Preparation and Characterization of Nanoporous Copper Films by Chemical Dealloying

Abstract

Nanoporous Cu (np-Cu) materials can be easily prepared by chemical dealloying of Zn-Cu alloys. Tuning the surface area, the number of defects, the content of the less noble metal, and the mass transport properties of the nanoporous materials allows us to control its chemical, physical and catalytic properties as well as its mechanical properties for different applications. We present how the formation of the np-Cu films is controlled by the annealing temperature and kind of electrolyte. The Zn-Cu alloy films were prepared by electrodeposition of Zn onto a Cu surface. After the thermal annealing at three different temperatures, the Zn-Cu alloy films were dealloyed in acidic and alkaline media. Based on our results obtained from SEM, EDX, XPS and XRD, we correlate the structural changes (ligament size, pore size, composition) with the experimental dealloying conditions (annealing temperature, kind of electrolyte) to better understand the dealloying processes for the np-Cu films.

Ligament Evolution in Nanoporous Cu Films Prepared by Dealloying

“…In particular, during the dissolution of a less noble metal, the surface diffusion process of the remaining noble metal leads to the formation of nanosized ligaments and pores. Thus, the dealloying processes depend on the kinetics of the dissolution of the less noble metal and of the surface diffusion of the remaining noble metal as well as the mass transport processes at the interface between the electrolyte and the alloyed surface. , In addition, the pH value, kind of electrolyte, and applied potential can be adjusted to the structure of spongelike materials by controlling the surface diffusion of the remaining noble metal in the presence of adsorbing ions or oxide-based passivation layers. , This enables the tailoring of the characteristic properties like ligament size, pore size, and chemical composition of the np materials over a broad length scale. − …”

“…In the past, various Cu-based alloys like Al–Cu, Mn–Cu, or Zn–Cu have already been investigated in forming np-Cu structures during the dealloying process. ,,, Different methods are applied to produce these master alloys, for example, melt spinning or quenching of a molten metal solution. , A more facile technique under very mild conditions has recently been developed by Jia et al They prepared Zn-rich Zn–Cu alloy films by Zn electrodeposition onto a Cu surface and subsequent thermal annealing at around 150 °C in an inert atmosphere for the alloying process. The advantages of this synthetic approach are that the alloy formation is achieved without applying high temperatures, and the Zn–Cu alloy film can be obtained on different shapes of the Cu-based substrate like foil, plate, disk, and so forth.…”