Capillary shrinkage of graphene oxide hydrogels

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  • ReceivedNov 30, 2019
  • AcceptedDec 3, 2019
  • PublishedDec 5, 2019


Conventional carbon materials cannot combine high density and high porosity, which are required in many applications, typically for energy storage under a limited space. A novel highly dense yet porous carbon has previously been produced from a three-dimensional (3D) reduced graphene oxide (r-GO) hydrogel by evaporation-induced drying. Here the mechanism of such a network shrinkage in r-GO hydrogel is specifically illustrated by the use of water and 1,4-dioxane, which have a sole difference in surface tension. As a result, the surface tension of the evaporating solvent determines the capillary forces in the nanochannels, which causes shrinkage of the r-GO network. More promisingly, the selection of a solvent with a known surface tension can precisely tune the microstructure associated with the density and porosity of the resulting porous carbon, rendering the porous carbon materials great potential in practical devices with high volumetric performance.

Funded by

the National Natural Science Fund for the Distinguished Young Scholars


the National Natural Science Foundation of China(51702229,51872195)

the CAS Key Laboratory of Carbon Materials(KLCM,KFJJ1704)

Shenzhen Basic Research Project(ZDSYS201405,09172959981)


This work was supported by the National Natural Science Fund for the Distinguished Young Scholars, China (51525204), the National Natural Science Foundation of China (51702229 and 51872195), the CAS Key Laboratory of Carbon Materials (KLCM KFJJ1704).

Interest statement

The authors declare no conflict of interest.

Contributions statement

Yang QH conceived and supervised the study. Qi C and Tao Y designed the experiment and Qi C carried out it. Qi C, Luo C, Tao Y and Yang QH discussed the data. Lv W, Zhang C, Deng Y, Li H, Han J, Ling G provided the technical support and commented the results.

Author information

Changsheng Qi received his Bachelor’s degree and Master’s degree of applied chemistry from the North University of China in 2005 and 2008, respectively. He is a PhD candidate under the guidance of Prof. Quan-Hong Yang. His research interest focuses on the liquid phase assembly and mechanism of GO, and its applications.

Chong Luo received his Bachelor’s degree of materials science and engineering from the Central South University in 2013 and now is a PhD candidate under the guidance of Prof. Quan-Hong Yang and Prof. Wei Lv. His research interest focuses on the liquid phase assembly of GO and mechanism study on energy storage.

Ying Tao is an associate professor at the School of Chemical Engineering and Technology at Tianjin University. Her main research interests focus on the assembly of low dimensional materials, carbon-based materials and their applications in electrochemical energy storage and environmental remediation.

Quan-Hong Yang joined Tianjin University as a full professor in 2006 and became a Chair Professor in the same university in 2016. His research focuses on novel functional carbon materials with the applications in energy and environmental fields. Specifically, he has made significant advances in high volumetric performance EES devices and the catalysis in lithium-sulfur batteries. See http://nanoyang.tju.edu.cn for more details about Nanoyang Group.


Supplementary information

Experimental details and supporting data are available in the online version of the paper.


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  • Figure 1

    (a) Two typical assembly models for conventional carbon materials, which can be regarded as assemblies with graphene as building blocks; (b) preparation of different porous carbons by removing residual solvents in different ways.

  • Figure 2

    Capillary shrinkage of r-GO hydrogels using two solvents with almost the same boiling point yet different surface tensions. (a) An integral r-GO hydrogel obtained after hydrothermal treatment; (b, c) SEM images and inset photos of the monoliths obtained by immersion of patent hydrogels in water or 1,4-dioxane for solvent-exchange and then dried; (d) XRD patterns of these r-GO monoliths; (e) N2 adsorption-desorption isotherms; (f) BET surface area and (g) PSD of the resulting HPGM and Diox-G.

  • Figure 3

    Capillary shrinkage of the r-GO hydrogel during solvent evaporation. (a) Schematic of the r-GO hydrogel capillary shrinkage process; (b) capillary force exerted on the r-GO sheets during solvent evaporation.

  • Figure 4

    Characterizations of the r-GO monoliths obtained in solvents with different surface tensions. (a) Photos of the r-GO monoliths after solvent evaporation; (b) N2 adsorption/desorption isotherms of the desolvated r-GO monoliths; (c) relationship between the BET surface area and solvent surface tension; (d) bulk density and cumulative pore volume of the desolvated r-GO monoliths as a function of solvent surface tension; (e) the EtOH-G monolith can be further densified to EtOH-HPGM by second drying after immersion in water. It has similar isotherms to HPGM.

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