Size-Dependent Reactivity of Co _n ^- (n=5-25) Cluster Anions toward Carbon Dioxide

A fundamental understanding of the reactivity evolutionof nanosizedclusters at an atomically precise level is pivotal to assemble desiredmaterials with promising candidates. Benefiting from the tandem massspectrometer coupled with a high-temperature ion-trap reactor, thereactions of mass-selected Co- n (-) (n = 5-25) clusters with CO2 wereinvestigated and the increased reactivity of Co20-25 (-) was newly discovered herein. This finding marksan important step to understand property evolution of subnanometermetal clusters (Co-25 (-), & SIM;0.8 nm)atom-by-atom. The reasons behind the increased reactivity of Co20-25 (-) were proposed by analyzingthe reactions of smaller Co6-8 (-) clusters that exhibit significantly different reactivity towardCO(2), in which a lower electron affinity of Co- n contributes to the capture of CO2 whilethe flexibility of Co- n (-) could play vital roles to stabilize reaction intermediates and suppressthe barriers of O-CO rupture and CO desorption.