Hcp-Ni derived highly dispersed and stable Ni/Al2O3 catalysts for CO2 methanation

Metastable hcp-Ni enables the synthesis of highly dispersed and stable Ni/Al 2 O 3 catalyst • Highly dispersed Ni/Al 2 O 3 catalyst delivers 75.7% CO 2 conversion and 100-h stability • Original hcp-Ni particles spontaneously transform into fcc-Ni clusters of ∼2.3 nm • Small Ni clusters promote CO 2 methanation via monodentate formate intermediate • Fcc-Ni precursors undergo severe sintering to ultra-large and less-active particles Ni-based catalysts are promising candidates for CO 2 methanation while their practical applications are limited by particle agglomeration and deactivation. Here, we report a facile strategy to fabricate a highly dispersed and stable Ni/Al 2 O 3 catalyst using metastable hexagonal close-packed (hcp)-Ni as a precursor. Comprehensive characterization reveals that the initial hcp-Ni (∼12.0 nm) spontaneously transforms into uniform face-centered cubic (fcc)-Ni nanoparticles (NPs) of ∼2.3 nm on γ -Al 2 O 3 support during H 2 reduction and CO 2 methanation reaction. The small Ni particles contribute to improved Ni 0 proportion on catalyst surface. In contrast, the original fcc-Ni precursors are prone to sintering, forming ultra-large and less-active Ni aggregates. The highly dispersed Ni NPs derived from hcp-Ni enhance CO 2 adsorption-activation and facilitate the formate-mediated reaction pathway. The resulting hcp-Ni/Al 2 O 3 catalyst delivers a CO 2 conversion of 58.2% with a CH 4 selectivity of 85.4% at 460 °C and endows robust stability exceeding 100 hours. The optimal CH 4 space time yield reaches 179.5 mmol·g cat −1 ·h −1 , exceeding 2.4 times that of fcc-Ni/Al 2 O 3 . This work establishes a reliable synthesis paradigm rooted in crystal-phase regulation, enabling the manufacture of highly dispersed and stable Ni-based catalysts for efficient CO 2 methanation. Manufacturing Highly Dispersed and Stable Ni/Al 2 O 3 Catalysts from hcp-Ni for Enhanced CO 2 Methanation Download: Download high-res image (221KB) Download: Download full-size image