Electrochemical CO$_2$ Reduction via Gas-Phase Catholyte*

Reducing CO$_2$ to CO through electrolysis, for the eventual conversion to hydrocarbons, provides a path towards utility-scale seasonal storage of renewable energy. Electrochemical reduction of CO$_2$ has previously been achieved using a two chamber system. The chambers are typically separated by a semipermeable Nafion membrane, with an oxygen evolution catalyst anode on one side, a gold cathode on the other, and a solution containing CO$_2$ on both sides. If instead, CO$_2$ gas was in the second chamber, the reaction should yield more CO formed from CO$_2$ at a given overpotential; this would result from the increased concentration of CO$_2$ at the cathode surface and more facile mass transport of the CO and CO$_2$. With liquid in one chamber and gas in the other, electrolysis is performed by integrating the cathode onto the semipermeable Nafion membrane. This membrane electrode assembly is fabricated via nanoimprint lithography (NIL), simultaneously achieving high active surface area and permeability. Challenges to the Nafion NIL process, and the performance of the system in CO$_2$ reduction, will be presented.