CO₂ Capture from Simulated Martian Atmosphere for Electrolytic Co-Production of Carbon and Oxygen Using Li₂CO₃-CaCO₃ Molten Salts

This study employs a Li2CO3-CaCO3 molten salt system for CO2 capture from simulated Martian atmosphere (96% CO2, 2% N₂, 2% Ar) with simultaneous electrochemical conversion to carbon (C), carbon monoxide (CO), and oxygen (O2). Using an Fe-Ni alloy inert anode, we systematically investigated CO32 reduction mechanisms at the cathode, corrosion behavior of the Fe-Ni anode, oxygen evolution reactions, and temperature-dependent product distributions. Results demonstrate that cathodic CO32 reduction constitutes a diffusion-controlled irreversible process. Below 900°C, CO32 undergoes preferential reduction to solid carbon, where electrolysis at 880°C yields maximally graphitized carbon with an ID/IG ratio of 0.35. Above 900°C, CO formation dominates the reduction process, accounting for 36.5% of cathode gas at 930°C. The Fe-Ni alloy anode exhibits exceptional stability in molten salt, forming a protective Fe2O3-NiFe2O4 composite oxide layer during electrolysis that effectively safeguards the substrate. During anodic reactions, O2 discharge precedes CO32 oxidation, governed by O2 concentration gradients and diffusion kinetics within the molten salt, causing O2 concentration to increase with temperature until peaking at 83% at 880°C before declining markedly above 900°C.