Substitutional Boron Research Articles

Photoelectric transport signals induced by the periodical B/P substitution of doped graphene half-metals

Abstract Using the nonequilibrium Green’s function combined with the density functional theory, we investigate the spin-resolved photoelectric current in ferromagnetic hydrogenated zigzag graphene nanoribbons with boron or phosphorus atom substitutions (B/P-ZGNRs). Our findings indicate that B/P substitution induces half-metallic or semiconducting characteristics, depending on the edge form and substituted atoms. Induced by linear polarized light, the spin-resolved photocurrent could reveal information of the band structure and the contribution of different orbitals to the transport processes. Photocurrent peaks at specific photon energies clearly indicate the band edge of B/P-ZGNRs, while its signs reflect the distribution of the transmission coefficient spectrum. In symmetrically hydrogenated B/P-ZGNRs, the px orbital is found to be dominant. However, in asymmetric B/P-ZGNRs, the py orbital can also be dominant. Furthermore, B/P substitution induces a narrow band near the Fermi level, leading to remarkable negative differential resistance. These findings suggest potential applications of B/P-ZGNRs in spintronic devices and micro photoelectric detection.

Origin of high stability, enhanced specific capacity, and low Li diffusion energy in boron doped Li3V2(PO4)3

Li3V2(PO4)3 (LVP) is a well-known cathode material of Li-ion batteries, whereas the specific capacity is limited by the maximum Lithium (Li) de-intercalation probability associated with vacancy energy. The reason behind this limitation is not known yet, which needs to be address, and the modification needs to be done in the electronic structure to get a more specific capacity. In this work, using First-principles calculation, we have found that Li1 (the tetrahedra geometry) is having a higher Li vacancy energy as compared to Li2 and Li3, which limits the Li de-intercalation below x = 1.8, (where x is Li concentration). The change in bandgap of LVP structure after boron (B) substitution is directly correlated to the change in the oxygen (O) occupancy due to B substitution. As of comparing formation energy plot of pristine LVP and B substituted LVBP structure, we have found that in case of LVBP structure formation of x > 2 Li de-intercalation is possible, which help to enhance the specific capacity up to 205 mAh/g. Overall, we identify the cause of the less specific capacity of LVP and provide the solution by suggestion B doping, which also provides less Li diffusion barrier energy.

Minority Carrier Traps Induced by Neutron Reactions with 4H-SiC

This work presents the characterization of minority carrier traps in epitaxial n-type 4H-SiC after high fluence neutron irradiation using minority carrier transient spectroscopy (MCTS) in a temperature range of 20 K to 660 K. Three minority carrier trap levels are reported, labelled as X, B and Y, whose activation energies were estimated by Arrhenius analysis and where the B level is assigned to substitutional boron (BSi). The dynamic behaviour of the trap levels was studied by consecutive temperature scans.

A Playground for Heavy Atom Tunnelling: Neutral Substitutional Defect Rearrangement from Diamondoids to Diamonds.

Many diamond properties are defined by substitutional defects (i. e., a carbon atom replaced by another element), which may involve the formation of structural isomers that can interconvert. Herein, we analysed by computational means the structure, thermodynamics, and kinetics of substitutional nitrogen, boron, and oxygen from small diamondoids up to the diamond bulk, focusing on the possibility of heavy atom quantum tunnelling rearrangement between the isomers. The large range of threshold energies and bond lengths lead to a variety of intriguing behaviours, including cage size dependent thermally activated tunnelling of nitrogen, and quantum delocalization of boron. In addition, we predict that applying an external electric field makes it possible to control the rearrangement thermodynamics and kinetics through tunnelling, which lets us hypothesize that these systems can potentially be used as atomic memory devices.

Cope-Type Hydroamination of Vinylboronates.

Aminoboronic acid derivatives can serve as versatile synthetic intermediates and pharmacophores but remain difficult to synthesize. Herein we report a synthesis of the β-aminoboronic acid motif via anti-Markovnikov hydroamination of vinylboronates. This reaction benefits from the activating effect of the boronate substituent and forms novel BON-containing heterocycles, oxazaborolidine zwitterions. A computational study is included to help determine the effects of alkene boron substitution. Derivatization reactions also support the synthetic utility of the oxazaborolidine adducts.

Structural, microstructural, and microwave dielectric properties of (Al1-xBx)2Mo3O12 ceramics with low dielectric constant and low dielectric loss for LTCC applications

The (Al1-xBx)2Mo3O12 ceramics with double phases were prepared by solid-phase sintering method at the temperature from 725 to 800 °C for LTCC application. Through XRD pattern and Rietveld refinement analysis, it was confirmed that the (Al1-xBx)2Mo3O12 composition consists of the coexistence of double phase (the monoclinic structure of the P21/a space group and the orthorhombic structure of the Pnca space group), and the orthorhombic phase was increased with boron substitution. The microwave dielectric properties of the (Al1-xBx)2Mo3O12 ceramic series were impacted by double-phase formation (crystal structure ratio), which increases the densification and grain uniformity. With the boron substitution, the (Al1-xBx)2Mo3O12 ceramic series demonstrate outstanding microwave dielectric properties (εr = 4.04, Q × f = 35870 GHz @ 15 GHz, τƒ = 4.2 ppm/°C) with high relative density (ρrel ≈ 98.84%) and thermal conductivity κ = 0.88 W/m.K for x = 0.3 at 775 °C, indicate that it is a promising candidate for LTCC substrate material.

Localized and quasi-localized energy levels in the electron spectrum of graphene with isolated boron and nitrogen substitutions

Based on the calculation and analysis of local Green’s functions of impurity atoms of low concentration in a two-dimensional graphene lattice, the conditions for the formation and characteristics of local discrete levels with energies lying outside the band of the quasi-continuous spectrum and quasi-localized states with energies near the Fermi one are determined. Specific calculations were performed for boron and nitrogen impurity atoms, which can actually replace carbon in graphite and graphene nanostructures. For a boron impurity that forms local discrete levels outside the band of the quasi-continuous spectrum, sufficiently simple analytical expressions for the conditions for their formation, energy, intensity at the impurity atom, and damping parameter are obtained. An analysis of the formation of states quasi-localized on nitrogen impurities with energy near the Fermi level in graphene nanostructures was carried out.

Theory of shallow and deep boron defects in 4H -SiC

Abstract Despite advances toward improving the quality of $p$-type 4H-SiC substrates and layers, we still have no model capable of accounting for the multitude of boron-related optical, junction, and paramagnetic resonance experiments available in the literature. A conspicuous puzzle is the observation of two shallow boron defects with rather distinct axial orientations as found by electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) data. This feature is not observed in material doped with other group-III elements. Another open issue involves conflicting conclusions from photoluminescence and EPR studies of a deeper boron center, which has been linked to rather distinct models, either based on substitutional or vacancy-related boron defects. We unlock these and other problems by means of first-principles calculations, where the temperature-dependent stability, the electronic activity, and the paramagnetic response of boron defects in 4H-SiC are investigated.

(Best Student Presentation Award) Reduced Pressure – Chemical Vapor Deposition of Monocrystalline and Polycrystalline Si(:B) and SiGe(:B) Layers on Blanket Wafers

Monocrystalline SiGe alloys can be used instead of monocrystalline Si in order to increase the performances of devices such as heterojunction bipolar transistors (HBTs) [1]. The epitaxial growth of blanket, monocrystalline SiGe layers on Si with a dichlorosilane + germane + hydrochloric acid chemistry was extensively investigated in the literature [2,3]. Similarly, a switch from polycrystalline Si to polycrystalline SiGe can be favorable, for instance, in Complementary-MOS (C-MOS) devices [4,5]. However, the blanket growth by Reduced-Pressure Vapor Deposition (RP-CVD) of polycrystalline Si and SiGe has not been systematically investigated. We have thus performed a one-to-one comparison in terms of growth kinetics and electrically active dopant incorporation between blanket monocrystalline and polycrystalline Si(:B) and SiGe(:B) layers.Epitaxies or depositions were performed, in 300 mm RP-CVD chambers, on two types of templates (Fig.1): i) N-type Si substrates (Fig.1(a)) and ii) poly-Si/oxide/ P-type Si substrates (Fig.1(b)). The poly-Si layer in stack 1.(b) was obtained thanks to amorphous Si deposition followed by annealing at 750 °C, resulting in a poly-Si film. SiH4+HCl+H2 (named Process 1) and SiH2Cl2 (DCS)+HCl+GeH4+H2 (named Process 2) chemistries were used to deposit Si and SiGe layers between 675-750 °C and 10-20 Torr.Monocrystalline and polycrystalline SiGe growth kinetics for two process conditions: i) 750 °C, 10 Torr with a HCl partial pressure of 0.05 Torr and ii) 725 °C, 10 Torr, with a HCl partial pressure of 0.06 Torr, were similar to that in the literature [1-3, 6-8]. As already shown for monocrystalline layers, there was an increase of the intrinsic SiGe growth with the germane partial pressure and the temperature. Meanwhile, it was reduced when adding HCl (Fig.2). Very similar growth rates and evolutions were however obtained whatever the crystalline state of the layers.When diborane was added the gaseous mixture, different behaviors were evidenced depending on i) the crystallinity and ii) the stoichiometry. The Si:B and SiGe:B growth rates increased with the B2H6 flow whatever the chemistry (Fig.3). This was due to a hydrogen desorption increase on boron surface sites [5,10-11]. Growth rates were otherwise higher for monocrystalline than for polycrystalline layers. The electrical resistivities of c-Si:B and c-SiGe:B layers were one decade lower than those of poly-Si:B and poly-SiGe:B layers, however (Fig.4). Resistivity values were otherwise higher for c-Si:B than for c-SiGe:B. This was likely due to i) a better incorporation of B atoms into SiGe than in Si [3,8,9] and ii) a better hole mobility in SiGe [10]. An opposite behavior was observed for polycrystalline layers, with higher resistivities for poly-SiGe:B than for poly-Si:B. We otherwise had similar resistivity evolutions as the partial pressure of diborane Pp(B2H6) increased for all types of layers. A decrease was observed first, followed by a resistivity plateau then some resistivity re-increase for really high diborane flows. Such a phenomenon was already observed for monocrystalline layers and was explained by a crystalline quality degradation [3,8,9] that reduced the hole mobility. A similar behavior was assumed for poly-layers, with a morphological transition to the amorphous phase [11,12]. Top-view Scanning Electron Microscopy (SEM) images (Fig. 5) confirmed the morphological evolution of c-Si:B, poly-Si:B, c-SiGe:B and poly-SiGe:B as the diborane partial pressure increased.New data points for c-SiGe and c-SiGe:B will also be provided for other process conditions. For intrinsic layers, we will show that Refs. [1,2] x2/(1-x) = n×(F(GeH4)/F(SiH2Cl2)) relationship between the Ge concentration x and the germane over dichlorosilane mass-flow ratio is also valid at 10 Torr, with n = 3 at 700 °C with a F(SiH2Cl2)/F(H2) Mass-Flow Ratio (MFR) of 0.005 and a F(HCl)/F(H2) MFR of 0.006. Various characterization techniques were also used to determine the concentration of substitutional Boron atoms in SiGe:B layers and the lattice contraction coefficient (β = 9.11×10-24 cm3). The value of the latter, which is most useful to assess the compressive strain compensation by small boron atoms in SiGe layers, will be compared to literature values.[1] J. Appl. Phys. 88 (2000) 4044[2] J. Crystal Growth 305 (2007) 113[3] J. Crystal Growth 310 (2008) 62[4] J. Microelec. Sys. 16 (2007) 68[5] International Electron Devices Meeting (1991) 567[6] Appl. Phys. Lett. 56 (1990) 1275.[7] S. Chang et al., ECS Proceedings 87–8 (1987) 122[8] J Mater Sci: Mater Electron (2007) 18:747[9] ECS Trans. 75, 8 (2016) 265[10] Mater. Sci. Eng. B 114–115 (2004) 318[11] Appl. Phys. Lett. 66 (1995) 195[12] ECS Trans. 35, 30 (2011) 45 Figure 1

Spatial segregation of substitutional B atoms in graphene patterned by the moiré superlattice on Ir(111)

Fabrication of ordered structures at the nanoscale limit poses a cornerstone challenge for modern technologies. In this work we show how naturally occurring moiré patterns in Ir(111)-supported graphene template the formation of 2D ordered arrays of substitutional boron species. A complementary experimental and theoretical approach provides a comprehensive description of the boron species distribution, bonding configurations, interfacial interaction with Ir(111) and the impact on graphene's electronic structure. Atomically-resolved scanning tunnelling microscopy images and density functional theory calculations reveal that boron preferably forms small aggregates of substitutional defects in geometrically low regions of the moiré superlattice of graphene, by inducing local bending of graphene towards the underlying Ir(111). Surprisingly, calculations reveal that the incorporation of electron deficient boron does not lead to an enhanced p-type doping, as the local rippling of the graphene layer prompts electron uptake from the iridium substrate that compensates the initial electron loss due to substitutional boron. Scanning tunnelling spectroscopy and angle-resolved photoemission spectroscopy measurements corroborate that the arrays of boron species do not modify the electronic structure of graphene near the Fermi level, hence preserving the slight p-type doping induced by Ir(111).

Structural features of heavily boron-doped graphite and diamond microcrystals synthesized at high pressures

Heavily boron-doped graphite was synthesized from a mixture of adamantane and boron using a high-pressure technique. Ab initio calculations of a carbon cluster of 64 atoms located in two layers of graphene with the inclusion of one boron atom were made. Substitution of boron for carbon in the graphene layer correlates with the experimental data if we consider the change in the cell parameters. The easy transformation of the boron-doped graphite lattice into a diamond one at pressure of about 7.5 GPa may be due to the presence of a small number of boron atoms between graphene layers. Heavily boron-doped diamond crystals in the shape of a five-pointed star were found. The mechanism of their growth includes cyclic twinning and is obviously associated with the presence of a fluid phase in the synthesis medium and facilitated twinning of a diamond lattice containing boron.

Stabilization of Extra-Large-Pore Zeolite by Boron Substitution for the Production of Commercially Applicable Catalysts.

Stable extra-large-pore zeolites are desirable for industrial purposes due to their ability to accommodate bulky reactants and diffusion through channels. Although there are several extra-large pore zeolites reported, stable ones are rare. Thus, their stabilization is a feasible strategy for industrial applications. Here, an extra-large-pore zeolite EWT with boron substitution is presented, and the resulting zeolite B-RZM-3 increased the thermal stability from 600 °C in its silica form to 850 °C. The crystal structure, determined by combining continuous rotation electron diffraction (cRED) and powder X-ray diffraction (PXRD), shows that B atoms preferentially substitute the interrupted (HO)T(OT)3 (Q3 ) sites and are partially converted into 3-coordination to relax framework deformation upon heating. After Al-reinsertion post-treatment, Al-B-RZM-3 shows higher ethylbenzene selectivity and ethylene conversion rate per mol acid site than commercial ZSM-5 and Beta zeolite in benzene alkylation reaction. Synthesizing extra-large-pore zeolite in borosilicate form is a potential approach to stabilize interrupted zeolites for commercial applications.

Rotational and Gas Temperature Measurements for He-C Plasma: Application to Heterogeneous Carbon Nanotubes Synthesis

Plasmas containing carbon cover a wide range of application, either using graphite electrodes or carbon containing plasma gas. The study of the C2 molecule is an interesting way to get information on moderate temperature part of the discharge. In the case of heterogeneous carbon nanotubes (CNTs) synthesis by electric arc, reasonable yield can be achieved with substitution of boron and/or nitrogen atoms by optimizing synthesis parameters. This is based on the knowledge of the plasma and gas temperatures in the synthesis chamber. While electrodes material is vaporized through the arc, nanotubes formed in the growth zone a few centimeters away, when temperature decreases down to 1200 °C–1500 °C. Molecular temperature is particularly relevant since it corresponds to the outer part of the arc, in contact with the growth zone. In this article, Abel inversion is used on side-on integrated spectral profiles for C2(0,0) Swan band, in order to get radial rotational temperature profiles. In addition, gas temperature measurements are performed using thermocouples in the arc chamber. Results show that a strong plasma temperature gradient is associated with favorable synthesis conditions for carbon-bore-nitrogen nanotubes. Gas thermal homogeneity is reached in the chamber after about 30 s, mainly through convection processes.

Synthesis of [B,Al]-EWT-Type Zeolite and Its Catalytic Properties

EWT zeolite belongs to ultra-large pore zeolite with the 10MR and 21MR channels, which has good thermal stability, certain acid strength and good application prospects in petroleum refining and petrochemical reactions. However, EWT zeolite has fewer medium/strong acid sites, especially Brönsted acid sites, which makes it difficult to apply to acid-catalyzed reactions. The regulation of acid amount and distribution was achieved by boron and aluminum substitution into the siliceous framework of EWT. The physico-chemical properties of the samples were characterized by XRD, SEM, N2 adsorption-desorption, XRF, ICP, Py-IR, NH3-TPD and 11B & 27Al & 29Si MAS NMR. The results show that quantities of boron and aluminum elements can occupy the framework of [B,Al]-EWT to increase the density of medium and strong acid centers, with more acidity and Brönsted acid centers than EWT zeolite. In the reaction of glycerol with cyclohexanone, the conversion of the sample (U-90-08-10/U-90-H-HCl) is significantly higher than that of the EWT sample, approaching or exceeding the Beta zeolite. A catalytic activity study revealed a direct correlation between the Brönsted acidic site concentration and the activity of the catalyst. The U-90-08-10-H catalyst was also considerably stable in the catalytic process. This work shows, for the first time, that extra-large pore zeolites can be used in industrial acid-catalytic conversion processes with excellent catalytic performance.

First-Principles Study of Two-Dimensional B-Doped Carbon Nanostructures for Toxic Phosgene Gas Detection

The diverse coordination environment on the surface of carbon-based nanomaterials contributes significantly to their unique adsorption properties. Here, we perform first-principles calculations to determine the sensitivity and selectivity of pristine, 1B, and homonuclear 2B-doped graphdiyne, pentagraphene, and phagraphene structures toward toxic phosgene (COCl2) gas molecule. The strength of the phosgene gas adsorption on the perfect surfaces is negligible, while the substitution of homonuclear boron on the studied substrates can make inert carbon allotropes into an active material for capturing the COCl2 gas molecule. Further, the charge density difference and Lowdin charge analysis were computed to provide additional insights for understanding the phenomenon clearly, and the results are completely consistent with the observed trends. The prominent changes in the electronic structure of homonuclear boron-doped surfaces indicate strong reactivity toward phosgene gas molecules, thereby inducing significant variations in the conductivity or resistivity of the sensing device. The π electron occupancy is correlated with the sensing of carbon materials toward phosgene. Overall, homonuclear 2B-doped graphidyne and 1B/2B-doped pentagraphene display high selectivity and sensitivity with better performance, which makes them potential candidates toward target phosgene gas molecules. These fundamental atomic-scale insights may furnish novel outcomes into the rational design of defect engineered carbon-based nanomaterials for the detection of toxic phosgene gas molecules.

Computationally Efficient Region-Wise Potential- Based Extremely Closed-Form Analytical Modeling of B/N Substitution Doped GFETs

A simplified region-wise potential-based analytical model is established for boron (B) or nitrogen (N) substitution doped graphene field-effect transistor (GFET). The closed-form direct analytical relation between graphene channel potential and applied bias condition is developed by imposing the effective approximation for Fermi–Dirac integral function in various regions of operation. The boundary for distinct GFET operating regime is separated based on the position of Dirac point and Fermi energy level with respect to applied bias condition. The semiclassical drift and diffusive transport model is utilized to obtain the drain current. In addition to that, the drift component, diffusion coefficient, and its corresponding current component for B and N substitution doped GFETs have been modeled individually and their influence on total current is discussed. The proposed region-potential-based analytical model has shown good agreement with numerically solved self-consistent model. Also, the physical insights in device design, such as threshold voltage and saturation drain potential model with respect to various doping/device parameters, have been examined.

(Digital Presentation) Investigations into the Capacity Degradation Due to an Electronic Structural Change in Homogenous Boron-Substituted Ni-Rich Layered Oxides

Ni-rich layered oxides (LiNixCoyMnzO2, x≥0.8, x+y+z=1) would fulfil the energy density requirements of the automobile industry since they offer outstanding capacities at relatively high mean voltages and sufficient power densities1-3. However, the materials still show significant capacity and voltage fade which requires substantial research. Recently we have shown that the electronic structure is the key to understand the performance but also the failure of the materials1. Thus, we intend to modify the electronic structure using anionic dopants such as Boron. Thus, homogenous B-substituted NCM811s (BNCM811_x%, x% means the x at. % of Boron) are synthesized and the materials reveal a significant change in the electronic structure as evident from x-ray photoelectron spectroscopy (XPS) and near edge x-ray absorption spectroscopy (NEXAFS). Interestingly, a shift of the so called H2-H3 peak4 to higher potentials was observed by Boron substitution and BNCM811s_2% shows relative higher initial discharge capacity (Figure 1A.) at a slightly higher mean voltage, but a lower cycling stability compared to NCM811 (Figure 1B.).The H2-H3 differential capacity peak (Figure 1C) might also include oxygen release5, which is one of the main reasons restricting the cycling stability. Near edge x-ray absorption spectroscopy (NEXAFS) shows that the H2-H3 peak corresponds to a reaction from Ni3+ to Ni2+ (upon charge) and Ni2+ to Ni3+ (upon discharge) which suggest a reaction like NiO2 ⥂ NiO + ½ O2 as the underlying process. At the same time, an Oxygen K peak at 531 eV appears in the NEXAFS spectra, which was assigned to O-O formation in the host structure of Li-rich materials6, 7. Note that the electronic structure of the materials was determined in 5 mAh/g steps over the H2-H3 peak and due to the high resolution, this process became visible for the first time. The findings suggest that dimer formation is not only a phenomenon of Li-rich materials but can also be found in Ni-rich layered oxides at high states of charge.The origin of dimer formation and oxygen release can be traced back to the electronic configuration of Ni. Charge transfer multiplet calculations reveal, that Ni2+ reacts to covalent Ni3+ upon charge (and vice versa upon discharge)1. Ni3+ has a 3d7 electronic state, whose low spin configuration is more preferred than its high spin configuration. Thus, Ni3+ is more prone to Jahn-Teller (JT) distortions and tends to form covalent bonds. Consequently, the electrons are more bound to the individual sites making a further oxidation of the transition metal almost impossible. In conclusion, Boron substitution helps us to understand the function and failure of layered oxides in Li-ion batteries on an atomistic scale and the findings can be used as a design guide for future materials. K. Kleiner, C. A. Murray, C. Grosu, B. Ying, M. Winter, P. Nagel, S. Schuppler and M. Merz, Journal of The Electrochemical Society, 2021.J. Zhao, W. Zhang, A. Huq, S. T. Misture, B. Zhang, S. Guo, L. Wu, Y. Zhu, Z. Chen and K. Amine, Advanced Energy Materials, 2017, 7, 1601266.S.-J. Yoon, K.-J. Park, B.-B. Lim, C. S. Yoon and Y.-K. Sun, Journal of the Electrochemical Society, 2014, 162, A3059.S. Jamil, G. Wang, L. Yang, X. Xie, S. Cao, H. Liu, B. Chang and X. Wang, Journal of Materials Chemistry A, 2020, 8, 21306-21316.K. Märker, P. J. Reeves, C. Xu, K. J. Griffith and C. P. Grey, Chemistry of Materials, 2019, 31, 2545-2554.E. Hu, X. Yu, R. Lin, X. Bi, J. Lu, S. Bak, K.-W. Nam, H. L. Xin, C. Jaye and D. A. Fischer, Nature Energy, 2018, 3, 690-698.K. Kleiner, B. Strehle, A. R. Baker, S. J. Day, C. C. Tang, I. Buchberger, F.-F. Chesneau, H. A. Gasteiger and M. Piana, Chemistry of Materials, 2018, 30, 3656-3667. Figure 1

Effect of Boron Doping on the Interlayer Spacing of Graphite.

Boron-doped graphite was prepared by the heat treatment of coke using B4C powder as a graphitization catalyst to investigate the effects of the substitutional boron atoms on the interlayer spacing of graphite. Boron atoms can be successfully incorporated into the lattice of graphite by heat treatment, resulting in a reduction in the interlayer spacing of graphite to a value close to that of ideal graphite (0.3354 nm). With an increase in the catalyst mass ratio, the content of substituted boron in the samples increased significantly, causing a decrease in the interlayer spacing of the boron-doped graphite. Density functional theory calculations suggested that the effects of the substitutional boron atoms on the interlayer spacing of the graphite may be attributed to the transfer of Π electrons between layers, the increase in the electrostatic surface potential of the carbon layer due to the electron-deficient nature of boron atoms, and Poisson contraction along the c-axis.

Revealing different depth boron substitution on interfacial charge transfer in TiO2 for enhanced visible-light H2 production

Visible-light catalytic H2 production is being actively studied as a promising route to replace fossil fuel and improve the environment. Anion doped TiO2 is a kind of modified semiconductor with great research potential. However, the depth of anion substitution is difficult to control and hence its impact on photo-generated carriers is controversial. In addition, the effect of interfacial anion doping on the deposition behavior of co-catalyst is not clear. Herein, only bulk B-doped TiO2 (OB/TiO2) and surface to bulk B-doped TiO2 (STB/TiO2) were prepared successfully. They exhibited excellent visible-light catalytic H2 production rate, which were 73 times (488.4 μmol/g/h) and 26 times (171.6 μmol/g/h) higher than that of the Blank TiO2 (6.7 μmol/g/h), respectively. By multiple characterizations, directional deposition of Pt induced by electron-deficient structure was observed and photo-generated hole trapping site (Ti4+O2-Ti4+O•-) was identified in subsurface of TiO2. Surface B would accelerate the recombination of photo-generated carriers, and thus render the photocatalytic performance of OB/TiO2 superior to STB/TiO2. This work provides valuable insights for rationally designing anion doped TiO2 and maximizing the photocatalytic efficiency via structural optimizations.

DFT study for hydrogen storage on γ-Boron-Graphyne decorated with Li atoms

This work reports theoretical calculations for hydrogen storage on γ-B-Graphyne structure using DFT. The pristine γ-Graphyne is a 2D structure, with 2 kinds of hexagonal rings. The boron substitution on a pristine γ-Graphyne is characterized by the formation of a 2D structure, the molecular structure of the boron substitution on a pristine γ-Graphyne is very close to γ-Graphyne structure. Boron substitution on γ-Graphyne is developed to create an active site for metallic decorations. For hydrogen storage, the calculated gravimetric capacity is 6.94 wt%, this result reaches DOE gravimetric targets (6.5 wt%). To measure the hydrogen bonding on the 18Li—γ-B-Graphyne structure, the average binding energies, and adsorption energies for each H2 molecule are calculated, these values are between 0.321 and 0.353 eV, these values suggest that H2 adsorption at ambient temperatures is possible. The calculations reveal that Li decoration improves the hydrogen storage conditions. Finally, employing adsorption isotherms calculations, the equilibrium pressure is determined for the 18Li—γ-B-Graphyne.