Competitive Hydration Versus Migration of Pre‐hydrated Electrons for CO₂ Reduction in Aqueous Solution Revealed by Ab Initio Molecular Dynamics Simulation

Abstract

Photoinjected excess electrons (EEs) can fulfill the direct reduction of CO2 (CO2R) in an aqueous solution. However, the underlying mechanism is still poorly understood, especially the EE dynamics, which govern reaction mechanisms. Here, using a hybrid functional‐based ab initio molecular dynamic simulation strategy, it accurately characterizes the dynamics details of CO2R by aqueous EEs in solution and uncovers the nature of how EEs migrate for efficient CO2R. The AIMD simulations reveal that the injected EEs undergo hydration with diverse hydrated forms (various pre‐hydrated/e−pre/e22−pre and hydrated/e−aq/e22−aq) and multiple reaction channels due to competition of hydration versus migration. Interestingly, all pathways go through the same relay state [CO22−]aq and reach the same product (HCOO−). The core process before [CO22−]aq is competitive electron hydration and possible e−pre‐migration featuring either slowly flowing or fast jumping mode, while that after [CO22−]aq is proton transfer catalyzed by H‐bonding network as a proton source. The nature is how the concerted hydration dynamics of EEs and target CO2 govern the reaction proceeding through modulating their energy gap . This study provides dynamics insights into CO2R in aqueous solution by diverse e−pre/e−aq and the proposed strategy can also be utilized to explore the reduction mechanisms based on pre‐solvated electrons in other media.