Sign-inversion of charging-induced variation of electrical resistance of nanoporous platinum

Abstract

Sign-inversion of charging-induced variation of electrical resistance of nanoporous platinum AbstractThe electrical resistance (R) of nanoporous platinum prepared by dealloying reversibly changes by 4% upon electrochemical surface charging in a regime where oxygen adsorption/desorption and surface oxidation/reduction occurs. The variation of R with charging shows a sign inversion.Besides the usual behavior of increasing R with positive charging, a decrease of R occurs at higher potentials. Following recent studies of the sign inversion of the surface stress-charge response of porous nanophase Pt, the sign-inversion of the resistance with charging may be related to the electronic structure of the surface oxide. In addition, a charge-induced variation of the chargecarrier scattering rate at the metal−electrolyte interface is taken into account.

Dealloying progress during nanoporous structure evolution analyzed by in situ resistometry

“…The smaller contribution to the total charge transfer by secondary dealloying in the case of Cu-Pt may be related to the formation of smaller ligaments, which is associated with a more thorough removal of Cu. 33 Ligament sizes determined earlier in the literature for the here used dealloying systems of np-Au 34 and np-Pt 33 confirm the trends of significantly smaller/bigger ligaments for platinum/gold as also expected from the previous results.…”

“…This indicates that, in spite of fixing the wires on the sample surface as described above, the resistometric contacts are less stable than for gold due to lower ductility and stronger oxidation. 18,33 Nevertheless the resistance trends are obvious: compared to np-Au the resistance of the np-Pt sample remains at a lower level during a larger part of the etching process and increases steeply at the end, where a total increase by about three orders of magnitude is observed for both samples.…”

“…† Table 1 summarizes details of the dealloying experiments presented here, including master alloys and dealloying potentials in reference to Ag/AgCl (Radiometer Analytical, saturated KCl). The applied parameters were chosen based on previous research, published by our group 17,18,33 as well as others. 34 The charge transfer during dealloying was calculated by continuously integrating the measured current i, corrected for leakages by subtracting a constant value determined from the transient at the end of the etching process.…”

In situ characterization of hydrogen absorption in nanoporous palladium produced by dealloying

“…The resistometric measurements were set up similar to our work on nanoporous platinum [12–13]. To sum up briefly, the rectangular sample (ca.…”

“…Nanoporous metals freshly prepared by dealloying are in a strongly oxidized condition, associated with particular physical properties [15–16 12–13]. By suitable treatment, i.e., repeated cyclic voltammetry (CV) in a wide potential range, the sample can be reduced until finally a metallic CV behavior is reached in a steady state.…”