With the realization of the global impact of waste carbon on the atmosphere, coupled with a clear and growing demand for abundant electricity, there are both environmental and economic driving forces for capturing and converting carbon dioxide (CO2) into high value hydrocarbon products. Two conversion approaches that have been studied extensively are the electrochemical CO2 reduction reaction (eCO2R) and the thermochemical Fischer-Tropsch reaction (F-T); however, leveraging the two reactions together for direct CO2 conversion to synthetic fuels has been challenging due to mismatched reactor size and scales of production, incompatible operating conditions, and poor stability of F-T catalysis in the presence of CO2-rich reactant streams. This work employs advanced manufacturing to bridge the gap between these two technologies by creating custom 3D-printed reactors. These reactors were designed to align the scale of production for each reaction and consequently allow for a combined electrochemical-thermochemical approach for converting CO2 to C4+ synthetic fuels. A range of operating conditions for each process were investigated: for eCO2R, electrochemical potential and reactor geometry were tailored for maximum conversion of CO2 to CO and optimal ratio of H2:CO; for F-T, catalyst synthesis and operating temperature were studied for conversion of CO2-rich reactant streams to multi-carbon products at ambient pressure. As a result, we report a joint electro-thermochemical system that reaches a maximum of 20% single-pass conversion of CO2 that is stable for over 8 hours; furthermore, we achieve &gt; 60% selectivity to C4+ products. This work represents a method to achieve high selectivity to desired products from CO2, as well as a viable path for scaling these technologies together for sustainable production of synthetic fuels and valuable products from waste carbon.

Combined electro-thermochemical system for conversion of waste carbon to C4+ synthetic fuels using 3D-printed reactors

ACS Fall 2021

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