The primary source of oxygen in space exploration is derived from water electrolysis. Herein, we discovered a mild photochemical hydrogenation process that can convert CO₂ into carbon nanotubes (CNTs) and H₂O by using a Co-based catalyst. Hence, astronauts can extract oxygen from CO₂ metabolism to close the oxygen recycling loop (overall reaction: CO₂ → C + O₂), allowing for ∼100% theoretical oxygen recovery. This photochemical technique has enabled a high turnover number (the molar ratio of C to Co) of 240 for CNT formation during a 100 h reaction in a flow reactor. The oxygen recovery efficiency reaches approximately 68% when using flowing CO₂ and H₂, surpassing the theoretical maximum (50%) for the Sabatier reaction combined with water electrolysis at the International Space Station. The tip-growth mode of CNTs principally allows long-term oxygen recovery from CO₂, in addition to space manufacturing of CNTs.

中文翻译：

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光化学 CO2 加氢制碳纳米管和 H2O 用于太空探索中的氧气回收


太空探索中氧气的主要来源来自水电解。在此，我们发现了一种温和的光化学加氢过程，可以通过使用 Co 基催化剂将 CO₂ 转化为碳纳米管 （CNT） 和 H₂O。因此，宇航员可以从 CO₂ 代谢中提取氧气以闭合氧气循环（总反应：CO₂ → C + O₂），从而实现大约 100% 的理论氧气回收。这种光化学技术使在流动反应器中 100 h 反应期间形成 CNT 的 240 高周转数（C 与 Co 的摩尔比）成为可能。当使用流动的 CO₂ 和 H₂ 时，氧回收效率达到约 68%，超过了国际空间站 Sabatier 反应结合水电解的理论最大值 （50%）。除了 CNT 的空间制造外，CNT 的尖端生长模式主要允许从 CO₂ 中长期回收氧气。