Cellular scaffolds based on multiwalled carbon nanotubes interpenetrating conductive metal-organic frameworks as efficient eelectrocatalysts in microbial fuel cells

Sluggish kinetics of the cathodic oxygen reduction reaction (ORR) is one of the major challenges hindering the development of microbial fuel cells (MFCs). In this work, a three-dimensional (3D) cellular scaffolds structure is fabricated by in-situ growth of conductive Ni/Co-catecholate bimetal metal-organic frameworks (MOFs) on multiwalled carbon nanotubes (NiCo-CAT/MWCNTs). Such specific structure successfully achieves favorable electronic channels and fast charge-transfer capacity and displays an ultra-low ohmic internal resistance of 7.27 Ω. Meanwhile, NiCo-CAT/MWCNTs exhibit a superior ORR half-wave potential (−0.442V vs. Hg/HgCl2), onset potential (−0.064V vs. Hg/HgCl2) and high limiting current density (8.25 mA cm−2), which exceed that of commercial Pt/C. In the MFC with the NiCo-CAT/MWCNTs cathode, the maximum power density is 130% higher than Pt/C cathode. The outstanding performance of MFC is mainly due to the optimized electronic structure and fully exposure of the Ni, Co synergistic catalytic active sites. In addition, oxygen permeability is greatly improved by electrospun polyvinylidene fluoride (PVDF) air diffusion layer replacing the traditional carbon cloth cathode. This study provides a new perspective for MFCs performance improvement by ORR conductive MOFs catalysts.