(411e) Microfluidic Reactor for Electrochemical Reduction of CO2

Efficient conversion of CO2 into useful chemicals would address the intertwined issues of domestic energy security and climate change. This approach is much more attractive than simply capturing CO2 followed by sequestration, an approach that is receiving significant attention lately. Chemical conversion of CO2 can in principal be performed locally, at the capture source, whereas the sequestration approach would require transportation from the source to a suitable sequestration site. Furthermore, conversion of CO2 to a useful product would likely make it more economical to capture CO2 and prevent its release to the atmosphere. Also, CO2 can be reduced to formic acid [1], which is a promising fuel for fuel cells [2]. This would provide a means of energy storage that is needed for intermittent renewable sources such as wind and solar to become a major source of electricity. Coupling an electrochemical reactor for reducing CO2 with a fuel cell would allow excess electricity to be stored in chemical form (via formic acid), and later converted back to electricity when supply from the renewable source is insufficient. The formic acid could also be used in fuel cells to make high energy density power sources for portable applications. CO2 can also be reduced to CO to make syngas, which can be use to make longer chain hydrocarbons through Fischer-Tropsch synthesis [3]. These products can serve both as fuels (gasoline) and feedstock for chemical synthesis, which is another large consumer of fossil fuels. More efficient catalytic processes and better electrochemical reactors are needed to make efficient conversion of CO2 into useful chemicals economically feasible.

Our research group has previously developed a microfluidic fuel cell [4]. In this presentation we will illustrate the design and characterization of a microfluidic electrochemical platform based on our fuel cell to accomplish the efficient reduction of CO2 to formic acid. This design uses a flowing liquid electrolyte stream, which offers a number of benefits: (i) media flexibility in both composition and pH, (ii) electrolyte supplies reactant (H2O) to anode and eliminates any water management issues, (iii) reference electrode in exit steam allows analysis of individual electrodes. We will present our findings on the effects of electrolyte composition, pH and catalyst on formic acid production from CO2 along with developments in the reactor design.

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[2] Y. Zhu, S. Ha, R. Masel, J. Power Sources, 130, 2004, 8.

[3] N. Furuya and S. Koide, Electrochimica Acta, 36, 1991, 1309; T. Yamamoto, D. Tryk, A. Fujishima and H. Ohata, Electrochimica Acta, 47, 2002, 3327.

[4] R. Jayashree, M. Mitchell, D. Natarajan, L. Markoski, and P. Kenis, Langmuir, 23, 2007, 6871.