You are invited to CHEM 591 – Graduate Student Seminars of Chemistry Department.
This week’s speakers are Muratcan Ös, Levent Bahçeci, and Miray Tamer.
Please see the seminar information and the abstracts below.
Scavenger-Based Mechanistic Analysis of Methanol Partial Oxidation
to Formaldehyde on Facet Defined Anatase TiO2 {100} and {001} Nanocrystal Catalysts
Miray Tamer
Advisor: Prof Emrah Özensoy
Time: May 5, 12:30, SBZ14
Milling an Extra Mile: Mechanistic Study of Some Mechanochemical Reactions for Active Pharmaceutical Ingredient Synthesis
Levent Bahçeci
Advisor: Assoc. Prof Bilge Baytekin
Time: May 5, 12:30, SBZ14
Two Salt Surfactant Mesophases: Synthesis of Mesoporous MgM2O4 (M = Mn, Fe and Co) Electrodes and Their Electrochemical Properties
Muratcan Ös
Advisor: Prof Ömer Dağ
Time: May 5, 12:30, SBZ14
Scavenger-Based Mechanistic Analysis of Methanol Partial Oxidation to Formaldehyde on Facet Defined Anatase TiO2 {100} and {001} Nanocrystal Catalysts – Miray Tamer
Methanol, a key C1 feedstock, plays a central role in energy storage and chemical manufacturing, and its selective conversion to formaldehyde (FA) is of significant industrial importance. Conventional FA production relies on energy-intensive thermal processes operating at elevated temperatures. Here, we investigate the photocatalytic oxidation of methanol to formaldehyde over anatase TiO2 as a sustainable, low-temperature alternative. However, despite the extensive use of anatase TiO2 in photocatalysis, the dominant reaction pathways governing methanol-to-formaldehyde conversion remain insufficiently resolved in the literature.
In this study, anatase TiO2 {100} and {001} nanocrystal catalysts were synthesized and
thoroughly characterized using various analytical techniques, including TEM, XRD, BET,
RAMAN, XPS and EPR. The photocatalytic activity toward formaldehyde production was
studied under UV-A irradiation (365 nm) for 1 h at room temperature. Formaldehyde quantification was performed using the Nash method, based on indirect detection via UV-Vis spectrometry. To elucidate the prominent reaction pathways, electron, hole, and hydroxyl radical-mediated reaction routes were selectively probed using AgNO3, Na2C2O4, and isopropanol as scavengers, respectively.
Our mechanistic studies indicate that the electron-mediated pathway dominates formaldehyde production over both TiO2 {100} and {001} facets, while facet-dependent differences emerge in the contributions of secondary pathways: the TiO2 {100} surface exhibits comparable h⁺- and •OH-mediated contributions, whereas the {001} facet shows a markedly enhanced h⁺-mediated contribution, highlighting the structure sensitivity of the reaction. This facet-dependent behavior is attributed to the higher surface density of undercoordinated Ti5c sites and the relatively higher surface energy of the {001} facet as compared to that of {100}, which render the former sites less stable and more catalytically active, thereby promoting hole-driven oxidation pathway. These findings highlight the significance of the surface chemical features of anatase TiO2 catalysts in governing competing methanol-to-formaldehyde reaction pathways, providing a strategy to tailor photocatalytic conversion.
Keywords: Facet defined anatase TiO2, Methanol oxidation, Photocatalysis, Scavenger,
Mechanistic Analysis, Structure sensitivity.
Milling an Extra Mile: Mechanistic Study of Some Mechanochemical Reactions for Active Pharmaceutical Ingredient Synthesis – Levent Bahçeci
Mechanochemistry is a subfield of chemistry that governs reactions driven by mechanical motions, such as compression, shear, or friction. In recent years, chemists have turned their attention to mechanochemical reactions, which offer greener options, new chemical pathways, and high selectivity. One area that remains particularly interesting is organic mechanochemistry. It offers an alternative to wet synthesis of crucial chemicals, with a growing interest as they are produced on a larger scale and require efficiency. However, fundamental research on reaction mechanisms of organic mechanochemistry remains largely uncharted. Here, we show a novel method for the synthesis of of several first-generation H-1 antihistamine representatives, and investigate the stereochemistry of the solid-state reaction pathways when the solvents effects are removed, using a cryomilling device. Our results demonstrate that when the starting reactant is an enantiomer, antihistamine production occurs through inversion of stereochemistry as seen in Sn2 mechanisms. We also investigate further into liquid assisted grinding (LAG) of such reactions with emphasis on polar/apolar solvents and their effects on stereochemistry.
Two Salt Surfactant Mesophases: Synthesis of Mesoporous MgM2O4 (M = Mn, Fe and Co) Electrodes and Their Electrochemical Properties – Muratcan Ös
Mesoporous magnesium metal oxides (MgM2O4, where M = Mn (II), Fe (III) and Co (II)) have been synthesized by using transition metal nitrate salts (Mn(H2O)42, Co(H2O)62, and [Fe (H2O)9] (NO3)3) and two surfactants (hexadecyltrimethylammonium bromide, CTAB and 10-lauryl ether, C12E10) using molten salt-assisted self-assembly method (MASA). The clear solutions of the ingredients form lyotropic liquid crystalline (LLC) phase (mesophase) upon their solvent evaporation. The solutions and mesophases are analyzed primarily using ATR-FTIR, XRD, and POM techniques. The nitrate species, monitored by ATR-FTIR, are unique to follow hydrolysis and condensation processes during solvent evaporation. The LLC phase, drop-cast coated over a glass substrate, is calcined at elevated temperatures (300-700oC) to obtain the mesoporous MgM2O4 and analyzed through high-angle XRD and ATR-FTIR, SEM, BET and XPS.
Further, to investigate the catalytic performance of the samples in water oxidation, they are coated onto fluorine-doped tin oxide (FTO) substrates and graphite rods by spin and dip coating methods, respectively, and subsequently calcined to obtain porous electrodes. These electrodes are then studied for their electrochemical properties using cyclic voltammetry (CV), multi-step chronopotentiometry and amperometry (MCP-MCA) measurements. The results indicate that cobalt-based mesoporous electrodes have higher stability compared to manganese and iron-based electrodes, and exhibit small Tafel slope values at graphite substrates, indicative of favorable reaction kinetics for water oxidation.
1Raza, H. A.; Karakaya, I.; Dag, Ö. Nanoarchitectonics of Mesoporous CaFe2O4 Thin-Film Electrodes from Salt-Surfactant Lyotropic Liquid Crystalline Mesophases and Their OER Performance. ACS Applied Energy Materials 2023, 6 (18), 9681–9697. DOI:10.1021/acsaem.3c01776.