No abstract

No abstract

The renewable-electricity-driven carbon dioxide reduction reaction (CO2RR) is potentially a pathway to closing the anthropogenic carbon cycle; however, it is challenging to couple a fast cathodic CO2RR that endows tunable selectivity with a kinetically matched anodic oxygen evolution reaction (OER) at a promising energy efficiency. Here, we report a cost-effective strategy to convert CO2 into C/CO (tunable selectivity of over 70%) with enhanced OER kinetics in water-soluble Na-K-based molten carbonate by modulating the electrolyte’s oxo-acidity using earth-abundant borax (Na2B4O7) as an electrolyte additive, where the borates acting as O2– (an oxo-base) shuttles that constantly mediate between cathode and anode can concurrently facilitate CO2RR and OER. In particular, it can respectively sustain CO2RR at a stable current density of 100 mA cm–2 with a considerable OER current density of ∼300 mA cm–2. The optimal energy efficiency can reach up to over 60%, opening avenues for efficiently manipulating CO2RR and simultaneously enhancing OER.

Harvesting oxygen and metals from the local resources of the Moon is a key step to advancing outer space exploration. A large amount of oxygen is stored in the lunar regolith in the form of oxides. Many efforts have been devoted to electrochemically splitting oxides to oxygen and metals in molten oxides and molten salts. However, a cheap oxygen-evolution inert anode is still a serious challenge, especially in the supercorrosive molten halides. Herein, we combine a molten CaCl 2 electrolyzer that can convert Chang'e-5 lunar regolith simulants to metals and CO 2 using a carbon anode and a molten carbonate electrolyzer that can convert the generated CO 2 to carbon and oxygen using a cheap Ni11Fe10Cu oxygen-evolution anode. Further, the electrolytic carbon is reused as the anode in the molten CaCl 2 electrolyzer, thereby closing the carbon cycle. Hence, the overall electrochemical reaction of the dual-electrolyzer system is to convert lunar regolith to metals and oxygen. More broadly, this system can convert the CO 2 generated by humans living on the Moon and Mars to oxygen and carbon materials.