Bi Doping Research Articles

Efficient photoelectrocatalytic reduction of CO2 to formate via Bi-doped InOCl nanosheets

Converting CO2 into useful substances is an important approach to address the challenge of reducing CO2 emissions and combating climate change. Compared with the traditional process, photoelectrocatalytic CO2 reduction has great potential to solve the problem of CO2 emission. In this work, Bi-doped InOCl cathode catalysts were prepared by a two-step calcination process, and they demonstrated efficient catalytic activity for the reduction of CO2 to formate. The inclusion of bismuth (Bi) in InOCl resulted in improved catalytic performance compared to the native InOCl catalyst. Specifically, the highest formate selectivity can be observed at −0.9 V vs RHE with a Faraday efficiency of 89.9% and the product rate of 101.41 μmol h–1cm–2 when the Bi doping amount is 5%, representing approximately 2 and 3 times the values obtained with native InOCl, respectively. The experimental results indicate that Bi doping promotes the formation of {001} crystalline surfaces in InOCl, while increasing the specific surface area and the availability of more active sites for CO2 reduction. This work holds significant potential for further advancements in the field of photoelectrocatalytic reduction of CO2.

Dual-Photosensitizer Synergy Empowers Ambient Light Photoactivation of Indium Oxide for High-Performance NO2 Sensing.

Light-activated chemiresistors offer a powerful approach to achieving lower-temperature gas sensing with unprecedented sensitivities. However, an incomplete understanding of how photoexcited charge carriers enhance sensitivity obstructs the rational design of high-performance sensors, impeding the practical utilization under commonly accessible light sources instead of ultravioletor higher-energy sources. Here, a rational approach is presented to modulate the electronic properties of the parent metal oxide phase, exemplified by this model system of Bi-doped In2O3 nanofibers decorated with Au nanoparticles (NPs) that exhibit superior NO2 sensing performance. Bi doping introduces mid-gap energy levels into In2O3, promoting photoactivation even under visible blue light. Additionally, green-absorbing plasmonic Au NPs facilitate electron transfer across the heterojunction, extending the photoactive region toward the green light. It is revealed that the direct involvement of photogenerated charge carriers in gas adsorption and desorption processes is pivotal for enhancing gas sensing performance. Owing to the synergistic interplay between the Bi dopants and the Au NPs, the Au-BixIn2-xO3 (x=0.04) sensing layers attain impressive response values (Rg/Ra=104 at 0.6ppm NO2) under green light illumination and demonstrate practical viability through evaluation under simulated mixed-light conditions, all of which significantly outperforms previously reported visible light-activated NO2 sensors.

High thermoelectric performance of GeTe-MnTe alloy driven by spin degree of freedom

GeTe has been known as an excellent thermoelectrics, whereas its realistically application is limited by its structural phase transition near 700 K. Here, we show that the temperature of phase transition can be suppressed below 300 K by alloying 35% MnTe. The GeTe-MnTe alloy exhibits the much different transport properties from GeTe. Its room-temperature Seebeck coefficient is close to that of optimized GeTe, while its carrier concentration is one order higher. The increase of Seebeck coefficient of GeTe-MnTe is found to be accompanied with the decrease of magnetic susceptibility, while GeTe shows the opposite trend. By optimizing the carrier concentration with Bi doping and Bi/Sb co-doping, the peak figure of merit of GeTe-MnTe reaches 1.46 at 823 K. Our study reveals that GeTe-MnTe alloy is a novel and promising thermoelectric material.

Realizing High Thermoelectric Performance in GeTe‐Based Supersaturated Solid Solutions

AbstractAs a highly promising thermoelectric material in the mid‐temperature region, pristine GeTe shows deteriorated thermoelectric properties due to the low Seebeck coefficient and the intrinsic high thermal conductivity. Herein, it is discovered that the introduction of strongly correlated d, f electrons by alloying rare‐earth atoms at Ge sites will increase the band effective mass and promote band convergency, which can largely improve the electric transport property. Moreover, the heavy atoms (Pb, Bi) doping induces optical phonon softening and the avoided crossing between acoustic and optical phonon branches, decelerating both optical and acoustic phonon velocities. The modulated composition wave from the fluctuated multi‐component distribution introduces a complicated hierarchical structure including point defects and nanoprecipitates, which provides all‐scale scattering sources for heat‐carrying phonons and results in low lattice thermal conductivity. Consequently, a high zT of 2.4 at 800 K can be obtained in the Ge0.86Pb0.09Bi0.03Ce0.005Te sample due to the combination of strong correlation for d, f electrons and the full‐spectrum scattering for phonons. This work provides an effective strategy to increase the thermoelectric performance of IV–VI compounds by combining the modulated band structure and the softening phonon dispersion.

Unlocking the potential of Cu3SbSe3: Ultralow thermal conductivity and enhanced thermoelectric performance

Cu3SbSe3, with its ultralow thermal conductivity and Earth-abundant elements, has emerged as a promising thermoelectric material. However, synthesizing its pure phase and achieving effective doping have proven to be challenging. In this study, we present our findings on the investigation of thermoelectric properties of stoichiometric and off-stoichiometric Cu3SbSe3 compositions along with various doping strategies. Our results demonstrate that samples with non-stoichiometric compositions and Bi doping further reduces the lattice thermal conductivity of 0.16 W/mK. The consistently moderate Seebeck coefficient leads to a zT value of 0.25 at 650 K across all cation-deficient samples. Furthermore, we observed that 5% Bi doping further enhances the zT value to 0.35, representing a 52% improvement over pristine Cu3SbSe3. We believe that the compositional insensitivity of zT and the enhanced performance achieved through Bi doping offer new opportunities for exploring materials with ultra-low thermal conductivity in the field of thermoelectrics.

Defect and doping properties of sliding ferroelectric γ-InSe for photovoltaic applications

Layered van der Waals (vdw) materials have been proposed as light-absorbing materials for photovoltaic applications. InSe is a layered vdw semiconductor with ultra-high carrier mobility, strong charge transfer ability, super deformability, thermoelectricity, and optoelectronic properties. Its γ phase, or γ-InSe, was greatly stabilized by doping recently, which also exhibits sliding ferroelectricity. In this study, we propose that γ-phase InSe (γ-InSe), which was recently synthesized in a high-quality bulk phase, could be an excellent light-absorbing material candidate. Based on the first-principles simulations, bulk γ-InSe is found to possess suitable bandgap, decent absorption, and low effective mass. The investigation of defect properties reveals the major defect types, defect levels, and deep-level defects that could possibly harm the efficiency, and the deep-level defects can be significantly suppressed under Se-rich conditions. In addition, γ-InSe is intrinsically n-type, which can be tuned into weak p-type by Zn and Cd doping. We also identify the defect types of Y and Bi doping, which have been experimentally used to adjust the mechanical property of γ-InSe, and find that Y interstices could play an important role in improving the stiffness of γ-InSe. Our study provides theoretical insights for photovoltaic and other photoelectronic applications based on this interesting ferroelectric layered vdw material.

Substantially low thermal conductivity and high thermoelectric figure-of-merit in Bi-doped Sr2CoRuO6 double perovskites

Transition metal oxide thermoelectric materials are interesting due to their high thermal stability, low toxicity, and low cost. Although several interesting thermoelectric oxides have been reported thus far, but reducing the lattice thermal conductivity while maintaining the good electrical conductivity to get optimum thermoelectric performance is still a challenge. In addition, many oxide systems are not well explored as yet for their potential to convert waste heat into electricity using the Seebeck effect. Herein, we report the structural and thermoelectric properties of the Sr2−xBixCoRuO6 (0 ≤ x ≤ 0.8) double perovskites. Rietveld refinement of X-ray powder diffraction data shows that the unit cell parameters increase with Bi content (x). The electrical resistivity decreases with x due to the much larger and well-connected grains in Bi containing samples. The Seebeck coefficient changes its sign from negative to positive with increasing Bi content indicating hole doping. The thermal conductivity of the samples decreases with increasing x due to the soft chemical bonding and heavy atomic mass of the doped Bi atoms. These changes in transport properties lead to a large power factor of 1.87 × 10–4 W/m·K2 and a thermoelectric figure-of-merit of 0.24 for the x = 0.8 sample at 668 K. We estimated the heat capacities from the temperature independent Dulong-Petit limit for solids for calculation of the thermal conductivities and therefore some uncertainty in the reported zT values is expected.

The Superconductivity in Bi-Doped BaFe2As2 Single Crystals.

We have successfully synthesized a series of Bi-doped BaFe2As2 high-quality single crystals for the first time. X-ray diffraction (XRD) patterns show an expansion of lattice parameter c with Bi doping, indicating a negative pressure effect. By investigating the resistivity, a Fermi liquid (FL) to non-Fermi liquid (NFL) crossover is observed from normal state to antiferromagnetic order state, accompanied by three superconducting transitions labeled as SC I, SC II and SC III, which are supposed to be induced by three superconducting realms with various Bi concentrations. Thus, we propose that the NFL behavior is closely related to the presence of superconductivity. The magnetic susceptibility measurements further speculate that the SC I and SC III phases should exhibit filamentary superconductivity while the SC II exhibits a possible bulk superconductivity of TC~7 K.

Structural and optical characterization of dilute Bi-doped GaN nanostructures grown by molecular beam epitaxy

We have carried out detailed studies on the epitaxy and characterization of dilute Bi-doped GaN nanostructures. A comprehensive investigation of Bi-doped GaN nanowires and quasi-film epitaxial growth conditions has been performed. Scanning electron microscopy studies show that lowering the GaBiN growth temperature causes gradual changes in top c-plane nanowire morphology due to the incremental incorporation of foreign Bi atoms. This trend is further substantiated by the secondary ion mass spectroscopy analysis of a multi-layer Bi-doped GaN quasi-film. However, it is also found that the amount of Bi incorporation into the GaN lattice is relatively independent of the N2 flow rate variation under the growth conditions investigated. Furthermore, room-temperature micro-Raman spectra show that there are additional peaks near 530, 650, and 729 cm−1 wave numbers in the Bi-doped GaN samples, which can primarily be attributed to Bi local vibrational modes, indicative of a small amount of Bi incorporation in the GaN lattice. Moreover, phonon calculations with density functional theory indicate that Bi replacing the N sites is the likely origin of the experimentally measured Raman modes. X-ray photoelectron spectroscopy measurements have also been obtained to deduce the electronic interaction between the Bi dopant atom and the GaN nanostructure. Such one-dimensional nanowires permit the synthesis of dislocation-free highly mismatched alloys due to strain relaxation, allowing efficient light absorption and charge carrier extraction that is relevant for solar energy harvesting and artificial photosynthesis.

A comparative study of the activation energy and shielding properties of some binary and ternary echo-friendly alloys reinforced by Bi substitutes Zn particles for radiation protection

The thermal and mechanical stability besides environmentally friendly of some low-melting binary systems dopant with third element such as Bi started to gain much attention. This study provides the synthesized, effects of rapid solidification processing (RSP) and Bi doping on the microstructural, mechanical performance and gamma radiation shielding of various lead-free binary and ternary alloys have compositions Sn-(50-x)Zn-xBi (where x = 0, 10, 20, 30 and 40 wt.%) using high cooling rate. Microstructure modifications, elastic and plastic behavior were investigated. As well as the gamma-ray shielding performance of all as-prepared melt-spun process alloys was examined experimentally using FH 40G dose rate measuring unit. Phy-X/PSD software was used to compute the μ m values across a large energy range of 0.015 MeV–15 MeV. To clearly understand the gamma radiation shielding capability of the melt-spun process alloys, different shielding parameters includes linear attenuation coefficients, LAC, mass attenuation coefficient, MAC, mean free path, MFP, half value layer (HVL) and tenth value layer (TVL) were calculated and compared to other commonly shielding materials. X-ray diffraction (XRD) analysis confirms the presence of different phases such as β-Sn, Bi, Zn as well as two IMCs Sn0.95Bi0.05 and Sn0.85Zn0.15. The morphology features of the samples using scanning electron microscopy (SEM) revealed that Bi particles dopant the matrix led to refine the microstructures as well as forming a uniform and homogeneous distribution of IMCs. It is also, reported that the increase of Bi dopant led to enhancing the Bi segregation in the matrix in addition to decreasing the crystallite size which reinforces the mechanical strength and radiation shielding properties. The elastic modulus and Vickers microhardness increase with increasing Bi additions to about 35% and 27%, respectively. The results showed that correlation between activation energy and shielding properties of as-prepared alloys. The mass and linear attenuation coefficient for all prepared samples increases as Bi increases from 10 to 40 wt.%. On the other hand, low activation energies indicate easier formation and growth of IMCs. The results also show that the Sn-10Zn-40Bi alloy has the highest mechanical and shielding attenuation properties. It may be attributed to promoting the brittleness of Bi, refinement of crystallite size, extended the solid solubility and microstructure features accompanying Bi content using rapid cooling. As a result, Sn-10Zn-40Bi alloy may be recommended as a preferable alloy for radiation shielding performance to be used for medical, industrial and nuclear waste storage fields. In the current work, an attempt has been made not only to summarize the various investigations made so far on visualizing the feasibility of alloys as radiation shielding material; but also, to provide a comparative study for further consideration to be used in other fields.

Tunable magneto-transport properties in ultra-high Bi-doped Si prepared by liquid phase epitaxy

During the past decades, excavating the novel functional materials towards CMOS-compatible spin-transport devices has been treated as one of the most urgent tasks to revolutionize the current Si-based nonmagnetic spintronics. Among various strategies, triggering the exotic physics in Si via utilizing heavy-element hyperdoping is the most straightforward way to achieve the abovementioned expectation. In this work, by using liquid phase epitaxy growth, we have achieved the highest Bi doping level in Si up to 2.0 × 1021 cm−3. The resulting Bi-hyperdoped Si layers are confirmed to be single-crystalline and epitaxially regrown without extended defects or Bi agglomerates via various microstructural analysis. The Bi-hyperdoped Si layers exhibit a metallic-like behavior with the carrier densities up to 1.55 × 1015 cm−2 and a prominent electrical activation yield around 50 %. Negative magnetoresistance due to magnetic-field suppressed weak localization at both sides of the insulator-to-metal transition is observed. Tunable magneto-transport properties are realized in ultra-high Bi doped Si epilayers by controlling the donor concentration. This provides new possibilities for designing Si devices that integrate spin-charge conversion and spin transport. This work promises to enable heavy-element hyperdoped semiconductor epilayers as novel spin-based electronics material platform via a chip-technology compatible approach.

Transformation of Ba0.7Sr0.3TiO3 from ferroelectrics to relaxor ferroelectrics by doping of Bi(Mg0.5Sn0.5) and realization of high energy storage

Transformation of Ba0.7Sr0.3TiO3 from ferroelectrics to relaxor ferroelectrics by doping of Bi(Mg0.5Sn0.5) and realization of high energy storage

Bi-doped ruthenium oxide nanocrystal for water oxidation in acidic media.

There is an urgent need to develop a cost-effective and highly efficient acidic OER catalyst to support the progress of proton exchange membrane water electrolysis technology. Ruthenium-based catalysts, which possess high activity and significantly lower cost compared to iridium-based catalysts, emerge as competitive candidates. However, their suboptimal stability constrains the wide application of RuO2. Herein, we develop ultra-small Bi0.05Ru0.95O2 nanocrystal with diameter of approximately 6.5 ± 0.1 nm for acidic OER. The Bi0.05Ru0.95O2 nanocrystal electrocatalyst exhibits a low overpotential of 203.5 mV at 10 mA cm-2 and 300+ hour stability at a high water-splitting current density of 100 mA cm-2 in 0.5 M H2SO4 with a low decay rate of 0.44 mV h-1. Density functional theory (DFT) calculation results confirmed the adsorbate evolving mechanism (AEM) occurring on Bi0.05Ru0.95O2, which prevents lattice oxygen from participating in the reaction, thus avoiding the collapse of the structure. We proved that the Bi dopants could play a crucial role in not only reducing the energy barrier of the potential-determining step, but also delivering electrons to Ru sites, thereby alleviating the over-oxidation of Ru active sites and enhancing operation durability.

Bismuth drives the morphology and piezoresistivity of lead-free (TMSO)3Sn3xBi2(1−x)I9 halide perovskite thin films

The bending strain sensitivity of (TMSO)SnI3, a monodimensional lead-free halide, is greatly increased by Bi doping. The observed piezoresistivity is fully reversible and can be explained based on the microstructural features.

Bi-doped ZnAl-layered double hydroxides with enhanced photocatalytic activity for ciprofloxacin degradation: the synergistic effect of Bi doping and oxygen vacancies

In this study, a series of Bi-ZnAl-LDHs (BZA-X) enriched with oxygen vacancies (OVs) were synthesized by doping ZnAl-LDHs with different ratios of bismuth ions.

Manipulating key intermediates and suppressing the hydrogen evolution reaction via dual roles of Bi for high-efficiency nitrate to ammonia and energy conversion.

The nitrate reduction reaction (NO3RR) is a promising technology for simultaneous treatment of NO3- wastewater and synthetic ammonia. However, the NO3RR involves multiple electron and proton transfer processes, and the ammonia selectivity and yield are highly susceptible to the evolution of key intermediate (*NO2) and the competing hydrogen evolution reaction (HER). In this study, bismuth (Bi), with a high hydrogen overpotential, is used as an inhibitor of the HER. Meanwhile, the Bi doping CoS2 (Bi-CoS2) can refine the d-band center of CoS2, which optimizes the adsorption of *NO2, reduces the accumulation of NO2- on the surface of the catalyst and then releases more active sites, thereby enhancing the NO3RR activity. This viewpoint is verified by experimental results, density functional theory (DFT) calculations and in situ Raman. Benefitting from the dual roles of Bi, Bi-CoS2 exhibits a highest NH3 Faraday Faradaic efficiency (FE) of 87.18%, an ammonia yield rate of 944.64 μg h-1 cm-1 and long-term stability at -0.2 V versus the reversible hydrogen electrode (RHE). Furthermore, an assembled Zn-NO3- battery can reach a maximum power density of 16.3 mW cm-2 and high FENH3 of 95.76%, providing a high-efficiency multifunctional system for nitrate to ammonia and energy conversion.

Morphological and structural properties of bismuth-nickel ferrite synthesized by a combined sol-gel method

In this paper, Bi x Ni1-x Fe2O4, (x = 0, 0.3, and 0.5), nanoparticles were synthesized by a sol–gel method, and the synthesized samples were calcination at 350 and 650o C for 3 h. The influence of Bi doping on morphological and structural properties was studied. The field emission scanning electron microscopy (FESEM) analysis showed all of the specimens contain a compact order of homogenous nanoparticles with a spherical form and polyhedral particles with an average size ranging from 36.305 nm to 27.554 nm at 350 and 650o C respectively. By studying the energy dispersive spectrometer analysis patterns, the existence of constituent elements, Ni, Bi, Fe, and O, was verified with a proportion very close to the stoichiometry of the chemical formula. The formation of a ferrite phase was confirmed by X-ray diffraction. An increase in the average crystallite and grain size has been observed with an increase in Bi doping. The Fourier Transform Infrared(FT-IR) studies were made in the frequency range 400-4000 cm-1 and observed two strong absorption peaks. The frequency band is found at 555 cm-1 whereas the lower frequency band is at 1338.5 cm-1. It is noticed that the two prominent absorption bands were slightly shifted towards the higher frequency side with the increase of Bi3+ ion concentration.

Improved Structural Stability of CuO Via Bi Doping for Glucose Sensing

Glucose sensing is of great importance in fields such as medical diagnostics, food industry, and environmental monitoring. Copper oxide (CuO) has shown promising results as an electrochemical sensor for glucose detection due to its high sensitivity and selectivity towards glucose molecules[1]. However, one of the key challenges is to maintain the morphology and crystal structure of CuO during long-term glucose electrooxidation. CuO is prone to phase transformation, which can lead to changes in its crystal structure and affect its electrochemical performance. Moreover, the stability of CuO can be affected by external factors such as applied potential and pH, which can induce corrosion and degradation of the CuO layer over time.In this contribution, we propose a novel approach to improve the structural stability of CuO via surface bismuth doping. The Bi-doped CuO was prepared via an ultrasonic method, generating homogenously distributed Bi atoms on the surface of CuO thin flakes. At Bi doping level between 5% to 10%, the structure of CuO retains, indicating the replacement of Cu by Bi atoms other than phase separation. The long-term electrochemical test showed <1% current loss with the 10% Bi-doped CuO while >30% current loss with the CuO (Figure 1), suggesting that Bi atoms can act as the structural stabilizer for CuO electrocatalyst. Moreover, no significant sensitivity loss (~650 mA mM−1 cm−2) was observed after Bi doping.Our results demonstrate significant improvements in the CuO sensor's stability and accuracy, which can pave the way for its practical applications in various fields. Figure 1 Amperometric response of CuO and Bi-doped CuO (percentage shows the Bi/Cu ratio) during long-term glucose electrolysis. Reference: W. Zheng, Y. Li, L. Hu, L.Y.S. Lee, Sensors & Actuators: B. Chemical 2019, 282, 187-196 Figure 1

Origin of multiferroic properties of pure and ion doped zircon- and scheelite-type DyCrO[formula omitted

Using a microscopic model we have calculated the temperature and magnetic field dependence of the magnetization, polarization and specific heat of zircon- and scheelite-type DyCrO4. The origin of the polarization in these two compounds is theoretically explained. The ferroelectricity in the scheelite-type DyCrO4 is driven by the magnetic ordering, whereas in the zircon-type DyCrO4 it is due to the CrO4 distortion-driven ferroelectric order. The magnetic field dependence of the polarization in both compounds is very different. It is discussed the magnetic field dependence of the magnetization in the scheelite- and zircon-type DyCrO4. The temperature dependence of the specific heat is also calculated which shows anomalies at the phase transition temperatures. The doping of Bi at the Dy sites leads to decrease of the magnetization and the phase transition temperature, whereas by Cu ion doping they increase.

Bi-doped CuCeO2−x nanorod catalysts for photothermal CO-PROX in H2-rich streams: Enhanced oxygen vacancy and light absorption capacity

The wide band gap of ceria limited the light absorption and photothermal conversion of copper-ceria catalyst for photothermal preferential oxidation of CO (CO-PROX). In the present work, doping Bi element was adopted to regulate the energy band and catalytic performance of CuCeO2−x nanorod catalysts for photothermal CO-PROX. Bi/CuCeO2−x nanorods were synthesized by co-precipitation hydrothermal and deposition precipitation method. The Bi/CuCeO2−x catalyst with the molar ratio of Bi/Ce 2.5% exhibited the best catalytic performance and the CO conversion reached 90% under 2.5 suns with a surface temperature of 120 °C. The doped Bi species were incorporated into the CeO2 lattice and promoted the formation of oxygen vacancy sites and the strong Cu-Ce interaction, as revealed by XRD, XPS, Raman and H2-TPR results. In addition, doping Bi reduced the band gap of ceria nanorod from 2.77 to 2.47 eV and remarkably enhanced the UV–vis light response and photogenerated carrier separation of Bi/CuCeO2−x-2.5.