Room-Temperature Adsorption on Magnetite Induces Spontaneous Fragmentation of Early Transition-Metal Size-Selected Nanoclusters

The stability of supported metal nanoclusters, namely, their ability to preserve structure, composition, and catalytic activity over time, is a fundamental prerequisite for catalyst durability, resistance to deactivation, and long-term performance under operating conditions. Despite their often-exceptional intrinsic activity, nanoclusters are particularly susceptible to structural evolution driven by strong metal–support interactions. Here, we demonstrate that size-selected early transition-metal nanoclusters (W, Mo, and Ta) soft-landed on reconstructed Fe3O4(001) undergo spontaneous breakdown already at room temperature, in the absence of thermal activation or reactive gas environments. Combining high-energy resolution photoelectron spectroscopy and scanning tunneling microscopy with density functional theory, we show that strong metal–oxygen bonding, together with reconstruction-induced surface defects of the oxide support, provides the driving force required to overcome metal–metal cohesion within the clusters, leading to their dissociation. Upon further oxidation, an enhanced degree of atomization is produced, particularly for larger clusters, yielding highly dispersed metal species. The propensity for fragmentation, i.e., the partial or total breaking of metal–metal bonds in the cluster, follows the trend Ta > W > Mo, which correlates closely with metal oxophilicity, adsorption energies, and intrinsic metal–metal bond strengths. These findings establish adsorption-induced fragmentation of metal nanoclusters as an intrinsic manifestation of metal–support interactions for early transition metals on reducible oxides. More broadly, they reveal a spontaneous room temperature pathway to cluster destabilization and identify an innovative strategy for the controlled generation of high densities of single metal atoms from well-defined nanocluster precursors.