Extremely low fractions of graphene oxide in carbon foam prepared by a spin-coating method as freestanding supercapacitor electrodes

Three-dimensional carbon foam (CF) has been widely employed as a conductive framework for preparing self-supporting supercapacitor electrodes. Herein, based on the spin-drying mechanism of washing machine, a spin-coating method is developed to prepare carbon foam@graphene oxide (CF@GO) composites, in which a special centrifugation tube containing a macroporous shelf is used to separate the foam block and residual GO suspension during centrifugation. The GO fractions in CF@GO composites are controlled easily by tuning the spin speeds. As freestanding electrodes in two-electrode supercapacitors, the CF@GO-4500 (4500 rpm, 1.2 wt% GO) and CF@RGO-1000 electrodes (1000 rpm, 3.2 wt% GO) exhibit the specific capacitances of 159 Fg⁻¹ (258 mF cm⁻²) and 180 Fg⁻¹ (297 mF cm⁻²) at 0.5 Ag⁻¹, respectively, which are much higher than those of CF and CF@GO-4 or CF@RGO-4 sample (15.3 wt% GO) prepared by a conventional soaking–freeze-drying method. The results show that a few GO/RGO sheets loading in CF framework exhibit an enhanced electrochemical performance in supercapacitor, rather than filling much GO/RGO.