Synthesis of nanoporous gold by free corrosion of an amorphous precursor

Highlights: • Nanoporous Au obtained after free corrosion of amorphous ribbon in HNO₃ at different [C] and temperatures. • Ligaments coarsen from small domains as a function of temperature and electrolyte concentration. • Scattering domains determined for evaluating surface diffusion coefficients. • Entropy of activation for the surface diffusion suggests interaction of adatoms with electrolyte. - Abstract: De-alloying of an amorphous precursor is attractive to get a fine microstructure after copious nucleation of crystalline hillocks. However, the noble metal atoms freed on the alloy surface gain high mobility causing coarsening of ligaments. This work describes the de-alloying by free corrosion of a Au-based amorphous alloy in HNO₃ at different temperatures and concentrations. Gold ligaments ranging from 47 to 155 nm have been obtained as a function of acid content. Scanning Electron Microscopy, Transmission Electron Microscopy and X-ray Diffraction was used to characterize the nanoporous structure of dealloyed samples. Moreover, an evaluation of the surface diffusion coefficient and of the activation energy and entropy for diffusion of Au adatoms have been performed to study the mechanism of dealloying under free corrosion conditions in comparison with previous studies