Carbon dioxide conversion to C1 - C2 compounds in a microbial electrosynthesis cell with in situ electrodeposition of nickel and iron. (1st July 2021)

• Record Type: Journal Article
• Authors: Gomez Vidales, Abraham; Bruant, Guillaume; Omanovic, Sasha; Tartakovsky, Boris
• Is Part Of: Electrochimica acta. Volume 383(2021)
• Publication Date: 2021-07-01
• Subjects: Bioelectrosynthesis -- Electrodeposition -- Acetogenesis -- Methanogenesis -- CO2 electrolyzer; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2021.138349
• Languages: English
• ISSNs: 0013-4686

Abstract

Highlights: Continuous CH4 bioelectrosynthesis from CO2 demonstrated with 80% or higher Coulombic Efficiency. At pH values below 8 CH4 cathodic off-gas contains up to 85% CH4 . At pH above 8.5, production of acetate and then ethanol (up to 8 g L −1 ) was obtained. Coulombic efficiency remained above 80% 16S sequencing showed proliferation of Clostridium, Methanosaeta, Methanobrevibacter and Methanobacterium spp at the cathode. Abstract: This study demonstrates the continuous conversion of CO2 to methane, acetate, and ethanol in a Microbial Electrosynthesis Cell (MESC) with a carbon felt biocathode. The MESC was inoculated with a mixed anaerobic microbial consortium and operated at a mesophilic temperature of 30 °C. In situ deposition of Ni and Fe was achieved by introducing 0.2 g L −1 of NiSO4 or FeSO4, respectively, into the cathode compartment influent stream. In response, a considerable improvement in MESC performance was observed with a current density of 6.4 mA cm −2 (per separator area) and a CH4 production of 0.83 L (LR d) −1 ( R = cathode volume). Once Ni and Fe were removed from the influent solution, the performance remained unchanged. Electron dispersive spectroscopy confirmed Ni and Fe electrodeposition. A shift from CH4 to acetate and ethanol production with concentrations reaching 5 and 8 g L −1, respectively, was observed upon increasing the cathode compartment pH to 8.5–9.0. 16S rRNA gene sequencing showed significant changes in the bacterial population at the cathode with Clostridia representing almost two-thirds of the population. Methanosaeta, Methanobrevibacter, and Methanobacterium species dominated the archaeal community.