You are cordially invited to the graduate student seminars of the Chemistry Department.
This week’s speakers are Ezgi Sevgen, Suay Bilgin, and Kaan Karaca.
Please see the seminar information below and the attached abstracts.
1. “Electrochemical Impedance Spectroscopy and Current Interruption Tests for Following the Material’s Reasons for Battery State-of-Health Decay”
Speaker: Rezan Ezgi Sevgen
Advisor: Assoc. Prof. Burak Ulgut
Date : May 7th, 2023, Tuesday
Time : 12:30
Place: SBZ-14
Abstract:
Lithium-ion batteries have gained traction across various sectors, but concerns persist in the automotive industry regarding safety and charging times. Fast charging, while convenient, is known to reduce battery lifespan by decreasing its capacity, which impacts marketability. Consequently, there’s a significant focus on real-time estimation of state-of-health (SoH) of batteries in academic and industrial research. The SoH is defined as the actual discharge capacity as a ratio of the initial discharge capacity, and 80% left of it is considered to be the end of life for the battery. Therefore, it is measured only after a full discharge. Ultimately, the SoH is controlled by some combination of materials’ properties of the anode, the cathode and/or the electrolyte in addition to the surfaces. Our research focuses on uncovering mechanisms that affect the SoH using advanced operando techniques. Specifically, Electrochemical Impedance Spectroscopy (EIS) and Intermittent Current Interruption (ICI). These non-invasive, arguably the most informative methods, provide detailed insights into the underlying processes affecting battery performance. Specifically, EIS employs equivalent circuit fitting to match data with physical battery parameters, while ICI yields numerical results on transport parameters through mathematical analysis of the data. I will present the results of the aforementioned tests on ASPİLSAN INR18650A28 batteries, applying identical parameters and conditions to eight batteries throughout their lifetimes to ensure statistically significant datasets. The goal is to optimize test parameters, reduce experimental time, and identify key variables correlated with capacity loss. The results will be analyzed and ultimately, quick tests will be designed that correlates with the SoH. By doing so, we aim to shed light on the mechanisms influencing battery SoH and contribute to the development of more efficient and reliable battery technologies. 2.5000 2.5500 2.6000 2.6500 2.7000 2.7500 2.8000 2.8500 2.9000 0 50 100 150 200 250 300 350 400 450 500 Averaged Capacity (Ah) Cycle Number Battery Capacities (Ah) vs Cycle Number Series1 Series2 Series3 Series4 Series5 Series6 Series7 Series8
2. “Aerobic Oxidation of Alcohols Catalyzed by an Efficient Heterogeneous Mixed Metal Hydroxide Catalyst”
Speaker: Suay Bilgin
Advisor: Asst. Prof. Yunus Emre Turkmen
Date : May 7th, 2023, Tuesday
Time : 12:30
Place: SBZ-14
Abstract:
An environmentally friendly and efficient metal hydroxide catalyst, which was recently developed by Ozensoy and Turkmen research groups for use in aerobic C-H activation reactions for various organic compounds, has shown favourable results. As a part of our ongoing studies on developing catalytic oxidation reactions, in this project, we aim to utilize this catalyst for aerobic alcohol oxidation reactions [1, 2]. Metal hydroxides are used for this purpose because of their ability to operate at relatively low temperatures and their capability to transform into metal oxides [2]. Thanks to these properties, metal hydroxides can act as highly effective catalysts for oxidation reactions. The optimal Fe0.6Mn0.4(OH)x catalyst was found to act effectively in the oxidation of various benzhydrol, benzyl alcohol and 1- phenylethanol derivatives. It has been observed that the results of conversion from alcohol to ketone or alcohol to aldehyde vary depending on the different substituents and their positions attached to the starting alcohol. As a future plan, further mechanistic studies will be conducted to suggest possible oxidation mechanisms.
Acknowledgement: Financial support from the Scientific and Technological Research Council of Türkiye (TÜBİTAK; Grant No: 121Z524) is gratefully acknowledged.
References:
1. Sahin, Y.; Sika-Nartey, A. T.; Ercan, K. E.; Kocak, Y.; Senol, S.; Ozensoy, E.; Türkmen, Y. E. Precious Metal-Free LaMnO3 Perovskite Catalyst with an Optimized Nanostructure for Aerobic C–H Bond Activation Reactions: Alkylarene Oxidation and Naphthol Dimerization. ACS Applied Materials & Interfaces 2021, 13 (4), 5099–5110. https://doi.org/10.1021/acsami.0c20490.
2. Sika-Nartey, A. T.; Sahin, Y.; Ercan, K. E.; Kap, Z.; Kocak, Y.; Erdali, A. D.; Erdivan, B.; Türkmen, Y. E.; Ozensoy, E. Two-Dimensional Bimetallic Hydroxide Nanostructures for Catalyzing Low-Temperature Aerobic C–H Bond Activation in Alkylarene and Alcohol Partial Oxidation. ACS Applied Nano Materials 2022, 5 (12), 18855–18870. https://doi.org/10.1021/acsanm.2c04634.
3. “Elucidation of structure-functionality relationships of Cu2O nanoparticles during photocatalytic methanol partial oxidation”
Speaker: Kaan Karaca
Advisor: Prof. Emrah Ozensoy
Date : May 7th, 2023, Tuesday
Time : 12:30
Place: SBZ-14
Abstract:
Methanol is one of the centerpieces of the chemical industry both as a C1 product and an intermediate. Formaldehyde is one of the important products of methanol valorization and currently, it is mostly produced by the use of platinum group metal (PGM) catalysts and energy inefficient high-temperature thermal catalytic pathways. The use of Cu2O and “solar energy” utilizes affordable, and environmentally friendly novel photocatalysts which can significantly reduce the energy cost of formaldehyde production from methanol. Copper catalysts are widely used in the methanol industry in reactions like methanol synthesis, methanol decomposition, partial oxidation of methanol, and steam reforming of methanol, and various studies were performed on copper catalysts during these reactions. Relevant catalytic mechanistic studies were either performed on over-simplified planar copper model catalysts under ultra-high vacuum (UHV) conditions or carried out on extremely complex powder catalysts. In this work, we aim to elucidate the photocatalytic reaction mechanism of methanol to formaldehyde using shape-defined Cu2O nanocrystals that predominantly expose (100), (111), and (110) facets. In this regard, nano/micro cube, octahedra, and dodecahedra Cu2O catalysts were synthesized and characterized using SEM, ATR-IR, XRD, and XPS. Facet-dependent methanol adsorption and decomposition were investigated via in-situ FTIR. For activity measurements, a custom-design liquid-phase photocatalytic reactor was constructed and initial photocatalytic activity measurements were performed where Nash method was utilized for the quantification of formaldehyde.