Defect-Rich and Boron-Doped Al2O3-Supported Ru Nanocatalyst for Enhanced CO2 Methanation Activity

Presently, fabricating a stable and high-performance noble metal catalyst is still a challenging task due to the easy aggregation and growth of metal particles during heterogeneous catalysis reactions. In this regard, catalyst supports always can profoundly impact the metal dispersion and electronic interaction with active metal species, thereby significantly regulating the catalytic performance of catalysts. Herein, a new strategy for fabricating boron-doped alumina support with coordinatively unsaturated penta-coordinated Al3+ (Alpenta3+) sites via a micro-liquid-film reactor-assisted coprecipitation approach was developed. Accordingly, as-formed alumina could efficiently immobilize Ru atoms via the anchoring effect of the Alpenta3+ site to construct a supported Ru catalyst for CO2 methanation. An as-constructed Alpenta3+ site-rich and boron-doped Al2O3-supported Ru nanocatalyst exhibited a better catalytic performance in CO2 methanation along with a higher methane yield of 81.2% under reaction conditions (i.e., 350 °C, 0.1 MPa pressure, and gas hourly space velocity of 6000 mL·gcat–1·h–1), compared to other supported Ru ones over commercial alumina and defect-free alumina. It was demonstrated that the high catalytic performance was closely associated with the coexistence of surface-defective Alpenta3+ sites and B–O species, thereby facilitating the accommodation of active hydrogen species on the support during CO2 hydrogenation as well as the activation adsorption of CO2 at the medium-strength basic sites originating from surface B–O–Al structures. This work provides a new strategy to construct high-performance and stable supported noble metal catalysts through engineering alumina support with special defective structures and surface modification for the applications in advanced heterogeneous catalytic systems.