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

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% CH₄ 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.