Electrochemically Tunable Resistance of Nanoporous Platinum Produced by Dealloying

Abstract

The extremely high surface-to-volume ratio of nanoporous platinum (np-Pt) produced by dealloying was applied for tuning electrical resistance by surface charging. In the as-dealloyed state, a characteristic sign-inversion of the charging-induced resistance variation occurs, which can be associated with the electronic structure of PtO. After electrochemical reduction, the relative resistance variations of np-Pt of up to 58% could be generated by electrochemically induced adsorption and desorption, which was 1 order of magnitude larger compared with that of cluster-assembled nanocrystalline Pt. Although the maximum resistance variation was also higher than that of dealloyed nanoporous gold (np-Au), the resistance variation related to the imposed charge was reduced owing to the higher bulk resistance of Pt compared with that of Au. The sign-inversion behavior of the resistance could be recovered by re-oxidation.

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.…”

Dealloying progress during nanoporous structure evolution analyzed by in situ resistometry

“…† 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.…”

“…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.…”

“…However, the sample oxidation during dealloying also makes an important contribution: for dealloyed, nanoporous platinum an electrical resistance decrease by about a factor of 10 was found to be associated with the reduction of the primary oxide. 18 Therefore the high resistance of the dealloyed structure has to be considered as originating from a combination of porosity and oxide.…”