Breaking the current density bottleneck in electrochemical CO₂ reduction reaction via high-pressure operated Sn single-atom catalysts

Electrochemical carbon dioxide reduction reaction (eCO₂RR) in aqueous media is fundamentally constrained by the low solubility of CO₂, leading to limited current densities and poor product selectivity. Herein, we have developed tin single-atom catalysts (Sn-SACs) featuring well-defined SnN₄ coordination as a platform to systematically investigate the influence of CO₂ pressure on reaction kinetics and selectivity. Elevating the CO₂ pressure to 5 MPa markedly enhances mass transport, achieving a Faradaic efficiency for formate of 85% at −1.1 V vs. RHE with high current density, in stark contrast to 11.5% under 0.1 MPa. In situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) reveals that high pressure favors the formation of *OCHO intermediates, thereby redirecting the reaction pathway toward formate production. Complementary density functional theory (DFT) calculations corroborate that increased local CO₂ concentration stabilizes the *OCHO transition state and lowers the associated energy barrier. This work has established that pressure engineering as an effective strategy to decouple mass transport, activity, and selectivity in eCO₂RR, underscoring the promise of high-pressure electrochemistry for efficient CO₂ conversion.