Coupling Atomic Confinement With CO 2 Pressure for Selective and Stable CO 2 Electroreduction

ABSTRACT Electrochemical reduction of CO 2 (CO 2 RR) offers a promising route to convert waste carbon into valuable chemical feedstocks while mitigating greenhouse emissions. However, achieving high activity and selectivity in CO 2 RR remains challenging due to the low solubility of CO 2 in aqueous electrolytes and competing hydrogen evolution reactions (HER) that limit efficiency under practical conditions. Here, we address these limitations by coupling high‐pressure operation with atomic‐scale catalyst design. A tin oxide (SnO x ) nanoparticle catalyst featuring sub‐nanometer interplanar gaps (< 1 nm) was synthesized via an electrochemical cation implantation (ECI) process to create confined reaction environments. The resulting ECI(S)–SnO x achieved a Faradaic efficiency for CO (FE CO ) of 69.2% and a current density of –11.2 mA cm −2 at –3.0 V under 7.4 MPa. Additionally, the CO 2 RR reaction maintained stable performance for 40 h. The synergy between atomic‐scale confinement and CO 2 pressurization enhances CO 2 availability, suppresses HER, and promotes CO formation through a *COOH‐mediated pathway. This work establishes a general strategy for tuning CO 2 electroreduction pathways by integrating nanoscale structural confinement with controlled reaction environments.