The zero-gap CF-MEA is an appealing device for CO2R to reduce ohmic losses, but the C2-selective catalysts developed under alkaline flow cells show decreased C2 selectivities in MEA systems. One of the reasons is due to excess surface coverage of CO2 at catalysts surface enabled by MEA that blocks active sites for carbon-carbon (C-C) coupling reactions. To this end we searched for optimal CO2-to-ethylene conversion conditions in MEA devices via innovative materials design and tunings of local environment, and studied how they could be coupled together to activate CO2 and accelerate CO2R in the most energy-efficient ways. Particularly, silica nanoclusters show enhanced CO2 adsorption and the copper-silica interface delivers a 65% ethylene selectivity from CO2R (Nature Communications 2021). Later, a series of metal phthalocyanine molecules were immobilized at the Cu surfaces to confine CO and C2 intermediates towards a record 73% ethylene selectivity. Two manuscripts under development are related to these research findings.
We then developed new methods to steer the ethylene and ethanol selectivities from CO2R. While the CO2-to-ethylene conversion on Cu-based catalysts is thermodynamically favourable, promoting ethanol production by supressing ethylene formation pathways has mainly been explored using density functional theory (DFT) calculations. Guided by DFT analysis, we unveiled the ethylene-ethanol switching mechanism and then developed efficient strategies to improve ethanol electrosynthesis from CO2R. Our results suggest that tunings of the hydroxyl and CO coverages at the Cu surface offer a great opportunity to promote ethanol and suppress ethylene from CO2R. To do so we employed a new pulsed electrolysis coupled with the design of bimetallic Cu alloys to achieve the ideal combinations of hydroxyl and CO adsorptions. As a result, we achieved 50% ethanol selectivity from CO2R and the related results are currently under manuscript drafting for publication.
We disseminated the project results through diverse means: (1) 8 research talks to world-class universities such as ETH Zurich (Switzerland), Princeton University (US), University of British Columbia (Canada), Shanghai Jiao Tong University (China), etc.; (2) one live educational session to general audience in the “Celebration: EPFL turns 50!” event before the Covid; (3) social media platforms including Twitter, Facebook and LinkedIn since the pandemic.
