Bifunctional electrode materials: Enhancing microbial fuel cell efficiency with 3D hierarchical porous Fe₃O₄/Fe-N-C...

The rational development of high-performance anode and cathode electrodes for microbial fuel cells (MFCs) is crucial for enhancing MFC performance. However, complex synthesis methods and single-performance electrode materials hinder their large-scale implementation. Here, three-dimensional hierarchical porous (3DHP) Fe₃O₄/Fe-N-C composites were prepared via the hard template method. Notably, Fe₃O₄/Fe-N-C-0.04-600 demonstrated uniformly dispersed Fe₃O₄ nanoparticles and abundant Fe-N_x and pyridinic nitrogen, showing excellent catalytic performance for oxygen reduction reaction (ORR) with a half-wave potential (E_1/2) of 0.74 V (vs. RHE), surpassing Pt/C (0.66 V vs. RHE). Moreover, Fe₃O₄/Fe-N-C-0.04-600 demonstrated favorable biocompatibility as an anode material, enhancing anode biomass and extracellular electron transfer efficiency. Sequencing results confirmed its promotion of electrophilic microorganisms in the anode biofilm. MFCs employing Fe₃O₄/Fe-N-C-0.04-600 as both anode and cathode materials achieved a maximum power density of 831.8 ± 27.7 mW m^-2, enduring operation for 38 days. This study presents a novel approach for rational MFC design, emphasizing bifunctional materials capable of serving as anode materials for microorganism growth and as cathode catalysts for ORR catalysis.