Thermally Stabilized Hydrogenation Dynamics in Single-Atom Alloys Enables Selective CO ₂ Electroreduction

Electrochemical CO₂ reduction to single-carbon products is central to sustainable fuels and chemicals, but under industrially relevant conditions elevated temperature fundamentally alters reaction behavior and the mechanistic basis for steering hydrogenation of carbon-based intermediates toward selective C₁ formation remains elusive. By integrating artificial intelligence-guided literature mining with theoretical modeling, single-atom alloy catalysts combining thermodynamic advantage with temperature-dependent dynamic surface stability were identified. We report that the coverage and lifetime of surface-active hydrogen (*H) serve as intrinsic, temperature-dependent descriptors for catalyst design, enabling tunable C₁ activity and selectivity under thermally enhanced electrocatalysis. Au₁Cu single-atom alloys are shown to direct CO₂ to either CO or CH₄ via thermally stabilized hydrogenation dynamics; in situ surface-interrogation scanning electrochemical microscopy quantitatively resolves *H coverage and lifetime and links their balance to suppression of hydrogen evolution and promotion of deep hydrogenation to methane. Selectivity was modulated by Au content, delivering about 60% faradaic efficiency for CH₄ at 353 K, whereas higher loadings favored approximately 85-90% CO. Under device-relevant operation and high renewable electricity share, net carbon emissions were reduced relative to conventional electrocatalysis. These findings highlight a quantitative, temperature-explicit mechanistic framework based on *H coverage and lifetime, providing general principles for C₁-selective CO₂ electroreduction and guiding catalyst design beyond room-temperature conditions.