CO₂-to-CO Electrolysis in Pure Water at Ampere-Level Current Density and 1000 h Stability via a Rapid-Transport...

Electrochemical reduction of CO₂ to CO offers a sustainable pathway to syngas for synthetic fuels and chemicals. Conducting CO₂ electrolysis in pure water simplifies system design and avoids salt precipitation, yet its performance is constrained by sluggish reaction kinetics and limited selectivity. To address these challenges, we constructed a rapid-transport fixed-charge interface (RTFC-I) via electrochemical reconstruction of a polymer-modified Ag electrode, yielding a nanostructured surface coated with a quaternary ammonium polymer layer. This design creates rapid mass transport channels and a positively charged microenvironment, which stabilizes critical reaction intermediates while restricting proton transport. The optimized electrode achieves a CO Faradaic efficiency (FECO) of ∼99% at 500 mA cm^-2 (25°C), and maintains 76.4% FECO at 1.0 A cm^-2 (60°C). It also exhibits stable continuous operation for 1000 h, along with excellent scalability, as validated in an integrated three-cell stack featuring a total active area of 960 cm². In situ Fourier-transform infrared (FTIR) spectroscopy, differential electrochemical mass spectrometry (DEMS), and density functional theory (DFT) calculations verify that the RTFC-I reduces the energy barrier for *COOH formation and enhances CO₂ reduction activity. This work validates fixed-charge nanostructured interfaces as a robust strategy for alkaline-free CO₂ electrolysis in pure water.