Electrically conductive polymer composites containing iron oxide / hydroxide and their preparation using high ferrate

Abstract

The main subject of the present invention is an electrically conductive polymer composite comprising iron oxide / hydroxide, comprising a) an electrically conductive polymer, and b) an iron oxide / hydroxide compound incorporated into the electrically conductive polymer, wherein the composite comprises an iron oxide / hydroxide compound other than magnetite, and the electrically conductive polymer is different from polyaniline (PANI). Another subject of the present invention is a method for electrochemically producing the above-mentioned electrically conductive polymer composite by one of the following methods: Method I, comprising the steps of: a) providing a layer of electrically conductive polymer; b) electrochemically reducing the layer of electrically conductive polymer; c) contacting the reduced layer of electrically conductive polymer with an aqueous solution of high-iron ferrate ions; d) optionally repeating steps b) and c); e) optionally isolating and drying the obtained composite; or Method II, comprising the steps of: a) providing a layer of electrically conductive polymer; b) contacting the layer of electrically conductive polymer with an aqueous solution of high-iron ferrate ions; c) electrochemically oxidizing the layer of electrically conductive polymer in the aqueous solution of high-iron ferrate ions; d) electrochemically reducing the oxidized layer of electrically conductive polymer in the aqueous solution of high-iron ferrate ions; e) optionally repeating steps c) and d); e) optionally isolating and drying the obtained composite.

Description

Technical Field

[0001] This invention relates to conductive polymer composites containing iron oxides / hydroxides and methods for preparing them using ferrates via electrochemical methods. Background Technology

[0002] Composite materials containing conductive polymers and metal (particularly metal oxides) nanoparticles are widely used in the fields of electrocatalysis, sensors (e.g., electronic, electrochromic, or optical sensors) and microelectronics.

[0003] Various methods for producing the aforementioned composite materials are known, among which electrochemical methods are of particular interest from a practical standpoint due to their low cost and high efficiency. In these electrochemical methods, conductive polymer layers can be directly prepared on a substrate surface from a solution containing the monomers.

[0004] In conductive polymers, such as poly(3,4-ethylenedioxythiophene) (PEDOT) or poly(3,4-ethylenedioxypyrrole) (PEDOP), it is suitable for the electrochemical production of composites containing MnO2 or WO3 [Liu R, Duay J, Lee SB (2010) Redox exchange induced MnO2 nanoparticle enrichment in poly(3,4-ethylenedioxythiophene) nanowires for electrochemical energy storage. ACS Nano 4 (2010) 4299–4307., DV Zhuzhelskii, EGTolstopjatova, AI Volkov, SN Eliseeva, GGLáng, VV Kondratiev, Insights on the electrodeposition mechanism of tungsten oxide into conducting polymers: Potentiostatic vs. potentiodynamic deposition, Synthetic Metals 267(2020)116469, AONizhegorodova, SNILE Eliiseeva, EGTolstopjatova, GGLáng, D. Zalka, M. Ujvári, VV Kondratiev, EQCM study of redox properties of PEDOT / MnO2 composite films in aqueous electrolytes, Journal of Solid State Electrochemistry 22(2018)2357–2366.]. In the aforementioned publications, deposition was carried out in acidic or neutral solutions because the electrochemical properties of the conductive polymers PEDOT and PEDOP are more favorable in acidic media. Furthermore, PEDOT films, especially PEDOP films, deposited on substrates are not sufficiently stable in alkaline media.

[0005] Among metal oxide nanoparticles, iron oxide, especially conductive polymers containing magnetic magnetite (Fe3O4), has attracted particular attention for practical applications. They can be used as contrast agents in magnetic resonance imaging (MRI) and magnetic recording media, biomolecular separation, heterogeneous catalysis, environmental and food analysis, and immunoassays. Therefore, only a few methods for preparing composite materials are documented in the literature. Shin et al. disclosed a method (S. Shin, J. Jang, Chemical Communications 41 (2007) 4230; S. Shin, H. Yoon, J. Jang, Catalysis Communications 10 (2008) 178) in which the monomer of the conductive polymer (specifically, 3,4-ethylenedioxythiophene, EDOT) reacts with Fe3O4 in the presence of a strong acid (HCl). The resulting polymer (Fe3O4-PEDOT) is used for adsorbing heavy metal ions and photocatalytically decomposing organic dyes. A drawback of this method is that the strong acid decomposes the magnetic clusters of the nanostructure, and the magnetic nanoparticles dissolve in HCl, forming water-soluble Fe3O4 nanoparticles. 3+ / Fe 2+ The presence of ions leads to a decrease in magnetite content. It is noteworthy that no other iron oxides / hydroxides form in the strongly acidic medium; therefore, the solution contains only the chloride salts of the aforementioned iron ions.

[0006] In the process developed by Reddy et al. (KRReddy, W. Park, BCSin, J. Noh, and Y. Lee, Journal of Colloid and Interface Science, vol. 335, no. 1, pp. 34-39, 2009), dispersed core-shell composite materials were prepared by in-situ polymerization of EDOT monomers in a micellar solution of lignin sulfonic acid in the presence of magnetic nanoparticles (Fe3O4). It was noted that the diffraction pattern of magnetite (Fe3O4) showed no signs of impurities, indicating that the material was considered pure.

[0007] Zheng et al. (M. Zheng, J. Huo, Y. Tu, J. Jia, J. Wu, and Z. Lan, RSC Advances, vol. 6, no. 2, pp. 1637-1643, 2016) formed PEDOT / Fe3O4 thin films by spin-coating an EDOT precursor solution doped with Fe3O4 onto fluorinated tin oxide (FTO) glass and then polymerizing it. This technique requires many preparation steps, is time-consuming, and has low cost-effectiveness. The produced thin films were used as counter electrodes in dye-sensitized solar cells (DSSCs).

[0008] There are also reports in the literature on the preparation of core-shell composite materials containing γ-Fe2O3 and polyaniline or polypyrrole [R. Gangopadhyay A.De, Conducting Polymer Nanocomposites: A Brief Overview, Chemistry of Materials 12 (2000) 608-622.].

[0009] An important point is that in the fabrication of core-shell systems, polymers are deposited on the surface of pre-formed magnetite or hematite nanoparticles. Therefore, the "composite material" is actually composed of a set of tiny spherical units, and the polymer does not form a coherent matrix. This property of composite materials is detrimental in terms of mechanical stability, and such aggregated composites are clearly unsuitable for applications where they may undergo severe mechanical deformation.

[0010] Qin et al. (Journal of Inorganic and Organometallic Polymers and Materials, published online: July 14, 2020; https: / / doi.org / 10.1007 / s10904-020-01666-8; title: Acid Assisted One Step In Situ Polymerization Synthesis of PANI / α-Fe2O3 / β-FeOOH Composites and Its Formation Mechanism) proposed a polyaniline (PANI)-based composite material. During its preparation, a composite material containing iron oxide / hydroxide is formed, wherein polymerization is carried out in the presence of FeCl3. Therefore, the final polymer contains FeCl3 in its chains. The final step of this method is to grind the resulting solid material into powder. Prasanna et al. used a similar procedure to prepare PANI / FeCl3 composite materials (in which case, powdered materials were obtained) (Synthesis of polyaniline / alfa-Fe2O3 nanocomposite electron material for supercapacitor applications; Materials Today Communications (2017), vol 12, 72-78).

[0011] The methods described for producing composite materials containing iron oxides / hydroxides embedded in a conductive polymer matrix are not electrochemical methods. Furthermore, in known methods, magnetite (Fe3O4) particles, or in the case of PANI, Fe2O3 / FeOOH particles, are incorporated into the system during the polymerization step, rather than after the polymer film has formed. Summary of the Invention

[0012] This invention provides a simple, economical, and reproducible electrochemical method for preparing conductive polymer composites containing iron oxides / hydroxides. The conductive polymer can be, for example, poly(3,4-ethylenedioxythiophene) (PEDOT), polyaniline (PANI), poly(o-phenylenediamine) (PoPD), preferably poly(3,4-ethylenedioxythiophene) (PEDOT) or polyaniline (PANI) or other polymers with similar structures.

[0013] In embodiments of the invention, the preferred conductive polymer is poly(3,4-ethylenedioxythiophene), or PEDOT, a conductive polymer with good conductivity and well-controllable photoelectric and redox properties. The alkylene dioxy substituents on the polythiophene backbone are used to improve electrochemical, optical, and electrochromic properties. PEDOT is a widely used conductive polymer due to its stability and reproducibility. It is found in TNT sensors, hydrogen chloride and ammonia vapor detectors, NO2 sensors, neural probes, uric acid and dopamine sensors, and other medical sensors. In the case of PEDOT, the alkylene dioxy substituents on the polythiophene backbone are ethylenedioxy groups. In principle, similar polymers having a β-polythiophene backbone can also be used, wherein the optionally substituted alkylene dioxy substituents contain multiple carbon atoms, for example 3-12, preferably 3-8 carbon atoms. This thiophene monomer is described in the literature: a) JH Kang et al.: A Dual-Polymer Electrochromic Device with High Coloration Efficiency and Fast Response Time: Poly(3,4-(1,4-butylene-(2-ene)dioxy)thiophene)-Polyaniline ECD, Chem. Asian J., 2011, 6, 2123-2129; and b) LAEstrada: “Direct (Hetero)arylation Polymerization: An Effective Route to 3,4-Propylenedioxythiophene-Based Polymers with Low Residual Metal Content”, dx.doi.org / 10.102 / mz4003886I ACS Macro Lett. 2013, 2, 869-873). That is, the raw material can also be a polymer having a polythiophene backbone, wherein the thiophene monomer is optionally replaced by an alkylene dioxy group containing 2-12 carbon atoms. Preferred are those thiophene monomers replaced by alkylene dioxy groups containing 2-8 carbon atoms, especially those thiophene monomers replaced by alkylene dioxy groups containing 2 or 3 carbon atoms, among which PEDOT is considered the most preferred.

[0014] The normal oxidation / reduction of PEDOT is as follows:

[0015]

[0016] In embodiments of the invention, the polymer layer is preferably reinforced with a non-conductive polymer (e.g., polyphenols [preferably poly(bisphenol A)-PBPA], and polyolefins). Films reinforced with non-conductive polymers are more resistant to degradation caused by peroxidation that may occur during processing. That is, the reinforcing material is essentially "mechanical" (and therefore also called "mechanically reinforcing material") because the reinforcing polymer "fixes" the oxidized conductive polymer layer, which is easily peeled off from the substrate. Furthermore, it acts as a non-enclosed capping layer / cloud to protect the conductive polymer layer (e.g., substantially resisting UV radiation) without completely isolating it from the environment, allowing the conductive polymer to contact its surrounding medium.

[0017] Peroxidation is defined as the partial irreversible oxidation of a polymer at an applied positive potential, which can lead to significant structural changes or degradation of the polymer film [GGLáng, M.Ujvári, S.Vesztergom, V.Kondratiev, J.Gubicza, KJSzekeres: The Electrochemical Degradation of Poly(3,4-ethylenedioxythiophene) Films Electrodeposited from Aqueous Solutions, Z.Phys.Chem.2016(230)1281–1302.]. Inducing this phenomenon using cyclic voltammetry, we observed an oxidation peak at higher positive potentials, indicating that the polymer film is peroxidized, while no corresponding reduction peak was observed at more negative potentials.

[0018] Moderate peroxidation is also beneficial for the formation of composite materials because it increases the porosity of the membrane (which is also advantageous, for example, when used in sensors); while strong peroxidation leads to polymer degradation, polymer chain separation, and peeling from the substrate. Reinforcement with a non-conductive polymer also prevents polymer chain separation and membrane peeling. Irreversible deposition of PBPA on the surface of PEDOT membranes has been previously observed [E. Mazzotta, C. Malitesta, E. Margapoti, Direct electrochemical detection of bisphenol A at PEDOT-modified glassy carbon electrons, Anal. Bioanal. Chem. 405 (2013) 3587–3592.], however, this is considered a detrimental phenomenon due to electrode passivation, i.e., the advantages of the method according to the invention are not recognized. Based on passivation, it is assumed that a more closed (more “covered”) PBPA layer was deposited in this study than that described in the invention.

[0019] The basic feature of the method according to the present invention is that it reduces ferrate ions (FeO4) 2- Iron oxides / iron hydroxides are incorporated into electrodeposited conductive polymer films on inert substrates (gold, platinum, graphite, glassy carbon, conductive carbon layers, and carbon fibers). That is, the production of the conductive polymer layer and the incorporation of iron oxides and iron hydroxide compounds [including FeO(OH)] are spatially and temporally separate processes. Therefore, the conductive polymer layer can be formed under ideal conditions (i.e., only in the presence of necessary reagents), which improves its quality.

[0020] As used herein, the term "iron oxide" refers to any Fe(II) oxide (FeO), Fe(III) oxide (Fe2O3), and Fe3O4 (magnetite) containing Fe(II) and Fe(III) atoms or mixtures thereof in any proportion. The term "iron hydroxide" refers to any one of iron(II) hydroxide [Fe(OH)2] and iron(III) hydroxide [Fe(OH)3] or mixtures thereof in any proportion. The composite material may also contain a mixture of oxide-hydroxide [FeO(OH)].

[0021] As used herein, the term "iron oxide / hydroxide" refers to an iron-containing material comprising one or more compounds selected from Fe2O3, Fe3O4, Fe(OH)2, Fe(OH)3, and FeO(OH). In a preferred embodiment, the term "iron oxide / hydroxide" refers to an iron-containing material that substantially comprises one or more compounds selected from Fe2O3, Fe3O4, Fe(OH)2, Fe(OH)3, and FeO(OH), and optionally consists only of the listed compounds.

[0022] The ratio of iron oxide to iron hydroxide compounds (including FeO(OH) compounds) incorporated into the membrane can be altered through electrochemical reduction and oxidation of the composite material. Therefore, it is possible to obtain a composition in which Fe(III) or Fe(II) compounds typically constitute the majority, or magnetite (Fe3O4)—a compound containing a mixture of Fe(II) and Fe(III) ions—constitutes the majority. Theoretically, the production method according to the invention is also applicable to the synthesis of composite materials containing pure magnetite and composite materials without magnetite. However, in practice, when the electrochemical production method according to the invention is applied, other Fe(II) and Fe(III) compounds are formed in the composite in addition to magnetite. This composite material according to the invention differs from those known in the prior art (i.e., they are considered novel) because in known methods, pure magnetite is incorporated into the conductive polymer during polymer production [or if other Fe(II) and Fe(III) compounds are incorporated into the polymer (through simple copolymerization), PANI is the base polymer]. Magnetite is a fairly stable compound, difficult to dissolve even in strong acids. Therefore, the products of known methods starting from magnetite contain only other iron oxides / hydroxides as impurities (i.e., in amounts less than 1 wt%, typically only trace amounts). In the composite material according to the invention, the content of iron oxides / hydroxides other than magnetite, calculated from the total mass of the iron oxide / hydroxide compounds, is at most 100%, but typically at least 1-25 wt%, preferably 2-10 wt%.

[0023] Based on prior knowledge, the possibility of incorporating iron oxide / hydroxide nanoparticles into conductive polymer matrices from ferrate ions is unexpected, as ferrate ions are only stable in strongly alkaline media (pH >> 13, typically 14-15) and degrade rapidly in neutral or acidic media. Conversely, the electrochemical properties of conductive polymers are much worse in alkaline media, and they are readily degraded (e.g., polymer films deposited on supports are easily peeled off). Furthermore, ferrate ions are very strong oxidants in neutral and weakly alkaline media, and therefore can oxidize and degrade polymer chains. Presumably, for these reasons, ferrate ions have not previously been used to incorporate iron oxide / hydroxide compounds into conductive polymers. However, in our experiments, we found a pH range (7-13, preferably 9-12), which is not obvious to those skilled in the art, within which the aforementioned negative phenomena are only to a lesser extent, making it possible to use ferrate ions to incorporate iron oxide / hydroxide compounds into conductive polymers. That is, under these conditions, some conductive polymers (preferably PEDOT, polyaniline) remain sufficiently stable and electroactive, and the decomposition of ferrate ions occurs slowly enough to allow them to enter the polymer.

[0024] The non-obvious nature of the present invention is further confirmed by the fact that it is impossible to prepare iron oxide / hydroxide-containing composite materials by the methods described in this specification using known and widely used poly(3,4-ethylenedioxypyrrole) (PEDOP) conductive polymers, because the polymer becomes unusable (degrades) upon contact with a medium (alkaline solution containing ferrate ions).

[0025] Preparation of conductive polymer composites containing iron oxides / hydroxides

[0026] In a preferred embodiment of the invention, the conductive polymer layer is formed on the substrate surface by constant current polymerization (as described in Examples 1-7) or potentiodynamic deposition (as described in Example 8).

[0027] During constant current deposition, the current between the working electrode and the counter electrode remains constant, while the potential difference between the working electrode and the reference electrode is monitored in the cell as a function of time.

[0028] In potentiodynamic deposition (cyclic voltammetry or (dynamic) cyclotaxis of electrode potentials, or simply potentiodynamic cyclotaxis), the potential of the working electrode changes periodically according to an appropriately selected triangular signal, while the current flowing through the battery is measured. An advantage of this method is that the amplitude and frequency of the periodic potential perturbation can be selected based on the characteristics of the system. This method can also be used to incorporate iron into conductive polymers, as detailed below.

[0029] During the deposition of conductive polymers, the current density (j) is typically 0.05–1.00 mA / cm². 2 The preferred value is 0.1-0.3 mA / cm. 2 For example, 0.2 mA / cm 2 The reaction time is typically 500-15000 s, preferably 1000-8000 s, for example 1800 s or 3600 s. The pH of the solution is approximately neutral (e.g., pH = 5-8), and the reaction is preferably carried out at room temperature (T = 20-25 °C).

[0030] To form conductive polymers containing iron oxides / hydroxides, i.e., to incorporate iron into thin films, two types of electrochemical methods were employed:

[0031] 1. Polymers in the reduced state The reduction of ferrate ions occurs through a “reaction” between the polymer chains and the ferrate ions. Therefore, we operate within the electrode potential range where the polymer is in a reduced state, which can preferably be adjusted using a potentiostat. The appropriate potential range depends on the quality of the polymer and the reference electrode. Determining the appropriate electrode potential is within the knowledge of those skilled in the art. Potentials applied in neutral media (pH = 5-7) are typically in the range of (-0.45)–(+0.05) V, preferably (-0.35)–(-0.05) V [measured relative to a saturated sodium chloride-filled calomel electrode (SSCE)]. It is important to note that the polymer must be in a reduced state. .

[0032] The reduction of ferrate ions proceeds according to the following chemical reaction equations. In these equations, (P) - The term represents the negatively charged portion of the polymer chain, i.e., the "active site." (P) represents the active site in the neutral state, while (P...) + This indicates the oxidation state of the active site. To stabilize ferric acid root The reduction of ions is carried out under alkaline conditions, preferably at pH 10-14. .

[0033] 2FeO4 2– +10H3O + +6(P) – =Fe₂O₃ + 15H₂O + 6(P)

[0034] 3FeO4 2– +16H3O + +10(P) – =Fe3O4 + 24H2O + 10(P)

[0035] 2FeO4 2– +10H3O + +3(P )– =Fe₂O₃ + 15H₂O + 3(P)+

[0036] 3FeO4 2– +16H3O + +5(P) – =Fe3O4 + 24H2O + 5(P) +

[0037] FeO4 2– +5H3O + +3(P) – =Fe(OH)3 + 6H2O + 3(P)

[0038] FeO4 2– +5H3O + +3(P) – =FeO(OH) + 7H₂O + 3(P)

[0039] Based on the above, the redox reaction (electron transfer) occurs between the polymer chains and the active sites of ferrate ions. The state of the polymer membrane can be controlled by adjusting the electrode potential to an appropriate range (which can preferably be modified using a potentiostat). The reduced membrane must be removed from the electrolytic cell used for electrochemical reduction and immersed in a solution containing ferrate ions (thus bringing the membrane into contact with the ferrate ions). In this way, a reaction can occur between the active sites and the ferrate ions. By repeating the reduction and immersion steps, the content of iron oxide / hydroxide incorporated into the membrane can be gradually increased.

[0040] According to another production method, reduction is carried out in a ferrate-containing solution, and the resulting material is then immersed in the solution (relaxation) for 15-300 seconds, preferably 30-60 seconds (this is also an embodiment of the aforementioned "contact"). The iron content is increased by further adding ferrate solution and / or by repeating the steps (i.e., by repeating the reduction and immersion steps several times).

[0041] Furthermore, moderate overoxidation of the conductive polymer film can promote an increase in the content of incorporated iron oxides / hydroxides due to the appearance of cracks in the polymer structure (i.e., an increase in its porosity). Moderate overoxidation means that the conductive polymer is oxidized to a degree sufficient to cause irreversible partial oxidation. [In this case, in a neutral medium (pH = 5-7), the electrode potential (the positive potential limit under cyclization conditions) must be (+0.8)-(+1.2)V vs. SSCE, preferably (+0.9)-(+1.1)V vs. SSCE].

[0042] 2. At a sufficiently high positive electrode potential [which can preferably be adjusted using a potentiostat, the appropriate potential range depends on the quality of the polymer and the reference electrode; determining the appropriate electrode potential is common knowledge to those skilled in the art; importantly, The polymer must be in its oxidized state. [That is, forming positively charged positions on the chain], ferrate ions, i.e., negatively charged counterions (as negative ions, they compensate for the positive charge formed at a positive potential in the polymer membrane), enter the membrane immersed in a solution containing ferrate ions. Then, by changing the electrode potential in the negative direction, (parallel) reduction of the polymer chain and ferrate ions occurs, usually accompanied by positive ions (e.g., H3O). + The migration of ferrate ions and solvents. The applied potential window in the alkaline medium (pH = 10⁻¹²) is E = (-0.7) - (+0.4) V vs. SCE, preferably E = -0.4 - (+0.3) V vs. SCE (potassium chloride saturated calomel electrode). Based on the above, by changing the electrode potential in the negative direction, ferrate ions enter the membrane as counter ions and participate in the following reduction processes, for example:

[0043] 2FeO4 2– +10H3O + +6e – =Fe2O3 + 15H2O

[0044] 3FeO4 2– +16H3O + +10e – =Fe3O4 + 24H2O

[0045] FeO4 2– +5H3O + +3e – =Fe(OH)3 + 6H2O

[0046] FeO4 2– +5H3O + +3e – =FeO(OH) + 7H2O

[0047] Therefore, iron oxide / hydroxide compounds are formed through the direct electrochemical reduction of ferrate ions.

[0048] The content of iron oxide / hydroxide incorporated into the membrane can be gradually increased by repeating the oxidation and reduction steps. The repetition of the oxidation and reduction steps can be performed using cyclic voltammetry (also known as potentiodynamic cyclization).

[0049] By changing the electrode potential, electrochemically active iron oxide / hydroxide compounds (incorporated into the composite electrode in the form of nanoparticles) can interconvert according to the following reaction formula (this, of course, applies to the final products of the two methods mentioned above), for example:

[0050] 3Fe₂O₃ + 2H₃O + +2e – = 2Fe3O4 + 3H2O

[0051] 3Fe(OH)3 + H3O + +e – =Fe3O4 + 6H2O

[0052] 3FeO(OH) + H3O + +e – =Fe3O4 + 3H2O

[0053] Using both types of methods, ferrate treatment—that is, incorporating iron oxide / hydroxide particles into the polymer membrane—was observed to significantly improve the electrochemical properties of the polymer membrane. From a practical standpoint, it may be particularly interesting that the frequency-dependent capacity of the membrane increased in the mid-frequency range (see...). Figure 1 b)). This also means that the membrane can respond to sudden potential changes more quickly, making it more suitable for use in devices with supercapacitors (e.g., transient energy storage). Attached Figure Description

[0054] Figure 1 a) shows the cyclic voltammogram (the curve is recorded in the third cycle, E = (-0.3) - (+0.6) V vs. SSCE, v = 100 mV / s); Figure 1 b) shows the logarithm of the (frequency-dependent) capacitance value (Y” / ω) calculated from the impedance spectrum (E = 0.1V vs. SSCE) as a function of the logarithm of the frequency. Measurements were taken in a 0.1M Na2SO4 electrolyte solution, (1) representing the deposition on gold (A = 0.196 cm⁻¹). 2 (1) A PEDOT film prepared on a substrate according to Example 3, and (2) represents a PEDOT / iron oxide / hydroxide layer.

[0055] Figure 2 a) and b) show SEM (scanning electron microscope) images of the PEDOT / iron oxide / hydroxide composite layer deposited on a gold substrate according to Example 1 (Table 1#1), where a) is secondary electrons and b) is backscattered electrons. The scale at the bottom of the images corresponds to 50 μm. Figure 2 c) shows the EDX spectrum demonstrating the atomic composition of the sample, and also shows the peak corresponding to iron.

[0056] Figure 3 The study showed that the PBPA-reinforced PEDOT layer exhibited increased resistance to peroxidation compared to the untreated bisphenol A PEDOT film. According to Example 7, PEDOT ( Figure 3 a)) and PEDOT / PBPA ( Figure 3 b)) Samples were deposited on a gold substrate. The photograph of the strongly peroxidized layer shows the good structural enhancement effect of PBPA. Example

[0057] All electrochemical measurements were performed at room temperature (22.0 ± 0.5) °C. Solutions were saturated with oxygen-free argon (Linde 5.0) before use, and an inert gas atmosphere was maintained during the experiments. Electrochemical measurements were performed using a Zahner IM6 electrochemical workstation controlled by Thales software. Scanning electron microscopy (SEM) images were obtained from Quanta. TM Images were captured using a 3D FEG high-resolution dual-beam scanning electron microscope (SEM / FIB). Secondary electrons and scattered electrons were detected during the scanning process.

[0058] Research on PEDOT layer

[0059] Electrochemical studies of PEDOT layers were conducted at a depth of 150 cm. 3 The experiment was conducted in a three-electrode cell with a volumetric electrode, the working electrode being deposited on a gold disk (A = 0.196 cm⁻¹). 2 The electrodes were coated with a PEDOT layer, with a sodium chloride saturated calomel electrode (SSCE) as the reference electrode and a ring-shaped platinum plate as the counter electrode. These electrodes were immersed in 0.1 mol / dm³ of mol / dm³ ... 3 In H₂SO₄ solution. The potential window used in the cyclic voltammetry studies was E = (-0.1) - (+0.8) V vs. SSCE, with scan rates of v = 100 mV / s and 50 mV / s. Electrochemical impedance spectroscopy (EIS) measurements were performed in the frequency range of 50 kHz to 96.1 mHz, with a perturbation signal amplitude of 5 mV and electrode potentials of E = (+0.4) V or (+0.2) V vs. SSCE.

[0060] I. Synthesis of composite materials containing a PEDOT layer

[0061] Example 1

[0062] (1) Electrochemical deposition of the PEDOT layer in a volume of 150 cm³ 3 The electrolysis was carried out in a three-electrode electrolytic cell under constant current conditions (j = 0.2 mA / cm). 2 (t = 3600 s), on a gold substrate (A = 0.196 cm⁻¹). 2Deposition was performed on the substrate. The monomer-containing solution consisted of 0.01M EDOT / 0.1M Na2SO4 (pH=6). The counter electrode was a ring-shaped platinum plate. A potassium chloride saturated calomel electrode (SCE) was used as the reference electrode.

[0063] (2) The deposited PEDOT layer was reduced in 0.1M Na2SO4 (pH=5) solution (E=0.3V, t=120s). A sodium chloride saturated calomel electrode (SSCE) was used as a reference electrode.

[0064] (3) Immerse the reduced PEDOT layer in 0.05M Na2FeO4 / NaOH solution (t=30s; pH=14-10*).

[0065] (4) Repeat steps (2) and (3) 10 times consecutively.

[0066] *: The pH value decreases continuously during this process.

[0067] The following embodiments are basically carried out as described in Embodiment 1; therefore, only the main features of the method are given.

[0068] Example 2:

[0069] (1) Under constant current conditions (j=0.2mA / cm) 2 (t=3600s), using 0.01M EDOT / 0.1M Na2SO4 as electrolyte (counter electrode: Pt, reference electrode: SCE), a PEDOT layer was electrochemically deposited on a gold substrate.

[0070] (2) The deposited PEDOT layer was reduced in 0.1M Na2SO4 (pH=5) solution (E=-0.3-(+1.1)Vvs.SSCE; v=50mV / s, 3 cycles). Under the applied positive potential limit, the polymer was irreversibly oxidized (peroxidized), thus the structure became more porous, which promoted the entry of ions into the polymer membrane.

[0071] (3) Reduce the deposited PEDOT layer in 0.1M Na2SO4 (pH=5) solution (E=-0.3V vs. SSCE; t=120s).

[0072] (4) Immerse the reduced PEDOT layer in 0.05M Na2FeO4 / NaOH solution (pH=14-10*, t=30s).

[0073] (5) Repeat steps (3) and (4) 10 times consecutively.

[0074] *: The pH value decreases continuously during this process.

[0075] Example 3:

[0076] (1) Under constant current conditions (j=0.2mA / cm) 2 (t=3600s), using 0.01M EDOT / 0.1M Na2SO4 as electrolyte (counter electrode: Pt, reference electrode: SCE), a PEDOT layer was electrochemically deposited on a gold substrate.

[0077] (2) Reduce the deposited PEDOT layer in 0.1M Na2SO4 (pH=5) solution (E=-0.3V vs. SSCE; t=300s).

[0078] (3) The reduced PEDOT layer was immersed in 0.05M Na2FeO4 / NaOH solution (pH=14-10*, t=300s).

[0079] *: The pH value decreases continuously during this process.

[0080] Example 4:

[0081] (1) Under constant current conditions (j=0.2mA / cm) 2 (t=3600s), using 0.01M EDOT / 0.1M Na2SO4 as electrolyte (counter electrode: Pt, reference electrode: SCE), a PEDOT layer was electrochemically deposited on a gold substrate.

[0082] (2) The deposited PEDOT layer was reduced in 0.05M Na2FeO4 / NaOH (pH=14*) solution (E=-0.56Vvs.SSCE; t=300s).

[0083] The reduced PEDOT layer is immersed in the solution of step (2) (t = 300 s).

[0084] *: The pH value decreases continuously during this process.

[0085] Example 5:

[0086] (1) Under constant current conditions (j=0.2mA / cm) 2 (t=1000s), using 0.01M EDOT / 0.1M Na2SO4 as electrolyte (counter electrode: Pt, reference electrode: SCE), a PEDOT layer was electrochemically deposited on a gold substrate.

[0087] (2) The deposited PEDOT layer was reduced in 0.1M Na2SO4 (pH=5) solution (E=-0.3V vs. SSCE; t=120s).

[0088] (3) The reduced PEDOT layer was immersed in 0.05M Na2FeO4 / NaOH solution (pH=14-10*, t=30s).

[0089] (4) Repeat steps (2) and (3) 10 times consecutively.

[0090] *: The pH value decreases continuously during this process.

[0091] Example 6:

[0092] (1) Electrochemical deposition of the PEDOT layer in a volume of 150 cm³ 3 The electrolysis was carried out in a three-electrode electrolytic cell under constant current conditions (j = 0.2 mA / cm). 2 (t = 3600 s), on a gold substrate (A = 0.196 cm⁻¹). 2 Deposition was performed on the substrate. The monomer-containing solution consisted of 0.01M EDOT / 0.1M Na2SO4 (pH=5). The counter electrode was a ring-shaped platinum plate. A potassium chloride saturated calomel electrode (SCE) was used as the reference electrode.

[0093] (2) The deposited PEDOT layer was reduced in 0.1M Na2SO4 (pH=5) solution (E=0.3V, t=120s). A sodium chloride saturated calomel electrode (SSCE) was used as a reference electrode.

[0094] (3) The reduced PEDOT layer was immersed in 0.05M Fe2FeO4 / KOH solution (t=30s; pH=14-10*).

[0095] (4) Repeat steps (2) and (3) 10 times consecutively.

[0096] *: The pH value decreases continuously during this process.

[0097] Example 7:

[0098] (1) Under constant current conditions (j=0.2mA / cm) 2 PEDOT films were electrochemically deposited on a gold substrate using 0.01M EDOT / 0.1M Na2SO4 as electrolyte (pH=5, counter electrode: Pt, reference electrode: SCE). (t=3600s)

[0099] (2) Reduce the deposited PEDOT layer in 0.1M Na2SO4 (pH=5) solution (E=-0.3V vs. SSCE; t=300s).

[0100] (3) The reduced polymer layer was immersed in 0.05M Na2FeO4 / NaOH solution and subjected to cyclic potentiodynamic polarization: 21 cycles (pH = 14-10*, E = (-0.4)-(+0.3V) vs. SCE; v = 100mV / s).

[0101] *: The pH value decreases continuously during this process.

[0102] Example 8:

[0103] (1) Under constant current conditions (j=0.2mA / cm) 2 (t=3600s), using 0.01M EDOT / 0.1M Na2SO4 as electrolyte (counter electrode: Pt, reference electrode: SCE), a PEDOT layer was electrochemically deposited on a gold substrate.

[0104] (2) The PEDOT layer was immersed in 0.05M K2FeO4 / KOH solution and subjected to cyclic potentiodynamic polarization: 21 cycles (pH=14-10*, E=(-0.4)-(+0.3)V vs. SCE; v=100mV / s)

[0105] *: The pH value decreases continuously during this process.

[0106] Table 1 summarizes various PEDOT / Fe... x O y Production parameters of composite materials and their iron content expressed as atomic percentage (atomic %).

[0107] Table 1: Production parameters (t) of PEDOT / iron oxide / hydroxide composite material deposited on gold substrate dep : Deposition time of PEDOT layer; Overox: Occurrence of PEDOT layer peroxidation; t red : Restore time, E red Reduction potential, pH compared to SSCE electrode red pH and t of the reducing medium imm Impregnation time, atomic percent (Fe): data obtained from EDX measurements.

[0108]

[0109] * Potential kinetics: 21 cycles, E = (-0.4) - (+0.3V) vs. SCE; v = 100mV / s

[0110] Discussed in more detail here Figure 1 Content:a) Cyclic voltammograms (curves recorded in the third cycle, E = (-0.3) - (+0.6) V vs. SSCE, v = 100 mV / s) and b) deposited on a gold substrate (A = 0.196 cm⁻¹) according to Example 3. 2 The logarithm of the frequency-dependent capacitance (Y” / ω) of the PEDOT film (1) on the substrate and the PEDOT / iron oxide / hydroxide layer (2) in 0.1M Na2SO4 electrolyte is compared with the logarithm of the frequency (as a function of the logarithm of the perturbation signal frequency) calculated from the impedance spectrum (E=0.1V vs. SSCE). The study of the electrochemical properties of the composite material shows that the iron-containing composite material also retains the capacitive properties of the original film containing only the conductive polymer. Figure 1 a). Compared to pure PEDOT layers without iron oxide / hydroxide, the composite layer shows a moderate increase in low-frequency capacitance, while exhibiting a clear increase in capacitance in the mid-frequency range. Figure 1 (b)). In practice, this increase in capacity means that the iron content of the polymer layer is electrochemically active, i.e., the oxidation state can be tuned by changing the potential. Furthermore, the capacity of the modified polymer film is linear over a wider range, which is a highly advantageous characteristic for its use as a supercapacitor.

[0111] Discussed in more detail here Figure 2 Content The PEDOT / iron oxide / hydroxide composite layer deposited on a gold substrate according to Example 1 (Table 1#1) is shown in the following images: a) SEM image recorded with secondary electrons, b) backscattered electron image, and c) EDX spectrum showing the atomic composition of the sample, where peaks corresponding to iron can be seen. The scale at the bottom of the figure corresponds to 50 μm. The electron microscopy images confirm that the PEDOT / iron oxide / hydroxide composite film also exhibits the cauliflower-like structure characteristic of PEDOT. In the backscattered electron image, the composite material (dark details) is well distinguishable from the gold substrate (light details). Based on these, severe cracking rather than uniformity can be observed in the layer, which may be due to the effects of the steps used in the synthesis of the composite material (peroxidation).

[0112] The presence of iron oxides in the layer can also be detected by Mössbauer spectroscopy ( Spectrosopy (SMP) assay. Due to the very small size of the iron-containing crystals, the composition cannot be determined.

[0113] II. Production of Conductive Polymer Layers Reinforced with PBPA Layers

[0114] Example 9

[0115] Preparation of poly(bisphenol A) [PBPA] reinforced PEDOT membrane

[0116] Step 1: Deposition of poly(3,4-ethylenedioxythiophene) layer

[0117] Electrochemical deposition of the PEDOT layer in a volume of 150 cm⁻¹ 3 The electrolysis was carried out in a three-electrode cell, where the working electrode was a gold disk (A = 0.196 cm⁻¹). 2 The reference electrode was a potassium chloride saturated calomel electrode (SCE), and the counter electrode was a toroidal platinum disk. These electrodes were immersed in a pre-prepared 0.01 mol / dm³ solution. 3 EDOT / 0.1mol / dm 3 In a Na₂SO₄ solution (pH = 5), during constant current deposition, a current of j = 0.2 mA / cm² was applied. 2 The current density. The deposition time is t = 1800 s.

[0118] The prepared polymer layer was immersed in Milli-Q water for one day to relax (thus ensuring the removal of oligomers).

[0119] Step 2: Deposition of the poly(bisphenol A) [PBPA] layer

[0120] Electrochemical deposition of the PBPA layer on the PEDOT layer was performed using a potentiodynamic method at a depth of 30 cm. 3 The electrolysis was carried out in a three-electrode electrolytic cell, wherein the working electrode was deposited on a gold plate (A = 0.196 cm⁻¹). 2 The PEDOT layer on the surface was impregnated with 100ppm BPA / 0.5mol / dm³. 3 The electrode was prepared in H2SO4 (pH = 0.6) solution; the reference electrode was a saturated sodium chloride-filled calomel electrode (SSCE); and the counter electrode was a platinum wire. During potentiodynamic deposition, the potential window was E = -0.1 - (+1.0) V vs. SSCE, the scan rate was v = 100 mV / s, and the number of cycles was 10.

[0121] Step 3: Study of the PEDOT / PBPA layer

[0122] Electrochemical deposition of the PEDOT layer in a volume of 150 cm⁻¹ 3 The electrolysis was carried out in a three-electrode cell, where the working electrode was a gold disk (A = 0.196 cm⁻¹). 2 The reference electrode was a potassium chloride-saturated calomel electrode (SCE), and the counter electrode was a ring-shaped platinum plate. These electrodes were immersed in a pre-prepared 0.1 mol / dm³ solution. 3 EDOT / 0.1mol / dm 3The samples were prepared in Na₂SO₄ solution (pH = 1.3). The potential window during cyclic voltammetry studies was E = (-0.1) - (+0.8) V vs. SSCE, with scan rates of v = 100 mV / s and 50 mV / s. Electrochemical impedance spectroscopy (EIS) measurements were performed in the frequency range of 50 kHz–96.1 mHz, with a perturbation signal amplitude of 5 mV and electrode potentials of E = 0.4 V or 0.2 V vs. SSCE.

[0123] Step 4: Peroxidation of the PEDOT / PBPA layer

[0124] The peroxidation of the PEDOT layer prepared in step 2 was carried out in a volume of 150 cm³. 3 The electrolysis was carried out in a three-electrode cell, with the working electrode deposited on a gold disk (A = 0.196 cm⁻¹). 2 A PBPA-reinforced PEDOT layer was applied to the electrode, with a sodium chloride-saturated calomel electrode (SSCE) as the reference electrode and a ring-shaped platinum plate as the counter electrode. These electrodes were immersed in 0.1 mol / dm³ of mol / dm³ ... 3 In H2SO4 solution. During the peroxidation process, the potential window is E = 0.4-1.5V vs. SSCE, the scan rate is v = 50mV / s, and the number of cycles is 3.

[0125] Step 5: Study of the PEDOT peroxide layer

[0126] Electrochemical studies of the PEDOT peroxide layer prepared in step 4 were conducted in a volume of 150 cm³. 3 The electrolysis was carried out in a three-electrode cell, wherein the working electrode was deposited on a gold disk (A = 0.196 cm⁻¹). 2 A PBPA-reinforced PEDOT layer was applied to the electrode, with a sodium chloride-saturated calomel electrode (SSCE) as the reference electrode and a ring-shaped platinum plate as the counter electrode. These electrodes were immersed in 0.1 mol / dm³ of mol / dm³ ... 3 In H₂SO₄ solution. The potential window during cyclic voltammetry studies was E = (-0.1) - (+0.8) V vs. SSCE, with scan rates of v = 100 mV / s and 50 mV / s. Electrochemical impedance spectroscopy (EIS) measurements were performed in the frequency range of 50 kHz–96.1 mHz, with a perturbation signal amplitude of 5 mV and electrode potentials of E = 0.4 V or 0.2 V vs. SSCE.

[0127] A more detailed discussion Figure 3 Content: Studies have shown that PBPA-supported / reinforced PEDOT layers are more resistant to peroxidation than pure PEDOT films. Compared to PEDOT films ( Figure 3 a) Different, PEDOT / PBPA layer ( Figure 3 b) It will not peel off from the substrate due to peroxidation.

[0128] Example 10:

[0129] Deposition of bisphenol A layer after ferrate treatment

[0130] (1) Under constant current conditions (j=0.2mA / cm) 2 (t=3600s), using 0.01M EDOT / 0.1M Na2SO4 as electrolyte (pH=5, counter electrode: Pt, reference electrode: SCE), a PEDOT layer was electrochemically deposited on a gold substrate.

[0131] (2) The PEDOT layer was immersed in 0.05M K2FeO4 / KOH solution for potentiodynamic cyclization: 21 cycles, (pH=14-10*, E=-0.4-(+0.3)V vs. SCE; v=100mV / s.)

[0132] *: The pH value decreases continuously during this process.

[0133] (3) Deposit poly(bisphenol A) layer from 100ppm BPA / 0.1M Na2SO4 (pH=5) electrolyte solution using potentiodynamic method (10 cycles, E=-0.2-(+0.8)V vs. SSCE; v=100mV / s).

[0134] The Fe content of the formed material is 13.3% (atomic %).

[0135] Example 11:

[0136] Deposition of bisphenol A layer before ferrate treatment

[0137] (1) Under constant current conditions (j=0.2mA / cm) 2 (t=3600s), using 0.01M EDOT / 0.1M Na2SO4 as electrolyte (counter electrode: Pt, reference electrode: SCE), a PEDOT layer was electrochemically deposited on a gold substrate.

[0138] (2) Deposition of a poly(bisphenol A) layer from a 100ppm BPA / 0.5M H2SO4 (pH=0.6) electrolyte solution using potentiodynamic methods (10 cycles, E=-0.1-(+1.0)V vs. SSCE; v=100mV / s).

[0139] (3) The deposited PEDOT / PBPA layer was reduced in 0.1M Na2SO4 (pH=5) solution (E=-0.3V, t=120s). A sodium chloride saturated calomel electrode (SSCE) was used as a reference electrode.

[0140] (4) The reduced PEDOT layer was immersed in 0.05M K2FeO4 / KOH solution (t=30s; pH=14-10*).

[0141] (5) Repeat steps (2) and (3) 10 times.

[0142] *: The pH value decreases continuously during this process.

[0143] Fe content of the material: 0.5 atomic%.

[0144] III. Synthesis of composite materials containing PANI film

[0145] In the case of certain polymers (such as polyaniline), constant current polymerization is not used (as in the synthesis of PEDOT films), and potentiodynamic deposition is recommended instead because constant current deposition is less efficient. The other preparation steps are the same as those discussed for PEDOT.

[0146] Example 12:

[0147] (1) PANI film was electrochemically deposited on a gold substrate using potentiodynamic method (E = 0.2-0.8V, v = 100mV / s, 40 cycles) with 0.2M aniline / 0.5M H2SO4 as electrolyte (counter electrode: Pt, reference electrode: SCE).

[0148] (2) Reduce the deposited PANI layer in 0.1M Na2SO4 (pH=5) solution (E=-1.3V vs. SSCE; t=300s).

[0149] (3) The reduced PEDOT layer was immersed in 0.05M Na2FeO4 / NaOH solution (pH=14-10*, t=300s).

[0150] *: The pH value decreases continuously during this process.

[0151] When the initial bright green polymer layer turns purplish-blue after treatment, iron incorporation into the polymer film can be observed.

Claims

1. A method for electrochemically producing conductive polymer composites containing iron oxides / hydroxides by one of the following methods: Method I, which includes the following steps: a) Provide a conductive polymer layer, optionally subjecting the conductive polymer layer to partial irreversible electrochemical oxidation or peroxidation; b) Electrochemically reduce the conductive polymer layer, optionally in a solution containing ferrate ions; c) Contact the reduced conductive polymer layer with an aqueous solution of ferrate ions; d) Optionally repeat steps b) and c). e) Optionally, the composite material is separated from the electrode used in the electrochemical reaction, and if necessary, the composite material is dried; or Method II includes the following steps: a) Provide a conductive polymer layer, optionally electrochemically reducing the conductive polymer layer; b) Contact the conductive polymer layer with an aqueous solution of ferrate ions; c) Electrochemical oxidation of the conductive polymer layer in ferrate ion aqueous solution; d) Electrochemical reduction of the oxidized conductive polymer layer in an aqueous solution of ferrate ions; e) Optionally repeat steps c) and d). f) Optionally, the composite material is separated from the electrode used in the electrochemical reaction, and if necessary, the composite material is dried.

2. The method according to claim 1, wherein in steps I a) and II a), the conductive polymer layer is generated electrochemically, wherein the conductive polymer layer is deposited on the substrate by a constant current or potentiodynamic method.

3. The method according to claim 2, wherein the substrate is selected from: gold, platinum, graphite, glassy carbon, conductive carbon layer and carbon fiber.

4. The method of claim 3, wherein the substrate is selected from gold.

5. The method of claim 1, wherein steps I b) and I c) or II c) and II d) are repeated 5 to 20 times in step I d) or II e).

6. The method of claim 5, wherein steps I b) and I c) or II c) and II d) are repeated 8 to 12 times in step I d) or II e).

7. The method according to any one of claims 1 to 6, wherein the reduction according to step I b) is carried out in a solution containing ferrate ions, and the contact according to step I c) is carried out in a manner that allows the conductive polymer layer to stand in the ferrate solution of step I b), and optionally additional ferrate is added to the solution.

8. The method according to claim 7, wherein the ferrate is sodium ferrate or potassium ferrate.

9. The method according to any one of claims 1 to 6, wherein in step II e), steps c) and d) are repeated by cyclic voltammetry.

10. A conductive polymer composite material containing iron oxide / hydroxide, obtained by the method according to any one of claims 1 to 9.

11. The conductive polymer composite material containing iron oxide / hydroxide according to claim 10, wherein the conductive polymer is reinforced with a polymer deposited thereon.

12. The conductive polymer composite material containing iron oxide / hydroxide according to claim 11, wherein the deposited polymer is poly(bisphenol A).

13. A conductive polymer composite material containing iron oxide / hydroxide produced by the method according to any one of claims 1 to 9, comprising: a) Conductive polymers, and b) Iron oxides / hydroxides incorporated into the conductive polymer The iron oxide / hydroxide compound mentioned therein is not magnetite, and The conductive polymer described therein is different from polyaniline, and The conductive polymer is reinforced by a polymer deposited thereon.

14. The conductive polymer composite containing iron oxide / hydroxide according to claim 13, wherein the polymer deposited on the conductive polymer is electrodeposited poly(bisphenol A).

15. The conductive polymer composite material containing iron oxide / hydroxide according to claim 13 or 14, wherein the conductive polymer is selected from poly(3,4-ethylenedioxythiophene) and poly(o-phenylenediamine).

16. The conductive polymer composite material containing iron oxide / hydroxide according to claim 15, wherein the conductive polymer is selected from poly(3,4-ethylenedioxythiophene).

17. The conductive polymer composite material containing iron oxide / hydroxide according to claim 13 or 14, wherein the iron oxide / hydroxide compound is selected from: Fe2O3, Fe(OH)2, Fe(OH)3 and FeO(OH).

18. The conductive polymer composite material containing iron oxide / hydroxide according to claim 13 or 14, wherein, Based on the total mass of the iron oxide / hydroxide compound, the content of the iron oxide / hydroxide compound other than magnetite in the composite material is at least 1 to 25 wt%.

19. The conductive polymer composite material containing iron oxide / hydroxide according to claim 18, wherein, Based on the total mass of the iron oxide / hydroxide compound, the content of the iron oxide / hydroxide compound in the composite material, excluding magnetite, is 2 to 10 wt%.

Images