Browsing by Author " Ramírez, A.M.R."

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    In situ electrochemical synthesis of rhenium oxide-reduced graphene oxide hybrid electrodes for enhanced water splitting
    (2025) Vergara-Pacheco. A. ; Fernandez Adell, Jose Ignacio; Preuss, P. ; Stephant, N.; Cattin, L.; Louarn, G.; Bernede, J.-C. ; Fischer, A.; Camarada, M.B. ; Ramírez, A.M.R.
    This study reports the in situ electrochemical synthesis of rhenium oxide nanoparticles on a glassy carbon (GC) electrode pre-modified with graphene oxide (GO), which is simultaneously reduced to reduced graphene oxide (rGO) during deposition. The resulting GC|rGO|ReOxNP electrodes were characterized by XPS, SEM, TEM, and EDS. Optimal HER performance was obtained with a 60 s deposition, achieving an overpotential of − 0.160 V at 10 mA cm− 2 and a Tafel slope of 52 mV⋅dec− 1. The post-HER analysis showed that the optimum electrocatalytic properties were associated with the predominant rhenium oxidation states ReVI and ReVII. A key strength of this approach lies in its simplicity and sustainability: the electrochemical method provides a direct, single-step route for simultaneously depositing rhenium oxide nanoparticles and reducing GO to rGO under mild conditions. This eliminates the need for high-temperature treatments or multistep chemical procedures commonly reported in similar studies. These results highlight the potent
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    Rhenium and Rhenium–Copper Nanoparticles: Evaluation of the Catalytic Activity for the Decomposition of Ammonium Perchlorate
    (2023) Preuss, P.; Méndez, G.Y.; Hormazábal-Campos, C.; Ramírez, A.M.R.; Angel Figueroa, Felipe Alfonso; Camarada, M.B.
    © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.Composites of rhenium (ReNP) and rhenium–copper nanoparticles (ReCuNP) were studied as catalysts for the decomposition of the oxidizer ammonium perchlorate (AP) for composite solid propellants. Both composites were prepared by reducing ammonium perrhenate (NH4ReO4) and copper chloride (CuCl2) in the presence of polyamidoamine (PAMAM) dendrimers. The PAMAM-based nanostructures were characterized by transmission electron microscopy (TEM), high resolution TEM, and X-ray photoelectron spectroscopy. ReNP@PAMAM samples showed rhenium clusters and partially oxidized spherical nanoparticles of approx. 1 nm in diameter, while ReCuNP@PAMAM comprised nanoparticles of 6 nm in average size with different shapes and high-size dispersion. The computational description demonstrated the higher stability of the interaction between copper and PAMAM than perrhenate anion due to the charge transfer from the dendrimer to the cation. The materials were evaluated for the catalytic decomposition of AP by calorimetry. The catalytic performance of ReCuNP@PAMAM was superior to that of ReNP@PAMAM, lowering the decomposition of AP at high temperatures. However, the latter composite increased the energy release drastically due to the exothermic oxidation of rhenium metal. Graphical Abstract: [Figure not available: see fulltext.].