Self-assembled reduced graphene hydrogels by facile chemical reduction using acetaldehyde oxime for electrode materials in supercapacitors

Abstract

Self-assembled three-dimensional (3D) reduced graphene hydrogels (RGHs) were fabricated by the facile chemical reduction of a graphene oxide (GO) dispersion with ammonia using acetaldehyde oxime as reducing and doping agent. The chemical reduction of GO was confirmed by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy. The hierarchical porosity and structures of the resulting RGHs can be demonstrated by field emission scanning electron microscopy (FESEM) and N₂ sorption experiments. Benefiting from the developed porosity with micro-meso hierarchical pore texture, the specific capacitance of RGHs exhibited high specific capacitances of 230.4, 155.3, 234.2, 155.1 and 191.8 F g⁻¹ at 0.3 A g⁻¹ for RGHs-1, RGHs-2, RGHs-5, RGHs-10 and RGHs-15 in 6 M KOH electrolyte, respectively. More importantly, the RGHs maintained high capacitances of 167.1, 110.4, 142.3, 106.9 and 142.3 F g⁻¹ (the retention rates are 72.5, 71.1, 60.8, 68.9 and 74.2% for RGHs-1, RGHs-2, RGHs-5, RGHs-10 and RGHs-15) at a very high current density of 20 A g⁻¹, indicating good electrochemical stability and a high degree of reversibility in the repetitive charge/discharge cycling test.