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