Interstitial Boron Research Articles

An Interstitial Boron Inserted Metastable Hexagonal Rh Nanocrystal for Efficient Hydrogen Oxidation Electrocatalysis

AbstractConstructing metastable phase structure plays an important role in changing the physicochemical properties and improving the catalytic performance of nanocrystals. Unfortunately, the synthesis of metastable phase metallic nanocrystals is highly challenging, mainly due to the thermodynamically unstable ground‐state. Here, we report a synthesis of unconventional metastable hexagonal rhodium nanocrystal (Bint−Rhhcp/C) via interstitial boron insertion. The insertion of boron atoms into the interstitial sites of cubic Rh lattice not only induces the atomic arrangements from face‐centered cubic (fcc) to hexagonal close‐packed (hcp), but also stabilizes the metastable hexagonal Rh structure. Benefiting from the phase transition and interstitial boron doping, the Bint−Rhhcp/C catalyst exhibits remarkable catalytic performance toward hydrogen oxidation reaction (HOR) under alkaline media, with a mass activity of 1.413 mA μgPGM−1. Experimental measurements including in situ surface‐enhanced infrared absorption spectroscopy (SEIRAS) and density functional theory (DFT) calculations indicate that the strengthened adsorption of hydroxyl species on the electrode surface of Bint−Rhhcp/C is responsible for the reconstruction of interfacial water structure and increased water proportions in the gap region in the electric double layers. As a result, the increased water connectivity and hydrogen bond network facilitate high‐efficiency hydrogen transfer across the interface, thereby boost the alkaline HOR performance.

Dose-Dependent Performance of Boron-Implanted Self-Aligned Bottom-Gate IGZO TFTs

This work provides an interpretation of donor activation in self-aligned bottom-gate (SA-BG) Indium-Gallium-Zinc Oxide (IGZO) TFTs with ion-implantation of boron (11B+) species as the source/drain treatment. The effect of implant dose on device operation was investigated. Transfer characteristics appeared similar with a boron dose of 1 and 2×1015 cm-2 however, a 45% decrease in max current was observed for devices implanted with a 4×1015 cm-2 dose. Van der Pauw measurements displayed a similar trend; an increase in boron dose resulted in an increase in sheet resistance. A left-shift in transfer characteristics was observed with a greater shift in the 4×1015 cm-2 dose devices, following thermal stability treatments. The existence of two separate boron species is hypothesized, (1) an electrically active donor species involving a relatively small fraction of the total boron concentration and (2) additional boron interstitials and/or other associated defects. A detailed discussion on developed arguments arrived at through analysis of TFT electrical characteristics is presented.

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.

Change in Growth Mode of BGaN Layers Grown on GaN

A change in the growth mode from Stranski–Krastanov one, which is characteristic of MOCVD grown GaN, to the laterally grown BGaN in the Volmer–Weber growth mode is described. This change in growth is evidenced by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of BGaN grown on GaN at high temperatures. It is postulated on the basis of SIMS and XRD results that this change in growth is initiated by the transfer of boron atoms from gallium substitutional to interstitial. The proposed mechanism for the observed growth change is related to the generation of nitrogen interstitials and subsequent reactions with boron interstitials, which result in the formation of a BN layer at the growth front. The observed large change in the growth mode is due to a lattice mismatch between the grown BGaN and the atomic layer of BN and stays behind the change to the Volmer–Weber growth mode. The consequence of the Volmer–Weber growth mode is the textural layer of BGaN. The textural character of this material is associated with large voids between grown BGaN “plates”. These large voids are responsible for the termination of threading dislocations propagating in the c-direction. It is also postulated that the blocked threading dislocations from the GaN underlayer and laterally grown BGaN layers along the a-directions are responsible for the decrease in defect concentration within these layers.

Interstitial Boron-Modulated Porous Pd Nanotubes for Ammonia Electrosynthesis.

Electrochemical conversion of nitrogen into ammonia at ambient conditions as a sustainable approach has gained significant attention, but it is still extremely challenging to simultaneously obtain a high faradaic efficiency (FE) and NH3 yield. In this work, the interstitial boron-doped porous Pd nanotubes (B-Pd PNTs) are constructed by combining the self-template reduction method with boron doping. Benefiting from distinctive one-dimensional porous nanotube architectonics and the incorporation of the interstitial B atoms, the resulting B-Pd PNTs exhibit high NH3 yield (18.36 μg h-1 mgcat.-1) and FE (21.95%) in neutral conditions, outperforming the Pd/PdO PNTs (10.4 μg h-1 mgcat.-1 and 8.47%). The present study provides an attractive method to enhance the efficiency of the electroreduction of nitrogen into ammonia by incorporating interstitial boron into porous Pd-based catalysts.

A Highly-Efficient Boron Interstitially Inserted Ru Anode Catalyst for Anion Exchange Membrane Fuel Cells.

Developing high-performance electrocatalysts for alkaline hydrogen oxidation reaction (HOR) is crucial for the commercialization of anion exchange membrane fuel cells (AEMFCs). Here, boron interstitially inserted ruthenium (B-Ru/C) is synthesized and used as an anode catalyst for AEMFC, achieving a peak power density of 1.37W cm-2 , close to the state-of-the-art commercial PtRu catalyst. Unexpectedly, instead of the monotonous decline of HOR kinetics with pH as generally believed, an inflection point behavior in the pH-dependent HOR kinetics on B-Ru/C is observed, showing an anomalous behavior that the HOR activity under alkaline electrolyte surpasses acidic electrolyte. Experimental results and density functional theory calculations reveal that the upshifted d-band center of Ru after the intervention of interstitial boron can lead to enhanced adsorption ability of OH and H2 O, which together with the reduced energy barrier of water formation, contributes to the outstanding alkaline HOR performance with a mass activity of 1.716mA µgPGM -1 , which is 13.4-fold and 5.2-fold higher than that of Ru/C and commercial Pt/C, respectively.

Interstitial boron-doped Ni4Mo nanoarray catalyst boosts stable hydrogen evolution reaction

Designing a strategy to make the intrinsic activity of NiMo-based catalysts while being able to achieve long-term stable hydrogen production at ampere-level current densities is important for their development in AEM electrolyzers. Herein, interstitial boron atom-doped Ni4Mo is designed to obtain the catalyst with excellent alkaline HER properties. B4.7-Ni4Mo/NF exhibits a small overpotential of 135.2 mV at 1000 mA cm−2 and a high turnover frequency (TOF) value of 6.14 s−1 at 100 mV in alkaline HER, which very close to that of Pt/C (6.86 s−1). The catalyst requires only 1.73 V to achieve a current density of 1.0 A cm−2 in AEM electrolyzer at 60 °C and is stable for 800 h. Experimental and theoretical calculations reveal that interstitial boron doping not only optimizes the electronic structure to optimize H* adsorption and promote the water dissociation but also inhibits the dissolution of Mo by forming boron-metal bond.

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.

Investigation and passivation of boron and hydrogen impurities in tetragonal ZrO2 dielectrics for dynamic random access memory capacitors

Tetragonal ZrO2 high-k material as the dielectric layer of dynamic random access memory (DRAM) capacitors faces bulk defect related leakage current, which is one of the main obstacles to the down-scaling of DRAM devices. Boron and hydrogen impurities are known to be responsible for leakage current degradation and are hard to be removed in DRAM capacitors. However, the defect origins of boron and hydrogen leakage current are still puzzling, and corresponding suppression methods are urged. In this work, the properties of boron and hydrogen impurities in tetragonal ZrO2 are investigated using first-principles calculations, and defect types such as boron and hydrogen interstitials are discovered to have detrimental defect levels related to leakage current. Based on the discovery, a chlorine co-doping approach that can passivate detrimental defects by forming defect complexes is further proposed. By introducing level repulsion due to coupling between defect states, defect levels of passivated defect complexes are moved out of the region of leakage current contribution. Thus, bulk defect related leakage current in tetragonal ZrO2 based DRAM capacitors can be effectively suppressed without device structure modification, and a broad vista is opened for next-generation DRAM devices.

Red anatase TiO2 microspheres with exposed major {0 0 1} facets and boron-stabilized hydrogen-occupied oxygen vacancies for visible-light-responsive water oxidation

In pursuit of efficient solar energy to chemical energy conversion through band engineering of wide-bandgap photocatalysts such as TiO2, a compromise occurs between a narrow bandgap and high-redox-capacity photo-induced charge carriers, which impairs the potential advantages associated with the widened absorption range. The key to this compromise is an integrative modifier that can simultaneously modulate both the bandgap and band edge positions. Herein, we theoretically and experimentally demonstrate that oxygen vacancies occupied by boron-stabilized hydrogen pairs (OVBH) serve as an integrative band modifier. Compared to hydrogen-occupied oxygen vacancies (OVH), which require the aggregation of nanosized anatase TiO2 particles, oxygen vacancies coupled with boron (OVBH) can be easily introduced into large and highly crystalline TiO2 particles, as shown by density functional theory (DFT) calculations. The coupling with interstitial boron facilitates the introduction of paired hydrogen atoms. The red-colored {001} faceted anatase TiO2 microspheres with OVBH benefit from the narrowed bandgap of 1.84 eV and the down-shifted band position. These microspheres not only absorb long-wavelength visible light up to 674 nm but also enhance visible-light-driven photocatalytic oxygen evolution.

Designing interstitial boron‐doped tunnel‐type vanadium dioxide cathode for enhancing zinc ion storage capability

AbstractChemical doping is a powerful method to intrinsically tailor the electrochemical properties of electrode materials. Here, an interstitial boron‐doped tunnel‐type VO2(B) is constructed via a facile hydrothermal method. Various analysis techniques demonstrate that boron resides in the interstitial site of VO2(B) and such interstitial doping can boost the zinc storage kinetics and structural stability of VO2(B) cathode during cycling. Interestingly, we found that the boron doping level has a saturation limit peculiarity as proved by the quantitative analysis. Notably, the 2 at.% boron‐doped VO2(B) shows enhanced zinc ion storage performance with a high storage capacity of 281.7 mAh g−1 at 0.1 A g−1, excellent rate performance of 142.2 mAh g−1 at 20 A g−1, and long cycle stability up to 1000 cycles with the capacity retention of 133.3 mAh g−1 at 5 A g−1. Additionally, the successful preparation of the boron‐doped tunnel‐type α‐MnO2 further indicates that the interstitial boron doping approach is a general strategy, which supplies a new chance to design other types of functional electrode materials for multivalence batteries.

Study of electron paramagnetic resonance as a tool to discriminate between boron related defects in barium disilicide

Barium disilicide (BaSi2), composed of Earth-abundant and nontoxic elements, is a promising material for thin-film solar cells. The control of carrier type and carrier concentration by impurity doping is particularly important for the application of BaSi2 to solar cells. However, the presence of defects in semiconductors such as BaSi2 may have a significant impact on the electrical and optical properties of solar cells. In this study, we chose boron to act as a p-type impurity in BaSi2 and studied boron-related defects using the Quantum Espresso method with density functional theory. The formation energy of interstitial boron defects was found to be lower than that of boron in Si vacancy sites. The hyperfine coupling constants of 137Ba with antisite boron defects (BSi) are very localized and differ significantly from those of 137Ba with interstitial boron defects (Bi). This suggests that neutral BSi and Bi can be identified by electron paramagnetic resonance.

Ultrafine oxygenophilic nanoalloys induced by multifunctional interstitial boron for methanol oxidation reaction

Interface construction is one of the most feasible approaches to optimize the physical and chemical properties of noble metal-based catalysts and consequently improve their catalytic performance. Herein, the design of effective reaction interfaces by bimetallic, trimetallic or polymetallic alloying has been extensively explored. In this research, metalloid boron (B) was alloyed within palladium-iridium (Pd-Ir) nanoalloy supported on nitrogen-doped graphene (NG) to promote the methanol oxidation reaction (MOR) in alkaline media. Being benefited from this, the optimum Pd7IrBx/NG catalyst exhibited enhanced EOR activity mass activity (1141.7 mA mg−1) and long-term stability (58.2 % current density retention rate after 500 cycles of cyclic voltammetry). The mechanism was further studied by electrochemical experiments and characterization, which highlighted that the multifunctional effect of electronic effect and strain effect and kinetic optimization induced by boron doping played a very positive role on MOR.

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.

Forging strength–ductility unity in a high entropy steel

Fe72.4Co13.9Cr10.4Mn2.7B0.34 high entropy steel was prepared by magnetron sputtering. The alloy exhibits a high yield strength of 2.92 ± 0.36 GPa while achieving appreciable plasticity of 13.7 ± 1.9% at the ultimate compressive strength (3.37 ± 0.36 GPa). The distribution of iron and chromium shows an unusual, characteristic spinodal-like pattern at the nanometer scale, where compositions of Fe and Cr show strong anticorrelation and vary by as much as 20 at.%. The high strength is largely attributable to the compositional modulations, combined with fine grains with body-centered cubic (BCC) crystal structure, as well as grain boundary segregation of interstitial boron. The impressive plasticity is accommodated by the formation and operation of multiplanar, multicharacter dislocation slips, mediated by coherent interfaces, and controlled by shear bandings. The excellent strength–ductility combination is thus enabled by a range of distinctive strengthening mechanisms, rendering the new alloy a potential candidate for safety-critical, load-bearing structural applications.

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).

Strained Zero‐Valent Iron for Highly Efficient Heavy Metal Removal

AbstractMicroscale zero‐valent iron is one of the most important multifunctional environmental remediation materials, yet its passivated iron oxide shell hampers the transportation of inherent electrons. Herein, the authors exert tensile strain onto mZVI by interstitial boron doping that destabilizes lattice FeFe interactions, thereby liberating the electrons trapped in the iron reservoir. Tensile strain also upshifts the equilibrated Fermi level at the iron/iron oxide Ohmic heterojunction, thus populating the oxide shell with abundant electrons for robust heavy metal sequestration. Strained‐mZVI exhibits a 62 times faster Cr(VI) removal rate than its unstrained counterpart and can successfully treat industrial wastewater such as landfill leachate, electroplating, and chromium effluents. The excellent property and exceedingly low cost ($2000 ton−1) of strained‐mZVI results in its great potential to remediate heavy metal‐contaminated water and soil.

5.5 MeV Electron Irradiation-Induced Transformation of Minority Carrier Traps in p-Type Si and Si1−xGex Alloys

Minority carrier traps play an important role in the performance and radiation hardness of the radiation detectors operating in a harsh environment of particle accelerators, such as the up-graded sensors of the high-luminosity hadron collider (HL-HC) at CERN. It is anticipated that the sensors of the upgraded strip tracker will be based on the p-type silicon doped with boron. In this work, minority carrier traps in p-type silicon (Si) and silicon–germanium (Si1−xGex) alloys induced by 5.5 MeV electron irradiation were investigated by combining various modes of deep-level transient spectroscopy (DLTS) and pulsed technique of barrier evaluation using linearly increasing voltage (BELIV). These investigations were addressed to reveal the dominant radiation defects, the dopant activity transforms under local strain, as well as reactions with interstitial impurities and mechanisms of acceptor removal in p-type silicon (Si) and silicon–germanium (SiGe) alloys, in order to ground technological ways for radiation hardening of the advanced particle detectors. The prevailing defects of interstitial boron–oxygen (BiOi) and the vacancy–oxygen (VO) complexes, as well as the vacancy clusters, were identified using the values of activation energy reported in the literature. The activation energy shift of the radiation-induced traps with content of Ge was clarified in all the examined types of Si1−xGex (with x= 0–0.05) materials.

The Boron–Oxygen (BᵢOᵢ) Defect Complex Induced by Irradiation With 23 GeV Protons in p-Type Epitaxial Silicon Diodes

In this work, the thermally stimulated current (TSC) technique has been used to investigate the properties of the radiation-induced interstitial boron and interstitial oxygen defect complex by 23-GeV (<inline-formula> <tex-math notation="LaTeX">$E_{\text {kin}}$ </tex-math></inline-formula>) protons, including activation energy, defect concentration, as well as the annealing behavior. At first isothermal annealing (at 80 &#x00B0;C for 0&#x2013;180 min) followed by isochronal annealing (for 15 min between 100 &#x00B0;C and 190 &#x00B0;C in steps of 10 &#x00B0;C), studies had been performed in order to get information about the thermal stability of the interstitial boron and interstitial oxygen defect in 50-<inline-formula> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula>cm material after irradiation with 23-GeV protons to a fluence of <inline-formula> <tex-math notation="LaTeX">$6.91\times 10^{13}\,\,{\text {p/cm}^{2}}$ </tex-math></inline-formula>. The results are presented and discussed. Furthermore, the extracted data from TSC measurements are compared with the macroscopic properties derived from current&#x2013;voltage and capacitance&#x2013;voltage characteristics. In addition, the introduction rate of interstitial boron and interstitial oxygen defect as a function of the initial doping concentration was determined by exposing diodes with different resistivities (10, 50, 250, and 2 <inline-formula> <tex-math notation="LaTeX">$\text{k}\Omega $ </tex-math></inline-formula>cm) to 23-GeV protons. These results are compared with data from TSC and deep-level transient spectroscopy measurements achieved by the team of the CERN-RD50 &#x201C;Acceptor removal project.&#x201D