Efficient syngas production from carbon dioxide emissions via system engineering

Carbon dioxide (CO₂) electrolysis (CO₂R), using renewable electricity and CO₂ emissions, provides a sustainable pathway to the production of commodity chemicals and fuels. Today's CO₂R systems achieve practical reaction rates (>100 mA cm⁻²) and energy efficiencies (>40 %) in the sustainable production of syngas (carbon monoxide (CO) and hydrogen (H₂)). However, conventional neutral- and alkaline-media electrolyzers suffer (bi)carbonate formation, due to the spontaneous reaction between CO₂ and OH⁻ ions. The (bi)carbonate ions crossover to the anode and then converted back to the gaseous CO₂ by the protons. The CO₂ mixes with oxygen produced by the oxygen evolution reaction (OER). The undesirable (bi)carbonate formation sets impractical carbon efficiency limits, imposing energy penalties associated with CO₂ recovery. This work presents a system design concept that enables the recovery and reutilization of CO₂, breaking the impractical carbon efficiency limits in neutral-media CO₂R-to-CO systems. The CO₂R system herein eliminates the anodic separation process by employing a thermodynamically favourable liquid-product-oxidation-process (LPOP). The full system achieves a CO Faradaic efficiency of 66.9 %, a current density of 100 mA cm⁻², and a carbon efficiency of 44.6 %. The CO₂R-LPOP integration produces CO with an energy input of 26.6 GJ ton⁻¹, representing a ∼40 % less energy input compared to its conventional neutral-media CO₂R-OER counterpart.