Lyudmila V. Moskaleva

Bio: Lyudmila V. Moskaleva is an academic researcher from University of Bremen. The author has contributed to research in topics: Adsorption & Ab initio. The author has an hindex of 24, co-authored 68 publications receiving 1881 citations. Previous affiliations of Lyudmila V. Moskaleva include Russian Academy of Sciences & Technische Universität München.

MoB/g-C3N4 Interface Materials as a Schottky Catalyst to Boost Hydrogen Evolution

Abstract: Proton adsorption on metallic catalysts is a prerequisite for efficient hydrogen evolution reaction (HER). However, tuning proton adsorption without perturbing metallicity remains a challenge. A Schottky catalyst based on metal–semiconductor junction principles is presented. With metallic MoB, the introduction of n-type semiconductive g-C3N4 induces a vigorous charge transfer across the MoB/g-C3N4 Schottky junction, and increases the local electron density in MoB surface, confirmed by multiple spectroscopic techniques. This Schottky catalyst exhibits a superior HER activity with a low Tafel slope of 46 mV dec−1 and a high exchange current density of 17 μA cm−2, which is far better than that of pristine MoB. First-principle calculations reveal that the Schottky contact dramatically lowers the kinetic barriers of both proton adsorption and reduction coordinates, therefore benefiting surface hydrogen generation.

The spin-conserved reaction CH+N2→H+NCN: A major pathway to prompt no studied by quantum/statistical theory calculations and kinetic modeling of rate constant

Abstract: A new spin-conserved path for the CH(2H)+N2 reaction at temperatures relevant to prompt NO formation has been theoretically investigated by means of ab initio MO calculations at the G2M level of theory. The result of the calculation reveals that the CH(2H)+N2 reaction takes place primarily via the ground electronic doublet potential energy surface, producing H+NCN instead of the commonly assumed, spin-forbidden HCN+N(4S) products. The overall rate constant for NCN production has been computed by a multichamel canonical variational Rice-Ramsperger-Kassel-Marcus theory calculation for the temperature range 1500–4000 K at 0.5–2 atm pressure: k3=2.22×107 T1.48 exp (−11760/T) cm3/(mol·s). The theoretically predicted rate constant was found to be in good agreement with high-temperature shock tube data kinetically modeled with the new mechahism that includes NCN reactions. In addition, k, was also found to be consistent with the apparent rate constants previously modeled for prompt NO formation in several flamer studies.

Silver residues as a possible key to a remarkable oxidative catalytic activity of nanoporous gold

Abstract: Recently, several forms of unsupportedgold were shown to display a remarkable activity to catalyze oxidation reactions. Experimental evidence points to the crucial role of residual silver present in very small concentrations in these novel catalysts. We focus on the catalytic properties of nanoporous gold (np-Au) foams probed viaCO and oxygen adsorption/co-adsorption. Experimental results are analyzed using theoretical models represented by the flat Au(111) and the kinked Au(321) slabs with Ag impurities. We show that Ag atoms incorporated into gold surfaces can facilitate the adsorption and dissociation of molecular oxygen on them. CO adsorbed on top of 6-fold coordinated Au atoms can in turn be stabilized by co-adsorbed atomic oxygen by up to 0.2 eV with respect to the clean unsubstituted gold surface. Our experiments suggest a linking of that most strongly bound CO adsorption state to the catalytic activity of np-Au. Thus, our results shed light on the role of silver admixtures in the striking catalytic activity of unsupported gold nanostructures.

Atomically dispersed nonmagnetic electron traps improve oxygen reduction activity of perovskite oxides

Abstract: Complexity in strongly correlated oxides such as perovskite strictly dominates their performance for oxygen reduction reaction (ORR). Precise control of the physical correlations among spin, charge, orbital, and lattice degrees of freedom in these oxides can exercise considerable enhancement of ORR activity, but has until now remained elusive. Here, we show that nonmagnetic hexavalent molybdenum (Mo6+) atomically dispersed within oxide lattice steers the intrinsic activity of catalytically active sites by entrapping extrinsic electrons at their 3d orbitals, without the occurrence of lattice symmetry breaking and magnetic perturbation. With double perovskite La2Co2+Mn4+O6 as a model catalyst, the atomic-scale electron trap generates additional high-spin, catalytically active Mn3+(t32ge1g) sites and highly conductive Co2+(e2g)–O–Mn3+(e1g) double exchange channels, leading to five-fold improvement in ORR activity. First-principles calculations reveal a substantial increase of the spin density on Mn sites caused by electron trapping, and unambiguously confirm a more exothermic reaction pathway as well as a lower barrier of the rate-limiting surface hydroxide regeneration on Mo1/La2CoMnO6. We can also extend this strategy with atomic precision easily to other four oxide catalysts and achieve large enhancement in their ORR activities as anticipated, indicating its broad utility. This work embodies the theories of condensed matter physics in rational design of ORR catalysts, and may inspire further development of the control of electron correlation in strongly correlated electron systems.

Microscopic models of PdZn alloy catalysts: structure and reactivity in methanol decomposition.

Abstract: We review systematic experimental and theoretical efforts that explored formation, structure and reactivity of PdZn catalysts for methanol steam reforming, a material recently proposed to be superior to the industrially used Cu based catalysts. Experimentally, ordered surface alloys with a Pd : Zn ratio of ∼1 : 1 were prepared by deposition of thin Zn layers on a Pd(111) surface and characterized by photoelectron spectroscopy and low-energy electron diffraction. The valence band spectrum of the PdZn alloy resembles closely the spectrum of Cu(111), in good agreement with the calculated density of states for a PdZn alloy of 1 : 1 stoichiometry. Among the issues studied with the help of density functional calculations are surface structure and stability of PdZn alloys and effects of Zn segregation in them, and the nature of the most likely water-related surface species present under the conditions of methanol steam reforming. Furthermore, a series of elementary reactions starting with the decomposition of methoxide, CH3O, along both C–H and C–O bond scission channels, on various surfaces of the 1 : 1 PdZn alloy [planar (111), (100) and stepped (221)] were quantified in detail thermodynamically and kinetically in comparison with the corresponding reactions on the surfaces Pd(111) and Cu(111). The overall surface reactivity of PdZn alloy was found to be similar to that of metallic Cu. Reactive methanol adsorption was also investigated by in situ X-ray photoelectron spectroscopy for pressures between 3 × 10−8 and 0.3 mbar.

Phd by thesis

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Density functional theory for transition metals and transition metal chemistry

Abstract: We introduce density functional theory and review recent progress in its application to transition metal chemistry. Topics covered include local, meta, hybrid, hybrid meta, and range-separated functionals, band theory, software, validation tests, and applications to spin states, magnetic exchange coupling, spectra, structure, reactivity, and catalysis, including molecules, clusters, nanoparticles, surfaces, and solids.

Recent Advances in Electrocatalytic Hydrogen Evolution Using Nanoparticles.

Abstract: Hydrogen fuel is considered as the cleanest renewable resource and the primary alternative to fossil fuels for future energy supply. Sustainable hydrogen generation is the major prerequisite to realize future hydrogen economy. The electrocatalytic hydrogen evolution reaction (HER), as the vital step of water electrolysis to H2 production, has been the subject of extensive study over the past decades. In this comprehensive review, we first summarize the fundamentals of HER and review the recent state-of-the-art advances in the low-cost and high-performance catalysts based on noble and non-noble metals, as well as metal-free HER electrocatalysts. We systemically discuss the insights into the relationship among the catalytic activity, morphology, structure, composition, and synthetic method. Strategies for developing an effective catalyst, including increasing the intrinsic activity of active sites and/or increasing the number of active sites, are summarized and highlighted. Finally, the challenges, perspectives, and research directions of HER electrocatalysis are featured.