On the Viability of Carbon Dioxide in-Situ Resource Utilization (ISRU) to Produce Chemical Feedstocks on Mars

Abstract

The vision of a sustained human presence in space and extraterrestrial bodies necessitates an ever-larger share of life sustaining materials to be produced by in-situ resource utilization (ISRU). In this context, on Mars, NASA envisions the transformation of Martian atmospheric carbon dioxide into potential feed stocks through a process of climate enhancing resource utilization (with the technology being applicable for CO2 utilization on Earth as well) [1]. Amongst the potential raw materials present on Mars, the presence of stable brines in the liquid phase [2] (due to dissolved perchlorate salts suppressing the freezing point of water to < 213K) along with the availability [3] of 95 vol.% atmospheric CO2, can enable the development of a CO2-H2O electrolyzer to produce CO2 reduction products and O2. In this work, we examine the viability of such an electrolyzer system operating at or near Martian ambient conditions by developing thermodynamic and electrochemical polarization models of this system for various CO2 reduction products. Given the extreme operating conditions, the models were first applied to existing experimental data from an operational water electrolyzer under simulated Martian conditions to evaluate fit [2]. For the proposed CO2-H2O electrolyzer, the Nernst potential for various reactions, the anode/cathode catalysts, their corresponding overpotentials and separator conductivity were calculated or parameterized from experiments in the literature. This was integrated into the polarization model to predict the performance of these electrolyzers under Martian conditions and for various desired products. The polarization curves were calculated for the following possible reaction products; CO (# of e- = 2), HCHO (# of e- = 4), CH3OH (# of e- = 6), CH4 (# of e- = 8), C2H4 and C2H5OH (# of e- = 12) under both Earth and Mars conditions. CH4 and C2H5OH were found to be thermodynamically favored products as compared to other(s) across the range of operational temperatures from 230 K to 298 K. CO, HCHO and C2H4 can serve as potential feed stocks for downstream processing into other useful chemicals on Mars and strategies are discussed for their selective production.REFERENCES[1]. NASA, small business innovation research (SBIR) & small business technology transfer (STTR) program, 2022 phase I solicitation[2].Gayen, P., Sankarasubramanian, S., & Ramani, V. K., Fuel and oxygen harvesting from Martian regolithic brine. Proceedings of the National Academy of Sciences, 117(50), 31685, (2020).[3].Meyen, Forrest E., et al. "Thermodynamic model of Mars oxygen ISRU experiment (MOXIE)." Acta Astronautica 129, 82 (2016). Figure 1. Calculated electromotive force of the production of various CO2 reduction products. Figure 1