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

Abstract

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-CF₃PhCCH), which features a –CF₃ substituent at the ortho position (ortho-CF₃). 2-CF₃PhCCH 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.