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16. Nano-CrOx Enkapsüle Edilmiş Polipirolün Elektrokimyasal Sentezi ve Süperkapasitör Uygulaması.

Author

Karaca, Erhan

Abstract

Nano-sized PPy/CrOx composite was deposited on a graphite foil (GF) surface using multi-cyclic voltammetry via simultaneous synthesis of PPy and CrOx from an acetonitrile/HBF4/LiBF4/solution containing pyrrole and Cr(BF4)3. The electrochemical properties of the composite were examined using CV and EIS techniques in a Li2SO4 solution, and it was characterized by FESEM, EDX, TEM, and XPS methods. This study revealed that oxygen-deficient CrOx containing Cr(II), Cr(III), and Cr(VI) oxidation states could be synthesized in acetonitrile, unlike in aqueous medium. CrOx with a 6% ratio was encapsulated within the partially oxidized PPy clusters thanks to the simultaneous synthesis of components. The specific capacitance of the PPy/CrOx composite-coated electrode with a mass loading of 4 mg cm-2 was 150 F g-1 at 50 mV s-1, which was higher than that of PPy. Thus, it could be revealed that a small amount of nano CrOx provided a considerable pseudocapacitive contribution to the composite. An asymmetric supercapacitor cell was constructed with PPy/CrOx composite- and PVC/carbon-coated GF electrodes in a polyvinyl alcohol (PVA)/Li2SO4 gel electrolyte. The cell exhibited an energy density of 20.1 Wh kg-1 and a power density of 3.50 kW kg-1 at 5 A g-1. [ABSTRACT FROM AUTHOR]

Published
2024
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17. In situ electrosynthesis of polypyrrole/nano Bi2O4 composite for supercapacitor applications.

Author

Karaca, Erhan

Abstract

Polypyrrole/Bi2O4 (PPy/Bi2O4) composite is synthesized by an electrochemical process in acetonitrile in the presence of Py monomer and Bi(BF4)3 on the surface of the stainless steel mesh (SSM) for supercapacitor anode via in-situ formation of the components. The properties of the resulting coating are analyzed using various techniques: EIS, cyclic voltammetry, XPS, XRD, TEM, and FESEM. The Bi2O4 interphase with a ratio of 3.2% occurs in the mixed valence states of Bi(III) and Bi(V) from Bi(BF4)3 during the electrosynthesis of PPy. Thus, Bi2O4 nanoparticles are homogeneously encapsulated in partially oxidized PPy clusters and significantly affect the electrical properties of the binder-free coating. The pseudocapacitive contribution (72.3%) in the composite becomes predominant at high scan rates thanks to the fast redox reaction of both components. The PPy/Bi2O4-coated electrode exhibits a specific capacitance of 312 F g−1 (at 50 mV s−1) in 100 mM Li2SO4, a more capacitive response than that of the PPy homopolymer-coated electrode. A solid-state asymmetric cell is constructed using PVA/Li2SO4 electrolyte and two types of electrodes loaded with 10 mg cm−2: one coated with PPy/Bi2O4 and the other coated with PVC/carbon. The device demonstrates specific energy of 19.8 Wh kg−1, specific power of 1380 W kg−1 at 2.5 A g−1, and coulombic efficiency of 97% with high stability of 83% over 5000 cycles. [ABSTRACT FROM AUTHOR]

Published
2023
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20. Galvanostatic Synthesis Of Nanostructured Ag-Ag2O Dispersed Ppy Composite On Graphite Electrode For Supercapacitor Applications

Author

Karaca, Erhan, Gokcen, Dincer, Pekmez, Nuran Ozcicek, and Pekmez, Kadir

Abstract

Polypyrrole (PPy) and nanostructured Ag-Ag2O were co-deposited galvanostatically on the Ag-intercalated graphite electrode in acetonitrile/TBABF(4) solution with AgBF4, Py, HBF4, H2O, and sodium carboxymethyl cellulose (CMC). The effects of additives and intercalation on the capacitive behaviors of PPy-Ag-Ag2O-CMC composite (4.0 mg/cm(2)) were studied in H2SO4 (0.1 M) solution by using cyclic voltammetry and electrochemical impedance spectroscopy methods. The composite coating was characterized using X-ray photoelectron spectroscopy, transmission electron microscopy, X-ray diffraction (XRD), Brunauer, Emmett, and Teller, and scanning electron microscopy (SEM) energy dispersive X-ray spectroscopy. The incorporation of nano-sized Ag-Ag2O particles and CMC into the composite has significant impacts on the morphology, which also greatly influences the capacitive performance. XRD and SEM studies showed that the electrochemical intercalation of silver in acetonitrile medium provided partially exfoliated surface of graphite, thus the capacitive properties further enhanced. The capacitive properties of the composite coating were also tested using the galvanostatic charge-discharge method. The specific capacitance of the composite coated electrode was calculated as 500 F/g at 2.0 A/g in H2SO4 solution by subtracting the capacitance of bare graphite electrode. Asymmetric and symmetric supercapacitor configurations were utilized to examine the capacitive performance of PPy-Ag-Ag2O-CMC composite (10 mg/cm(2)) on Ag-intercalated graphite paper. The asymmetric supercapacitor providing a power density of 0.51 kW/kg at 2.0 A/g and an energy density of 23.6 Wh/kg maintains 62% of its capacitance after 5000 cycles.

Published
2020

21. 4.2 V Stack Of Metal Oxide-Polypyrrole-Based Composite Electrodes And Their Power Management

Author

Karaca, Erhan, Gokcen, Dincer, Pekmez, Nuran Ozcicek, Pekmez, Kadir, Ugur, Merve, and Aksu, N. Dogancan

Abstract

Polypyrrole (PPy)-based composites containing nanostructured VO x, PbO x, and MnO x are galvanostatically synthesized on exfoliated graphite papers (1.0 and 6.25 cm(2)) formed as a result of the intercalation with their metals. Both intercalation and synthesis are performed in the synthesis solution containing metal(II)tetrafluoroborate salts, pyrrole monomer, HBF4, H2O, Triton-X 100 (TX100), and carboxymethyl cellulose (CMC). The mass loading of the composite at the electrode is maintained at 10 mg cm(-2). Symmetric and asymmetric unit cells are prepared in polyvinyl alcohol (PVA)/H2SO4 (1:1) gel electrolyte using composites synthesized on the treated graphite paper electrode. The electrical properties of these cells are examined by electrochemical impedance spectroscopy and their capacitive properties by cyclic voltammetry and galvanostatic-charge discharge test. The asymmetrical cell, prepared with PPy/PbO x/CMC composite having energy density and cycle life better than others, exhibits 7.77 Wh kg(-1) and 0.51 kW kg(-1) at a working voltage of 1.4 V, considering the total mass of all sub-components. The three-cell asymmetric stack design, which is prepared using these composite-coated electrodes, achieves a coulombic efficiency of 76% at 4.2 V. Finally, an electronic control system (DC/DC buck-boost converter) is designed and implemented to manage the charge and discharge cycles of single-cell and bipolarly connected stack to operate the asymmetric supercapacitor arrays with high performance.

Published
2020

26. Electrochemical synthesis of composite materials based on polypyrrole containing nano-sized metal oxide for supercapacitor energy storage applications

Author

Karaca, Erhan, Özçiçek, Nuran, Kimya, and Kimya Anabilim Dalı

Subjects
Energy, Energy storage, Nano-Buyutlu Metal Oksit, Süperkapasitör, Konu Başlıkları Listesi::Bilim, Spectroscopic analysis, Enerji, Kimya, Enerji depolama, Elektrokimyasal Sentez, Chemistry, Polipirol, Analytical chemistry, Kompozit
Abstract

There is an increasing demand for the development of high performance, clean and sustainable energy systems and energy storage due to the rapid depletion of fossil fuels, and their environmental issues. One of the important candidates among energy storage system is the supercapacitors due to their high power density, efficiency and cycle life. This dissertation aims to investigate the galvanostatic synthesis of polypyrrole (PPy) composites with nano-structured VOx, PbOx, Ag-Ag2O, MnOx, CoOx, NiOx, and FeOx on their own metal (M)-intercalated graphite surfaces. PPy and metal oxides were simultaneously synthesized by using galvanostatic method in acetonitrile solution containing pyrrole, MBF4 salts, tetrabutylammonium tetrafluoroborate (TBABF4), HBF4, H2O, and sodium carboxymethyl cellulose (CMC). The effects of additives and graphite intercalation on the capacitive behaviors of PPy/MOx/CMC composites (4.0 mg/cm2, 0.0244 cm2) were studied in 100 mM H2SO4 solution by using cyclic voltammetry and electrochemical impedance spectroscopy (EIS) methods. XRD, TEM, XPS, SEM-EDX, and BET techniques were used for the composite characterization. It was determined that nano-sized (3-100 nm) metal oxides homogeneously dispersed in PPy, and the coating surface areas increased, compared to homopolymer. The capacitive properties of the composite coatings were examined by means of the galvanostatic charge-discharge test. The highest specific capacitance value was recorded for PPy/PbOx/CMC coating, whereas the lowest was for PPy/FeOx/CMC coating. For applications, the capacitive behaviors of composites (10.0 mg cm-2, 0.2 cm2) were examined in split test cell with two electrodes (symmetric and asymmetric) containing polyvinyl alcohol-H2SO4 gel electrolyte. PPy composites with PbOx, VOx and MnOx were also tested with higher electrode area (1.0 cm2 and 6.25 cm2). The highest specific capacitance (165 F g-1), energy density (22.9 Wh kg-1), and power density (0.36 kW kg-1) at 2.0 A g-1 were determined for asymmetric supercapacitor based on PPy/PbOx/CMC composite (10.0 mg cm-2, 1.0 cm2) on Pb-intercalated graphite sheet. The asymmetric cell in a potential range of 1.0 V maintained 91% of its capacity after 1000 cycles. Lastly, a three asymmetric cell stack with the nano-sized PbOx dispersed PPy composite electrode yielded 3.0 V potential. The findings in the study, demonstrate the viability of asymmetric supercapacitor, are promising for the possible future applications. Bu tez çalışması ve ilgili yayınlar TÜBİTAK ARDEB 1001 – Bilimsel Ve Teknolojik Araştırma Projelerini Destekleme Programı “KBAG 117Z340” numaralı “Enerji Depolanması için Elektrokimyasal Olarak Elde Edilen İletken Polimer-Metal Oksit Kompozit Elektrot Malzemeleri Kullanılarak Süperkapasitör Hazırlanması” isimli projeyle desteklenmiştir. İÇİNDEKİLER Sayfa ÖZET i ABSTRACT iii TEŞEKKÜRLER v İÇİNDEKİLER vi ŞEKİLLER DİZİNİ ix ÇİZELGELER DİZİNİ xiii SİMGELER VE KISALTMALAR xv 1. GİRİŞ 1 2. GENEL BİLGİLER 3 2.1. SÜPERKAPASİTÖRLER 3 2.1.1. Elektrolitler 6 2.1.1.1. Sulu Elektrolitler; 7 2.1.1.2. Organik Elektrolitler; 7 2.1.1.3. İyonik Sıvılar; 7 2.1.2. Elektrotlar 8 2.1.2.1. Metal Oksitler 8 2.1.2.2. İletken Polimerler 8 Polipirol 11 2.1.2.3. İletken Polimerlerin Kompozitleri 13 Metal Oksitler ile Kompozitler 13 Karboksimetil Selüloz ile Kompozitler 14 Triton X-100 ile Kompozitler 15 2.1.3. Süperkapasitör Üretimi 15 2.1.4. Süperkapasitörlerle İlgili Çalışmalar 16 3. DENEYSEL ÇALIŞMALAR 21 3.1. Kimyasallar 21 3.2. Elektrokimyasal Biriktirme ve Testler 22 3.3. Kaplamaların karakterizasyonu 24 3.4. İki Elektrotlu Konfigurasyonlar 24 3.5. KULLANILAN YÖNTEMLER 26 3.5.1. Raman Spektroskopisi 26 3.5.2. X Işınları Kırınımı (XRD) 26 3.5.3. X Işınları Fotoelektron Spektroskopisi (XPS) 27 3.5.4. Geçirimli Elektron Mikroskobu (TEM) 28 3.5.5. BET (Brunauer Emmett–Teller) Yüzey Alanı Ölçümü 28 3.5.6. Taramalı elektron mikroskobu SEM, EDX ve EDX Haritalama 28 3.5.7. Dönüşümlü Voltametri (CV) 29 3.5.8. Kronopotansiyometri 30 3.5.9. Galvanostatik Şarj-Deşarj 30 3.5.10. Elektrokimyasal Empedans Spektroskopisi (EIS) 31 4. SONUÇLAR VE TARTIŞMA 34 4.1. Polipirol/metal (V, Pb, Ag, Mn, Co, Ni, Fe) oksit kompozitlerinin Asetonitril Ortamında Grafit Yüzeyine Elektrokimyasal Sentezi 34 4.1.1. PPy/VOx Kompozitinin sentezi 35 4.1.1.1. PPy/VOx Kompozitinin Potansiyodinamik yöntemle Sentezi 35 4.1.1.1. PPy/VOx Kompozitinin Galvanostatik Sentezi 38 4.1.1.1. PPy/VOx Kompozit Sentezine Katkıların Etkisi 40 4.1.1.2. Grafit Elektrodun Vanadyum ile İnterkalasyonu 43 4.1.1.3. V-int. KG Yüzeyine PPy/VOx/CMC Kompozitinin Galvanostatik Sentezi ………………………………………………………………………….45 4.1.1.4. PPy/VOx/CMC Sentezine Katkıların ve İnterkalasyonun Etkisinin Elektrokimyasal Empedans Spektroskopisi ile İncelenmesi 48 4.1.2. Diğer PPy/Metal Oksit Kompozitlerinin Galvanostatik Sentezi 49 4.2. Elektrotların Karakterizasyonu 51 4.2.1. Metal-interkale elektrodun karakterizasyonu 51 4.2.2. PPy/Metal Oksit Kaplı Elektrotların Karakterizasyonu 53 4.2.2.1. XRD 53 4.2.2.2. XPS 55 4.2.2.3. TEM 56 4.2.2.4. BET 58 4.2.2.5. SEM-EDX 58 4.3. Kompozitlerin Galvanostatik Şarj Deşarj Testleri 60 4.3.1. Üç Elektrotlu Sistem 60 4.3.2. İki Elektrotlu Sistem 68 4.4. Büyük Ölçekte Hazırlanan Bazı Kompozitlerin İki Elektrotlu Simetrik ve Asimetrik Hücre Davranışlarının İncelenmesi 81 4.4.1. Elektrokimyasal Empedans Spektroskopisi 82 4.4.2. Dönüşümlü Voltamogram 86 4.4.3. Galvanostatik Şarj-Deşarj Testi 89 4.5. Elektrokimyasal Üç Hücreli Asimetrik Yığın (Stack) Testi 94 5. YORUM 98 6. KAYNAKLAR 101 7. EKLER 117 EK 1 117 EK 1.1. KOMPOZİTLERİN SENTEZİ 117 EK 1.2. ELEKTROTLARIN KARAKTERİZASYONU 132 EK 2 – TEZDEN TÜRETİLMİŞ YAYINLAR 150 EK 3 – TEZDEN TÜRETİLMİŞ BİLDİRİLER 151 EK 4 – TEZ ÇALIŞMASI ORJİNALLİK RAPORU 152 ÖZGEÇMİŞ 153 Fosil yakıtların tükenmesi ve çevresel sorunlar, yüksek performanslı, temiz ve sürdürülebilir enerji sistemlerinin geliştirilmesini ve enerji depolanmasını önemli hale getirmiştir. Enerji depolama sistemleri arasında en önemli adaylardan biri olan süper kapasitörler yüksek güç yoğunluğuna, verime ve döngü ömrüne sahiptirler. Bu tez çalışması metal (M) interkale grafit yüzeylerine VOx, PbOx, Ag-Ag2O, MnOx, CoOx, NiOx ve FeOx içeren polipirol (PPy) kompozitlerinin galvanostatik sentezini araştırmayı amaçlamaktadır. PPy ve metal oksitler, pirol, MBF4 tuzları, tetrabütilamonyum tetrafloroborat (TBABF4), HBF4, H2O ve sodyumkarboksimetil selüloz (CMC) içeren asetonitril çözeltilerinde eş zamanlı sentezlenmesiyle kompozit kaplı elektrotlar hazırlandı. Katkıların ve grafit interkalasyonunun PPy/MOx/CMC kompozitin (4.0 mg/cm2, 0.0244 cm2) kapasitif davranışı üzerine etkisi sulu H2SO4 çözeltisi (100 mM) içinde, dönüşümlü voltametri ve elektrokimyasal empedans spektroskopisi (EIS) yöntemleri kullanılarak araştırıldı. Kompozit kaplamaları karakterize etmek için XRD, TEM, XPS, SEM-EDX, BET ve RAMAN teknikleri kulanıldı. PPy içinde homojen olarak dağılmış metal oksitlerin nano-boyutta (3-100 nm) olduğu ve homopolimerinkine göre kaplama yüzey alanının arttığı belirlendi. Kompozit kaplamaların kapasitif özellikleri galvanostatik şarj-deşarj testleri ile incelendi. En yüksek kapasitans değerini PPy/PbOx/CMC kaplama, en düşük değeri de PPy/FeOx/CMC kaplama sağladı. Uygulamaya dönük çalışmalar için kompozitin (10.0 mg cm-2, 0.2 cm2) kapasitif davranışları iki elektrotlu split test hücresinin simetrik ve asimetrik konfigürasyonları kullanılarak polivinilalkol-H2SO4 jel elektrolitinde incelendi. PbOx, VOx ve MnOx içeren PPy kompozitleri daha büyük alanlı elektrotlar (1.0 cm2 ve 6.25 cm2) ile kurulan test hücrelerinde de denendi ve Pb-interkale grafit kağıt yüzeyindeki PPy/PbOx/CMC kompozitinden (10.0 mg cm-2, 1.0 cm2) hazırlanmış asimetrik süperkapasitörde 2.0 A g-1’da spesifik kapasitansı 165 F g-1, enerji yoğunluğu 22.9 Wh kg-1 ve güç yoğunluğu 0.36 kW kg-1 olarak bulundu. Bu elektrodun 1.0 V potansiyel aralığında 1000 döngü sonunda kapasitesinin % 91 ini koruduğu belirlendi. Son olarak, nano-boyutlu PbOx içeren kompozit elektrodu ile hazırlanmış üç hücreli asimetrik yığının %70 kulombik verim ile 3.0 V potansiyel sergilediği gözlendi. Bu sonuçlar asimetrik konfigurasyonlu süperkapasitörün uygulanabilirliğini göstermekte ve gelecekteki olası uygulamalar için umut vadetmektedir.

Published
2019

28. Galvanostatic synthesis of nanostructured Ag‐Ag2O dispersed PPy composite on graphite electrode for supercapacitor applications.

Author

Karaca, Erhan, Gökcen, Dinçer, Pekmez, Nuran Özçiçek, and Pekmez, Kadir

Subjects
*SUPERCAPACITOR electrodes, *SODIUM carboxymethyl cellulose, *ENERGY dispersive X-ray spectroscopy, *GRAPHITE composites, *X-ray photoelectron spectroscopy, *ENERGY density
Abstract

Summary: Polypyrrole (PPy) and nanostructured Ag‐Ag2O were co‐deposited galvanostatically on the Ag‐intercalated graphite electrode in acetonitrile/TBABF4 solution with AgBF4, Py, HBF4, H2O, and sodium carboxymethyl cellulose (CMC). The effects of additives and intercalation on the capacitive behaviors of PPy‐Ag‐Ag2O‐CMC composite (4.0 mg/cm2) were studied in H2SO4 (0.1 M) solution by using cyclic voltammetry and electrochemical impedance spectroscopy methods. The composite coating was characterized using X‐ray photoelectron spectroscopy, transmission electron microscopy, X‐ray diffraction (XRD), Brunauer, Emmett, and Teller, and scanning electron microscopy (SEM) energy dispersive X‐ray spectroscopy. The incorporation of nano‐sized Ag‐Ag2O particles and CMC into the composite has significant impacts on the morphology, which also greatly influences the capacitive performance. XRD and SEM studies showed that the electrochemical intercalation of silver in acetonitrile medium provided partially exfoliated surface of graphite, thus the capacitive properties further enhanced. The capacitive properties of the composite coating were also tested using the galvanostatic charge–discharge method. The specific capacitance of the composite coated electrode was calculated as 500 F/g at 2.0 A/g in H2SO4 solution by subtracting the capacitance of bare graphite electrode. Asymmetric and symmetric supercapacitor configurations were utilized to examine the capacitive performance of PPy‐Ag‐Ag2O‐CMC composite (10 mg/cm2) on Ag‐intercalated graphite paper. The asymmetric supercapacitor providing a power density of 0.51 kW/kg at 2.0 A/g and an energy density of 23.6 Wh/kg maintains 62% of its capacitance after 5000 cycles. [ABSTRACT FROM AUTHOR]

Published
2020
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30. Memristive behavior of TiOx obtained via Pb(II)-assisted anodic oxidation process.

Author

Gokcen, Dincer, Şentürk, Orhun, Karaca, Erhan, Pekmez, Nuran Özçiçek, and Pekmez, Kadir

Subjects
TITANIUM dioxide, LEAD, ELECTROLYTIC oxidation, COPPER, PLATINUM
Abstract

Memristive devices are of promising systems enabling the potential applications of neuromorphic circuits, logical operations, and non-volatile memories. This study introduces a low-cost and feasible TiOx formation process for memristive devices with Cu/TiOx/Ti/Cu and Pt/TiOx/Ti/Pt layers. In the proposed device, active material TiOx is produced by anodic oxidation of Ti using cyclic voltammetry in 100 mM Methane sulfonic acid (CH3SO3H) aqueous solution containing Pb(CH3SO3)2. The influence of Pb2+ content in the anodic oxidation process is evaluated using cyclic voltammetry and electrochemical impedance spectroscopy (EIS). Particularly, EIS results indicate that an increase in the Pb2+ content in the solution improves the conductivity of TiOx films. The conductivity improves with the insertion of more oxygen deficiency to TiOx. The structural identity and oxide thicknesses are worked out using Scanning Electron Microscopy, Low Angle X-Ray Diffraction (XRD) and Ellipsometry. Addition of Pb2+ to CH3SO3H solution significantly improves the oxidation rate and increasing the amount of Pb2+ in the solution produces a thicker oxide layer. Low Angle XRD analysis suggests the TiOx formation, including oxygen-deficient (Magneli) phase, on Ti. Our findings indicate that during the anodic oxidation, a soluble oxygenated Pb4+ compound, (Pb(OH)22+), occurs and instead of contributing to PbO2 deposition, it shows a catalytic effect on TiOx formation. I-V measurements are conducted to investigate memristive behavior. Increasing the amount of Pb2+ content in the anodization solution yields wider hysteresis referring to more distinguishable ON/OFF states for electronic applications. [ABSTRACT FROM AUTHOR]

Published
2019
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31. An Enzyme‐free H2O2 Sensor Based on Poly(2‐Aminophenylbenzimidazole)/Gold Nanoparticles Coated Pencil Graphite Electrode.

Author

Teker, Mine Şen, Karaca, Erhan, Pekmez, Nuran Özçiçek, Tamer, Uğur, and Pekmez, Kadir

Subjects
*ENZYMES, *GOLD nanoparticles, *GRAPHITE, *ELECTRODES, *ELECTROCHEMICAL analysis
Abstract

A poly(2‐aminophenylbenzimidazole)/gold nanoparticles (P2AB/AuNPs) coated disposable pencil graphite electrode (PGE) was fabricated as an enzyme‐free sensor for the H2O2 determination. P2AB/AuNPs and P2AB were successfully synthesized electrochemically on PGE in acetonitrile for the first time. The coatings were characterized by scanning electron microscopy, X‐ray diffraction spectroscopy, Energy‐dispersive X‐ray spectroscopy, Surface‐enhanced Raman spectroscopy, and UV‐Vis spectroscopy. AuNPs interacted with P2AB as carrier enhances the electrocatalytic activity towards reduction of H2O2. The analytical performance was evaluated in a 100 mM phosphate buffer solution at pH 6.5 by amperometry. The steady state current vs. H2O2 concentration is linear in the range of 0.06 to 100 mM (R2=0.992) with a limit of detection 3.67×10−5 M at −0.8 V vs. SCE and no interference is caused by ascorbic acid, dopamine, uric acid, and glucose. The examination for the sensitive determination of H2O2 was conducted in commercially available hair oxidant solution. The results demonstrate that P2AB/AuNPs/PGE has potential applications as a sensing material for quantitative determination of H2O2. [ABSTRACT FROM AUTHOR]

Published
2019
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33. Electrosynthesis of binder-free polypyrrole/nano- Bi2O3-Bi2O2CO3composite for supercapacitor anode

Author

Karaca, Erhan

Abstract

β-Bi2O3-Bi2O2CO3dispersed polypyrrole (PPy/β-Bi2O3-Bi2O2CO3) composite is electrochemically deposited on stainless steel mesh (SSM) surface in an acetonitrile solution of pyrrole monomer and pre-synthesized β-Bi2O3-Bi2O2CO3nanoparticles. The coating is characterized compared with those of the PPy homopolymer coating and β-Bi2O3-Bi2O2CO3powder using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), XPS, XRD, TEM, and FESEM. Flower-shaped spherical nanoparticles containing β-Bi2O3-Bi2O2CO3phases are encapsulated in the partially oxidized PPy clusters composed of small nanospheres, thus dispersed well in the composite. The PPy/β-Bi2O3-Bi2O2CO3coating exhibits a more capacitive behaviour than the PPy coating due to the electro-generation of Bi5+in the β-Bi2O3-Bi2O2CO3phases during the synthesis of composite and the supercapacitor cycling. The coated electrode provides a higher pseudocapacitive contribution (67.4 %) thanks to the mixed metal oxide of β-Bi2O3-Bi2O2CO3in addition to PPy, exhibited a specific capacitance of 360 F g−1in 100 mM Li2SO4. Bi2O2CO3with a layered structure contributes to enlarge of active surface area, conductivity, and catalytic performance. A solid-state asymmetric cell is fabricated with polyvinyl alcohol (PVA)/Li2SO4using 10 mg cm−2mass-loaded PPy/β-Bi2O3-Bi2O2CO3composite- and polyvinyl chloride (PVC)/carbon- coated SSM electrodes. The device provides 64.2 Wh kg−1specific energy and 350 W kg−1specific power at 0.5 A g−1with a coulombic efficiency of 90 % and high stability of about 97 % for 5000 cycles. The electrode has the potential to be used as a binder-free electrode in high-performance supercapacitors.

Published
2023
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35. Nano MnOxencapsulated pyrrole-carbazole copolymer and polyvinyl chloride/carbon-coated flexible electrodes for solid-state supercapacitor cell

Author

Karaca, Erhan, Özgenç, Gökhan, Pekmez, Nuran Özçiçek, and Pekmez, Kadir

Abstract

Pyrrole (Py) and carbazole (Cz) monomers are polymerized simultaneously in the presence of MnOxnanoparticles synthesized chemically on a stainless steel mesh (SSM) electrode by the pulse galvanostatic method in an acetonitrile medium. The resulting p(Py-co-Cz)/MnOxcomposite is characterized by cyclic voltammetry EIS, GCD XPS, XRD, FESEM, BET, and TEM. Since the current is applied for short periods in the presence of both monomers, p(Py-co-Cz) copolymer chains occur in short lengths, suitable for supercapacitor electrodes. The copolymer has higher Cmand lower Rctvalues as well as higher porosity that improves ion transport, thus greater stability than the homopolymers. It may be due to tricyclic Cz segments located between Py segments in the chains, which inhibit degradation. During the synthesis, nano-sized MnOxis also encapsulated homogeneously into the p(Py-co-Cz) coating, where 5 % is the weight percentage of manganese. Since the composite combines the advantages of the conductive polymer and metal oxide, it has the lowest Rctand highest Cmvalues among the coatings here. The p(Py-co-Cz)/MnOxcoating with 10 mg cm−2exhibits a high specific capacitance of 352 F g−1at 5 A g−1as well as flexibility, as its specific capacitance remains nearly stable (99 %) up to a bending angle of 90°. The cathode prepared from polyvinyl chloride (PVC)/activated carbon/carbon black on SSM operates within a wide voltage range of 0 to −1.5 V at 98 % cycle stability after 1000 cycles. The asymmetric cell configuration with the flexible anode and cathode electrodes provides 38 kW kg−1and 5.28 Wh kg−1at 5 A g−1at a wide potential range of 2.1 V in PVA/Na2SO4gel electrolyte, and the cycling stability was 67 % after 1000 cycles.

Published
2022
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