Coexistence of anodic and cathodic reactions at the scale of a single microbial electrode elucidated by coupling experimental, analytical and numerical approaches

Abstract

Due to the complex biogeochemistry of marine sedimentary systems, the burial depth of sedimentary electrodes significantly influences their bioelectrochemical activity. This study investigates the impact of burial conditions on sedimentary microbial electrodes in oxic and suboxic zones of reconstructed sedimentary systems was investigated. Carbon-felt electrodes were deployed in laboratory reactors filled with fresh marine sediments and seawater under three different exposure conditions. The results showed that the placement of electrodes, whether in sediments or in seawater, profoundly affected both the electrical current (anodic or cathodic) and the microbial communities colonizing the electrode biofilm. Electrodes placement in the transition zone between the oxic and suboxic zones led to the formation of microbial electrodes with hybrid bioelectrochemical properties. Analytical and numerical models were developed to calculate the ratio of anodic and cathodic surfaces operating at the scale of these sedimentary microbial electrodes.