Room Temperature Conversion of CO₂ Into Graphitic Carbon Quantum Dots by Field-Induced Electron Localization at Ag...

Converting CO₂ into solid carbon under mild conditions remains one of the foremost challenges. Here, a field-induced electron localization strategy that enables room-temperature transformation of CO₂ captured in amine solution into graphitic carbon quantum dots (g-CQDs) is reported. Rapid electron injection (at relatively low bias -1.3 to -1.7 V vs. Ag/AgCl) to a nanoscale AgO/Ag interface stabilized by the [BMIM]⁺[BF₄]^- ionic liquid generates a dynamic interfacial electron layer that sustains continuous electron transfer under a strong localized electric field. Operando Ag K-Edge XANES combined with theoretical simulations reveal pronounced electron localization at the Ag nanoparticle/electric double layer (Ag-EDL) interface, which activates CO₂ reduction via CO intermediates and C₂-radical coupling, yielding g-CQDs with negligible gaseous and liquid byproducts. The process requires only 0.9 kWh kg^{- 1} C, representing a record low energy demand for solid-carbon formation from CO₂ under ambient conditions. Scaled operation in a 2-L reactor demonstrates steady g-CQD production and incorporation of only 0.05 wt.% of the CO₂-derived g-CQDs into Portland cement enhances compressive strength of the cement mortar by ≈40%, attributed to the high dispersibility and nucleation activity of g-CQDs. This work establishes field-induced electron localization as a versatile platform for ambient CO₂ conversion into value-added carbon nanomaterials.