Iron-involved zeolitic imidazolate framework-67 derived Co/Fe-NC as enhanced ORR catalyst in air–cathode microbial fuel cell

Abstract

Microbial fuel cell (MFC), simultaneously degrading organic pollutants and harvesting electricity, suffers from a sluggish oxygen reduction reaction (ORR) on cathode. The catalysts for Pt substitution are crucial to enhance the ORR performance and power output. Thus, a Co and Fe co-doped carbon derived from ZIF-67 (Co/Fe-NC) is prepared, which is proved to have excellent electrochemical properties. When the catalyst Co/Fe-NC is equipped in microbial fuel cell, the maximum power density of 1831 ± 57 mW m−2 is achieved, which is 13.5 % higher than that of Fe@Co-NC and 49.3 % higher than that of Co-NC. Moreover, the electrochemical tests show that Co/Fe-NC has a smaller charge transfer resistance and a higher exchange current density, which implies the faster kinetics of ORR. The enhanced performance of Co/Fe-NC can be attributed to the rougher rhombic dodecahedral interface, larger surface area, various types of nitrogen species, critical roles of cobalt and iron species, both high graphitization and defects. All these characteristics are responsible for the significant increase in ORR activity and power output. This work designs and compares different catalysts derived from iron-involved ZIF-67, and demonstrates a superior ORR electrocatalyst of Co/Fe-NC, which can be a potential alternative to Pt in the MFC practical application.