DNA origami as an electronically coupled scaffold for Au nanocluster electrocatalysts.

Abstract

Ultra-small, atomically precise gold nanoclusters (Au NCs) offer distinctive opportunities for electrocatalysis owing to their discrete electronic structures and high density of coordinatively unsaturated sites; however, uncontrolled aggregation and the absence of spatial control over cluster nucleation on conventional supports remain significant challenges for the rational engineering of catalytic interfaces. Herein, we report a site-directed, in situ strategy for the spatially controlled synthesis of Au NCs on DNA origami (Au NC@DNA) scaffolds, which function as localized nucleation and coordination platforms to afford Au NC@DNA origami hybrid architectures. The resulting hybrids exhibit a narrowly distributed Au NC size of 1.5 ± 0.2 nm, as established by complementary UV-vis and fluorescence spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). When evaluated for the hydrogen evolution reaction (HER) in 0.5 M H₂SO₄, the Au NC@DNA origami hybrid exhibits a low overpotential of 87 mV at a current density of -10 mA cm^-2, together with a Tafel slope of 67 mV dec^-1, a charge-transfer resistance of 13.87 Ω, and a mass activity of 416.3 A g^-1. These electrocatalytic metrics substantially exceed those of Au NC@Poly-C, pristine DNA origami, and poly-cytosine (poly-C) controls and approach the performance of the benchmark Pt/C catalyst. Furthermore, the Au NC@DNA origami catalyst demonstrates pronounced operational durability, maintaining its electrocatalytic activity over 3000 continuous linear sweep voltammetry cycles and 36 h of chronoamperometric operation. Density functional theory (DFT) calculations identify the DNA-Au₂₁ configuration as a thermodynamically favorable catalytic motif, characterized by a near-thermoneutral Gibbs free energy of hydrogen adsorption (ΔG_H*). Bader charge analysis and projected density of states (PDOS) further reveal substantial electronic coupling between the Au cluster and DNA ligand, accompanied by Au-H orbital hybridization and charge redistribution involving neighbouring N/O coordination sites. These results demonstrate that DNA origami functions not merely as a structural template but as an electronically coupled and catalytically relevant scaffold that modulates the physicochemical properties of atomically precise Au nanoclusters.