substrate prepared by different pretreatment methods

[0073] Sample [R s / Ω·cm 2 ]]> [R ct / Ω·cm 2 ]]> Q dl / mF·cm 2 ]]> nl EE 1.667 3.732 30.47 0.8348 CE 1.670 6.367 17.36 0.8682 NE 1.537 21.368 7.656 0.8792

[0074] R in Table 2 ct This reflects the resistance value of the oxide coating; the lower the value, the more favorable it is for the anodic reaction. This further illustrates that electrochemical etching of the titanium substrate facilitates the reaction at the coated titanium anodic electrode.

[0075] 7. Enhance electrolytic life testing and failure analysis

[0076] Enhanced electrolysis life graphs can reflect the cell voltage variation trend of EE, CE, and NE coated titanium anodes, facilitating the analysis of electrode failure processes. Figure 8 Titanium anodes prepared from different pretreated titanium sheets with the same coating amount at 1 mol·L -1 A line graph showing the change in cell pressure over electrolysis time in H2SO4, indicating that the cell pressure change is related to the anode potential.

[95] The two roughened electrodes, EE and CE, exhibit enhanced electrolytic life. The cell voltage variation trends of the roughened EE and CE anodes are generally characterized by a period of relative flatness followed by a sharp increase, with the flattened area showing minor fluctuations. The anode obtained through electrochemical roughening shows a slower change in the sharp increase phase compared to the anode obtained through chemical etching, indicating that their failure mechanisms are different. Figure 9 The bar chart shows the lifetime of different electrodes. The EE anode achieved a lifetime of 224 hours, while the CE anode achieved 188 hours. However, the lifetime of the coated titanium anode prepared from untreated titanium sheets was less than 100 hours. This is presumably because the surface of the unroughened titanium sheet is relatively smooth, making it difficult for the coating to adhere to the titanium substrate and causing it to detach more easily during testing. This also indicates that different roughening pretreatments can affect the lifetime of the coated titanium anode, and electrochemical etching can effectively extend the lifetime of the coated titanium anode.

[0077] Figure 10 Figures a, b, and c show the failure diagrams for the EE, CE, and NE electrodes, respectively. Failure diagrams b and c show that the main causes of failure are coating peeling and lifting. Specifically, the NE electrode... Figure 10 As shown in Figure c), the coating severely peeled off over a large area, indicating very poor adhesion between the coating and the unetched titanium substrate surface. This is likely the main reason for the rapid failure of the NE electrode. (Failure diagram of the EE electrode is also shown.) Figure 10 As shown in Figure a), the iridium-tantalum oxide coating has a relatively large remaining amount. The cracking and coating loss at the hilly areas indicate that the electrode coating is prone to dissolution and detachment at thinner sections. Further analysis suggests that the failure of the EE electrode is due to a combination of coating detachment, dissolution, and substrate corrosion. The microstructure of the failed CE electrode is as follows: Figure 10As shown in the middle b, the surface morphology with many micro concave pits is obtained by chemical etching, which will be beneficial to enhance the bonding of the coating and the substrate, so the coating is not peeled off in bulk, but is uniformly missing and dissolved. The failure of the CE electrode coating is speculated to be due to the sharp peaks formed between the substrate pits and the pits, which causes the coating to be thin at the peaks, and the electrolyte is more likely to invade the titanium substrate, so that the titanium substrate is oxidized and failed. Combined with the strengthening life experiment and the SEM graph of the coating, it can be known that the surface with high roughness size pits combined by electrochemical etching is most beneficial to fully exert the catalytic activity of the coating while having higher service life.

[0078] In summary, the titanium sheet is roughened by electrochemical etching and chemical etching in the present application, and the performance and strengthening electrolytic life of the two roughened substrates and the titanium substrate without any roughening treatment under the same active layer coating are compared. Preliminary research finds that roughening has a great influence on the catalytic activity and stability of the coated titanium anode, and the following conclusions are drawn: In the electrochemical test of EE, CE and NE electrodes, it is found that whether the titanium substrate is roughened or not has a great influence not only on the OER performance, but also on the stability of the coated electrode. The titanium anode prepared by the substrate without roughening has lower catalytic activity and poorer life. The titanium substrate obtained by electrochemical etching can have higher electrocatalytic activity and electrochemical active area under the same active oxide load. Through the strengthening electrolytic life experiment and the electrode failure graph, it can be speculated that proper etching directly affects the service life of the electrode. The CE electrode has relatively sharp protruding peaks due to the micro-morphology of the titanium substrate, which causes the protruding titanium to be more likely to protrude the coating, and the electrolyte is more likely to invade the titanium substrate, causing the substrate to corrode and oxidize. The EE electrode has larger hilly undulations and higher roughness on the surface, which can maintain longer strengthening electrolytic life. It is shown that electrochemical etching is more beneficial to the adhesion of the coating and the stability of the electrode.

[0079] It should be understood that the application of the present application is not limited to the above examples, and those of ordinary skill in the art can make improvements or changes according to the above description, and all these improvements and changes shall belong to the protection scope of the appended claims of the present application.

Claims

1. A method for roughening the surface of a coated titanium electrode substrate, characterized in that, The method comprises the steps of: Na3PO4·12H2O, Na2CO3, NaOH are dissolved in deionized water in a mass ratio of 105:25:4 to prepare 0.3% alkali oil removal liquid, and heated to boiling for standby; The initial titanium sheet is cut and added to the boiling alkali oil removal liquid and kept for 40-80 min; The initial titanium sheet is taken out, washed with deionized water and ultrasonically cleaned in deionized water to complete the alkali washing process, and the cut titanium sheet is prepared; A double electrode system is formed by taking NaBr as an electrolyte, taking the cut titanium sheet as a working electrode, and taking an initial titanium sheet as a counter electrode, and the double electrode system is powered on. -2 The cut titanium sheet is etched once, and then the cut titanium sheet is cleaned by an ultrasonic cleaning machine to remove flocculent impurities on the surface of the cut titanium sheet, and then the cut titanium sheet is cleaned by an acid etching liquid for 1-2 min. -2 The cut titanium sheet is etched twice, and then the cut titanium sheet is cleaned by an ultrasonic cleaning machine to remove flocculent impurities on the surface of the cut titanium sheet, and then the cut titanium sheet is cleaned by an acid etching liquid for 1-2 min. Then, the titanium sheet is washed with deionized water for 3-4 times, and finally washed with ethanol once, the cleaned rough titanium substrate is stored in anhydrous ethanol and standby, and the rough titanium substrate is prepared.

2. The method for roughening the surface of a coated titanium electrode substrate according to claim 1, characterized in that, The size of the cut titanium sheet is 10 mm×15 mm×0.2 mm or 10 mm×20 mm×0.2 mm.

3. A coated titanium electrode substrate, characterized in that, The coated titanium electrode substrate surface roughening method is prepared by using the coated titanium electrode substrate surface roughening method of claim 1 or 2.

4. Use of a coated titanium electrode substrate, characterized in that The coated titanium electrode substrate of claim 3 is used to prepare a coated titanium electrode.

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