Enhanced Photo‐Thermal CO2 Methanation with Tunable RuxNi1‐x Catalytic Sites: Alloying Beyond Pure Ru

Developing solid‐solution nano‐alloys from immiscible metals has garnered significant interest; however, the high formation entropy poses substantial challenges in synthesis, hindering a comprehensive understanding of the catalytic mechanisms under alloying effects. Herein, the synthesis of small‐sized (≈2.5 nm) RuxNi1‐x solid‐solution alloy nanoparticles with precisely controlled Ru/Ni ratios across a broad compositional range is reported for the first time, despite their bulk immiscibility. The Ru0.76Ni0.24/TiO2 catalyst, with an optimized Ru/Ni ratio, delivers superior photo‐thermal catalytic activity for CO2 methanation, achieving a CH4 production rate of 3.58 mol gmetal−1 h−1 with 94% selectivity at 250 °C under light irradiation, representing a 2.82‐fold enhancement over monometallic Ru/TiO2. Comprehensive investigations reveal that the reconstruction of electronic structure at Ru–Ni active sites enhances the adsorption/activation of reactants, promotes the transformation of intermediate HCO3* to HCOO*, and facilitates the separation of the photo‐generated charge carriers witnessed by the femtosecond time‐resolved transient absorption (fs‐TA) spectroscopy. These combined effects collectively result in significantly enhanced CH4 formation performance. This work highlights the potential of regulating catalytic sites in immiscible metal combinations for photo‐thermal catalytic CO2 conversion, underscoring the promise of these cost‐effective alloys in heterogeneous catalysis.