Ensembles of metastable states of size-selected cluster catalysts determine activity and selectivity

Supported size-selected cluster catalysts are highly fluxional, and easily isomerize and/or change composition in reaction conditions, under the influence of temperature, electrochemical potential, binding and changing reagents and reaction intermediates, as well as the momentum exchange with hot reagents arriving at their surfaces. As a result, a dynamic ensemble of many catalysts states forms in reaction conditions, giving rise to many reaction pathways, and various channels enabling reactivity, selectivity, or catalyst degradation. The most stable cluster species, while dominant in the population and responsible for the majority of operando spectral signatures, can play a much lesser role in the actual catalytic chemistry, where instead, the less stable species typically turn out more reactive, prone to poison binding, or dissociation and sintering initiation. This majorly updated theory of cluster-based catalytic interfaces will be illustrated on several examples of pure and alloyed supported Pt clusters catalyzing hydrocarbon dehydrogenation.