One promising method to move toward more sustainable energy sources is though converting electrical energy into chemical energy. More specifically, electrochemically converting CO2 to a useful form such as a fuel. One of the challenging processes in producing fuels or chemicals from CO2 has been efficiently and selectively producing C4-C6 and higher multifunctional organic compounds from CO2. In efforts to overcome these challenges, a system that combines the faster kinetics of electrochemical inorganic CO2 reduction catalysts with highly selective microbial metabolism is being designed and investigated. This system is unique as it is designed in the from the concepts of a specialized reactor developed for detailed studies on electrochemical CO2 reduction on metal surface in the Jaramillo lab, but modified for the addition of select microorganisms. This allows us to develop a selective, efficient, and sustainable process for converting CO2 to a fuel.We are investigating using a Sn electrocatalyst which reduces CO2 to formate, and the microoganism Methanococcus maripaludis which metabolizes formate and produces methane. In our first prototype set up a Sn cathode with a surface area of 5.89 cm2 was poised at a potential of -1.3 V vs NHE. This resulted in an average current density of -0.9 mA/cm2, and methane was produced by the microoganisms at a rate of 0.0289 mL/cm2 per minute. This result is promising as the rate of methane production is 100 fold greater than other similar bioelectrochemical systems. One of the main challenges of this research is to develop methods which enable the electrochemical CO2 reduction process to be robust, efficient, and stable on the time scale of months. Studies of a Sn electrocatalyst over long periods of time provide an insight of the mechanism of the deactivation of Sn in large time frames. These studies will allow for the development of methods to maintain the electrocatalysts activity and/or inhibit its deactivation. These studies will also be aimed toward developing larger scale electrochemical CO2 reduction systems, as in order to use these electrochemical systems commercially, many of the same issues on the electrochemical side must be overcome.

Integrated electrochemical-biological systems for the production of fuels and chemicals from CO2

253rd National Meeting (2017)

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