Room Temperature Conversion of CO ₂ Into Graphitic Carbon Quantum Dots by Field‐Induced Electron Localization at Ag Nanoparticles/Electric Double Layer Interface

Converting CO 2 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 CO 2 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] + [BF 4 ] − 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 CO 2 reduction via CO intermediates and C 2 ‐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 CO 2 under ambient conditions. Scaled operation in a 2‐L reactor demonstrates steady g‐CQD production and incorporation of only 0.05 wt.% of the CO 2 ‐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 CO 2 conversion into value‐added carbon nanomaterials.