Abstract
Microbial electrosynthesis is a new approach to converting C1 carbon (CO2) to more complex carbon-based products. In the present study, CO2, a potential greenhouse gas, was used as a sole carbon source and reduced to value-added chemicals (acetate, ethanol) with the help of bioelectrochemical reduction in microbial electrosynthesis systems (MES). The performance of MES was studied with varying electrode materials (carbon felt, stainless steel, and cobalt electrodeposited carbon felt). The MES performance was assessed in terms of acetic acid and ethanol production with the help of gas chromatography (GC). The electrochemical characterization of the system was analyzed with chronoamperometry and cyclic voltammetry. The study revealed that the MES operated with hybrid cobalt electrodeposited carbon felt electrode yielded the highest acetic acid (4.4 g/L) concentration followed by carbon felt/stainless steel (3.7 g/L), plain carbon felt (2.2 g/L), and stainless steel (1.87 g/L). The alcohol concentration was also observed to be highest for the hybrid electrode (carbon felt/stainless steel/cobalt oxide is 0.352 g/L) as compared to the bare electrodes (carbon felt is 0.22 g/L) tested, which was found to be in correspondence with the pH changes in the system. Electrochemical analysis revealed improved electrotrophy in the hybrid electrode, as confirmed by the increased redox current for the hybrid electrode as compared to plain electrodes. Cyclic voltammetry analysis also confirmed the role of the biocatalyst developed on the electrode in CO2 sequestration.
Highlights
Increasing amounts of CO2 emission is a major global issue that must be addressed soon [1,2]
Microbial electrosynthesis systems (MES) is a doublechambered system consisting of anode and cathode compartments, where acetogenic microbes at the cathode catalyze the reduction of CO2 via using electrons and protons generated from cathode and electrolyte, respectively
We explored various biocathodes viz. carbon felt (CF), stainless steel mesh (SS), CF and SS merger (CF/SS), and an electrodeposited hybrid electrode (CF/SS/Co-O) composed of CF, SS, and a cobalt oxide (Co-O)
Summary
Increasing amounts of CO2 emission is a major global issue that must be addressed soon [1,2]. In MES, electrode material and electrotrophy are conjunctively playing a key role as the bioelectrochemical reactions occurring within the system are regulated by the biofilm formed on the electrode surface [15]. In MES, capacitance, electrotrophy, and electron flux are dependent on various electrode properties such as material, composition, porosity, biocompatibility, anticorrosive, mechanical strength, surface area, impurities, and others that in turn catalyze the bioelectrochemical reactions on their surface [18]. Coating the electrode surface with modifiers such as PANI, PPy, CNT, and chitosan can provide a larger surface area and enhance the biofilm development and electron transfer, thereby enhancing the system efficiency [23,24,25] Metal catalysts such as Ni, Au, and Pd can improve the electron transfer by lowering the activation energy [26,27]. Comparative analysis of biochemical and electrochemical parameters for four different biocathodes was conducted to evaluate the optimum biocathode material and increasing the MES performance
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