Contact electrocatalyst, method for making thereof and its applications in degrading organic pollutants

Abstract

The present invention discloses a contact electrocatalyst comprising a modified PMMA polymer having a plurality of functional monomers, wherein the side chain of the functional monomer is substituted of an electron-pulling group. High substitution rate of electron-pulling groups enables the plasma-modified polymer to activate generation of reactive oxygen species, thereby improving degradation of organic pollutes. Reuse of the plasma-modified polymer in electrocatalytic degradation demonstrates consistent results after multiple repeats, and the plasma-modified polymer remains highly effective of organic pollute degradation after long-term preservation, indicating excellent endurance.

Description

Technical Field

[0001] This invention relates to catalysts, particularly catalysts that catalyze the chain reaction of reactive oxygen species through contact electrification; the invention also relates to the manufacture of the aforementioned catalysts and methods for using the aforementioned catalysts to degrade organic pollutants. Prior Technology

[0002] Current methods for degrading organic pollutants (such as methyl orange) in water bodies, such as photodegradation or microbial degradation, all have many drawbacks. Photodegradation efficiency depends on the intensity and wavelength of the light source, the catalyst has low stability, and the treatment cost is high, making it easily limited by environmental conditions. Microbial degradation, on the other hand, has a long treatment time, and the growth of microorganisms is easily affected by organic pollutants, so it has very strict requirements for environmental conditions and may produce secondary pollution.

[0003] Contact electrocatalysis (CEC) is a strategy that applies the principle of contact electrification to catalytic reactions. It combines the relationship between electron transfer during contact electrification and the catalytic reaction, thereby increasing the rate of chemical reactions. Compared to photodegradation and microbial degradation, contact electrocatalysis, based on the triboelectric sequence between the catalyst and water molecules, provides appropriate mechanical energy to promote the transfer of electrons between the catalyst and water. This results in the generation of a large number of reactive oxygen species (ROS) in the overall reaction system, such as H3O+ and -OH, while also restoring the catalyst to a non-charged state. As long as appropriate mechanical energy is continuously provided to the reaction system, this electron transfer cycle will not stop, thereby increasing the degradation rate of pollutants.

[0004] To continuously provide mechanical energy to enhance ROS generation within the reaction system, different ultrasonic oscillation power and frequency can be used to maintain CEC performance. The power and frequency of the ultrasound affect the number and size of bubbles generated within the reaction system. During the formation and disintegration of these bubbles, new catalytic surfaces are continuously provided, increasing the catalytic surface area and improving the reaction rate. Furthermore, uniform vibration also helps to evenly disperse the reactants near the catalyst surface, increasing the overall reaction efficiency.

[0005] In comparison, the CEC degradation method is more efficient and faster, and can adapt to different environmental conditions; the catalyst has high stability, is not easily deactivated, and is easy to operate, requiring no complex condition control, thus avoiding secondary pollution caused by microbial degradation.

[0006] However, the materials currently used for CEC are mainly fluorinated polymers, which have high manufacturing costs and low Tg points. For example, the appropriate operating temperature of polytetrafluoroethylene (PTFE) is only between 20 and 30°C, which means that the ultrasonic-driven CEC reaction system requires additional cooling devices. Not to mention that the production of fluorinated polymers involves the addition of perfluorooctanoic acid, a carcinogenic toxin, which harms the environment and human health. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a contact electrocatalyst based on PMMA polymer. By adding PMMA polymer to the reaction system, electrons are continuously generated through continuous input of mechanical energy, producing a large number of reactive oxygen species and increasing the degradation efficiency of organic pollutants.

[0008] Accordingly, in a general embodiment of the present invention, a contact electrocatalyst is provided, comprising a modified PMMA polymer, the surface of which contains a plurality of functional monomers, wherein the side chains of the functional monomers are configured with electron-withdrawing groups, including carbon-oxygen bonds (CO), carbonyl groups (C=O), ester groups (-COOR), or carbon dangling bonds (C-), thereby improving the electron-withdrawing ability of the surface layer.

[0009] The above-described embodiments of the contact electrocatalyst may also include one or more of the following.

[0010] In some embodiments, the surface work function of the modified PMMA polymer is greater than 4.5 eV and less than or equal to 7.4 eV.

[0011] In some implementation schemes, the ratio of the functional monomers is 0.1 to 10%, based on the total number of the structural monomers and the functional monomers.

[0012] In the sample used in the above embodiments, the molecular weight of the modified PMMA polymer is between 100,000 and 2,000,000.

[0013] In a preferred embodiment, the electron-withdrawing group includes a carbon dangling bond (C-); the surface work function of the modified PMMA polymer is greater than 6.6 eV and less than or equal to 7.4 eV; the ratio of the functional monomer to the total number of the structural monomers and the functional monomers is 2 to 8%; and the molecular weight of the modified PMMA polymer is 900,000 to 1,200,000.

[0014] In other embodiments of the present invention, there is a method for preparing a contact electrocatalyst, comprising: treating a PMMA polymer with plasma for a period of time to convert the side chain groups of the structural monomers on the surface of the PMMA polymer into electron-withdrawing groups to form functional monomers, thereby obtaining a modified PMMA polymer, wherein the electron-withdrawing groups include carbon-oxygen bonds (CO), carbonyl groups (C=O), ester groups (-COOR), or carbon dangling bonds (C-), wherein R is a group with any number of carbon atoms.

[0015] In a configuration commonly used in the above embodiments, the plasma treatment includes bombarding the PMMA polymer with a plasma of 200 to 4000 watts in a plasma gas atmosphere for a time, wherein the time is 10 to 300 seconds, and the plasma gas atmosphere contains helium, argon, neon, nitrogen, or air.

[0016] In the sample commonly used in the above embodiments, the ratio of the functional monomer to the total number of the structural monomer and the functional monomer in the modified PMMA polymer is 0.1 to 10%.

[0017] In some other embodiments of the present invention, there is a method for degrading organic pollutants, which includes: adding a contact electrocatalyst to a pollution source in a molar ratio according to the molar number of organic pollutants in the pollution source to carry out electrocatalytic degradation of the organic pollutants, wherein the contact electrocatalyst includes the contact electrocatalyst as described above or the contact electrocatalyst prepared by the method described above.

[0018] In the general embodiments described above, the pollution source includes industrial wastewater, domestic wastewater, agricultural wastewater, and soil and groundwater; the organic pollutant includes monoazo dyes, diazo dyes, triazo dyes, or polyazo dyes. Simple Explanation of the Diagram

[0019] Figure 1A is a molecular chain transformation diagram illustrating the redox reactions during the plasma treatment of PMMA polymer. Figure 1B is a cartoon illustration illustrating the specific configuration of the plasma process chamber; Figure 2 shows photographs illustrating the color changes of different embodiments after reacting with liquid samples; Figures 3A to 3C are curve graphs, line graphs, and bar graphs showing the degradation rates of methyl orange in different embodiments; Figure 4A is a photograph showing the color change of the powder in Example 3 after vibration degradation; Figure 4B shows the microscopic surface morphology of different embodiments after oscillation degradation as presented by scanning electron microscopy images; Figure 5 is a line graph showing the degradation effects of control examples and embodiments with different molecular weights; Figures 6A to 6B show the characteristic peak spectra, presenting the FTIR analysis results of Control Example 1, Example 3, and Example 6; Figure 6C is a molecular chain transformation diagram illustrating the chemical reaction results during the plasma treatment process in Examples 3 and 6; Figure 7A shows the surface morphology diagram, phase diagram, and phase distribution diagram, presenting the KPFM analysis results of Control Example 1, Control Example 2, Example 3, and Example 6. Figure 7B is a schematic diagram showing the work function measurement results of Comparative Example 1, Comparative Example 2, Example 3, and Example 6; Figure 8 is a bar chart showing the recyclability test results of Example 3; and Figure 9 is a line graph showing the timeliness test results of Example 3. Implementation

[0020] The first embodiment of the present invention provides a contact electrocatalyst comprising a modified polymer containing a plurality of functional monomers, wherein the side chains of the functional monomers are configured with electron-withdrawing groups.

[0021] In a common embodiment, the modified polymer is a modified PMMA polymer, wherein, based on the total number of structural monomers and functional monomers of the modified PMMA polymer, the ratio of functional monomers is 0.1% to 10%, preferably 2% to 8%, and more preferably 3% to 5%; note that the term "total number" in this specification refers to a number, expressed in the chemical field as a molar number; understandably, functional monomers can be distributed in any part of the main chain or branches of the modified PMMA polymer, forming blocks or randomly distributed; naturally, when the modified PMMA polymer is in the form of powder, agglomerate, or film, the functional monomers can be located on the surface or in the inner layer below the surface; in several embodiments, the ratio of functional monomers refers to the ratio of functional monomers located on the surface of the modified PMMA polymer to the total number of structural monomers and functional monomers.

[0022] The term "electron-withdrawing group" in this invention refers to a chemical group with a relatively negative electrostatic sequence; in other words, it is a chemical group with a high electronegativity, having an average electronegativity of 2.70 to 3.50, preferably 2.90 to 3.05. In these embodiments, the electron-withdrawing group may include, for example, a carbon-oxygen bond (CO), a carbonyl group (C=O), an ester group (-COOR), a methyl group (CH3), or a carbon dangling bond (C-), wherein R is a group with any number of carbon atoms.

[0023] In all the above embodiments, the molecular weight of the modified PMMA polymer is from 100,000 to 2,000,000, preferably from 100,000 to 200,000, 200,000 to 300,000, 300,000 to 400,000, 400,000 to 500,000, 500,000 to 600,000, 600,000 to 700,000, 700,000 to 800,000, or 800,000 to 900,000. 900,000 to 1,000,000, 1,000,000 to 1,200,000, 1,200,000 to 1,400,000, 1,400,000 to 1,600,000, 1,600,000 to 1,800,000 or 1,800,000 to 2,000,000, preferably 700,000 to 800,000, 800,000 to 900,000, 900,000 to 1,000,000, 1,000,000 to 1,200,000.

[0024] In the above embodiments, the surface work function of the modified PMMA polymer is greater than 4.5 eV and less than or equal to 7.4 eV, such as 4.5 to 4.9 eV, 5.0 to 5.5 eV, 5.6 to 6.0 eV, 6.1 to 6.5 eV, 6.7 to 7.0 eV or 7.1 to 7.4 eV, preferably 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3 or 7.4 eV; more preferably, the surface work function is 7.4 eV.

[0025] In this embodiment, the form of the contact electrocatalyst is not particularly limited; it can be a powder or a sheet, and can be further prepared into a solution or a suspension. It is understood that a solution refers to suspending and dissolving the contact electrocatalyst in a compatible solvent, while a suspension refers to suspending and dispersing the contact electrocatalyst in an incompatible solvent. Compatible solvents may include, for example, water, methanol, ethanol, propanol, isopropanol, acetone, acetic acid, etc., and are not limited thereto. Incompatible solvents may include, for example, n-hexane, cyclohexane, n-heptane, benzene, toluene, diethyl ether, petroleum ether, etc., and are not limited thereto.

[0026] In some embodiments, the contact electrocatalyst is a powder with an average particle size of 1 to 100 μm, preferably 1 to 10 μm or 10 to 100 μm.

[0027] A second embodiment of the present invention provides a method for preparing a contact electrocatalyst, comprising: treating a PMMA polymer with plasma for a period of time to convert the side chain groups of the structural monomers on the surface of the PMMA polymer into electron-withdrawing groups to form functional monomers, thereby obtaining a modified PMMA polymer, wherein the electron-withdrawing groups include carbon-oxygen bonds (CO), carbonyl groups (C=O), ester groups (-COOR), and carbon dangling bonds (C-), wherein R is a group with any number of carbon atoms.

[0028] It is understood that the present invention uses plasma treatment to bombard PMMA polymer with plasma to generate a redox reaction, thereby replacing the side chain groups on the structural monomer with electron-withdrawing groups. Taking methyl methacrylate (MMA) as the structural monomer, as shown in Figure 1A, the side chain group is methyl formate. During the plasma treatment time, due to the plasma bombardment, some of the methyl formate groups of the structural monomer are cracked, exposing the electron of the second carbon of acrylic acid to form a carbon dangling bond (C-), thus transforming the structural monomer into an electron-deficient group.

[0029] The specific definitions of the physical properties of "structural monomers", "functional monomers", "electron-withdrawing groups" and "modified PMMA polymers" in the second embodiment, including molecular weight, ratio of functional monomers, average electronegativity, work function, etc., have been explained in detail in the first embodiment and will not be repeated here.

[0030] In this embodiment, the specific conditions of the plasma treatment include: bombarding the PMMA polymer with a plasma of 200 to 4000 watts for 10 to 300 seconds in a plasma gas atmosphere, wherein the plasma gas atmosphere contains helium, argon, neon, nitrogen or air.

[0031] Specifically, as shown in Figure 1B, PMMA polymer (P1) is placed in a plasma process chamber (1) and continuously bombarded by plasma (3) generated by a plasma source (2) to convert it into a modified PMMA polymer (P2). The structure of the plasma process chamber (1) is not particularly limited. Any chamber that can define a space to accommodate the powder form of PMMA polymer or its suspension solution and has any suitable plasma source, such as remote, microwave, capacitively coupled plasma (CCP) or inductively coupled plasma (ICP), can be used as a suitable plasma process chamber.

[0032] The flow rates and other processing parameters described below are for suspensions; it should be understood that these parameters may be adjusted based on the volume of the suspension being processed and the type of chamber used without departing from the embodiments disclosed herein.

[0033] In a specific example, the plasma source includes one or more of capacitively coupled plasma, inductively coupled plasma, pulsed discharge plasma, hot filament, electron cyclotron resonance plasma, or atmospheric pressure plasma.

[0034] In these examples, the plasma gas atmosphere comprises helium (He), argon (Ar), neon (Ne), nitrogen (N2), or air, wherein the flow rate of the plasma gas is 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 L / min; preferably, the flow rate of the plasma gas is set to 7, 8, 9, 10, 11, 12, or 13 L / min; more preferably, the flow rate of the plasma gas is set to 10 L / min.

[0035] In these examples, the PMMA polymer is treated with plasma for at least 10 to 20 seconds, 20 to 30 seconds, 30 to 45 seconds, 45 to 60 seconds, 60 to 75 seconds, 75 to 90 seconds, 90 to 120 seconds, 120 to 150 seconds, 150 to 200 seconds, 200 to 250 seconds, or 200 to 300 seconds; preferably, at least 20 to 30 seconds, 30 to 45 seconds, 45 to 60 seconds, 60 to 75 seconds, 75 to 90 seconds, 90 to 120 seconds, or 120 to 150 seconds; more preferably, at least 30 to 45 seconds, 45 to 60 seconds, 60 to 75 seconds, or 75 to 90 seconds.

[0036] In these examples, the plasma is generated by a plasma source with a power of less than or equal to 4000 watts, 3000 watts, 2000 watts, 1000 watts, 500 watts, or 200 watts; preferably, the plasma is implemented with a power of less than or equal to 3000 watts, 2000 watts, or 1000 watts; more preferably, the plasma is implemented with a power of 1000 to 3000 watts.

[0037] In some examples, the plasma is a pulsed plasma with a duty cycle of less than or equal to 75%, 70%, 65%, 60%, 55%, 50%, 45%, or 40%, and a frequency in the range of 50 Hz to 100 Hz, or in the range of 60 Hz to 90 Hz, or in the range of 70 Hz to 80 Hz; in another example, the plasma is a continuous plasma that operates with a duty cycle of 100%.

[0038] In these examples, the surface of the suspension solution is at a first distance D1 from the plasma source, which is less than or equal to 10 cm, 9.5 cm, 9.0 cm, 8.5 cm, 8.0 cm, 7.5 cm, 7.0 cm, 6.5 cm, 6.0 cm, 5.5 cm, 5.0 cm, 4.5 cm, 4.0 cm, 3.5 cm, or 3.0 cm; preferably, the first distance D1 is 8.0 cm, 7.5 cm, 7.0 cm, 6.5 cm, 6.0 cm, 5.5 cm, or 5.0 cm; more preferably, the first distance D1 is 6.5 cm.

[0039] In these examples, the surface of the suspension solution is at a second distance D2 from the bottom of the plasma process chamber. This second distance D2 is less than or equal to 1.0 cm, 0.9 cm, 0.8 cm, 0.7 cm, 0.6 cm, 0.5 cm, 0.4 cm, 0.3 cm, 0.2 cm, or 0.1 cm; preferably, the second distance D2 is less than or equal to 0.7 cm, 0.6 cm, 0.5 cm, 0.4 cm, or 0.3 cm; more preferably, the second distance D2 is less than or equal to 0.5 cm.

[0040] In the above-described embodiments, the contact electrocatalyst is further subjected to centrifugation and drying to form catalyst powder. The drying temperature depends on the glass transition temperature (Tg) of the contact electrocatalyst. It is understood that when the drying temperature is higher than the Tg temperature, the catalyst will be deactivated. Specifically, the drying temperature can be controlled between 40 and 60°C.

[0041] In an aquatic environment, the side chain groups of modified PMMA polymer undergo mechanical action, causing electrons from water molecules to transfer to carbon dangling bonds (C-) according to a triboelectric sequence. After losing electrons, the water molecules are converted into H2O*. Through rapid proton conversion, H3O+ and -OH are generated. When electrons on the surface of the modified PMMA polymer collide with the modified PMMA polymer, O2 molecules capture electrons to form O2-, restoring the modified PMMA polymer to its original uncharged state. As long as this mechanical energy continues to exist, this cycle will not stop.

[0042] A third embodiment of the present invention provides a method for degrading organic pollutants, comprising: adding a contact electrocatalyst to a pollution source in a molar ratio based on the molar number of organic pollutants in the pollution source to perform electrocatalytic degradation of the organic pollutants, wherein the contact electrocatalyst comprises the contact electrocatalyst provided as in the first embodiment or the second embodiment.

[0043] In a variety of implementation schemes, the pollution source primarily includes industrial wastewater, domestic wastewater, agricultural wastewater, and soil and groundwater; industrial wastewater includes, for example, wastewater from the textile industry, paper industry, leather industry, food processing industry, cosmetics manufacturing industry, paint and coating industry, printing industry, pharmaceutical industry, petrochemical industry, or oil refining industry, and contains organic pollutants including volatile organic compounds, non-volatile organic compounds, halogenated organic compounds, non-halogenated organic compounds, polycyclic aromatic hydrocarbons, aliphatic hydrocarbons, heterocyclic hydrocarbons, petroleum hydrocarbons, organic solvents, and polymers.

[0044] In a variety of embodiments, the organic pollutant includes, but is not limited to, industrial dyes, such as azo dyes, anthraquinone dyes, triphenylmethane dyes, indigo dyes, sulfur dyes, aniline dyes, or phthalocyanine dyes.

[0045] In some embodiments, the azo dye can be a monoazo dye, a diazo dye, a triazo dye, or a polyazo dye. Among them, monoazo dyes include, for example, methyl orange, methyl red, orange G, and azobenzene; diazo dyes include, for example, Congo red; and triazo dyes include, for example, Direct Red 23.

[0046] In some embodiments, the molar ratio of the contact electrocatalyst to the organic pollutant is 1:(0.1 to 10), preferably 1:(0.5 to 5), 1:(0.8 to 2), or 1:(0.85 to 1).

[0047] In some embodiments, while performing electrocatalytic degradation, ultrasonic treatment is simultaneously performed on the mixture of the contact electrocatalyst and organic pollutants. The conditions for the ultrasonic treatment include: setting the ultrasonic power to be greater than or equal to 50W, 100W, 150W, 200W, 250W, 300W, 350W, or 400W; setting the ultrasonic frequency to be less than or equal to 20kHz, 25kHz, 30kHz, 35kHz, 40kHz, 45kHz, or 50kHz; and performing oscillation for at least 0.5 hours, 1.0 hours, 1.5 hours, 2.0 hours, 2.5 hours, 3.0 hours, 3.5 hours, 4.0 hours, 4.5 hours, 5.0 hours, 5.5 hours, or 6.0 hours.

[0048] In some preferred embodiments, the ultrasonic power is set to be greater than or equal to 100W, 150W or 200W, the ultrasonic frequency is set to be less than or equal to 30kHz, 35kHz, 40kHz, 45kHz or 50kHz, and the oscillation is performed for at least 1.0 hour, 2.0 hours, 3.0 hours or 4.0 hours.

[0049] [Example] [1 (PMMA-30)]

[0050] Take 1 gram of PMMA powder with a molecular weight of 996K, place it in a scintillation bottle, and add deionized water to a depth of 0.5 cm from the bottom of the bottle; set the plasma generator to a power of 3000 watts, set the argon flow rate to 10 L / min, and place its outlet at a height of 6.5 cm from the liquid surface, the same height as the bottle opening.

[0051] After starting the plasma machine, perform plasma treatment for 30 seconds. After the treatment is completed, centrifuge the modified PMMA powder with deionized water for 30 minutes to separate the modified PMMA powder from the deionized water. Then dry the modified PMMA powder in an oven at 50°C.

[0052] [Example] [2 (PMMA-45)]

[0053] It is largely the same as Example 1, except that the plasma treatment lasts for 45 seconds.

[0054] [Example] [3 (PMMA-60)]

[0055] It is largely the same as Example 1, except for the plasma treatment lasting 60 seconds.

[0056] [Example] [4 (PMMA-75)]

[0057] It is largely the same as Example 1, except that the plasma treatment lasts for 75 seconds.

[0058] [Example] [5 (PMMA-90)]

[0059] It is largely the same as Example 1, except for the plasma treatment lasting 90 seconds.

[0060] [Example] [6 (PMMA-120)]

[0061] It is largely the same as Example 1, except that the plasma treatment lasts for 120 seconds.

[0062] [Comparison Example] [1 (PMMA-0)]

[0063] It is largely the same as Example 1, except that no plasma treatment was performed.

[0064] [Comparison Example] [2 (PMMA-80K)]

[0065] It is largely the same as Example 3, except that PMMA powder with a molecular weight of 80K is used.

[0066] [Experimental Example] [1-PMMA] [Powder Vibration Degradation of Methyl Orange] [(I)]

[0067] Take 0.15 g of each of Examples 1 to 6 and Comparative Example 1, place them in a new scintillation bottle, and add 10 mL of methyl orange solution with a concentration of 5 ppm. Place the scintillation bottle in an ultrasonic vibrator for vibration treatment: power 150 W, frequency 40 kHz; vibration time is 1 hour each time, and data are recorded each time.

[0068] On the other hand, referring to Figure 2, the appearance color changes of the liquid samples corresponding to Examples 1 to 3 are more significant. Obviously, methyl orange degrades under the action of Examples 1 to 3, resulting in a decrease in concentration. Furthermore, the concentration change of methyl orange solution was analyzed by ultraviolet-visible spectrophotometer (UV-VIS) after centrifugation of the liquid samples. The results are shown in Figures 3A to 3C. The absorbance at a specific wavelength (464 nm) shows that the concentration of methyl orange changes with the shaking treatment time. According to Beer-Lambert's law, as the shaking treatment time increases, the degradation rate in the liquid samples corresponding to Examples 1 to 4 also gradually increases. Among them, the degradation rate of Example 3 reached 85% after 4 hours of shaking treatment, but the degradation rate of Example 6 did not increase significantly compared with Control Example 1.

[0069] As shown in Figure 4A, observing the appearance of the powder, it can be seen that the color of the powder in Example 3 did not change after being degraded by shaking, indicating that no physical adsorption of methyl orange occurred during the shaking degradation process.

[0070] Further, SEM images of the modified PMMA powders of Comparative Example 1, Example 3 and Example 6 were taken; as shown in Figure 4B, whether it is untreated PMMA powder or modified PMMA powder treated with different plasma times, its surface morphology and appearance did not change significantly after vibration degradation, indicating that the vibration degradation process did not have any impact on the physical morphology of the modified PMMA powder, showing that its structural stability is good.

[0071] [Experimental Example] [2-] Modification [PMMA] [Powder Vibration Degradation of Methyl Orange] [(II)]

[0072] To test whether PMMA of different molecular weights has any effect on the electrocatalytic degradation effect, UV-Vis analysis was performed on Control Example 2 and Example 3. As shown in Figure 5, the degradation rate of Control Example 2 after 4 hours was only about 20%, which was much lower than that of Example 3 after 4 hours. Obviously, a larger molecular weight is beneficial to improving the electrocatalytic degradation effect.

[0073] [Experimental Example] [3-] [FTIR] [Measurement]

[0074] FTIR analysis was performed on control example 1, example 3 and example 6 to infer the bond changes of the modified PMMA polymer.

[0075] Figure 6A shows the FTIR spectra of Control Example 1, Example 3 and Example 6. It can be observed that all three samples show the main characteristic peak of PMMA.

[0076] Figure 6B shows the magnified FTIR spectra of the powders from Comparative Example 1, Example 3, and Example 6. It shows that after plasma treatment, the strengths of C–C, C–O, C=O, and CH₃ bonds all decreased. This indicates that the plasma broke many chemical bonds and may have generated a large number of carbon dangling bonds (C-).

[0077] Based on this, as shown in Figure 6C, it can be inferred that plasma treatment induces PMMA to first break down from the C-C bonds, forming a large number of carbon dangling bonds (C-), as in Example 3. Since carbon dangling bonds (C-) are electron-deficient structures, they can enhance the ability of PMMA polymer to capture electrons from water, significantly improving catalytic degradation performance. In Example 6, due to the excessively long plasma treatment time, the carbon dangling bonds (C-) combine with the plasma-excited -OH groups in the aqueous environment to form C-OH bonds, reducing the proportion of carbon dangling bonds (C-) in the PMMA polymer and thus affecting its catalytic degradation effect.

[0078] [Experimental Example] [4-KPFM] [analyze]

[0079] KPFM analysis was performed on the surface roughness and phase change of the modified PMMA polymers in Control Example 1, Control Example 2, Example 3 and Example 6.

[0080] Figure 7A shows the surface morphology of AFM for Control Example 1, Control Example 2, Example 1 and Example 6 in the left column, presenting their roughness at the nanoscale. Since there is no significant difference in surface roughness, the influence of roughness on the degradation of methyl orange can be ruled out.

[0081] The middle column of Figure 7A shows its KPFM phase image. It can be seen that Example 3 has the most negative phase, followed by Example 6. The right column of Figure 7A shows its phase distribution. It can be seen that Comparative Example 1, Comparative Example 2, Example 1 and Example 6 all show a single Gaussian function curve, indicating that the surface potential distribution is relatively uniform.

[0082] Furthermore, the surface work function of the modified PMMA polymer was analyzed using KPFM. Specifically, gold (Au) was used as a standard sample, and a DC bias voltage (VCPD) was applied to the probe and the sample to calculate the work function on the sample surface. As shown in Figure 7B, the measurement results show that the work functions of Control Example 1 and Control Example 2 are 4.9 eV and 4.7 eV, respectively, while the work functions of Example 3 and Example 6 are 7.4 eV and 6.6 eV, respectively. Obviously, after plasma treatment, the difference in Fermi level between the modified PMMA powder and water is increased, and the greater the potential difference, the stronger the electron transfer ability. Among them, the work function of Example 6 is as high as 7.4 eV, which makes it easy to accept electrons from water during the degradation process and has the best electro-contact degradation effect.

[0083] [Experimental Example] [5-] [Recyclability Test]

[0084] Following the method described in Experimental Example 1, the modified PMMA powder from Example 3 was subjected to ultrasonic oscillation to degrade methyl orange. After each reaction, the methyl orange solution and the modified PMMA powder were separated, and the modified PMMA powder was dried. The above oscillation degradation test was repeated 5 times, and the methyl orange degradation rate was recorded each time.

[0085] As shown in Figure 8, after each 4-hour shaking degradation reaction, the degradation rate of methyl orange remained at 88%. This demonstrates that even after repeated use, the modified PMMA powder can still maintain high catalytic performance and stable degradation effect on methyl orange, showing that these materials have durability and reusability.

[0086] [Experimental Example] [6-] [Aging Test of Electrically Contacted Catalysts]

[0087] Following the method described in Experimental Example 1, the freshly prepared modified PMMA powder of Example 3 was subjected to ultrasonic oscillation for 4 hours, and its methyl orange degradation rate reached approximately 89%. After the reaction, the methyl orange solution and modified PMMA powder were separated. The modified PMMA powder was dried and placed for 1 month, and the aforementioned test was repeated. As shown in Figure 9, the methyl orange degradation rate of the modified PMMA powder after 1 month of placement only decreased slightly to 85%, which indicates that the PMMA powder treated with appropriate plasma can still maintain good catalytic performance after long-term storage.

[0088] The contact electrocatalyst provided by this invention specifically achieves the following beneficial effects:

[0089] Firstly, plasma modification using polymer as a base increases the superoxide hydrogen substitution rate on the powder surface, which is beneficial for generating a large number of reactive oxygen species in water. Secondly, the increase in surface work function and the lower charge transfer resistance between powders increase electron transfer efficiency, which helps to improve the degradation rate of organic pollutants, including methyl orange.

[0090] Secondly, after the plasma-modified polymer powder is placed in polluted water for electrocatalytic degradation, the powder surface is not damaged or physically attached to organic pollutants. Its structure is stable, and the recycled powder can be repeatedly used for electrocatalytic degradation, maintaining a considerable degradation rate and thus being reusable. On the other hand, the recycled powder can also maintain high degradation performance after long-term storage, thus possessing durability.

[0091] Third, the raw materials for modified PMMA polymers are readily available, and the manufacturing process is simple, which is conducive to industrial mass production.

[0092] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention; it is obvious to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without creative effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

[0093] 1: Plasma process chamber 2: Plasma source 3: Plasma P1: PMMA polymer P2: Modified PMMA polymer

Claims

1. A contact electrocatalyst comprising a modified PMMA polymer, wherein the surface layer contains a plurality of functional monomers, wherein, The side chain of this functional monomer is configured with electron-withdrawing groups, which include carbon-oxygen bonds (CO), carbonyl groups (C=O), ester groups (-COOR), or carbon dangling bonds (C-), wherein R is a group with any number of carbon atoms, and the molecular weight of the modified PMMA polymer is 100,000 to 2,000,000.

2. The contact electrocatalyst as described in claim 1, wherein, The surface work function of this modified PMMA polymer is greater than 4.5 eV and less than or equal to 7.4 eV.

3. The contact electrocatalyst as described in claim 1, wherein: The electron-withdrawing groups include carbon dangling bonds (C-); the surface work function of the modified PMMA polymer is greater than 6.6 eV and less than or equal to 7.4 eV; the molecular weight of the modified PMMA polymer is 900,000 to 1,200,000.

4. A method for preparing a contact electrocatalyst, comprising: A PMMA polymer is subjected to plasma treatment for a certain period of time to convert the side chain groups of the structural monomers on the surface of the PMMA polymer into electron-withdrawing groups to form functional monomers, thereby obtaining a modified PMMA polymer. The electron-withdrawing groups include carbon-oxygen bonds (CO), carbonyl groups (C=O), ester groups (-COOR), or carbon dangling bonds (C-), where R is a group with any number of carbon atoms.

5. The preparation method as described in claim 4, wherein, The plasma treatment includes bombarding the PMMA polymer with a plasma of 200 to 4000 watts in a plasma gas atmosphere for a time of 10 to 300 seconds, wherein the plasma gas atmosphere contains helium, argon, neon, nitrogen, or air.

6. The preparation method as described in claim 4, wherein, The plasma treatment uses a plasma source including one or more of capacitively coupled plasma, inductively coupled plasma, pulsed discharge plasma, hot wire, electron cyclotron resonance plasma, or atmospheric pressure plasma.

7. A method for degrading organic pollutants, comprising: Based on the mole number of organic pollutants in a pollution source, a contact electrocatalyst is added to the pollution source in a mole ratio to carry out electrocatalytic degradation of the organic pollutants, wherein the contact electrocatalyst includes the contact electrocatalyst as described in any one of claims 1 to 3 or the contact electrocatalyst prepared by the method described in any one of claims 4 to 6.

8. The method as described in claim 7, wherein, The pollution sources include industrial wastewater, domestic wastewater, agricultural wastewater, and soil and groundwater; the organic pollutants include monoazo dyes, diazo dyes, triazo dyes, or polyazo dyes.

9. The method as described in claim 7, wherein, The molar ratio of the contact electrocatalyst to the organic pollutant is 1:(0.1 to 10).

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