Bare Bi Research Articles

Bismuth as a buffer layer for metal contact with silicon carbide studied by In situ photoelectron spectroscopy

Silicon carbide (SiC) is a promising third-generation semiconductor due to its wide bandgap. However, the high Schottky barrier and metal-induced gap states (MIGS) at the metal/SiC interface present significant challenges for device fabrication, leading to high contact resistance and poor current delivery. This study proposes the use of bismuth (Bi), with its semimetallic properties and gap-state saturation effect, as a contact buffer layer to address these issues. We conducted a systematic investigation of the chemical and electronic characteristics of the Pt/Bi/4H-SiC(0001) system, fabricated via molecular beam epitaxy (MBE), using in situ X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). Our findings reveal weak bonding between the Bi buffer layer and the 4H-SiC(0001) surface, resulting in a slight downward band bending effect and the formation of a substantial dipole across the Bi/4H-SiC(0001) interface. Moreover, UPS spectra indicate a reduction in the work function of Pt/Bi/4H-SiC(0001), suggesting the potential for achieving low contact resistance. Notably, the Pt/Bi/4H-SiC(0001) system remains stable when exposed to 1.6×109 Langmuir of oxygen at room temperature, while a bare Bi buffer layer undergoes partial oxidation. These results provide a comprehensive understanding of the Pt/Bi/4H-SiC(0001) interfaces and strategies for improving metal/SiC contacts.

Bi/UiO-66-derived electrocatalysts for high CO2-to-formate conversion rate

In the CO2 electrocatalytic reduction reaction (CO2RR) technology, high CO2 conversion rate is highly required for efficient CO2 utilization from the CO2 resource. In this study, we propose the strategy of combining UiO-66 metal organic framework (MOF) structure with Bi electrocatalyst for highly active CO2RR with selective formic acid production. The synthesized Bi/UiO-66 catalyst shows superior CO2 reduction property, 4.6 times higher current density at −0.7 V vs. reversible hydrogen electrode (RHE) than bare Bi without UiO-66 despite of low electrochemical surface area. Also, NH2 functionalized UiO-66 shows almost no effect on CO2RR as compared to without NH2 probably due to disassembled linkers during CO2RR. Various characterizations such as Fourier transform infrared (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) indicate carbonate species captured form of CO2 at Zr-MOF site should contribute the high CO2 conversion rate. Our findings demonstrate the feasibility of Zr-MOF as a Supporting material to achieve efficient CO2 reduction.

Strategic catalyst modification for boosting CO2 concentration at electrode surface and easing selective CO2 reduction at higher potential

PANI modification on the Bi flake surface enhances CO2 concentration at the electrode surface which slows down formate selectivity drop at higher potential as compared to bare Bi flakes.

Hierarchical Bi2WO6/BiFeWO6 n-n heterojunction as an efficient photocatalyst for water splitting under visible light

A hierarchical Bi 2 WO 6 /BiFeWO 6 architectures were synthesized by a facile and low-cost hydrothermal approach using Bi 2 WO 6 flower structure as an efficient backbone for the growth of layered BiFeWO 6 sheets. The conduction band offset and bandgap of flower like Bi 2 WO 6 were tailored strategically as active photocatalyst under visible light and suitable for water reduction. By developing n-n heterojunction between Bi 2 WO 6 and BiFeWO 6 , the active surface area as well as number of free charge carriers have been enhanced which may boost the catalytic redox reactions. The physicochemical properties of the heterojunction was characterized to investigate the phase, morphology, thermal stability, light absorption and oxidation states of the elements. The photocatalytic activity of Bi 2 WO 6 /BiFeWO 6 heterojunction was investigated through H 2 generation via water splitting under visible light, where four-fold enhanced activity achieved for heterojunction compared to bare Bi 2 WO 6 . Further, photoelectrochemical properties were studied to determine the band edge potentials and illustrate the enhanced photoresponse for heterojunction. The Bi 2 WO 6 /BiFeWO 6 heterojunction showed lower charge transfer resistance compared to Bi 2 WO 6 , owing to efficient charge separation at electrode-electrolyte interface. The synergistic effect of high surface area, lower recombination rate and the suitable band edge potentials led to high catalytic activity, good cycling stability and superior photoelectrochemical response of heterojunction. This work provide insight into the synergistic effect of hierarchical n-n heterojunction and opens up an avenue for rational design of photocatalyst for water splitting and H 2 generation. • The n-n Bi 2 WO 6 /BiFeWO 6 heterojunction has been developed • The photocatalytic H 2 generation of n-n Bi 2 WO 6 /BiFeWO 6 heterojunction is greatly enhanced. • The charge transfer mechanism are confirmed from Mott-Schottky analysis. • The synergistic effect of high surface area, lower recombination and suitable band edges led to high catalytic activity.

Synergistic effect of diatomite and Bi self-doping Bi2MoO6 on visible light photodegradation of formaldehyde

Good indoor air environment is of great significance for the health and comfort assurance of occupants. In this work, a series of bismuth self-doping Bi 2 MoO 6 /diatomite (BD-X) composites with different proportions of bismuth and molybdenum source were prepared via a mild solvothermal process. Under visible light irradiation, the BD-3 sample exhibited the optimal formaldehyde (HCHO) mineralization performance, and the corresponding calculated rate constant was up to 3.2 times higher than that of bare Bi 2 MoO 6 (B). The introduction of diatomite as catalyst carrier could not only contribute to the dispersion of nano-scale Bi 2 MoO 6 photocatalyst, but also promote the exposure of (001) crystal plane of Bi 2 MoO 6 . In particular, the molybdenum vacancy generated with increasing the proportion of bismuth source, which effectively facilitated the separation of photogenerated carriers. Moreover, the photogenerated holes (h + ) played the major role in the photocatalytic degradation process. Overall, this research would provide a novel binary composite photocatalyst derived from natural mineral for the high-efficient mineralization of formaldehyde under visible light. • An efficient adsorption-photocatalysis system was constructed with diatomite as carrier. • The molybdenum vacancy generated with increasing the proportion of bismuth source. • Diatomite and Bi self-doping Bi 2 MoO 6 promoted the synergistic photodegradation of HCHO. • Excellent photocatalytic mineralization of HCHO was obtained under visible light.

Photocatalytic degradation of tetracycline hydrochloride with visible light-responsive bismuth tungstate/conjugated microporous polymer

• The construction of Bi 2 WO 6 /CMPs composite with Sonogashira-Hagihara polymerization. • The optimized tetracycline hydrochloride degradation efficiency reached 84 %. • The interfacial heterojunction of composite facilitates the separation of e − and h + . Conjugated microporous polymer (CMP) is an emerging organic semiconductor with π-conjugated skeletons, and the bandgap of CMP can be flexibly modulated to harvest visible light. Based on the diversity and adjustability of monomers in CMP, we designed and synthesized donor-accepter (D-A) type BTN-CMP through Sonogashira-Hagihara cross-coupling polymerization, further in-situ constructing series of inorganic/organic Z-scheme BW/BTN- n composite in the presence of Bi 2 WO 6 . After optimization, the tetracycline hydrochloride ( C 0 = 10 mg·L −1 ) degradation efficiency reached 84% with BW/BTN-2 as catalyst in 90 min under visible light irradiation, the apparent rate constant k 1 is 0.017 min −1 , which is 1.7 and 5.7 times higher than bare Bi 2 WO 6 and BTN-CMP. X-ray photoelectron spectra and UV–Vis diffuse spectra showed that the enhanced photocatalytic activity originated from the tight heterojunction between Bi 2 WO 6 and BTN-CMP, which can extend the light absorption range and facilitate the separation and transport of photogenerated charges in the interface of heterojunction. The active species trapping experiments and electron spin resonance technique revealed that h + was the dominant active species during the photodegradation process of tetracycline hydrochloride (TCH). The present study demonstrated the feasibility to construct inorganic/organic composite for the photocatalytic degradation of environmental pollutants.

Enhanced catalytic activity and stability of bismuth nanosheets decorated by 3-aminopropyltriethoxysilane for efficient electrochemical reduction of CO2

Herein, the effects of the introduction of 3-aminopropyltriethoxysilane (APTES) on the intrinsic properties of functionalized Bi nanosheets (Bi-NHS) electrocatalyst and the electrocatalytic performance of CO2 reduction reaction were carefully studied. As a result, high selectivities (> 90 %) to formate in significantly wide potentials of 500 mV and the energy efficiency ΦHCOOH as high as 65.8 % at –0.66 V for the cathodic half reaction can be observed. In addition, the Bi-NHS electrode shows a maximal faradic efficiency of 96.0 % at –0.96 V and a low overpotential around 340 mV, maintains well-preserved catalytic activity, giving formate yield of 8.02 g L−1, in a long term of continuous electrolysis. Based on experiment and density functional theory (DFT) calculations, CO2 reduction to formate on Bi(001)-NHS surface is more energetically favorable than that on bare Bi(001) surface and the APTES is excellent ligands as promoters for stabilized catalytic performance of metallic bismuth.

RETRACTED: Synthesis of hollow structured Bi4O5Br2/Cu2O P–N heterojunctions with large surface area for enhanced photocatalytic performance towards the degradation of organic dyes

Cu 2 O nanoparticles have been anchored on the surface of Bi 4 O 5 Br 2 hollow nanocubes, and the resulting composites have been tested for the photocatalytic degradation of organic dyes under visible light. The as-synthesized composites are composed of Bi 4 O 5 Br 2 in the monoclinic phase and Cu 2 O in the cubic phase, both of which respond to visible light. The optimized Bi 4 O 5 Br 2 /Cu 2 O composite can decompose 95% of initial RhB and 99% of initial MB after 80 min illumination, which is significantly higher than those obtained on bare Bi 4 O 5 Br 2 and Cu 2 O photocatalysts. The charge transfer and separation dynamics in the Bi 4 O 5 Br 2 /Cu 2 O composite photocatalysts under excitation are proved to be superior compared to bare Bi 4 O 5 Br 2 in the electrochemical measurements. The enhanced performance of the Bi 4 O 5 Br 2 /Cu 2 O composite is attributed to the p-n junction formed between Bi 4 O 5 Br 2 and Cu 2 O, which inhibits charge recombination and facilitates effective charge separation. Lastly, it has been proved in the scavenger tests that superoxide radical is the most crucial active species in the photocatalytic degradation of RhB.

Quantum Efficiency Study and Reflectivity Enhancement of Au/Bi Absorbers

X-ray absorbers of the X-ray Integral Field Unit (X-IFU) microcalorimeters are required to provide high quantum efficiency (QE) for incident X-rays and high reflectivity to longer wavelength radiation. The thickness of the electroplated Au and Bi layers of the absorber is tuned to provide the desired pixel heat capacity and the QE. To calculate the QE precisely, in addition to filling factor, we have included the effects of surface roughness, edge profile of the absorbers and the effects of the different angles of incidence of the incoming X-rays from the X-IFU optic. Based on this analysis, it is found that thickness of the Bi layer needs to be adjusted by 4.3% to achieve the X-IFU QE requirements. To enhance the absorber’s rejection of low-energy radiation, a second thin layer of Au is sputter-deposited on top of the Bi layer. Optical measurements in the wavelength range 0.3–20 μm show a significant increase in reflectivity compared to a bare Bi layer.

Metal-support interaction enhanced electrochemical reduction of CO2 to formate between graphene and Bi nanoparticles

Metal nanoparticles stabilized on a support material have been explored extensively to boost heterogeneous catalysis. Herein, the effect of metal-support interaction between bismuth (Bi) nanoparticles and reduced graphene oxide nanosheets (Gr) on the electroreduction of CO2 towards value-added formate is explored. The obtained Bi/Gr hybrid catalysts exhibit a superior catalytic activity towards electrochemical reduction of CO2, which gives the maximum faradic efficiency of 92.1 % at -0.97 V (vs. RHE) for formate generation. Particularly, the hydride shows an enhancement to the catalysts of bare Bi and physical mixture of Bi and Gr, with a high current density of 28.1 mA∙cm−2 and production rate of 0.53 mol∙cm−2 h-1 at -1.17 V (vs. RHE) for formate generation. The electrochemical analysis reveals that the metal-support interactions substantially boost CO2 electroreduction activity through modification the electronic structure and improving interfacial electron transfer between Bi and Gr. This work not only deepens an understanding of metal-support interaction effect but also sheds light on the design of high-efficiency catalysts toward CO2 electroreduction by virtue of the interactions between active metals and carbon-like support.

Mechanism of MgAl-LDH-induced enhancement in the plasmonic photocatalytic performance over bismuth nanospheres

The rapid development of industry, automobiles and manufacturing has emitted an ever-growth amount of the atmospheric gas pollutants to the atmosphere, such as nitric oxide (NO x ), sulfur oxide (SO x ), volatile organic compounds (VOC) and particle matters (PM). NO is deemed as one critical air pollutant as it is the leading origins of several environmental issues, such as the acidic rain, haze, and photochemical smog. To eliminate its environmental risk, it is highly desired to develop one effective, cost-effective and environmental-friendly technology to detect, regulate and remove them. Till now, various technologies have been developed, including the selective physical/chemical adsorption, heterogeneous catalytic reduction/oxidation and photocatalysis, to show high efficiency in separation, conversion and detoxification of NO. Among them, photocatalysis is receiving an ever-increased attention by its high efficiency, low cost and green feature (this technology enables the direct utilization of solar light to trigger the generation of highly active oxidative free radicals for pollutant degradation and mineralization). In the development of photocatalytic technology, the core part is the design and synthesis of highly effective and durable photocatalyst. Plasmonic metal with a unique localized surface plasmon resonance (LSPR) feature have now emerged as one appealing class of photocatalysts with wide applications in environmental remediation and energy conversion. In the plasmonic metal-directed photocatalysis, the surface electrons of plasmonic metal oscillate resonated with the incident photon, giving rise to the generation of hot carriers for catalytic redox reactions. However, most of the current LSPR-directed photocatalysis is limited to the noble metal (Au and Ag). Very recently, the earth-abundant bismuth metal (Bi) was confirmed to show a unique LSPR feature in visible light region, and more importantly, can serve as a direct plasmonic photocatalyst in ppb-level NO removal from a gas flow under UV illumination. However, bare Bi particles do not show enough redox capability as the hot carriers produced via LSPR in Bi metal cannot travel over distances longer than tens of nanometers. In this study, we attempt to introduce the MgAl-layered double hydroxide (MgAl-LDH) to intensify photocatalytic efficiency of the Bi metal. A facile liquid-phase ultrasound-assisted assembly approach was firstly used to synthesize the Bi@MgAl-LDH nanocomposite, in which Bi-NPs are uniformly supported on MgAl-LDH nanosheets. This composite can efficiently and steadily photocatalyze the removal of ppb-level NO from a continuous air flow under ultraviolet light irradiation via the plasmonic effect Bi metal. The removal efficiency reaches 43% for Bi@MgAl-LDH, much higher than the bare Bi-NPs (43%). The combined study of the composite phase/morphology/structure, its optical property, band structure and ESR oxidation radical capture experiments reveal that MgAl-LDH cannot form a heterojunction with Bi-NPs, and the enhanced photocatalysis on Bi@MgAl-LDH originates from the abundant hydroxide ions (OH−) on the surface of MgAl-LDH. These OH− can quickly capture the photoexcited holes to generate ·OH radicals, and simultaneously promote the electron-hole separation by consuming the holes, both of which can raise the utilization efficiency of the photoexcited hot carriers and provide sufficient oxidative radicals for NO oxidation. Additionally, MgAl-LDH has a unique water molecule memory effect, and the OH− that is consumed in photocatalysis can be replenished by adsorbing water from the air, leading to a stable photocatalytic performance. The reaction pathway study of the photocatalytic NO oxidation over Bi@MgAl-LDH by in-situ DRIFTS reveals that NO is completely mineralized into nitrate. The present work should contribute to a deeper understanding of the photocatalytic mechanism and then the design of robust catalysts for air purification.

Bi Nanoparticles Anchored in N-Doped Porous Carbon as Anode of High Energy Density Lithium Ion Battery

A novel bismuth–carbon composite, in which bismuth nanoparticles were anchored in a nitrogen-doped carbon matrix (Bi@NC), is proposed as anode for high volumetric energy density lithium ion batteries (LIBs). Bi@NC composite was synthesized via carbonization of Zn-containing zeolitic imidazolate (ZIF-8) and replacement of Zn with Bi, resulting in the N-doped carbon that was hierarchically porous and anchored with Bi nanoparticles. The matrix provides a highly electronic conductive network that facilitates the lithiation/delithiation of Bi. Additionally, it restrains aggregation of Bi nanoparticles and serves as a buffer layer to alleviate the mechanical strain of Bi nanoparticles upon Li insertion/extraction. With these contributions, Bi@NC exhibits excellent cycling stability and rate capacity compared to bare Bi nanoparticles or their simple composites with carbon. This study provides a new approach for fabricating high volumetric energy density LIBs.

Pyrophosphate effect on the photocatalytic degradation of phenol over bare and Pt-deposited Bi2WO6

Pyrophosphate-mediated hole transfer from Pt/Bi2WO6to phenol can accelerate phenol degradation in aqueous solutions.

Bi metal sphere/graphene oxide nanohybrids with enhanced direct plasmonic photocatalysis

The Bi metal sphere/graphene oxide (Bi/GO) nanohybrids were firstly synthesized by a simple one-step solvothermal method. Compared with bare Bi spheres, the Bi/GO nanohybrids exhibited highly enhanced and stable direct plasmonic photocatalytic activity towards removal of NO, primarily resulting from the assistance of graphene oxide. The Bi spheres act as antenna for incident light absorption via the SPR effect. The graphene oxide is regarded as an acceptor and transporter of the photogenerated electrons and provides the binding sites for Bi deposition. Furthermore, the related growth and plasmonic photocatalytic mechanisms of Bi/GO nanohybrids system were proposed reasonably. The agreements of the simulation results and experimental study where Bi spheres and Bi/GO nanohybrids were applied as direct plasmonic photocatalysts were discussed for the first time. This work could not only provide new insights into the understanding of the plasmonic effects of Bi spheres but also pave a new way to design direct plasmonic photocatalysts with superior performance.

Large improvement of photo-response of CuPc sensitized Bi2WO6 with enhanced photocatalytic activity

In order to harvest the solar energy more efficiently, a novel photocatalyst was designed by introducing an organic dye sensitizer, copper phthalocyanine (CuPc), into an inorganic semiconductor Bi(2)WO(6). This composite photocatalyst exhibited an improved photo-response in the whole visible spectrum and even the near infrared region. Under a red LED (λ = 620 nm) irradiation, the CuPc/Bi(2)WO(6)/FTO electrode showed photocurrent response. The photo-degradation of RhB and phenol under simulated solar light demonstrated that the CuPc-Bi(2)WO(6) composite exhibited much higher photocatalytic activity than bare Bi(2)WO(6). Moreover, the composite photocatalyst also showed photo-activity under a red LED (λ = 620 nm) irradiation, further testifying the sensitization effect of CuPc. This study provides a new strategy to increase the utilization rate of solar energy substantially.

Photocatalytic activity of zinc modified Bi 2O 3

The surface of α-Bi 2O 3 was modified by either impregnating Zn acetate or coating with a sol–gel containing Zn hydroxide. The surface modified Bi 2O 3 powders were evaluated by UV–Visible spectroscopy, Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and surface area analysis (BET). The photocatalytic performances were evaluated for the degradation of phenol, methylene blue and methyl orange. The variations in photocatalytic activity were correlated with morphology change. The presence of ZnO does not significantly prevent the progressive formation of photocatalytically inactive (BiO) 2CO 3, while the dye decolourization capability of nanocomposite is significantly preserved with respect to that of bare Bi 2O 3.

Influence of heat treatment on the properties of Bi 1.8Pb 0.2Sr 2Ca 2Cu 3O x ceramics and Ag-sheathed tapes

Optimization of a heat treatment temperature is applied to bare Bi 1.8Pb 0.2Sr 2Ca 2Cu 3O x ceramics as well as to Ag-sheathed tapes prepared by the powder in the tube method. We discuss structural differences observed by SEM and the phase content and FWHM of rocking curves obtained by X-ray diffraction. Further, we compare the superconducting transition temperature of short samples measured by a.c. susceptibility and the critical current anisotropy measured by the four probe method. The effect of the Ag-envelope as oxygen barrier is shown comparing the differences in the width of transition temperature. The difference in the angular dependence of critical currents reflects not only the texture but also the path in which the current is flowing.

X-ray emission from very-heavy H- and He-like ions in collisions with gaseous and solid targets

Projectile X-ray emission and charge-exchange processes are studied for bare and one-electron Bi, Pb, and U ions in collisions with gaseous and solid targets at relativistic energies. The experimental data for both the total and subshell differential cross sections are discussed and compared with theoretical predictions. Moreover, the experiments were extended to atomic structure studies. The result for the groundstate Lamb-shift for hydrogenic uranium is presented, which compares very well with theoretical prediction.