Active carbon electrode doped with photo-modified metal oxide in hydroxyl atmosphere and preparation method of active carbon electrode

Abstract

The invention relates to the field of electrochemical materials for preparing carbon electrodes, in particular to a light-modified trace metal oxide doped activated carbon electrode in a hydroxyl atmosphere and a preparation method of the light-modified trace metal oxide doped activated carbon electrode. According to the preparation method, a trace amount of nano-scale metal oxide is added in the active carbon electrode manufacturing stage, then a tabletting electrode is prepared, after the electrode is formed, more oxygen-containing functional groups are obtained on the surface of the electrode plate by adopting an illumination method in a hydroxyl atmosphere, and meanwhile, the wettability of the electrode plate is also effectively improved. The improvement of the wettability greatly improves the effective specific surface area of the active carbon of the electrode plate, and the improvement of the specific surface area of the electrode plate and richer oxygen-containing functional groups enable the electrode to obtain higher capacitive performance under the condition of aqueous electrolyte. The operation method is simple and easy to implement, has the advantages of low energy consumption, safety and environmental protection, does not generate physical contact with the electrode plate in the modification process, and does not need additional protection measures.

Description

[0001] Technical Field: The present invention relates to the field of electrochemical materials for the preparation of carbon electrodes, and specifically relates to an activated carbon electrode modified by light doping with trace metal oxides in a hydroxyl atmosphere and a preparation method thereof.

[0002] Technical Background: Activated carbon is used as an electrode material in electrochemical energy storage devices such as supercapacitors due to its high stability and rate performance. The activated carbon electrode provides a double-layer capacitance in the supercapacitor. For the double-layer capacitance, the surface area utilization rate of the activated carbon material is very important. However, the hydrophobicity exhibited by the activated carbon limits the surface area utilization rate. Therefore, the wetting characteristics of the electrode material are the key factors determining its energy storage performance. Improving the wetting characteristics of the material can increase the oxygen-containing functional groups and available surface area of the active material, thereby enhancing the energy storage effect. For metal oxides, surface functionalization modification of their nanomaterials by physical and chemical means can regulate the surface free energy of the material and control the surface charge, achieving the purposes of changing the wettability of the material surface and improving the surface activity. The oxygen-containing functional groups on the surface of activated carbon also have a great influence on wettability, making ions more likely to enter the micropores during the electrochemical process, effectively increasing the specific surface area of the material, and thus obtaining a better specific surface area. The current main research on activated carbon electrodes mainly focuses on material preparation, such as obtaining a higher specific surface area, more oxygen-containing functional groups, and doping S and N elements. There is less research on further modifying the electrode after it is prepared and formed to improve its capacitance capacity.

[0003] The authorized invention patent ZL201710658575.6 uses a method of applying phosphoric acid to the activated carbon electrode to improve the wetting performance of the electrode, realizing in-situ modification of the carbon electrode by a one-step method to obtain an increase in capacitance. The coating method of this invention patent will generate a certain amount of phosphorus-containing cleaning wastewater that needs to be further treated.

[0004] The authorized invention patent ZL202010701076.2 uses a method of microbial degradation to carry out electrode modification work. A biodegradable substance is added during the production process of the carbon electrode. Through the action of microorganisms, the specific surface area of the carbon electrode is increased and the pore structure of the carbon electrode is enriched. A large number of functional groups are generated inside and on the surface of the carbon electrode, and metal elements are doped at the same time, which plays a beneficial role in the adsorption of charges and the pseudocapacitive reaction. Microbial waste liquid will be generated during the biological process. Although it is treated by microwave, its production and treatment process is also relatively complex.

[0005] The authorized invention patent ZL202110521101.3 has carried out work on plant fiber-doped and polymer-modified activated carbon electrodes. Nanoscale plant fibers are added during the electrode manufacturing stage, and after the electrode is formed, the plant fibers are synthesized into water-absorbing polymers through a polymerization reaction. After the polymer absorbs water in the aqueous electrolyte, it swells and re-opens the collapsed pore space in the original activated carbon. The nanoscale water-absorbing substances inside the electrode can effectively improve the internal wetting performance of the electrode and enhance the capacitance capacity of the electrode. This process is slightly complicated due to the need for a polymerization reaction in the later stage, and the reaction process also poses requirements for the electrode strength.

[0006] The authorized invention patent ZL202010701035.3 has carried out research on liquid-phase pressure-modified carbon electrodes. The wettability of the capacitive electrode has been significantly improved, but the high operating pressure and the electrode cleaning solution are also limitations of this invention.

[0007] In the present invention, trace amounts of nanoscale metal oxides are added during the activated carbon electrode manufacturing stage, and then a pressed electrode is prepared. After the electrode is formed, in a hydroxyl atmosphere (such as water, methanol, ethanol, etc.), by using a method of light irradiation (infrared, sunlight, ultraviolet light), the surface of the electrode sheet obtains more oxygen-containing functional groups, and at the same time, the wetting performance of the electrode sheet is effectively improved. The improvement of the wetting performance has significantly increased the effective specific surface area of the activated carbon in the electrode sheet. The increase in the specific surface area of the electrode sheet and the richer oxygen-containing functional groups enable the electrode to obtain higher capacitance performance under aqueous electrolyte conditions. This operation method is simple and easy to implement, has the advantages of low energy consumption, safety, and environmental protection, and moreover, the modification process does not cause physical contact with the electrode sheet, and no external protection measures are required. Summary of the Invention

[0008] The object of the present invention is to provide a light-modified activated carbon electrode doped with metal oxides in a hydroxyl atmosphere and its specific preparation method. Compared with the un-doped and un-modified carbon electrode, the prepared carbon electrode has improved wettability, significantly enhanced capacitance capacity, and basically unchanged capacitance retention rate, and has the characteristics of easily available raw materials and simple methods.

[0009] To achieve the above object, the technical solution steps taken by the present invention are as follows:

[0010] 1) Sieve and dry the activated carbon for later use;

[0011] 2) Prepare a mixture of nano metal oxide / activated carbon by using the direct mixing method or the solvent thermal-calcination combined method, and the obtained mixture of metal oxide / activated carbon is mixture A;

[0012] 3) Weigh a certain amount of mixture A, conductive agent, and binder according to weight fractions, uniformly mix them, and then add a certain amount of anhydrous ethanol or N-methylpyrrolidone as a solvent, and stir while heating until the solvent completely evaporates to obtain mixture B;

[0013] 4) Drop a small amount of ethanol or methanol onto mixture B to obtain mixture C;

[0014] 5) Take a current collector plate, and evenly distribute mixture C onto the current collector plate by the coating method or the pressing method, and vacuum dry it at 40 - 80 °C for 3 - 15 hours. After cooling down, take it out to obtain electrode A;

[0015] 6) Put electrode A into a closed modification device, and place a light source with adjustable power in the modification device;

[0016] 7) Introduce a modified hydroxyl atmosphere into the modification device. Under the condition of 10 - 55 °C, control the partial pressure of hydroxyl gas in the atmosphere to be 0 - 20 kPa or the relative humidity of air to be 0 - 100%;

[0017] 8) Turn on the light source, adjust it to a certain power, adjust the temperature of the modification device, and at the same time keep the partial pressure of hydroxyl gas at 0 - 20 kPa or the relative humidity at 0 - 100%, irradiate for 10 - 300 minutes, and then take it out from the modification device to obtain modified electrode B.

[0018] Use a contact angle measuring instrument to test the wetting performance of the modification. If the contact angle decreases significantly, this modified electrode B is the finished modified electrode. It should be noted that this modified electrode should be put into use immediately or stored under bright and illuminated conditions. After 30 hours under dark, low - light or extremely dry storage conditions, the modification effect weakens until it returns to the unmodified effect.

[0019] Further, the metal oxide described in step 2) can be TiO 2 、Mn y O x 、NiO、Fe 2 O 3 、WO 3 、ZnO、Cu 2 O、SnO 2 any one of them.

[0020] Further, the steps of the direct mixing method described in step 2) are as follows: Take nano - metal oxide, grind it in a nano - grinder for 5 - 60 minutes to obtain the metal oxide for standby; Weigh the nano - metal oxide and activated carbon with a mass ratio of 1:1000 - 10:1000, mix them and put them into the nano - grinder to grind for at least 150 minutes to ensure uniform mixing and obtain the mixture.

[0021] Further, the steps of the solvothermal-calcination combined method in step 2) are as follows: Add metal chloride to a certain amount of activated carbon, and ensure that the mass ratio of the converted oxide to activated carbon is 1:1000 - 10:1000; Add one or more of urea solution, thiourea solution, ethylene glycol, ammonia water, and sodium citrate reagent, where for every 1 g of pure chloride, it corresponds to 1 - 10 mL of urea or thiourea solution with a concentration of 1 mol / L, or corresponds to 1 - 10 g of ethylene glycol, ammonia water, or sodium citrate; Then add deionized water according to the ratio of 200 mL of deionized water for every 10 g of activated carbon, and transfer it to a hydrothermal reaction kettle (with a Teflon inner lining); Add all reactants and solvents to the hydrothermal reaction kettle, and react at 80 - 220 °C for 4 - 24 hours; After the reaction is cooled, filter by suction. During the suction filtration process, wash several times with deionized water and alcohol respectively, dry the obtained solid, the drying temperature is below 50 °C, and the drying time is 1 - 8 hours; Then put the solid into a tube furnace, and calcine it at 300 - 1000 °C for 2 - 10 hours under an inert atmosphere, and take it out after cooling to obtain a mixture of metal oxide and activated carbon.

[0022] Further, the conductive agent described in step 3) is any one or a combination of acetylene black, graphite powder, carbon nanotubes, or graphene; the binder is polytetrafluoroethylene or polyvinylidene fluoride; By weight, the mixture A is 70 - 90 parts, the conductive agent is 5 - 15 parts, and the binder is 5 - 15 parts; The mass of the solvent is 1 - 10 times the total mass of the above several substances after mixing.

[0023] Further, in step 5), the current collector plate is a metal current collector plate, an alloy current collector plate, or a carbon current collector plate.

[0024] Further, in step 5), the pressing method is as follows: Press the mixture C onto the current collector plate with a tablet press at 5 - 40 MPa, vacuum dry it at 30 - 100 °C for 2 - 24 hours, and take it out after cooling and temperature reduction to obtain electrode A.

[0025] Further, in step 6), the modification equipment is an incubator or a vacuum glove box with constant temperature and humidity functions.

[0026] Further, in step 6), the light source is a light source with adjustable power and controllable wavelength, which can stably provide infrared, visible, and ultraviolet light of a certain wavelength.

[0027] Further, in step 7), the modified hydroxyl atmosphere is one or a mixture of volatile organic alcohols and organic acid gases such as wet air, methanol gas, and ethanol gas.

[0028] Further, in step 8), the power is 100 - 2000 W, and the temperature of the modification device is 10 - 55 °C.

[0029] In the actual operation process, when using wet air, the modification operation is carried out in an incubator, and the water vapor partial pressure is controlled by relative humidity or absolute humidity at a certain temperature. When using gases such as methanol gas and ethanol gas, which are not wet air, as the hydroxyl atmosphere, the modification operation needs to be carried out in a vacuum glove box. At room temperature, the gas pressure is controlled by controlling the vacuum degree. It should be particularly noted that organic gases such as methanol and ethanol are toxic and flammable and explosive gases. During the modification process, it is necessary to pay attention to the explosion-proof measures of the modification light source, and the modification gas should also be avoided from contacting the operators.

[0030] The beneficial effects of the present invention are as follows: The wetting performance of the activated carbon electrode is poor, especially under the condition of aqueous electrolyte, resulting in the electrode material not being fully utilized. In the present invention, a metal oxide with a mass ratio of less than 1% is doped into the activated carbon and then the electrode is prepared. Then, the activated carbon electrode is modified by light irradiation in a hydroxyl atmosphere. The wetting performance of the metal oxide can be used to improve the wetting performance of the overall electrode sheet, and at the same time, the oxygen-containing functional groups on the surface of the activated carbon material are increased. Under the action of both, the wetting performance of the overall electrode material is improved, thereby improving the utilization rate of the pore area of the material. In particular, the capacitance performance of the electric double layer supercapacitor can be significantly improved. According to the method for modifying the carbon electrode provided by the present invention, under the condition of aqueous electrolyte, the specific capacitance of the modified carbon electrode is 30% - 100% higher than that of the carbon electrode directly prepared from ordinary activated carbon under the same conditions, and the capacitance retention rate can still reach more than 96% after 3000 charge and discharge cycles. Moreover, this modification method is easy to operate, there is no physical contact during the modification process, and the modification effect is good, providing a new idea for the application and research and development of carbon electrode materials in the fields of supercapacitors and batteries. Description of the Drawings

[0031] In the drawings, the left figure is the contact angle measurement image of the activated carbon electrode doped with titanium dioxide without modification; the right figure is the contact angle image of the activated carbon electrode doped with titanium dioxide irradiated with 302 nm light for 30 minutes in an air atmosphere (1 atm, 30 °C, relative humidity 60%). Detailed Embodiments

[0032] Example 1

[0033] (1) Grind the dry activated carbon, pass through a 300-mesh sieve, and dry for later use; take nano-titanium dioxide for later use.

[0034] (2) Weigh 29.7 g of activated carbon into a 500 ml beaker. Then weigh 0.3 g of nano-titanium dioxide and add it to the beaker. Stir evenly with a glass rod, pour it into a grinder and grind manually for 5 min. Then put the mixed powder into a planetary ball mill and grind and mix at 200 r / min for 6 h. Finally, activated carbon material powder with 1% mass composition of nano-titanium dioxide is obtained;

[0035] (3) By mass ratio, take 8.5 g of activated carbon, 1 g of acetylene black (conductive agent), and 0.5 g of polytetrafluoroethylene (PTFE) and mix them. Then add about 30 g of N-methylpyrrolidone solution. Stir and heat while slowly evaporating the solvent to make the mixture mix evenly until the mixture becomes viscous, obtaining mixture A;

[0036] (4) Drop a small amount of weighed anhydrous ethanol (about 5% of the mass of mixture A) onto mixture A to obtain mixture B;

[0037] (5) Scrape mixture B onto the current collector with a surgical blade, dry it in vacuum at 50 °C for 12 hours, take it out after cooling down, and obtain electrode A;

[0038] (6) Put electrode A into an incubator, control the temperature at 30 °C, adjust the relative air humidity to 60%, turn on the light source, adjust the wavelength to 302 nm, adjust the light source power to 300 W, and irradiate for 30 min. Modified electrode B is obtained.

[0039] In Example 1, the performance of the modified electrode is as follows: the contact angle of the modified electrode is 33°; in a three-electrode system, with 1 M sodium sulfate solution as the electrolyte, in the potential range of 0 - 0.8 V, under the condition that the scanning rate of cyclic voltammetry is set at 0.005 V / s, the specific capacitance performance is 246 F / g; at a constant current charge-discharge with a current density of 1 A / g, the capacitance retention rate after 3000 charge-discharges is 97%.

[0040] Example 2

[0041] (1) Grind the dry activated carbon, sieve it through a 300-mesh sieve, and dry it for standby; take titanium tetrachloride for standby.

[0042] (2) Weigh a certain amount of liquid TiCl 4 0.237 g and 10 g of activated carbon, 3 mL of ethylene glycol solution with a concentration of 1 mol / L, and 200 mL of deionized water. Put the above materials into a hydrothermal reaction kettle (with a Teflon inner liner) with a volume of 250 mL. React at 150 °C for 8 hours. Cool the reaction solution to room temperature, take out the reaction kettle and filter it, filter it three times with distilled water, wash it once with anhydrous ethanol, and dry it in an oven at 50 °C for 1 h. Finally, set the tube furnace to 600 °C and calcine it in an inert atmosphere for 4 h. After cooling, the final sample TiO 2Activated carbon powder with a mass content of approximately 1%.

[0043] (3) By mass ratio, respectively take 8.5 g of the activated carbon powder obtained in the above step (2), 1 g of acetylene black (conductive agent), and 0.5 g of polytetrafluoroethylene (PTFE), mix them, then add approximately 30 g of N-methylpyrrolidone solution, heat and stir to slowly evaporate the solvent and make the mixture mix evenly until the mixture becomes viscous, obtaining mixture A;

[0044] (4) Drop a small amount of anhydrous ethanol (about 5% of the mass of mixture A) weighed on mixture A to obtain mixture B;

[0045] (5) Scrape mixture B onto the current collector with a surgical blade, dry it in a vacuum at 50 °C for 12 hours, take it out after cooling down, obtaining electrode A;

[0046] (6) Put electrode A into an incubator, control the temperature at 30 °C, adjust the relative air humidity to 60%, turn on the light source, adjust the wavelength to 302 nm, adjust the light source power to 300 W, and irradiate for 30 min. Obtain modified electrode B.

[0047] In Example 2, the performance of the modified electrode is as follows: the contact angle of the modified electrode is 15°; in a three-electrode system, with 1 M sodium sulfate solution as the electrolyte, in the potential range of 0.8 V, under the condition that the scanning rate of cyclic voltammetry is set to 0.005 V / s, the specific capacitance performance is 257 F / g; at a constant current charge-discharge with a current density of 1 A / g, the capacitance retention rate after 3000 charge-discharges is 97%.

[0048] Example 3

[0049] (1) Grind the dried activated carbon, pass it through a 300-mesh sieve, and dry it for standby; take nickel chloride hexahydrate for standby.

[0050] (2) Weigh 0.185 g of nickel chloride hexahydrate and 10 g of activated carbon, 2 mL of urea solution with a concentration of 1 mol / L, and 200 mL of deionized water. Put the above materials into a hydrothermal reaction kettle (with a Teflon liner) with a volume of 250 mL. React at 160 °C for 6 hours, cool the reaction solution to room temperature, take out the reaction kettle and filter, filter three times with distilled water, wash once with anhydrous ethanol, and dry in an oven at 50 °C for 1 h. Finally, set the tubular furnace to 600 °C and calcine in an inert atmosphere for 3 h. After cooling, the final sample obtained is activated carbon powder with a NiO mass content of approximately 0.5%.

[0051] (3) Weigh 8 g of the activated carbon powder obtained in the above step (2), 1 g of acetylene black (conductive agent), and 1 g of polyvinylidene fluoride (PVDF) respectively by mass ratio, mix them, then add about 30 g of N-methylpyrrolidone solution, heat and stir to slowly evaporate the solvent and make the mixture mix evenly until the mixture becomes viscous, obtaining mixture A;

[0052] (4) Drop a small amount of anhydrous ethanol (about 5% of the mass of mixture A) weighed in advance onto mixture A to obtain mixture B;

[0053] (5) Scrape mixture B onto the current collector with a surgical blade, dry it in a vacuum at 50 °C for 12 hours, take it out after cooling down, obtaining electrode A;

[0054] (6) Put electrode A into a vacuum glove box, control the temperature at 25 °C, evacuate the air in the glove box, after the pressure in the glove box is stable, turn off the exhaust equipment, spray methanol vapor into the glove box to increase the pressure in the glove box by about 15 kPa, stop inputting methanol vapor, turn on the light source, adjust the wavelength to 245 nm, adjust the light source power to 300 W, and irradiate for 48 min. Obtain modified electrode B.

[0055] In Example 3, the performance of the modified electrode is as follows: the contact angle of the modified electrode is about 0°; in a three-electrode system, with 1 M sodium sulfate solution as the electrolyte, in the potential range of 0 - 0.8 V, under the condition that the scanning rate of cyclic voltammetry is set at 0.005 V / s, the specific capacitance performance is 264 F / g; at a constant current charge-discharge with a current density of 1 A / g, the capacitance retention rate after 3000 charge-discharges is 96.5%.

[0056] Example 4

[0057] (1) Grind the dried activated carbon, sieve it through a 300-mesh sieve, and dry it for standby; weigh manganese chloride tetrahydrate for standby.

[0058] (2) Weigh 0.115 g of manganese chloride tetrahydrate, 10 g of activated carbon, 2 mL of a 1 mol / L thiourea solution, and 200 mL of deionized water, and put the above materials into a hydrothermal reaction kettle (with a Teflon liner) with a volume of 250 mL. React at 150 °C for 8 hours, cool the reacted solution to room temperature, take out the reaction kettle and filter it, filter it three times with distilled water, wash it once with anhydrous ethanol, and dry it in an oven at 50 °C for 1 h. Finally, set the tubular furnace to 400 °C and calcine it in an inert atmosphere for 3 h. After cooling, the final sample obtained is MnO 2 Activated carbon powder with a mass content of about 0.5%.

[0059] (3) Weigh 8 g of the activated carbon powder obtained in the above step (2), 1 g of acetylene black (conductive agent), and 1 g of polyvinylidene fluoride (PVDF) respectively by mass ratio, mix them, and then add about 30 g of N-methylpyrrolidone solution. Stir and heat to slowly evaporate the solvent and make the mixture mix evenly until the mixture becomes viscous, obtaining mixture A;

[0060] (4) Drop a small amount of anhydrous ethanol (about 5% of the mass of mixture A) weighed in mixture A to obtain mixture B;

[0061] (5) Coat mixture B on the current collector with a surgical blade, dry it in vacuum at 50 °C for 12 hours, take it out after cooling down, and obtain electrode A;

[0062] (6) Put electrode A into a vacuum glove box, control the temperature at 30 °C, evacuate the air in the glove box. After the pressure in the glove box is stable, turn off the exhaust equipment, spray ethanol vapor into the glove box to increase the pressure in the glove box by about 17 kPa, stop inputting ethanol vapor, turn on the light source, adjust the wavelength to 302 nm, adjust the light source power to 300 W, and irradiate for 80 min. Obtain modified electrode B.

[0063] In Example 4, the performance of the modified electrode is as follows: the contact angle of the modified electrode is about 0°; in a three-electrode system, with 1 M sodium sulfate solution as the electrolyte, in the potential range of 0 - 0.8 V, under the condition that the scanning rate of cyclic voltammetry is set to 0.005 V / s, the specific capacitance performance is 268 F / g; at a constant current charge-discharge with a current density of 1 A / g, the capacitance retention rate after 3000 charge-discharges is 97%.

[0064] Example 5

[0065] (1) Grind the dried activated carbon, sieve it through a 300-mesh sieve, and dry it for standby; weigh ferric chloride hexahydrate for standby.

[0066] (2) Weigh 0.17 g of ferric chloride hexahydrate, 10 g of activated carbon, 2 mL of ethylene glycol solution with a certain concentration, 1 mL of urea solution with a concentration of 1 mol / L, 0.05 g of sodium citrate dihydrate, and 200 mL of deionized water. Put the above materials into a hydrothermal reaction kettle (with a Teflon inner lining) with a volume of 250 mL. React at 190 °C for 24 hours, cool the reacted solution to room temperature, take out the reaction kettle and filter it, filter it three times with distilled water, wash it once with anhydrous ethanol, and dry it in an oven at 50 °C for 1 h. Finally, set the tube furnace to 300 °C and calcine it in an inert atmosphere for 2 h. After cooling, the final sample obtained is Fe 2 O 3 activated carbon powder with a mass content of about 0.5%.

[0067] (3) Take 8 g of the activated carbon powder obtained in the above (2), 1 g of acetylene black (conductive agent), and 1 g of polyvinylidene fluoride (PVDF) respectively by mass ratio, mix them, and then add about 30 g of N-methylpyrrolidone solution. While stirring, heat to slowly evaporate the solvent and mix the mixture evenly until the mixture becomes viscous to obtain mixture A;

[0068] (4) Drop a small amount of anhydrous ethanol (about 5% of the mass of mixture A) weighed onto mixture A to obtain mixture B;

[0069] (5) Spread mixture B on the current collector with a surgical blade, dry it in vacuum at 50 °C for 12 hours, take it out after cooling down to obtain electrode A;

[0070] (6) Put electrode A into an incubator, control the temperature at 30 °C, adjust the relative air humidity to 50%, turn on the light source, adjust the wavelength to 302 nm, adjust the light source power to 300 W, and irradiate for 50 min to obtain modified electrode B.

[0071] In Example 5, the performance of the modified electrode is as follows: the contact angle of the modified electrode is about 0°; in a three-electrode system, with 1 M sodium sulfate solution as the electrolyte, in the potential range of 0 - 0.8 V, under the condition that the scanning rate of cyclic voltammetry is set at 0.005 V / s, the specific capacitance performance is 263 F / g; at a constant current charge-discharge with a current density of 1 A / g, the capacitance retention rate after 3000 charge-discharges is 97.5%

[0072] Comparative Example 1 Activated Carbon

[0073] Grind the dried activated carbon, pass it through a 300-mesh sieve, and dry it for standby. Mix the above activated carbon with acetylene black and polytetrafluoroethylene (PTFE) in a mass ratio of 85:10:5, and then add a nitrogen-methylpyrrolidone solution with a mass three times that of the mixture as the solvent. While heating and stirring until a large amount of the solvent evaporates, a viscous mixture A is obtained; drop a small amount of anhydrous ethanol onto mixture A, and scrape it onto a nickel mesh by the coating method to prepare an electrode. Dry it in vacuum at 60 °C for 12 hours, take it out after cooling down to obtain electrode A. Dry it in vacuum at 60 °C for 12 hours, take it out after cooling down to obtain carbon electrode B.

[0074] In Comparative Example 1, the performance of the electrode is as follows: the contact angle of the electrode is 110°; in a three-electrode system, with 1 M sodium sulfate solution as the electrolyte, in the potential range of 0.8 V, under the condition that the scanning rate of cyclic voltammetry is set at 0.005 V / s, the specific capacitance performance is 167 F / g; at a constant current charge-discharge with a current density of 1 A / g, the capacitance retention rate after 3000 charge-discharges is 99.5%.

[0075] Comparative Example 2 Activated Carbon Modification

[0076] The dry activated carbon was ground, passed through a 300-mesh sieve, and dried for later use. The above-mentioned activated carbon was mixed with acetylene black and polytetrafluoroethylene (PTFE) in a mass ratio of 85:10:5. Then, a solution of N-methylpyrrolidone with three times the mass of the mixture was added as a solvent. While heating and stirring, the solvent was allowed to volatilize significantly to obtain a viscous mixture A. A small amount of absolute ethanol was dropped onto mixture A, and it was scraped onto a nickel mesh by the smearing method to prepare an electrode, which was dried in vacuum at 60 °C for 12 hours. After cooling and temperature reduction, it was taken out to obtain electrode A. It was dried in vacuum at 60 °C for 12 hours. After cooling and temperature reduction, it was taken out to obtain carbon electrode B.

[0077] Electrode B was placed in an incubator, the temperature was controlled at 30 °C, the relative air humidity was adjusted to 60%, the light source was turned on, the wavelength was adjusted to 302 nm, the light source power was adjusted to 300 W, and it was irradiated for 30 min to obtain modified electrode C;

[0078] In Comparative Example 2, the performance of the modified electrode was as follows: the contact angle of the modified electrode was 113°; in a three-electrode system, with 1 M sodium sulfate solution as the electrolyte, in the potential range of 0.8 V, under the condition that the scanning rate of cyclic voltammetry was set at 0.005 V / s, the specific capacitance performance was 165 F / g; at a constant current density of 1 A / g for charge and discharge, the capacitance retention rate after 3000 charge and discharge cycles was 99.5%.

[0079] Comparative Example 3: Doping without modification

[0080] (1) The dry activated carbon was ground, passed through a 300-mesh sieve, and dried for later use; nano-titanium dioxide was taken for later use.

[0081] (2) 30 g of activated carbon was weighed into a 500-ml beaker, and then 0.3 g of nano-titanium dioxide was weighed and added to the beaker. It was slowly stirred evenly with a glass rod, poured into a grinder and manually ground for 5 min. Then, the mixed powder was put into a planetary ball mill and ground and mixed at 200 r / min for 6 h. Finally, activated carbon material powder with a nano-titanium dioxide mass composition of 1% was obtained;

[0082] (3) By mass ratio, 8.5 g of activated carbon, 1 g of acetylene black (conductive agent), and 0.5 g of polytetrafluoroethylene (PTFE) were taken and mixed respectively. Then, about 30 g of N-methylpyrrolidone solution was added. While stirring and heating, the solvent was slowly volatilized and the mixture was evenly mixed until the mixture became viscous to obtain mixture A;

[0083] (4) A small amount of weighed absolute ethanol (about 5% of the mass of mixture A) was dropped onto mixture A to obtain mixture B;

[0084] (5) Mixture B was scraped onto the current collector with a surgical blade and dried in vacuum at 50 °C for 12 hours. After cooling and temperature reduction, it was taken out to obtain electrode A;

[0085] In this Comparative Example 3, the electrode performance is as follows: the electrode contact angle is 105°; in a three-electrode system, 1M sodium sulfate solution is used as the electrolyte, the potential range is 0.8V, and under the condition that the scanning rate of cyclic voltammetry is set to 0.005V / s, the specific capacitance performance is 166F / g; the current density is 1A / g for constant current charge and discharge, and the capacitance retention rate after 3000 charge and discharge cycles is 99%.

Claims

1. A method for preparing a photomodified metal oxide-doped activated carbon electrode under a hydroxyl atmosphere, characterized in that The preparation steps are as follows: (1) sieving and drying the activated carbon for later use; (2) preparing a mixture of nano metal oxide / activated carbon by a direct mixing method or a solvent thermal-calcination combined method, and the obtained mixture of metal oxide / activated carbon is mixture A; (3) Weighing a certain amount of mixture A, a conductive agent, and a binder according to weight fractions, uniformly mixing, adding a certain amount of anhydrous ethanol or nitrogen methyl pyrrolidone as a solvent, and heating and stirring until the solvent is completely evaporated to obtain a mixture B; (4) adding a small amount of ethanol or methanol to mixture B to obtain mixture C; (5) Take the current collecting plate, and evenly distribute the mixture C on the current collecting plate by a spreading method or a pressing method, and vacuum dry it at 40-80° C. for 3-15 hours, and take it out after cooling to obtain electrode A; (6) placing electrode A into a sealed modification device, and placing a light source with adjustable power in the modification device; (7) introducing a modified hydroxyl atmosphere into the modification equipment, and controlling the hydroxyl gas partial pressure in the atmosphere to 0-20 kPa or the relative humidity of the air to 0-100% at 10-55° C.; (8) Turn on the light source, adjust it to a certain power, adjust the temperature of the modification equipment, and keep the partial pressure of the hydroxyl gas at 0-20 kPa or the relative humidity at 0-100%, irradiate for 10-300 minutes, and then take it out from the modification equipment to obtain the modified electrode B.

2. The method for preparing a photomodified metal oxide-doped activated carbon electrode under a hydroxyl atmosphere as claimed in claim 1, characterized in that: The metal oxide described in step (2) is TiO2, Mn y O x , any one of NiO, Fe2O3, WO3, ZnO, Cu2O, SnO2.

3. The method for preparing a photomodified metal oxide-doped activated carbon electrode under a hydroxyl atmosphere as claimed in claim 1, characterized in that The direct mixing method described in step (2) is as follows: taking nano metal oxide, grinding it in a nano grinder for a period of time to obtain metal oxide for use; weighing the nano metal oxide and activated carbon in a mass ratio of 1:1000 to 10:1000, mixing them, and grinding them in a nano grinder for at least 150 minutes to ensure uniform mixing to obtain a mixture.

4. The method for preparing a photomodified metal oxide-doped activated carbon electrode under a hydroxyl atmosphere as claimed in claim 1, characterized in that The solvent thermal-calcination combined method described in step (2) comprises the following steps: adding a metal chloride to a certain amount of activated carbon, and ensuring that the mass ratio of the metal chloride to the activated carbon after conversion into oxides is 1:1000-10:1000; adding one or more of urea solution, thiourea solution, ethylene glycol, ammonia water, and sodium citrate reagents, wherein each 1g of pure chloride corresponds to 1-10mL of 1mol / L urea or thiourea solution, or corresponds to 1-10g of ethylene glycol, ammonia water, or sodium citrate; and then adding 200mL of deionized water per 10g of activated carbon. Deionized water is added in a proportion of 1:1 to 2:1 and the reaction mixture is transferred to a hydrothermal reactor; all reactants and solvents are added to the hydrothermal reactor, and the reaction is carried out at 80-220° C. for 4-24 hours; the reaction is filtered after cooling, and the filtration process is washed with deionized water and alcohol for several times, and the obtained solid is dried at a drying temperature below 50° C. for 1-8 hours; the solid is then placed in a tubular furnace, calcined at 300-1000° C. under an inert atmosphere for 2-10 hours, and taken out after cooling to obtain a mixture of metal oxides and activated carbon.

5. The method for preparing a photomodified metal oxide-doped activated carbon electrode under a hydroxyl atmosphere as claimed in claim 1, characterized in that: In step (3), the mixture A is 70-90 parts, the conductive agent is 5-15 parts, and the binder is 5-15 parts in terms of weight; the mass of the solvent is 1-10 times the total mass of the above-mentioned substances after mixing.

6. The method for preparing a photomodified metal oxide-doped activated carbon electrode under a hydroxyl atmosphere as claimed in claim 5, characterized in that: The conductive agent described in step (3) is any one or a combination of acetylene black, graphite powder, carbon nanotubes or graphene; the binder is polytetrafluoroethylene or polyvinylidene fluoride.

7. The method for preparing a photomodified metal oxide-doped activated carbon electrode under a hydroxyl atmosphere as claimed in claim 1, characterized in that In step (5), the pressing method is: pressing the mixture C onto a current collecting plate at 5-40 MPa using a tablet press, vacuum drying at 30-100° C. for 2-24 hours, and taking it out after cooling to obtain electrode A.

8. The method for preparing a photomodified metal oxide-doped activated carbon electrode under a hydroxyl atmosphere as claimed in claim 1, characterized in that: In step (7), the modified hydroxyl atmosphere is one or a mixture of volatile organic alcohols such as humid air, methanol gas, ethanol gas, and organic acid gases.

9. The method for preparing a photomodified metal oxide-doped activated carbon electrode under a hydroxyl atmosphere as claimed in claim 1, characterized in that: In step (8), the power is 100-2000W and the temperature of the modification equipment is 10-55°C.

10. An activated carbon electrode doped with a metal oxide photomodified in a hydroxyl atmosphere, characterized in that: Obtained by the preparation method according to any one of claims 1 to 9.

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