Electrostatic self-assembly of hierarchical porous carbon microparticles

Abstract

Hierarchical porous carbon microparticles (HPCMs) are produced by milling and sieving porous monolithic carbon, which was obtained by carbonization of a resorcinol-formaldehyde gel in the presence of surfactant as a pore stabilizer. The obtained HPCMs has a surface area of 536 m2 g-1 and maximum specific capacitance and areal capacitance, measured at slow scan rates, of 194 F g-1 and 152 mF cm-2 respectively. Moreover, the carbon surface remains accessible at 100 mV s-1 with large values of specific capacitance (154 F g-1) and areal capacitance (121 mF cm-2), making the material suitable for fast supercapacitors. The HPCMs are then built into electrostatic self-assembled (ESA) adsorbed layers by sequential immersion of a planar electrode in HPCMs dispersions and a cationic polyelectrolyte. Using soluble redox molecules, it is possible to detect the finite (inside the pores) and semi-infinite (outer surface) diffusion of redox species. The specific capacitance of the HPCMs could be increased up to 5 times (to ca. 900 F g-1 in acid media) by adsorption of naphthoquinone molecules on the carbon surface. Using the ESA process, it is possible to build a layer with three different quinones in a single electrode. The specific capacitance of those layers is more than 4 times higher and maintained nearly constant in a wide range of potential.