Switching CO ₂ Electroreduction Pathways via Polyvinylpyrrolidone‐Mediated Water Configuration Control

The water configuration plays a critical role in steering the CO₂ electroreduction pathway, yet achieving precise control over water arrangement remains a significant challenge. In this study, we demonstrate that introducing trace amounts of polyvinylpyrrolidone (PVP) into 3 M KCl enables targeted control over the CO₂ electroreduction product distribution by simply adjusting the PVP concentration. Using a Cu₁₉CeO_x (molar ratio of Cu:Ce = 19:1) electrode, in the absence of PVP, multicarbon (C₂₊) products dominate, but substantial CO and H₂ are also generated, with negligible CH₄ formation. Remarkably, the addition of just 25 ppm PVP shifts the primary product to CH₄, achieving a Faradaic efficiency (FE) of 60.4% at 500 mA cm^-2. Further increasing the PVP concentration to 125 ppm switches the dominant product back to C₂₊, with an impressive FE of 90.8% at 800 mA cm^-2. This trend is consistent across various Cu-based catalysts, highlighting the universality of this approach. Mechanistic studies reveal that PVP reconstructs the water configuration at the cathode surface, modulating not only the adsorption strength and coverage of *CO intermediates but also the kinetics of water dissociation, thereby dictating the reaction pathway.