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NASA's current mandate is to land humans on Mars by 2033. Here, we demonstrate an approach to produce ultrapure H2 and O2 from liquid-phase Martian regolithic brine at ~-36 °C. Utilizing a Pb2Ru2O7-δ pyrochlore O2-evolution electrocatalyst and a Pt/C H2-evolution electrocatalyst, we demonstrate a brine electrolyzer with >25x the O2 production rate of the Mars Oxygen In Situ Resource Utilization Experiment (MOXIE) from NASA's Mars 2020 mission for the same input power under Martian terrestrial conditions. Given the Phoenix lander's observation of an active water cycle on Mars and the extensive presence of perchlorate salts that depress water's freezing point to ~-60 °C, our approach provides a unique pathway to life-support and fuel production for future human missions to Mars. [ABSTRACT FROM AUTHOR]

The chlorine evolution reaction (CER) and oxygen evolution reaction (OER) occur simultaneously due to the low difference (0.13 V) in their standard potentials. RuO2 is the state‐of‐art electrocatalyst used for both OER and CER. The activity and selectivity of different RuO2 low‐index facets, namely (100), (110), (111), (001) and (101), are investigated through ab‐initio density functional theory (DFT) based calculations. The selectivity of different facets is explored in a mixed OER‐CER region by combining Pourbaix diagrams and linear scaling relationships. The difference in limiting overpotential of OER and CER is identified as the selectivity descriptor (SDCER). The most CER‐ and OER‐selective facets are found to be (101) (SDCER=0.39 V) and (001) (SDCER=0.14 V), respectively. The understanding of facet dependent CER selectivity in RuO2 can be extended as a design strategy to modulate OER and CER activity and selectivity as per design requirements. [ABSTRACT FROM AUTHOR]