Alfalfa Leaf-Derived Porous Heteroatom-Doped Carbon Materials as Efficient Cathodic Catalysts in Microbial Fuel Cells

Heteroatom-doped lamellar-structured carbon with a high surface area synthesized from alfalfa leaves is utilized as a cathode catalyst in this study to improve the power output of microbial fuel cells (MFCs). Different chemical activation agents are used to treat alfalfa leaf-derived carbon (ALC). It is found that chemical activation agents substantially affect the catalytic activities of the alfalfa leaf-derived carbon materials in the power output of MFCs and the oxygen reduction reaction (ORR). ALC materials activated by KOH (ALC-K) exhibit the best electrochemical activity compared with those of materials activated by FeCl3 (ALC-Fe) or ZnCl2 (ALC-Zn). A high limiting current density and excellent long-term stability can be seen with ALC-K as the cathode catalyst, which gives superior results to those of Pt/C. Moreover, a maximum power density of approximately 1328.9 mW/m2 is obtained from an MFC equipped with an ALC-K cathode, offering performance characteristics comparable to those of a Pt/C cathode as well. This work demonstrates a new method for the production of inexpensive nanostructured carbon materials derived from natural resources that exhibit high performance in MFCs.