Coupling Atomic Confinement With CO₂ Pressure for Selective and Stable CO₂ Electroreduction

Electrochemical reduction of CO₂ (CO₂RR) offers a promising route to convert waste carbon into valuable chemical feedstocks while mitigating greenhouse emissions. However, achieving high activity and selectivity in CO₂RR remains challenging due to the low solubility of CO₂ 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 CO₂RR reaction maintained stable performance for 40 h. The synergy between atomic-scale confinement and CO₂ pressurization enhances CO₂ availability, suppresses HER, and promotes CO formation through a *COOH-mediated pathway. This work establishes a general strategy for tuning CO₂ electroreduction pathways by integrating nanoscale structural confinement with controlled reaction environments.