Graphene-based PANI composite coatings with fine-controllable 3D hierarchical structures prepared from bio-inspired photo-/colloidal-lithography technique for flexible supercapacitor application

In this study, various bio-inspired micro-/nano-scaled cylindrical patterns were designed by controlling their width and interspacing over a silicon substrate by using 3D photo/colloidal lithography techniques. The surface morphology and cross-sectional images confirmed the exact fabrication of bio-inspired textures. The as-prepared bio-inspired surface textures were coated with polydimethylsiloxane as a soft negative template and then covered with polyaniline (PANI) to investigate the morphology effect in supercapacitor application. Results showed that the bio-inspired texture with micro-/nano-architectured surface of two different widths and interspacing of 5 µm and 500 nm provided the best PANI capacitance performance of 429 F/g amongst other single and non-patterned (plain) templates with capacitance performances of 364 and 316 F/g, respectively, at 5 mV/s. Moreover, reduced graphene oxide was successfully incorporated into PANI; characterised using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy; and investigated for supercapacitor performance by using the bio-inspired micro/nano-template. A synergistic performance of 614 F/g was observed at 1 A/g with excellent capacitive retention of 85% after 10,000 cycles. Efficient flexibility was also found over long-term cycling without defects in the performance. Thus, these novel bio-inspired electrodes could open the door for developing further portable bio-inspired electronic devices in the future.