Mesoporous Confinement of Ni Nanoparticles in Al2O3 Enables Highly Selective CO Production via Reverse Water–Gas Shift Reaction

Nickel-based catalysts have been extensively investigated for the reverse water–gas shift (RWGS) reaction; however, their practical application is often hindered by the undesired methanation side reaction. To address this challenge, we developed mesoporous Al2O3 as a support to disperse and spatially confine Ni nanoparticles. Ni/Al2O3 catalysts were synthesized via two strategies: pre-introduction of the Ni precursor during the sol–gel formation of mesoporous Al2O3 and post-impregnation of the Ni precursor onto preformed mesoporous Al2O3. Compared with Ni supported on conventional γ-Al2O3, both catalysts exhibited lower CO2 hydrogenation activity but significantly improved CO selectivity. Through a combination of structural characterizations and kinetic analyses, we revealed that pre-introduced Ni species were transformed into smaller Ni nanoparticles confined within the mesoporous channels, accompanied by stronger metal-support interactions. These structural features did not alter the intrinsic RWGS reaction but effectively suppressed the competing methanation reaction, thereby achieving superior CO selectivity. This study demonstrates that rational regulation of support morphology and control over metal incorporation strategies provide an effective approach for steering CO2 hydrogenation toward selective CO production.