Electrochemically Tunable Resistance of Nanoporous Metals Produced by DealloyingWednesday (28.09.2016) 15:30 - 15:45 Part of:
Dealloying is an (electro-)chemical process in which the less noble component is removed from a master alloy by selective etching, resulting in a nanoporous structure of the more noble element . The particular properties of nanoporous metals produced by this method find application in various fields of research such as sensing, energy storage, or (electro-)catalysis. The extraordinary high surface-to-volume ratio makes nanoporous materials also predestined systems for property tuning by means of electrochemical charging since charging-induced surface modifications may affect a considerable fraction of the bulk material .
In the present work nanoporous platinum, gold and palladium with high specific surface areas up to 30 m²/g are produced by dealloying. Resistometry performed upon electrochemically induced ad-/desorption processes in an aqueous electrolyte reveals relative variations of the electrical resistance of the nanoporous metals up to more than 50%. Due to the high surface-to-volume ratio, this variation is about an order of magnitude higher than that measured under similar conditions for porous nanocrystalline Pt samples made from commercial Platinum Black. The resistance variation is considered to arise primarily from charging-induced variations of the charge-carrier scattering at the metal-electrolyte interfaces. For the as-dealloyed state of nanoporous platinum, a sign-inverted resistance-to-charge response can be observed  which is associated with the semiconducting nature of PtO formed during dealloying. Differences in the charging sensitivity of the electrical resistance of nanoporous Pt and Au will be discussed. Electrical resistance measurements are further applied to monitor the evolution of the nanoporous structure during dealloying.
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