Nano-enhanced microbial electrochemical cells for energy recovery from dilute organic matter
- Microbial electrochemical cells (MECs) show great potential for energy recovery from dilute reservoirs of organic matter, such as domestic wastewater, marine sediment, waste biomass and methane hydrate. In order to enhance the performance of the MECs, this study focuses on applying materials science and nanotechnology to develop new MEC electrodes and configurations. First, a three-dimensional (3D) microbial bio-electrode design has been proposed and realized by conformally coating carbon nanotubes (CNTs) or graphene on a macroscale porous substrate, such as textile or sponge. Such composite bio-electrodes provide a two-scale porous structure, a macroscale porous textile or sponge providing an open 3D space accessible for microbial growth and a microscale porous CNT or graphene layer showing strong interactions with the microbial biofilms. Compared with a widely used commercial carbon cloth anode, our composite bio-electrodes achieve significantly improved performance in maximum current density (3-fold), maximum power density (2-fold), energy recovery efficiency (3-fold), and long term stability as anodes in microbial fuel cells (MFCs). At the same time, the capital cost is at least one order of magnitude less. The next, a new oxygen reduction cathode for aqueous MFCs has been designed and obtained by electrochemically depositing Pt nanoparticles on a macroscale porous CNT-coated textile electrode. For this CNT-textile-Pt cathode, the electrochemical deposition method guarantees the electronic pathway to all of the catalyst, while the open and macroscale porous CNT-textile provides high specific catalyst-electrolyte interfacial surface area. The CNT-textile-Pt cathode shows two orders higher surface area utilization efficiency than that of a commercial carbon cloth cathode with Pt painting. An MFC equipped with the CNT-textile-Pt cathode achieves a higher power density (2-fold) with a lower Pt loading (20%). Last, a new MEC, referred as a "microbial battery (MB)", has been developed. The key difference of MBs to MFCs is the use of solid-state cathodes to replace the oxygen gas cathodes. The MBs overcome the major drawbacks of MFCs: voltage losses at oxygen cathodes and introduction of oxygen into the anode compartment. A bench-scale MB with silver-oxide as the solid-state electrode achieves an efficiency of electrical energy conversion of 49% based on the combustion enthalpy of the organic matter consumed or 44% based on the organic matter added. Electrochemical re-oxidation of the solid-state electrode decreases net efficiency to about 30%, but this (un-optimized) net efficiency of energy recovery is still about an order of magnitude higher than the energy recovery efficiencies achieved with MFCs, and comparable to methane fermentation with combined heat and power.
|Type of resource
|electronic; electronic resource; remote
|1 online resource.
|Stanford University, Department of Civil and Environmental Engineering.
|Cui, Yi, 1976-
|Cui, Yi, 1976-
|McCarty, Perry L
|McCarty, Perry L
|Statement of responsibility
|Submitted to the Department of Civil and Environmental Engineering.
|Thesis (Ph.D.)--Stanford University, 2014.
- © 2014 by Xing Xie
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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