Ru Single-Atom-Nanoparticle Synergy Induces Interfacial Electron Redistribution for Complete Selectivity Reversal in CO2 Hydrogenation

Achieving controllable selectivity reversal for CO2 hydrogenation is a major challenge in low-carbon catalysis. Herein, ruthenium single atoms are anchored on TiO2 oxygen vacancies to form tight single-atom-nanoparticle interfaces at ∼0.83 wt % Ru loading, enabling complete product switching. RuNP/TiO2 predominantly produces CO via reverse water–gas shift, while RuSA+NP/TiO2 achieves ∼100% CH4 selectivity from 250 to 400 °C. Combined in situ spectroscopic characterization and DFT calculations reveal a temperature-dependent dual reaction pathway: low-temperature CH4 formation is dominated by the CO*-mediated hydrogenation pathway, while the HCOO*-mediated pathway gradually governs the reaction at high temperatures. The coexistence of Ru single atoms and nanoparticles optimizes interfacial electronic distribution, accelerates CO2 activation and H* spillover, and stabilizes the SA–NP synergistic active structure during long-time testing. This work elucidates the structure-performance relationship of dual-type Ru active sites and provides a rational design strategy for high-efficiency CO2 methanation catalysts.