Space programs around the globe have begun to consider the logistical demands of missions beyond the orbital neighborhood of Earth. Unlike local installations such as the International Space Station, long-range missions will not have the option to resupply critical materials from Earth. Thus, the development of capabilities for what is often termed “In-Situ Resource Utilization” (ISRU) have been a continuing focus of research through NASA and other agencies. One particular long-range mission of interest is to place human astronauts on Mars; the major component of the thin Martian atmosphere is carbon dioxide, making CO2 a natural input to ISRU technologies for production of carbon-containing materials. Production of mission consumables from in-situ Mars resources will be critical to enabling human exploration of Mars, in part by minimizing the number and size of descent/ascent vehicles. Potential ISRU products from CO2 include that seem likely to provide significant mission benefits with minimal infrastructure required are propellants (e.g., hydrocarbons), fuel cell reactants (e.g., formic acid, methanol, carbon monoxide), and life support consumables (e.g., oxygen). The first portion of this talk will comprise a high-level overview of the chemical transformations that can be imparted to CO2 via electrocatalysis on gas-diffusion electrodes (GDEs), in the form of a summary of literature reports on the catalytic performance of a wide variety of single-metallic and metal-alloy systems. The remainder will encompass an exposition of the electrocatalytic performance of tin and copper single-metal GDE electrocatalysts prepared by pulsed electrodeposition. These metals are well known for their ability to reduce carbon dioxide to formic acid and hydrocarbons/carbon monoxide, respectively, and are under active development in numerous academic research groups and industrial entities to this end. These experimental results clearly demonstrate the power and flexibility of the pulse/pulse-reverse electrodeposition approach to catalyst fabrication, as evidenced by the appreciable effects of the pulsed-waveform electrodeposition parameters on CO2 electroreduction product distribution and total current density.
A bioinspired molybdenum–copper molecular catalyst for CO2 electroreduction