The quest for supercapacitors that can hold both high energy and power density is of increasing significance as the need for green and reliable energy storage devices grows, for both large-scale and integrated systems. While supercapacitors for integrated technologies require a solid-state approach, gel-based electrolytes are generally not as efficient as their aqueous counterparts. Here we demonstrate a strategy to enhance the performance of quasi-solid-state supercapacitors made by graphitized silicon carbide on silicon electrodes and polyvinyl alcohol (PVA) + H2SO4 gel electrolyte. The electrochemical characterization shows an increase of the specific capacitance of the cell up to 3-fold resulting from a simple agent-free, in-situ, electrochemical treatment leading to functionalization of the graphitic electrodes. The functionalization of the electrodes simultaneously enables redox reactions, without adding any redox agent, and increases the double layer contribution to the overall capacitance. The strategy and insights offered by this work hold great promise for improving quasi-solid-state, miniaturized on-chip energy storage systems, which are compatible with silicon electronics.