Direct photoconversion of CO2 to carbon nanotubes for oxygen recycling in extraterrestrial exploration

Abstract The Sabatier reaction coupled with water electrolysis constitutes the state-of-the-art oxygen recovery technology in International Space Station missions, but the oxygen recovery efficiency of this system is only 49% (theoretical maximum 50%). Technologies that could realize oxygen recovery of >75% are urgently needed for long duration manned missions. Herein, we found a mild photochemical process that can convert CO2 into carbon nanotubes (CNTs) over a Co-based catalyst, thus permitting 100% theoretical oxygen recovery. This photochemical technology has enabled a high turnover number (the molar ratio of C to Co) of 160 for CNT formation, the tip-growth mode of which principally allows sustained and long-term oxygen recovery from CO2. The established photochemical strategy for CO2 hydrogenation into CNTs closes the oxygen recycling loop, which would promote mankind to travel to the Sea of Stars.