CO2-Derived Graphite: A Critical Material for Terrestrial and Martian Sustainability.

CO2, one of the major contributors to global climate change, is a promising carbon feedstock for graphite synthesis. Graphite is the only carbon-based critical material recognized by numerous countries and international organizations, with various applications including energy storage on Earth and Mars. Herein, this study realizes the mild, efficient in situ synthesis of graphite from CO2, H2O, and borate, which are abundant on both planets. At 220°C and 5.0 MPa with NaBH4, graphite is obtained with 79.2% selectivity and 93.1 wt.% purity, and byproduct NaBO2 can be electrochemically recycled for sustainable material utilization. Mechanistic investigations reveal that CO2 reacts with NaBH4 to form methane, ethylene, and propadiene. Methane and ethylene generate aromatics, while propadiene promotes polymerization into graphite. As a Zn-based battery anode, the graphite retains 90.9% capacity after 2500 cycles at 1.0 A·g-1 for Zn-CO2||MnO2, confirming excellent energy storage performance. This work not only provides a novel, sustainable strategy for CO2 utilization and storage but also aims to bridge terrestrial environmental crisis mitigation and extraterrestrial in-situ resource utilization, laying a foundational basis for material, environmental, and energy sustainability on Earth and Mars.