Mesoporous polypyrrole-based graphene nanosheets anchoring redox polyoxometalate for all-solid-state micro-supercapacitors with enhanced volumetric capacitance

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  • ReceivedSep 3, 2017
  • AcceptedSep 26, 2017
  • PublishedOct 26, 2017


Micro-supercapacitors (MSCs) have emerged as one competitive candidate of high-performance, flexible, safe, portable and wearable energy storage devices. However, improving their electrochemical performance from electrode materials to assembled devices still remains huge challenges. Here, we for the first time synthesized two-dimensional (2D), ultrathin, mesoporous polypyrrole-based graphene nanosheets uniformly anchored with redox polyoxometalate (mPPy@rGO-POM) by soft template approach. Further, using a layer-by-layer deposition and mask-assisted technique, the compactly stacked and sandwich-like hybrid film (mPGM) based on pseudocapacitive mPPy@rGO-POM nanosheets and electrochemically exfoliated graphene was directly fabricated as binder- and additive-free interdigital electrodes for all-solid-state planar micro-supercapacitors (mPGM-MSCs). Notably, the resulted mPGM-MSCs exhibited outstanding areal capacitance (115 mF cm–2), remarkably enhanced volumetric capacitance (137 F cm–3 at 1 mV s–1) in comparison with MSCs based on the films of mPPy@rGO without POM anchoring (95 F cm–3), and non-porous polypyrrole-graphene (68 F cm–3). Further, mPGM-MSCs disclosed robust mechanical flexibility with ~96% of capacitance retention at a highly bending angle of 180°, and impressive parallel or serial interconnection for boosting capacitance or voltage output. As a consequence, our proposed strategy of filling the redox species into mesoporous graphene and other 2D nanosheets will open up new ways to manufacture high-compact and flexible energy storage devices ranging from supercapacitors to batteries.

Funded by

China Postdoctoral Science Foundation(2016M601348)

the National Natural Science Foundation of China(51572259)

and Exploratory Research Program of Shaanxi Yanchang Petroleum(Group)

National Key R&D Program of China(2016YBF0100100)

Natural Science Foundation of Liaoning Province(201602737)

Recruitment Program of Global Expert(1000)




This work was supported by the National Natural Science Foundation of China (51572259), National Key R&D Program of China (2016YBF0100100 and 2016YFA0200200), Natural Science Foundation of Liaoning Province (201602737), Recruitment Program of Global Expert (1000 Talent Plan), DICP, China Postdoctoral Science Foundation (2016M601348), and Exploratory Research Program of Shaanxi Yanchang Petroleum (Group) Co., LTD & DICP.

Interest statement

The authors declare that they have no conflict of interest.

Contributions statement

Wu ZS proposed and supervised the whole project. Qin J and Ren R conducted the experiments and prepared the MSCs. Zhou F and Xiao H participated in synthesis of EG materials and fabrication of MSCs mask. Qin J and Wu ZS wrote and revised the manuscript. All authors contributed to the discussion and comments of this manuscript.

Author information

Jieqiong Qin is pursuing PhD degree in Dalian Institute of Chemical Physics (DICP), Chinese Academy of Sciences (CAS), under the supervision of Prof. Zhong-Shuai Wu. She received his MS degree in China Research Institute of Daily Chemical Industry in 2016. Her current research focuses on graphene and 2D materials for energy storage devices, such as micro-supercapacitors.

Zhong-Shuai Wu received his Ph.D in materials science from Institute of Metal Research, CAS, in 2011, and worked as a postdoctor at Max-Planck Institute for Polymer Research in 2011-2015. Then he joined DICP, CAS, and was appointed as full Professor, and group leader of 2D Materials & Energy Devices. He has published more than 60 research articles in Adv. Mater., Nat.Commun., JACS, ACS Nano etc., with a total citation of more than 12,000 times. His research focuses on graphene and 2D materials for energy storage devices, such as supercapacitors, micro-supercapacitors, high-energy batteries (Li-S, Li-, K-, Na-ion), flexible and planar energy-storage devices.


Additional detailed calculations, and figures are available in the online version of the paper.


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  • Figure 1

    Scheme of the fabrication of mPPy@rGO-POM nanosheets.

  • Figure 2

    Morphology and structure of mPPy@GO nanosheets. (a, b) SEM images. (c, d) TEM images. (e) AFM image (up) and corresponding height profile (down). (f) N2 adsorption-desorption isotherm and pore size distribution (inset).

  • Figure 3

    (a, b) TEM images of mPPy@rGO nanosheets after reduction. (c, d) TEM and HRTEM images of mPPy@rGO-POM nanosheets. (e) EDX spectrum of mPPy@rGO-POM nanosheets. Cu element is derived from TEM grid used. (f) Raman spectra of mPPy@GO, mPPy@rGO and mPPy@rGO-POM nanosheets.

  • Figure 4

    (a, b) Photographs of mPGM film taken at (a) flat and (b) bending states. (c, d) TEM and HRTEM images of EG nanosheets. (e) Cross-section schematic of sandwich-like mPGM film, showing an EG/mPPy@rGO-POM/EG structure. (f) Top-view SEM image of mPGM film. (g, h) Cross-section SEM images of mPGM film at low and high magnification. (i–m) Cross-section elemental mapping analyses of mPGM film, showing the presence of (i) C, (j) O, (k) Mo, (l) N and (m) P elements.

  • Figure 5

    (a) CV curves tested at 10 mV s–1, (b) areal capacitance, (c) volumetric capacitance as a function of scan rate, and (d) Ragone plot of mPGM-MSCs, mPG-MSCs, and PG-MSCs. (e) CV curves and (f) Ragone plot of mPGM-MSCs based on the varying volume from 1, 2 to 4 mL mPPy@rGO-POM ink.

  • Figure 6

    (a) CV curves measured at 50 mV s–1 of mPGM-MSCs under different bending angles, and (b) capacitance retention as a function of bending angle of mPGM-MSCs. Insets in (b) are optical images of mPGM-MSCs taken at 0 and 180o. (c) CV curves tested at 50 mV s–1 and (d) GCD profiles obtained at 0.5 mA cm–2 of three parallelly-connected mPGM-MSCs. (e) CV curves at 50 mV s–1 and (f) GCD profiles at 0.2 mA cm–2 of three serially-connected mPGM-MSCs. Inset in (f) is a photograph of three serial mPGM-MSCs to power a light-emitting diode.

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