DescriptionThe palladium-hydrogen system has been an extensively studied model system for hydrogen absorption in bulk metals over many decades. With nanoporous palladium structures (np-Pd), e.g. prepared via selective etching by electrochemical dealloying, extraordinarily fast hydrogen sorption can be achieved due to the high surface to volume ratio. Modern technological application potentials of np-Pd range from hydrogen storage and sensing to (electro-)catalysis and low-voltage actuation.
In previous studies, an extraordinarily strong expansion of more than 5% was achieved for np-Pd upon electrochemical hydrogen absorption . Here we present a systematic dilatometric investigation of actuation under different hydrogenation conditions. The nanoporous samples, which are prepared by dealloying Co-Pd master alloys , are charged at different potentials (and thus sorption rates) in a variety of electrolytes covering a broad spectrum of pH values from strongly acidic to strongly alkaline.
The dilatometric data allow a clear distinction between hydrogen adsorption at the surface and hydrogen absorption into the bulk, which leads to strong actuation. The severe, continuous degradation of np-Pd, which was observed recently upon charging in acidic media , can be explained based on dilatometric data recorded in different electrochemical regimes. Aqueous KOH solution is shown to be an ideal electrolyte for efficient charging while avoiding degradation or dissolution.
A spontaneous material failure under the pressure of the dilatometer pushrod is observed during charging-induced actuation at very high strain rates. The underlying mechanisms will be discussed with regards to hydrogen sorption mechanisms, H-concentration profiles as well as a possible strain-rate dependence of the yield strength.
 E.-M. Steyskal et al., Beillstein J. Nanotechnol. 7 (2016) 1197
 M. Hakamada et al., J. Alloy. Compd. 479 (2009) 326
 J. Zhang et al., Electrochim. Acta 220 (2016) 91
|Period||16 Sep 2017 → 21 Sep 2017|
|Event title||European Congress and Exhibition on Advanced Materials and Processes: Euromat 2017|
|Location||Thessaloniki, GreeceShow on map|
Fields of Expertise
- Advanced Materials Science
FWF - Nanoporös - In-situ magnetometry of nanoporous metals during dealloying and charging
Project: Research project