Tin Oxide/Vertically Aligned Graphene Hybrid Electrodes Prepared by Sonication-Assisted Sequential Chemical Bath Deposition for High-Performance Supercapacitors

Hybrid electrodes comprising metal oxides and vertically aligned graphene (VAG) are promising for high-performance supercapacitor applications because they enhance the synergistic effect owing to the large contact area between the two constituent materials. However, it is difficult to form metal oxides (MOs) up to the inner surface of a VAG electrode with a narrow inlet using conventional synthesis methods. Herein, we report a facile approach to fabricate SnO2 nanoparticle-decorated VAG electrodes (SnO2@ VAG) with excellent areal capacitance and cyclic stability using sonicationassisted sequential chemical bath deposition (S-SCBD). The sonication treatment during the MO decoration process induced a cavitation effect at the narrow inlet of the VAG electrode, allowing the precursor solution to reach the inside of the VAG surface. Furthermore, the sonication treatment promoted MO nucleation on the entire VAG surface. Thus, the SnO2 nanoparticles uniformly covered the entire electrode surface after the S-SCBD process. SnO2@VAG exhibited an outstanding areal capacitance (4.40 F cm-2) up to 58% higher than that of VAG electrodes. The symmetric supercapacitor with SnO2@VAG electrodes showed an excellent areal capacitance (2.13 F cm-2) and a cyclic stability of 90% after 2000 cycles. These results suggest a new avenue for sonication-assisted fabrication of hybrid electrodes in the field of energy storage.