Oxygen Activation Mechanisms on AuₓCuᵧ Surfaces: A DFT Perspective

1. Introduction

Bimetallic Au–Cu surfaces exhibit tunable catalytic properties that are highly sensitive to surface composition and atomic arrangement. Cu incorporation into Au modifies oxygen activation pathways and reactive oxygen species (ROS) generation, which are central to catalytic and antimicrobial functionalities. Atomistic understanding of these effects is essential for the rational design of Au–Cu nanomaterials. In this work, we investigate these effects at the atomic level using density functional theory (DFT) calculations to elucidate how surface composition and atomic arrangement in Au–Cu systems govern oxygen activation and ROS formation.

2. Methods

Density functional theory (DFT) calculations were performed to investigate oxygen reduction reaction (ORR) mechanisms on Au_xCu_y model surfaces with systematically varied Cu content. Periodic Au(111) slab models were constructed with surface and subsurface Cu incorporation to represent different Au_xCu_y compositions. Adsorption geometries and free energies of key ORR intermediates (O*, O*, OOH*, OH*, and H₂O₂*) were determined. Activation barriers for O–O and OOH bond dissociation were calculated, together with charge transfer, O–O bond lengths, vibrational frequencies, and d-band electronic structure analysis.

3. Results

The calculations reveal that Cu incorporation substantially strengthens oxygen adsorption and lowers O–O bond dissociation barriers relative to pristine Au surfaces. Au-rich Au_xCu_y models favor stabilization of molecular intermediates and H₂O₂ formation, while Cu-enriched surfaces promote deeper oxygen activation and facile O–O cleavage. Charge transfer analysis indicates enhanced metal-to-oxygen electron donation with increasing Cu content, accompanied by d-band centre shifts towards the Fermi level and progressive O–O bond weakening.

Conclusions

The DFT results demonstrate that surface composition in Au_xCu_y systems critically governs oxygen activation and ROS-related pathways. The atomistic insights provided here establish clear design principles for tailoring Au–Cu bimetallic surfaces with controlled reactivity through precise compositional engineering.