Syngas production: diverse H2/CO range by regulating carbonates electrolyte composition from CO2/H2O via co-electrolysis in eutectic molten salts

Abstract

We present a novel sustainable method for the direct production of syngas (H₂ + CO) from CO₂/H₂O co-electrolysis using a hermetic device, to address the continuously increasing level of environmental carbon dioxide (CO₂). All experiments were conducted using a two-electrode system with a coiled Fe cathode and coiled Ni anode in eutectic mixtures of binary and ternary carbonates with hydroxide in a 0.1 : 1 hydroxide/carbonate ratio. With an applied voltage of 1.6–2.6 V and an operating temperature of 500–600 °C, the H₂/CO product ratio was easily tuned from 0.53 to 8.08 through renewable cycling of CO₂ and H₂O. The Li_0.85Na_0.61K_0.54CO₃–0.1LiOH composite had the highest current efficiency among those tested, with an optimum value approaching ∼93%. This study provides a promising technique for the electrochemical conversion of CO₂/H₂O to a controllable syngas feedstock that can be used in a broad range of industrial applications.