You are invited to CHEM 591 – Graduate Student Seminars of Chemistry Department.
This week’s speakers are Berfin Güleryüz, Sude Selda Yağcı, Joud Al Hourani and Miray Tamer.
Please see the seminar information and the abstracts below.
Structure Sensitivity in DeNOx Catalysis on Shape-Defined Cu2O Nanocrystal Model Catalysts
Berfin Güleryüz
Advisor: Prof. Emrah Özensoy
Time: May 12, 12:30, SBZ14
Salty Hydrogel Muscles with Ion Tunable Stiffness
Sude Selda Yagcı
Advisor: Assoc. Prof Bilge Baytekin
Time: May 12, 12:30, SBZ14
Electrocatalytic Nitrate Reduction to Ammonia Using Galvanically Deposited Cu@Ni Foam
Joud Al Hourani
Advisor: Prof. Emrah Özensoy
Time: May 12, 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
Advisor: Prof. Emrah Özensoy
Time: May 12, 12:30, SBZ14
Structure Sensitivity in DeNOx Catalysis on Shape-Defined Cu2O Nanocrystal Model Catalysts – Berfin Güleryüz
Nitrogen oxides (NOₓ) are major atmospheric pollutants, and their efficient removal remains a significant catalytic challenge. Cu-based materials are widely employed in DeNOₓ technologies, while the structural complexity of CuOₓ-based catalysts can be effectively examined using shape-defined Cu₂O nanocrystal model systems. In this context, the present study investigates the mechanism of NOₓ adsorption and decomposition on well-defined Cu₂O nanocrystals.
Highly uniform cubic and octahedral Cu₂O nanocrystals exposing predominantly {100} and {111} facets, respectively, were synthesized and employed to elucidate the facet dependence of NOₓ adsorption and desorption at elevated temperatures. The catalysts were systematically characterized by SEM, TEM, XRD, and XPS, while probe-molecule adsorption experiments (NO+O2) were monitored by in situ Fourier transform infrared (FTIR) spectroscopy, enabling real-time identification of surface species. In addition, temperature-programmed desorption (TPD) experiments were performed to evaluate the thermal stability of adsorbed species and to quantify the relative NOₓ storage capacities of cubic and octahedral Cu₂O nanocrystals.
On the cubic catalysts, bridging and bidentate nitrate/nitrite species were predominantly observed, whereas monodentate nitrate/nitrite species were dominant on the octahedral catalysts. This distinction is attributed to the different surface geometries of the two morphologies: cubic Cu₂O mainly exposes terrace sites with high-coordination surface atoms, whereas octahedral Cu₂O contains a higher density of kinks and edges, that is, coordinatively unsaturated sites, which make polydentate nitrate/nitrite adsorption less favorable. Temperature-dependent in situ FTIR and TPD results further demonstrated that NOₓ-derived surface intermediates exhibit greater thermal stability on the {111} facets than on the {100} facets. Complementary in situ FTIR and TPD experiments conducted over the 50–700 °C temperature range also revealed that NOₓ thermal decomposition and reduction pathways are strongly structure-sensitive. Overall, this study establishes a clear structure-functionality relationship in Cu-based DeNOₓ catalysts by directly correlating surface geometry with NOₓ adsorption behavior, intermediate speciation, thermal stability, and reactivity.
Keywords: Cu₂O nanocrystals; facet-dependent reactivity; in situ FTIR spectroscopy; temperature-programmed desorption; model catalysts; deNOₓ catalysis.
Salty Hydrogel Muscles with Ion Tunable Stiffness – Sude Selda Yağcı
Hydrogels are three-dimensional hydrophilic polymer networks that can store water in their structure without disrupting their structures1. Hofmeister series is a systematic arrangement of ions based on their ability to precipitate proteins2. Salts can thoroughly affect the mechanical properties of hydrogels by the diffusion of their ions into the gel by disrupting their hydration network causing it to either shrink and get stiff or swell and get soft which in turn modulates their viscoelasticity, yield stress, and damping properties. While there are researches focusing on common kosmotropic salts of ions such as citrate and sulfate, it is rare to find research on other salts that have the opposite effect or those that focus on gathering information to create a trend by means of mechanical properties. Here we will show a collective data set regarding salts of various ions and their effects. The salts selected for this study, Na3Cit, Na2SO4, NaCl, NaI, and NaSCN, span the full spectrum of the Hofmeister series ranging from kosmotropes (salt-out), which promote protein stability and aggregation, to chaotropes (salt-in) which increase protein denaturation and solubility. For quantifications of these effects, rheological measurements focusing on strain and frequency sweep are being made to characterize the altered gels. Furthermore, the study will explore the reversibility of these alterations. By adding counter-acting salts to already altered gels, the research aims to determine if salt precipitation can restore the original mechanical properties of the material. This work can pave the way for significant implications for the development of tunable biomaterials in soft robotics and tissue engineering.
1 Turan, N. B.; Engin, G. O.; Bilgili, M. S. In Environmental nanotechnology: Implications and applications; Elsevier, 2022; Vol. 99, pp 105–134 2 Moghaddam, S. Z.; Thormann, E. The Hofmeister Series: Specific Ion Effects in Aqueous Polymer Solutions. J. Colloid Interface Sci. 2019, 555, 615–635.
Electrocatalytic Nitrate Reduction to Ammonia Using Galvanically Deposited Cu@Ni Foam – Joud Al Hourani
Ammonia is a crucial chemical used for fertilizers and energy storage, and it is mainly produced by the Haber-Bosch Process, which consumes large amounts of energy and emits significant CO2. Electrocatalytic Nitrate reduction (NO3RR) offers a practical route to produce Ammonia while treating wastewater from pollutants. Copper-based catalysts are widely studied for electrochemical nitrate reduction due to their moderate binding strength toward nitrate and key intermediates (NO₃⁻, NO₂⁻, NOₓ*). Their activity and selectivity depend strongly on surface structure and oxidation state, making controlled synthesis and interface design critical. In this work, copper is deposited onto nickel foam (NF) via galvanic replacement to form a conductive, high-surface-area electrode with a defined Cu–Ni interface. The material is characterized to confirm copper loading and surface composition and then evaluated for nitrate reduction under controlled conditions, including variation of electrolyte environment. Ammonia yield is quantified using the indophenol blue method, and the results reflect how the Cu/Ni interfacial structure influences nitrate reduction performance.
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.