J Solid State Electrochem https://doi.org/10.1007/s10008-017-3801-2 ORIGINAL PAPER Synthesis of ternary polypyrrole/Ag nanoparticle/graphene nanocomposites for symmetric supercapacitor devices Murat Ates 1 & Sinan Caliskan 1 & Esin Ozten 1 Received: 12 August 2017 / Revised: 27 September 2017 / Accepted: 9 October 2017 # Springer-Verlag GmbH Germany 2017 Abstract In this study, novel ternary synthesis of reduced graphene oxide (rGO) sheets via intercalation of Ag nanoparticles (Ag) and polypyrrole (PPy) was obtained for supercapacitor evaluations. The synthesis procedure of nanocomposite is simple, cheap, and ecologically friendly. The nanocomposites were analyzed by Fourier transform infrared-attenuated transmission reflectance (FTIR-ATR) and scanning electron microscopy-energy dispersion X-ray analysis (SEM-EDX). In addition, electrochemical performances of electrode active materials (rGO/Ag/PPy) of the samples were tested by means of galvanostatic charge/discharge (GCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The highest specific capacitance and energy density of rGO/Ag/PPy nanocomposite were obtained as C sp = 1085.22 F/g and E = 36.92 Wh/kg for [rGO] o / [Py]o = 1/5 at 4 mV/s in 1 M H2SO4 solution. Under the optimized preparation conditions in different initial feed ratios ([rGO]o/[Py]o = 1/1, ½, 1/5, and 1/10) of rGO/Ag/PPy, nanocomposites acquired a high Coulombic efficiency, and a retention of 66% of its initial capacitance for [rGO]o/[Py]o = 1/ 10 after 1000 cycles. GCD and EIS measurements of rGO/Ag/ PPy nanocomposite electrode active material allowed for supercapacitor applications. Keywords Ag nanoparticles . Symmetric supercapacitor . Ragone plot . Reduced graphene oxide . Polypyrrole . Power density * Murat Ates [email protected]; https://www.atespolymer.org 1 Physical Chemistry Division, Department of Chemistry, Faculty of Arts and Sciences, Namik Kemal University, Degirmenalti Campus, 59030 Tekirdag, Turkey Introduction Supercapacitors are mostly used in energy storage devices due to their high capacitance, power and energy density, long stability, and environmental friendliness [1, 2]. Polypyrroles are commonly used in parts of electrode active materials for pseudocapacitors of flexible supercapacitors. However, there is a limited usage in cycle life of PPys during charge/discharge performances. To solve this problem, in literature, hybrid electrode materials such as reduced graphene oxide (rGO), metal oxides, nanoparticles, and conducting polymers have been designed to increase capacitance values and improve rate capabilities [3]. Polypyrrole (PPy) is the most commonly used active material among to conducting polymers due to its high charge density, easy preparation, low cost, relatively high conductivity, long charge/discharge performances, and environment friendliness [4–6]. Different types of design of PPy have been presented by scientists like PPy nanoparticles [7], PPy nanowire [8], PPy nanotube [9, 10], PPy graphene using vitamin C [11], and PPy nanofiber [12]. In addition, PPy is synthesized by micro-emulsion technique [13]. PPy/nanofiber materials are obtained by using zeolite, alumina, and other nanostructured templates [14, 15]. Moreover, PPy/carbon aerogel nanocomposites are synthesized by chemically for supercapacitor [16]. Electrospinning technique is also used for PPy nanofiber synthesis [17–19]. Sheng et al. [20] have studied NiCo alloy nanoparticles coated on polypyrrole/rGO nanocomposites (NiCo/PPy/rGO) by in situ chemical polymerization and a co-reduction process for glucose sensing. As a result, NiCo/PPy/GO nanocomposites can be used as electroactive materials for biosensor application of non-enzymatic glucose. However, it has high volume change during the repeated accumulated depletion of ions in the electrochemical charge/ discharge performances. This phenomenon decreases its J Solid State Electrochem mechanical stability [21, 22]. PPy is used for supercapacitors due to its good energy storage capability, high degree of flexibility, high conductivity, and strong hydrophobicity [23, 24]. Therefore, rGO is used as nanofillers in rGO/PPy composite materials [25, 26]. Carbon materials such as graphene, carbon nanotubes, and carbon fibers have many advantages due to their high surface area, good material structure, and better conductivity and hence used in many supercapacitor applications [27, 28]. The chemical reduction of graphene oxide (GO) has been used as one of the most efficient methods for the large production amount of graphene [29, 30], in combination with polymers and nanomaterials for use in biosensors [31, 32], electronics and optoelectronics [33, 34], drug transportation [35, 36], enzyme immobilization [37, 38], and supercapacitors [39, 40]. Li et al. [41] have synthesized PPy-graphene sheet nanocomposites after doing reduced graphene react with tetrazine derivatives through inverse electron demand Diels-Alder reaction. PPy/ graphene nanocomposites with 40% PPy supply a very large capacitance per weight (Csp = 326 F/g at 0.5 A/g) and a small resistance because of a good ion accessibility. Wang et al. [42] have prepared PPy/Fe3O4/rGO nanocomposites to present an electrochemical sensor for dopamine. The results show that it has a low operational voltage ( 0 . 3– 0 .6 V v er s u s SC E ) , a l o w d et ec t i on l i m i t (2.33 nM), a wide linear range (7.0 nm-2.0 muM), and good selectivity for DA over uric acid and ascorbic acid. In the literature, there is a large variance range from 55 to 535 F/g in capacitance properties of carbon nanotube (CNT)/PPy composites, energy density ranges from 3.6 to 84.9 Wh/kg, and cyclability experiments reveal 55– 101% capacitance retention after 5000 cycles [43]. Nanomaterials such as Ag nanoparticles supply to agglomerate due to their high surface energy which inhibits their cycle life, stability as an electrode material, and helps in avoiding such agglomeration [44]. In the literature, a suggested strategy is to engineer ternary nanocomposites combining graphene with two different kinds of materials [45, 46]. Nanocomposites represent a milestone in the present energy scenario, since they are used as electrodes and electrolytes for supercapacitors, batteries [47, 48], and hybrid solar cells [49, 50]. In the literature, Bella et al. [51] have studied natural cellulose fibers which are used as components for bio-derived photo-anodes and polymer electrolytes in dye-sensitized solar cells (DSSCs). They are many advantages such as safety, eco-friendliness, and cheapness [52]. In this work, we present a ternary synthesis of GO/Ag/PPy nanocomposites. Ag nanoparticles and intercalated PPy supply a better accessibility of electrolyte ions into the rGO nanosheets, improved charge accumulation, and supply high electrochemical performance for supercapacitors. Experimental study Materials Pyrrole (> 98%), polyethylene glycol (PEG-400), ptoluene sulfonic acid, FeCl 3·6H2O, hydrazine hydrate, Ag nanoparticles, and cellulose ester membrane were obtained from Sigma-Aldrich. Graphite, zinc (II) chloride, hydrogen peroxide, sodium nitrate, potassium permanganate, hydrochloric acid, acetonitrile, ethyl alcohol, chloroform, ammonia, methanol, and sulfuric acid were purchased from Merck (Darmstadt, Germany). They were used as received. Instrumentations A potansiostat/Galvanostat (iviumstat model; software: iviumsoft and Faraday cage: BASI cell Stand C3) was used for cyclic voltammetry (CV), galvanostatic, chargedischarge (GCD), and electrochemical impedance spectroscopy (EIS) measurements. Supercapacitor devices were run with a two-electrode system. There are many equipments used in various experimental sections, such as accurate balance (Ohaus pioneer), ultrasonic bath (Elma, E3OH, Elmasonic), incubator (Dry-Line, VWR), and deionized water equipment (purelab Option-Q, Elga, DV25, water resistance: 18.2 MΩ·cm). Preparation of rGO/Ag/PPy nanocomposite device We measured the electrochemical performances of devices with CV, GCD, and EIS tests. Stainless steel (SS) electrodes were used as current collectors in supercapacitor devices. rGO and rGO/Ag/PPy films made on different initial feed ratio of [rGO]o/[Py]o = 1/1, ½, 1/5, and 1/10 are flexible and mechanically strong and thus can be directly used as supercapacitor electrodes without using additional binders or additives. We used an ion-porous separator (Celgard 3501, Celgard, and Charlotte, NC) between two electroactive materials in a layered structure. This layered connection was wrapped with Kapton tape and then dipped in 1 M H2SO4 solution. Electrochemical performances were measured by an iviumstat Potansiostat/galvanostat instrument. Results and discussion Preparation of graphene oxide and graphene GO was prepared by a modified Hummer’s method [53–56]. GO (100 mg) was inserted in a 250-mL flask, and added with 100 mL deionized (DI) water. The color J Solid State Electrochem Fig. 1 Schematic illustration and synthesis of graphene from GO of the solution changed from yellow-brownish to light yellow by ultrasonication process. Hydrazine hydrate (32.1 mmol) was added to the solution and heated at 100 °C for 24 h under oil bath. GO reduced to rGO and formed as black solid product. This solid was filtrated by DI water, methanol and dried under vacuum atmosphere. The schematic illustration and synthesis of graphene is given in Fig. 1. Preparation of rGO/Ag//PPy nanocomposites 1 mL polyethylene glycol (PEG-400) and 50 mg GO were added to 6 mL ethyl alcohol solution and mixed with ultrasonication process for 2 h at room temperature. Black-brownish colloidal substance was obtained as a product. 7.22 mmol (483 mg) pyrrole monomer and 0.005 g Ag nanoparticles were added to the solution and mixed in 15 min. 2 mmol p-toluene sulfonic acid (p-TsA) were added at 0–5 °C and mixed in 15 min. 50 mL, 0.34 M FeCl 3 ·6H 2 O aqueous solution (molar ratio of FeCl3/pyrrole is 2.35:1) was added drop by drop and fast oxidation reaction was obtained. Suspension solution was mixed at 0–5 °C for 2 h and polymerization occurs at room temperature for 22 h. The obtained product was filtrated and washed with deionized (DI) water, and ethanol. After that, it dried at 50 °C under vacuum atmosphere for 24 h [57]. The illustration of rGO/Ag/PPy nanocomposite is shown in Fig. 2. FTIR-ATR analysis FTIR-ATR spectra of rGO/Ag/PPy nanocomposites with different feed ratios of [rGO]o/[Py]o = 1/1, ½, 1/5, and 1/ 10 are given in Fig. 3. The peaks at 3219, 3220, and 3221 cm−1 for [rGO]o/[Py]o = 1/1, 1/10, and 1/5 were attributed to N-H stretching. The peaks at 1519 and 1429 cm−1 referred to C-C and C-N stretching. The peak at 1010 cm−1 shows C-H vibration of pyrrole ring [58]. The peak at 1451 cm−1 appeared due to S=O group obtained from p-TsA [59], this peak is due to attachment of bisulfate (HSO 4 − ) group with the PPy. The peak at 1629 cm−1 was obtained from the skeletal vibration of rGO [60]. The peak at 1009 cm−1 is due to the =C-H in plane vibration of the PPy. C-C peak of PPy was obtained at 1135 cm−1, which was shifted to 1140 cm−1 at different [rGO]o/[Py]o = 1/1, ½, 1/5, and 1/10 for nanocomposites [61, 62]. The spectrum of rGO showed an absorption band at 1629 cm−1 for C=C stretching, indicating the replacement of the graphene structure on reduction [63]. The shifting resulted in interactions such as π-π stacking J Solid State Electrochem Fig. 2 Schematic illustration and preparation of rGO/Ag/PPy nanocomposite between PPy and rGO or hydrogen bonding for the residual oxygen functional groups on rGO [64]. SEM-EDX analysis FESEM images of GO, rGO, and rGO/Ag/PPy nanocomposites show the rGO nanoscrolls of different dimensions of embedded into PPy matrix (Figs. 4–5). Figure 4b shows the FESEM image of rGO, the fluffy crumpled image proves the ultra thin layers of rGO [65]. Graphenes can lead the PPy nucleation and deposition on nanosheets during in situ polymerization. PPy densely adhered on the surface of graphene nanosheets and were tightly sandwiched between graphene layers, while some firmly anchored to the edges of graphene nanosheets or bridge the adjacent individual graphene nanosheets [66]. EDX analysis also confirmed higher wt% of carbon (52.64%) as shown in Table 1. It confirmed the efficient exfoliation and reduction of GO to rGO [67]. EDX analysis was Fig. 3 FTIR-ATR spectra of rGO/Ag/PPy nanocomposites with different feed ratios [rGO]o/[Py]o = 1/1, ½, 1/5, and 1/10 J Solid State Electrochem Fig. 4 SEM photographs of a GO, b rGO, and c rGO/Ag/PPy nanocomposite performed to confirm the rGO nanoscrolls embedded into the PPy matrix. EDX spot analysis over the rGO nanosheets in rGO/Ag/PPy showed a low amount of nitrogen (3.38% for GO, and 47.36% for rGO), and a C/O ratio (22.04/73.65 for GO and 52.64/—— for rGO) as given in Table 1. Fig. 5 SEM photographs of rGO/Ag/PPy nanocomposites with different feed ratios of a [rGO]o/[Py]o = 1/1, b [rGO]o/ [Py]o = 1/2, c [rGO]o/[Py]o = 1/5, and d [rGO]o/[Py]o = 1/10 Cyclic voltammetric measurements The specific capacitance of the electrode can be calculated as per the reported methods in the literature according to the following Eq. 1 from CV curves [68–70]: J Solid State Electrochem Table 1 EDX analysis of GO, rGO, PPy and rGO/Ag/PPy nanocomposites with different feed ratios, [rGO]o/]Py]o = 1/1, ½, 1/5, and 1/10 Elements GO rGO rGO/Ag/PPy [rGO]0/[Py]0= 1:1 1:2 1:5 1:10 22.63 18.50 21.86 33.37 18.10 22.78 17.44 22.45 C N 22.04 3.38 52.64 47.36 O 73.65 – 58.32 35.29 32.66 33.64 S Ag 0.93 – – – – 0.52 – 9.48 – 26.46 – 26.47 C sp ¼ ∫ðI dV=Δϑ m ΔV Þ ð1Þ where Csp is the specific capacitance (F/g), I is the discharge current (A), ΔV is the potential window (V), Δϑ is the sweep rate (V/s), and m is the total mass of the electrode active materials (g) (Fig. 6). The CV curves showed that rGO/Ag/ PPy electrode had a rectangular CV curves and also exhibited the mirror image characteristic for all the reported sweep rates up to 1000 mV/s, showing a supercapacitor behavior. There were no oxidation-reduction peaks of CV plots, which pointed out the negligible pseudocapacitance contribution from PPy to the total capacitance of rGO/Ag/PPy nanocomposites [71]. The CV measurements were taken in the potential range between 0.0 and 0.8 V in 1 M H2SO4 solution. Scan rates were taken as 4, 6, 8, 10, 20, 40, 60, 80, 100, 150, 200, 250, 500, 750, and 1000 mV/s. The Csp versus scan rate plots were calculated from CV measurements as shown in Fig. 7. The PPy electrode showed the specific capacitance of Csp = 55.3 F/g at the scan rate of 5 mV/s [72]. The highest specific capacitance of the rGO/Ag/PPy nanocomposite was Csp = 1085.22 F/g for [rGO]o/[Py]o = 1/5 at 4 mV/s and the capacitance decreased by increasing the scan rate as shown in Fig. 7. The specific capacitances of the rGO/Ag/PPy nanocomposite were larger than rGO and GO electrodes. C sp values were obtained as 362.44, 330.73, and 279.21 F/g for [rGO]o/[Py]o = ½, 1/1, and 1/10, respectively. The Csp values of rGO and GO were obtained as 93.18 and 45.16 F/g, respectively, at a scan rate of 4 mV/s. Therefore, the specific capacitance of rGO/Ag/PPy nanocomposite was larger than individual PPy, rGO, and GO electrodes because many combinations of microcapacitors were formed in the nanocomposite material and this resulted in higher specific capacitance. The results were supported by FESEM, GCD measurements, and electrochemical impedance spectroscopic results [73, 74]. The specific capacitance of rGO/Ag/PPy nanocomposite was higher even at a lower scan rate, in comparison to PPy, rGO, and GO electrodes, which can be ascribed to the synergistic effect between rGO, Ag nanoparticles, and PPy [75]. Fig. 6 CV curves for the a rGO, rGO/Ag/PPy nanocomposites in different feed ratios, b [rGO]o/[Py]o = 1/1, c [rGO]o/[Py]o = 1/2, d [rGO]o/[Py]o = 1/5, and e [rGO]o/[Py]o = 1/10 J Solid State Electrochem The power densities of the electrodes were calculated from the ratio of energy densities to discharge time as given in the following Eq. 5 [77]: P ¼ E=t ð3Þ where E is the energy density of the electrode in Wh/kg and t is the discharge time of the CV curve in h, and power densities of 8161.74 and 32,873.97 W/kg were obtained for rGO, and rGO/Ag/PPy nanocomposite at [GO]o/[Py]o = 1/2, respectively at 1000 mV/s. The energy and power density of rGO revealed a low value compared to nanocomposites due to the higher ion diffusion resistance [78]. Fig. 7 Specific capacitance of all rGO, and rGO/Ag/PPy nanocomposites in different initial feed ratios of [rGO]o/[Py]o = 1/1, ½, 1/5, and 1/10 with scan rates, as determined by CV measurements The energy density and power density were calculated according to Eqs 4 and 5, respectively. Figure 8 shows a Ragone plot calculated from the rGO/Ag/PPy with different initial feed ratios of [rGO]o/[Py]o = 1/1, ½, 1/5, and 1/10 and rGO curves. There was an inverse proportional relationship between energy density (E) and power density (P). The energy densities (Wh/kg) of the electrodes were calculated using the following Eq. 4 [76]: E ¼ ðC ΔV Þ=7:2 ð2Þ where C is the specific capacitance in F/g, ΔV is the voltage range in V, and E is the energy of the electrode in Wh/kg. A high energy density of 36.92 Wh/kg was derived from CV data for rGO/Ag/PPy nanocomposites at [rGO]o/[Py]o = 1/5 and 1.11 Wh/kg for rGO 0.98 Wh/kg for GO at a scan rate of 1000 mV/s. Galvanostatic charge/discharge measurements The galvanostatic charge/discharge (GCD) method was used to evaluate the electrochemical capacitance of materials under controlled current densities. The capacitances of GCD of the supercapacitor devices were calculated by the Eq. 2: C dev ¼ iapp =ð−dE=dt Þ ð4Þ where –dE/dt is the slope of the discharge curve and iapp is the discharge current. GCD curves were also obtained at a constant current density of 1 A/g as shown in Fig. 9. ESR is called low internal resistance in energy storage devices. ESR was obtained by the following Eq. 3: ESR ¼ V drop =2 iapp ð5Þ where Vdrop is the voltage drop due to ESR of the capacitor; ESR is the equivalent series resistance of the supercapacitors in ohms, iapp is the discharge current in amperes. The specific capacitance of the rGO/Ag/PPy nanocomposite at [rGO]o/ [Py] o = 1/10 supercapacitor device was 16.15 F/g at 0.135 A/g, which was 8.03 fold higher than that of rGO (C s p = 2.01 F/g at 0.0125 A/g). The rGO/Ag/PPy supercapacitor device had an energy density (E = 4.37 Wh/ kg at 0.273 A/g) and a power density (P = 1421.92 W/kg at 1.36 A/g for [rGO]o/[Py]o = ½. Electrochemical impedance spectroscopic measurements Fig. 8 Energy density versus power density obtained in 1 M H2SO4 solution from CV measurements for rGO, and rGO/Ag/PPy nanocomposites with different feed ratios, [rGO]o/]Py]o = 1/1, ½, 1/5, and 1/10 Electrochemical impedance spectroscopy (EIS) measurements were carried out to investigate the resistivity performances such as the equivalent series resistance (ESR) and charge transfer resistance (Rct) of the electrodes from the starting frequency of 100 kHz to an ending frequency of 10 mHz, as shown in Fig. 10. The ESR includes the electrolyte, electrode resistance and Rct. Rct is the rate of charge transfer at the electrode and electrolyte interface [79]. The calculated Nyquist plot slope value is J Solid State Electrochem Fig. 9 Galvanostatic charge-discharge (GCD) curves of an a rGO, and rGO/Ag/PPy nanocomposites with different feed ratios, b [rGO]o/ ]Py]o = 1/1, c [rGO]o/]Py]o = ½, d [rGO]o/]Py]o = 1/5, e [rGO]o/ ]Py]o = 1/10. Electrode active materials were taken at constant current densities of 0.0125, 0.0137, 0.0690, and 0.135 A/g, respectively, in twoelectrode configuration theoretically parallel to the imaginary axis (vertical line) showing a real capacitance behavior and low ionic diffusion resistance within the electrode structure [80]. The impedance and resistance measurements were obtained from the real part of impedance, and the capacitance values were calculated with the following equation (Eq. 6): Csp ¼ −1= 2 π f Z″ ð6Þ The double layer capacitances (Cdl) were obtained as 0.33, 0.41, 0.14, 0.37, and 0.093 F/g for [rGO]o/[Py]o = 1/1, ½, 1/5, 1/10, and rGO, respectively (Fig. 10b). The highest phase angle ( ) was obtained as = 78o at 1.65 Hz, 73.69o at 37.59 Hz, 79.26o at 1.33 Hz, and 77.78o at.1.66 Hz for [rGO]o/[Py]o = 1/1, 1/5, 1/10, and rGO, respectively (Fig.10c). where, π = 3.14, f is frequency in Hz, and Z″ is the imaginary part of the impedance values. The highest specific capacitance was calculated as Csp = 2.58 F/g for [rGO]o/ [Py]o = 1/5 obtained from Nyquist plot (Fig. 10a). The other Csp values were obtained as Csp = 0.893, 0.297, 0.167, and 0.122 F/g for [rGO]o/[Py]o = 1/1, rGO, [rGO]o/[Py]o = 1/10, and ½, respectively. Double layer capacitance (Cdl) was obtained from a Bodemagnitude plot by extrapolating the linear line to w = 1 (logw= 0) and showing the Eq. 7 as shown in Fig. 10b: IZI ¼ 1=C dl ð7Þ Stability tests for rGO/Ag/PPy nanocomposites Long cycle life is an important factor for supercapacitor electrode materials. The electrochemical stability levels of rGO, PPy, and rGO/Ag/PPy were taken by repeating the CV method in the potential between 0.0 and 0.8 V at 100 mV/s for 1000 cycles (Fig. 11). PPy is well-known to show poor cyclability due to its large volume transformations during repetitive redox (charge/discharge) cycles [81]. PPy can serve as a spacer to further enhance the surface area of GO, resulting in good electrical conductivity and improved cycling stability [82]. We used rGO and Ag nanoparticles in PPy matrix to prevent the degradation during the stability process. rGO electrodes showed almost no decay up to 1000 cycles, demonstrating excellent cycling stability. Figure 11 shows the cycling performance of rGO/Ag/PPy nanocomposites with different J Solid State Electrochem Fig. 10 EIS analysis of rGO, and rGO/PPy nanocomposites in different initial feed ratio of [rGO]o/[Py]o = 1/1, ½, 1/5, and 1/10, a Nyquist plot, b Bode-magnitude plot, c Bode-phase plot. EIS measurements were taken at frequencies between 10 mHz and 100 kHz with a sinusoidal signal amplitude of 10 mV in 1 M H2SO4 initial feed ratios of [rGO]o/[Py]o = 1/1, ½, 1/5, and 1/10 possessed good cycle stability. After 1000 cycles, 58.12, 64.88, 39.55, and 66.00% of initial capacitance were kept for [rGO]o/[Py]o = 1/1, ½, 1/5, and 1/10, respectively. And Coulombic efficiency of rGO/Ag/PPy was kept to near 100%. Conclusion Fig. 11 Stability of rGO, and rGO/PPy nanocomposites in different initial feed ratios of [rGO]o/ [Py]o = 1/1, ½, 1/5, and 1/10 tested by CVs. Scan rate was measured as 100 mV/s for 1000 cycles Novel ternary nanocomposites of rGO/Ag/PPy were chemically synthesized by in situ polymerization method. The obtained active materials were characterized by FTIR-ATR, SEM-EDX, CV, GCD, and EIS analysis. The electroactive material was found to be a suitable electrode for capacitive applications. The cyclic voltammetric data showed an electrode specific capacitance of 1085.22 F/g for [rGO] o / [Py]o = 1/5 at 4 mV/s configured as symmetric supercapacitor. The specific capacitances of rGO and GO show as Csp = 93.18 and 45.16 F/g, respectively. The π-π stacking interaction between rGO and PPy nanocomposites incorporated with Ag nanoparticles enhanced the specific capacitance. A good cycling stability was obtained as ~ 66% capacitance retention after 1000 cycles. The electrochemical studies showed that rGO/Ag/PPy nanocomposite could be used for energy storage applications. Acknowledgements The fact that this study was financed by Namik Kemal University, Tekirdag, Turkey, project number: NKUBAP.01.GA. 16.076 is gratefully acknowledged. Authors also thank Expert Muhammet Aydın (Namik Kemal Uni., NABILTEM, Tekirdag, Turkey) for recording SEM-EDX and FTIR-ATR measurements. 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