Breaking Supercapacitor Symmetry Enhances Electrochemical Carbon Dioxide Capture
Zhen Xu, Xinyu Liu, Grace Mapstone, Zeke Coady, Charles Seymour, Selina E. Wiesner, Svetlana Menkin, Alexander C. Forse
Abstract
High Resolution Image Download MS PowerPoint Slide Electrochemical CO 2 capture using supercapacitors offers an energy-efficient approach for mitigating CO 2 emissions, but its performance is thought to be hindered by competing CO 2 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 CO 2 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 CO 2 uptake in capacitive systems by suppressing competing processes, while the noncapacitive zinc counter electrode simplifies the mechanistic picture of capacitive CO 2 capture. Extending this approach, we develop asymmetric supercapacitors with two different porous carbon electrodes, demonstrating a 200% increase in CO 2 capture capacities at low charging rates. In summary, this study pioneers asymmetric systems for electrochemical CO 2 capture and establishes a general strategy to enhance both understanding and performance.