Stainless steel is a promising electrode material for anodes of microbial fuel cells

The abilities of carbon cloth, graphite plate and stainless steel to form microbial anodes were compared under identical conditions. Each electrode was polarised at -0.2 V vs. SCE in soil leachate and fed by successive additions of 20 mM acetate. Under these conditions, the maximum current densities provided were on average 33.7 A m(-2) for carbon cloth, 20.6 A m(-2) for stainless steel, and 9.5 A m(-2) for flat graphite. The high current density obtained with carbon cloth was obviously influenced by the three-dimensional electrode structure. Nevertheless, a fair comparison between flat electrodes demonstrated the great interest of stainless steel. The comparison was even more in favour of stainless steel at higher potential values. At +0.1 V vs. SCE stainless steel provided up to 35 A m(-2), while graphite did not exceed 11 A m(-2). This was the first demonstration that stainless steel offers a very promising ability to form microbial anodes. The surface topography of the stainless steel did not significantly affect the current provided. Analysis of the voltammetry curves allowed two groups of electrode materials to be distinguished by their kinetics. The division into two well-defined kinetics groups proved to be appropriate for a wide range of microbial anodes described in the literature.