Amorphous Ni3B Research Articles

Amorphous Ni3B Promotes Electroreduction of Nitrate to Ammonia.

The electrocatalytic nitrate reduction to ammonia (NRA) can address nitrogen cycle imbalance and high carbon emissions; however, the intense competition of hydrogen evolution reaction (HER) restricts the rate of NH3 production. Herein, amorphous Ni3B (a-Ni3B) is designed to balance the NRA and HER. The NH3 yield of a-Ni3B surpasses those of pure Ni and NiO, which is attributed to the preferential adsorption of NO3- on the B and Ni sites of a-Ni3B for the NRA reaction, greatly inhibiting the HER. Furthermore, the a-Ni3B possesses advantages in NRA performance compared to crystalline Ni3B (c-Ni3B) due to more active hydrogen (*H) generated during the catalytic process. The *H in the NRA process on a-Ni3B is verified by the electron spin resonance technique. The NRA mechanism is comprehensively discussed based on the results of in situ characterization and density functional theory calculations. The a-Ni3B can enhance NH3 production by inhibiting HER, which provides ideas for sustainable NH3 synthesis.

Structural Changes Observed during the Reversible Hydrogenation of Mg(BH4)2 with Ni-Based Additives

The decomposition and rehydrogenation of γ-Mg(BH4)2 ball milled together with 2 mol % of Ni-based additives, Ninano, NiCl2, NiF2, and Ni3B, has been investigated during one hydrogen desorption–absorption cycle. Under the applied ball-milling conditions, no mechanochemical reactions between γ-Mg(BH4)2 and Niadd were observed. Hydrogen desorption carried out at temperatures of 220–264 °C resulted for all samples in partial decomposition of Mg(BH4)2 and formation of amorphous phases, as seen by powder X-ray diffraction (PXD). PXD analysis after rehydrogenation at temperatures of 210–262 °C and at pressures between 100 and 155 bar revealed increased fractions of crystalline β-Mg(BH4)2, indicating a partial reversibility of the composite powders. The highest amount of [BH4]− is formed in the composite containing Ni3B. Analysis by X-ray absorption spectroscopy performed after ball milling, after desorption, and after absorption shows that the Ni3B additive remains unaffected, whereas NiCl2 and NiF2 additives react with Mg(BH4)2 during the hydrogen desorption–absorption and form compounds with a local structure very similar to that of amorphous Ni3B. Multinuclear NMR spectroscopy confirms the partial reversibility of the system as well as the formation of [B10H10]2– during hydrogen absorption. The presence of [BnHn]2– (n = 10, 12) was also detected by infrared (IR) spectroscopy of the dehydrogenated and rehydrogenated samples. The IR measurements give no clear indication that ions containing B–H–B bridged hydrogen groups were formed during the H-sorption cycle.

Selection of peptides binding to metallic borides by screening M13 phage display libraries

BackgroundMetal borides are a class of inorganic solids that is much less known and investigated than for example metal oxides or intermetallics. At the same time it is a highly versatile and interesting class of compounds in terms of physical and chemical properties, like semiconductivity, ferromagnetism, or catalytic activity. This makes these substances attractive for the generation of new materials. Very little is known about the interaction between organic materials and borides. To generate nanostructured and composite materials which consist of metal borides and organic modifiers it is necessary to develop new synthetic strategies. Phage peptide display libraries are commonly used to select peptides that bind specifically to metals, metal oxides, and semiconductors. Further, these binding peptides can serve as templates to control the nucleation and growth of inorganic nanoparticles. Additionally, the combination of two different binding motifs into a single bifunctional phage could be useful for the generation of new composite materials.ResultsIn this study, we have identified a unique set of sequences that bind to amorphous and crystalline nickel boride (Ni3B) nanoparticles, from a random peptide library using the phage display technique. Using this technique, strong binders were identified that are selective for nickel boride. Sequence analysis of the peptides revealed that the sequences exhibit similar, yet subtle different patterns of amino acid usage. Although a predominant binding motif was not observed, certain charged amino acids emerged as essential in specific binding to both substrates. The 7-mer peptide sequence LGFREKE, isolated on amorphous Ni3B emerged as the best binder for both substrates. Fluorescence microscopy and atomic force microscopy confirmed the specific binding affinity of LGFREKE expressing phage to amorphous and crystalline Ni3B nanoparticles.ConclusionsThis study is, to our knowledge, the first to identify peptides that bind specifically to amorphous and to crystalline Ni3B nanoparticles. We think that the identified strong binding sequences described here could potentially serve for the utilisation of M13 phage as a viable alternative to other methods to create tailor-made boride composite materials or new catalytic surfaces by a biologically driven nano-assembly synthesis and structuring.

Characterisation by various microscopic techniques of the damage created by MeV C60 ions in amorphous Ni3B

In the work presented here, we study the damage resulting from the high rates of energy deposition in electronic processes during the slowing down of energetic projectiles in amorphous Ni3B. More precisely, we study the structural modifications of the targets irradiated at 300 K in a wide range of fluences (109–5×1011 cm−2) with 30 MeV C60 ions. The experimental results mainly concern the surface features and were obtained by Transmission Electron Microscopy (TEM) using in particular phase contrast and topographical contrast imaging. In the case of C60 ions, TEM reveals that surface damage consists of approximatively 20 nm diameter hollows, which are surrounded by protuding rims. This seems to indicate that the anisotropic growth process, which is specific of amorphous structures, is induced by each individual C60 cluster ion. Previous results obtained using GeV heavy monoatomic projectiles showed that the plastic deformation of the targets started only above an incubation fluence, i.e. after a significant spatial overlap of the damaged regions.

Visualization in an electron microscope of the impact of energetic projectiles in amorphous targets

Crystalline and amorphous Ni 3B have been irradiated at 300 K with GeV uranium ions and with 30 MeV C 60 fullerene ions. These projectiles deposit a very large amount of energy in the targets via electronic excitation and ionization, which results in the creation of amorphous tracks in the crystalline compound and of ‘disordered amorphous’ matter lying in the vicinity of the projectile path in the initially amorphous target, which is the first state leading to the well-known anisotropic growth of amorphous materials submitted to high electronic excitations. It is shown here that it is possible to directly visualize in an electron microscope the impact of the ions in the amorphous targets. This allows us to compare the sizes of the observed impacts with those of disordered regions that were previously extracted from phenomenological models describing damage creation in amorphous matter and to compare the extension of damaged regions induced in the same compound when bombarded in its crystalline and amorphous forms.

Creep of a crystalline metallic layer induced by high energy heavy ion irradiation

The atomic transport induced by ion electronic energy loss in amorphous systems is studied on metallic sandwiches irradiated at liquid nitrogen temperature with 500 MeV iodide ions delivered by the VICKSI accelerator of the Hahn-Meitner-Institut (Berlin). The sandwiches are composed of two amorphous Ni3B layers of 1 or 1.5 μm thickness embedding a crystalline Au or W layer of thickness varying from 20 to 900 nm. Rutherford backscattering experiments using a 3.6 MeV He2+ beam delivered by the ARAMIS accelerator of the CSNSM (Orsay) were performed in order to determine the modifications of the geometry of the sandwiches after swift heavy ion irradiation. The results show a huge creep of the crystalline part of the sandwiches. The magnitude of this creep depends on the nature of the crystalline layer (Au or W) and increases steadily with the irradiating ion fluence with a strain-rate decreasing with increasing layer thickness. This creep phenomenon is due to the plastic deformation process occurring in the surrounding amorphous layers and is induced by ion electronic energy loss. A simple rheological model is developed to reproduce the observed effects.

Creep of a crystalline metallic layer induced by GeV heavy ion irradiation

The atomic transport induced in amorphous systems by ion electronic energy loss is studied on metallic sandwiches irradiated with 500 MeV iodine ions. The sandwiches are composed of two amorphous Ni 3B layers of thickness 1-1.5 μm and of one crystalline Au or W layer of thickness varying from 20 to 900 nm. Rutherford backscattering experiments using a 3.6 MeV He beam were performed to determine the modifications of the geometry of the sandwiches due to irradiation. A huge creep phenomenon is evidenced in the crystalline part of the sample. The amplitude of the creep depends on the nature of the crystalline layer (Au or W) and decreases with the layer thickness. This creep phenomenon is induced by the plastic deformation process occurring in the amorphous layers surrounding the crystalline one, and is due to ion electronic energy loss.

New insight on the ion beam-induced plastic deformation in amorphous alloys by marker experiments

Abstract The macroscopic atomic transport induced in amorphous systems by ion electronic energy loss is studied by means of RBS experiments on a marker either implanted (Bi) or evaporated (Au) in the target. Irradiation of amorphous Ni3B with 500 MeV I ions leads to (i) a huge shift of the marker profile towards the sample surface, (ii) a surprising decrease of its distribution width. The results are totally accounted for by the plastic deformation phenomenon induced by electronic excitation in amorphous materials.

Structural modifications of crystalline and amorphous Ni 3B irradiated with high-energy heavy ions

Crystalline and amorphous Ni 3B ribbons have been irradiated at low temperature with GeV heavy ions in order to study the structural modifications induced in metallic alloys by ion electronic energy loss. The atomic rearrangements produced by irradiation were characterized via in situ electrical resistance measurements and room-temperature X-ray and electron diffraction. Amorphous Ni 3B behaves as the other amorphous alloys already investigated: creation of disorder with a cross section increasing with the ion electronic stopping power, followed by an anisotropic growth of the sample dimensions. Crystalline Ni 3B shows a new and very interesting behavior: a huge electrical resistivity increase above an electronic energy loss threshold attributed to amorphization of the irradiated alloy.

Metaemission and photoemission spectroscopies of amorphous Ni 3B surface electronic structure: Evolution during crystallization and O 2 or CO adsorption

Metaemission and photoemission spectroscopies were combined to probe the density of occupied electronic states in the outermost layer and at various depths in amorphous or crystalline Ni 3B. Clear differences were observed between the bulk and surface electronic structures in both states, indicating a lower hybridization of B orbitals at the surface. Structural disorder induces a smearing out of B states in the bulk of the glass (with respect to the crystal), and a lower density of B 2p unhybridized states at its surface. This difference in the surface electronic structures could explain the lower reactivity of the glass with O 2 or CO.