High Throughput Correlative Electrochemistry-Microscopy Analysis on a Zn-Al Alloy

Gunani Jayamaha; Levi Tegg; Cameron L Bentley; Minkyung Kang

doi:10.1021/acsphyschemau.4c00016

High Throughput Correlative Electrochemistry-Microscopy Analysis on a Zn-Al Alloy

ACS Phys Chem Au. 2024 May 10;4(4):375-384. doi: 10.1021/acsphyschemau.4c00016. eCollection 2024 Jul 24.

Authors

Gunani Jayamaha¹, Levi Tegg², Cameron L Bentley³, Minkyung Kang¹

Affiliations

¹ School of Chemistry, The University of Sydney, Camperdown, New South Wales 2006, Australia.
² School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Camperdown, New South Wales 2006, Australia.
³ School of Chemistry, Monash University, Clayton, Victoria 3800, Australia.

Abstract

Conventional electrodes and electrocatalysts possess complex compositional and structural motifs that impact their overall electrochemical activity. These motifs range from defects and crystal orientation on the electrode surface to layers and composites with other electrode components, such as binders. Therefore, it is vital to identify how these individual motifs alter the electrochemical activity of the electrode. Scanning electrochemical cell microscopy (SECCM) is a powerful tool that has been developed for investigating the electrochemical properties of complex structures. An example of a complex electrode surface is Zn-Al alloys, which are utilized in various sectors ranging from cathodic protection of steel to battery electrodes. Herein, voltammetric SECCM and correlative microstructure analysis are deployed to probe the electrochemical activities of a range of microstructural features, with 651 independent voltammetric measurements made in six distinctive areas on the surface of a Zn-Al alloy. Energy-dispersive X-ray spectroscopy (EDS) mapping reveals that specific phases of the alloy structure, particularly the α-phase Zn-Al, favor the early stages of metal dissolution (i.e., oxidation) and electrochemical reduction processes such as the oxygen reduction reaction (ORR) and redeposition of dissolved metal ions. A correlative analysis performed by comparing high-resolution quantitative elemental composition (i.e., EDS) with the corresponding spatially resolved cyclic voltammograms (i.e., SECCM) shows that the nanospot α-phase of the Zn-Al alloy contains high Al content (30-50%), which may facilitate local Al dissolution as the local pH increases during the ORR in unbuffered aqueous media. Overall, SECCM-based high-throughput electrochemical screening, combined with microstructure analysis, conclusively demonstrates that structure-composition heterogeneity significantly influences the local electrochemical activity on complex electrode surfaces. These insights are invaluable for the rational design of advanced electromaterials.