Boosting Power Density of Microbial Fuel Cells with 3D Nitrogen‐Doped Graphene Aerogel Electrode

Abstract

A 3D nitrogen‐doped graphene aerogel (N‐GA) as an anode material for microbial fuel cells (MFCs) is reported. Electron microscopy images reveal that the N‐GA possesses hierarchical porous structure that allows efficient diffusion of both bacterial cells and electron mediators in the interior space of 3D electrode, and thus, the colonization of bacterial communities. Electrochemical impedance spectroscopic measurements further show that nitrogen doping considerably reduces the charge transfer resistance and internal resistance of GA, which helps to enhance the MFC power density. Importantly, the dual‐chamber milliliter‐scale MFC with N‐GA anode yields an outstanding volumetric power density of 225 ± 12 W m−3 normalized to the total volume of the anodic chamber (750 ± 40 W m−3 normalized to the volume of the anode). These power densities are the highest values report for milliliter‐scale MFCs with similar chamber size (25 mL) under the similar measurement conditions. The 3D N‐GA electrode shows great promise for improving the power generation of MFC devices.

Interpenetrated Bacteria‐Carbon Nanotubes Film for Microbial Fuel Cells

“…Furthermore, it has been reported that charge transfer resistance of MFC is closely related to the efficiency of extracellular electron transport. [1c] The smaller the charge transfer resistance represents the higher the power delivering efficiency that is critical to MFC . Notably, the charge transfer resistances of the bacteria‐CNT composite electrodes [bacteria‐CNT‐1: 1.65 Ω cm −2 (20.72 Ω); bacteria‐CNT‐2: 1.44 Ω cm −2 (18.18 Ω)] are similar and considerably lower than the value obtained from the bacteria‐colonized‐CNT anode [2.65 Ω cm −2 (33.32 Ω)], and significantly lower than the values reported for carbon cloth anodes (>100 Ω cm −2 ) .…”

“…It is anticipated that the power density of an MFC can be enhanced by increasing the number of electrogenic bacteria colonized on the anode, when the bio‐oxidation reaction is not limited by mass transfer (the diffusion of redox species) or charge transport (both direct and indirect extracellular electron transport) . In the past decade, a variety of new anode structures, such as carbon cloth, carbon nanotube (CNT)‐textile, macroporous reduced graphene oxide‐nickel (rGO‐Ni), 3D nitrogen‐doped graphene aerogel, etc. have been developed with a goal of increasing the electrode surface area for bacteria colonization.…”

“…However, increasing the accessible surface area for bacteria in porous structures has been a long‐standing challenge. Most previously reported porous anode structures have large pores between ≈5 to 500 µm to ensure efficient diffusion of micrometer size bacteria (e.g., S. oneidensis MR‐1 is about 2.5 µm in length and 0.5 µm in diameter) and good utilization of the interior surface . Yet, the large pores severely limit the total surface area per unit mass or volume, and thus, the loading number of bacteria.…”

Aerogels: promising nanostructured materials for energy conversion and storage applications

“…Besides, N-doped graphene aerogel was used as an electrode in Li-ion supercapacitor and got a maximum energy density of 70 Wh/Kg with the power density of 200 Wh/Kg with good cycling stability [111]. N-doped graphene aerogel was also used as an anode material for microbial fuel cell and attained a power density of 225 W/m 3 with a high open circuit potential of 0.69 V [112].…”

Successive parabolic interpolation as extremum seeking control for microbial fuel & electrolysis cells

“…Therefore, to make MFCs a competitive renewable technology, a lot of research focuses on the impact of the bioreactor structure, the used materials for the electrodes and the microbial community on the volumetric power density [2]. Recent MFCs achieve volumetric power densities of 225W m −3 , although on a small scale (25ml) and in a wellcontrolled lab environment [3].…”