Browsing by Author "Ruiz-Leon, Domingo"

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    Carbon dioxide electrochemical reduction by copper nanoparticles/ionic liquid-based catalytic inks
    (2024) Gazzano, Valeria; Mardones-Herrera, Elias; Saez-Pizarro, Natalia; Armijo, Francisco; Martinez-Rojas, Francisco; Ruiz-Leon, Domingo; Honores, Jessica; Isaacs, Mauricio
    The development of copper nanoparticle (CuNP)-based catalysts for the electrochemical reduction of carbon dioxide (ECO2-R) offers a promising approach to enhance its transformation into other industrially significant compounds. This study reports ECO2-R at -1.3 V vs RHE using CuNPs and catalytic inks composed of CuNPs and ionic liquids (ILs), observing significant differences in the selectivity of each catalyst. Specifically, CuNPs alone show a preference for producing ethylene and aqueous products, such as formic acid, ethanol, and formaldehyde. In contrast, the addition of ILs to the catalytic system redirects selectivity toward gaseous products, with methane being the main product. These findings highlight the potential to optimize catalyst composition to tailor the selectivity of CO2 conversion processes. ILs modify the catalytic environment and influence reaction pathways, enabling the selection of specific products.
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    Evidence for the Formation of a Copolymer by Simultaneous Electropolymerization of p-Tetraaminophenyl Porphyrin Cobalt (II)) and o-Phenylenediamine on Glassy Carbon
    (2012) Arce, Roxana; Río Quero, Rodrigo del; Ruiz-Leon, Domingo; Vélez Cifuentes, Jorge; Isaacs Casanova, Mauricio; Valle de la Cortina, María Angélica del; Aguirre, Maria J.
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    Growth direction and exposed facets of Cu/Cu2O nanostructures affect product selectivity in CO2 electroreduction
    (2022) Castro-Castillo, Carmen; Nanda, Kamala Kanta; Mardones-Herrera, Elias; Gazzano, Valeria; Ruiz-Leon, Domingo; Jesus Aguirre, Maria; Garcia, Gonzalo; Armijo, Francisco; Isaacs, Mauricio
    The electrochemical reduction of CO2 to fuels and value-added chemicals on metallic copper is an attractive strategy for valorizing CO2 emissions. However, favoring the CO2 reduction over hydrogen evolution and exclusive control of selectivity towards C1 or C2+ products by restructuring the copper surface is a major chal-lenge. Herein, we exploit the differential orientation of the exposed facets in copper nanostructures that can tune the product selectivity in CO2 electroreduction. The Cu nanostructure with predominant {111} orientation produce C1 products only upon CO2 electroreduction at an applied potential of-1.3 V vs. reversible hydrogen electrodes (RHE), with 66.57% Faradaic efficiency (FE) for methane. Whereas the vertically grown copper nanostructures that are oriented in {110} direction have higher dislocation density and show greater CO2 electroreduction activity (>95%) at the same applied potential, with FE towards ethylene 24.39% and that of oxygenates 41.31%. FIA-DEMS analysis provided experimental evidence of selectivity of methane over methanol at higher overpotentials indicating the mechanism of methane formation occurs via *COH intermediate. The ethylene formation at a potential-1.0 V vs. RHE or more negative to it suggests a common intermediate for methane and ethylene on the vertically grown copper nanostructures. This work advances the understanding between the product selectivity and the surface structure of the copper nanostructures in electrochemical CO2 reduction.
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    Reduced Graphene Oxide Overlayer on Copper Nanocube Electrodes Steers the Selectivity Towards Ethanol in Electrochemical Reduction of Carbon Dioxide
    (2022) Mardones-Herrera, Elias; Castro-Castillo, Carmen; Nanda, Kamala Kanta; Veloso, Nicolas; Leyton, Felipe; Martinez, Francisco; Saez-Pizarro, Natalia; Ruiz-Leon, Domingo; Jesus Aguirre, Maria; Armijo, Francisco; Isaacs, Mauricio
    Developing copper-based electrocatalysts that favor high-value multi-carbon oxygenates is desired, given their use as platform chemicals and as a direct fuel for transportation. Combining a CO-selective catalyst with copper shifts the selectivity of CO2 electroreduction toward C-2 products. Herein, we developed a reduced graphene oxide (rGO)-modified copper nanocube electrocatalyst that could shift the selectivity of CO2 electroreduction towards ethanol (Faradaic efficiency 76. 84 % at -0.9 V vs. reversible hydrogen electrode (RHE)). Spectroelectrochemical Raman analysis reveals a higher population of *C2HxOy intermediates at -0.9 V vs. RHE on the rGO-modified copper nanocube electrocatalyst surface, which coincides with the highest faradaic efficiency of ethanol upon CO2 electroreduction at the same potential. Our results demonstrate that the rGO modification can enhance ethanol selectivity through a probable tandem electrocatalysis mechanism and provide insights into controlling electrocatalytic activity and product selectivity in the CO2 electroreduction reaction.
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    Suitability study of Ag nanosheet SERS substrates as a screening method for imidacloprid after QuEChERS extraction
    (2024) Leyton-Soto, Felipe; Schultz, Zachary D.; Ormazabal-Toledo, Rodrigo; Ruiz-Leon, Domingo; Giordano, Ady; Isaacs, Mauricio
    With the current food demand, pesticides have become some of the most important compounds to maintain food quality; however, this requires the development of methodologies that allow fast, sensitive, and low-cost screening for these contaminants. Surface-enhanced Raman spectroscopy is an emerging solution since the interaction between the analyte and metallic nanostructures increases the Raman signals, enabling trace detection and a chemical-specific measurement. In this way, the fast detection of contaminants is possible, and further advances may enable portable assays. In this work, SERS substrates with silver nanosheets (AgNSs) on a copper surface were synthesized, producing a strong SERS effect and a reproducible signal intensity from methylene blue probe molecules at an optimal reaction time of 1 min. A quantitative analysis of the pesticide imidacloprid was then performed by applying a PLSR chemometric model, revealing a high linear correlation between the reference values and the predicted values of the pesticide (Rcv2 = 0.9732 and RMSECV = 0.1239). AgNS substrates were used to determine the feasibility of using this methodology for screening imidacloprid in real bee honey samples obtained through QuEChERS extraction, and an average recovery of 75.5% +/- 0.08 was obtained. In addition, density functional theory simulations were carried out to elucidate the possible molecular interaction with the SERS surface and to assign the observed vibrational modes of imidacloprid. SERS is thus demonstrated to be an alternative to conventional pesticide detection techniques.
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    Zinc Stannate as anode and Pyrrolidinium-Based Room Temperature Ionic Liquid as electrolyte for Lithium-ion Cells
    (2021) Quezada, Diego; Honores, Jessica; Ruiz-Leon, Domingo
    With the aim to design safer batteries, pyrrolidinium-based room temperature ionic liquids (RTIL) have been used as electrolytes in Li-ion batteries using zinc stannate as the anodic material. The lithium diffusion coefficients were calculated using Electrochemical Impedance Spectroscopy (EIS) data and were 2.37 x 10(-12) cm(2)s(-1) for MPPyrTFSI and 1.29 x 10(-12) cm(2)s(-1) for BMPyrTFSI. The performance of the device strongly depended on the cation chemical structure, yielding different specific capacity values of 306.3 mAhg(-1) for BMPyrTFSI and 269.2 mAhg(-1) for MPPyrTFSI.