Novel Efficient Microbial Fuel Cell Anodes Using Activated Carbon Nanofiber Nonwoven

Microbial Fuel Cells (MFCs) are a technology capable of sustainably treating wastewater. In a single chamber design, the anode and cathode, traditionally spatially separated by a semi-permeable membrane, rest in the same chamber, allowing diffusion to occur. Despite the promise MFC technology holds, they have not yet been commercialized due to high costs and low power density limitations. One of the ways to address the latter issue is through the use of better electrode materials. In a previous study, activated carbon nanofibers nonwoven (ACNFN) were introduced as a novel anode material for MFCs, where they were found to perform vastly better compared to traditional anode materials, including carbon cloth and carbon brush.

ACNFN were fabricated by electrospinning a solution of polyacrylonitrile in dimethylformamide. Precursor fibers then underwent stabilization and carbonization. Finally, they were steam activated directly after carbonization to create greater porosity and increase the active surface area.  The objective of this follow-up study was to determine the effect of activation temperature and steam volume delivered on the performance of these anodes.  Three different activation temperatures and steam volumes were chosen and post-fabrication, the materials were characterized for biomass adhesion and electrochemical performance in a single chamber MFC. 

It was found that steam exposure during the activation period (versus only additional heating without steam delivery) increased anode power generation in an MFC. Additionally, anodes that were steam activated at higher temperatures had enhanced biomass adhesion and generated increasingly higher power outputs in single-chamber MFCs. In fact, the anode steam activated at the highest temperature tested outperformed a traditional carbon cloth anode, when measured for current drawn at specific voltages.  Continued exploration of activation parameters can further increase anode efficiency to hopefully create an implementable and scalable fuel cell.