Interstitial Boron Atoms Research Articles

Interstitial Boron Atoms in Pd Aerogel Selectively Switch the Pathway for Glycolic Acid Synthesis from Waste Plastics.

Electro-reforming of poly(ethylene terephthalate) (PET) into valuable chemicals is garnering significant attention as it opens a mild avenue for waste resource utilization. However, achieving high activity and selectivity for valuable C2 products during ethylene glycol (EG) oxidation in PET hydrolysate on Pd electrocatalysts remains challenging. The strong interaction between Pd and carbonyl (*CO) intermediates leads to undesirable over-oxidation and poisoning of Pd sites, which hinders the highly efficient C2 products production. Herein, a nonmetallic alloying strategy is employed to fabricate a Pd-boron alloy aerogel (PdB), wherein B atoms are induced to regulate the electron structure and surface oxophilicity. This approach allows a remarkable mass activity of 6.71 A mgPd -1, glycolic acid (GA) Faradaic efficiency (FE) of 93.8%, and stable 100 h cyclic electrolysis. In situ experiments and density functional theory calculations reveal the contributions of B inserted in Pd lattice on highly effective EG-to-GA conversion. Interestingly, the heightened surface oxophilicity and regulated electronic structure by B incorporation weakened *CO intermediates adsorption and enhanced hydroxyl species affinity to accelerate oxidative *OH adspecies formation, thereby synergistically avoiding over-oxidation and boosting GA synthesis. This work provides valuable insights for the rational design of high-performance electrocatalysts for GA synthesis via an oxophilic B motifs incorporation strategy.

Thermodynamical stability of carbon-based defects in α boron from first principles

We report an exhaustive study of the formation enthalpy and charge states of carbon-based defects in rhombohedral α boron within the density functional theory (DFT) that enables us to derive rules about the formation of complex carbon defects. We have accounted for one and two interstitial carbon atoms, eventually combined with one substitutional carbon atom and/or one interstitial boron atom and varied several geometric parameters. We find that when positioned in the plane perpendicular to the [111] rhombohedral axis, two carbon atoms turn out to preferentially form a graphite-like hexagon with four boron atoms. When positioned instead along the [111] axis, the distance between them strongly affects the defect thermodynamic stability, and we find in particular that additional negative charges strongly stabilize the diatomic carbon–carbon chains.

Gain recovery in heavily Irradiated Low Gain Avalanche Detectors by high temperature annealing

Studies of annealing at temperatures up to 450 °C with Low Gain Avalanche Detectors (LGAD) irradiated with neutrons are described. It was found that the performance of LGADs irradiated with 1.5e15 n/cm2 was already improved at 5 min of annealing at 250 °C. Isochronal annealing for 30 min in 50 °C steps between 300 °C and 450 °C showed that the largest beneficial effect of annealing is at around 350 °C. Another set of devices was annealed for 60 min at 350 °C and this annealing significantly increased depletion voltage of the gain layer (Vgl). The effect is equivalent to reducing the effective acceptor removal constant by a factor of ∼ 4. Increase of Vgl is the consequence of increased effective space charge in the gain layer caused by formation of electrically active defects or re-activation of interstitial boron atoms.

Tuning deformation mechanisms of face-centered-cubic high-entropy alloys via boron doping

Face-centered-cubic (FCC) high-entropy alloys (HEAs) can be strengthened through boron doping. However, the existing form of boron and its effect on the deformation mechanism of FCC HEAs have been rarely reported. The present work demonstrates for the first time the effect of the interstitial boron and boron-rich precipitate on the deformation mechanisms of the FCC (CoCrFeNi) HEAs. The dominant deformation mechanism of CoCrFeNi HEAs is dislocation slip, whereas the interstitial boron atoms dissolved in the matrix, thereby reducing the stacking fault energy (SFE) and transforming the dominant deformation mechanism to deformation twins. The loss of Cr from the matrix after boride formation increased the SFE, which led to transforming the dominant deformation mechanism from deformation twins to dislocation slip. Based on the results, we firstly propose to tune the deformation mechanism of FCC HEAs via boron doping, which provide a new strategy for designing and optimizing the HEAs. • Adding boron to CoCrFeNi HEA can significantly improve the yield strength. • The different existing form of boron will change the SFE of CoCrFeNi HEA, thereby affecting its deformation mechanism. • We firstly propose to tune the deformation mechanism of FCC HEAs via boron doping.

Interstitial boron-doped nanoporous palladium film for electro-reduction of nitrogen to ammonia

Electrocatalytic nitrogen reduction to ammonia has attracted abundant research interest due to its mild operation condition and sustainable feedstock. The identification of efficient catalysts with high selectivity of nitrogen reduction is the key for the electro-synthesis of ammonia. Herein, interstitial boron-doped nanoporous palladium film is directly formed on Ni foam (nPdB/NF) via micelle-assisted reduction method using borane dimethylamine complex as reducing agents and boron dopant. The binder-free nanoporous structure provides abundant active sites and facilitated mass/charge transfer. Moreover, the introduction of interstitial boron atoms can modify the electronic structure of Pd, which can both improve the nitrogen adsorption and inhibit hydrogen evolution on nPdB/NF. As such, nPdB/NF exhibits high NH3 yield of 29.0 μg h−1 mg−1cat. and Faraday efficiency of 17.9% in 0.1 M Na2SO4, superior to that of nPd/NF (19.7 μg h−1 mg−1cat and 14.7%). This work offers an attractive method for the introduction of interstitial boron into Pd-based catalysts to improve NRR performance.

Regulating the intermediate affinity on Pd nanoparticles through the control of inserted-B atoms for alkaline hydrogen evolution

• The Pd-B/C with the control of inserted-B atoms are synthesized by a facile route. • The optimized Pd-B/C catalyst exhibit superior alkaline HER activity. • The inserted boron atoms is beneficial to regulate the intermediate affinity on Pd. Strong affinity of palladium to hydrogen needs to be overcome in the rational design of highly efficient and robust Pd-based catalyst for hydrogen evolution reaction (HER). In this work, we achieved the insertion of boron atoms in the Pd lattice interstitial sites by a facile co-reduction method, and successfully prepared Pd-B nanoparticles supported on carbon. Benefiting from the optimization of electronic state induced by the control of interstitial boron atoms, the obtained Pd 86 B 14 /C catalyst exhibit pronounced alkaline HER performance with a small overpotential of 38 mV at 10 mA cm −2 and a low Tafel slope of 36.6 mV dec −1 in 1 M KOH. Theoretical calculations unveil that the inserted boron atoms into host palladium leads to the charge redistribution and the lower d-band center on Pd because of the electron transfer between Pd and inserted B. More importantly, the control of inserted boron atoms makes the d-band center of Pd appropriately shift negatively relative to the Fermi level and consequently balances the hydrogen adsorption/desorption behavior of Pd surface, resulting in superior catalytic performance (Pd 86 B 14 /C).

Realization of interstitial boron ordering and optimal near-surface electronic structure in Pd-B alloy electrocatalysts

The fundamental understanding and precise tuning of interatomic s,p-d orbital hybridization are critical to the design of interstitial alloy catalysts containing light constituent atoms. Here, we present a joint theoretical and experimental study that reveals the importance of distribution, concentration and ordering of interstitial boron atoms in Pd-B alloy’s near-surface electronic structure and catalytic performance. Our theoretical results demonstrate that the sub-surface location of interstitial boron atoms with a Pd:B atomic ratio of 2:1 is necessary to ensure an appropriate degree of interatomic s,p-d orbital hybridization, and thereby an optimal surface electronic structure for the hydrogen evolution reaction (HER). We experimentally achieve this with highly-crystalline intermetallic Pd2B. Due to its optimal electronic structure and ordered arrangement of interstitial boron atoms, the intermetallic Pd2B exhibits Pt-like catalytic activity for HER and has excellent catalytic stability for over seven days.

Boranes: The Boron Subhydride B104.67H3 with a Distorted β-Boron Crystal Structure.

A single crystal of the boron subhydride B104.67(4)H3 was serendipitously obtained while attempting to synthesize β-boron. An accurate crystal structure analysis revealed a distorted β-boron framework with the noncentrosymmetric space group R3m. We have found one interstitial site occupied by boron. The site related by inversion remains empty. The distortions of the framework result in ideal environments for the interstitial boron atom, and for the three hydrogen atoms at bridging positions between icosahedral B12 groups, they result in ideal B-H distances of 1.33 Å. B104.67(4)H3 is a borane with the lowest amount of hydrogen recorded to date, and it is the first compound with a noncentrosymmetrically distorted β-boron framework.

Interstitial Boron Atoms in the Palladium Lattice of an Industrial Type of Nanocatalyst: Properties and Structural Modifications.

It is well-established that the inclusion of small atomic species such as boron (B) in powder metal catalysts can subtly modify catalytic properties, and the associated changes in the metal lattice imply that the B atoms are located in the interstitial sites. However, there is no compelling evidence for the occurrence of interstitial B atoms, and there is a concomitant lack of detailed structural information describing the nature of this occupancy and its effects on the metal host. In this work, we use an innovative combination of high-resolution 11B magic-angle-spinning (MAS) and 105Pd static solid-state NMR nuclear magnetic resonance (NMR), synchrotron X-ray diffraction (SXRD), in situ X-ray pair distribution function (XPDF), scanning transmission electron microscopy-annular dark field imaging (STEM-ADF), electron ptychography, and electron energy loss spectroscopy (EELS) to investigate the B atom positions, properties, and structural modifications to the palladium lattice of an industrial type interstitial boron doped palladium nanoparticle catalyst system (Pd-intB/C NPs). In this study, we report that upon B incorporation into the Pd lattice, the overall face centered cubic (FCC) lattice is maintained; however, short-range disorder is introduced. The 105Pd static solid-state NMR illustrates how different types (and levels) of structural strain and disorder are introduced in the nanoparticle history. These structural distortions can lead to the appearance of small amounts of local hexagonal close packed (HCP) structured material in localized regions. The short-range lattice tailoring of the Pd framework to accommodate interstitial B dopants in the octahedral sites of the distorted FCC structure can be imaged by electron ptychography. This study describes new toolsets that enable the characterization of industrial metal nanocatalysts across length scales from macro- to microanalysis, which gives important guidance to the structure-activity relationship of the system.

Hydrogenation, dehydrogenation of α-tetragonal boron and its transition to δ-orthorhombic boron

Boron bulk crystals are marked by exceptional structural complexity and unusual related physical phenomena. Recent reports of hydrogenated α-tetragonal and a new δ-orthorhombic boron B52 phase have raised many fundamental questions. Using density functional theory calculations it is shown that hydrogenated α-tetragonal boron has at least two stable stoichiometric compositions, B51H7 and B51H3. Thermodynamic modeling was used to qualitatively reproduce the two-step phase transition reported by (Ekimov et al 2016 J. Mater. Res. 31, 2773) upon annealing, which corresponds to successive transitions from B51H7 to B51H3 to pure B52. The so obtained δ-orthorhombic boron is an ordered, low-temperature phase and α-tetragonal boron is a disordered, high-temperature phase of B52. The two phases are connected by an order-disorder transition, that is associated with the migration of interstitial boron atoms. Atom migration is usually suppressed in strongly bound, covalent crystals. It is shown that the migration of boron atoms is likely to be assisted by the migration of hydrogen atoms upon annealing. These results are in excellent agreement with the above mentioned experiment and they represent an important step forward for the understanding of boron and hydrogenated boron crystals. They further open a new avenue to control or remove the intrinsic defects of covalently bound crystals by utilizing volatile, foreign atoms.

Diffusion Paths for Interstitial Impurities in Different Polymorphic Modifications of Niobium Silicide Nb5Si3

Structural models of the α, β, and γ modifications of Nb5Si3 silicides, which are used as a reinforcing phase in composites obtained in situ based on the Nb‒Si system, have been constructed by computer simulation methods. A geometric analysis of unit cells is performed using the H-poisk program to estimate the voids existing in the structures. The results of measuring the number of voids and their sizes are reported. A conclusion about possible diffusion paths of interstitial boron, carbon, nitrogen and oxygen atoms is drawn based on the calculation results, and the solubility of these impurities in the structure of each Nb5Si3 modification is estimated.

Evolution of anisotropy in bcc Fe distorted by interstitial boron

The evolution of magnetic anisotropy in bcc Fe as a function of interstitial boron atoms was investigated in thin films grown by molecular beam epitaxy. The thermodynamic nonequilibrium conditions during film growth allowed one to stabilize an interstitial boron content of about $14\phantom{\rule{0.28em}{0ex}}\mathrm{at}.\phantom{\rule{0.16em}{0ex}}%$ accompanied by lattice tetragonalization. The $c/a$ ratio scaled linearly with the boron content up to a maximum value of 1.05 at $300{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$ substrate growth temperature, with a room-temperature magnetization of. In contrast to nitrogen interstitials, the magnetic easy axis remained in-plane with an anisotropy of approximately $\ensuremath{-}5.1\ifmmode\times\else\texttimes\fi{}{10}^{6}\phantom{\rule{0.28em}{0ex}}\mathrm{erg}/{\mathrm{cm}}^{3}$. Density functional theory calculations using the measured lattice parameters confirm this value and show that boron local ordering indeed favors in-plane magnetization. Given the increased temperature stability of boron interstitials as compared to nitrogen interstitials, this study will help to find possible ways to manipulate boron interstitials into a more favorable local order.

Effect of High Configuration Entropy and Rare Earth Addition on Boride Precipitation and Mechanical Properties of Multi-principal-Element Alloys

A series of multi-principal-element (MPE) alloys have been prepared by adding Ni, Mn, Al, Cu and Y into the reference CoCrFe-B alloy. The microstructure and mechanical properties of these MPE alloys have been investigated thoroughly. It is found that the addition of the elements can inhibit boride precipitation in the designed alloys and the solid solution strengthening effect induced by interstitial boron atoms is more significant than that by boride precipitation. The MPE alloys with the fcc phase as the main solid solution phase have a higher boron solubility and hence less boride precipitation, than those with the bcc phase as the main solid solution phase. The addition of yttrium can improve the boron solubility, decrease boride precipitation, control the boride morphology and, importantly, simultaneously improve the compressive strength and ductility of boron-containing MPE alloys.

Effect of Heat Treatment on Borides Precipitation and Mechanical Properties of CoCrFeNiAl1.8Cu0.7B0.3Si0.1 High-Entropy Alloy Prepared by Arc-Melting and Laser-Cladding

Effects of heat treatment on borides precipitation and mechanical properties of arc-melted and laser-cladded CoCrNiFeAl1.8Cu0.7B0.3Si0.1 high-entropy alloys were comparatively studied. The arc-melted alloy contains lots of long strip borides distributed in the body-centered cubic phase, with a hardness about 643 HV0.5. Laser-cladding can effectively inhibit the boride precipitation and the laser-cladded alloy is mainly composed of a simple bcc solid solution, with a high hardness about 769 HV0.5, indicating the strengthening effect by interstitial boron atoms is greater than the strengthening by borides precipitation. Heat treatments between 800 degrees C and 1200 degrees C can simultaneously improve the hardness and fracture toughness of arc-melted alloys, owing to the boride spheroidization, dissolution, re-precipitation, and hence the increased boron solubility and nano-precipitation in the bcc solid solution. By contrast, the hardness of laser-cladded alloys reduce after heat treatments in the same temperature range, due to the decreased boron solubility in the matrix.

Defects involving interstitial boron in low-temperature irradiated silicon

Interstitial boron-related defects in silicon subjected to irradiation with 5 MeV electrons at a temperature of 80 K are investigated by Fourier-transform infrared absorption spectroscopy. This study demonstrates the radiation-enhanced annealing of interstitial boron during irradiation. We have revealed the interaction, which occurs in the course of irradiation, of diffusing interstitial boron atoms with one another and with interstitial oxygen. The local vibrational modes associated with these defects are identified, and the thermal stability of the defects is determined.

Unravelling the Efficient Photocatalytic Activity of Boron-induced Ti3+ Species in the Surface Layer of TiO2

Ti3+ species are highly unstable in air owing to their facile oxidation into Ti4+ species, and thus they cannot concentrate in the surface layer of TiO2 but are mainly present in its bulk. We report generation of abundant and stable Ti3+ species in the surface layer of TiO2 by boron doping for efficient utilization of solar irradiation. The resultant photocatalysts (denoted as B-TiO2−x) exhibit extremely high and stable solar-driven photocatalytic activity toward hydrogen production. The origin of the solar-light activity enhancement in the B-TiO2−x photocatalysts has been thoroughly investigated by various experimental techniques and density functional theory (DFT) calculations. The unique structure invoked by presence of sufficient interstitial boron atoms can lead to substantial variations in density of states of B-TiO2−x, which not only significantly narrow the band gap of TiO2 to improve its visible-light absorption, but also promote the photogenerated electron mobility to enhance its solar-light photocatalytic activity.

Local vibrational modes of interstitial boron–interstitial oxygen complex in silicon

In the present work, we report local vibrational mode (LVM) related absorption lines which are assigned to the complex incorporating interstitial boron and interstitial oxygen atoms (BiOi), a possible precursor of the center responsible for light‐induced degradation (LID) in solar cells produced from boron‐doped oxygen‐rich silicon. Fourier transform infrared absorption (IR) spectroscopy was used for detection and analysis of absorption lines due to defects which were created in boron‐doped Czochralski‐grown Si samples by irradiation with 6 or 10 MeV electrons at room temperature. Changes in the IR absorption spectra upon isochronal annealing of the irradiated samples in the temperature range 75–225 °C have also been monitored. A set of previously unreported LVM lines with the same formation and elimination behavior has been studied. The most intense lines of the set are found to be at 991, 721, and 550 cm−1. On the basis of an analysis of changes in intensity of the lines with the concentrations of impurities in the silicon and on the similarity of their annealing features with those for the DLTS signal due to the BiOi center, it is argued that the lines are related to the LVMs of this defect. The positions of the lines have been compared with the previously reported LVMs derived from ab initio modeling calculations for different configurations of the BiOi complex. A configuration having calculated LVMs close to those determined experimentally has been found and the origins of the modes are discussed.

Doping TiO2 with boron or/and cerium elements: Effects on photocatalytic antimicrobial activity

The aim of this study is to study the effect of ions co-doped on the photocatalytic antimicrobial activities of TiO2 nano-materials under illumination with visible light. Pure TiO2, boron or cerium single doped TiO2, boron and cerium co-doped TiO2 nano-materials were synthesized by a sol–gel method calcinated at 600 °C and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–Vis absorption spectra (DRS) and Photoluminescence spectra (PL). The photocatalytic antimicrobial activities of nano-materials were determined by killing rate of Staphylococcus aureus. The results show TiO2, B or/and Ce doped TiO2 nano-materials are anatase phase as the main crystalline phase. TiO2 doped with ions exhibit small crystal size and high specific surface area. B and Ce co-doping decreases the band gap of the TiO2 and effectively inhibits electrons and holes recombination. The present forms of boron ions are a substitution B occupying O sites, interstitial boron atoms and BOB bonds in [BO3]; Ce3+ and Ce4+ co-exist in the materials. The antimicrobial results show killing rate of B and Ce co-doping TiO2 is superior to the other materials, and B and Ce co-doped has a synergistic antimicrobial effect.

Radiation-induced bistable centers with deep levels in silicon n +–p structures

The method of deep level transient spectroscopy is used to study electrically active defects in p-type silicon crystals irradiated with MeV electrons and α particles. A new radiation-induced defect with the properties of bistable centers is determined and studied. After keeping the irradiated samples at room temperature for a long time or after their short-time annealing at T ∼ 370 K, this defect does not display any electrical activity in p-type silicon. However, as a result of the subsequent injection of minority charge carriers, this center transforms into the metastable configuration with deep levels located at EV + 0.45 and EV + 0.54 eV. The reverse transition to the main configuration occurs in the temperature range of 50–100°C and is characterized by the activation energy ∼1.25 eV and a frequency factor of ∼5 × 1015 s–1. The determined defect is thermally stable at temperatures as high as T ∼ 450 K. It is assumed that this defect can either be a complex of an intrinsic interstitial silicon atom with an interstitial carbon atom or a complex consisting of an intrinsic interstitial silicon atom with an interstitial boron atom.

The nature of boron‐oxygen lifetime‐degrading centres in silicon

AbstractLight‐induced degradation of minority carrier lifetime in silicon is caused by the formation of two B‐O recombination centres: fast‐stage centres (FRC) and slow‐stage centres (SRC). FRC were concluded to emerge by a carrier‐assisted reconfiguration of a latent BO2 defect composed of a substitutional boron atom and an oxygen dimer. The nature of SRC however remained uncertain; this defect appeared to involve an interstitial boron atom rather than a substitutional one. More recent data on SRC in boron‐containing compensated p‐Si and n‐Si now show that the SRC actually emerge in the same way as FRC: by a reconfiguration of BO2, but from a different latent form. The two latent BO2 defects (the precursors for FRC and for SRC) are created during a cooling stage after the last high‐temperature anneal, and their concentration, proportional to the boron concentration and squared oxygen concentration, depends on the cooling rate. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)