(666a) Electrochemical Upgrading CO2 into Fuels and Chemicals

Electrochemical CO₂ reduction (CO₂R) offers exciting opportunities in turning waste carbon into value-added chemicals/fuels. To date, Cu-based materials have shown appreciable activity and selectivity in producing multi-carbon products during CO2R. However, the unsatisfactory performance of Cu catalysts under practical relevant conditions has hindered the practical implementation of this technology. In addition to catalyst development, managing the microenvironment at the reaction interface is crucial for achieving the desired performance in CO₂R. Recently, managing the H₂O and CO₂ concentrations at the reaction interface has been found to play crucial roles in achieving enhanced CO₂R performance. However, achieving precise control of these variables during CO₂R remains challenging, and the underlying mechanisms that influence CO₂R are not fully understood. In this study, guided by a multi-physics model, we demonstrate that tuning the local H₂O/CO₂ concentrations is achievable by applying thin polymer coatings to the catalyst surface. Beyond the often-explored hydrophobicity, we find that the polymer properties of gas permeability and water-uptake ability are even more critical in tuning the local H₂O/CO₂ concentrations. Building upon these understandings, we achieve CO₂R on Cu with Faradaic efficiency exceeding 87% towards multi-carbon products at high current density of -2 A cm^-2. Encouraging cathodic energy-efficiency (>50%) is also observed at this high current density due to the substantially reduced cathodic potential. Additionally, we demonstrate stable operation of CO₂R for over 150-hour at practical relevant current densities owning to the stable interface enabled by the polymer coatings. Moreover, this strategy has been successfully extended to CO₂R based on membrane electrode assemblies. Our findings underscore the significance of fine-tuning of the local H₂O/CO₂ balance for future applications of CO₂R. Furthermore, building on the success of converting CO₂ into C₂H₄, we also developed a system capable of further converting the CO₂-derived C₂H₄ into ethylene glycol with high efficiency and selectivity.