RuO2-coated vertical graphene hybrid electrodes for high-performance
solid-state supercapacitors
Zhao Jun Han1,*, Shafique Pineda1, Adrian T. Murdock1, Dong Han Seo1, Kostya (Ken)
Ostrikov1,2, Avi Bendavid1
1CSIRO Manufacturing, 36 Bradfield Road, Lindfield, NSW 2070, Australia. 2School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology,
Fig. S1. Growth of VG with and without the Ar pre-treatment on a SiO2/Si substrate. (a) Top-
view and (b) cross-sectional view of VG grown without Ar pre-treatment. (c) The enlarged
view of the squared area in (b). (d) Top-view and (e) cross-sectional view of VG grown with
Ar pre-treatment. (f) The enlarged view of the squared area in (e). It can be seen that with the
Ar pre-treatment, a base layer with a higher density of VG was induced. This base layer
increased the adhesion between VG and the Ni growth substrate. Scale bars in (a, d) are 200
nm and in (b, c, e, f) are 1 µm.
Fig. S2. (a) N2 adsorption-desorption isotherm at 77 K; (b) Pore size distribution calculated
based on the Density Functional Theory (DFT) model. Prior to the measurement, the VG
powder was outgassed at 300 °C overnight. A type II isotherm where the adsorbed volume
increased at low relative pressure due to the monolayer formation. As the relative pressure
approached unity an abrupt rise indicated the capillary condensation. A type H3 hysteresis was
observed in the desorption curve. This hysteresis indicated the non-rigid aggregate of plate-like
particles, in good agreement with the structure of VG nanosheets. The surface area of VG is
~400 m2/g and the pore size distribution based on the DFT model showed a relatively high
portion of pore radius at <2 nm.
Fig. S3. (a) TEM image of pure VG showing a structure with ~10 layers of graphene. (b) Low-
and (c) high-resolution TEM images of discrete RuO2 nanoparticles deposited on both edge
and basal plane of VG nanosheets. The nominal thickness of RuO2 in (b) & (c) was further
reduced to 2 nm to better characterize the lattice structure of RuO2.
Fig. S4. Raman spectra of pristine VG and RuO2/VG.
Fig. S5. CV curve of Ni substrate in contact with the PVA/H3PO4 electrolyte, obtained at a
scan rate of 100 mV/s. It is clear that Ni was unstable in the acidic gel electrolyte.
Fig. S6. (a) Photo and structure of coin cell assembled with two RuO2/VG electrodes, a
separator, and aqueous 1 M Na2SO4 electrolyte. (b) CV curves of the coin cell at scan rates of
5, 10, 20, 50 and 100 mV/s. (c) Discharge curves of the coin cell at current densities of 0.2,
0.5, 1, 1.5, and 2 mA/cm2. (d) The area capacitance Ca plotted as function of the scan rate.
Fig. S7. (a) Ca, (b) CV and (c) Cs plots of solid-state RuO2/VG measured at different RuO2 thickness.
Fig. S8. Rate capability of 10 nm RuO2/VG. A high capacitance retention of 75.6% was
observed when the scan rate was increased from 5 to 200 mV/s.
Fig. S9. (a) Photo of a large size VG sample (6 x 6 cm2) produced in PECVD. (b) Photo of a
stacked two-electrode symmetric cell assembled by two identical RuO2/VG electrodes with the
gel electrolyte. (c) The stacked symmetric cell conformed to a cylindrical vial showing the
flexibility. (d) CV curves of the stacked symmetric cell at scan rates of 5, 10, 20, 50, and 100
mV/s.
Fig. S10. (a) CV curves of solid-state RuO2/VG supercapacitors tested at no bending, bending
radius of 9 mm, and bending radius of 5 mm; (b) Plot of capacitance change at different bending
conditions.
Fig. S11. CV curves of a coin cell assembled by two symmetric 250 nm RuO2/VG electrodes
with gel electrolyte at scan rates of 20, 50, 100, and 200 mV/s. Ca of this device was 28 mF/cm2
at a scan rate of 100 mV/s.
Table S1. Fitting results of the EIS spectra to the equivalent circuit model shown in the inset
of Fig. 5e, where RS is the equivalent series resistance (ESR), RCT is the charge transfer
resistance, M is the restricted diffusion element and CPE is the constant phase element. The
impedance of M is given by , while CPE is given by 𝑅𝑑 ∗ 𝑐𝑜𝑡ℎ( 𝑡𝑑𝑗2𝜋𝑓)/ 𝑡𝑑𝑗2𝜋𝑓
.1/(𝑄 ∗ (𝑗2𝜋𝑓)𝛼
M CPESample RS (Ω) RCT (Ω)
Rd (Ω) Td (s) Q (F/s1-α) α
Pristine VG 6.0 6.8 11.8 1.6e-3 0.25e-3 0.69
5 nm RuO2/VG 2.5 0.6 7.4e-3 11e-6 2.1e-3 0.67
Table S2. Performance comparison of the current RuO2/VG electrodes with other
supercapacitor electrodes reported in the recent literature.
Electrodes Deposition method of RuO2
Electrolyte Ca or Cs (if Ca is not available)
Stability Reference
RuO2/RGO Solution. High cost.
Aqueous 435 – 497 F/g 98.2% after 1,000 cycles
[1]
RuO2/Carbon QDs
Solution. High cost.
Aqueous 460 – 594 F/g 96.9% after 5,000 cycles
[2]
RuO2/IL-RGO Solution. High cost.
Aqueous 149 F/g 89% – 97% after 1,000 cycles
[3]
RuO2/CNT Solution. High cost.
Aqueous 973 F/g N.A. [4]
Hollow RuO2/CNT
Solution. High cost.
Aqueous 655 – 819 F/g >95% after 1,000 cycles
[5]
RuO2/SWNT Solution. High cost.
Aqueous 8 – 16 mF/cm2 N.A. [6]
RuO2/carbon onion
Solution. High cost.
Gel 205 F/g 94.5% after 4,000 cycles
[7]
RuO2/IL-CMG Solution. High cost.
Gel 175 F/g 95% after 2,000 cycles
[8]
RuO2/stainless steel
Solution. High cost.
Gel 167 – 234 F/g ~70% after 1,000 cycles
[9]
RuO2/PEDOT:PSS
Solution. High cost.
Gel 1.7 mF/cm2 93% after 6,000 cycles
[10]
RuO2/Ti foil Solution. High cost.
Gel ~20 mF/cm2 N.A. [11]
RuO2/CNW Solution. High cost.
Gel 1000 mF/cm2 85% – 90% after 2,000 cycles
[12]
RuO2/porous Au Solution. High cost.
Gel 3250 mF/cm2 90% after 2,000 cycles
[13]
RuO2/TiN Solution-free (ALD).High cost.
Nafion 0.578 mF/cm2 80% after 25,000 cycles
[14]
RuO2/VA FLG Solution-free.Low cost.
Aqueous 20 mF/cm2 70% after 4,000 cycles
[15]
RuO2/VA MWNT
Solution-free.Low cost.
Aqueous 16.94 mF/cm2 90% after 400 cycles
[16]
RuO2 NWs/SWNT
Solution-free (CVD).Low cost.
Gel 138 F/g N.A. [17]
RuO2/VG Solution-free.Low cost.
Gel 15.3 mF/cm2 71% after 10,000 cycles
This work
Supplementary References
1 Kim, J.-Y., Kim, K.-H., Yoon, S.-B., Kim, H.-K., Park, S.-H. & Kim, K.-B. In situ chemical synthesis of ruthenium oxide/reduced graphene oxide nanocomposites for electrochemical capacitor applications. Nanoscale 5, 6804 (2013).
2 Zhu, Y., Ji, X., Pan, C., Sun, Q., Song, W., Fang, L., Chen, Q. & Banks, C. E. A carbon quantum dot decorated RuO2 network: outstanding supercapacitances under ultrafast charge and discharge. Energy Environ. Sci. 6, 3665 (2014).
3 Choi, B. G. & Park, H. S. Controlling size, amount, and crystalline structure of nanoparticles deposited on graphenes for highly efficient energy conversion and storage. ChemSusChem 5, 709 (2012).
5 Wang, P., Xu, Y., Liu, H., Chen, Y., Yang, J. & Tan, Q. Carbon/carbon nanotube-supported RuO2 nanoparticles with a hollow interior as excellent electrode materials for supercapacitors. Nano Energy 15, 116 (2015).
6 Das, R. K., Liu, B., Reynolds, J. R. & Rinzler, A. G. Engineered macroporosity in single-wall carbon nanotube films. Nano Lett. 9, 677 (2009).
7 Muniraj, V. K. A., Kamaja, C. K. & Shelke, M. V. RuO2·nH2O Nanoparticles Anchored on Carbon Nano-onions: An Efficient Electrode for Solid State Flexible Electrochemical Supercapacitor. ACS Sustainable Chem. Eng. 4, 2528 (2016).
8 Choi, B. G., Chang, S.-J., Kang, H.-W., Park, C. P., Kim, H. J., Hong, W. H., Lee, S. & Huh, Y. S. High performance of a solid-state flexible asymmetric supercapacitor based on graphene films. Nanoscale 4, 4983 (2012).
9 Dubal, D. P., Gund, G. S., Holze, R., Jadhav, H. S., Lokhande, C. D. & Park, C.-J. Solution-based binder-free synthetic approach of RuO2 thin films for all solid state supercapacitors. Electrochim. Acta 103, 103 (2013).
10 Zhang, C. J., Higgins, T. M., Park, S.-H., O'Brien, S. E., Long, D., Coleman, J. N. & Nicolosi, V. Highly flexible and transparent solid-state supercapacitors based on RuO2/PEDOT:PSS conductive ultrathin films. Nano Energy 28, 495 (2016).
11 Lian, K. & Tian, Q. Solid asymmetric electrochemical capacitors using proton-conducting polymer electrolytes. Electrochem. Comm. 12, 517 (2010).
12 Dinh, T. M., Achour, A., Vizireanu, S., Dinescu, G., Nistor, L., Armstrong, K., Guay, D. & Pech, D. Hydrous RuO2/carbon nanowalls hierarchical structures for all-solid-state ultrahigh-energy-density micro-supercapacitors. Nano Energy 10, 288 (2014).
13 Ferris, A., Garbarino, S., Guay, D. & Pech, D. 3D RuO2 Microsupercapacitors with Remarkable Areal Energy. Adv. Mater. 27, 6625 (2015).
14 Gnerlich, M., Pomerantseva, E., Gregorczyk, K., Ketchum, D., Rubloff, G. & Ghodssi, R. Solid flexible electrochemical supercapacitor using Tobacco mosaic virus nanostructures and ALD ruthenium oxide. J. Micromech. Microeng. 23, 114014 (2013).
15 Soin, N., Roy, S. S., Mitra, S. K., Thundat, T. & McLaughlin, J. A. Nanocrystalline ruthenium oxide dispersed Few Layered Graphene (FLG) nanoflakes as supercapacitor electrodes. J. Mater. Chem. 22, 14944 (2012).
16 Ye, J.-S., Cui, H. F., Liu, X., Lim, T. M., Zhang, W.-D. & Sheu, F.-S. Preparation and Characterization of Aligned Carbon Nanotube–Ruthenium Oxide Nanocomposites for Supercapacitors. Small 1, 560 (2005).
17 Chen, P., Chen, H., Qiu, J. & Zhou, C. Inkjet Printing of Single-Walled Carbon Nanotube/RuO2 Nanowire Supercapacitors on Cloth Fabrics and Flexible Substrates. Nano Res. 3, 594 (2010).
