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

Abstract

This study employs Li 2 CO 3 -CaCO 3 molten salt for CO 2 capture from simulated Martian atmosphere (96% CO 2 , 2% N 2 , 2% Ar) with simultaneous electrochemical conversion to carbon, carbon monoxide, and oxygen. Using an Fe-Ni alloy inert anode, we systematically investigated the reduction mechanism of CO 3 2− at the cathode, corrosion behavior of the anode, oxygen evolution reactions, and temperature-dependent product distributions. Results from cyclic voltammetry demonstrate that cathodic reduction of CO 3 2− constitutes a diffusion-controlled irreversible process. Below 900 °C, CO 3 2− undergoes preferential reduction to solid carbon, where electrolysis at 880 °C yields maximally graphitized carbon with an I D /I G 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 Fe 2 O 3 -NiFe 2 O 4 composite oxide layer during electrolysis that effectively safeguards the substrate. During anodic reactions, O 2− discharge precedes CO 3 2− oxidation, governed by O 2− concentration gradients and diffusion kinetics within the molten salt, causing O 2 concentration in the anode gas to increase with temperature until peaking at 83% at 880 °C before declining markedly above 900 °C.