Substituent effect in determining the total structure of an all-alkynyl-protected Ag98 nanocluster for methanol tolerant oxygen reduction reaction.

Metal nanoclusters (NCs) with atomically precise structures are desirable models for truly understanding their structure-property relationship. This study reports the synthesis and structural anatomy of a Ag98 NC protected solely by an alkynyl ligand, 2-(trifluoromethyl)phenylacetylene (2-CF3PhC[triple bond, length as m-dash]CH), which features a -CF3 substituent at the ortho position (ortho-CF3). 2-CF3PhC[triple bond, length as m-dash]CH ligands are so exquisitely arranged on the surface of Ag98 that the steric hindrance caused by ortho-CF3 is minimized but its function as a hydrogen-bond (H-bond) acceptor (H⋯F) is maximized. Such a rule also applies to inter-cluster interactions which define the stacking sequence of Ag98 NCs. When supported on carbon black, Ag98 NCs demonstrate desirable oxygen reduction activity with robust long-term durability and excellent methanol tolerance, outperforming the commercial Pt/C catalyst.