摘要
Integrating multiple active sites within a single catalytic system has emerged as a promising strategy to unlock new performance windows in heterogeneous catalysis. Herein, we report a novel design configuration of a heterogeneous catalyst co-loaded with Ni single atoms and NiO nanoparticles on the oxygen-deficient TiO2 support, denoted as Ni-SA+NP, for highly efficient CO2 methanation. This tandem system achieves an unprecedented CH4 production yield of similar to 4,658 mu mol g(-1) at 573 K with a CH4 production rate of similar to 16768 mmol g(-1) h(-1) and CH4 selectivity of 90%, significantly surpassing the performance of catalysts containing only Ni single atoms (similar to 2,794 mu mol g(-1) at 573 K) and NiO nanoparticles (similar to 4,018 mu mol g(-1) at 573 K). While Ni single atoms offer excellent atomic dispersion and strong metal-support interaction, they often suffer from oxidation and a lack of ensemble sites, which limits multistep reaction kinetics. Our strategy addresses these limitations by creating oxygen vacancies in oxidized Ni single atoms and providing ensemble sites (adjacent NiO nanoparticles and oxygen-deficient TiO2 support), thereby enabling a synergistic interaction between oxygen vacancies in Ni single atoms/TiO2 support and adjacent NiO nanoparticles. The results of in situ X-ray absorption spectroscopy reveal that the oxygen vacancies in Ni single atoms and TiO2 support facilitate the CO2 activation, whereas the adjacent NiO nanoparticles interacts with H-2 molecules (Ni-O-ads + H-2 -> Ni + H2O) and undergo reduction to metallic Ni during CO2 methanation. This multiple-site architecture creates a highly active interface for CO2 activation and hydrogenation, setting a new benchmark for methanation catalysis and providing a scalable blueprint for hybrid single-atom/nanoparticle catalyst design.