Carbon dioxide splitting using an electro-thermochemical hybrid looping strategy†
Reclaiming oxygen (O2) efficiently from carbon dioxide (CO2), a major product of human metabolism, is a key technology to minimize the oxygen supply required for challenging missions such as manned deep space exploration. Ideally, a method that can convert CO2 into elemental carbon (C) and O2 under mild conditions is highly desirable; however, due to the highly unfavorable thermodynamics, direct CO2 splitting requires extreme conditions. Herein, we present an electro-thermochemical hybrid looping (ETHL) strategy to split CO2 into C and O2 under mild conditions with a 100% theoretical oxygen recovery efficiency, which cannot be accomplished using any existing electrochemical or thermochemical process. The ETHL process combines an electrochemical step that reduces CO2 into carbon monoxide (CO) with a thermochemical step that further converts CO into C and CO2. By recycling the produced CO2 from the thermochemical step back to the first electrochemical step, this closes the loop with C and O2 as the only products. The results showed 96% selectivity for the CO2 electrolysis step and nearly 100% selectivity for the CO thermochemical step, demonstrating the feasibility of the ETHL strategy for complete oxygen recovery from CO2.