Green polymer electrolyte and activated charcoal-based supercapacitor for energy harvesting application: Electrochemical characteristics

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Introduction
Fossil fuel consumption has caused high levels of pollution, prompting efforts to study and create renewable energy materials.Human tricks, specific energy consumption, and production are the main sources of ruthless green issues, e.g., environmental degradation and global warming [1].Global electrical energy is 44.2% from coal, 38.0% from natural gases, 17.1% from renewable energy, and 0.6% and 5% from fuel oil/diesel and hydro, respectively.The use of coal as an energy source has a significant disadvantage in that it emits CO 2 into the atmosphere and contributes to global warming.Natural biodegradable biopolymers, often referred to as the future "green materials," are showing great promise as ideal hosts for creating biopolymer electrolytes designed for a variety of energy devices [2,3].These biopolymers come from sources like cellulose, starch, chitosan (CH), and alginate, and they stand out for being environmentally friendly, easy to find, and sustainable [4].They naturally decompose over time, resulting in minimal environmental impact, representing a substantial advancement in contrast to conventional energy storage approaches; consequently, they are commonly referred to as "green" polymers [2,4].This innovative approach not only makes energy devices like batteries, fuel cells, and supercapacitors safer and more efficient, but it also aligns with the global trend of using more sustainable resources and reducing waste.Thus, researchers are turning to green polymer membranes for electrochemical devices resembling solar cells, supercapacitors, fuel cells, and batteries to address this.This shift aims to achieve the goal of clean energy that is both sustainable and affordable [5].Minimizing environmental impact is critical in the pursuit of a high-tech future.Micro-sized energy storage will be required for automation and robotics, which could result in a large amount of plastic waste if not properly planned for.
One of the simplest electrochemical devices is electrochemical double-layer capacitors (EDLCs) due to their simple preparation methods, long life cycles, and large power density [6,7].In contrast to conventional batteries, EDLCs do not contain hazardous explosive components, thereby enhancing their safety profile.Moreover, the readiness of EDLCs ensures safety for both individuals and the surrounding environment.Compared to lead acid batteries, EDLC is significantly smaller and has a rapid rate of charging and discharging [8].Carbon has been chosen as the right material to provide a large surface for ion adsorption.Electrostatic interactions between ions and electrons govern the energy storage procedure of an EDLC [9].Activated carbon (AC) stands out as a prime candidate for EDLC electrodes due to its robust chemical and physical properties, large surface area, and porous structure [10].Polyvinyl alcohol (PVA) is widely used to reduce plastic waste because it is a versatile polymer with properties similar to those of natural polymers, such as being eco-friendly, biodegradable, biocompatible, and having good film-forming abilities [11].To achieve the fabrication of polymer electrolyte films with superior performance, an approach known as polymer blending can be employed, wherein additional polymers are incorporated into the polymer host.When two polymers are combined together, their functional groups will act as channels for ionic transportation [12].It is widely recognized that polymer blends have a high concentration of functional groups, which enhances their performance in assorted fields such as drug delivery, energy storage devices (ESDs), polymer electrolytes, and tissue engineering [13].PVA has been reported to be biocompatible with various polymers such as hydroxypropylmethylcellulose [14], dextran [15], starch [16], methylcellulose [17], and pectin [18].
CH is another excellent green polymer.CH has a linear structure made up of (1,4)-linked-2-amino-deoxy-glucan units derived via chitin deacetylation.After cellulose, chitin is the most prevalent carbohydrate on the planet [19].CH is widely used in the green polymer edible film industry due to its film-forming properties [20].In the food industry, CHs films are employed as bioactive packaging for the preservation of apples, raspberries, cherimoya, kiwi, and loquat [21][22][23][24][25].The functional groups in the linear CH polymer chains also play a crucial role in ionic conduction, making CH a good choice for a greener future with economic and environmental benefits [26].
Glycerol is important in enhancing the performance of polymer-based electrolytes as it increases salt dissociation and ionic conductivity.This is due to glycerol's high dielectric property, which weakens the forces between cations and anions [27][28][29].The addition of the right amount of glycerol boosts the ionic conductivity and mechanical strength of green polymers.In this work, a glycerol-based CH-PVA polymer electrolyte will be tested with sodium acetate (NaOAc) as the ionic source.The best performing films will be used as separator in EDLC fabrication.According to the study, incorporating green polymer electrolytes in an EDLC assembly has resulted in a breakthrough.The assembled EDLC recorded a high specific capacitance (∼74 F•g −1 ), which is similar to values recorded for liquid and gel-based electrolytes.The electrolyte used in the EDLC assembly also displayed a relatively high energy density, comparable to that of leadacid batteries, as illustrated in Figure 1.Previous research indicates that EDLC devices, which have energy densities comparable to batteries, could potentially revolutionize energy resources through the use of nontoxic materials.However, the low energy density of EDLC devices has prevented their commercialization.As a result, many research groups and companies are concentrating on developing EDLC devices with exceptionally high energy density.This would allow for novel opportunities in energy storage and expand knowledge regarding standards such as the Ragone plot for electrochemical devices.The current study's results, involving an EDLC device that delivers high energy density and excellent performance over 500 cycles, could stimulate discussion regarding the future of EDLC devices and their potential to replace battery technology.This research presents promising insights into the development of solid biopolymer electrolytes, offering potential solutions for sustainable energy storage systems.• ) was a solvent.All these chemicals were procured from Sigma Aldrich and employed in their as-received state without any further purification.The standard solution casting method was used to create the solid polymer electrolyte films.0.5 g of CH and 0.5 g of PVA were dissolved in a 1% CH 3 COOH solution and distilled water, respectively, at 80°C.After combining the CH and PVA solutions separately, they were blended together at room temperature for 6 h to form the CH-PVA blend solution.To create the NaOAc doped samples, 40% salt was added to the mixture.After that, we made several plasticized polymer electrolytes by adding varying quantities of glycerol to the CH-PVA-NaOAc-based polymer mix electrolyte samples.The glycerol content ranged from 11 to 55 wt% in step 11.For easy identification, the samples were labeled as CSPVNACT1, CSPVNACT2, CSPVNACT3, CSPVNACT4, and CSPVNACT5 incorporated with 11, 22, 33, 44, and 55 wt% of glycerol.Upon transferring the specimens into distinct labeled Petri dishes, they were allowed to gradually dry under ambient conditions (∼30°C) and at a relative humidity of 22% for a duration of 10 days.To ensure absolute absence of moisture within the samples, further drying was employed by putting the samples in a desiccator loaded with silica gel.This careful process yielded fully dried solid polymer electrolyte (SPE) films with a thickness of 0.0278 cm, ready for characterization and the construction of an EDLC device.For accurate film thickness determination, measurements were conducted using a digital micrometer, specifically the Mitutoyo Absolute Micrometer 1D-C112XBS model.

Transference number measurement (TNM) study
The contribution of each charge carrier in an EDLC was analyzed with TNM to enhance its high performance.The analysis was conducted using a V&A Instrument DP3003 digital DC power supply.The current was recorded using a UT803 True RMS multimeter, which was connected to a computer for data extraction.The ionic (t i ) and electronic (t e ) transference numbers were determined using an equation at a voltage of 0.2 V: where I cf and I b are the constant flow and beginning cur- rent, respectively.In the measurement procedure, a circular segment of the most conducting CH-PVA-based SPE, was introduced between a pair of chemically inert stainless steel (SS) electrodes.These electrodes were designed with a compressed spring mechanism to ensure optimal contact.In a Teflon casing, the electrolyte sample was positioned between to SS electrodes.Green polymer electrolyte and activated charcoal-based supercapacitor  3

Linear sweep voltammetry (LSV) study
The ability of the SPE film as an energy storage option was evaluated using LSV.The strength, redox reactions, and behavior of the film within a range of 0-3.5 V at a sweeping rate of 50 mV•s −1 were examined through LSV.The investigation was completed with a Digi-IVY DY2300 Potentiostat.The top-performing CH-PVA electrolyte was positioned among two SS electrodes and enclosed in a Teflon casing for LSV analysis.
The electrode and electrolyte configurations used in the LSV study, which relied solely on the most conductive electrolyte, are depicted schematically in Figure 2.This sandwich configuration allows for precise and controlled measurements of the film's electrochemical behavior and its ion transport properties in which both electrodes were constructed of SS. • ) and PVdF from Merck and agitated continuously for about 5 h using a magnetic stirrer bar operating at low speed.The end product was a dark, viscous slurry that was applied over an aluminum current collector using a 0.25 mm doctor blade.The electrodes were dehydrated at 60°C for a few hours before being cooled to room temperature and placed in a desiccator to further dry.The electrodes were cut into circular forms of ∼2 cm in diameter and utilized as the negative electrode in a CR2032 coin cell for testing, with the best-performing polymer electrolyte sheet sandwiched between the two electrodes.Within this investigation, AC serves as the electrode substance due to its chemical durability, exceptional conductivity, substantial specific surface area exceeding 2,000 m²•g −1 , and notable porosity.

Device characterizations 2.5.1 Cyclic voltammetry (CV) study
The method of charge storage in EDLC is based on capacitive charge separation, as opposed to redox reactions.To affirm this mechanism, the EDLC was subjected to a CV study.The capacitance (C cyc ) was tracked as the scan rate was incrementally adjusted from 10 to 100 mV•s −1 .The C cyc was computed using the following mathematical expression: The CV plot area, I V V d ( ) , was calculated using Origin 9.0 software with the integration function.The starting and ending potentials (V i andV f ) were set as 0 and 1 V, respectively, with "m" representing the mass of AC and "x" representing the scan rate.

Galvanostatic charge-discharge (GCD) of assembled EDLC
The GCD test was conducted using a − 1.4 mA cm 2  • current density and a NEWARE battery cycler.The key EDLC parameters counting, specific capacitance (C s ), energy and power densities (E and P), equivalent series resistance (ESR), and efficiency (η) were the focus of this research: where the symbol "s" stands for the decline in the discharge region, "V dr " denotes the decrease in potential, and "i" represents the current density in operation.3 Result and discussion

EIS and AC conductivity study
The characterization of ionic conductivity in polymeric materials can be effectively carried out through the use of electrochemical impedance spectroscopy [30].This technique allows for the determination of inter-particle interactions, including grain and grain boundary effects, through the analysis of complex impedance data [31].Figure 4 displays the Cole-Cole plot for the plasticized systems to determine the DC conductivity.Typically, the frequency domain analysis of impedance spectra yields two distinct regions, a half-circle at high frequency and a line at low frequency.It has been suggested that the low-frequency (LFr) line arises from the contribution of blocking electrodes, while the highfrequency (HFr) half-circle reflects the ionic conduction mechanism of the bulk electrolyte [32][33][34].The interface between electrodes and electrolyte samples can be viewed as a capacitor in the presence of blocking electrodes.When the impedance is ideal, the impedance plot displays a vertical spike.It is notable that an increase in plasticizer concentration is known to result in a decline in the HFr semicircle diameter [35].Each sample's bulk resistance (R b ) is shown in the insets of the impedance charts.The equation given below indicates that the DC ionic conductivity in polymer-based electrolytes is linked to the ion density and mobility [36]: where n, q, and µ denote the total number of ions, charge of ions, and ionic mobility, respectively.According to the formula, increasing either ion mobility or charge carrier density results in improved DC ionic conductivity.By following up on impedance plots and locating the real axis value at the semicircle's lowest point, one may estimate the dc value.Following is an equation that could be used to compute the DC conductivity: where A and t represent the area and thickness of the sample, respectively [37].Table 1 lists the DC conductivity of the polymer electrolytes (PEs) in which the conductivity boosts with glycerol incorporation as the glycerol improves more mobile ions into the PE and decreases the R b .The reduction in R b leading to its minimum value corresponds to the attainment of the highest conductivity (7.56 × 10 −5 S•cm −1 ), indicating the successful interaction among the components of the electrolyte.The LFr spike appearance in Figure 4(b-e) indicates dissociation of more salts by glycerol and thus increase in conductivity.This is attributed to the improved flexibility of the polymer chains, which helps in faster migration of ions.

AC conductivity
In Figure 5, the frequency dependency of the AC conductivity in the CH-PVA-NaOAc-glycerol systems is demonstrated.Conductance spectra typically exhibit three regions: an LFr zone due to a proper electrode polarization (EP), a plateau region representing the DC conductivity of the system, and an HFr zone due to bulk structural interactions.
Determining AC conductivity in disordered materials can be a complex task due to the diverse range of charge states that are present [38][39][40].
The frequency behavior provides a valuable tool for evaluating the localization of states.A remarkable conductivity dispersion is a hallmark of electrical conduction in disordered materials, often described as a combination of a frequencyindependent term and a frequency-dependent contribution [39].The equation below summarizes this relationship: where σ(ω) signifies the total conductivity, and σ ac and σ dc denote the frequency-dependent AC conductivity and frequency-independent DC conductivity, respectively.The alternating current conductivity is given by the expression (Aω S ), where A is a temperature-dependent parameter, and ω is a power law exponent.This research showed that the doped systems had two distinct regions: an LFr dispersion zone originated by ion-blocking at the electrode-electrolyte interface, and a plateau mid-frequency area that reflects bulk conductivity [39].The DC conductivity, extrapolated from the plateau area to zero frequency, was found to be in agreement with the Cole-Cole plotted values.At low frequencies, the conductance was observed to be high due to the buildup of charges at the electrodes, while at intermediate frequencies, low applied field duration and a gradual charging procedure led to an AC conductivity value similar to DC conduction [38][39][40].

Dielectric properties
The complex dielectric permittivity (ε) of materials is given as ′′ = ′ + ε ε jε .Figures 6 and 7 demonstrate the variation in ′ ε and ′′ ε parameters alongside frequency, correspond- ingly.The ′ ε represents the charge storages, whereas ′′ ε represents the amount of energy lost during movement of ions [41,42].The ′ ε and ′′ ε were retrieved from the real and imaginary sections of complex impedance spectroscopy using the formulae given below: The symbol C o represents vacuum capacitance, ω = 2πf indicates the angular frequency, and f represents the working frequency.At low frequencies, EP at the electrode surface causes a dispersion region to appear.Meanwhile, high frequencies exhibit a plateau region due to the ionic dipoles' inability [41,42].The connection among the dielectric constant and the quantity of free ions in the electrolytes is as follows: where U displays the dissociation of energy, k B is the Boltzmann constant, and n o denotes the pre-exponential factor.Figure 6 shows how the ′ ε readings improved after the increment in glycerol concentrations.The system with 55 wt% glycerol shows the best ′ ε value, indicating the largest number of free ions in the system.This result is consistent with the EIS and AC conductivity results.In the study, the dielectric constant has a lower value than the dielectric loss, indicating that the movement of the carriers contributes to the dielectric loss value [43][44][45].The high ′′ ε value at LFr is due to the mobility of the free charges inside the material.These values do not accurately represent the intrinsic bulk dielectric characteristics of the material, primarily due to the accumulation of free charges at the interface between the electrodes and the electrolyte.At LFr, there is enough time for charges to collect at the interfaces prior to the reversed dielectric field, leading to a noticeable high rate of ′ ε .However, at HFr, there is no enough time for charges to store at the boundary, but only polarize at the bulk of the materials.This results in conductivity relaxation [46].Additionally, at LFr zones, ions and dipoles have enough time to bring into line themselves in the trend of the applied electric field.As a result, the aggregation of charge carriers at the boundary produces EP, which decreases the HFr dielectric characteristics (bulk properties) [47].
Ionic conductivity in polymer electrolytes is a multifaceted process affected by salt concentration and dissociation, polymeric host dielectric characteristics, chain flexibility, and ion aggregation [44,48].A key feature of ion-conducting polymer electrolytes is their ionic conductivity; the dielectric study of these systems is also of great importance in gaining an understanding of ion transport and ion-molecule  interactions in solid polymer electrolytes [49].Figure 8 shows the variation in loss tangent (tanδ) against frequency for the CSPVNACT electrolytes.It can be seen that the loss tangent peaks of the CSPVNACT samples change in frequency as a function of the plasticizer concentration.The relaxation peaks observed in the plasticized electrolytes could be attributed to almost complete ion relaxation times.The presence of a relaxation process in the CSPVN-ACT samples signifies that glycerol enhances the segmental motion of the polymer blend chains, consequently promoting increased free volume and improved ion transport [50,51].Quick segmental motion and ionic mobility both contribute to ionic transport within the CH-PVA blending matrix.Table 2 shows the relaxation time values extracted from frequency peaks.It shows that adding plasticizers via salt dissociation could enhance carrier concentration and segmental motion and thus reduce the required time for DC conduction [52].The peak shifts to the HFr side, demonstrating the shorter relaxation period.The outcomes of the present investigation are in line with those reported in prior studies [53].The dielectric field and polarization are in phase at low frequencies, while the polarization lags behind the electric field frequency at high frequencies.The dielectric loses energy and emits heat as a consequence of the phase change.When the relaxation process is equal to the duration of the applied electric field, maximum loss tangent is obtained, resulting in a resonant state [54].According to Jiang et al. [55], the principal reason of the rise in the loss tangent (tanδ) with increasing frequency of operation is resistive losses.This phenomenon arises due to the challenge faced by the ionic mobility of the electrolyte samples in keeping pace with HFr electric fields.As can be seen in Figure 8, the tanδ value increases with frequency, climbs to its maximum value, and then declines.Moreover, the highest loss tangent value shifts to high frequency along with an increase in glycerol concentration.

LSV study
The LSV is used to determine the breakdown voltage of polymer electrolyte membranes.The application of voltage will reveal any redox reactions within the polymer electrolyte.Figure 9 presents the breakdown voltage profile of the CH-PVA electrolyte film, which demonstrates exceptional stability.No significant current is observed as the film is subjected to a linear potential sweep from 0 to +2.33 V.This represents the creation of a charge double-layer (CDL) at the interface of the polymer electrolyte and SS electrodes.When the potential exceeds 2.33 V, the current value sharply increases.The plot established that the CH-PVA film has decomposed beyond +2.33 V, which indicates the degradation of oxide or oxidation of functional groups [56].This phenomenon triggers the polarization process to be unstable.This is a general idea that the performance of the EDLC will be unstable at potentials greater than 2.33 V.As reported by Vahini et al. [57], the Na-based polymer electrolyte film exhibited instability in its current response when the applied potential exceeded 2 V.A study indicated that a polymer electrolyte incorporating sodium iodide (NaI) as the ionic source and methylcellulose as the polymer host demonstrated electrochemical stability up to   Green polymer electrolyte and activated charcoal-based supercapacitor  9 1.7 V [58].Hence, the optimized CH-PVA electrolyte in this work can be useful in low voltage energy storage applications.

Transference number study
Most ESDs rely on the ionic species of the polymer electrolyte.Ions are required in an EDLC to ensure that the energy storage process can be done via the CDL.TNM analysis is one of the easiest ways to check the dominance of a charge carrier.Figure 10 presents the TNM plot of the most conducting CH-PVA film at 0.2 V driving voltage.Both electrons and ions were thought to contribute equally to the current, hence 6.3 μA was the first value used for I b .But it was not long until the current value dropped dramatically, leveling out at a constant 1 μA.Small, steady current flow shows that the SS electrodes are successfully inhibiting ion flow.When a certain voltage is applied to the electrolyte, both anions and cations flow toward their respective electrodes, where a CDL develops on the electrodes' surfaces, through which only electrons may pass [59,60].Based on the outcome, it is verified that polarization, which is important for an EDLC, is possible in CH-PVA electrolyte.Ions have been established as the principal charge carriers governing the overall conduction, attributed to the elevated concentration of t i (0.84).Polyethylene oxidesodium thiocyanate (NaSCN) electrolyte is reported to have a t i of 0.89 [61].Ibrahim et al. [62] reported a polyurethane-NaI system with a t i of more than 0.8.As the inclusion of sodium fluoride (NaF) increased from 6 to 10 wt%, the t i of PVA-polyvinylpyrrolidone film increased from 0.89 to 0.909 [63].cause the energy storage, which is known as a non-Faradaic capacitor.Through CV analysis, the existence of non-Faradaic processes in the EDLC was verified.The CV curve when the scan rate was lowered from 100 to 20 mV•s −1 is shown in Figure 11(a) and (b) displays the specific capacitance as opposed to scan rate.As observed in Figure 11(a), the CV curve of the EDLC at 100 mV•s −1 looks like the shape of a typical leaf, where the calculated C cyc is 9.4 F•g −1 .At a rapid scan rate, the development of the CDL is unstable due to the imbalance conduction of ions [64].As the scan rate decreased to 50 and 20 mV•s −1 , the C cyc is obtained as 20 and 38 F•g −1 , respectively.The curve at the edges of the plot of 20 mV•s −1 is smaller than 50 and 100 mV•s −1 .Furthermore, the plot has deviated to a rectangular-like shape at 20 mV•s −1 .This indicates a low internal resistance.The efficient and stable transport of ions occurs at a low current flow, allowing complete polarization of ions. Figure 12 shows the schematic design of the fabricated EDLC.Obtaining a perfect rectangular shape CV plot is challenging due to the roughness of the carbon electrodes, as their porosity causes a varying distance between ions in the electrolyte and their corresponding active sites in the AC electrode.Figure 13 shows the mechanism of CDL formation in EDLC.The absence of humps or peaks in the plot confirms that the EDLC in this work functions as a non-Faradaic capacitor, exhibiting the scan rate-dependent characteristics typical of capacitor cells.

Charge-discharge of the assembled EDLC
The charge-discharge curve for the EDLC is displayed in Figure 14 for a number of cycles.The EDLC is charged to a maximum of 1 V and then discharged down to 0 V.Because of the electrostatic interaction between the ions in the electrolyte and the electrons in the electrodes, the curve should normally have a triangular form.However, because of the intercalation and de-intercalation processes, the discharge curve for ordinary batteries is often nonlinear [65].
Figure 15 shows the CH-PVA-based EDLC's capacitance (C s ) and efficiency when the current density is − 1.4 mA cm 2  • as a function of the cycle number.The C s values remain almost constant, with an average of 77 F•g −1 .When the sample material is placed between the electrodes, the charge carriers move through the polymer electrolyte film and form the EDLC.This results in ion polarization stabilization and charge accumulation on both electrodes.The efficiency of an EDLC is considered high if its discharge time is close to or greater than its charge time.The initial cycle had an efficiency of 71.3%.Initially, charging usually takes longer than discharging, until stability is reached.However, after the 50th cycle, the efficiency remains consistently high, ranging between 99% and 100%.This result shows that the EDLC has exceptional stability over multiple cycles [66][67][68].
The ESR is a crucial factor for determining the quality of the electrolyte-electrode interface and the internal resistance of an EDLC. Figure 14 shows a noticeable voltage drop (V dr ) before the discharge process.The EDLC's average V dr was around 0.12 V. Figure 16    Green polymer electrolyte and activated charcoal-based supercapacitor  11 between the electrodes and the electrolyte in the EDLC [66].Lower ESR values indicate a good connection between the electrodes and the electrolyte, allowing for efficient charge carrier conduction to the electrodes and the formation of a CDL through electrostatic interactions [69].
Figure 17 illustrates the changes in E and P in the constructed EDLC throughout 500 cycles.The stored energy begins at 10.6 Wh•kg −1 during the first cycle and ultimately stabilizes at 10.7 Wh•kg −1 .Because of comparable energy barriers, the mobile ions in the CH-PVA polymer matrix may readily migrate toward the electrodes [70].EDLCs built of biopolymers, according to Winie et al. [71], may have energy densities varying from 0.57 to 2.8 Wh•kg −1 , depending on the change in current density from 2 to 0.6 mA•cm −2 .The stability of energy density and capacitance patterns suggests that ionic aggregation is unlikely.At the beginning of the first cycle, the P value is 1,139 W•kg −1 and swings somewhat, with an average P of 1,188 W•kg −1 .Because charge transfer is connected with the gap between the electrolyte and electrodes, P has a high association with ESR [72].
ESDs need to store a lot of energy and provide quick access to electricity when needed.To compare different ESDs, scientists use the Ragone plot, which shows the relationship between energy density (Wh•kg −1 ) and power density (W•kg −1 ) on a logarithmic scale.Examples of ESDs include batteries, capacitors, supercapacitors, flywheels, and magnetic ESDs, which occupy different regions on the Ragone plot.When choosing an ESD, power density is an important factor to consider.The study suggests that EDLC devices based on biopolymers are the future of energy storage, but more research is needed to ensure consistent results.To achieve this, researchers need to carefully prepare films, encapsulate the ESDs properly, and analyze the results thoroughly.Our group is working on developing EDLC ESDs that are as good as or better than batteries.To our knowledge, EDLC is the future of ESDs, provided that it can store energy like a battery.The goal for EDLC in the future is shown in Figure 18, and achieving it will help protect us from toxic materials and reduce the effects of temperature changes on our environment.

Conclusion
A polymer blend electrolyte composed of CH, PVA, NaOAc, and glycerol has been created as a means of reducing plastic waste, particularly micro-plastics, in oceans.This material was found to be suitable for use as an electrode separator in an AC-based EDLC.It was found that at 55% glycerol, the system revealed a high ionic conductivity of 7.56 × 10 −5 S•cm −1 .The dielectric property study confirmed the ionic conduction process in the system and revealed the existence of non-Debye type relaxation, as indicated by asymmetric peaks of the loss tangent pattern.The alternating conductivity exhibits EP, a plateau (mid frequency region) and dispersion region at high frequency.The majority of the conductivity in the electrolyte was due to ions, with a contribution of 0.84, while electrons contributed only 0.16.The highest conducting CH-PVA-NaOAc-glycerol electrolyte has a potential limit of 2.33 V and can be applied in various electrochemical applications.With no redox peaks in the CV plot and a scan rate-dependent capacitance of 9.4-38 F•g −1 , it was clear that the EDLC exhibited capacitive behavior.In the future, the use of other plasticizers such as sorbitol and polyethylene glycol could increase the salt dissociation and improve the specific capacitance of the electrolyte.Additionally, replacing NaOAc with a salt with lower lattice energy may also increase the conductivity value.The charge and discharge measurement of the CH-PVA-NaOAc-glycerolbased EDLC showed an average specific capacitance of 77 F•g −1 , an ESR of 87 Ohms, an energy density of 10.7 Wh•kg −1 , and a power density of 1,188 W•kg −1 .The EDLC also demonstrated high cycling ability by completing 500 charge-discharge cycles.The performance of the EDLC, can be improved by incorporating nano-fillers, polymer grafting, and utilizing different types of carbon, salt, and polymers to enhance both electrodes and electrolytes, which are key components of EDLC.Ensuring tight contact between the electrodes and electrolytes is crucial in achieving this improvement.In conclusion, microbial-based EDLC has proven to be a viable option for lowvoltage applications.

Figure 1 :
Figure 1: The Ragone plot for various electrochemical devices.

Figure 2 :
Figure 2: Schematic showing the LSV analysis electrolyte and electrode setup.

Figure 3
Figure3depicts the methods and materials needed to create AC electrodes.A planetary ball miller was used to combine dry AC with carbon black (CB).To prevent excessive air bubble formation, the AC-CB powder was added to a solution of N-methyl pyrrolidone (anhydrous, 99.5%, − M : 99.13 g mol W 1

Figure 3 :
Figure 3: The fabrication process of the EDLC.

Figure 5 :
Figure 5: AC conductivity plot for the plasticized systems to distinguish EP, DC, and dispersion regions.

Figure 6 :Figure 7 :
Figure 6: The variation in ε′ against frequency for the CSPVNACT samples.

Figure 11 :
Figure 11: (a) CV curves of the CH-PVA based EDLC at various scan rates and (b) specific capacitance as opposed to scan rate.

Figure 14 :
Figure 14: The GCD for the EDLC device.

Figure 15 :
Figure 15: Calculating the EDLC's efficiency over 500 cycles and its specific capacitance.

Figure 16 :
Figure 16: ESR plot of the assembled CH-PVA based EDLC throughout the 500 cycles.

Figure 17 :
Figure 17: The E and P of the assembled EDLC.

Figure 18 :
Figure 18: The obtained energy density position in Ragone plot.

Table 1 :
DC ionic conductivity of the CSPVNACT samples

Table 2 :
Relaxation time extracted from peak frequency