Substantially improved efficiency and selectivity of carbon dioxide reduction by superior hydrated electron in microdroplet

The photochemical conversion of CO 2 into valuable fuels faces challenges of low efficiency and poor selectivity. Hydrated electrons (e aq − ), with their extremely negative reduction potential, are promising CO 2 -reducing agents, yet their short lifetime limits selectivity and high-energy-density product formation. Herein, we show that microdroplet interfaces with strong electric fields (10 9 volts per meter) substantially extend the lifespan of e aq − generated from industrial sulfite pollutants (SO 3 2− ), lowering energy barriers in the CO 2 reduction reaction and enabling targeted product formation. The machine learning strategy identified microdroplet size as the key parameter controlling electric field strength, product yield, and selectivity. In our lab-based scaled-up system, microdroplets <10 micrometers improved performance by four to seven orders of magnitude over bulk-phase systems, achieving ~99% methanol selectivity. Strong interfacial electric fields stabilize intermediates and modulate carbon-oxygen bond lengths, directing pathways to high-value products. This approach enables sustainable CO 2 utilization via microdroplets, potentially producing fuels from waste.