Formation and Tunable Properties of Dealloyed Nanoporous Metals Studied by In-Situ Resistometry

Description

Nanoporous (np) metals produced by dealloying, a selective (electro-)chemical etching process, exhibit a high surface-to-volume-ratio and macroscopic sample sizes in three dimensions. This unique combination makes np-metals attractive for basic research as well as technology applications such as sensing, energy storage or (electro-)catalysis.
Various parameters of the dealloying process may sensitively influence the outcoming nanostructure. In the present work, the etching process of np-Au and np-Pt is investigated in-situ by resistometry, dynamically monitoring the entire macroscopic sample. This perfectly complements earlier studies, which were either performed ex-situ and/or restricted to microscopic portions of material.
During dealloying, the resistance increases by about three orders of magnitude. A model is developed which describes the observed characteristics to be governed by the dissolution of the master alloy in favor of the nanoporous structure. In agreement with earlier ex-situ SEM studies [2], the etching is shown to proceed in two stages, i.e., ’primary (or bulk) dealloying’ and ’secondary (or ligament) dealloying’.
The high achievable specific surface area up to 30 m²/g, also makes the dealloying process an ideal method for the preparation of nanostructures with electrochemically tunable properties, following the concept of Gleiter et al [3]. By electrochemical ad-/desorption, which strongly influences interfacial charge carrier scattering, reversible resistance variations up to several tens of percents can be generated [4]. This tunability exceeds that of porous nanophase platiunum prepared by compaction of Pt nanopowder [5] by an order of magnitude, which can be attributed to the extraordinarily high surface-to-volume ratio of dealloyed metals.

[1] J. Erlebacher et al., Nature 410 (2001) 450
[2] X. Ye et al., J. Electrochem. Soc, 161 (2014) C517
[3] H. Gleiter et al., Acta Mater. 49 (2001) 737
[4] E.-M. Steyskal et al., Langmuir 32 (2016) 7757
[5] E.-M. Steyskal et al., Beilstein J. Nanotechnol. 4 (2013) 394

Period	18 Sept 2017
Event title	European Congress and Exhibition on Advanced Materials and Processes: Euromat 2017
Event type	Conference
Location	Thessaloniki, GreeceShow on map
Degree of Recognition	International