Charging properties of gold clusters in different environments

The charge-dependent capacitance of gold clusters in the gas phase, protected by ligands and stabilized in ionic liquids, is investigated using density functional theory. For strong compounds such as naked or monolayer protected clusters, structural relaxation due to charging is effective only for very small species. The charge-dependent capacitance is mainly governed by two distinct electronic factors: the change in the effective charge centroid and the strong influence of electronic shell closings of the delocalized electrons. Both effects can be found and explained from within a simple jellium model. In contrast, soft compounds between gold clusters and ionic liquids undergo a structural reorganization during the charging process which results in a pronounced peak in the capacitance at zero charge.