Atomically precise Au15Ag23 nanoclusters co-protected by alkynyl and bromine: Structure analysis and electrocatalytic application toward overall water splitting

We report the structure analysis and electrocatalytic application toward overall water splitting of atomically precise Au 15 Ag 23 ( t BuC ≡ C) 18 Br 6 nanoclusters (Au 15 Ag 23 in short). Au 15 Ag 23 possesses a triple-layered core-shell-shell metal core structure of Au 6 @Au 6 Ag 23 @Au 3 , with the core centre being a tetragonal bipyramidal Au 6 structure unit, and the outer layer of one Ag atom linked with two alkynyl ligands to form a linear structural motif covering the surface of the metal nucleus. Au 15 Ag 23 is a superatom with 14 free electrons and it displays a unique absorption profile. Remarkably, the Au 15 Ag 23 catalyst exhibits excellent electrocatalytic properties in hydrogen evolution reaction (HER), manifested by a low overpotential of 125 mV at 10 mA cm −2 and a negligible current decrease for 16 h in 0.5 M H 2 SO 4 , while the Au 15 Ag 23 /NiFe-LDH catalyst demonstrates outstanding electrocatalytic performance in oxygen evolution reaction (OER), evidenced by an ultralow overpotential of 250 mV at 10 mA cm −2 and a ∼5% current decrease for 30 h in 1.0 M KOH. Such promoting effect is ascribed by the electron transfer from NiFe-LDH to the Au 15 Ag 23 clusters, which results in generating high valent Fe species as active sites. When using the two catalysts for overall water splitting (OWS), only 1.51 V was required to achieve a current density of 10 mA cm −2 , and it performed well in the 50 h's stability test. This study enriches the family member of alkynyl-protected AuAg bimetallic nanoclusters, and further highlights the dual functionalities (catalyzing HER and promoting OER) that metal nanoclusters can make contribution for electrochemical energy conversion and beyond.