Adsorption of O2 on anionic silver clusters: spins and electron binding energies dominate in the range up to nano sizes

Exploring the reactivity of metal clusters is an important task in cluster science, while only a few previous studies involve the reactions of nano-sized ones. Here we report a kinetic measurement on reactions of Ag-n(-) (n = 6-69) with O-2 using a flow reactor running at 120 K. Their relative rates were obtained by fitting decay processes of parent ions at different O-2 flow rates. Comparing the variations of the kinetic rates and the photodetachment energies of Ag-n(-) (i.e. the binding energies of their excess electrons), we distinguished the separate effect of clusters' spins or their electron binding strength. This work firstly shows that reactions of O-2 and Ag-n(-) up to nano sizes are still dominated by the clusters' global electronic properties. This conclusion is conceptually important for understanding the reaction mechanisms on silver based nanocatalysts.