Description: In the combined Phase I and Phase II programs Faraday and our MIT collaborators will demonstrate the feasibility of low-cost fabrication of high-efficiency, microchannel-plate reactors for the electrocatalytic reduction of CO2 to CH4. The proposed concept is founded on FARADAYIC® Through-Mask Etching of metallic (e.g., stainless steel and titanium) substrates to form suitable microchannel electrodes, and on pulse-reverse FARADAYIC® Electrodeposition of copper for uniform coating of the cathode surfaces. The electrocatalytic efficiency of the copper layer will be enhanced through the use of a literature-reported oxide-reduction process. Inclusion of a suitably large density of channels should result in substantial active area in a compact form factor, while entirely avoiding the complications of packed-bed type reactors. Faraday plans to focus development toward the ultimate use of room-temperature ionic liquids (ILs), as they afford such advantages as negligible evaporative loss, generally high CO2 solubility and low CH4 solubility, and a broad potential window of electrochemical inertness. The particular challenge of gas-liquid separations in microgravity, where buoyant effects cannot be exploited, will be addressed through a novel centripetal application of an established spiral-channel microfluidic concept. The envisioned system described in this proposal consists of three distinct unit operations: (1) an absorber which "getters" gaseous CO2 from the atmosphere using a wet room temperature IL-based electrolyte, (2) a microfluidic electroreactor which efficiently converts the CO2 to CH4 with oxygen being generated as useful by-product, and (3) a spiral-channel gas-liquid separator to remove the CH4 and O2 from the IL stream which is recycled to the absorber.

Benefits: The proposed technology will create low cost, compact, robust, high-efficiency microreactor systems for conversion of CO2 to CH4, with integrated centripetal microchannel separators for gas-liquid separations in microgravity. NASA applications would benefit from the capability for in-situ generation of hydrocarbon fuels from CO2 sourced from, e.g., crew exhalation gases or the Martian atmosphere. The compact form factor of the proposed stackable-plate is anticipated to integrate readily into NASA space vehicles.

The proposed technology not only addresses the desire for "ISRU processes associated with collecting, separating, pressurizing, and processing gases collected from in-situ resources including the Mars atmosphere, trash processing, and volatiles released from in-situ soil/regolith resources, into oxygen, methane, and water," but also provides a manufacturing route to "highly efficient chemical reactors … based on modular/stackable microchannel plate architectures" for efficient, low-power, in-situ conversion of carbon dioxide to methane. Reduction in anthropogenic greenhouse gas (GHG) emissions, including CO2, is a well-established governmental and business target. In the Sixth United States Climate Action Report, for example, the goal of "reducing U.S. greenhouse gas emissions in the range of 17 percent below 2005 levels by 2020" was noted. Broader interest in the developed world also exists for reductions in GHG emissions. Electrical power generation by fossil fuel combustion and industrial production all entail large amounts of generated CO2 at present. Upon demonstration and scaling, the produced microreactors will be compatible with existing technologies and installable directly into the market.