Three-dimensional hierarchical graphitic carbon encapsulated CoNi alloy/N-doped CNTs/carbon nanofibers as an efficient multifunctional electrocatalyst for high-performance microbial fuel cells

A novel Co/Ni metal-organic framework (MOF)-derived three-dimensional (3D) nanoarchitecture in which graphene carbon-coated CoNi alloy nanoparticles grow on the tips of N-doped carbon nanotubes that are vertically-aligned on carbon nanofibers (Co/Ni@GC/NCNTs/CNFs) is fabricated. The Co/Ni@GC/NCNTs/CNFs electrode has a half-wave oxygen reduction reaction (ORR) potential of 0.80 V, a superior standing stability with 84.8% current retention after 175 000 s. The oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) reach a lower overpotential of 0.395 V and 0.15 V, respectively. Moreover, the resultant sample is an air cathode catalyst in a microbial fuel cell and indicates an utmost power density of 2100 ± 45 mW cm−2, which is much better than that of the Pt/C electrode (1334 ± 61 mW m−2). The density functional theory calculation demonstrates that the designed Co/Ni@GC/NCNTs/CNFs catalyst can remarkably promote OER, ORR, and HER performance.