Adsorption-driven tuning of the electrical resistance of nanoporous gold

Abstract

The electrical resistance of nanoporous gold prepared by dealloying is tuned by charging the surfaces of the porous structure in an electrolyte. Reversible variations in the resistance up to approximately 4% and 43% occur due to charging in the regimes of double layer charging and specific adsorption, respectively. Charging-induced variations in the electron density or of the volume cannot account for the resistance variation, indicating that this variation is primarily caused by charge-induced modifications of the charge carrier scattering at the solid-electrolyte interface. The relative resistance variation in nanoporous Au with surface charging is found to be much higher than reported for porous nanocrystalline Pt. This is due to the lesser resistance contribution from internal grain boundaries. The resistance variation in nanoporous Au is also higher than that found in thin films owing to the stronger surface scattering in the ligament structure compared to plan surfaces. We argue that the strong resistance variation in up to 43% in the regime of specific adsorption is due to the reversible formation of a chemisorbed surface layer acting as scattering centers for the charge carriers.

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

“…This has been observed before both for porous nanophase metals (nanocystalline Pt [11], Au 75 Fe 25 [12,13], nanoporous Au [14,15]) as well as for thin films [19] including Pt [20]. For sample II (Pt-II, Fig.…”

“…A reversible resistance variation ΔR/R 0 of about 4% occurs. Since scanning is limited to the narrow range of specific adsorption, this maximum variation ΔR/R 0 is much lower than that observed for nanoporous Au recently [15]. The most striking feature is that both during positive and negative scan, the resistance first increases and subsequently decreases, giving rise to relative resistance minima at the reversal points of the CV and to resistance maxima in between.…”

“…In each of these studies the resistance was observed to increase reversibly upon positive charging, ranging from several percent up to 40 % when positive charging is extended to the regime of chemisorption [15]. The present work, reports on studies of the tunable electrical resistance of nanoporous Pt prepared by dealloying which shows a sign inversion from an increase to a decrease of the resistance with positive charging.…”

“…The resistance measurements in dependence of electrochemical charging were performed in a similar way as decribed previously for measurements on np-Au [15]. Summarizing briefly, the nanoporous Pt stripe was contacted by five Pt wires, four electrodes for resistance The resistance was monitored concurrently in intervals of 2.5 seconds during cyclovoltametric (CV) scanning.…”

“…Electrical resistance in dependence of charging has been investigated so far for both particle-assembled porous nanocystalline metals (Pt [11], Au 75 Fe 25 [12], [13]) as well as for nanoporous Au prepared by dealloying [14,15]. In each of these studies the resistance was observed to increase reversibly upon positive charging, ranging from several percent up to 40 % when positive charging is extended to the regime of chemisorption [15].…”