Novel three-dimensional electrode structures with urchin-like pore canal for high-performance microbial fuel cells

In this work, a kind of urchin-like porous structural gel beads as three-dimensional (3D) packed anode materials were prepared to utilize the chemical coprecipitation method, forming the reduced graphene/chitosan/Fe 3 O 4 (rGO/CHI/Fe 3 O 4 ) gel beads (GFe100). The average diameter of Fe 3 O 4 nanoparticles in the gel beads was about 13 nm, distributing uniformly in GFe100 gel beads in situ. Fe 3 O 4 nanoparticles formed in the material-preparation process had a significant pore-creating function to form urchin-like pore canals with the help of the micro-reactor. The average size of these canals was 13.55 μm, which could enhance more functional microbes in the gel beads to strengthen the biocompatibility and extracellular electron transfer (EET) of anode electrodes. The maximum output voltage and power density of GFe100 was 759 mV and 17.823 W·m - 3, which was 2.3 times (327 mV) and 23.21 times (0.768 W m - 3 ) higher than that of GFe0 prepared without any addition of Fe 2+, respectively. The significant electricity generation performance of GFe100 was mainly attributed to the urchin-like canal structure. Exoelectrogens possessed the macropore structure for the controlled diffusion process and extracellular metabolic products occupied the micropore and mesopore structure donating for the surface reactant process. This work suggested that three-dimensional gel beads filled into the anode chamber might be the potential for long-term MFC practice application with a high electricity generation performance.