This work presents the synthesis of Au nanoparticles from gold coatings recovered from processor pins with minimal waste generation. The process consisted of four main steps: (1) physical recovery of pins, (2) recovery of gold coatings by acid digestion, (3) synthesis of HAuCl₄ under mild conditions and, (4) synthesis of Au nanoparticles by the Turkevich method. The small dimensions of Au coatings allowed the synthesis of HAuCl₄ with lower amounts of HCl_conc and HNO_3conc than those used with aqua regia. This method has significant advantages, such as lower NO_2(g) emission, easy post-treatment and purification, low synthesis cost and high yields. Gold nanoparticles synthesized from HAuCl₄ were characterized by transmission electron microscopy (TEM) and UV-Vis spectroscopy. Size distribution analysis showed particles 14.23 nm in length and 12.05 nm in width, while absorption spectra showed a surface plasmon located at 523 nm; these characteristics were very similar to those observed with Au nanoparticles obtained with Aldrich’s reagent. It is suggested that recycling procedures can be improved by taking into account the size and shape of the metals to be recovered, thus introducing a new field of research known as hydronanometallurgy.

In this work, the oxygen reduction reaction in the absence or presence of 2.0 mol l⁻¹methanol and the hydrogen oxidation reaction are studied on RuFe electrocatalyst synthesized by a microwave thermal heating method in water as reaction medium. The electrocatalysts were morphologically and structurally typified by scanning electron microscopy and by x-ray diffraction, respectively. Three crystalline phases were found: Ru, Fe₂O₃and Fe(OH)₃·(H₂O)_x(Bernalite). Functional tests were performed by convective (rotating disk electrode) and non-convective (linear sweep voltammetry and cyclic voltammetry) electrochemical techniques in 0.5 mol l⁻¹H₂SO₄. Both RuFe electrocatalysts show interesting electrochemical activities since they can carry out both the oxygen reduction reaction and the hydrogen oxidation reaction.

Metallic ruthenium electrocatalyst with activity for the hydrogen oxidation reaction and the oxygen reduction reaction has been synthesized by microwave irradiation at 180 ℃ in deionized water as reaction media. Characterization of the material by ATR-FTIR spectroscopy shows a complete decarbonylation of the precursor Ru3(CO)12 with formation of metallic Ru, which is confirmed by the corresponding x-ray diffraction analysis. Evaluation of the material's electrocatalytic properties by the rotating disk electrode technique in 0.5 mol L-1 allows the study of hydrogen oxidation and oxygen reduction reaction using linear sweep voltammetry, exhibiting that the diffusional processes of H2 and O2 can be improved by modifying the electrocatalytic ink preparation.

This work presents an OsRu-based electrocatalyst synthesis, by a rapid and efficient method through microwave irradiation. The outstanding electrocatalyst shows a dual catalytic activity, demonstrating both: hydrogen oxidation and oxygen reduction reactions. The material is structural and morphologically characterized by FT-IR, X-ray diffraction, EDS, and SEM, indicating nanoparticulated Os and Ru metallic phases with a crystallite size of ∼6 nm, calculated by the Scherrer equation. The metal nanoparticles are apparently deposited on a carbonaceous sponge-like morphology structure. Its electrochemical characterization is performed in 0.5 M H₂SO₄ by the rotating disk electrode technique, employing cyclic and linear sweep voltammetry. Two different ink treatments have been studied to improve the obtained polarization curves. The material is also tested in the presence of methanol for the oxygen reduction reaction, showing an important resistance to this contaminant, making it viable for its use in direct methanol fuel cells (DMFCs) as a cathode and in polymer electrolyte fuel cells (PEMFCs) as an anode as much as a cathode.

A simple and rapid synthesis of a CoFeRu-based electrocatalyst by a microwave-assisted method (using water as the microwave absorbing solvent) is reported in this work. Agglomerates with different sizes and shapes are observed by scanning electron microscopy technique. The energy dispersive X-ray spectroscopy shows a low atomic percentage of Co and similar atomic percentage of Fe and Ru. However, the X-ray diffraction exhibits only the presence of metallic Ru and Fe₂O₃ (hematite) phases. The oxygen reduction without and with 2 mol L⁻¹ methanol is studied using the rotating disk electrode technique. The electrochemical kinetic parameters obtained are compared to a similar electrocatalyst reported in the literature, which was synthesized using a mixture of an organic solvent with DI water as the microwave absorbing solvent. An improvement on the activity of the electrocatalyst synthesized is observed, where high Tafel slopes are not observed. The electrocatalyst also showed tolerance to the presence of methanol during the oxygen reduction reaction.