Plasmonic photosynthesis of C₁-C₃ hydrocarbons from carbon dioxide assisted by an ionic liquid

Photochemical conversion of CO₂ into fuels has promise as a strategy for storage of intermittent solar energy in the form of chemical bonds. However, higher-energy-value hydrocarbons are rarely produced by this strategy, because of kinetic challenges. Here we demonstrate a strategy for green-light-driven synthesis of C₁-C₃ hydrocarbons from CO₂ and H₂O. In this approach, plasmonic excitation of Au nanoparticles produces a charge-rich environment at the nanoparticle/solution interface conducive for CO₂ activation, while an ionic liquid stabilizes charged intermediates formed at this interface, facilitating multi-step reduction and C-C coupling. Methane, ethylene, acetylene, propane, and propene are photosynthesized with a C₂₊ selectivity of ~50% under the most optimal conditions. Hydrocarbon turnover exhibits a volcano relationship as a function of the ionic liquid concentration, the kinetic analysis of which coupled with density functional theory simulations provides mechanistic insights into the synergy between plasmonic excitation and the ionic liquid.