Single-Walled Carbon Nanotube-Clostridium Ljungdahlii hybrid for Carbon Dioxide Fixation to Value-Added Chemicals

Abstract

Direct electricity-powdered production of value-added carbon organic compoundsfrom CO2 and H2O, a process that mimics natural Wood–Ljungdahl pathway (WLP), is of fundamental and practical interestfor renewable energy applications. The process depends on electrotrophy, the ability of some microorganisms to use electrons derived from an electrode as the sole energy source to reduce carbon dioxide. In this work, an acetogenic microorganism Clostridium ljungdahliiis immobilizedon carbon felt (CF) andhighly enriched semiconducting single-walled carbon nanotube (SWCNT) scaffolds under different conditions (physical soaking and growth under electrochemical bias). As a proof of principle, we demonstrate that this conductive carbon-bacteria system can utilize electrical current to fix CO2 under to multiple chemical targets, such as acetate and ethanol. The porous structure of the hybrid electrode provides the large surface area needed for high bacteria loading and excellent diffusion kinetics, while the s-SWCNTs appear to facilitate unique modes of bacterial adsorption and strong interfacial interactions. As such, the hybrid system enables low overpotential (η < 200 mV) and high Faradaic efficiency (> 90%). With the SWCNT modification and bacteria electrochemical growth, the hybrid electrode exhibited much higher performance on acetate production due to the enhanced bacteria-electrode interface quality for charge transfer. I will also discuss our efforts to understand the biochemicalpathways and possible underlying charge transfer mechanisms of CO2reduction of this SWCNT-Clostridium ljungdahliisystem. These results suggest a potential route for using SWCNTs to facilitate efficient microbial electrochemical biofilm formation and energy storage, furthering the potential applicability in bioelectrochemical systems.