Holistic Strategies Across Nano-, Micro-, and Macro-Scales to Enhance the Activity of Electrochemical CO 2 Reduction Reaction (CO 2 RR)

Electrochemical CO2 reduction reactions (CO2RR) have been developed to produce diverse chemicals where ethylene (C2H4) is regarded as a promising product. In this comprehensive research, the electrode (3 × 3 cm2), which is larger than the one typically used in a lab-scale test, was utilized, attaining high Faradaic efficiency toward C2H4 (FEC2H4) owing to optimized catalyst and system components. From the catalyst perspective, a Cu metal organic framework was thermally treated to obtain a superior surface area, which induced desirable Cu+ and formation of graphitic C phases, which are conducive to stabilization of surface-adsorbed CO (*CO) followed by dimerization as an essential intermediate step. In the system, injection of humidified CO2 showed better catalytic activity than injection of aqueous H2O and CO2 owing to intensified mass transport of reactants. In addition, the combination of an anion exchange membrane and anion ionomer facilitated the rapid removal of OH– ions, reducing side reactions. The in situ mechanism study supported the positive effects of the anion pair on the optimized catalyst where obvious intermediate peaks were found in the spectra. According to the stability test, the best system achieved ∼70 mA cm–2 and ∼70% of Faradaic efficiency toward C2H4 (turnover frequency for ethylene, TOFC2H4 20.18 h–1) for 48 h. The techno-economic analysis results and ethylene production cost of $1126.7/tonne also suggested that this system is economically viable. In conclusion, the best combination of catalyst material applied to 9 cm2 and reaction system intensified the current density and FEC2H4 successfully, providing insights into scale-up and commercialization of the process from nano-, micro-, and macro-scale studies.