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Electrodeposition of polypyrrole on He plasma etched carbon nanotube films for electrodes of flexible all-solid-state supercapacitor

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Abstract

Flexible and portable supercapacitors have been intensively investigated due to their reliable energy storage performance and promising applications in wearable electronic devices. Owing to the unique pseudocapacitance property of conducting polymer and the high conductivity and stability of carbon nanotube film (CNTF), polypyrrole (PPy) was electrodeposited on He plasma etched carbon nanotube film (HCNTF) for electrodes of flexible supercapacitor with high performance. As demonstrated by Raman spectra and contact angle measurement, He plasma etching can produce amorphous carbon on the CNTF and advance the hydrophilicity of the CNTF, which promoted the electrodeposition of PPy onto the CNTFs and improved the adhesion between PPy and CNTF. All-solid-state supercapacitors were fabricated using the PPy/HCNTF electrodes and H3PO4/PVA electrolyte. Cyclic voltammetry tests showed that the capacitive performance of PPy/HCNTF is much higher than that of PPy/CNTF. The specific capacitance of the PPy/HCNTF supercapacitor determined by a galvanostatic charge-discharge method at 0.5 A g−1 is about 414 F g−1, which was maintained 92% after 5000 cycles, reflecting high cycle stability. Moreover, the PPy/HCNTF supercapacitor could remain 96% of the original capacitance when it was bent for 500 times surrounding a cylinder with a diameter of 1.5 cm, showing perfect flexibility and great potential for flexible energy storage devices.

Polypyrrole/He etching carbon nanotube film was prepared for electrodes of supercapacitors. He plasma etching promoted the electrodeposition of polypyrrole and improved the performance of the supercapacitors.

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References

  1. Couly C, Alhabeb M, Van Aken KL, Kurra N, Gomes L, Navarro-Suarez AM, Anasori B, Alshareef HN, Gogotsi Y (2018) Asymmetric flexible mxene-reduced graphene oxide micro-supercapacitor. Adv Electron Mater 4(1):1700339

    Article  CAS  Google Scholar 

  2. Kumar KS, Choudhary N, Jung Y, Thomas J (2018) Recent advances in two-dimensional nanomaterials for supercapacitor electrode applications. Acs Energy Lett 3(2):482–495

    Article  CAS  Google Scholar 

  3. Li X, Tang Y, Song J, Yang W, Wang M, Zhu C, Zhao W, Zheng J, Lin Y (2018) Self-supporting activated carbon/carbon nanotube/reduced graphene oxide flexible electrode for high performance supercapacitor. Carbon 129:236–244

    Article  CAS  Google Scholar 

  4. Lu J, Xu W, Li S, Liu W, Javed MS, Liu G, Hu C (2018) Rational design of CuO nanostructures grown on carbon fiber fabrics with enhanced electrochemical performance for flexible supercapacitor. J Mater Sci 53(1):739–748

    Article  CAS  Google Scholar 

  5. Bora A, Mohan K, Doley S, Dolui SK (2018) Flexible asymmetric supercapacitor based on functionalized reduced graphene oxide aerogels with wide working potential window. ACS Appl Mater Interfaces 10(9):7996–8009

    Article  CAS  PubMed  Google Scholar 

  6. Hu R, Zhao J, Zhu G, Zheng J (2018) Fabrication of flexible free-standing reduced graphene oxide/polyaniline nanocomposite film for all-solid-state flexible supercapacitor. Electrochim Acta 261:151–159

    Article  CAS  Google Scholar 

  7. Lu X, Shen C, Zhang Z, Barrios E, Zhai L (2018) Core-shell composite fibers for high-performance flexible supercapacitor electrodes. ACS Appl Mater Interfaces 10(4):4041–4049

    Article  CAS  PubMed  Google Scholar 

  8. Shao L, Wang Q, Ma Z, Ji Z, Wang X, Song D, Liu Y, Wang N (2018) A high-capacitance flexible solid-state supercapacitor based on polyaniline and Metal-Organic Framework (UiO-66) composites. J Power Sources 379:350–361

    Article  CAS  Google Scholar 

  9. Wang Y, Zhang Y, Zhong W, Qing X, Zhou Q, Liu Q, Wang W, Liu X, Li M, Wang D (2018) Flexible supercapacitor with high energy density prepared by GO-induced porous coral-like polypyrrole (PPy)/PET non-woven fabrics. J Mater Sci 53(11):8409–8419

    Article  CAS  Google Scholar 

  10. Zhang H, Li A, Wang J, Zhang Y, Zhao Z, Zhao H, Cheng M, Wang C, Wang J, Zhang S, Wang J (2018) Graphene integrating carbon fiber and hierarchical porous carbon formed robust flexible “carbon-concrete” supercapacitor film. Carbon 126:500–506

    Article  CAS  Google Scholar 

  11. Chang Z-H, Feng D-Y, Huang Z-H, Liu X-X (2018) Electrochemical deposition of highly loaded polypyrrole on individual carbon nanotubes in carbon nanotube film for supercapacitor. Chem Eng J 337:552–559

    Article  CAS  Google Scholar 

  12. Li J, Lu W, Yan Y, Chou T-W (2017) High performance solid-state flexible supercapacitor based on Fe3O4/carbon nanotube/polyaniline ternary films. J Mater Chem A 5(22):11271–11277

    Article  CAS  Google Scholar 

  13. Song L, Cao X, Li L, Wang Q, Ye H, Gu L, Mao C, Song J, Zhang S, Niu H (2017) General method for large-area films of carbon nanomaterials and application of a self-assembled carbon nanotube film as a high-performance electrode material for an all-solid-state supercapacitor. Adv Funct Mater 27(21):1700474

    Article  CAS  Google Scholar 

  14. Toan Phuoc T, Quyet Huu D (2017) High-performance supercapacitor electrode based on buckypaper/polyaniline composite. J Electron Mater 46:6056–6062

    Article  CAS  Google Scholar 

  15. Yu J, Lu W, Pei S, Gong K, Wang L, Meng L, Huang Y, Smith JP, Booksh KS, Li Q, Byun J-H, Oh Y, Yan Y, Chou T-W (2016) Omnidirectionally stretchable high-performance supercapacitor based on isotropic buckled carbon nanotube films. ACS Nano 10(5):5204–5211

    Article  CAS  PubMed  Google Scholar 

  16. Durukan MB, Yuksel R, Unalan HE (2016) Cobalt oxide nanoflakes on single walled carbon nanotube thin films for supercapacitor electrodes. Electrochim Acta 222:1475–1482

    Article  CAS  Google Scholar 

  17. Fu D, Zhou H, Zhang X-M, Han G, Chang Y, Li H (2016) Flexible solid-state supercapacitor of metal-organic framework coated on carbon nanotube film interconnected by electrochemically-codeposited PEDOT-GO. Chemistryselect 1(2):285–289

    Article  CAS  Google Scholar 

  18. Ma Y-Y, Yi G-B, Wang J-C, Wang H, Luo H-S, Zu X-H (2017) Shape-controllable and -tailorable multi-walled carbon nanotube/MnO2/shape-memory polyurethane composite film for supercapacitor. Synth Met 223:67–72

    Article  CAS  Google Scholar 

  19. Xiang X, Zhang W, Yang Z, Zhang Y, Zhang H, Zhang H, Guo H, Zhang X, Li Q (2016) Smart and flexible supercapacitor based on a porous carbon nanotube film and polyaniline hydrogel. RSC Adv 6(30):24946–24951

    Article  CAS  Google Scholar 

  20. Zhang S-W, Yin B-S, Liu C, Wang Z-B, Gu D-M (2018) NiMoO4 nanowire arrays and carbon nanotubes film as advanced electrodes for high-performance supercapacitor. Appl Surf Sci 458:478–488

    Article  CAS  Google Scholar 

  21. Du D, Wu X, Li S, Zhang Y, Xing W, Li L, Xue Q, Bai P, Yan Z (2017) Remarkable supercapacitor performance of petal-like LDHs vertically grown on graphene/polypyrrole nanoflakes. J Mater Chem A 5(19):8964–8971

    Article  CAS  Google Scholar 

  22. Wang L, Ouyang Y, Jiao X, Xia X, Lei W, Hao Q (2018) Polyaniline-assisted growth of MnO2 ultrathin nanosheets on graphene and porous graphene for asymmetric supercapacitor with enhanced energy density. Chem Eng J 334:1–9

    Article  CAS  Google Scholar 

  23. Yu J, Xie F, Wu Z, Huang T, Wu J, Yan D, Huang C, Li L (2018) Flexible metallic fabric supercapacitor based on graphene/polyaniline composites. Electrochim Acta 259:968–974

    Article  CAS  Google Scholar 

  24. Zhang X, Wang J, Liu J, Wu J, Chen H, Bi H (2017) Design and preparation of a ternary composite of graphene oxide/carbon dots/polypyrrole for supercapacitor application: importance and unique role of carbon dots. Carbon 115:134–146

    Article  CAS  Google Scholar 

  25. Luo S, Zhao J, Zou J, He Z, Xu C, Liu F, Huang Y, Dong L, Wang L, Zhang H (2018) Self-standing polypyrrole/black phosphorus laminated film:promising electrode for flexible supercapacitor with enhanced capacitance and cycling stability. ACS Appl Mater Interfaces 10(4):3538–3548

    Article  CAS  PubMed  Google Scholar 

  26. Moon H, Lee H, Kwon J, Suh YD, Kim DK, Ha I, Yeo J, Hong S, Ko SH (2017) Ag/Au/polypyrrole core-shell nanowire network for transparent, stretchable and flexible supercapacitor in wearable energy devices. Sci Rep 7(1):41981

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  27. Wan C, Jiao Y, Li J (2017) Flexible, highly conductive, and free-standing reduced graphene oxide/polypyrrole/cellulose hybrid papers for supercapacitor electrodes. J Mater Chem A 5(8):3819–3831

    Article  CAS  Google Scholar 

  28. Zhang L, Wang W, Cheng J, Shi Y, Zhang Q, Dou P, Xu X (2018) Skeleton networks of graphene wrapped double-layered polypyrrole/polyaniline nanotubes for supercapacitor applications. J Mater Sci 53(1):787–798

    Article  CAS  Google Scholar 

  29. Liu S, An C, Chang X, Guo H, Zang L, Wang Y, Yuan H, Jiao L (2018) Optimized core-shell polypyrrole-coated NiCo2O4 nanowires as binder-free electrode for high-energy and durable aqueous asymmetric supercapacitor. J Mater Sci 53(4):2658–2668

    Article  CAS  Google Scholar 

  30. Zhu J, Feng T, Du X, Wang J, Hu J, Wei L (2017) High performance asymmetric supercapacitor based on polypyrrole/graphene composite and its derived nitrogen-doped carbon nano-sheets. J Power Sources 346:120–127

    Article  CAS  Google Scholar 

  31. Du D, Wu X, Li S, Zhang Y, Xing W, Li L, Xue Q, Bai P, Yan Z (2017) Remarkable supercapacitor performance of petal-like LDHs vertically grown on graphene/polypyrrole nanoflakes. J Mater Chem A 5(19):8964–8971

    Article  CAS  Google Scholar 

  32. Zhang L, Wang W, Cheng J, Shi Y, Zhang Q, Dou P, Xu X (2018) Skeleton networks of graphene wrapped double-layered polypyrrole/polyaniline nanotubes for supercapacitor applications. J Mater Sci 53(1):787–798

    Article  CAS  Google Scholar 

  33. Zhou Y, Xie Y (2018) Enhanced electrochemical stability of carbon quantum dots-incorporated and ferrous-coordinated polypyrrole for supercapacitor. J Solid State Electrochem 22(8):2515–2529

    Article  CAS  Google Scholar 

  34. Miomandre F, Saba J, Wojcik K, Bai J (2015) Electrochemical synthesis of polypyrrole nanowires on carbon nanotube-coated carbon fibers. J Solid State Electrochem 19(9):2691–2699

    Article  CAS  Google Scholar 

  35. Choi DJ, Bosca A, Pedros J, Martinez J, Barranco V, Rojo JM, Yoo JJ, Kim YH, Calle F (2016) Improvement of the adhesion between polyaniline and commercial carbon paper by acid treatment and its application in supercapacitor electrodes. Compos Interface 23(2):133–143

    Article  CAS  Google Scholar 

  36. Chiu HT, Lin JS (1992) Electrochemical deposition of polypyrrole on carbon fibres for improved adhesion to the epoxy resin matrix. J Mater Sci 27(2):319–327

    Article  CAS  Google Scholar 

  37. Ge D, Huang S, Qi R, Mu J, Shen Y, Shi W (2009) Nanowire-based polypyrrole hierarchical structures synthesized by a two-step electrochemical method. Chemphyschem 10(11):1916–1921

    Article  CAS  PubMed  Google Scholar 

  38. Huang S, Han Y, Lyu S, Lin W, Chen P, Fang S (2017) A facile one-step approach for fabrication of polypyrrole nanowire/carbon fiber hybrid electrodes for flexible high performance solid-state supercapacitors. Nanotechnology 28(43):435204

    Article  PubMed  CAS  Google Scholar 

  39. Liu Z, Zhao Z, Wang Y, Dou S, Yan D, Liu D, Xia Z, Wang S (2017) In situ exfoliated, edge-rich, oxygen-functionalized graphene from carbon fibers for oxygen electrocatalysis. Adv Mater 29(18):1606207

    Article  CAS  Google Scholar 

  40. Krushnamurty K, Reddy PMK, Srikanth I, Prasad PSR, Ghosal P, Subrahmanyam C (2014) The reinforcement ability of plasma-etched carbon nanofibers on mechanical properties of C-epoxy composites. Plasma Process Polym 11(6):588–595

    Article  CAS  Google Scholar 

  41. Hussain S, Amade R, Jover E, Bertran E (2013) Nitrogen plasma functionalization of carbon nanotubes for supercapacitor applications. J Mater Sci 48(21):7620–7628

    Article  CAS  Google Scholar 

  42. Wang J, Xu Y, Chen X, Sun X (2007) Capacitance properties of single wall carbon nanotube/polypyrrole composite films. Compos Sci Technol 67(14):2981–2985

    Article  CAS  Google Scholar 

  43. Hosseini MG, Rasouli H, Shahryari E, Naji L (2017) Electrochemical behavior of a Nafion-membrane-based solid-state supercapacitor with a graphene oxide-multiwalled carbon nanotube-polypyrrole nanocomposite. J Appl Polym Sci 134:44926

    Google Scholar 

  44. Yang LF, Shi Z, Yang WH (2015) Polypyrrole directly bonded to air-plasma activated carbon nanotube as electrode materials for high-performance supercapacitor. Electrochim Acta 153:76–82

    Article  CAS  Google Scholar 

  45. Xu J, Zhu L, Bai Z, Liang G, Liu L, Fang D, Xu W (2013) Conductive polypyrrole-bacterial cellulose nanocomposite membranes as flexible supercapacitor electrode. Org Electron Phys Mater Appl 14:3331–3338

    CAS  Google Scholar 

  46. Raudsepp T, Marandi M, Tamm T, Sammelselg V, Tamm J (2014) Influence of ion-exchange on the electrochemical properties of polypyrrole films. Electrochim Acta 122:79–86

    Article  CAS  Google Scholar 

  47. Mathur A, Roy SS, Hazra KS, Wadhwa S, Ray SC, Mitra SK, Misra DS, Mclaughlin JA (2012) Oxygen plasma assisted end-opening and field emission enhancement in vertically aligned multiwall carbon nanotubes. Mater Chem Phys 134(1):425–429

    Article  CAS  Google Scholar 

  48. Wilhelm H, Lelaurain M, McRae E, Humbert B (1998) Raman spectroscopic studies on well-defined carbonaceous materials of strong two-dimensional character. J Appl Phys 84(12):6552–6655

    Article  CAS  Google Scholar 

  49. Choi C, Lee JA, Choi AY, Kim YT, Lepró X, Lima MD, Baughman RH, Kim SJ (2014) Flexible supercapacitor made of carbon nanotube yarn with internal pores. Adv Mater 26(13):2059–2065

    Article  CAS  PubMed  Google Scholar 

  50. Li S, Zhao C, Shu K, Wang C, Guo Z, Wallace GG, Liu H (2014) Mechanically strong high performance layered polypyrrole nano fibre/graphene film for flexible solid state supercapacitor. Carbon 79:554–562

    Article  CAS  Google Scholar 

  51. Zhao X, Sanchez BM, Dobson PJ, Grant PS (2011) The role of nanomaterials in redox-based supercapacitors for next generation energy storage devices. Nanoscale 3(3):839–855

    Article  CAS  PubMed  Google Scholar 

  52. Zhou Y, Hu X, Shang Y, Hua C, Song P, Li X, Zhang Y, Cao A (2016) Highly flexible all-solid-state supercapacitors based on carbon nanotube/polypyrrole composite films and fibers. RSC Adv 6(67):62062–62070

    Article  CAS  Google Scholar 

  53. Dumée L, Germain V, Sears K, Schütz J, Finn N, Duke M, Cerneaux S, Cornu D, Gray S (2011) Enhanced durability and hydrophobicity of carbon nanotube bucky paper membranes in membrane distillation. J Membrane Sci 376(1-2):241–246

    Article  CAS  Google Scholar 

  54. Yu H, Cheng D, Williams TS, Severino J, Rosa IMD, Carlson L, Hicks RF (2013) Rapid oxidative activation of carbon nanotube yarn and sheet by a radio frequency, atmospheric pressure, helium and oxygen plasma. Carbon 57:11–21

    Article  CAS  Google Scholar 

  55. Chen X, Qiu L, Ren J, Guan G, Lin H, Zhang Z, Chen P, Wang Y, Peng H (2013) Novel electric double-layer capacitor with a coaxial fiber structure. Adv Mater 25(44):6436–6441

    Article  CAS  PubMed  Google Scholar 

  56. Chen T, Peng H, Durstock M, Dai L (2014) High-performance transparent and stretchable all-solid supercapacitors based on highly aligned carbon nanotube sheets. Sci Rep 4:3612

    Article  PubMed  PubMed Central  Google Scholar 

  57. Huang S, Chen P, Lin W, Lyu S, Chen G, Yin X, Chen W (2016) Electrodeposition of polypyrrole on carbon nanotube-coated cotton fabrics for all-solid flexible supercapacitor electrodes. RSC Adv 6(16):13359–13364

    Article  CAS  Google Scholar 

  58. Wu QF, He KX, Mi HY, Zhang XG (2007) Electrochemical capacitance of polypyrrole nanowire prepared by using cetyltrimethylammonium bromide (CTAB) as soft template. Mater Chem Phys 101(2-3):367–371

    Article  CAS  Google Scholar 

  59. Chen T, Fan Y, Wang G, Zhang J, Chuo H, Yang R (2016) Rationally designed carbon fiber@NiCo2O4@polypyrrole core-shell nanowire array for high-performance supercapacitor electrodes. Nano 11(02):1650015

    Article  CAS  Google Scholar 

  60. Zhang R, Yan K, Palumbo A, Xu J, Fu S, Yang E-H (2019) A stretchable and bendable all-solid-state pseudocapacitor with dodecylbenzenesulfonate-doped polypyrrole-coated vertically aligned carbon nanotubes partially embedded in PDMS. Nanotechnology 30(9):095401

    Article  CAS  PubMed  Google Scholar 

  61. Chang ZH, Feng DY, Huang ZH, Liu XX (2018) Electrochemical deposition of highly loaded polypyrrole on individual carbon nanotubes in carbon nanotube film for supercapacitor. Chem Eng J 337:552–559

    Article  CAS  Google Scholar 

  62. Sawangphruk M, Srimuk P, Chiochan P, Krittayavathananon A, Luanwuthi S, Limtrakul J (2013) High-performance supercapacitor of manganese oxide/reduced graphene oxide nanocomposite coated on flexible carbon fiber paper. Carbon 60:109–116

    Article  CAS  Google Scholar 

  63. El-Kady MF, Kaner RB (2013) Scalable fabrication of high-power graphene micro-supercapacitors for flexible and on-chip energy storage. Nat Commun 4(1):1475

    Article  PubMed  CAS  Google Scholar 

  64. Fu Y, Cai X, Wu H, Lv Z, Hou S, Peng M, Yu X, Zou D (2012) Fiber supercapacitors utilizing pen ink for flexible/wearable energy storage. Adv Mater 24(42):5713–5718

    Article  CAS  PubMed  Google Scholar 

  65. Gui Z, Zhu H, Gillette E, Han X, Rubloff GW, Hu L, Lee SB (2013) Natural cellulose fiber as substrate for supercapacitor. ACS Nano 7(7):6037–6046

    Article  CAS  PubMed  Google Scholar 

  66. Sarac AS, Gilsing H-D, Gencturk A, Schulz B (2007) Electrochemically polymerized 2,2-dimethyl-3,4-propylenedioxythiophene on carbon fiber for microsupercapacitor. Prog Org Coat 60(4):281–286

    Article  CAS  Google Scholar 

  67. Zhou Y, Hu XY, Shang YY, Hua CF, Song PX, Li XJ, Zhang YJ, Cao AY (2016) Highly flexible all-solid-state supercapacitors based on carbon nanotube/polypyrrole composite films and fibers. RSC Adv 6(67):62062–62070

    Article  CAS  Google Scholar 

  68. Cherusseri J, Kar KK (2016) Ultra-flexible fibrous supercapacitors with carbon nanotube/polypyrrole brush-like electrodes. J Mater Chem A 4(25):9910–9922

    Article  CAS  Google Scholar 

  69. Yu J, Xie F, Wu Z, Huang T, Wu J, Yan D, Huang C, Li L (2018) Flexible metallic fabric supercapacitor based on graphene/polyaniline composites. Electrochim Acta 259:968–974

    Article  CAS  Google Scholar 

  70. Xiang X, Zhang W, Yang Z, Zhang Y, Zhang H, Zhang H, Guo H, Zhang X, Li Q (2016) Smart and flexible supercapacitor based on porous carbon nanotube film and polyaniline hydrogel. RSC Adv 6(30):24946–24951

    Article  CAS  Google Scholar 

  71. Huang S, Han Y, Lyu S, Lin W, Chen P, Fang S (2017) A facile one-step approach for the fabrication of polypyrrole nanowire/carbon fiber hybrid electrodes for flexible high performance solid-state supercapacitors. Nanotechnology 28(43):435204

    Article  PubMed  CAS  Google Scholar 

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Funding

This work was supported by Zhejiang Provincial Natural Science Foundation of China (No. LQ18E030012) and National Natural Science Foundation of China (No. 51302246).

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  1. National Engineering Lab for Textile Fiber Materials & Processing Technology (Zhejiang), Faculty of Materials and Textiles, Zhejiang Sci-Tech University, Hangzhou, 310018, People’s Republic of China

    Yichuan Han, Peishan Chen, Yanfei Xia, Sanqing Huang, Wenxing Chen & Wangyang Lu

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  1. Yichuan Han
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Han, Y., Chen, P., Xia, Y. et al. Electrodeposition of polypyrrole on He plasma etched carbon nanotube films for electrodes of flexible all-solid-state supercapacitor. J Solid State Electrochem 23, 1553–1562 (2019). https://doi.org/10.1007/s10008-019-04242-4

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