Dual Function Materials Enabling Human Space Flight: Carbon Dioxide Capture and Conversion for Life Support on Crewed Missions.

Carbon dioxide removal is important for keeping astronauts alive in space, where CO₂ can accumulate to harmful or even deadly levels in cabin air if untreated. Additionally, on Earth, CO₂ direct air capture is an important technology for reversing the harmful impacts of rising anthropogenic atmospheric CO₂ concentrations. In both scenarios, captured CO₂ needs to be dealt with, potentially via reaction into a more desirable final product such as renewable hydrocarbons or water. One potential solution is utilizing combined solid sorbents and catalysts in one material, known as dual function material (DFM). In this work, DFMs are used to capture and convert CO₂ from spacecraft cabin air into water as a form of recycling, which is necessary for enabling a longer duration human spaceflight. DFM is studied with CO₂ concentrations relevant to cabin air conditions for astronauts (1500 to 3000 ppm of CO₂) both with and without moisture present. DFM CO₂ capacity increases by nearly a factor of 4 and uptake rates by 10 with more realistic moist inlet air compared to dry cabin air. The wet capacity of DFM is comparable to state-of-the-art sorbents in use on the International Space Station (ISS) now; however, ISS systems must dry cabin air before CO₂ capture since they lose CO₂ capacity with a wet air inlet. DFM shows promise to save significant mass, size, power, and complexity for a CO₂ removal and conversion system, which could help enable longer duration human space missions.