Browsing by Author "Sancy Velásquez, Mamie Odette"

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    Corrosion Analysis of a High Entropy Alloy for Ammonia Production
    (2024) Sancy Velásquez, Mamie Odette; Silva Barbieri, Daniela Carolina; Walczak, Magdalena Marta
    Global energy demand has increased significantly due to world population growth and the industrialization of developing economies. Energy production has been based mainly on fossil-fuel energy, which has increased global warming due to the rise of greenhouse gases in the atmosphere, such as carbon dioxide. According to the Energy Institute, renewable power generation through wind, solar, and other renewable sources, represent only 40,86% of energy sources in 2022 [1]. An alternative energy source for fossil fuels is hydrogen, which can be produced through renewable resources that increase energy efficiency. However, the storage and transportation of hydrogen present a series of technical challenges, resulting in high costs and motivating the development of intermediate technologies. Recently, ammonia generated by renewable energy sources has gained significant attention as an energy carrier, a medium to store and transport chemical energy, and directly as fuel [2]. Ammonia is also a primary raw material for making inorganic fertilizers, pharmaceuticals, synthetic fibers, resins, and other applications, benefiting nearly half the world's population. Ammonia can be transported more efficiently and safely than hydrogen in tanker vessels or pipelines due to its relative ease of being liquefied at room temperature and moderate pressure, increasing energy density. Currently, ammonia is produced mainly from hydrogen and nitrogen by the Haber-Bosch process, which utilizes fossil fuel, thus resulting in carbon dioxide emissions. Ammonia production can also involve the non-spontaneous nitrogen reduction reaction by electrochemical techniques, which uses hydrogen that can be provided from the water, reducing energy consumption and carbon dioxide emissions. However, the non-spontaneous nitrogen reduction reaction has low activity, and its voltage is close to that of the hydrogen evolution reaction. Plasma and electrothermal chemical cycle methods have been explored to improve the selectivity of non-spontaneous nitrogen reduction reactions. Several studies have proposed new catalysts to increase the active sites, modify the size and morphology of particles, and introduce defects, such as transition metal-based catalysts, carbon-based catalysts, phosphorus-based catalysts, etc. Nevertheless, traditional catalysts frequently degrade rapidly due to the harsh chemical environment and the inherent corrosiveness of the reactions involved. A highly active catalyst that degrades quickly due to corrosion offers limited practical value. Researchers are exploring novel materials like high-entropy alloys (HEAs) to address this challenge, which also have high corrosion resistance [3]. This study focuses on the potential of a HEA, FeCrMnNiCo, as a catalyst for the electrochemical conversion of nitrogen to ammonia via the electrochemical method, evaluating the influence of the microstructure on its mechanical properties, catalytic activity, and corrosion resistance. A ball burnishing deformation was applied to the HEA at different conditions. The X-ray diffraction revealed that the FeCrMnNiCo alloy presented a face-centered cubic crystalline structure, and scanning electron microscopy analysis showed that the alloying elements were segregated in the deformed samples. The mechanical deformation determined both catalytic activity and corrosion resistance of the HEA.
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    Improved ammonia production using Cu2O@poly-carbazole electrocatalysts in the electrochemical reduction of molecular nitrogen and nitrogen oxoanions
    (2024) Herrán Maldonado, Luis Alberto; Véliz-Silva, Diego F.; Poblete Baeza, Colin; Leiva Farias, Elías Guillermo; Honores Sotelo, Jessica Scarlet; Landaeta Campos, Esteban Alonso; Sancy Velásquez, Mamie Odette; Del Río Quero, Rodrigo Rafael; Sáez Navarrete, César Antonio; Dalchiele, Enrique; Isaacs Casanova, Mauricio Alejandro
    In the present study, a Cu2O@PCz electrode for the nitrogen reduction reaction is proposed; this electrode takes advantage of the catalytic properties of Cu2O in conjunction with conducting polymers such as polycarbazole (PCz). This combination demonstrates an improvement in the catalytic activity and higher stability of this metal oxide in nitrogen electro-reduction reaction (NRR) and nitrogen oxoanion electro-reduction reaction (NORR) processes under aqueous conditions. On this basis, the material synthesized on FTO (SnO2 : F), Cu2O@PCz, exhibits a faradaic efficiency of around 38.83%, together with an NH3 productivity of 1.83 μg h−1 cm−2 in NRR type processes, on applying a potential of −0.8 V (V vs. Ag/AgCl). Similarly, in NORR type processes, the material exhibits NH3 and N2H4 productivity. The latter is the most relevant in terms of the yields obtained. Specifically, using nitrite (NO2−), an efficiency of around 77.72% was obtained, together with a formation rate of 37.02 μg h−1 cm−2 at a potential of −0.8 V (V vs. Ag/AgCl). Although N2H4 is a by-product of ammonia formation, this molecule can be considered an intermediate, which broadens the scope of this study for future research into the production of green chemicals. Finally, this research presents promising new routes for the production of NH3 at room temperature, highlighting the potential of low-cost materials, easy synthesis, and enhanced stability.