Structural dynamics of Ni/Mo2CTx MXene catalysts under reaction modulate CO2 reduction performance

The catalyst’s structural dynamics under reaction conditions critically determine their performance. We proved this indication by studying Ni nanoparticles supported on Mo₂CT_x MXene, where the average size during CO₂ hydrogenation changed from 12.9 to 3.1 nm. A parallel increase of CO selectivity from 21.1% to 92.6% at 400 °C was observed, while the CO₂ conversion rate remained at about 84.0 mmol·g_cat^–1·h^–1. This transformation involved partial removal of Mo₂CT_x terminal groups, allowing direct interaction between Ni and Mo atoms instead of indirect coupling through -O terminations. The shift from a Ni-O-Mo to a Ni-Mo interaction enhanced electron transfer from Ni to Mo₂CT_x, strengthening the metal-support interaction and driving Ni nanoparticle dispersion. In-situ mechanistic analysis and kinetic isotope studies revealed that Ni dispersion suppresses the formate and carboxyl pathway, promotes direct CO₂ dissociation, and inhibits CO hydrogenation, shifting the primary product from CH₄ to CO. These findings provide a strategy for designing highly selective and stable MXene-based catalysts through engineered metal-support interactions.