Activity: Talk or presentation › Talk at conference or symposium › Science to science
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 , 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 . By electrochemical ad-/desorption, which strongly influences interfacial charge carrier scattering, reversible resistance variations up to several tens of percents can be generated . This tunability exceeds that of porous nanophase platiunum prepared by compaction of Pt nanopowder  by an order of magnitude, which can be attributed to the extraordinarily high surface-to-volume ratio of dealloyed metals.
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