Electron Transfer of <i>Shewanella oneidensis</i> MR-1 at Clay-Modified ITO Electrode

Abstract

The electrode material is an important aspect for the efficiency and costs in the microbial fuel cells (MFCs). Enhancing of current production and bacteria attachment to the electrode are essential goals for developing the performance of MFCs. In this study, the role of the structural iron present in clays in enhancing the electron transfer of Shewanella oneidensis MR-1 was investigated. Two types of clay containing different amounts of iron situated in the octahedral sites were used to modify ITO (indium tin oxide) electrodes, namely nontronite NAu-1, and montmorillonite (Wyoming) SWy-1. Synthetic montmorillonite SYn-1 which is iron-free clay was used for comparison. The interaction between the bacterial cells and the clays was studied by potential-step chronoamperometry, cyclic voltammetry, confocal microscopy, and scanning electron microscopy (SEM). The obtained results showed that the current densities generated upon ITO electrode modification using the NAu-1 and SWy-1 iron-containing clays were 19 and 3 times higher than that produced using the bare ITO electrode. No current density was obtained when utilizing the synthetic montmorillonite SYn-1 clay. SEM and confocal microscopy observations confirmed the increased coverage percentage of the bacterial cells attached to the clay-modified electrodes compared to the bare ITO.