Atomically precise Cu 6 nanoclusters for oxygen evolution catalysis: a combined experimental and theoretical study

Abstract Cu‐based nanomaterials have demonstrated great potential as efficient and economic catalysts for oxygen evolution reaction (OER), yet an ideal model catalyst with definitive composition and well‐defined structure is still lacking for understanding the structure–performance relationship at atomical level. Herein, we report the synthesis, structure analysis, and OER catalytic properties of a novel atomically precise Cu nanocluster of [Cu 6 (C≡CR) 4 (dppe) 3 ] (R = Fe(C 5 H 5 ) 2 , abbreviated as Cu 6 NC). Cu 6 NC possesses a unique metal core configuration and metal–ligand binding motifs. Interestingly, Cu 6 NC has superior OER performance to pure phosphine ligand‐protected Cu 18 nanocluster (Cu 18 NC in short, same Cu amount) and Cu nanoparticle (CuNP) with larger size, manifested by the lower overpotential at 10 mA·cm −2 , smaller Tafel slope, and reduced charge transfer resistance. Cu 6 NC also demonstrated excellent long‐term stability for prolonged operation. Density functional theory (DFT) calculations further confirm that the alkynyl ligand plays a critical role in promoting the catalytic performance, and Cu 6 NC has a lower energy barrier in the rate‐determining step of the OER process. This study not only highlights the unique advantages of employing ultrasmall Cu nanoclusters for OER, but also can shed light on designing ligand‐functionalized metal nanoclusters for electrochemical energy conversion and beyond.