Federico Scaglione

Nanoporous gold obtained from a metallic glass precursor used as substrate for surface-enhanced Raman scattering

Nanoporous gold (NPG) has been synthesized by electrochemical de-alloying a new precursor, amorphous Au30Cu38Ag7Pd5Si20 (at.%), starting from melt-spun ribbons. Ligaments ranging from 75 to 210 nm depending on the de-alloying time were obtained. Analytical and electrochemical evidence showed the ligaments contain residual Cu, Ag and Pd. Surface-enhanced Raman scattering from the NPG was investigated using pyridine and 4,4′-bi-pyridine as probe molecules. It was found that the activity is at maximum when the ribbon is fully de-alloyed although the ligaments then have a larger size. The enhancement is attributed to the small size of crystals in the ligaments, to their morphology and to trapped atoms.

Metastable microstructures containing zero valent iron for fast degradation of azo dyes

A novel iron powder obtained by ball milling ribbons of a rapidly solidified cast iron was tested for azo dye degradation in aqueous solution versus commercial Fe and a Fe-based metallic glass powders. The cast iron powders were at least as efficient in promoting the degradation reaction of ethyl-orange and direct blue-6 as the ball-milled metallic glass: dyes decomposition was complete in about an hour. The efficiency of alloy samples increases as a function of the decrease of particles size and does not appear to be strongly due to the structure of the phase containing Fe. The main reason for catalytic efficiency is the presence of metastable phases in the material. The zero valent iron that they contain is more prone to provide electrons for the degradation of N–N double bonds. The starting material is cheap and the sample preparation is straightforward. Therefore, it is believed these samples are suitable for fast degradation at room temperature of azo dyes compared with metallic glasses recently proposed in the literature.

Amorphous molybdenum sulphide @ nanoporous gold as catalyst for hydrogen evolution reaction in acidic environment

A novel catalyst for water splitting has been prepared by cyclic voltammetry (CV) deposition of amorphous MoS2 on nanoporous gold (NPG) obtained by electrochemical de-alloying a metallic glass precursor, Au40Cu28Ag7Pd5Si20 (at.%). As a function of number of CV cycles, Au ligaments are progressively encapsulated by a thin layer of amorphous MoS2 catalyst for hydrogen evolution. NPG provides a good substrate for deposition having excellent properties of handability and mechanical resistance in addition to catalytic activity, high conductivity and high surface area. Low onset potential, low Tafel slope and interesting values of exchange current density were obtained in linear sweep voltammetry of deposited samples. The synergistic behaviour of the multi-component material provides a highly efficient catalyst for hydrogen making of these samples a good candidate in some instances comparable to the conventional Pt catalyst for hydrogen evolution in acidic environment.