The capture and conversion of carbon dioxide (CO2) from industrial flue gas is a promising carbon capture, utilization, and storage (CCUS) process. Traditional routes typically follow a "capture-release-compression-electrolysis" tandem pathway, which is complex and energy-intensive. As an emerging reactive carbon capture technology, the bicarbonate-mediated integrated CO2 capture-electrolysis route couples upstream CO2 capture with subsequent electrocatalytic conversion, reducing the energy consumption associated with obtaining high-purity CO2 feedstock.
The electrolysis of bicarbonate capture liquids is a crucial step in the bicarbonate-mediated integrated CO2 capture-electrolysis route. However, this step suffers from insufficient current density (low reaction rate) and high cell voltage (low energy efficiency) .
In a study published in Angewandte Chemie International Edition, a research team led by Profs. BAO Xinhe, GAO Dunfeng, and ZHANG Guohui from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) in collaboration with Prof. WANG Guoxiong from Fudan University achieved efficient bicarbonate-mediated integrated CO2 capture and electrolysis to CO through an ionomer-driven reaction microenvironment control strategy.
Ionomer-driven reaction microenvironment control in bicarbonate-mediated integrated CO2 capture and electrolysis (Image by RONG Youwen)
Researchers improved the bicarbonate electrolysis performance by manipulating reaction microenvironments by introducing ionomers into cobalt phthalocyanine (CoPc) electrodes. In a cation exchange membrane-based zero-gap electrolyzer, the CoPc electrode modified with a Nafion ionomer exhibits a high CO Faradaic efficiency of 93% at an applied current density of 300 mA cm−2 and a CO partial current density of 410 mA cm−2 at a low cell voltage of 3.09 V.
Electrode structure characterization and finite element simulation results indicated that the proton conductivity of the Nafion ionomer increases the local concentration of in situ generated CO2 (i-CO2) in the proximity of the CoPc catalyst, resulting in improved CO formation.
Furthermore, researchers demonstrated a closed-loop CO2 capture and electrolysis cycle at the device level using the Nafion-incorporated CoPc electrode and a simulated flue gas.
"Our study showcases the promise of the reaction microenvironment control strategy for improving bicarbonate electrolysis performance and advancing reactive carbon capture technology," said Prof. GAO.