Boron-doped Samples Research Articles

Boron-doped TiO2 nanoparticles for improved photoelectrochemical response via enhanced surface area and visible light absorption

The present study introduces boron doping into TiO2 nanoparticles to synthesize boron-doped TiO2 samples. The structural and morphological properties of the pristine and doped samples are investigated using X-ray diffraction, Raman spectroscopy, Field Emission Scanning Electron Microscopy (FESEM) and High Resolution Transmission Electron Microscopy (HRTEM) techniques. Photoelectrochemical measurements have confirmed that a 3 wt % concentration of boron doped TiO2 nanoparticles shows improved photoelectrochemical response compared to pristine TiO2 nanoparticles. An ∼285-fold improvement (∼0.97 mA/cm2 at 0.81 V vs RHE) is observed in 3 wt % boron doped TiO2 nanoparticles array as compared to the pristine (3.4 μA/cm2 at 0.81 V vs RHE) photoanode samples. Moreover, the enhanced surface area, suppressed recombination, effective charge separation/transport of photogenerated charge carriers, and improved visible light absorption due to boron doping result in a remarkably high current density.

Performance improvement strategies of boron-doped lithium-rich layered oxide cathode materials for wide temperature condition

Herein, the boron-doped Li-rich materials are prepared by rapid nucleation-assisted solvothermal and high-temperature method. In this work, the effects of boron doping on crystal structure and cycling performances of as-prepared materials were investigated. The material characterization results show that the introduction of B reduces the TM valence, enlarges the (003) space distance, and modulates the local crystal structure, which may change the electrochemical performance of as-prepared samples. Li1.2Ni0.24Co0.08Mn0.48B0.02O2 (LLNCMBO-2) showed an increase in discharge capacity of 36.5 mAh g−1 at 0.1 C compared to the pristine sample. The LLNCMBO-2 exhibit high capacity retention of 85.50 % after 200 cycles with a voltage decay of only 254.9 mV. Additionally, the results of wide temperature testing show that the electrochemical performance of boron-doped samples improved evidently.

A novel boron-doping approach for long-term cycling life of Li-rich layered cathode

The commercial application of Li-rich Mn-based layered oxides (LLOs) is hindered due to their instability of lattice oxygen and dissolution of manganese. Herein, an effective and large-scale production co-precipitation boron-doping strategy was proposed to improve the performance of Li1.15Mn0.53Ni0.22Co0.1O2. We found that the boron introduced in the co-precipitation process will be uniformly distributed in the bulk and the resulting boron-doped Li1.15Mn0.53Ni0.22Co0.1O2 shows excellent electrochemical properties with low doping amount. Multi-dimensional analysis shows that boron doping significantly improves the structural stability of materials. After 1200 cycles at 1C, boron-doped sample can deliver 147 mAhg−1 with an excellent retention of 80.1%, which is much higher than that of the pristine sample of 44% after 700 cycles. Moreover, the discharge voltage decay of the boron-doped samples is only 0.54 mV per cycle (1.39 mV for pristine). It is worth mentioning that the pouch-cell full battery cycle performance of doped samples is also excellent. The doped cathode//graphite shows a superior capacity retention of 83.6% after 500 cycles without gas generation, while the pristine//graphite only hold the 46.6% of initial capacity. The dQ/dV curves and the SEM/EDS of electrode analysis verified higher reversibility of lattice oxygen, less manganese dissolution and more stable microstructure, which greatly improved the cycling life after boron doping.

Investigating the grain boundary features of lithium titanium phosphate as an electrolyte for all-solid-state lithium-ion batteries and their optimization by boron doping

This work reports a detailed analysis of the grain boundary electrochemical properties of lithium titanium phosphate for application in all-solid-state lithium-ion batteries and their improvement by boron addition, Li1+xTi2−xBx(PO4)3 (x = 0, 0.2). The results demonstrate that highly resistive grain boundaries exist in the undoped material, which preclude its ability to attain a high overall Li-ion conductivity. Conversely, boron addition provides a significant improvement of both bulk and grain boundary conductivities, resulting from the Li-enrichment associated with charge compensation for the boron doping. A detailed analysis using the brick layer model and a space charge analysis reveals a lower depletion of Li+ species at the space charge layers of the grain boundaries of the boron-doped sample, which allow a higher intrinsic grain boundary conductivity to be offered by this material. This factor permits a much higher overall conductivity to be attained in the boron-containing sample, despite a finer microstructure. Overall, this work provides new insights regarding the electrochemical nature of the grain boundary of NASICON-based solid-state Li-electrolytes, underscoring the effectiveness of composition-driven grain boundary engineering for performance improvement; a factor that is currently understudied for this category of material.

Enhancing mechanical properties of ultrafine-grained tungsten for fusion applications

Tungsten, while showing many favorable properties, faces challenges in high-performance applications due to its brittle nature. One strategy to improve strength and toughness in tungsten is to refine the grain size down to the ultra-fine grained (ufg) regime. However, as the grain size is reduced, the fraction of grain boundaries that provide easy paths for crack growth increases, thereby limiting the gain in ductility. Therefore, strengthening the grain boundaries is of great importance if one wants to tap the full potential of this material. Using ab-initio calculations, potential grain boundary cohesion enhancing doping elements were identified, and doped ultra-fine grained tungsten samples were fabricated from powders and characterized extensively using small-scale testing techniques. We found that additions of boron and hafnium improve the mechanical properties of tungsten remarkably. Furthermore, an additional low-temperature heat treatment of the boron-doped sample promotes grain boundary segregation, enhancing the properties even further. Thus, in this work we provide an effective pathway of improving mechanical properties in ultra-fine grained tungsten using grain boundary segregation engineering. This opens the door for many challenging applications of ufg W in harsh environments. To further underline the potential employment of ufg W in nuclear fusion reactors, a favorable swelling behavior and mechanical property response after irradiation with helium is presented within this work.

Influence of highly doped layers on hydrogen in-diffusion into crystalline silicon

In this work, the influence of highly doped layers on the hydrogen in-diffusion into silicon from hydrogen-rich silicon nitride is investigated. Hydrogen in the crystalline silicon bulk of wafers with and without highly doped layers present was examined in solar cell-like structures by resistivity measurements for quantification of BH-pair dynamics. Hydrogen diffusion through phosphorus- and boron-doped Float-Zone samples without highly doped layers and with p + - respectively n + -layers was determined via secondary ion mass spectrometry. Therefore, deuterium concentration in an amorphous silicon layer on the backside was measured. This experiment shows an up to threefold increase of deuterium concentration in the amorphous layer for samples with highly doped layers present. A possible explanation of this observation is given by simulations. • Influence of highly doped layers on H in-diffusion. • BH-pair dynamics in samples with and without highly doped layers. • SIMS data of D diffusing through highly doped layers and bulk c-Si. • Simulations of H-species in samples with n + -p-n + structure after firing.

Effect of graphene-based additives on mechanical strength and microstructure of gypsum plaster

In this study, graphene-based materials such as graphene oxide, reduced graphene oxide, and boron-doped reduced graphene oxide were synthesized, and their effects on the microstructure and mechanical properties of gypsum plaster were investigated. The graphene oxide (GO) sample was synthesized by modified Hummers’ method, and reduced graphene oxide (rGO) was obtained with the thermal reduction of GO. Boron doped reduced graphene oxide (B-rGO) was prepared via the impregnation method. The synthesized graphene-based materials were characterized using H 2 -TPR, TGA-DTA, XRD, FT-IR, SEM-EDS, TEM, Raman, and N 2 adsorption-desorption analysis. Analysis results confirmed that 450 o C was a sufficient temperature under an H 2 atmosphere to reduce GO and preserve rGO structure. XRD results revealed the presence of multilayer graphene structure in the rGO and B 2 O 3 crystals in the B-rGO sample. Multilayer graphene formation was also determined from the I 2D /I G ratio (0.1) of Raman analysis. Mechanical strength studies showed that while GO had a negative effect on both bending and compressive strength of gypsum plaster, rGO enhanced its bending and compressive strength. The addition of 0.1 wt% rGO added gypsum plaster increased the bending strength by 15.1% and compressive strength by 3.70%. SEM, He Pycnometry, and N 2 adsorption-desorption analyses revealed that rGO addition significantly changed the microstructure of gypsum plaster. The addition of B-rGO positively affected the compressive strength of the plaster and the highest increase was obtained as 8.6%; however, no significant change was observed in the microstructure of gypsum. • Electron microscopy images represented graphene nanosheets and graphene layers • X-ray diffraction results revealed the B 2 O 3 crystals in the boron-doped sample • Reduced graphene oxide increased the bending and compressive strength • Boron doped reduced graphene oxide enhanced the compressive strength • Reduced graphene oxide decreased the porosity of the gypsum

Enhancing energy efficiency and long-term durability of vanadium redox flow battery with catalytically graphitized carbon fiber felts as electrodes by boron doping

A boron doping on a commercial carbon fiber felt (CFF) is used to assemble a high-performance vanadium redox flow battery (VRFB). The CFF is immersed in the boric acid solution and subjected to a heat-treatment up to 2700 °C. The crystallinity of the boron-doped samples increases more than threefold when compared to only heat-treated CFF, indicating that boron induces CFF to highly graphitized CFF. As a result, electrochemical impedance spectroscopy and cyclic voltammetry reveal that boron-doped CFFs increase electrical conductivities. In addition, when the boron-doped CFFs are applied to VRFB electrodes, their electrochemical performances are improved compared to CFF and only heat-treated CFF. The CFFB5 that is a sample containing 0.6 at.% of boron contents exhibits the best electrochemical performance in the single-cell test compared to the other samples. In particular, the CFFB5 sample provides excellent energy efficiency (90% at 50 mA cm–2) and long-term durability (98.1% over 150 cycles). Consequently, our approach introduces effective modulation of commercially available CFF with a significant graphitization via a feasible boron doping method and we conclude that the resulting boron-doped CFF induces improved electrochemical performance for VRFB applications when the appropriate amount of a doping agent is provided.

Insights into the Adsorption and Photocatalytic Oxidation Behaviors of Boron-Doped TiO2/g-C3N4 Nanocomposites toward As(III) in Aqueous Solution

The coupled adsorption–photocatalytic oxidation process provides a great potential scenario to enhance the removal efficiency of arsenite contaminants by converting As(III) to As(V) and simultaneous adsorption. In this study, the boron-doped black TiO2/g-C3N4 nanocomposite is synthesized by combination of sol–gel and in situ decomposition-thermal polymerization methods as a photocatalyst for the photocatalytic oxidation and adsorption of As(III). Under dark conditions, the boron-doped samples (B-TiO2 and B-TiO2/g-C3N4) display an increase in the As(III) adsorption capacity by one order of magnitude up to circa 3.2 mg g–1 with an initial As(III) concentration of 2 mg L–1 at 298.15 K and pH 5. The adsorption kinetics of As(III) on B-TiO2/g-C3N4 conform to the pseudo-second-order kinetic model, revealing the chemical adsorption mechanism. Under visible light irradiation, the total arsenic removal capacity is substantially improved by 20% with a removal capacity of 3.9 mg g–1. The enhancement of arsenic adsorption is attributed to the chemical complexation and hydrogen bond, in which B–OH bonds play a dominant role. The photocatalytic oxidation mechanism of the as-synthesized B-TiO2/g-C3N4 is attributed to the synergism of superoxide radicals, hydroxyl radicals, and photogenerated holes.

The Cerium/Boron Insertion Impact in Anatase Nano-Structures on the Photo-Electrochemical and Photocatalytic Response

Boron- and cerium-doped titania (Anatase) were prepared via sol-gel method. Phase composition and morphology were assessed by X-ray diffraction (XRD), scanning electronic microscopy (SEM), BET, diffuse reflectance spectra (DRS), and XPS. Photo-electrochemistry of these materials, deposited onto fluorine-doped SnO2 (FTO), was investigated in acid and acid-containing methanol. The boron-doped sample showed the best opto-electronic properties among the investigated samples. On the other hand, the cerium-doped titania samples annihilate to a certain extent the titania surface states, however, photogenerated charge separation was limited, and certainly associated to surface Ce3+/Ce4+ species. The substitutional effect of boron ions for O sites and interstitial sites was confirmed by XRD and XPS analyses.

A cost-efficient approach for simultaneous scanning electrochemical microscopy and scanning ion conductance microscopy

A novel and cost-efficient probe fabrication method yielding probes for performing simultaneous scanning electrochemical microscopy (SECM) and scanning ion conductance microscopy (SICM) is presented. Coupling both techniques allows distinguishing topographical and electrochemical activity information obtained by SECM. Probes were prepared by deposition of photoresist onto platinum-coated, pulled fused silica capillaries, which resulted in a pipette probe with an integrated ring ultramicroelectrode. The fabricated probes were characterized by means of cyclic voltammetry and scanning electron microscopy. The applicability of probes was demonstrated by measuring and distinguishing topography and electrochemical activity of a model substrate. In addition, porous boron-doped diamond samples were investigated via simultaneously performed SECM and SICM.Graphic abstract

Dry Sliding Wear Behavior of Boron-Doped 205 Manganese Steels

In the present study, the wear properties of 205 manganese steels produced by a casting process with different boron contents (0.0023-0.0182 wt.%) were investigated, using a pin-on-disc tribometer under dry sliding conditions. The friction coefficient of 205 manganese steel by boron addition (at 0.0076 wt.%) reduced from 0.28 to 0.18. The addition of boron to 205 manganese steel led to a decrease in the friction coefficient due to the lubricating effect of boron. X-ray diffraction showed that the boron addition to 205 manganese steel increased lattice parameters of the samples. The wear test results at 5 and 10 N loads showed that the wear amount of 205 manganese steels decreased with boron addition. Thus, the wear results showed that the wear resistance of 205 manganese steel is increased with the addition of small amounts of boron. Furthermore, scanning electron microscopy images indicated that the characteristic wear mechanisms for the boron-doped samples on the worn surfaces were abrasive, and it was plastic deformation, mild abrasive, and adhesive wear mechanism in the undoped 205 manganese steel.

Room-temperature ferromagnetism in boron-doped oxides: a combined first-principle and experimental study

ABSTRACTThe ferromagnetic properties of boron-doped oxides, namely ZnO, MgO, CdO and TiO2 have been studied using first-principle calculations based on density functional theory. A boron atom, when doped at an anion site, generates a magnetic moment per dopant atom ranging from ∼1 µB in TiO2 to ∼3 µB in ZnO. The source of magnetism in the boron-doped oxides is the 2p-orbital electrons of the dopant atom plus a small contribution coming from the oxygen atoms surrounding the dopant. A spin–spin interaction study reveals that the doping of B at O sites favours ferromagnetic spin coupling in ZnO, MgO, CdO and TiO2. Boron-doped samples have been prepared by ion-beam irradiation with a 10 keV B+ beam implanting on sample pallets. Magnetic measurements have been carried out for B+-ion-implanted oxide samples using a SQUID magnetometer. A stable room-temperature ferromagnetic ordering is observed in boron-ion-irradiated ZnO, MgO, CdO and TiO2 samples.

On the crystallization behavior of sputter-deposited a-Si films on 4H-SiC

The crystallization behavior of sputter-deposited amorphous silicon (a-Si) films on 4H-SiC by post-deposition annealing (PDA) is investigated. Film thicknesses between 100 and 1500 nm were selected. PDA was carried out at temperatures between 800 and 1100 °C. In addition, the influence of the annealing time and the heating rate is evaluated. Furthermore, the impact of high boron doping and the face of the SiC substrate was determined. A low-pressure chemical vapor deposition (LPCVD) Si film was deposited on the same substrate for reasons of comparison. The crystallinity of the Si films was investigated using X-ray diffractometry and transmission electron microscopy, whereas atomic force microscopy was applied to determine the surface roughness. The amorphous phase of the as-deposited Si thin films was crystallized into a polycrystalline microstructure applying different PDA conditions. A sharp and distinct interface to the 4H-SiC substrate without the presence of structural defects, amorphous regions or any indication for alloy formation was observed. No influence of the underlying SiC to stimulate the texture in the Si grain orientation could be found. Different PDA parameters showed an influence on the average grain size and the stress inside the grains. Highly boron-doped samples exhibit mean grain size values up to several hundreds of nanometers. Although starting with a poor film quality represented by an amorphous microstructure due to sputter deposition at low substrate temperatures, polycrystalline Si layers on 4H-SiC substrates are realized exhibiting a more than twenty times lower surface roughness compared to those synthesized with LPCVD.

Dopant activation and photoresponses of boron-doped silicon by self-assembled molecular monolayers

Self-assembled molecular monolayer doping is an emerging doping technique. In this work, we investigated the activation rate and photoresponses of boron doped silicon by self-assembled molecular monolayer doping. By using low temperature Hall effect measurements and by secondary ion mass spectroscopy, we find that the activation rate of boron in these samples is in the range of 91%–54%, depending on the doping concentration. Interestingly, the photoresponsivity of the boron doped samples is also significantly higher than that of the phosphorus doped samples even though the same doping technique is used. The intriguing photoresponses are closely related to the trapping of photogenerated minority carriers by the defects in the p-type silicon.

Raman spectroscopy of silicon nanowires formed by metal-assisted chemical etching

Silicon nanowires obtained by metal-assisted chemical etching of crystalline silicon (Si) wafers are studied by Raman spectroscopy to reveal the effect of the formation time of nanowires and their additional doping with boron and phosphorus. The observed modification of the spectrum shape in the boron-doped samples due to the Fano effect made it possible to estimate the concentration of free holes in Si nanowires, which is of the order of 1019 - 1020 cm3, depending on the preparation conditions. The obtained results indicate the potential of the Raman spectroscopy for contactless diagnostics of Si nanostructures.

Boron-doped single crystal LiNi0.6Mn0.2Co0.2O2 with improved electrochemical performance for lithium-ion batteries

Single crystal boron-doped LiNi0.6Mn0.2Co0.2O2 cathode material with excellent electrochemical properties were synthesized in the study. X-ray diffraction revealed that boron doping promoted the unit cell expands along the c-direction which was conductive to improving the kinetic of lithium-ion transmission. Electrochemical tests showed that boron-doped cathode material exhibited remarkable improvement in cycling performance and rate capability compared to bare sample. After 50 cycles at 1.0 C, the boron-doped sample delivered 176.3 mAh g−1 with a retention of 96.1%, which was much higher than that of the undoped sample of 167.8 mAh g−1 with a retention of 90.7%. The highly ordered layered structure and improved structure stability during repeated intercalation/deintercalation of lithium ions were responsible for the enhanced electrochemical performance. Besides that, the unique single crystal morphology resulted in even faster lithium-ion transportation as a result of small particle size. Both the doping effects of boron and single crystal particles contributed to the excellent electrochemical performance of the doped cathode materials.

Effective Contact Formation Method on High-Sheet-Resistance Boron-Doped Emitter With Current Injection

We investigate the effect of current injection during contact formation of an Ag-based screen-printed electrode to boron-doped emitters, which differ by their sheet resistances. The average contact resistivities between the metal electrode and silicon of all the boron-doped emitter samples are ∼3 mΩ cm2, regardless of the sheet resistance (75–145 Ω/sq), and the lowest values are below 1 mΩ cm2 using the injection of a current density of 5 A/cm2 during the metallization process. Additionally, the injection of current to a phosphorus-doped emitter in the opposite direction suppressed the formation of the Ag precipitates and crystallites and increased the contact resistivity of over 300 mΩ cm2, which is comparable to that obtained when Ag paste is applied to a boron-doped emitter with no current injection. This finding indicates that electrons are essential for the reduction of Ag ions during high-temperature metallization process using the screen-printing technique and that the injection of current can control the contact formation and enhance the efficiency of solar cells. Finally, we suggest a suitable process for reducing the contact resistivity in manufacturing n-type Si solar cells.

Tuning the electronic band alignment properties of TiO2 nanotubes by boron doping

The present study highlights the significant impact of trace level doping of boron in titanium dioxide (TiO2) nanotubes by investigating the structural, optical and electronic properties of samples, TNT and B-TNT. TEM analysis of boron-doped sample confirms the formation of crystalline nanotube structures and the trace level quantification of boron was confirmed by XPS analysis, where B shows feature of Ti–O–B bonding. Raman analysis revealed that the rutile phase becomes prominent after boron doping and Raman bands shift towards higher wavenumber was observed with increase in the tube diameter. The boron incorporation in TiO2 nanotubes reduces the band gaps from 3.3 eV to 3.1 eV and the mid-gap states were created within the band gap of the B-TNT sample. The change in valance band position from 2.5 eV to 2.9 eV after boron doping significantly changed the Fermi level position in TiO2 nanotubes. The work function of pristine and boron doped TiO2 samples are observed as 4.23 eV and 4.27 eV, respectively, as measured by Kelvin probe force microscopy. Here, we have investigated the band alignment of TNT and B-TNT by using state-of-the-art material characterization surface sensitive techniques. It can also be concluded that the electron affinity of the B-TNT sample is enhanced ∼4.07 eV than that of TNT ∼ 3.43 eV. The type –II band alignment is observed to be in between TNT and B-TNT with a valence band offset (VBO) ∼ 0.4 eV and conduction band offset (CBO) ∼ 0.6 eV.

Enhancing Electrochemical Efficiency of Hydroxyl Radical Formation on Diamond Electrodes by Functionalization with Hydrophobic Monolayers.

Electrochemical formation of high-energy species such as hydroxyl radicals in aqueous media is inefficient because oxidation of H2O to form O2 is a more thermodynamically favorable reaction. Boron-doped diamond (BDD) is widely used as an electrode material for generating •OH radicals because it has a very large kinetic overpotential for O2 production, thus increasing electrochemical efficiency for •OH production. Yet, the underlying mechanisms of O2 and •OH production at diamond electrodes are not well understood. We demonstrate that boron-doped diamond surfaces functionalized with hydrophobic, polyfluorinated molecular ligands (PF-BDD) have significantly higher electrochemical efficiency for •OH production compared with hydrogen-terminated (H-BDD), oxidized (O-BDD), or poly(ethylene ether)-functionalized (E-BDD) boron-doped diamond samples. Our measurements show that •OH production is nearly independent of surface functionalization and pH (pH = 7.4 vs 9.2), indicating that •OH is produced by oxidation of H2O in an outer-sphere electron-transfer process. In contrast, the total electrochemical current, which primarily produces O2, differs strongly between samples with different surface functionalizations, indicating an inner-sphere electron-transfer process. X-ray photoelectron spectroscopy measurements show that although both H-BDD and PF-BDD electrodes are oxidized over time, PF-BDD showed longer stability (≈24 h of use) than H-BDD. This work demonstrates that increasing surface hydrophobicity using perfluorinated ligands selectively inhibits inner-sphere oxidation to O2 and therefore provides a pathway to increased efficiency for formation of •OH via an outer-sphere process. The use of hydrophobic electrodes may be a general approach to increasing selectivity toward outer-sphere electron-transfer processes in aqueous media.