7 research outputs found
Copper-Based Electrocatalysts for Electrochemical Reduction of CO2 to C2 Products
No full textThe electrochemical reduction of CO2 using copper-based electrocatalysts has emerged as a promising approach for sustainable chemical production, offering a pathway to mitigate the rising atmospheric CO2 levels while generating valuable fuels and chemicals. However, the selectivity and efficiency of copper-based catalysts towards specific C2 products remain a major challenge, hindering their commercial viability. This thesis focuses on the development, characterization, and mechanistic understanding of three promising electrocatalyst systems for multi-carbon product generation from CO2 reduction: copper-phosphide (Cu-P), copper-tin (Cu-Sn), and copper selenide (Cu2Se). A comprehensive investigation of the electrocatalysts was conducted using advanced characterization techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma optical emission spectrometry (ICP-OES). The electrochemical performance of the electrocatalysts was evaluated under various operating conditions in a zero-gap membrane electrode assembly (MEA) electrolyzer, which enables operation at industrially relevant current densities. The Cu-P0.065 electrocatalyst demonstrated a remarkable enhancement in ethylene selectivity, achieving a Faradaic efficiency (FE) of 52% at a current density of 150 mA cm-2 in 0.1 M KHCO3 electrolyte. The Cu-Sn0.03 electrocatalyst exhibited a notable shift in selectivity towards ethanol, with an FE of 48% at 350 mA cm-2 in 1 M KOH electrolyte. The Cu2Se electrocatalyst showcased a unique selectivity towards acetate production, achieving an FE of 32% at 350 mA cm-2 in 0.1 M KHCO3 electrolyte, surpassing the performance of the pure Cu electrode and previously reported Cu-Se electrocatalysts. Durability studies revealed the stability of the electrocatalysts under prolonged CO2 reduction conditions, with the Cu2Se electrocatalyst demonstrating exceptional structural integrity. Thermodynamic considerations based on Pourbaix diagrams highlighted the role of electronegative dopants in stabilizing the desired oxidation states of the electrocatalysts, contributing to their enhanced performance and stability. This thesis advances the understanding of CO2 reduction mechanisms for multi-carbon products on Cu-based electrocatalysts and provides valuable insights into the rational design of efficient and selective electrocatalysts. The development of the Cu-P0.065, Cu-Sn0.03, and Cu2Se electrocatalysts, with their remarkable selectivity, stability, and activity, represents a significant step forward in the field of electrochemical CO2 reduction
Development of a molecular procedure for the identification of Varroa destructor in southwestern Nigeria
No full textAbstract Varroa mites are a major cause among other factors such as disease, climate change, and other identified pests of the global decline in honeybees’ colonies. The four species of Varroa mites (which have varying destructive capability) are morphologically similar and the current technique of using the body ratio may lead to misidentification. The present study was designed to investigate the species of Varroa mites in Nigeria and the molecular procedure for identifying the mites. The body ratio of the varroa mites ranged between 1.46 ± 0.00 and 1.53 ± 0.03 across the four states studied in southwestern Nigeria, suggestive of Varroa destructor (≥1.4). Molecular identification using universal primers LCO 1490 and HCO 2198 failed to amplify the COX1 gene of the samples. However, a species-specific primer designed by the local team amplified the targeted gene at 230 bp. The results highlighted that V. destructor is the major pest mite in southwestern Nigeria and it can be easily identified using the species-specific primers presented in this study
Activity and Selectivity in the Electrochemical Reduction of CO2 at CuSnx Electrocatalysts Using a Zero-Gap Membrane Electrode Assembly
No full textThis article was originally published in Journal of The Electrochemical Society. The version of record is available at: https://doi.org/10.1149/1945-7111/ad6fd7.
© 2024 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. [DOI: 10.1149/1945-7111/ad6fd7]In this study Cu, Sn, and bimetallic CuSnx nanoparticles were synthesized and evaluated as electrocatalysts for CO2 reduction using zero gap membrane electrode assemblies. Results show bimetallic electrocatalysts with Sn contents above 10% yield formate as a primary product with Faradaic Efficiencies near 70% at 350 mA cm−2. Cu-Snx electrocatalysts with less than 10% Sn yield CO at current densities below 350 mA cm−2 and relatively lower cell potentials. When the low-Sn content bimetallic electrocatalysts were evaluated in alkaline anolytes at 350 mA cm−2, ethanol was recorded as the primary product (FE = 48.5% at Ecell ≥ 3.0 V). We propose enhanced C2 activity and selectivity originate from Cu dimers adjacent to Sn atoms for bimetallic electrocatalyst with low-Sn content. The C2 active sites are lost when the surface Sn content exceeds 25%–38%.This work was supported by the U.S. National Science Foundation under Award Number 2119435. A.L.O. acknowledges funding by the National Science Foundation under Award Number 1954611. Portions of this research were conducted with high performance computing resources provided by Louisiana State University (http://www.hpc.lsu.edu)
Activity and Selectivity in the Electrochemical Reduction of CO2 at CuSnx Electrocatalysts Using a Zero-Gap Membrane Electrode Assembly
No full textIn this study Cu, Sn, and bimetallic CuSnx nanoparticles were synthesized and evaluated as electrocatalysts for CO2 reduction using zero gap membrane electrode assemblies. Results show bimetallic electrocatalysts with Sn contents above 10% yield formate as a primary product with Faradaic Efficiencies near 70% at 350 mA cm−2. Cu-Snx electrocatalysts with less than 10% Sn yield CO at current densities below 350 mA cm−2 and relatively lower cell potentials. When the low-Sn content bimetallic electrocatalysts were evaluated in alkaline anolytes at 350 mA cm−2, ethanol was recorded as the primary product (FE = 48.5% at Ecell ≥ 3.0 V). We propose enhanced C2 activity and selectivity originate from Cu dimers adjacent to Sn atoms for bimetallic electrocatalyst with low-Sn content. The C2 active sites are lost when the surface Sn content exceeds 25%-38%
Electrochemical Reduction of CO2: A Common Acetyl Path to Ethylene, Ethanol or Acetate
No full textEthylene is well known as the primary product of CO2 reduction at Cu electrocatalysts using zero-gap membrane electrode assembly cells with gas diffusion cathodes. Other types of Cu electrocatalysts including oxide-derived Cu, CuSn and CuSe yield relatively more C2 oxygenates; however, the mechanisms for C2 product selectivity are not well established. This work considers selectivity trends of Cu-P0.065, Cu-Sn0.03, and Cu2Se electrocatalysts made using a standard one pot synthesis method. Results show that Cu-P0.065 electrocatalysts (Cuδ+ = 0.13) retain ethylene as a primary product with relatively higher Faradaic efficiencies (FE = 43% at 350 mA cm−2) than undoped Cu electrocatalysts (FE = 31% at 350 mA cm−2) at the same current density. The primary CO2 reduction product at Cu-Sn0.03 (Cuδ+ = 0.27) electrocatalysts shifts to ethanol (FE = 48% at 350 mA cm−2) while CO2 reduction at Cu2Se (Cuδ+ = 0.47) electrocatalysts favor acetate production (FE = 40% at 350 mA cm−2). Based on these results, we propose a common acetyl intermediate and a mechanism for selective formation of ethylene, ethanol or acetate based on the degree of partial positive charge (δ + ) of Cu reaction sites
Fundamental Insights into Copper-Epoxy Interfaces for High-Frequency Chip-to-Chip Interconnects
No full textFuture processes and materials are needed to enable multichip packages with chip-to-chip (C2C) data rates of 50 GB/s or higher. This presents a fundamental challenge because of the skin effect, which exacerbates signal transmission losses at high frequencies. Our results indicate that smooth copper interconnects with relatively thin cuprous oxides (Cu2O, CuI) and amine-functional silane adhesion promoters improve interfacial adhesion with epoxy dielectrics by nearly an order of magnitude. For the first time, we present X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy evidence of Cu(I)-O-Si bond formation at silane-treated interfaces. Thus, relatively smooth interconnects can benefit from reduced skin losses while maintaining their mechanical integrity and reliability. Failure mechanisms of Cu interconnects with cuprous and cupric oxide (CuO, CuII) are explored using scanning electron microscopy (SEM) and Auger electron spectroscopy (AES). These results indicate that both cupric oxides and relatively thick cuprous oxide interfaces lead to relatively weaker interfaces compared with thin cuprous oxides with adhesion promoters
Knowledge and attitude of populations on blackflies and onchocerciasis and participation in mass drug administration in first-line communities near Erin-Ijesha and Arinta waterfalls, Southwest Nigeria.
No full textBackgroundPreliminary assessments have identified blackfly biting activity at Erin-Ijesha and Arinta waterfalls in Southwest Nigeria, predisposing first-line communities to a high risk of onchocerciasis. There is a need to assess knowledge of blackflies, onchocerciasis, and participation in treatment programs among residents of first-line communities near the waterfalls to evaluate onchocerciasis transmission risk.MethodsA cross-sectional survey was conducted among 236 residents at Erin-Ijesha and Ipole-Iloro, two first-line communities using structured questionnaires. Data were entered into Microsoft Excel and analyzed using the Statistical Package for the Social Sciences (SPSS) software version 21. Relationships between variables were analyzed using t-test and chi-square, with a 95% confidence interval.ResultsMajority (73.3%) in Erin-Ijesha and (83.7%) in Ipole-Iloro reported knowledge of blackflies, with 83.3% and 87.0% aware of onchocerciasis, respectively. The majority of participants had no knowledge of how onchocerciasis is transmitted, with only 8.7% and 10.5% in Erin-Ijesha and Ipole-Iloro, respectively, linking the disease to blackfly bites. Ivermectin uptake was relatively high at 75.7% and 76.7% in Erin-Ijesha and Ipole-Iloro, respectively. Willingness to participate in future treatment programs was lower, at 64.7% and 64.0% in Erin-Ijesha and Ipole-Iloro, respectively. Level of education significantly influenced willingness to participate in future mass distribution of ivermectin (p ConclusionThe limited understanding of blackfly bioecology and onchocerciasis among residents may lead to increased exposure to bites, thereby raising the risk of transmission. To address this, the federal and state ministries of health, along with treatment implementing partners, should enhance sensitization efforts and public health education during the annual Mass Drug Administration campaigns. Improving knowledge in these high-risk communities will encourage residents to take preventive measures against bites and improve treatment uptake, ultimately reducing the risk of disease transmission
