Novel g-C3N4 assisted metal organic frameworks derived high efficiency oxygen reduction catalyst in microbial fuel cells

Abstract

The usage of efficient electrocatalyst in an appropriate way can significantly improve the oxygen reduction performance of microbial fuel cells (MFCs) cathode, which may accelerate its commercial application. In this work, isoreticular metal organic framework-3 (IRMOF-3) that modified with g-C3N4 and pyrolyzed at 850 °C (IR/CN-x%), exhibits a superior catalytic activity in alkaline electrolytes for oxygen reduction reaction (ORR). At high temperatures, after zinc evaporation, IRMOF-3 converts to a metal-free carbon skeleton that has large specific surface area. As a nitrogen source and supporting template, g-C3N4 introduces more activated nitrogen, and forms a new metal-free hierarchically porous nitrogen-doped carbon structure. As-synthesized IR/CN-50% as cathode catalyst displays a half-wave potential of 0.89 V (vs. RHE) and limit current density of 6.35 mA cm−2 in 0.1 M KOH, which is superior to commercial Pt/C (0.86 V@5.51 mA cm−2). Furthermore, IR/CN-50% shows approximately four-electron pathway and a yield of less than 4% hydrogen peroxide. Results from electrochemical tests further confirm IR/CN-50% possesses better durability and higher methanol tolerance than Pt/C. Besides, MFCs modified with IR/CN-50% present maximum power density (1402.8 mW m−3) better than the MFCs equipping with Pt/C catalyst (1292.8 mW m−3), which is a promising alternative electrocatalyst for MFCs.