Sodium cobalt oxide as a non-platinum cathode catalyst for microbial fuel cells

Abstract

Platinum has long been the best catalyst for microbial fuel cells (MFCs), but its high cost and limited resources have prompted us to find more abundant and less expensive alternatives. In this study, the potential of a sodium cobalt oxide (NaCo2O4) as a cathode catalyst for MFCs was investigated. A catalyst ink, prepared by mixing 50 wt% of Ketjenblack with NaCo2O4, was applied (4 mg cm−2 as NaCo2O4) to a waterproofed carbon to make an air-cathode. The activity of oxygen reduction reaction of the cathode was measured by the linear sweep voltammetry technique. The NaCo2O4 cathode exhibited about 50–90% current density of a cathode made with platinum-on-carbon catalyst at the same electric potential. This NaCo2O4 cathode was fit into a MFC, which was then run to treat synthetic wastewater. It exhibited the current density of about 3 A m−2. No decline in the current density or performance was observed over several days of operation. It exhibited the highest power density of 0.6 W m−2. Optimization of the cathode preparation conditions may further improve the cathode performance. This study suggests a promising potential of NaCo2O4 as a cathode catalyst for MFCs. Keywords: Microbial fuel cells, Air-cathode, Non-platinum catalyst, Oxygen reduction reaction, Voltammetry