Co-doped Bi Research Articles

Enhanced Thermoelectric Performance of ZrCoSb Half-Heusler Compounds by Sn–Bi Codoping

Enhanced Thermoelectric Performance of ZrCoSb Half-Heusler Compounds by Sn–Bi Codoping

Cobalt-Doped Bismuth Nanosheet Catalyst for Enhanced Electrochemical CO2 Reduction to Electrolyte-Free Formic Acid.

Electrochemical carbon dioxide (CO2) reduction reaction (CO2RR) to valuable liquid fuels, such as formic acid/formate (HCOOH/HCOO-) is a promising strategy for carbon neutrality. Enhancing CO2RR activity while retaining high selectivity is critical for commercialization. To address this, we developed metal-doped bismuth (Bi) nanosheets via a facile hydrolysis method. These doped nanosheets efficiently generated high-purity HCOOH using a porous solid electrolyte (PSE) layer. Among the evaluated metal-doped Bi catalysts, Co-doped Bi demonstrated improved CO2RR performance compared to pristine Bi, achieving ~90 % HCOO- selectivity and boosted activity with a low overpotential of ~1.0 V at a current density of 200 mA cm-2. In a solid electrolyte reactor, Co-doped Bi maintained HCOOH Faradaic efficiency of ~72 % after a 100-hour operation under a current density of 100 mA cm-2, generating 0.1 M HCOOH at 3.2 V. Density functional theory (DFT) results revealed that Co-doped Bi required a lower applied potential for HCOOH generation from CO2, due to stronger binding energy to the key intermediates OCHO* compared to pure Bi. This study shows that metal doping in Bi nanosheets modifies the chemical composition, element distribution, and morphology, improving CO2RR catalytic activity performance by tuning surface adsorption affinity and reactivity.

Optimization of energy storage and electrocaloric performance in Pb(Zr,Ti)O3 via A-Site La and Bi Co-doping

Lead-based ferroelectrics are one of the most fascinating candidates in the field of state-of-the-art electronic technology. Their intriguing properties are further enriched via the realization of morphotropic phase boundaries. Moreover, the A-site chemical substitution provides insight into the emergence of various exotic phases. Here, we employ co-doping of La3+ and Bi3+ at the A-site of Pb(Zr,Ti)O3 (PZT) ferroelectric to broaden the practical perspective of relaxor systems. Here, we emphasize that the A-site co-doping approach introduces technologically appealing amendments in the well-established temperature composition phase diagram of the PZT system. La3+ and Bi3+ doping favors the evolution of a novel response to thermal and field fluctuations. The maximum values of −ΔS are found to be ∼0.157, 0.118 and 0.176 J (kg·K)−1 for x=0.01, 0.02 and 0.03 , respectively. We employ the electrocaloric characteristics and Arrott plot as probing tools. The observation of a negative electrocaloric effect and the systematic reversal of Arrott lines, followed by a poling effect on the dielectric constant, reveals the emergence of ergodic phase as a novel phase. This further reveals that the Bi doping approach leads to the emergence of exotic characteristics in the chemically modified PZT system. The maximum observed recoverable energy for the composition for x = 0.01 is 0.0479 J cm−3 at a temperature of 388 K.

Effect of Co doping on the structure and magnetic properties of Bi0.8Ba0.2FeO3 nanoparticles

A series of Bi[Formula: see text]Ba[Formula: see text]Fe[Formula: see text]CoxO3 ([Formula: see text], 0.05, 0.10, and 0.15) samples were synthesized using the tartaric acid modified sol–gel method. The crystal structure of the prepared samples was analyzed by XRD, and the samples co-doped with Ba and Co were all rhombohedral distorted structures with the R3c space group. With an increase in the doping amount, a reduction in lattice parameters was observed along with crystallite sizes consistently being below 62[Formula: see text]nm. Mössbauer spectral analysis at room temperature reveals a good fit with two sextets and a doublet, all attributed to the Fe[Formula: see text] state. This suggests that the charge balance within the samples is maintained through the generation of oxygen vacancies in the system. The hysteresis loops of all samples revealed the weak ferromagnetic of the Co-doped Bi[Formula: see text]Ba[Formula: see text]FeO3 nanoparticles. With the increase in Co doping, the magnetic parameters such as saturation magnetization and coercive field significantly improved.

Bi co-doping for improving the ionizing radiation resistance of Er-doped fibers

Three Er-doped fibers (EDFs) with different concentrations of Bi ions doping were fabricated by atomic layer deposition combined with modified chemical vapor deposition. The radiation-induced absorption (RIA) could be dramatically weakened by co-doping Bi. Especially, the RIA of Bi/Er co-doped fiber (BEDF) at 1300 nm was 56.0% lower than that of EDF after a 1500 Gy irradiation treatment. With the increase of the irradiation dose, the fluorescence intensity and lifetime of EDF decreased continuously, while BEDF showed a trend, increasing first and then decreasing, and changed little before and after irradiation. The gain characteristics and laser threshold power of BEDF are less varied than those of EDF before and after irradiation. In addition, an irradiation simulation model of EDF and BEDF fiber was established through GEANT4 simulation toolkit and found that Bi ions are more likely to absorb gamma rays, thereby reducing the impact of irradiation on Er ions in BEDF. These results indicate that Bi co-doped EDF has significant performance improvements in radiation resistance, making it ideal for applications in harsh radiation environments.

Enhancing the Thermoelectric Power Factor of Mg2Si/MgO Composites by Ag and Bi Codoping

Enhancing the Thermoelectric Power Factor of Mg2Si/MgO Composites by Ag and Bi Codoping

Studies on Multiferroic Behavior of Y-Mn Co-Doped Bi0.9La0.1FeO3

Studies on Multiferroic Behavior of Y-Mn Co-Doped Bi0.9La0.1FeO3

(Digital Presentation) Bismuth and Transition Metal-Doped Bismuth Nanoparticles As Electrochemical Biosensors

Current non-enzymatic electrochemical biosensors rely heavily on transition metal-based nanomaterials, such as Pt, Ni, Co, and Cu, for molecule adsorption and charge transfer. Although high performance (sensitivity and selectivity) was usually demonstrated, these elements are generally toxic, making them less applicable for wearable/in vivo sensors.Two general strategies are approached to address such drawbacks: minimizing their usage without sacrificing the activity and searching for other elements with lower toxicity. In this study, we demonstrated that the overlooked bismuth nanoparticles (NPs) could be used for non-enzymatic electrochemical glucose sensing with comparable performance [1]. Using a laser ablation approach (see Figure 1A), stabilizer-free Bi NPs (~10 nm diameter) were prepared, showing amperometric sensitivity of 127 µA mM−1 cm−2. The synthesis approach also enabled the one-step surface doping of the Bi NPs, producing Ni and Co-doped Bi NPs with an atomic doping ratio of ~10%, and led to further sensitivity boost to 677 and 2326 µA mM−1 cm−2 (see Figure 1B). Kinetic analysis revealed that the oxidation of Bi(III) to Bi(V) species was the key to enabling glucose electrooxidation on Bi NPs. Such results demonstrate the vast potential of the overlooked bismuth in electrochemical biosensing. Figure 1 (A) Top: illustration of the laser ablation approach of preparing Bi and metal-doped Bi NPs; Bottom: TEM images of as-prepared Bi NPs and Co-Bi NPs; (B) Amperometric correlation between glucose concentration and the current density using Bi NPs and Co-Bi NPs as sensors. Reference: Zheng, W.; Li, Y.; Lee, L. Y. S., Bismuth and metal-doped bismuth nanoparticles produced by laser ablation for electrochemical glucose sensing, Sens. Actuators, B 2022, 357, 131334. Figure 1

Reentrant double glassy states and simultaneous presence of short- and long-range ordering in metamagnetic Co-doped Bi0·5La0·5Fe0·5Mn0·5O3 multiferroic

A study of the structural and magnetic properties of Bi0·5La0·5Fe0·45Co0·05Mn0·5O3 is presented in the article. We report the rare observations of two glassy transitions below the long-range ordering temperature along with the metamagnetic transitions at low temperatures. Frequency and DC field dependence of AC susceptibility and isothermal relaxation of remnant magnetization studies have all shown the slow spin dynamics for the compound. Interestingly, in the glass phase of the materials, metamagnetic transitions of the antiferromagnetic spins were found which indicate the coexistence of the long-range ordered phase along with the short-range ordered glassy phase. The double cluster glass phases can be comprehended, from the relaxations of the spin clusters arising from the competing magnetic interactions present in the system. Moreover, the roles of additional exchange interactions which are brought to the system by Co doping are also considered in explaining the observed double cluster glass transitions.

Enhanced Visible Photocatalytic Hydrogen Evolution of KN-Based Semiconducting Ferroelectrics via Band-Gap Engineering and High-Field Poling.

In various ferroelectric-based photovoltaic materials after low-band-gap engineering, the process by which high-field polarization induces the depolarizing electric field (Edp) to accelerate the electron-hole pair separation in the visible light photocatalytic process is still a great challenge. Herein, a series of semiconducting KN-based ferroelectric catalytic materials with narrow multi-band gaps and high-field polarization capabilities are obtained through the Ba, Ni, and Bi co-doping strategy. Stable Edp caused by high-field poling enhanced the visible photocatalytic hydrogen evolution in a 0.99KN-0.01BNB sample with a narrow band gap and optimal ferroelectricity, which can be 5.4 times higher than that of the unpoled sample. The enhanced photocatalytic hydrogen evolution rate can be attributed to the synergistic effect of the significant reduction of the band gap and the high-field-polarization-induced Edp. The change in the band position in the poled sample further reveals that high-field poling may accelerate the migration of carriers through band bending. Insights into the mechanism by which catalytic activity is enhanced through high-field-polarization-induced Edp may pave the way for further development of ferroelectric-based catalytic materials in the photocatalytic field.

Bismuth and metal-doped bismuth nanoparticles produced by laser ablation for electrochemical glucose sensing

Materials based on transition metals, such as Cu, Co, and Ni, have been intensively used as electrocatalysts for non-enzymatic electrochemical glucose sensing. However, the current trend of wearable/in vivo continuous glucose sensing has raised the need for non/low-toxic candidates. Herein, we demonstrate that the overlooked low-toxic bismuth (Bi)-based nanomaterials are suitable choices. Using a laser-ablation method, surfactant-free Bi nanoparticles (NPs) and transition metal (Ni and Co)-doped Bi NPs are obtained, achieving amperometric sensitivity values of 127, 677, and 2326 µA mM−1 cm−2, respectively. Low detection limits of 1 and 4 µM, as well as an extensive linear range of 0.001–3.5 mM, are recorded using Ni- and Co-doped Bi NPs, respectively. With competitive performance and high selectivity towards glucose sensing in both standard and serum samples, Bi-based nanomaterials are proven effective and promising candidates for future glucose sensor design beyond transition metal elements.

Enhanced activity for electrocatalytic H2 production through cooperative Pr and Bi co-doping of CeO2 in solid oxide electrolysis cells

CeO2-based catalysts as cathodes in solid oxide electrolysis cells (SOECs) have great potential for improving the storage of renewable electricity in the form of H2 via the water-splitting reaction (WSR). A key challenge to promote the WSR on CeO2 is facilitating the decomposition of stable surface hydroxides to form H2. Here, we use density functional theory to investigate the effect of Bi- and Pr- doping for the WSR on CeO2(111). We find that dopants influence the stability of hydridic H, which can be formed during the decomposition of hydroxyl to H2. By stabilizing hydridic H on Bi during the H2 formation step, Bi and Pr co-doped into ceria lower the barrier to H2 formation, enhancing the rate of WSR by 2–4 orders of magnitude compared to individually Pr-, Bi- or Gd-doped CeO2. We suggest co-doping as an effective strategy for improving the WSR in SOECs.

Evidence of room-temperature ferromagnetism in vertically aligned Bi–Co co-doped ZnO nanowires

We are the first to report Bi–Co co-doped zinc oxide nanowires (ZnO NWs) to investigate theoretically and experimentally the alignment of relative spin and the location of Bi3+ and Co2+ as the primary cause of magnetism. In the present study, we carefully performed theoretical and experimental studies of ZnO NWs prepared by the hydrothermal method and obtained exciting outcomes. The x-ray diffraction findings show that the NWs have a wurtzite crystal structure and high intensity at the (002) peak, indicating that most of the reflection comes from the hexagonal surface of the NWs. This means that the extended NWs are mainly aligned along the c-axis. The field-emission scanning electron microscope results show that, due to its anisotropic crystal existence, the grown NWs have a preferred path along the c-axis in the (001) direction. X-ray photoelectron spectroscopy studies established the presence of both Bi and Co in all the Bi–Co co-doped samples. They also showed that OH− groups exist on the surface of ZnO NWs, and increasing Co content tends to increase the O-deficient region in the ZnO matrix. UV–vis analysis showed a decreased optical band gap upon doping, which is probably due to the sp-d exchange interaction between localized d-electron bands of dopants. Optical studies also suggested that the doping induced an increase in electron concentration. The Raman results indicate that the ZnO NWs contain crystallization with few defects after Bi–Co-doping. From the magnetic studies, it was observed that the ferromagnetism probably originates from the defect-rich regions, i.e. NW surface and Bi and Co sit at ZnO’s substitutional site. In contrast, the core of the NWs remains under the other magnetic state. Our density functional theory studies are in line with the experimental results.

Optimized Mn and Bi co-doping in SnTe based thermoelectric material: A case of band engineering and density of states tuning

Tin telluride (SnTe) overwhelmingly continues to be studied owing to its promising thermoelectric properties, tunable electronic structure, and its potential as an alternate to toxic lead telluride (PbTe) based materials. In this research, we engineer the electronic properties of SnTe by co-doping Mn and Bi below their individual solubility limit. The First principles density functional theory studies reveal that both Bi and Mn introduce resonance states, thereby increasing the density of states near the Fermi level leading to enhanced Seebeck coefficient. This unique combination of using two resonant dopants to introduce flatter bands is effective in achieving higher performance at lower temperatures manifesting into a large Seebeck value of ∼91 μV/K at room temperature in the present case. Both elements optimally co-doped results in a very high power factor value of ∼24.3 μW/cmK2 at 773 K when compared to other high performance SnTe based materials. A zT of ∼0.93 at 773 K is achieved by tuning the proportion of the co-dopants Mn and Bi in SnTe. The hardness value of pristine SnTe was also seen to increase after doping. As a result, synergistic optimized doping proves to be a suitable means for obtaining thermoelectric materials of superior characteristics without the need for heavy doping.

Improvement of thermoelectric properties of SnTe by Mn Bi codoping

SnTe is an attracted lead-free thermoelectric material, but the thermoelectric performance is severely limited by the high hole concentration, undesirable valence band structure and high thermal conductivity. In this work, we study the multiple effects of MnBi codoping in SnTe to synergistically improve the overall power factor and ZT values. It is found that the MnBi codoping effectively reduces the hole concentration to an optimal range. As expected, Mn and Bi doping obviously decreases the energy separation between the two valence band maxima, enabling pronounced band convergence and improved Seebeck coefficient. Moreover, MnBi codoping introduces various phonon scattering centers to scatter a wide spectrum of phonons for a suppressed lattice thermal conductivity of 0.67 W m−1 K−1 at 850 K. The synergy of these effects yields a peak ZT of 1.3 at 850 K and an average ZT of 0.68 (300–850 K) in Sn0.90Mn0.07Bi0.03Te, suggesting SnTe-based material a promising candidate for medium-temperature thermoelectric applications.

Dielectric temperature stability of Nb-modified Bi0.5(Na0.78K0.22)0.5TiO3 lead-free ceramics

In this study, the phase structure, microstructure and dielectric properties of Bi0.5(Na0.78K0.22)0.5(Ti1-xNbx)O3 lead-free ceramics prepared by traditional solid phase sintering method were studied. The second phase pyrochlore bismuth titanate (Bi2Ti2O7) was produced in the system after introduction of Nb5+. The dielectric constant of the sample (x = 0.03) sintered at 1130 °C at room temperature reached a maximum of 1841, and the dielectric loss was 0.045 minimum. It had been found that the K+ and Nb5+ co-doped Bi0.5Na0.5TiO3 (BNT) lead-free ceramics exhibited outstanding dielectric-temperature stability within 100–400 °C with Tcc ≤±15%. Result of this research provides a valuable reference for application of BNT based capacitors in high temperature field.

Efficient interlayer charge release for high-performance layered thermoelectrics.

Many layered superlattice materials intrinsically possess large Seebeck coefficient and low lattice thermal conductivity, but poor electrical conductivity because of the interlayer transport barrier for charges, which has become a stumbling block for achieving high thermoelectric performance. Herein, taking BiCuSeO superlattice as an example, it is demonstrated that efficient interlayer charge release can increase carrier concentration, thereby activating multiple Fermi pockets through Bi/Cu dual vacancies and Pb codoping. Experimental results reveal that the extrinsic charges, which are introduced by Pb and initially trapped in the charge-reservoir [Bi2O2]2+ sublayers, are effectively released into [Cu2Se2]2− sublayers via the channels bridged by Bi/Cu dual vacancies. This efficient interlayer charge release endows dual-vacancy- and Pb-codoped BiCuSeO with increased carrier concentration and electrical conductivity. Moreover, with increasing carrier concentration, the Fermi level is pushed down, activating multiple converged valence bands, which helps to maintain a relatively high Seebeck coefficient and yield an enhanced power factor. As a result, a high ZT value of ∼1.4 is achieved at 823 K in codoped Bi0.90Pb0.06Cu0.96SeO, which is superior to that of pristine BiCuSeO and solely doped samples. The present findings provide prospective insights into the exploration of high-performance thermoelectric materials and the underlying transport physics.

Novel Tm3+/Yb3+–co-doped Bi2MoO6: Synthesis, characterization, and enhanced photocatalytic activity under visible-light irradiation

Abstract

Effect of Sr and Mn co-doping on multiferroic properties of BiFeO3 via sol-gel chemical process

In this contribution, Sr and Mn co-doped Bi0.90Sr0.10FexMn1 − xO3 (X = 0, 5%, 10%, 15%) nanoparticles were prepared by sol-gel (chemical route) method to observe the dominance of co-substitution on their grain size, morphology, UV-vis absorbance and magnetic properties. Co-substitution of Sr and Mn in BiFeO3, leads to structural transformation from rhombohedral (R3c) to orthorhombic (Pn21a). Field emission scanning electron microscope reveals that upon Mn doping nanoparticles become finer. The M-H loops depict that at 15 mol. % Mn doping the saturation magnetization (Ms) is enhanced significantly. Moreover, the synthesized nanoparticles absorb visible light and their band gaps reduce substantially.

Low Thermal Conductivity and High Thermoelectric Performance in Sb and Bi Codoped GeTe: Complementary Effect of Band Convergence and Nanostructuring

Complementary and beneficial effects of Sb and Bi codoping in GeTe are shown to generate high thermoelectric figure of merit, zT, of 1.8 at 725 K in Ge1-x-yBixSbyTe samples. Sb and Bi codoping in GeTe facilitates the valence band convergence enhancing the Seebeck coefficient as supported by density functional theoretical (DFT) calculations. Further, Sb and Bi codoping in GeTe releases the rhombohedral strain and increases its tendency to be cubic in structure, which ultimately enhances the valence band degeneracy. At the same time, Bi forms nanoprecipitates of size ∼5–20 nm in GeTe matrix and Sb doping increases solid solution point defects greatly, which altogether scatter low-to mid wavelength phonons and result in reduced lattice thermal conductivity down to 0.5 W/mK in the 300–750 K range.