Domain Size Dependence of the Oxygen Reduction Reaction on (100)-Oriented Au Thin Films
Authors: Soares Cybelle Palma de Olivera , Buvat Gaëtan , Denuault Guy , Tavares Ana C , Guay Daniel 
Published: May 2020

Due to its importance for energy conversion and storage, the oxygen reduction reaction (ORR) is one of the most studied electrochemical reactions. It has been reported that, in alkaline media, Au(100) single crystal is the most active electrocatalyst for the ORR1,2. Different reasons have been proposed to explain this high activity3,4. Understanding this remarkable activity can guide researchers in the design of more active electrocatalysts for practical applications using nanomaterials with specific shape and size. Since the ORR is a structure-sensitive reaction5–7 the manipulation of the structural properties of the materials is a powerful tool to elucidate the reaction mechanism responsible for the ORR and increase the activity of materials towards the reaction.
In this work, (100)-oriented Au thin films were deposited on (100) MgO. Thin films with different thicknesses were prepared by pulsed laser deposition and were used as model surfaces to study the ORR activity. Pulsed Laser Deposition (PLD) is a versatile method to prepare thin films with different surface orientations (epitaxial thin films)8,9
,
10. The structure and microstructure of the films were assessed by X-Ray Reciprocal Space Mapping (RSM) and Atomic Force Microscopy (AFM). There results were correlated with those obtained from Cyclic Voltammetry (CV) and Sampled Current Voltammetry (SCV).
The ORR activity was observed to be dependent on the film thickness, which is reflected by the shift of the onset and half-wave potentials of the ORR towards more positive potentials for the thicker films. When correlating the ORR activity with the structural and microstructural properties, Fig.1, the evidences suggest that larger lateral coherent lengths are responsible for the enhancement of the ORR catalysis on (100)-oriented Au thin films. The reasons underlying this behavior will be presented and discussed.

Figure 1: Plot showing the variation of the onset and half-wave potential, and the variation of the coherence length for thin films of various thicknesses.

References

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Figure 1