Abstract
Renewable electricity-powered reduction of CO2 (CO2R) is a promising route to upgrade CO2 to ethylene, an industrial feedstock in high demand. Compared with direct CO2 electroreduction to ethylene, CO2-CO-C2H4 tandem electrolysis is more carbon efficient, circumventing CO2 crossover and carbonate formation. However, current CO electroreduction produces a mixture of multi-carbon products (ethylene, ethanol, acetate, and propanol), and the mechanism underlying this dispersion of selectivity remains unclear.We studied the role of the microenvironment of the electrode in selectivity among C2+ products, and hypothesized that destabilizing the oxygen-containing intermediates would direct the reaction pathway toward the sole oxygen-free C2+ product, ethylene. When we explore the cations in electrolyte, we find the one with the most robust hydration shell (Li) promotes ethylene production, among C2+ products, compared to weakly hydrated cations (e.g. K). This is a distinctive trend compared to studies of activity that found reverse cation trend in jc2+. A combined study of operando Raman spectroscopy, MD simulation, and DFT calculation suggests that the strongly hydrated Li+ on the electrode surface has the greatest H2O-Ointermediate interaction and the least cation-Ointermediate interaction. This increases the difference in activation energy of the selectivity-determining step between ethylene pathway and oxygenates pathway, and hence leads to the preference of Li for hydrocarbons over oxygenates. Figure 1
Published Version
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