First-row Transition Metal Elements Research Articles

The Role of Metal Ions in Fungal Organic Acid Accumulation.

Organic acid accumulation is probably the best-known example of primary metabolic overflow. Both bacteria and fungi are capable of producing various organic acids in large amounts under certain conditions, but in terms of productivity-and consequently, of commercial importance-fungal platforms are unparalleled. For high product yield, chemical composition of the growth medium is crucial in providing the necessary conditions, of which the concentrations of four of the first-row transition metal elements, manganese (Mn2+), iron (Fe2+), copper (Cu2+) and zinc (Zn2+) stand out. In this paper we critically review the biological roles of these ions, the possible biochemical and physiological consequences of their influence on the accumulation of the most important mono-, di- and tricarboxylic as well as sugar acids by fungi, and the metal ion-related aspects of submerged organic acid fermentations, including the necessary instrumental analytics. Since producing conditions are associated with a cell physiology that differs strongly to what is observed under “standard” growth conditions, here we consider papers and patents only in which organic acid accumulation levels achieved at least 60% of the theoretical maximum yield, and the actual trace metal ion concentrations were verified.

Dealloying Ni-Co-Se Electrocatalysts for Efficient and Stable Oxygen Evolution at High Current Densities

Stable and affordable electrocatalysts are urgently needed to accelerate the transition from conventional fossil fuels to sustainable energy resources such as solar and wind. Over the last two decades, the electrocatalytic splitting of water, and carbon dioxide reduction to hydrocarbons have received great attention, however approximately 90% of the electricity input is consumed at the anodic oxygen evolution reaction (OER) due to poor reaction kinetics. Precious metal-based electrocatalysts (Pt, Ir, Ru) have been commonly used as OER catalysts, but proven uneconomic for large scale industrial deployment. First-row transition metal elements (Ni, Co, Fe) offer a great earth abundant and low-cost alternative for OER.In this work, we used a two-step novel milling process to produce Ni,Co-based nanocrystalline electrocatalysts. Cryo-milling (mechanical milling of precursors at cryogenic temperatures to achieve alloying) followed by surfactant-assisted ball milling (SABM), to reduce particles to nanoparticle, create stable disordered phases with high surface areas and coordinatively unsaturated active sites for the reaction of OER intermediates.Two Ni-Co-Se alloys were milled under various conditions and the structural evolution of the systems was monitored using X-ray diffraction (XRD) and electron microscopy. Our results confirmed the production of two fully alloyed ternary systems (NiCo)3Se4 and (NiCo)Se after 6 hours of milling time. The electrocatalytic activity and stability of the catalysts were evaluated by Tafel measurements obtained from linear sweep voltammetry (LSV) and cyclic voltammetry (CV) experiments. We found that Se in NiCo-based alloys stabilized the disordered structure by forming non-transitional clusters and significantly facilitated the production of nanoparticles. In situ X-ray Absorption Spectroscopy (XAS) and electron microscopy revealed that Se was dealloyed during the OER reaction activating the electrocatalysts by facilitating the formation of active Ni-Co oxyhydroxides. On a glassy carbon electrode at 10 mA.cm-2, activated (NiCo)3Se4 demonstrated a stable performance for 500 hours at 268 mV overpotential with a Tafel slope of 42 mV.dec-1. Moreover, the the catalyst was stable for 100 hours while delivering 500 mA.cm-2 at 320 mV of overpotential. This work suggests that milling can potentially be used to produce OER catalysts for industrial application.

Topological Spin-Charge Gearbox on a Real Molecular Magnet.

In this work, using ab initio many-body theory and inspired by an idea suggested by G. D. Mahan for an abstract N-dimensional chain composed of s-type atoms ( Phys. Rev. Lett. 2009, 102, 016801), we propose a functional topological spin-charge gearbox based on the real synthesized Co3Ni(EtOH) cluster driven with laser pulses. We analyze the implications arising from the use of a real molecule with d-character functional orbitals rather than an extended system and discuss the role of the point group symmetry of the system and the transferability of the electronic and spin density between different many-body states using specially designed laser pulses. We thus find that first-row transition-metal elements can host unpaired yet correlated d electrons and thus act as sites for spin information carriers, while designated laser pulses induce symmetry operations leading to a realizable spin-charge gearbox.

Structural, electronic and magnetic properties of some early vs late transition dimetallaborane clusters – A theoretical investigation

The strength of DFT methods in analyzing the electronic and magnetic properties of a series of dimetallaboranes of varied stoichiometry and architectural core, namely M2B3, M2B4 and M2B5 with both early- and late-transition metals is demonstrated. In particular, the observed 1H and 11B chemical shifts of most of the studied compounds are reproduced with a good accuracy of a few ppm at the DFT-GIAO BP86/TZ2P/SC level for the compounds with first-row transition metal elements and at the B3LYP/TZ2P/SO level for those with second- and third-row transition metal elements. This allows structural applications in elucidating the number and the location of bridging hydrogen atoms in experimentally poorly characterized metallaboranes such as (Cp*Cr)2B4H8.

Toward accurate thermochemical models for transition metals: G3Large basis sets for atoms Sc–Zn

An augmented valence triple-zeta basis set, referred to as G3Large, is reported for the first-row transition metal elements Sc through Zn. The basis set is constructed in a manner similar to the G3Large basis set developed previously for other elements (H-Ar, K, Ca, Ga-Kr) and used as a key component in Gaussian-3 theory. It is based on a contraction of a set of 15s13p5d Gaussian primitives to 8s7p3d, and also includes sets of f and g polarization functions, diffuse spd functions, and core df polarization functions. The basis set is evaluated with triples-augmented coupled cluster [CCSD(T)] and Brueckner orbital [BD(T)] methods for a small test set involving energies of atoms, atomic ions, and diatomic hydrides. It performs well for the low-lying s-->d excitation energies of atoms, atomic ionization energies, and the dissociation energies of the diatomic hydrides. The Brueckner orbital-based BD(T) method performs substantially better than Hartree-Fock-based CCSD(T) for molecules such as NiH, where the starting unrestricted Hartree-Fock wavefunction suffers from a high degree of spin contamination. Comparison with available data for geometries of transition metal hydrides also shows good agreement. A smaller basis set without core polarization functions, G3MP2Large, is also defined.

Rare earth-first-row transition metal perovskites as catalysts for the autothermal reforming of hydrocarbon fuels to generate hydrogen☆

Perovskite oxides (ABO3) containing rare earth elements on the A-site and first-row transition metal elements on the B-site were studied as catalysts for autothermal reforming of liquid hydrocarbon fuels to produce hydrogen for fuel cell systems. Experiments were conducted in a fixed bed microreactor at temperatures of 600–800 °C and gas-hourly space velocities (GHSV) ranging from 4600 to 28,000 h−1 using 2,2,4-trimethylpentane (isooctane) as a surrogate fuel. We have found that the two binary oxides, LaNiO3 and LaCoO3, produced high yields of H2, but were not structurally stable. These perovskites decomposed to La2O3 and Ni/NiO or Co/CoO under the reducing conditions present in the reformer. Three other binary oxides, LaCrO3, LaFeO3, and LaMnO3, were structurally stable but significantly less active than LaNiO3 and LaCoO3. The partial substitution of chromium, iron, aluminum, gallium, or manganese on the B-site of LaNiO3 to yield LaBxNi1−xO3 was shown to improve the structural stability without a significant decrease in the H2 yield. The effects of substituting rare earth elements for La and the substitution of alkaline earth elements on the A-site (La1−yAyBxNi1−xO3) on catalyst performance and stability were also investigated. Finally, La0.8Sr0.2M0.9Ni0.1O3 catalysts (where M = Cr, Mn, or Fe) were tested with a “benchmark fuel” mixture containing from 0 to 50 ppmw sulfur. These tests showed that using chromium as a stabilizing element in LaNiO3 imparts the most sulfur tolerance.

Parameter Calibration of Transition-Metal Elements for the Spin-Polarized Self-Consistent-Charge Density-Functional Tight-Binding (DFTB) Method: Sc, Ti, Fe, Co, and Ni.

Recently developed parameters for five first-row transition-metal elements (M = Sc, Ti, Fe, Co, and Ni) in combination with H, C, N, and O as well as the same metal (M-M) for the spin-polarized self-consistent-charge density-functional tight-binding (DFTB) method have been calibrated. To test their performance a couple sets of compounds have been selected to represent a variety of interactions and bonding schemes that occur frequently in transition-metal containing systems. The results show that the DFTB method with the present parameters in most cases reproduces structural properties very well, but the bond energies and the relative energies of different spin states only qualitatively compared to the B3LYP/SDD+6-31G(d) density functional (DFT) results. An application to the ONIOM(DFT:DFTB) indicates that DFTB works well as the low level method for the ONIOM calculation.

Systematically convergent basis sets for transition metals. I. All-electron correlation consistent basis sets for the 3d elements Sc–Zn

Sequences of basis sets that systematically converge towards the complete basis set (CBS) limit have been developed for the first-row transition metal elements Sc-Zn. Two families of basis sets, nonrelativistic and Douglas-Kroll-Hess (-DK) relativistic, are presented that range in quality from triple-zeta to quintuple-zeta. Separate sets are developed for the description of valence (3d4s) electron correlation (cc-pVnZ and cc-pVnZ-DK; n = T,Q, 5) and valence plus outer-core (3s3p3d4s) correlation (cc-pwCVnZ and cc-pwCVnZ-DK; n = T,Q, 5), as well as these sets augmented by additional diffuse functions for the description of negative ions and weak interactions (aug-cc-pVnZ and aug-cc-pVnZ-DK). Extensive benchmark calculations at the coupled cluster level of theory are presented for atomic excitation energies, ionization potentials, and electron affinities, as well as molecular calculations on selected hydrides (TiH, MnH, CuH) and other diatomics (TiF, Cu2). In addition to observing systematic convergence towards the CBS limits, both 3s3p electron correlation and scalar relativity are calculated to strongly impact many of the atomic and molecular properties investigated for these first-row transition metal species.

04/01813 Process for production of hydrocarbons by steam reforming: Abbott, P. E. J. and Fernie, M. J. PCT Int. Appl. WO 03 62,142 (Cl. C01B3/38), 31 Jul 2003, GA Appl. 2002/891

Perovskite oxides (ABO3) containing rare earth elements on the A-site and first-row transition metal elements on the B-site were studied as catalysts for autothermal reforming of liquid hydrocarbon fuels to produce hydrogen for fuel cell systems. Experiments were conducted in a fixed bed microreactor at temperatures of 600–800 °C and gas-hourly space velocities (GHSV) ranging from 4600 to 28,000 h−1 using 2,2,4-trimethylpentane (isooctane) as a surrogate fuel. We have found that the two binary oxides, LaNiO3 and LaCoO3, produced high yields of H2, but were not structurally stable. These perovskites decomposed to La2O3 and Ni/NiO or Co/CoO under the reducing conditions present in the reformer. Three other binary oxides, LaCrO3, LaFeO3, and LaMnO3, were structurally stable but significantly less active than LaNiO3 and LaCoO3. The partial substitution of chromium, iron, aluminum, gallium, or manganese on the B-site of LaNiO3 to yield LaBxNi1−xO3 was shown to improve the structural stability without a significant decrease in the H2 yield. The effects of substituting rare earth elements for La and the substitution of alkaline earth elements on the A-site (La1−yAyBxNi1−xO3) on catalyst performance and stability were also investigated. Finally, La0.8Sr0.2M0.9Ni0.1O3 catalysts (where M = Cr, Mn, or Fe) were tested with a “benchmark fuel” mixture containing from 0 to 50 ppmw sulfur. These tests showed that using chromium as a stabilizing element in LaNiO3 imparts the most sulfur tolerance.

Coupling between phonons and quantum rotors

Quantum free-rotors in crystalline solids are exceedingly rare, but have recently been found for NH 3 groups in several Hofmann clathrates: M a(NH 3) 2M b(CN) 4 · 2C 6D 6, where M a and M b are first-row transition metal elements. Above 4.0 K the spectrum of the NH 3 J = 0 J = 1 transitions broadens, and at around 30 K the inelastic peaks are Lorentzianshaped with appreciable intensity spreading beyond 1 meV. Because the rotational constant for NH 3 ≈ 0.71meV, any inhomogeneous broadening of the J = 0 J = 1 peaks cannot extend beyond this value. A model based on resonance of the rotational system with phonons suggests interaction with librational motions of the benzene molecules.