Microbial electrosynthesis cell (MEC) electrodes analyzed by using high resolution microscopy techniques

The intermittent nature of renewable sources of energy, most notably solar and wind, is leading to a search for strategies to capture the electrical energy produced from these sources in covalent chemical bonds, producing compounds that can readily be stored and consumed on demand, preferably within the existing infrastructure. One particularly attractive option is to reduce carbon dioxide (CO2) to produce multicarbon organic compounds that are precursors for desirable organic chemicals or liquid transportation fuels. Basic requirements for a practical system to fix carbon dioxide in this manner include the ability to use electrons derived from water as an abundant, inexpensive source of reductant and inexpensive, durable catalysts. Non biological electrochemical reduction of carbon dioxide has proven problematic. In contrast to bio-electrochemical processes which seem to be a promising alternative in recent time. The ability to transfer energy from renewable sources in the form of electrical energy to microorganisms which are further able to store the energy in multicarbon organic compounds is summarized in the scientific literature in the topic "microbial electrosynthesis". The resulting systems are called MEC’s (Microbial Electrolysis Cells), which use specific electrodes consisting of carbon felts onto which microorganisms adhere and grow to accept electrons and use them further for the reduction of several substances present in the surroundings. The used microorganisms were anaerobic bacteria from the genus Clostridium that are able to reduce CO2 in acetate, butanol and ethanol. The used microscopies were epifluorescence microscopy and atomic force microscopy (AFM). Under protective atmospheric conditions in a potential-free environment both techniques revealed that clostridial species accept the surfaces of the carbon electrodes for colonization by intensive biofilm formation, which is a fundamental prerequisite for microbial electrosynthesis. Further studies shall clarify whether biofilm formation will be changed by applying a potential or will be optimized by varying ambient parameter, such as pH value, temperature or the chemistry of the MEC cell, by this way creating optimal living conditions for the microorganisms to produce multicarbon organic compounds.