Fabrication of porous carbon structures for biological fuel cells

Abstract

Biofuel cells demand three-dimensional, “high” surface area electrodes with “high” electrical conductivity and structural integrity. The aim of this project is to design and fabricate porous carbon structures as electrodes for enzyme and microbe immobilisation in biofuel cells. These electrodes should have homogeneous pore size distributions, “high” electrical conductivity, “good” mechanical strength and a suitable surface for enzyme and microbe immobilisation. Various routes have been introduced to produce porous carbon electrodes with different ranges of pore sizes. In the case of microbial fuel cells where the pore sizes need to be in the micrometric ranges, a foaming method was adopted. To develop porous carbon electrodes with pore sizes in the nanometre ranges, a templating method was used. Highly ordered hierarchical mesoporous and macroporous carbon structures were obtained using the templating method. Ultimately, a polymer blend technique was developed to produce porous carbon electrodes in large-scales. Porous carbons prepared by this method composed of pores in the micrometric ranges and nanometre pores on the walls of the electrodes’ structures. Various methods to improve mechanical strength and electrical conductivity of the fabricated electrodes were examined. Successive impregnations of the samples in a resin improved the strength and the conductivity of the samples. Moreover, to increase the electrical conductivity of the electrodes, catalytic graphitisation was tested and different graphitic components were produced. The graphitised carbons exhibited electrical conductivities of up to fifty times larger than those obtained from the non-graphitised samples. Electrochemical behaviour of the amorphous and the graphitic carbon electrodes was investigated and it was found that the fabricated electrodes were electrochemically active.