Explosion-like Redispersion via Ejection of "Hot Molecules" In Situ Generated by Exothermic Reaction.

Abstract

Redispersion of metal catalysts is crucial for enhancing their efficiency and lifecycle in industrial applications. Despite extensive efforts, achieving efficient redispersion of high-loading metal catalysts remains challenging due to limited anchoring sites for dispersed species and insufficient molecular-level understanding of the mechanisms. Herein, an explosion-like redispersion pattern mediated by in-situ-produced "hot molecules" was discovered and illustrated in detail. Unlike traditional redispersion cases through the physical migration of atoms or particles promoted by strong interactions, the reaction of MoO₂ with O₂ was found to be a critical factor to induce this kind of unconventional redispersion driven by a strong thermodynamic force. The intense exothermic reaction resembles an explosion, wherein the produced mono- and multi-nuclear Mo_<i>x</i>O_<i>y</i> clusters with high kinetic energy would be ejected as "hot molecules" and dispersed onto support materials. The metastable hexagonal MoO₂ exhibited an ultrafast redispersion process, enabling the formation of uniformly dispersed subnano MoO₃ species with a loading capacity of up to ∼36.7 wt % on carbon supports. Moreover, this reaction-driven chemical redispersion is found to be extremely efficient and enables processes that are unachievable in the traditional case. It is believed that this work could provide a molecular-level understanding and pragmatic strategy for redispersion processes, which holds great significance for preparing highly efficient catalysts with enormous application potentials.