Carbon dioxide electrolysis systems for high carbon efficiency

Renewable-electricity-powered CO₂ reduction (CO₂R) could enable penetration of renewables into the vast chemical industry. Present-day CO₂R technology realizes production of multi-carbon chemicals with industrially relevant rates (>100 mA cm⁻²). However, (bi)carbonate formation (2OH^– + CO₂ → CO₃^2– + H₂O), which occurs readily in systems based on neutral and alkaline electrolytes, results in CO₂ (reactant) loss and associated energy penalties that render the process unviable. This Review article focuses on the overview of carbon-efficient CO₂R systems: CO₂R with all-liquid-phase anodic process; acidic-media CO₂R; local CO₂ regeneration from (bi)carbonate via bipolar systems; tandem CO₂ conversion; and CO₂R from capture solutions. It analyses the current feasibility of each system, discusses the technical and scientific challenges associated with each strategy, and outlines future research directions toward carbon- and energy-efficient CO₂ electrolysis at scale. The Review article emphasizes that carbon-efficient CO₂R systems eliminate (bi)carbonate formation and ensuing energy penalties. With the recent catalysis- and system-level breakthroughs, some of these systems (CO₂R with all-liquid-phase anodic process, tandem CO₂ conversion, and acidic-media CO₂R) outperform the conventional alkaline and neutral-media CO₂R systems in terms of energy intensity. The Review article underscores that achieving breakeven energy intensity requires further energy efficiency improvements, calling for innovative electrocatalysis and system integration approaches.