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Article

Transforming Chimney Soot via Stochastic Polymerization for Active Electrode Coating

by
Miroslav Petrov
1,*,
Lyubomir Slavov
1,
Toma Stankulov
2,
Boryana Karamanova
2,
Teodor Milenov
1,
Dimitar Dimov
1 and
Ivalina Avramova
3
1
Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Shaussee, 1784 Sofia, Bulgaria
2
Institute of Electrochemistry and Energy Systems, Bulgarian Academy of Sciences, Academician Georgi Bonchev Street, 1113 Sofia, Bulgaria
3
Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Academician Georgi Bonchev Street, 1113 Sofia, Bulgaria
*
Author to whom correspondence should be addressed.
Coatings 2023, 13(8), 1354; https://doi.org/10.3390/coatings13081354
Submission received: 25 June 2023 / Revised: 25 July 2023 / Accepted: 28 July 2023 / Published: 2 August 2023
(This article belongs to the Special Issue Electrochemical Deposition: Properties and Applications)
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Abstract

:
A polymerization procedure is presented to increase the molecular weight of hydrocarbons in household chimney soot without thermal treatment at high temperatures. Pristine soot was subject to chlorination, with half of it treated with magnesium (Mg-plates) to create random-type Grignard reagents (R-Mg-Cl) in diethyl ether media. Mixing the Grignard reagent and the rest of the halogenated soot material created new C-C bonds, thus increasing the molecular weight of the final product. The obtained stochastically polymerized soot (SPS) was investigated using Raman spectroscopy, FTIR spectroscopy and XPS and was subjected to electrochemical testing as an assembled supercapacitor with a KOH electrolyte. Results show significant carbon structure differences due to the chemical procedures and newly created functional groups in the soot. Such functional groups could increase the capacity of supercapacitors, creating pseudo-capacitance by participating in redox reactions. The results also unveiled removing any random contaminations in the pristine soot and obtaining a more uniform final product containing hydrocarbons with longer chains, thus increasing the molecular weight.

1. Introduction

The exceptional importance of the combustion of carbon-containing compounds as a source of thermal energy throughout human history and its related progress cannot be denied [1]. However, this process, essentially a reaction leading to numerous uncontrolled chemical changes in the starting hydrocarbons, is also associated with the production of harmful emissions into the atmosphere, including soot aerosols [1,2,3].
The incomplete combustion of hydrocarbons associated with both anthropogenic (various combustion systems for energy and heat production, transport, etc.) and natural sources (forest fires) is responsible for the formation and emission of more than 8 Tg of soot annually into the atmosphere [2,3,4,5,6,7]. With a more than 80% contribution, elemental carbon is the main constituent of soot particles regardless of the source [8,9,10]. The processes of the formation of soot, which passes roughly through four stages, i.e., from precursor formation to aggregate formation, have been the subject of many notable studies, summarized in a recent review article by Martin J. et al. [9]. The final product in the form of carbonaceous particulate matter, both as aerosols and as solid deposits (in diesel and gasoline particle filters, onto chimneys’ internal walls, etc.), leads to serious health and environmental risks for the population [7,9,11]. The industry has made enormous efforts to reduce the soot particles released into the atmosphere. But industrial advances can also lead to additional increases in the amount of solid deposits of soot and the generation of unnecessary waste products. At the same time, they could lead to obtaining even more soot as solid deposits, which indeed results in a huge amount of unnecessary cheap waste product. For instance, in the context of engine-generated soot emissions, besides advances in particle filters [12] and modifications in the combustion process like the use of EGR (exhaust gas recirculation), attempts were made to lower the temperature of the exhaust gases [13,14]. However, the EGR leads to higher quantities of soot in the crankcase oil [13], and lowering the temperatures leads to an increased rate of soot deposition [14]. To these amounts of soot as waste material must be added those obtained during the incomplete combustion of hydrocarbons in households. The study of the physicochemical properties of soot and the produced materials from them is of great importance for establishing their true value for practical applications, since a key point in the conceptual model of a circular economy is the successful application of waste materials as useful ones [3,5,10,15].
Although soot (as carbon black) has been widely used as a component in inks since ancient times [16], a recent review focused on the currently known applications of recycled soot [17] suggests the enormous, still-untapped potential of this abundant waste material. To the soot applications discussed by Uttaravalli et al. [17], some other studies on soot as a material for anti-bio-adhesion behavior coatings [18], as super hydrophobic coatings [19], and also some experimental attempts for soot to be used as supercapacitor electrodes [10,20,21] should be added. Functionalized candle soot is used to improve Raman sensing properties for active SERS (surface-enhanced Raman scattering) substrates [22].
On the other hand, to achieve specific physical properties and specialized applications for advanced structures and architectures, one could rely on the constant progress in polymer science [23,24,25]. Extensive research in the field of carbocationic and free radical polymerization (FRP) led to the synthesis of new well-defined (co)polymers, with FRP already being probably the most important commercial process, which allows one to obtain high molar mass polymers [23,24,25,26,27]. The discovery of Grignard agents could also be considered one important stage of development in polymer science. The ease of preparation of these organo-magnesium reagents, discovered at the beginning of the last century by Victor Grignard, ensures their large-scale success and ensures their wide application in organic and organometallic synthesis [28]. The reaction to obtain Grignard reagents (R-Mg-X) in various solvents is generally described as R-X + Mg, where R is a carbon-containing radical and X is a halogen element [28,29]. These reagents react with numerous organic functional groups containing polar multiple bonds (ketones, nitriles, sulfones, etc.), highly strained carbon rings, acidic hydrogens, etc. [29].
In the present study, a polymerization procedure was applied to alter the properties of what would otherwise be waste products (household chimney soot) in a way in which they could be further used as material for supercapacitance applications. Since the supercapacitors are a unique class of energy-storage devices that are mainly produced from carbon-based materials [30,31,32], attempts at this scientific direction should be regarded as needed steps toward the realization of a true circular economy [15]. Probably equally common and harmful as all other types of soot, also easily accessible and costless, but at the same time structurally different because of the specific burning conditions, household chimney soot lags far behind in terms of scientific research compared with all other types of carbonaceous materials.
Stochastic polymerization appears when complicate materials are involved in polymerization processes and different exchanging segments and molecules are interacting [33]. Here, stochastic free radical synthesis, involving a combination of newly created Grignard reagent and chlorinated soot, leads to the creation of new higher molecular compounds in pristine soot.
The novel chemical routine is described in detail. Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis were applied as techniques to characterize the obtained stochastically polymerized soot (SPS). The material was applied as an active electrode coating and was subjected to electrochemical testing with KOH as an electrolyte.

2. Materials and Methods

2.1. Experimental Section

Swept household chimney soot was used in the experimental procedure, shown as block scheme no. Figure 1 and described in detail below. Procedure must be performed carefully because of the starting exothermic reaction and the occurrence of immense amount of fine, thick foam. To avoid evaporation of chlorinated hydrocarbons, the mixture thus obtained was dried in a desiccator containing crystal CaCl2 and KOH for a month at RT.
After such a prolonged period, it was expected that all the moisture, CO2, and surplus HCl reacted with the CaCl2 and KOH crystallites.
The experimental procedures on the chlorinated soot (ChS) material continued in a 3-neck 200 mL flask, used as a reactor to obtain Grignard reagent (R-Mg-Cl). One of the three necks of the reactor was for inserting a glass rod used as a stirrer, the second one was used as a breather (filled with crystal CaCl2 between cotton tampons) and the central neck was used for filing the flask. The flask was rinsed with diethyl ether ((C2H5)2O) or Et2O) prior to experiment and placed in an ice water bath at 0 °C. Every glass piece of the equipment was heated for 2 h at 110 °C prior to experiment. Two 15 mL vessels filled with powdered ChS in each, 100 mL Et2O and 1 g Mg (fine plates) were placed in a Glove Bag filled with inert gas (Ar). The ChS from one of the vessels was placed in the flask, followed by the 100 mL Et2O and the Mg plates. The filling neck of the flask was capped and the Glove Bag was removed. This was followed by vigorous stirring of the solution, aiming at the maximum dissolution of the magnesium plates. A brief heating of the mixture to ~30 °C resulted in slight boiling (due to the low boiling point of the ether in the solution), then the mixture was quenched in the ice bath. After 12 h, needed for optimal reaction result, the Glove Bag again covered the installation and purged with Ar. A brief heating (to ~30 °C) was applied to increase the partial pressure in the volume, preventing of inlet of external gases. A separation funnel with a long glass tube at the bottom end and a syringe at the top end was used to evict the obtained Grignard reagent upwards via the creation of a vacuum. The unreacted Mg plates and sediment that remained at the bottom were removed through the breather neck of the flask, and the flask was rinsed again with ether. The second vessel with powdered chlorinated soot was then placed in the flask, and 20 mL of ether and the Grignard reagent were also added. After 24 h, the liquid phase was removed from the obtained mixture using a pipette, and the precipitated material was collected and dried at 30 °C for 1 h, resulting in the final experimental product: stochastically polymerized soot (SPS).

2.2. Methods of Investigation

The Raman spectra were taken using HORIBA Jobin Yvon Labram HR 800 spectrometer equipped with a Peltier-cooled CCD detector with He-Ne laser excitation of 633 nm wavelength and laser power at 0.5 mW. The spectral resolution was 1 cm−1 or better. The materials were also investigated using Fourier-transform infrared spectroscopy (FTIR) spectroscopy on Tenzor 27-Bruker apparatus in the range of 4000–550 cm−1. The X-ray photoelectron spectroscopy (XPS) studies were performed in a VG Escalab MKII electron spectrometer using monochromatic AlKα radiation with an energy of 1486.6 eV under base pressure 10−8 Pa and a total instrumental resolution 1 eV. The binding energies (BEs) were determined utilizing the C 1s line as a reference with an energy of 285.0 eV. The accuracy of the measured BE was 0.2 eV. The photoelectron lines of constituent elements on the surface were recorded and corrected by subtracting a Shirley-type background and quantified using the peak area and Scofield’s photoionization cross-sections. The deconvolution of spectra was performed with XPSPEAK41 software (version 4.1). The conditions used for electrochemical testing are presented in Section 3.4.

3. Results and Discussion

3.1. Raman Spectroscopy Investigation

Raman spectroscopy investigation was performed on the pristine soot sample and the SPS sample to unveil how the chemical treatment influences the pristine carbon structure in the soot (Figure 2).
Since carbon is the main constituent in the material, it is not surprising that Raman spectroscopy is a widely used method for the characterization of any type of soot [3,5,6,8,12,13,34,35,36,37,38,39,40,41,42].
In the first-order spectral region (1000–2000 cm−1), both spectra in Figure 2 exhibited the two typical-for-all-carbon-species broad bands, centered at 1364 cm−1 and 1583 cm−1, corresponding to the D- and G-band, respectively. A detailed description of the significance of these two peaks for the state of the carbon structure can be found in the seminal work of Ferrari and Robertson [43].
While the D peak was related to defects in the ordered graphite structure (crystalline defects, vacancies, etc.), the G peak was regarded as an expression of that same ordered graphitic structure [40]. Regarding soot samples, the G peak signaled some local order associated with the presence of sp2 aromatic carbon rings in the predominantly disordered structure [12,36]. In the spectral region of 2100–2800 cm−1, the pristine soot spectra exhibited a wide “bump” which comprised all overtone modes associated with the first-order carbon peaks (D and G).
But, these second-order peaks are rarely reported in the literature when regarding soot samples [44], so a contribution from some organic carbon (OC) or hydrocarbons could be regarded in that region. The spectrum of the SPS sample flattened in that region. A second major difference between the two spectra is the change in places in terms of the intensity of the G- and D-bands: in the SPS sample, the D-band increased in intensity, while the G-band decreased compared with the pristine soot spectrum. The drastic decrease in background fluorescence in the final product spectrum, compared with the pristine soot spectrum (Figure 2), should also be noted. The steep slope of the experimental curve until reaching the first peak at 1356 cm−1 (line “a” in Figure 2) is a typical indicator for the presence of an interfering fluorescence signal (FS), alongside the very shallow plateau between the D- and the G- band. The FS in a soot spectrum is due to organic compounds like PAHs (polyaromatic hydrocarbons) and unsaturated hydrocarbons condensed onto the particles, which are normally produced during combustion [5,37,40,44]. Thus, when comparing the two spectra, it could be said that the decrease in the intensity of the fluorescent signal, along with the complete alignment of the SPS spectrum in the region 2100–2800 cm−1, indicates the removal of any organic compounds and the achievement of a more uniform final product (SPS).
In order to further analyze the changes that took place during the pristine soots’ chemical treatment, a four-band fit was applied and is presented in Figure 3. Sadezky et al. were the first to establish a Raman deconvolution routine for carbonaceous materials, including soot, with a five-band fit involving four Lorentz-shaped curves (labeled as G, D1, D2 and D4) and one Gaussian-shaped curve (D3) [8]. Since then, the D2 curve has rarely been used when fitting soot samples [12,38]. The additional curves used for the spectrum analysis here, besides the G and D1 band, which match the D-band position and meaning, were the less-intense D3 and D4 bands. The D3 band, lying close to 1500 cm−1, is associated with the presence of amorphous carbon [8,12,13]. This carbon fraction in the soot comes from organic molecules, functional groups, fragments, etc. [8,12,13]. The D4 band, lying close to 1180 cm−1, is associated (when in soot) with ionic impurities and/or polyenes [8,13,42]. The decrease in intensity of the G-band in SPS compared with the pristine soot means raised disorder in the graphitic structure, which could be connected with the functionalization procedures conducted. The sp2 carbon atoms from the aromatic rings available in the pristine sample, most probably by adding chlorine atoms, changed their hybridization into sp3 and, thus, the G-band shrunk in intensity. Therefore, it can be concluded that the newly created functional groups in the soot do exist in the final product (SPS), which is of big importance for supercapacitance applications. In addition, there is also a significant increase in the contribution of both the amorphous carbon phase (D3 band) and that of ionic impurities (D4 band) in the SPS spectrum compared with that of the pristine soot sample (Figure 3). To obtain more information about the origin of these two additional phases’ increases, a further FTIR investigation was conducted. Nevertheless, the soot polymerization procedures involved have a major impact on altering the arbon phase composition of the original waste material.

3.2. FTIR Spectroscopy Investigation

FTIR spectra recorded on the pristine soot and the stochastically polymerized soot (SPS) materials are shown in Figure 4.
A significant change in the spectrum of the pristine soot’s chemical composition is evident in Figure 4. Taking into consideration that any given absorption band intensity assigned to a functional group increases/decreases proportionately with the number of times that a functional group occurs within the molecule [45], the presented data confirm the results from the Raman spectroscopy.
Starting with the higher wavenumbers, it can be seen that the intensity of the peak around 3500 cm−1 (stretching vibrations, OH-groups) was significantly lower in the SPS sample’s spectrum, compared with the pristine one (Figure 4). This means that OH groups were highly affected due to the chlorination process and the Grignard synthesis. In the spectral range 2960–2850 cm−1, where the stretching vibrations of C-H alkane bonds are situated [46], a significant lowering of the intensity in the SPS spectrum was observed. This was mainly due to the chlorination process, where the chlorine atoms displaced the hydrogen atoms from the C-H bonds. The overall intensity decrease in the peaks in the SPS spectrum was, in general, until 1300 cm−1, where the OH bending vibrations of phenol are situated (Figure 4). The peak at 1704 cm−1, assigned to C=O-conjugated aldehyde or acid [46], decreased in intensity in the SPS spectrum, but was still significant in appearance. Under UV light, PAH and aromatic species with carbonyl and carboxyl groups generated excited species, which then underwent further reaction [7]. At the lower wavenumbers, the absorbance in the SPS spectrum, compared with the pristine soot spectrum, increased where the C-O, C-C and C=C bending vibrations of alkyl aryl ether, esters and alkenes appeared [45]. This means that new bonds were created, thus increasing the molecular weight of the soot in the SPS sample. A strong intensity peak emerged in the SPS spectrum at 1066 cm−1 related to C-O stretching vibrations [47] (Figure 4). The reason for its appearance may be due to the addition of H2O2 in the chlorination process. The hydrogen peroxide oxidized H2, but H2O2 also reacted with carbon atoms and also could form additional C-O and C=O bonds. The existing C-O and C=O were probably oxidized to CO2, which was the main phase of the emerging gases during chlorination.
Another peak also appeared at 796 cm−1 in the SPS spectrum, which, according to the Sigma Aldrich database table [46], is characteristic of C-H or C=C bending vibrations. In this case, the peak may be due to both types of characteristic bond vibrations. The overall increase in intensity below 1200 cm−1 in the SPS spectrum, compared with the pristine soot spectrum, most probably means that the final product has been subject to a reduction process. If a Grignard synthesis is performed with a significant amount of H2O traces present, the water molecules destroy the Grignard reagent, thus giving simple C-H bonds instead of C-C bonds. However, the observed C-H and C-C spectral features in the FTIR spectra of the SPS sample had higher intensities, which is evidence that the polymerization was performed correctly, and hydrocarbons with longer chains were created.

3.3. XPS Analysis

The chemical state of the soot, PS and SPS samples were studied using X-ray Photoelectron Spectroscopy (XPS), presented in Figure 5. In the survey scan, clearly distinguished difference between the three spectra was that Cl was not present in the soot and PS samples. In addition, Si and Mg appeared in the SPS, which was due to the traces of Mg that remained after the synthesis, and the only source of Si was the used laboratory glass. There was N2, of which occurrence is normal in the burning processes, but it disappeared in the final SPS sample.
The C 1s and Cl 2p deconvoluted photoelectron spectra of the pristine soot (PS) are shown in Figure 6.
The C 1s and Cl 2p peaks were deconvoluted to obtain information on the sp2 and sp3 carbon bonding fractions and oxygenated functional, as well as to evaluate the possible carbon-to-chlorine bonding. The C 1s peak for PS can be fitted well by three peaks: sp2-hybridized carbon at 284.6 eV, sp3-hybridized carbon at 285.2 eV and the C-OH group at 286.6 eV.
The C 1s for the SPS presented in Figure 7 was fitted by four components, respectively: sp2-hybridized carbon at 284.6 eV, sp3-hybridized carbon at 285.2 eV, the C-OH group at 286.6 eV and the C=O group at 288.8 eV. It is worth noting that K and Cl were present in small amounts in the PS sample; the K 2p and Cl 2p binding energies suggest that they were linked as KCl. The chemical routine caused some changes in the chemical composition and bonding in the SPS. The peak at 286.6 eV can be associated with the existence of C-Cl bonds [48,49,50], left from the ChS sample as well as C-OH groups, which were already present on the PS surface in a significant amount. The concentration of oxygen on the surface of the SPS was lowered by the same amount as the increased concentration of chlorine atoms.
The Cl 2p XPS spectra (a spin–orbit split into 2p 3/2 (200.7 eV) and 2p 1/2 (202.3 eV) peaks) for the SPS, shown in Figure 7b, is clear proof of the presence of chlorine atoms on the surface of the chlorinated sample. Additional conformation for that is the shift of Cl 2p binding energy from 199.3 eV to 200.7 eV, which is typical for organic compounds.
The atomic surface concentrations of the constituent elements in the PS and SPS were calculated and are given in Table 1 and Table 2, respectively.

3.4. Electrochemical Testing

The tested symmetrical cell contained two identical electrodes coated with 80% active material (SPS sample), graphite ABG 1005 EG-1 (10%) and binder PVDF (10%). Binder in powder form and 10 µL N-Methyl-2-pyrrolidone were added to the active SPS mass, and then the prepared paste was applied to a nickel foam current collector with a diameter of 9 mm. The electrodes were dried in a drying oven at 80 °C for 12 h and pressed under pressure (20 MPa).
The cyclic voltammetry measurements (CV) were carried out in a two-electrode cell in a voltage window from 0.05 V up to 1.2 V and different scan rates—from 1 mVs−1 up to 50 mVs−1. The CV experiments were carried out on Multi PalmSens model 4. All measurements were performed at RT. The electrochemical test results are shown in Figure 8.
The electrodes were soaked in the electrolyte 6M KOH under vacuum and then mounted in a Swagelok-type cell with Viledon 700/18F separator and filled with 30 µL electrolyte. The capacitor cells were subjected to galvanostatic charge–discharge cycling using an Arbin LBT21084 Instrument System. The results are presented in Figure 9.
The cyclic voltammetry (CV) studies of the SPS material unveil that an oxidative reaction occurred when applying 6M KOH. There was one noticeable cathodic peak, which appeared at potentials above 0.6–0.8 V (Figure 8a) depending on the voltage window and at rates above 1 mVs−1 (Figure 8b). At a rate of 1 mVs−1, the cathodic peak was not as pronounced as can be seen in Figure 8b. Similar behavior at low velocities of the potential unfolding when conducting CV was also observed in our previous studies of thermally treated soot material. [10] The presence of the cathodic peak was due to both the oxygen evolution reaction, which was a consequence of the use of an aqueous electrolyte, and the reduction of chlorine to chloride ion [51]. Due to the unsatisfactory specific electrochemical characteristics of the material investigated in an alkaline electrolyte (6M KOH), more in-depth studies of different electrolyte conditions are planned. Such are envisaged as future work in which to combine the synergistic effect of a chlorine-containing salt in the electrolyte with the possibility of the chlorine ion being intercalated or adsorbed in the carbon matrix.

4. Conclusions

A novel stochastic polymerization procedure was successfully performed on household chimney soot to alter its properties and obtain a material suitable for active electrode coating. The free radical synthesis applied involved a combination of newly created Grignard reagent and chlorinated soot, which created new higher molecular compounds in the original waste product. A Raman spectroscopy investigation performed on the pristine soot and on the final product (SPS) unveiled some significant differences in the carbon structure due to the chemical procedures. The observed decrease in intensity of the G-band in the SPS spectrum compared with the pristine soot spectrum meant a raise in disorder in the graphitic structure. That is connected with the functionalization procedures conducted. The newly created functional groups in the soot did exist in the final product (SPS), which is of high importance for supercapacitance applications. Also, the observed decrease in the background fluorescent signal (FS) in the SPS spectrum compared with the pristine soot spectrum, as well as the complete alignment of the SPS spectrum in the Raman region 2100–2800 cm−1, could be regarded as proof for the removal of any random contamination and obtaining a more uniform final product (SPS). The FTIR spectroscopy investigation showed an increase in the intensity of the peaks, where the C-O, C-C and C=C bending vibrations of alkyl aryl ether, esters and alkenes appeared, meaning new bonds were created in the SPS material. Also, an intensity increase observed for the C-H and C-C spectral features in the FTIR spectrum of the SPS sample is evidence that polymerization was performed correctly, and hydrocarbons with longer chains were created, thus increasing the molecular weight in the final material. The results from the XPS investigation are in agreement with the Raman and FTIR spectroscopy studies. The results showed the appearance of key bonds, such as C-Cl, which is a heritage of the successfully conducted chlorination process. Its appearance is also a piece of evidence that the chlorinated soot and the Grignard agent are in non-stoichiometric quantity. The SPS material was applied as an active electrode coating and was subject to electrochemical testing with KOH as an electrolyte. Further investigations to combine the synergistic effect of a chlorine-containing salt in the electrolyte, with the possibility of the chlorine ion being intercalated or adsorbed in the carbon matrix, should give a positive outcome concerning the electrochemical characteristics of the material.

Author Contributions

Conceptualization, M.P. and T.S.; methodology, M.P.; validation, L.S., D.D., T.M. and I.A.; formal analysis, I.A., T.S., L.S. and T.M.; investigation, B.K., M.P., T.S. and D.D.; resources, M.P., I.A., T.M. and T.S.; writing—original draft preparation, M.P., L.S. and I.A.; writing—review and editing, L.S.; project administration, M.P.; funding acquisition, M.P. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Bulgarian National Scientific Fund, grant number KP-06-N57/21.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Acknowledgments

This work was supported by the Bulgarian National Scientific Fund, contract: KP-06-N57/21.

Conflicts of Interest

The authors declare no conflict of interest.

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Coatings 13 01354 g001
Figure 1. Block-scheme of the experimental procedures involved in altering household chimney soot into stochastically polymerized soot (SPS).
Figure 1. Block-scheme of the experimental procedures involved in altering household chimney soot into stochastically polymerized soot (SPS).
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Figure 2. Raman spectra of (a) pristine soot and (b) stochastically polymerized soot (SPS).
Figure 2. Raman spectra of (a) pristine soot and (b) stochastically polymerized soot (SPS).
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Figure 3. Four-band fit for the Raman spectra of (a) pristine soot and (b) stochastically polymerized soot (SPS).
Figure 3. Four-band fit for the Raman spectra of (a) pristine soot and (b) stochastically polymerized soot (SPS).
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Figure 4. FTIR spectra of (a) pristine soot and (b) stochastically polymerized soot (SPS).
Figure 4. FTIR spectra of (a) pristine soot and (b) stochastically polymerized soot (SPS).
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Figure 5. XPS spectra of soot, pristine soot (PS) and SPS.
Figure 5. XPS spectra of soot, pristine soot (PS) and SPS.
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Figure 6. XPS Deconvolution spectrum taken from PS sample (a) C 1s line (b), Cl 2p line.
Figure 6. XPS Deconvolution spectrum taken from PS sample (a) C 1s line (b), Cl 2p line.
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Figure 7. XPS Deconvolution spectrum taken from SPS sample (a) C 1s line (b), Cl 2p line.
Figure 7. XPS Deconvolution spectrum taken from SPS sample (a) C 1s line (b), Cl 2p line.
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Figure 8. (a) CVs within different potential windows at 20 mV s−1 scan rate, (b) CVs at the scan rates of 1, 10, 20 and 50 mV s−1.
Figure 8. (a) CVs within different potential windows at 20 mV s−1 scan rate, (b) CVs at the scan rates of 1, 10, 20 and 50 mV s−1.
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Figure 9. Continuous galvanostatic charge/discharge curves at a current density of 60 mA g−1.
Figure 9. Continuous galvanostatic charge/discharge curves at a current density of 60 mA g−1.
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Table 1. Atomic surface concentrations (%) of the constituent element in the pristine soot sample.
Table 1. Atomic surface concentrations (%) of the constituent element in the pristine soot sample.
Pristine Soot
Concentration (%)C 1sO 1sN 1sCl 2pK 2p
67.6726.083.361.141.76
Table 2. Atomic surface concentrations (%) of the constituent elements in the SPS.
Table 2. Atomic surface concentrations (%) of the constituent elements in the SPS.
SPS
Concentration (%)C 1sO 1sN 1sCl 2pMg 1sSi 2p
57.3520.971.195.220.3314.93
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MDPI and ACS Style

Petrov, M.; Slavov, L.; Stankulov, T.; Karamanova, B.; Milenov, T.; Dimov, D.; Avramova, I. Transforming Chimney Soot via Stochastic Polymerization for Active Electrode Coating. Coatings 2023, 13, 1354. https://doi.org/10.3390/coatings13081354

AMA Style

Petrov M, Slavov L, Stankulov T, Karamanova B, Milenov T, Dimov D, Avramova I. Transforming Chimney Soot via Stochastic Polymerization for Active Electrode Coating. Coatings. 2023; 13(8):1354. https://doi.org/10.3390/coatings13081354

Chicago/Turabian Style

Petrov, Miroslav, Lyubomir Slavov, Toma Stankulov, Boryana Karamanova, Teodor Milenov, Dimitar Dimov, and Ivalina Avramova. 2023. "Transforming Chimney Soot via Stochastic Polymerization for Active Electrode Coating" Coatings 13, no. 8: 1354. https://doi.org/10.3390/coatings13081354

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