Atomically precise Cu6 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 [Cu₆(C≡CR)₄(dppe)₃] (R = Fe(C₅H₅)₂, abbreviated as Cu₆NC). Cu₆NC possesses a unique metal core configuration and metal–ligand binding motifs. Interestingly, Cu₆NC has superior OER performance to pure phosphine ligand-protected Cu₁₈ nanocluster (Cu₁₈NC 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. Cu₆NC 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 Cu₆NC 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.

Graphical abstract