Functionalised graphite felt anodes for enhanced power generation in membrane-less soil microbial fuel cells

Abstract

There is a global need for sustainable and clean technologies that can actively contribute to reach the net-zero carbon goal by 2050. In this context, Soil Microbial Fuel Cell (SMFC) technology has a huge potential as an affordable and green energy harvesting source and as a carbon-neutral bioremediation strategy for the treatment of polluted lands. In this work, for the first time, cobalt oxide (Co₃O₄) modified graphite felt (GF) electrodes are explored as the anode material in SMFCs, with the aim of promoting the development of a high-performing electroactive biofilm and, therefore, boosting electrogenesis. First, cobalt hydoxide salt are hydrothermally distributed onto the graphite felt electrodes, then Co₃O₄ nanoflowers are obtained by calcination. The resulting Co₃O₄–GF electrodes show lower hydrophobicity and higher conductivity than GF, however, when Co₃O₄–GF is tested as the anode of a membrane-less, air-cathode SMFC device, after an initial boost in power performance, the activity decays with time, probably due to Co₃O₄ leaching. To overcome this issue, Co₃O₄ –GF electrodes are interweaved with polyaniline (PANI), resulting in PANI–Co₃O₄–GF, for a much more stable SMFC system, which generates a peak power density of 70 mW m⁻² at a current density of 143 mA m⁻². This value of power density is nearly three times greater than the power generated by the same SMFC system with a plain GF anode. The interweaving of PANI onto the Co₃O₄–GF electrode leads to a porous structure that, while providing stability to the electrode over prolonged periods of operation, also favours microbial attachment. Overall, these results provide exciting perspectives on the development of composite carbon-based anode materials for high performing soil microbial fuel cells, thus inspiring future trends in the field.