Insights into the electrochemical capacitor performance of transition metal-vertical graphene nanosheet hybrid electrodes

• Published in: Physical chemistry chemical physics : PCCP Vol. 21; no. 45; pp. 25196 - 2525
• Main Authors: Sahoo, Gopinath, Polaki, S. R, Anees, P, Ghosh, Subrata, Dhara, Sandip, Kamruddin, M
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 2019
• Subjects: Charge transfer; Copper; Electrical resistivity; Electrode materials; Electrodes; Gold; Graphene; Hybrid structures; Ion currents; Nanoparticles; Nanosheets; Nickel; Silver; Storage capacity; Supercapacitors; Transition metals
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c9cp05656d

Vertical graphene nanosheets (VGN) are envisioned as supercapacitor (SC) electrode materials due to their distinct geometry and remarkable properties. Of late, the hybrid structures of graphene-transition metal (TM) or oxides were found to exhibit enhanced charge storage capacity. Herein, we report the charge storage performance of VGN-transition metal nanoparticle (Au, Ag, Cu, and Ni) hybrid electrodes. Amongst them, Ni-decorated VGN exhibited the highest enhancement, up to 3.04 mF cm −2 (121.6 F g −1 ) compared to 0.16 mF cm −2 (6.4 F g −1 ) for as-grown VGN. Further, this was corroborated by the improved electrical as well as ionic conductivity of the metal-decorated VGN structures. Additionally, the presence of metal-oxygen-carbon bonding ensured a contribution of pseudocapacitance. Ab initio calculations elucidated the extent as well as the nature of charge ( e − ) transfer in TM nanoparticle-VGN hybrid structures. These findings are well corroborated with the charge storage performance. A combined effect from charge transfer and pseudocapacitance on the charge storage performance of TM nanoparticle-VGN hybrid electrodes is demonstrated. A symmetric coin-cell supercapacitor device using Ni/VGN electrodes was fabricated and the sustained performance tested over 10 000 charge-discharge cycles. The enhanced electrochemical capacitance of the transition metal-vertical graphene nanosheet hybrid electrodes are correlated with the increase in charge transfer supported ab initio DFT calculations and increase in electrical conductivity.