Modulation of Local Environment for Selective Bicarbonate Conversion to Multi‐Carbon Products
Tai Nguyen, Anh N. Nguyen, Guorui Gao, Jackson Crane, Thành Trần‐Phú, Gelson Tavares da Silva, Aldo Gonzalez‐Lopez, Hung Lai, Khac Huy Dinh, Duc‐Minh Phan‐Pham, Martin Guay, Carlos Escobedo, Rosalie K. Hocking, Jonathan Raisin, Lucia H. Mascaro, Cao‐Thang DinhABSTRACT
Renewable electricity‐powered direct electrosynthesis of multi‐carbon (C 2+ ) products such as ethylene (C 2 H 4 ) from bicarbonate offers a sustainable route for carbon dioxide (CO 2 ) utilization but is hindered by limited CO 2 availability and unfavorable reaction environments. Existing approaches, such as electrolyte engineering and buffering layers, often improve selectivity at the cost of higher full‐cell voltages, creating a trade‐off between selectivity and energy efficiency. Here, we introduce a new electrode design for direct bicarbonate (HCO 3 − ) conversion using highly porous copper electrodes coated with an ionomer/carbon layer. Multiphysics modeling results reveal that increasing HCO 3 − concentration enhances local in situ‐generated CO 2 ( i ‐CO 2 ) availability but suppresses the alkaline microenvironment required for C‐C coupling. We found that partially coating a large‐pore Cu electrode with the ionomer/carbon layer addresses the limitation by fine‐tuning the local reaction environment to favor C 2+ products while maintaining high CO 2 availability for high reaction rates. The optimized electrode achieves a C 2 H 4 Faradaic efficiency (FE) of 43% (total C 2+ FE of 60%) at 150 mA/cm 2 , with a low full‐cell voltage of 3.38 V. When coupled to a dilute CO 2 source (20% in argon) and pulsed operation, the system sustains > 30% C 2 H 4 FE for ∼150 h at 150 mA/cm 2 .