Nanostructured CuOx coatings onto Cu foils: Surface growth by the combination of gas-phase treatments

Abstract

In this work, the growth of copper oxide nanoarrays on the surface of copper foils by gas-based oxidation treatments was analyzed, employing either NH3–H2O2 vapors or air at high temperature. By adjusting the treatment conditions, homogeneous and firmly anchored copper oxide coatings were obtained, with densely packed surface nanostructures in the form of nanowires, nanofibers or nanorods. The homogeneity and stability of these nanostructures critically depends on the surface texture of the support, which can be easily changed by sanding or FeCl3 pretreatments. The sequential combination of both treatments allowed modifying the oxide nanoarchitectures and their surface composition. The NH3–H2O2/air sequence led to a transformation of surface nanorods with an outermost layer of Cu2O, first in CuO nanograins from which then CuO nanowires grew. A reverse combination, air/NH3–H2O2, generated a dense growth of cobweb-like nanofibers onto a base layer of CuO nanowires. The surface oxide nanostructures obtained, distributed in a large area and firmly anchored to the support, have great potential for the development of structured catalysts.