Tailoring Surface Properties of Electrodes for Synchronous Enhanced Extracellular Electron Transfer and Enriched Exoelectrogens in Microbial Fuel Cells

Abstract

An extracellular electron transfer (EET) process between an electroactive biofilm and an electrode is a crucial step for the performance of microbial fuel cells (MFCs), which is highly related to the enrichment of exoelectrogens and the electrocatalytic activity of the electrode. Herein, an efficient N- and Fe-abundant carbon cloth (CC) electrode with the comodification of iron porphyrin (FePor) and polyquaternium-7 (PQ) was synthesized using a facile solvent evaporation and immersion method and developed as an anode (named FePor-PQ) in MFCs. The surface structural characterizations confirmed the successful introduction of N and Fe atoms, whereas FePor-PQ achieved the N content of 9.59 at %, which may offer various active sites for EET. The introduction of PQ contributed to improving the surface hydrophilicity, providing the composite electrode good biocompatibility for bacterial attachment and colonization as well as substrate diffusion. Based on the advantages, the MFC with the FePor-PQ anode produced a maximum power density of 2165.7 mW m–2, strikingly higher than those of CC (1124.0 mW m–2), PQ (1668.8 mW m–2), and FePor (1978.9 mW m–2). Furthermore, with the EET mediated by the binding of flavins and c-type cytochromes on the outer membrane was enhanced prominently, the typical exoelectrogen Geobacter was enriched up to 55.84% in the FePor-PQ anode biofilm. This work reveals a synergistic effect from heteroatom coating and surface properties tailoring to boost both the EET efficiency and exoelectrogen enrichment for enhancing MFC performance, which also provides valuable insights for designing electrodes in other bio-electrochemical systems.

3D Hierarchical Co8FeS8-FeCo2O4/N-CNTs@CF with an Enhanced Microorganisms–Anode Interface for Improving Microbial Fuel Cell Performance

“…In general, the peak current ( i ) is composed of the fast kinetic process ( k 1 ν) and show kinetic process ( k 2 ν 0.5 ) in eq : in which i is the peak current at a fixed scan rate and k 1 and k 2 are constants. Both sides of eq are multiplied by ν 0.5 at the same time in eq : When plotting iv –0.5 versus v 0.5 , k 1 and k 2 can be determined . Then the contribution ratio of the fast and slow kinetics process can be analyzed.…”

“…When plotting iv −0.5 versus v 0.5 , k 1 and k 2 can be determined. 14 Then the contribution ratio of the fast and slow kinetics process can be analyzed. The fast and slow kinetics process contributions to the anodic peak current were shown in Figure 6e.…”

“…Microbial fuel cells (MFCs) are ecofriendly bioenergy harvesting and wastewater treatment technologies. − The anode in MFCs provides bacterial colonization sites for biofilm attachment and electron transfer paths to receive the metabolized electrons . The crystal structures of outer membrane c-type cytochromes (OMCs) and pili analyzed by cryo-TEM unveiled that the electron transmembrane and extracellular electron-transfer (EET) processes are mainly determined by the interface between OMCs or flavin–OMCs complex and anode. − It is challenging to obtain high MFCs power density without the formation of active biofilm with enriched exoelectrogens and the fast electronic/ionic transfer rates. , Thus, the question of how to strengthen the microorganism–anode interface to simultaneously favor the bacterial attachment and promote EET process is a great challenge. − …”

“…8−12 It is challenging to obtain high MFCs power density without the formation of active biofilm with enriched exoelectrogens and the fast electronic/ionic transfer rates. 13,14 Thus, the question of how to strengthen the microorganism−anode interface to simultaneously favor the bacterial attachment and promote EET process is a great challenge. 15−17 Commercial carbonaceous supports (carbon cloth, felt, paper, and brush) have been widely used as anodes for MFCs.…”

Microbial-Inspired Surface Patterning for Selective Bacterial Actions for Enhanced Performance in Microbial Fuel Cells

“…Bio-electrochemical systems (BESs) are devices which contain microorganisms to donate or accept electrons from an electrode. The performance of any BES is affected by many factors, where microbes and anodes play a very crucial role. , The extent of microbial–electrode interaction is the rate-limiting factor that determines the performance of the BES. In regard to enhanced microbial activity and extracellular electron transfer (EET), a desired anode with selective adhesion of microbes and that provides more sites for microbial adhesion and electron transfer is mandatory .…”