Role of Curvature in Stabilizing Boron-Doped Nanocorrugated Graphene.

Boron-doped carbon nanostructures have attracted great interest recently because of their remarkable electrocatalytic performance comparable to or better than that of conventional metal catalysts. In a previous work (Carbon 123, 605 (2017)), we reported that along with significant performance improvement, B doping enhances the oxidation resistance of few-layer graphene (FLG) that provides increased structural stability for intermediate-temperature fuel-cell electrodes. In general, detailed characterization of the atomic and electronic structure transformations that occur in B-doped carbon nanostructures during fuel-cell operation is lacking. In this work, we use aberration-corrected scanning transmission electron microscopy, nanobeam electron diffraction, and electron energy-loss spectroscopy (EELS) to characterize the atomic and electronic structures of B-doped FLG before and after fuel-cell operation. These data point to the nanoscale corrugation of B-doped FLGs as the key factor responsible for increased stability and high corrosion resistance. The similarity of the 1s to π* and σ* transition features in the B K-edge EELS to those in B-doped carbon nanotubes provides an estimate for the curvature of nanocorrugation in B-FLG.

Isosterism in pyrrole via azaboroles substitution, a theoretical investigation for electronic structural, stability and aromaticity.

This work uses ab-initio CBS-QB3 and density functional theory (B3LYP) to analyze the structure, stability, and aromaticity of all isosteric nitrogen-boron pyrroles. The mono-NB unit substituted group of the isosteric NB pyrrole has four isosteres, whereas the multi-NB unit substituted group has two isosteres. These two groups make up all isosteric NB pyrrole. For structural, energetic, magnetic, and electron delocalization criteria, the results highlight the predominance of the PN3B2 isostere and its greater stability over other conformers. In addition, the global reactivity indices, ESP, HOMO-LUMO, and NBO charges have all been estimated to forecast the active side's electron donation and acceptance. These isosteres are categorized as weak electrophiles and marginal nucleophiles. NB-isosteres have poorer stability, HOMO-LUMO gap, and aromaticity than the parent (pyrrole). In general, NB compounds with more ring sharing are less aromatic than NB molecules with less ring sharing. The current study is anticipated to help in understanding of the chemistry of NB substituted molecules and their experimental identification and characterization.

Stabilized Anionic Redox by Rational Structural Design from Surface to Bulk for Long-Life Fast-Charging Li-Rich Oxide Cathodes.

On account of high capacity and high voltage resulting from anionic redox, Li-rich layered oxides (LLOs) have become the most promising cathode candidate for the next-generation high-energy-density lithium-ion batteries (LIBs). Unfortunately, the participation of oxygen anion in charge compensation causes lattice oxygen evolution and accompanying structural degradation, voltage decay, capacity attenuation, low initial columbic efficiency, poor kinetics, and other problems. To resolve these challenges, a rational structural design strategy from surface to bulk by a facile pretreatment method for LLOs is provided to stabilize oxygen redox. On the surface, an integrated structure is constructed to suppress oxygen release, electrolyte attack, and consequent transition metals dissolution, accelerate lithium ions transport on the cathode-electrolyte interface, and alleviate the undesired phase transformation. While in the bulk, B doping into Li and Mn layer tetrahedron is introduced to increase the formation energy of O vacancy and decrease the lithium ions immigration barrier energy, bringing about the high stability of surrounding lattice oxygen and outstanding ions transport ability. Benefiting from the specific structure, the designed material with the enhanced structural integrity and stabilized anionic redox performs an excellent electrochemical performance and fast-charging property..

B-doping mediated formation of oxygen vacancies in Bi2Sn2O7 quantum dots with a unique electronic structure for efficient and stable photoelectrocatalytic sulfamethazine degradation.

This study devised a straightforward one-step approach that enabled simultaneous boron (B) doping and oxygen vacancies (OVs) production on Bi2Sn2O7 (BSO) (B-BSO-OV) quantum dots (QDs), optimizing the electrical structure of the photoelectrodes. Under light-emitting diode (LED) illumination and a low potential of 1.15 V, B-BSO-OV demonstrated effective and stable photoelectrocatalytic (PEC) degradation of sulfamethazine (SMT), achieving the first-order kinetic rate constant of 0.158 min-1. The surface electronic structure, the different factors influencing the PEC degradation of SMT, and the degradation mechanism were studied. Experimental studies have shown that B-BSO-OV exhibits strong visible light trapping ability, high electron transport ability, and superior PEC performance. DFT calculations show that the presence of OVs on BSO successfully reduces the band gap, controls the electrical structure, and accelerates charge transfer. This work sheds light on the synergistic effects of the electronic structure of B-doping and OVs in heterobimetallic oxide BSO under the PEC process and offers a promising approach for the design of photoelectrodes.

Construction of Boron- and Nitrogen-Enriched Nanoporous π-Conjugated Networks Towards Enhanced Hydrogen Activation.

Boron-enriched scaffolds have demonstrated unique features and promising performance in the field of catalysis towards the activation of small gas molecules. However, there is still a lack of facile approaches capable of achieving high B doping and abundant porous channels in the targeted catalysts. Herein, construction of boron- and nitrogen-enriched nanoporous π-conjugated networks (BN-NCNs) was achieved via a facile ionothermal polymerization procedure with hexaazatriphenylenehexacarbonitrile [HAT(CN)6 ] sodium borohydride as the starting materials. The as-produced BN-NCN scaffolds were featured by high heteroatoms doping (B up to 23 wt. % and N: up to 17 wt. %) and permanent porosity (surface area up to 759 m2 g-1 mainly contributed by micropores). With the unsaturated bonded B species acting as the active Lewis acid sites and defected N species acting as the active Lewis base sites, those BN-NCNs delivered attractive catalytic performance towards H2 activation/dissociation in both gaseous and liquid phase, acting as efficient metal-free heterogeneous frustrated Lewis pairs (FLPs) catalysts in hydrogenation procedures.

Boron-Doping Induced Electron Delocalization in Fluorophosphate Cathode: Enhanced Na-Ion Diffusivity and Sodium-Ion Full Cell Performance.

Na3 V2 (PO4 )2 O2 F (NVPOF) is widely accepted as advanced cathode material for sodium-ion batteries with high application prospects ascribing to its considerable specific capacity and high working voltage. However, challenges in the full realization of its theoretical potential lie in the novel structural design to accelerate its Na+ diffusivity. Herein, considering the important role of polyanion groups in constituting Na+ diffusion tunnels, boron (B) is doped at the P-site to obtain Na3 V2 (P2- x Bx O8 )O2 F (NVP2- x Bx OF). As evidenced by density functional theory modeling, B-doping induces a dramatic decrease in the bandgap. Delocalization of electrons on the O anions in BO4 tetrahedra is observed in NVP2- x Bx OF, which dramatically lowers the electrostatic resistance experienced by Na+ . As a result, the Na+ diffusivity in the NVP2- x Bx OF cathode has accelerated up to 11 times higher, which secures a high rate property (67.2 mAh g-1 at 60 C) and long cycle stability (95.9% capacity retention at 108.6 mAh g-1 at 10 C after 1000 cycles). The assembled NVP1.90 B0.10 OF//Se-C full cell demonstrates exceptional power/energy density (213.3 W kg-1 @ 426.4 Wh kg-1 and 17970 W kg-1 @ 119.8 Wh kg-1 ) and outstanding capability to withstand long cycles (90.1% capacity retention after 1000 cycles at 105.3 mAh g-1 at 10 C).

Enhanced adsorption performance of bensulfuron methyl with B doping biochar: Mechanism and density functional theory calculations.

It is an urgent task to develop suitable adsorbents for the control of herbicide-bensulfuron methyl (BSM) in the paddy rice fields at cold regions. Herein, B doping biochar was synthesized via one-step method. Results showed that the adsorption capacity for BSM on 1.0BBC was significantly superior to BC at 15 °C. Besides, low temperature resistance, wide pH adaptability, stable adsorption performance and reusability test suggested that 1.0BBC have potential practical application. The mechanisms of BSM removal by 1.0BBC were mainly attributed to pore filling and π-π electron donor-acceptor (EDA) interaction. Theoretical calculations revealed that BCO2 could enhance the adsorption capacity by π-π EDA between BSM and adsorbent. Meanwhile, hydroponic experiment demonstrated that the toxicity to soybean after adsorption of BSM by 1.0BBC was within the safe range. This study proves that 1.0BBC is an easy-to-prepare adsorbent with promising application in BSM removal in the rice paddy fields at lower temperature.

High-performance K-ion half/full batteries with superb rate capability and cycle stability.

SignificanceThe present work might be significant for exploring advanced K-ion batteries with superb rate capability and cycle stability toward practical applications. The as-assembled K-ion half cell exhibits an excellent rate capability of 428 mA h g-1 at 100 mA g-1 and a high reversible specific capacity of 330 mA h g-1 with 120% specific capacity retention after 2,000 cycles at 2,000 mA g-1, which is the best among those based on carbon materials. The as-constructed full cell delivers 98% specific capacity retention over 750 cycles at 500 mA g-1, superior to most of those based on carbon materials that have been reported thus far.

Lattice B-doping evolved ferromagnetic perovskite-like catalyst for enhancing persulfate-based degradation of norfloxacin.

Series of B-doped perovskite-like materials CeCu0.5Co0.5O3 (B-C3O) were fabricated with unique ferromagnetic property due to partial substitution of non-magnetic 2p-impurities boron in the lattice. Then, B-C3O was used for activating peroxymonosulfate (PMS) for the degradation of norfloxacin (NOR), one kind of emerging pollutants with the concentration level up to mg/L in wastewaters. The results indicated that 5.0% B-C3O exhibited stable catalytic ability at pH 3.0-9.0 and high degradation efficiency in co-existing inorganic Cl-, SO42-, NO3-, H2PO4- and organic humic acid. Non-radical 1O2, radicals •OH and SO4•-, as well as ClO- were detected with synergy effect for NOR degradation. By quantifying free radicals, •OH with 0.52 µM and SO4•- with 10.91 µM were obtained at 180 min, verifying the leading role of SO4•-. The degradation process involved the defluorination and decarboxylation, as well as opening of quinolone and piperazinyl rings. Adopting alfalfa as the model plant, the toxicity effect before and after NOR degradation was finally evaluated with seed germination rate and chlorophyll content as the physiological indicators. In summary, non-metal B-doping not only provides a creative strategy for the development of ferromagnetic perovskite-like materials, but also affords excellent catalysts for aiding the advanced oxidation technology for removal of emerging pollutants in wastewaters.

Transition-metal-free boron doped SbN monolayer for N2 adsorption and reduction to NH3: A first-principles study.

Electrochemical nitrogen reduction reaction (NRR) in ambient condition is an efficient and sustainable method to synthesize NH3. In this work, first-principles study was used to discuss the NRR process on B atom doped SbN monolayer. The adsorption of N2 on B-Sb17N18 and B-S18N17 was calculated including the adsorption energy, adsorption distance, and the charge density difference (CDD). Five different reaction pathways of NRR were taken into consideration and the stability of B-SbN was investigated. The results show that, because the energy of unoccupied orbital in sp3 hybridization of B atom is much lower than that in 2pz orbitals, the adsorption of N2 on B-Sb18N17 shows much larger adsorption energy (-1.01 eV with end-on pattern) compared to that of the adsorption on B-Sb17N18. For five different pathways, the 1, 2, and 4 pathways have a smaller limiting potential of about 0.52 V and the limiting step is: *N2 + H+ + e- â†’ *NNH. The 3 and 5 pathways have a larger limiting potential of 0.57 V with hydrogenation step: *NHNH2 + H+ + e- â†’ *NH2NH2. The B-Sb18N17 is structurally and thermally stable even at 500 K. Our theoretical prediction indicates that B atom substitutionally doped SbN monolayer can be a kind of high-performance metal-free NRR catalyst for NH3 synthetization, and the work provides attempts for designing and exploring 2D metal-free NRR catalysts.

Ionic liquid-assisted synthesis of porous boron-doped graphitic carbon nitride for photocatalytic hydrogen production.

This work presents a simple way to prepare boron-doped graphitic carbon nitride (B/g-C3N4), exhibiting an enhanced photocatalytic performance to split water for hydrogen production. B/g-C3N4 was synthesized via the pyrolysis of urea and 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim]BF4), which was adopted as the boron source. The aggregate of B/g-C3N4 nanosheets shows a porous structure since some bubbles are generated under the heat decomposition of ionic liquids. The porous structure is conducive to the exposure of more active sites. Moreover, B-doping will form some localized electronic energy levels in the band gap of g-C3N4, thereby extending its visible light response. As impacted by the porous structure of B/g-C3N4 aggregate and the narrow the band gap, the photocatalytic hydrogen generation rate (901 µmol h-1 g-1) is increased, almost 3 times faster than g-C3N4 (309 µmol h-1 g-1). This work proposed a simple method to prepare the aggregate of B/g-C3N4 nanosheets exhibiting pores under ionic liquid assistance. It can be a novel method to design porous polymer photocatalysts.

Giant Piezoresistance in B-Doped SiC Nanobelts with a Gauge Factor of -1800.

The giant piezoresistance effect (PRE) of semiconductors as featured by a high gauge factor (GF) is recognized as the prerequisite for realizing optimal pressure sensors with desired high sensitivity. In this work, we report the discovery of giant PRE in SiC nanobelts with a record GF measured using an atomic force microscope. The transverse piezoresistance coefficient along the [111] direction reaches as high as -312.51 × 10-11 pa-1 with a corresponding GF up to -1875.1, which is twice more than the highest value ever reported on SiC nanomaterials. The first-principles calculations reveal that B doping turns the acceptor states in the bandgap into deeper impurity levels, which makes the major contribution to the observed giant piezoresistance behavior. Our result provides new insights on designing pressure sensors based on SiC nanomaterials.

10B Conformal Doping for Highly Efficient Thermal Neutron Detectors.

This paper reports a simple and novel conformal doping strategy for microstructured silicon diodes using enriched 10B for sidewall doping while enabling enhanced neutron sensitivity. Monte-Carlo nuclear particle (MCNP) code simulations were initially used to calculate the neutron detection efficiency in the microstructured diodes as a function of geometry and pitch. A high-temperature anneal in 10B-filled diodes results in a conformal silicon p+ layer along the side walls of the trenches in the diodes. This results in large neutron detection areas and enhanced neutron detection efficiency when compared with planar detectors. With the method discussed here, a thermal neutron detection of ∼21% efficiency is achieved, which is significantly higher than the efficiency achieved in planar detectors (∼3.5%). The higher efficiency is enabled by the 10B acting as a source for conformal doping in the trenches, resulting in lower leakage current while also enabling neutron sensitivity in the microstructured diodes.

Transforming Photocatalytic g-C3 N4 /MoSe2 into a Direct Z-Scheme System via Boron-Doping: A Hybrid DFT Study.

Z-scheme photocatalytic systems are an ideal band alignment structure for photocatalysis because of the high separation efficiency of photo-induced carriers while simultaneously preserving the strong reduction activity of electrons and oxidation activity of holes. However, the design and construction of Z-scheme photocatalysts is challenging because of the need for appropriate energy band alignment and built-in electric field. Here, we propose a novel approach to a Z-scheme photocatalytic system using density functional theory calculations with the HSE06 hybrid functional. The undesirable type-I g-C3 N4 /MoSe2 heterojunction is transformed into a direct Z-scheme system through boron doping of g-C3 N4 (B-doped C3 N4 /MoSe2 ). Detailed analysis of the total and partial density of states, work functions and differential charge density distribution of the B-doped C3 N4 /MoSe2 heterojunction shows the proper band alignment and existence of a built-in electric field at the interface, with the direction from g-C3 N4 to MoSe2 , demonstrating a direct Z-scheme heterojunction. Further investigation on the absorption spectra reveals a large enhancement of the light absorption efficiency after boron doping. The results consistently confirm that electronic structures and photocatalytic performance can be effectively manipulated by a facile boron doping. Modulating the band alignment of heterojunctions in this way provides valuable insights for the rational design of highly efficient heterojunction-based photocatalytic systems.

Boron-Induced Electronic-Structure Reformation of CoP Nanoparticles Drives Enhanced pH-Universal Hydrogen Evolution.

Even though transition-metal phosphides (TMPs) have been developed as promising alternatives to Pt catalyst for the hydrogen evolution reaction (HER), further improvement of their performance requires fine regulation of the TMP sites related to their specific electronic structure. Herein, for the first time, boron (B)-modulated electrocatalytic characteristics in CoP anchored on the carbon nanotubes (B-CoP/CNT) with impressive HER activities over a wide pH range are reported. The HER performance surpasses commercial Pt/C in both neutral and alkaline media at large current density (>100 mA cm-2 ). A combined experimental and theoretical study identified that the B dopant could reform the local electronic configuration and atomic arrangement of bonded Co and adjacent P atoms, enhance the electrons' delocalization capacity of Co atoms for high electrical conductivity, and optimize the free energy of H adsorption and H2 desorption on the active sites for better HER kinetics.

Novel B-doped BiOCl nanosheets with exposed (001) facets and photocatalytic mechanism of enhanced degradation efficiency for organic pollutants.

Novel B doped BiOCl nanocrystals (B-BiOCl) with exposed (001) facets were fabricated via a facile solvothermal route. The characterization methods of XRD, BET, SEM, TEM, UV-vis DRS, PL, EIS, ESR and photocurrent measurement were performed to investigate the physicochemical properties of the B-BiOCl samples. The results indicated that doping B into BiOCl could regulate and control the growth of (001) crystal facet, increase the specific surface areas and enhance the efficiency of charge separation. Hence, the optimal B1.0-BiOCl (atomic ratio of Bi:O:Cl: B is around 27.41: 28.27:25.43:3.55) exhibited significant promoting effect for the degradation of phenol, bisphenol A and rhodamine B than that of pure of BiOCl. The results of radical capturing and ESR analysis confirmed that the O2- radicals played a fatal role in the degradation of organic pollutants. This work could be expected to offer a new insight into design and synthesis of highly efficient photocatalyst with specific exposed facets by doping non-metallic elements.

Ag loaded B-doped-g C3N4 nanosheet with efficient properties for photocatalysis.

Three material engineering strategies in the form of doping (Boron-doping), nanostructuring (nanosheet (NS) formation) and decorating with plasmonic nanoparticles (loading with Ag metal), were integrated to improve the photocatalytic activity of graphitic carbon nitride (gC3N4). Concentrations of B-doping and Ag-loading were optimized to maximize the catalytic performance in the final nanocomposite of Ag-loaded B-doped gC3N4 NS. Combined effect of all three strategies successfully produced over 5 times higher rate towards degradation of organic dye pollutant, when compared to unmodified bulk gC3N4. Detailed characterization results revealed that incorporation of B in gC3N4 matrix reduces the band gap to increase the visible light absorption, while specific surface area is significantly enhanced upon formation of NS. Decoration of Ag nanoparticles (NPs) on B-doped gC3N4 NS assists in fast transfer of photogenerated electrons from gC3N4 to Ag NPs owing to the interfacial electric field across the junctions and thus reduces the recombination process. Investigations on individual strategies revealed that decoration of Ag NPs to induce better charge separation, is the most effective route for enhancing the photocatalytic activity.

Superior B-Doped SiC Nanowire Flexible Field Emitters: Ultra-Low Turn-On Fields and Robust Stabilities against Harsh Environments.

Low turn-on fields together with boosted stabilities are recognized as two key factors for pushing forward the implementations of the field emitters in electronic units. In current work, we explored superior flexible field emitters based on single-crystalline 3C-SiC nanowires, which had numbers of sharp edges, as well as corners surrounding the wire body and B dopants. The as-constructed field emitters behaved exceptional field emission (FE) behaviors with ultralow turn-on fields (Eto) of 0.94-0.68 V/µm and current emission fluctuations of ±1.0-3.4%, when subjected to harsh working conditions under different bending cycles, various bending configurations, as well as elevated temperature environments. The sharp edges together with the edges were able to significantly increase the electron emission sites, and the incorporated B dopants could bring a more localized state close to the Fermi level, which rendered the SiC nanowire emitters with low Eto, large field enhancement factor as well as robust current emission stabilities. Current B-doped SiC nanowires could meet all essential requirements for an ideal flexible emitters, which exhibit their promising prospect to be applied in flexible electronic units.

First-Principles Investigation of Adsorption and Diffusion of Ions on Pristine, Defective and B-doped Graphene.

We performed first-principles calculations to reveal the possibility of applying pristine, defective, and B-doped graphene in feasible negative electrode materials of ion batteries. It is found that the barriers for ions are too high to diffuse through the original graphene, however the reduced barriers are obtained by introducing defects (single vacancy, double vacancy, Stone-Wales defect) in the graphene. Among the three types of defects, the systems with a double vacancy could provide the lowest barriers of 1.49 and 6.08 eV for Li and Na, respectively. Furthermore, for all kinds of B-doped graphene with the vacancy, the systems with a double vacancy could also provide the lowest adsorption energies and diffusion barriers. Therefore, undoped and B-doped graphene with a double vacancy turn out to be the most promising candidates that can replace pristine graphene for anode materials in ion batteries.