Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session D32: Catalytic Materials and Processes |
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Sponsoring Units: DCMP Chair: Sylvie Rangan, Rutgers University Room: Room 224 |
Monday, March 6, 2023 3:00PM - 3:12PM |
D32.00001: Revealing Charge Dynamics of Cu2O Thin Film via Transient Absorption Spectroscopy and Numerical Modeling in Picosecond to Microsecond Time Scale Mona Asadinamin Understanding the mechanism of charge dynamics of photocatalytic materials is the key to design and optimize more efficient materials for diverse renewable energy applications such as solar water splitting, solar CO2 conversion, environmental remedy, etc. In this study, the charge dynamics of Cu2O thin film, a low band gap photocatalyst, is unraveled by the combination of ultra-fast (picosecond) and nanosecond transient absorption spectroscopy (TAS) techniques. |
Monday, March 6, 2023 3:12PM - 3:24PM |
D32.00002: Turnover frequencies and rates of CO oxidation on Pt single atomic sites on CeO2 surfaces: an ab initio based KMC study Sampyo Hong, Dave Austin, Wei Tan, Shaohua Xie, Duy Le, Fudong Liu, Talat S Rahman Our recent study on singly dispersed Pt single atoms on CeO2 surfaces have shown that the Pt atoms bind at the Ce vacancy at the edge sites on CeO2 support after calcination at 550oC whereas they bind at the Ce vacancy sites on the terrace of CeO2 after calcination at 800oC. This difference in the local Pt geometry has substantial impact on CO oxidation such that the former exhibits higher CO turnover frequency (TOF) and reaches 100% CO conversion at lower temperature than the latter. To understand the rationale for this behavior, we have calculated the CO oxidation reaction pathways on both catalysts using density functional theory and then performing Kinetic Monte Carlo (KMC) simulations. Our KMC results show that the catalyst calcinated at 550oC has a higher CO2 TOF and conversion rate than the one calcinated at 800oC, in good agreement with experiments. We track the difference in the performance of the catalysts to the activation energies for O2 dissociation and CO-O combination. |
Monday, March 6, 2023 3:24PM - 3:36PM |
D32.00003: 2-propanol oxidation at the Co3O4 (001)/H2O Interface: the role of Temperature, Surface Composition and Electrochemical Environment Stephane Kenmoe, Amir Hossein Omranpoor, Eckhard Spohr Ab initio molecular dynamics simulations of a single hydrated 2-propanol molecule were performed to study the role of temperature, surface structure and electrochemical environment for the oxidation of 2-propanol to acetone at the Co3O4 (001)/H2O interface on the A-terminated and B-terminated surfaces. In both cases, no C-H bond cleavage is observed at room temperature. However, under oxidative conditions, which are modeled here by partial dehydrogenation of the mixed hydroxyl/water adsorbate layer, dehydrogenation of the alcoholic OH group is observed on both surface terminations. As a result, adsorbed 2-propanolate is formed. The reaction on the less hydroxylated B- terminated surface further proceeds with C-H bond cleavage at the 2-carbon atom. The oxidation product acetone remains adsorbed on the Co3+ site during the simulation period of approximately 20 ps. Both deprotonation steps are aided by the presence of the adsorbed hydroxyl groups in the vicinity of the adsorbed alcohol molecule, because both hydrogen atoms from the reac- tand molecule are transferred as protons to form adsorbed water molecules. Different from the case of the partially dehydrogenated environment, raising the system temperature from 300 to 450 K, which can be considered a simple model for high temperature thermal catalysis, does not lead to oxidation via C-H dehydrogenation of the 2-propanol molecule. |
Monday, March 6, 2023 3:36PM - 3:48PM |
D32.00004: First-principles study of electronic structure and magnetism in CoPt for catalysis Kevin J Allen, Christopher A Lane, Emilia Morosan, Jian-Xin Zhu The intermetallic compounds MPt (M = Co or Fe) have been of particular interest due to their potential applications as efficient catalysts for proton exchange membrane fuel cells. Interestingly, the presence of local magnetic moments appears to enhance catalytic activity. However, the underlying mechanism for this effect remains elusive. In this talk, we will focus on investigating the interaction between O2 and CoPt, due to magneto-crystalline anisotropy and robust catalytic performance in the latter. In particular, by performing first-principles electronic structure calculations, we will examine the change in O2 molecular binding energy and Co magnetic moment response for various crystal surface orientations. Additionally, the dependence on surface adsorption site and molecule orientation relative to the magnetic polarization will also be discussed to provide insight into the underlying mechanism of magnetic enhanced catalysis. This study will provide deeper understanding of chemical reaction pathways and magneto-regulation activities in CoPt. |
Monday, March 6, 2023 3:48PM - 4:00PM |
D32.00005: Effect of Local Coordination Environments of Ceria Supported Pt Single Atom Catalyst on Oxidation Reactions Talat S Rahman, Dave Austin, Wei Tan, Shaohua Xie, Duy Le, Sampyo Hong, Fudong Liu Ceria supported Pt single atom catalysts (SAC) (Pt1/CeO2) have been proposed as effective catalysts for several reactions. Controlling coordination environments of SAC can be a promising strategy to achieve satisfactory catalytic performance. Our joint experimental and computational study shows that the coordination environments of Pt1/CeO2 can be designed quite precisely via a simple calcination temperature-control strategy. Pt1/CeO2 prepared at 550 oC are found to mainly substitute Ce atoms at the edge sites (Pt/CeO2-550) and are to be favored for CO oxidation reaction while those prepared at 800 oC mainly substitute Ce atoms on the terrace of CeO2 (Pt/CeO2-800) and are more effective for NH3 oxidation. First principles calculations reveal that CO oxidation on Pt/CeO2-550 does not require the consumption of surface O atoms while that on Pt/CeO2-800 does. Similarly, NH3 oxidation requires the consumption of surface O in both systems but the removal of surface O in Pt/CeO2-550 requires higher energy than that in Pt/CeO2-800. We will present an analysis of the geometric and electronic structure of the two types of Pt SAC that elucidate the origin of their contrasting reactivity. |
Monday, March 6, 2023 4:00PM - 4:12PM |
D32.00006: Dehydrofluorination as a residue-free selective route to C-C bond formation at metal surfaces. Sylvie Rangan, Jonathan Viereck, Yang Zhang, Elena Galoppini, Robert A Bartynski Directing covalent on-surface polymerization of molecular precursors through rational synthetic design has been impaired by the lack of control over reaction sites and by limited chemical routes to covalent bond formation between precursors, resulting in limited control of the outcomes and parasitic surface reaction by-products. Here, using scanning tunnel microscopy, temperature programmed desorption and electron spectroscopies, we investigate the mechanism of a recently reported chemical route to C-C bond formation: dehydrofluorination on metal surfaces. We demonstrate that this chemical route, involving specifically C-H/F-C pairs, favors the elimination of HF in the gas phase as a single step therefore eliminating reaction by-products at the surface of metals. Unlike dehalogenation, we find that the remarkable selectivity of the dehydrofluorination reaction renders this C-C bond formation strategy chemo-selective as well as potentially regio-selective, if employed with a properly designed molecular precursor. Additionally, we demonstrate that the catalytic role of the metal substrate can be used to steer reaction pathways and select between dehydrofluorination and dehydrogenation reaction. For these reasons, the dehydrofluorination reaction, largely unexplored on metal surfaces, could become a valuable tool for on-surface synthesis. |
Monday, March 6, 2023 4:12PM - 4:24PM |
D32.00007: Dynamic floating solid layers of hydrated ions at electrochemical Stern layer of the solid-liquid interfaces: X-ray crystal truncation rod (CTR) studies Hoydoo You, Michael S Pierce, Vladimir Komanicky, Tomoya Kawaguchi X-ray crystal truncation rod studies show highly dynamic floating solid-like overlayers of hydrated ions formed at electrified solid-metal interfaces. Electrochemical double layers (EDL) is traditionally described as diffuse distributions of cations and anions, proposed in Gouy and Chapman (GC) model [1] and further developed extensively over decades largely based on voltammetry measurements. However, the GC model is suspected to break down at large potentials, because it predicts the unlimited rise in differential capacitance. Stern suggested long ago that there should be a layer with a finite ion density, known as ‘Stern layer’ [2]. While it is generally accepted that Gouy-Chapman model or its modified versions describe well electrochemical interphase structures, recent studies of Pt(111) surface in CsF solution using a model-independent direct inversion method [3] have shown that Stern layer forms over the large double-layer potential range on Pt(111) surface. [4] In this talk, we present observation of dynamic behavior of Electrochemical Stern layers under electrochemical potential waves. The hydrated ions have enough masses to ‘push’ the metal surface layer with significant recoil forces at the time of departures. The measurements were repeated with Li, Na, K, and Cs to show the presence of the Stern layers regardless of the ions using the consistent behavior of the recoil forces. |
Monday, March 6, 2023 4:24PM - 4:36PM |
D32.00008: Adsorption and reaction of formic acid on Cu(111): The importance of the intermolecular interaction Ikutaro Hamada, Septia Eka Marsha Putra, Fahdzi Muttaqien, Yuji Hamamoto, Kouji Inagaki, Akitoshi Shiotari, Jun Yoshinobu, Yoshitada Morikawa Formic acid (HCOOH) is known to be catalytically decomposed on low index Cu surfaces into hydrogen and carbon dioxide via the formate (HCOO) intermediate. HCOOH is known to form polymeric (overlayer) structures on a Cu(111) surface. However, the structure of the polymeric HCOOH has been debated and is not yet fully understood. In this work, we use van der Waals inclusive density functional theory calculations in combination with scanning tunneling microscopy / atomic force microscopy and clarify the structural and vibrational properties of the polymeric HCOOH on a Cu(111) surface [1,2]. We also investigate the catalytic dehydrogenation of HCOOH in the overlayer structure and clarify the active site and the role of the edge and hydrogen-bonding formed between HCOOH molecules [1]. Furthermore, we clarify the formation of various chain-like HCOOH-HCOO and HCOO nanostructures, depending on the annealing temperature [2]. Our study reveals the importance of intermolecular interaction and serves as a fundamental step toward full understanding of the catalytic reaction of HCOOH and development of more efficient catalysts. |
Monday, March 6, 2023 4:36PM - 4:48PM |
D32.00009: Atomic-scale interface dynamics for Pt nanoparticles on SrTiO3 (001) Yanna Chen, Anusheela Das, Isaiah D Duplessis, Denis T Keane, Michael J Bedzyk Pt particles were grown on single-crystal SrTiO3 (001) surface using pulsed laser deposition. The Pt/SrTiO3heterostructure was characterized using X-ray standing wave (XSW) excited photoelectron spectroscopy (XPS). After measuring XSW excited core-level photoelectron emission, the atomic-scale interface 3D maps were plotted for all the interface atoms. The Pt and O atoms at the interface change occupation dependent on the oxidization process. Pt atoms also move upwards. Notably, after oxidization process, O atoms prefer to form TiO2 double layer at the interface and Pt-O bonds form at the top of O atoms. Strong metal-support interaction is confirmed at the interface through comparing the as-deposited and oxidated states. This approach would be beneficial to understand the strong metal-support interaction dynamically in catalysis reactions, especially at the metal-support interface. |
Monday, March 6, 2023 4:48PM - 5:00PM |
D32.00010: Investigating transport properties of chiral p-wave superconductors Arman Duha, Mario F Borunda Chiral p-wave superconductors are systems that might host Majorana fermions. One of the key telltale signs of Majorana bound states (MBS) is a metal-insulator transition when disorder is introduced in the host material. For example, quasiparticle localization by a space-dependent random mass M(r) with a variation on the scale of lattice constant results in a metal-insulator transition. On the other hand, a randomly varying electrostatic potential V(r) can create a random arrangement of MBS through the Shockley mechanism. In this numerical study, we investigate the combined effect of the disorders, the random mass and random local potential, on the transport of chiral p-wave superconductors. |
Monday, March 6, 2023 5:00PM - 5:12PM |
D32.00011: Extended Kohler’s Rule of Magnetoresistance in TaCo2Te2 Samuel E Pate, Samuel E Pate, Leyi Li, Bing Shen, Xiuquan Zhou, Duck Young Chung, Ralu Divan, Mercouri G Kanatzidis, Ulrich Welp, Wai-Kwong Kwok, Zhili Xiao TaCo2Te2 is recently reported to be an air-stable, high mobility Van der Waals material with probable magnetic order [1]. Here we investigate the scaling behavior of its magnetoresistance. We measured both the longitudinal and Hall magnetoresistivities of TaCo2Te2 crystals in magnetic fields parallel to the c-axis and found that the magnetoresistance violates the Kohler’s rule MR = f[H/ρ0] while obeying the extended Kohler’s rule MR = f[H/(nTρ0)] [2], where MR = [ρxx(H)-ρ0]/ρ0 with ρxx and ρ0 being the longitudinal resistivities at a fixed temperature with and without the presence of a magnetic field H, respectively. nT is a thermal factor governed by the temperature dependence of the carrier density, which can be experimentally determined from the Hall magnetoresistivities ρxy(H) obtained at various temperatures. |
Monday, March 6, 2023 5:12PM - 5:24PM |
D32.00012: Methods for Investigating the Thermal Hall Effect up to 32T Aaron L Chan, Guoxin Zheng, Dechen Zhang, Kuan-Wen Chen, Dmitri Mihaliov, Yuan Zhu, Kaila G Jenkins, Lu Li Currently, the bulk of thermometers used in cryogenic experiments are resistive thermometers such as Cernox and ruthenium oxide. However, under high magnetic fields (>5T), the aforementioned thermometers have magnetoresistance of several percent, causing them to be either unreliable or require extensive calibration. We explore two potential compounds that are much more stable in similar temperatures and fields. Strontium titanate (SrTiO3) is an effective capacitive thermometer that varies only by a few hundredths of a percent at high fields. We show that oxygen-18 exchanged strontium titanate thermometers can be used as the sensor for temperature control in the millikelvin range, and hope to adapt them for thermal transport measurements. Gold germanium (AuGe) is a resistive thermometer that has a much smaller magnetoresistance (~1%) and does not have the bulk or wiring issues of capacitive thermometry. We explore avenues to apply it as a thin-film thermometer for thermal transport measurements. |
Monday, March 6, 2023 5:24PM - 5:36PM |
D32.00013: Edge-sensitive intrinsic superconductivity of MoTe2 Stephan Kim, Bingzheng Han, Shiming Lei, Leslie M Schoop, Robert Cava, N. Phuan Ong We report that the intrinsic superconductivity of MoTe2 is sensitive to the kind of condensate that prevails on its edge mode. We prepared nanodevices from exfoliated MoTe2 crystals (50 – 100 nm in thickness). The physical edges of the devices were entirely covered by niobium electrodes, which were reported to be incompatible with the intrinsic condensate. [1] Gold electrodes were used to apply current and measure resistances. The resulting differential resistance dV/dI spectra versus applied current I and applied field μH showed modulations of critical currents corresponding to the area, even at high H. Such oscillations were the signature of proximitized edge mode by niobium condensates. Evidence of suppression of intrinsic condensate were observed; the critical current switching at μH < μHc of intrinsic condensate was deterministic. Moreover, cuts of the differential resistance spectra at zero applied bias did not show any anti-hysteretic changes of resistance or plateaus of resistance at small fields. |
Monday, March 6, 2023 5:36PM - 5:48PM |
D32.00014: Real-time dynamics and optical excitations of capacitively coupled quantum many-body heterostructures Julian Rincon, Carlos Salas We compute and analyze the optical excitations and real-time dynamics, induced by the light-matter interaction, of capacitively coupled heterostructures, composed of one-dimensional quantum many-body subsystems modeled by a Hubbard-like Hamiltonian. Our numerical study was carried out using time-dependent matrix product states. The optical excitations of the isolated subsystems are greatly modified due to the capacitive coupling between them. Remarkably, we find negative values for the optical conductivity of one of the subsystems for intermediate values of the capacitive coupling, evidencing a perfect negative drag effect due to the quantum entanglement of two perfectly interlocked charge density waves. At weak coupling, we detect optical excitations which are perturbatively connected to those of the isolated subsystems. Additionally, we find that the heterostructure tends to store capacitive energy at the expense of a reduction of the electron mobility. This effect has been observed experimentally in vertically-grown quantum wires. |
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