Ru Nanowires for Effective Low‐Temperature CO ₂ Methanation in the Aqueous Phase

ABSTRACT The Sabatier reaction is a cornerstone for carbon‐neutral fuel synthesis, yet conventional catalytic systems face persistent challenges: hot‐spot‐driven deactivation due to high operating temperatures (over 473 K), parasitic CO byproducts generated from competing reverse water‐gas shift (RWGS) reactions, and limited catalyst durability under intense exothermic conditions. Here, we present an aqueous‐phase methanation system enabled by grain boundary‐rich ruthenium nanowires (Ru NWs) that overcome these limitations. Three‐dimensional free‐rotating Ru NWs, stabilized by polyvinylpyrrolidone, achieve 99% CH 4 selectivity at just 353 K while fully suppressing undesired RWGS activity. First‐principles simulations reveal that aqueous solvation elevates the energy barriers for *CO desorption and dissociation relative to *HCOO hydrogenation, thereby shifting the reaction pathway decisively toward methanation. This work establishes a new strategy for robust, low‐temperature Sabatier catalysis in water, offering a scalable route for power‐to‐gas applications under mild and sustainable conditions.