In the present work, the hydrotalcite-like materials known as layered double hydroxides (LDHs) were synthesized. The Ni–Al and Ni–Fe materials with different Ni/Fe ratio were obtained by coprecipitation method at variable pH. The LDH structure was verified by X-ray diffraction, Fourier transform infrared, and Raman spectroscopy. No secondary extra phases were observed for any material. The electronic properties were evaluated by UV–vis spectroscopy, while the magnetic ones were followed by electron paramagnetic resonance (EPR). The results suggested that sample H/Ni–Fe2 (Ni/Fe = 2) has a ferrimagnetic behavior as a result of the combined action of NiII–OH–NiII, FeIII–OH–NiII, and FeIII–OH–FeIII pairs across the layers and ferromagnetic interactions operating between layers. Furthermore, the material H/Ni–Fe1 (Ni/Fe = 1.5) showed a combination of paramagnetic and ferromagnetic interactions which favors a superexchange interaction among metal centers through the OH bridges across the cationic sheets; the superexchange interaction enhances the electrocatalytic activity on the oxygen evolution reaction (OER) in alkaline media. On the other hand, XPS experiments showed that the H/Ni–Fe1 did not exhibit structural changes after electrochemical processes. The activity toward the OER was in the order H/Ni–Fe1 > H/Ni–Fe2 > H/Ni–Al, as was confirmed using in situ linear sweep voltammetry (LSV) coupled with mass spectrometry (differential electrochemical mass spectrometry).

A comparative study between carbon supported Platinum–Tin (Pt–Snsyn), synthesized via the carbonyl route, and the commercial (Pt3Sn) from E–TEK is reported. The electro‐oxidation of methanol and adsorbed CO, in sulphuric acid medium, were used as probes to evaluate the performance of these electrocatalysts. In‐line differential mass spectrometry (DEMS) was used for this purpose. Both nanoparticulate materials had a mean particle size of = 1.68 ± 0.72 nm, and = 3.58 ± 1.94 nm, respectively. It is demonstrated that, under the same experimental conditions, our homemade Pt–Snsyn is less sensitive to poisoning by CO. This observation was again verified during the oxidation of methanol. These results are discussed in terms of the local disorder of the particles surface atoms, favourably induced by size effect and the preparation route employed.

No abstract

No abstract