Breaking Supercapacitor Symmetry Enhances Electrochemical Carbon Dioxide Capture

Electrochemical CO₂ capture using supercapacitors offers an energy-efficient approach for mitigating CO₂ emissions, but its performance is thought to be hindered by competing CO₂ capture and release processes at two identical porous carbon electrodes. To address this, we introduce an asymmetric supercapacitor-battery hybrid system with porous carbon and nonporous metallic zinc as the working and counter electrodes, respectively. The CO₂ capture capacity continuously increases as the charging rate decreases with a maximum capacity of 208 mmol_CO2 kg^-1, surpassing that of an analogous symmetric supercapacitor. Our findings suggest that breaking device symmetry enhances CO₂ uptake in capacitive systems by suppressing competing processes, while the noncapacitive zinc counter electrode simplifies the mechanistic picture of capacitive CO₂ capture. Extending this approach, we develop asymmetric supercapacitors with two different porous carbon electrodes, demonstrating a 200% increase in CO₂ capture capacities at low charging rates. In summary, this study pioneers asymmetric systems for electrochemical CO₂ capture and establishes a general strategy to enhance both understanding and performance.