Restructuring of nanoporous gold surfaces during electrochemical cycling in acidic and alkaline media

The electrochemical behavior of nanoporous gold (NPG) obtained by dealloying a AgAu alloy has been investigated by means of cyclic voltammetry (CV) in 0.1 M H2SO4 and 0.1 M KOH solutions supplemented by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) in order to understand different effects of the electrochemical treatment on the development of the surface structure of NPG. In order to reduce the IR drop caused by the high surface area of the bicontinuous network of pores and ligaments in NPG, NPG was transformed to a powder, from which a small portion was filled into a cavity microelectrode (CME). Additionally, this avoided sample-to-sample variation from the dealloying process because many fillings could be made from one NPG monolith. The cycling in 0.1 M H2SO4 led to restructuring of the surface to a more faceted one, only after the residual silver on the surface had been removed in the initial scan. The same cycling program in 0.1 M KOH did not cause restructuring. However, a transfer of the sample to 0.1 M H2SO4 could start the process. The ligament size did not change during restructuring. Additionally, it was found that residual Ag in NPG stabilizes the highly curved surfaces of the ligaments containing a high density of surface defects. The dissolution of the residual Ag in acid electrolytes lifts the blockage towards surface restructuring. These findings form a basis for understanding the electrochemical behavior of NPG and to devise appropriate treatments, for instance for their use in electrocatalysis.

Subjects

coarsening

electrocatalysis

electrochemical cycling

nanoporous gold

restructuring

DDC Class

530: Physik

540: Chemie

600: Technik

More Funding Information

The authors thank Deutsche Forschungsgemeinschaft for funding within the Research Group FOR2213-255613253 [subprojects 3 and 4]. Furthermore, funding is acknowledged for the SEM for the central facilities of the School of Mathematics and Science by the DFG (INST 184/107-1 FUGG) and for XPS instrumentation (INST 184/144-1 FUGG). Open access funding enabled and organized by Projekt DEAL.

Publication version

publishedVersion

Lizenz

https://creativecommons.org/licenses/by/4.0/

Name

celc.202000923.pdf

Size

2.41 MB

Format

Adobe PDF

Options

Restructuring of nanoporous gold surfaces during electrochemical cycling in acidic and alkaline media