Building Self-Assembled Multilayers Of Nanoporous Carbon Microparticles

JUAN M. BALACH; N. GUSTAVO COTELLA; DIEGO F. ACEVEDO; C. A. BARBERO

Santiago, Chile

Congreso; 10th International Conference on Frontiers of Polymers and Advanced Materials; 2009

Nanoporous carbon, obtained by carbonization of porous resorcinol-formaldehyde (RF) resins, are useful materials for supecapacitors due to their high specifica capacitance (> 100 F/g). However, monolithic carbon presents a slow response due to the length of the pores, related with the size of the material. Two ways to overcome the problem imply inserting micrometric sized pores in the monoliths or using microparticles, where the length of the pores is limited by the size of the particles. To build supercapacitor electrodes, the particles have to be linked among in some way. In the present communication, the layer-by-layer self assembly of porous carbon microparticles is described. The particles are made by three different methods: i) milling and sieving a monolithic porous carbon; ii) shaping the particles with microemulsions; iii) controlling the nucleation and growth of the RF gel. The microparticles are assembled on ITO or GC electrodes using a cationic polylelectrolyte (PDAMAC) as counterpart. The measurement of capacitance, using cyclic voltammetry data, shows that the amount of microparticles increases with self assembly steps. Using a soluble redox probe, it can be shown that outer surface of the particles behave as a semi-infinite diffusion system while the inner pore surface behave as a confined redox system. The specific capacitance can be further increased by adsorption of redox couples on the pore surface. By appropriate choice of the redox molecules adsorbed, the capacitamce could be made almost independent on the electrode potential.