Doping Elements Research Articles

Elemental doping tailoring photocatalytic hydrogen evolution of InP/ZnSeS/ZnS quantum dots

Photocatalytic water splitting for hydrogen production has garnered considerable attention as an effective method to alleviate energy shortages. In comparison to cadmium-based quantum dots (QDs) photocatalysts, InP QDs possess a smaller bandgap, larger exciton radius, broader absorption range, and are environmentally friendly. Although InP/ZnS core/shell QDs exhibit immense potential in photocatalysis, they suffer from rapid electron-hole recombination owing to interface defects and lattice mismatch. To address these issues, this study introduces an intermediate ZnSeS shell to reduce defects and tailor QD redox properties through transition metals (manganese and copper) doping. The characterization of QDs was performed from various perspectives, including morphology, element distribution, band structure, and charge transport efficiency. Notably, the photoelectrochemical properties of doped QDs were superior to those of the undoped QDs, while Mn-doped QDs showed inferior catalytic performance compared to the undoped ones. The mechanism of different photoelectrochemical and photocatalytic performances has been studied more intensely. The Mn-doped QDs undergo a process where Mn4+ is converted to Mn2+, consuming electrons in competition with the photocatalytic hydrogen evolution process. Conversely, InP/ZnSeS:Cu/ZnS QDs introduced an additional energy level into the original band structure, capturing some holes and slowing down the electron-hole recombination, thereby providing positive feedback for photocatalytic hydrogen production. Profiting from both the synergies of energy level structure and doping metal state, effective electron-hole separation, and rapid electron transfer to the surface of Cu-doped QDs accomplish the efficient hydrogen generation. The present study offers more possibilities for exploiting the required photocatalytic performance of QD catalysts via elemental doping.

Aloe vera-assisted biogenic synthesis of tunable magnesium oxide nanoparticles for enhanced photocatalytic and antibacterial applications

In this study, magnesium oxide (MgO) nanoparticles (NPs) tuned via doping with transition metal ions, Co2+/Cu2+/Zn2+ have been synthesized biologically using Aloe vera leaf extract as an encapsulating agent. These pure and doped MgO NPs have been characterized by using various physico-chemical characterization techniques. X-ray diffraction (XRD) analysis confirms the formation of face-centered cubic structures of pure and doped MgO NPs with their average crystallite sizes ranging from 8.11-17.83 nm. X-ray photoelectron spectroscopic (XPS) analysis confirmed the presence of doped element in their +2 oxidation state. UV-Visible spectral analysis revealed a significant reduction in band gap energies in nano-dimensions which further gets modified upon doping (1.76 − 4.9 eV). Our findings also demonstrated the engagement of phytochemicals as capping agents in Fourier transform infrared (FTIR) examination. Scanning electron microscopic (SEM) and Transmission electron microscopic (TEM) analysis provided insights into the morphologies and particle sizes. Elemental analysis by Energy dispersive X-ray (EDX) confirms the presence of Co, Cu, and Zn elements in doped MgO NPs. The photocatalytic degradation of dyes has confirmed that Co and Cu doping substantially enhance the photocatalytic activity compared to both undoped and Zn-doped MgO NPs. Furthermore, these nanoparticles demonstrate superior efficiency in degrading the cationic dye Malachite green (MG) compared to the anionic dye Methyl orange (MO). Regarding their antibacterial properties, only Cu doping induces a notable antibacterial effect in MgO NPs, particularly against gram-positive bacteria. Additionally, these nanoparticles exhibit substantial antioxidant activities. These tailored MgO nanoparticles exhibit potential for applications in wastewater treatment.

Highly flexible and temperature-tolerant phase change devices for dual-band camouflage

Here, we have developed a more temperature-tolerant emitter with a gradient emittance, which can enable adaptation to changing environmental conditions. Such a thermal emitter is mainly constructed by multilayered films composed of nitrogen (N)-doped Ge2Sb2Te5 (N-GST) and an underlying metal film. The proposed device not only possesses special wavelength selectivity in the middle infrared range but can also dynamically adjust average emissivity (from 0.13 to 0.83) through the degree of crystallization. Besides, N doping can elevate the phase transition temperature of GST and enhance its thermal resistance, which renders it particularly well-suited for applications in higher temperature environments than pure GST. This emitter also shows strong adhesion capability and high flexibility against bending, enabling more practical and widespread situations. By using a multi-layer structure, we combined the more temperature-tolerant and dynamically modulating N-GST emitter with an optical thin film, successfully achieving dual camouflage for both infrared and visible light. The element doping technology and multi-layer stacking approach presented in this research will provide valuable insight for the development of dynamic emissive materials in multi-spectral camouflage scenarios.

Effects of oxygen content, Mn/S ratio, Cu content, hot-rolling, and annealing on morphology/distribution of MnS inclusions and microstructure/mechanical properties of free-cutting stainless steel

Free-cutting steel, renowned for its exceptional machinability, is susceptible to the impact of manganese sulfide (MnS) and other non-metallic inclusions on the cutting performance and mechanical properties. The composition, morphology, and distribution of these inclusions are influenced by the total oxygen content and doping elements in free-cutting steel. This study focused on three S303 free-cutting steels with different S, Mn, and Cu contents, and the as-received samples were subjected to deoxidation and oxidation remelting, respectively, using a high-vacuum arc melting furnace to control the oxygen content. Thermo-Calc simulations were employed to predict the phases and phase proportions under different processing conditions and to compare with measurements. While the oxygen content was found to subtly affect the distribution and morphology of MnS inclusions, the Mn/S ratio notably affected the size and quantity of MnS inclusions, consequently impacting the mechanical properties of the steel. Higher Cu contents resulted in Cu segregates in the matrix but did not exist in MnS or form CuO; however, it significantly reduced strain hardening. Comparisons between hot-rolled and annealed samples revealed that the most significant changes in mechanical properties resulted from the release of residual stresses. In nanoindentation tests, it was observed that the hardness of MnS inclusion was influenced mainly by residual stresses not doping elements.

Doping Effects on Ternary Cathode Materials for Lithium-Ion Batteries: A Review.

The ongoing advancements in lithium-ion battery technology are pivotal in propelling the performance of modern electronic devices and electric vehicles. Amongst various components, the cathode material significantly influences the battery performance, such as the specific capacity, capacity retention and the rate performance. Ternary cathode materials, composed of nickel, manganese, and cobalt (NCM), offer a balanced combination of these traits. Recent developments focus on elemental doping, which involves substituting a fraction of NCM constituent ions with alternative cations such as aluminum, titanium, or magnesium. This strategic substitution aims to enhance structural stability, increase capacity retention, and improve resistance to thermal runaway. Doped ternary materials have shown promising results, with improvements in cycle life and operational safety. However, the quest for optimal doping elements and concentrations persists to maximize performance while minimizing cost and environmental impact, ensuring the progression towards high-energy-density, durable, and safe battery technologies.

Mn doping as a simple strategy for improving energy storage in BaBi4Ti4O15 thin films

To obtain high energy storage density in ferroelectric films, polarization and breakdown field Eb are two crucial factors. The inversely coupled relationship between polarization and Eb is commonly observed and it remains a challenge to realize high Eb without deteriorating polarization. Selecting a suitable element doping should largely enhance the Eb since of the optimization of microstructures as well as the decrease in defects, meanwhile the doping should induce extra polarization contribution from lattice distortion. In this work, we reported that Eb can be largely enhanced via Mn doping in BaBi4Ti4O15 thin films due to grain refining, densification, and oxygen vacancy reduction. Interestingly, the polarization is not deteriorated since of the Mn doping effect induced extra polarization from the lattice distortion. Consequently, an ultrahigh energy storage density of 96 J/cm3 with a high efficiency of 76.6% was achieved in BaBi4Ti3.95Mn0.05O15 thin films with excellent stability and reliability. This work will provide a simple and effective route to improve the energy storage in dielectric capacitors.

Comprehensive Understanding of Elemental Doping and Substitution of Ni‐Rich Cathode Materials for Lithium‐Ion Batteries via In Situ Operando Analyses

This review explores the challenges and advancements in the development of high‐energy lithium‐ion batteries (LIBs), particularly focusing on the electrochemical and structural stability of Ni‐rich cathode materials. Despite their potential to increase the energy density of LIBs, these cathode materials encounter issues such as irreversible phase transitions and structural degradation during cycling, which ultimately affect their electrochemical performance. Elemental doping/substitution has emerged as promising strategies to address these challenges. However, the precise mechanisms underlying their performance enhancement remain unclear. The objective is to elucidate the complex reaction mechanisms triggered by doping and substitution in Ni‐rich cathode materials by employing in situ operando analyses to uncover their effects on electrochemical behavior and structural integrity during cycling. This comprehensive investigation aims to clarify the roles of elemental dopants or substituents in the crystal structures of Ni‐rich cathode materials, thereby offering valuable insights for the structural engineering of cathode materials in high‐energy LIBs. By elucidating these intricate mechanisms, this review provides a practical roadmap for future research and significantly contributes to LIB technology by guiding material design and optimization strategies in the development of advanced LIBs.

Facile Synthesis of Oxygen-Doped g-C3N4 Mesoporous Nanosheets for Significant Enhancement of Photocatalytic Hydrogen Evolution Performance.

In this work, oxygen-doped g-C3N4 mesoporous nanosheets (O-CNS) were synthesized via a facile recrystallization method with the assistance of H2O2. The crystal phase, chemical composition, morphological structure, optical property, electronic structure and electrochemical property of the prepared O-CNS samples were well investigated. The morphological observation combined with the nitrogen adsorption-desorption results demonstrated that the prepared O-CNS samples possessed nanosheet-like morphology with a porous structure. Doping O into g-C3N4 resulted in the augmentation of the specific surface area, which could provide more active sites for photocatalytic reactions. Simultaneously, the visible light absorption capacity of O-CNS samples was boosted owing to the regulation of O doping. The built energy level induced by the O doping could accelerate the migration rate of photoinduced carriers, and the porous structure was most likely to speed up the release of hydrogen during the photocatalytic hydrogen process. Resultantly, the photocatalytic hydrogen production rate of the optimized oxygen-doped g-C3N4 nanosheets reached up to 2012.9 μmol·h-1·g-1, which was 13.4 times higher than that of bulk g-C3N4. Thus, the significantly improved photocatalytic behavior was imputed to the synergistic effect of the porous structure, the increase in active sites, and the enhancement of visible light absorption and charge separation efficiency. Our research highlights that the synergistic effect caused by element doping will make a great contribution to the remarkable improvement in photocatalytic activity, providing a new inspiration for the construction of novel catalysts.

Construction of an Electrochemical Molecularly Imprinted Sensor Based on L-carnitine Doped Polypyrrole for Vibrio Parahaemolyticus Detection

This study addresses the pressing need for rapid detection of pathogenic microorganisms by designing and fabricating an L-carnitine-doped polypyrrole (L-CN/PPy) electrochemical molecularly imprinted sensor, with Vibrio parahaemolyticus as the model target. Employing L-carnitine as a dual-functional dopant and auxiliary recognition element in the electropolymerization process, the sensor not only enhances the conductive properties of polypyrrole but also significantly improves its specific recognition capability towards the target bacteria. The sensor preparation encompasses the electrochemical polymerization of L-CN/PPy composite material, immobilization and elution of template bacteria, followed by bacterial recognition and detection steps. Through systematic optimization of L-CN concentration, polymerization conditions, eluent composition, elution time, and operational parameters, the sensor's performance is maximized. Experimental results confirm the sensor's efficacy in rapidly completing template bacteria elution within just 30 minutes and achieving efficient recognition of Vibrio parahaemolyticus within 20 minutes, demonstrating high sensitivity and selectivity. Moreover, the straightforward and rapid construction method of the sensor introduces a novel technological strategy for practical microbial detection applications, highlighting extensive application prospects.

A comprehensive investigation of alloying elements on site preferences, elastic properties and electronic structure of Mg17Al12 by first-principles calculations

The effect of elemental doping on the site preference, elastic properties and electronic structure of Mg17Al12 has been systematically investigated by first-principles calculations. And twenty-seven elements (Li, Na, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Sr, Y, Zr, Ag, Cd, In, Sn, Sb, Pb, Bi and La) are considered in this study. The calculations of substitution formation energies indicate that the alkali metal (Li), alkaline earth (Ca, Sr) and rare earth (Sc, Y, La) group elements and Ti, Zr favor to occupy Mg sites, and transition group (Fe, Co, Ni, Cu, Ag, Zn, Cd) elements and Ga, Ge, Sn, Sb prefer to occupy Al site, while Na, K, V, Cr, Mn, In, Pb and Bi are unstable in Mg17Al12 phase. Meanwhile, the results of phonon dispersion curves for the preferentially doped systems show that all doped structures are dynamically stable except for Sr, La and Sn doped systems. The elastic constants indicate that all preferential doping models are mechanically stable, and solute atoms with high bulk modulus lead to an increase in the bulk modulus of Mg17Al12 phase. Simultaneously, the calculated shear modulus/bulk modulus ratio (G/B), Poisson's ratio (v) and Cauchy's pressure (C‾12‐C‾44) indicate that the ductility of doped systems is better than Mg17Al12 alloy. All structures are elastic anisotropic, while the doping of Fe, Co and Ni reduces the degree of anisotropy of Mg17Al12 phase. Furthermore, the electronic structures show a strong hybridization between the p-orbitals of Mg and Al and the d-orbitals of alkaline earth, rare earth and Zr elements, resulting in higher structural stability. Finally, the adsorption behavior of O atom on Mg17Al12(110) surface and the structural stability, lattice constants, and elastic modulus of Mg34Al24-xZnx random solid solution alloys are investigated.

Effects of substituted chalcogen atoms on excited state proton transfer reaction for 2,5‐bis(benzoxazole‐2‐yl)‐thiophene‐3,4‐diol derivatives: A theoretical study

AbstractMotivated by the captivating allure of exquisitely regulated characteristics exhibited by 2‐(2‐hydroxyphenyl)‐benzoxazole and its derivatives in the domains of photochemistry and photophysics, our current endeavor primarily focuses on delving into the intricacies of photo‐induced excited state reactions for derivatives of 2,5‐bis(benzoxazol‐2‐yl)‐thiophene‐3,4‐diol (BTD). Given the profound impact of chalcogen element doping, our primary focus lies in investigating the excited state behaviors of BTD‐O, BTD‐S, and BTD‐Se fluorophores. Through simulations encompassing variations in geometry and vertical excitation charge reorganization, we unveil atomic‐electronegativity‐dependent hydrogen bonding interactions and photoexcitation‐induced charge recombination that can significantly augment the intramolecular double proton transfer (ESDPT) reaction in the excited state for BTD‐O, BTD‐S, and BTD‐Se fluorophores. By constructing potential energy surfaces and identifying transition state forms, we elucidate the ultrafast stepwise ESDPT mechanism facilitated by the low potential barriers. Moreover, we rigorously validate the chalcogen atomic electronegativity‐driven regulation of the stepwise ESDPT mechanism. We sincerely anticipate that manipulating solvent polarity will pave the way for groundbreaking advancements in luminescent materials.

Research on carbon black and cerium co-doped Ti4O7-CB-Ce electrocatalytic oxidation of tetracycline-based antibiotics.

Elemental doping is a promising way for enhancing the electrocatalytic activity of metal oxides. Herein, we fabricate Ti/ Ti4O7-CB-Ce anode materials by the modification means of carbon black and cerium co-doped Ti4O7, and this shift effectively improves the interfacial charge transfer rate of Ti4O7 and •OH yield in the electrocatalytic process. Remarkably, the Ti4O7-CB-Ce anode exhibits excellent efficiency of minocycline (MNC) wastewater treatment (100% removal within 20 min), and the removal rate reduces from 100 to 98.5% after five cycles, which is comparable to BDD electrode. •OH and 1O2 are identified as the active species in the reaction. Meanwhile, it is discovered that Ti/ Ti4O7-CB-Ce anodes can effectively improve the biochemical properties of the non-biodegradable pharmaceutical wastewater (B/C values from 0.25 to 0.44) and significantly reduce the toxicity of the wastewater (luminescent bacteria inhibition rate from 100 to 26.6%). This work paves an effective strategy for designing superior metal oxides electrocatalysts.

Antibacterial behavior and mechanism of nitrogen, silicon-doped amphiphilic carbon dots

A new kind of amphiphilic carbon dots (CDs) was prepared with citric acid and silane coupling agent as raw materials. Due to the doping of nitrogen and silicon elements, the surface of CDs contains not only oxygen-containing functional groups, but also alkyl hydrophobic chains, showing amphiphilic characteristic. The micro molecular structure and elemental composition of CDs were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), and other tests. The antibacterial behavior of CDs against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was studied by the disk antibacterial method, plate colony, scanning electron microscopy (SEM) and other methods. The biocompatibility of CDs was evaluated by cytotoxicity and hemolysis in vitro. The results proved that CDs possessed the average particle size of 1.75 nm and the negative surface potential of −2.71 mV. For E. coli and S. aureus, the minimum bactericidal concentrations of CDs were 500 μg/mL and 400 μg/mL, respectively. These co-doped CDs also possessed the ability to inhibit biofilm formation. The antibacterial mechanism was mainly through the adsorption force to rupture the bacterial membrane and induce the generation of reactive oxygen species in bacterial cells. In addition, CDs exhibited excellent biocompatibility because of their low cytotoxicity and hemolysis, indicating that they can be used as a new material in the antibacterial field.

Effect of A and B-site ion doping on the structure and properties of KNN-based ceramic coatings

K0.5Na0.5NbO3 (KNN) ceramics have been widely studied for high Curie temperature (Tc) and good electrical properties. The structural and electrical properties of KNN ceramics were significantly improved by A-site and B-site doping modifications. In this paper, KNN-based ceramic coatings doped with Mn, and Sb were prepared by supersonic plasma spraying. The effects of doping ions at A-site and B-site on the microstructure, phase structure, mechanical properties, and electrical properties of KNN-based ceramic coatings were mainly analyzed. The results show that the surface of the three coatings KNN, K0.5Na0.5Nb0.94Sb0.06O3 (KNNS), and K0.49Na0.49Mn0.02NbO3 (KNMN) is relatively flat, uniform distribution of the elements. The surface roughness (Sa) is 3.85 μm, 3.88 μm, and 3.66 μm, respectively. Pores and cracks are present within the coatings, but the KNNS ceramic coatings have significantly fewer pores and cracks compared to the KNN and KNMN ceramic coatings. XRD results show that KNN-based ceramic coatings exhibit single perovskite structure, and both Mn and Sb are successfully introduced into the KNN ceramics without the generation of a second phase. XPS results showed that the valence states of the elements in the KNN ceramic coatings did not change. In KNMN and KNNS ceramic coatings, the valence state of the doped elements did not change. The addition of Mn2+ and Sb3+ reduced the oxygen vacancy in KNN ceramic coatings. Among them, the KNMN ceramic coatings microhardness increased by 45.3 HV0.2, remnant polarization (Pr) increased by 8.1 μC/cm2, the dielectric constant (εr) increased by 107, and dielectric loss greatly reduced, reaching 0.005. The KNMN ceramic coatings microhardness increased by 90.8 HV0.2, dielectric constant increased by 195, Pr increased by 16.7 μC/cm2, dielectric loss is 0.007. These findings demonstrate that doping with Mn2+ and Sb3+ has a positive impact on the performance of KNN ceramic coatings, with Sb3+ having a greater effect.

Comparative study of physical properties of As2Se3 and (As2Se3)90Ge10 glassy alloys doped with metallic impurities

To examine the compositional and chemical effects on the glassy system, one must first understand its network structure. Alloying glassy systems cause significant conformal and configurational changes. The optical and physical parameters of As2Se3 and (As2Se3)90Ge10 glassy alloys doped with metallic impurities (X = Bi, Cd, Pb, Sb) have been evaluated. A comparison of the physical properties of glassy alloys has been made as the doping elements increase, i.e., from binary to ternary to quaternary system, and an effort has been made to correlate the optical and physical parameters. The optical density (Dop) and penetration depth (δ) have been calculated from the reported absorption coefficient (α) data. The mean coordination number (<r>) and the number of floppy modes (Mf) calculations show that the floppy regions are decreasing, and hence, the rigidity is increasing when As–Se is doped with Ge and As–Se-Ge is doped with X. The density (ρ) and packing density (PD) have also been evaluated, which are interrelated to the parameters like refractive index (n) and δ. Cohesive energy (CE), mean bond energy (<E>), and glass transition temperature (Tg) values give an insight into the stability and average crosslinking of the system with alloying. The conduction and valence band potentials have supported the optical bandgap (Egopt) values variation.

Influence of Ho, Gd, La Doping on Grain-Grain Boundary Characteristics and Minimization of Leakage Current in Nickel Ferrites

This study explores the impact of doping with Ho, Gd, and La on sol-gel-derived nickel ferrites through a comprehensive analysis using various analytical techniques. The combination of X-ray diffraction (XRD) analysis, X-ray fluorescence (XRF) spectra analysis, impedance spectroscopy, and I-V analysis enables a detailed exploration of the structural, compositional, and electrical characteristics of the samples. Williamson-Hall plots in XRD analysis reveal crucial insights into grain and grain boundary impacts, revealing a shift in trends for doped samples indicative of tensile strain and underscores the influence of dopant ions on lattice distortion. XRF study confirms the elemental composition of the samples, validating the experimental approach. Impedance spectroscopy sheds light on conduction mechanisms and charge transfer processes, while the modulus study identifies distinct relaxation peaks corresponding to grain and grain boundary relaxation mechanisms. IV analysis demonstrates a significant reduction in leakage current with rare Earth element doping, suggesting promising applications.

Curcumin-Assisted Synthesis of MoS2 Nanoparticles as an Electron Transport Material in Perovskite Solar Cells.

Recently, two-dimensional (2D) transition metal dichalcogenides (2D TMDs), such as molybdenum sulfide (MoS2) and molybdenum selenide (MoSe2), have been presented as effective materials for extracting the generated holes from perovskite layers. Thus, the work function of MoS2 can be tuned in a wide range from 3.5 to 4.8 eV by adjusting the number of layers, chemical composition, elemental doping, surface functionalization, and surface states, depending on the synthetic approach. In this proposed work, we attempt to synthesize MoS2 nanoparticles (NPs) from bulk MoS2 using two steps: (1) initial exfoliation of bulk MoS2 into few-layer MoS2 by using curcumin-cholesteryl-derived organogels (BCC-ED) and curcumin solution in ethylene diamine (C-ED) under sonication; (2) ultrasonication of the subsequently obtained few-layer MoS2 at 60-80 °C, followed by washing of the above chemicals. The initial treatment with the BCC-ED/C-ED undergoes exfoliation of bulk MoS2 resulted in few-layer MoS2, as evidenced by the morphological analysis using SEM. Further thinning or reduction of the size of the few-layer MoS2 by prolonged ultrasonication at 60-80 °C, followed by repeated washing with DMF, resulted in uniform nanoparticles (MoS2 NPs) with a size of ~10 nm, as evidenced by morphological analysis. Since BCC-ED and C-ED produced similar results, C-ED was utilized for further production of NPs over BCC-ED owing to the ease of removal of curcumin from the MoS2 NPs. Utilization of the above synthesized MoS2 NPs as an ETL layer in the cell structure FTO/ETL/perovskite absorber/spiro-OMeTAD/Ag enhanced the efficiency significantly. The results showed that MoS2 NPs as an ETL exhibited a power conversion efficiency (PEC) of 11.46%, a short-circuit current density of 18.65 mA/cm2, an open-circuit voltage of 1.05 V, and a fill factor of 58.66%, at the relative humidity of 70 ± 10% (open-air conditions) than that of the ED-treated MoS2 devices without curcumin. These results suggest that the synergistic effect of both curcumin and ED plays a critical role in obtaining high-quality MoS2 NPs, beneficial for efficient charge transport, lowering the crystal defect density/trap sites and reducing the charge recombination rate, thus, significantly enhancing the efficiency.

Thermoelectric properties and effective medium theory analysis on the (GeTe)1-x(InTe)x composites

We employed the p-type semiconductor InTe as an extrinsic phase mixing in the GeTe matrix for thermoelectric properties investigations on the (GeTe)1-x(InTe)x (x=0, 0.02, 0.04, 0.06, and 0.08) composites. We observed notable phenomena that a small amount of InTe has a significant influence on the thermoelectric properties as the primary host matrix in the (GeTe)1-x(InTe)x (x=0.02, 0.04, 0.06, and 0.08) composites. Even for small concentrations of InTe which possess lower thermal and electrical conductivities compared to those of GeTe, the thermoelectric properties of the (GeTe)1-x(InTe)x (x=0.02, 0.04, 0.06, and 0.08) composites are primarily influenced by the properties of InTe. We systematically elucidated the electrical conductivity of the (GeTe)1-x(InTe)x (x=0.02, 0.04, 0.06, and 0.08) composites through the application of effective medium theory (EMT). It is found that the effective media of the (GeTe)1-x(InTe)x (x=0.02, 0.04, 0.06, and 0.08) composites is an asymmetric medium insulator. The addition of InTe into GeTe reveals a significant decrease in total thermal conductivity due to reductions in both electronic and lattice thermal conductivity. Particularly, the decrease in lattice thermal conductivity was attributed to an increase in internal strain within the lattice induced by the addition of InTe. Consequently, the ZT values of the composite significantly increase across all temperature ranges. This study suggests that developing composites is an effective approach for enhancing thermoelectric performance, comparable to elemental doping, and demonstrates the ability to analyze the electrical properties of composite materials using EMT.

Rare earth doped bimetal hydroxide/multi-walled carbon nanotubes as composite electrodes to achieve high-energy-density asymmetric supercapacitors

A novel electrode material of Ni–Co bimetallic hydroxide composite multi-wall carbon nanotubes (La–NiCo LDH/MWCNTs/NF) doped with rare earth elements was prepared on nickel foam (NF) by a one-step hydrothermal method and doped with different concentrations of La3+ ions. The introduction of La3+ ions can increase the layer spacing of LDH materials. The acidification of MWCNTs on the surface of NF can also enhance the collection effect of NF. The synergistic effect of MWCNTs and La3+ ions further improves the specific capacitance of the material. At the current density of 1 A g−1, the maximum specific capacitance of the sample with 5 % La3+ ion concentration reaches 4396.0 F g−1, and the capacitance retention is 70.31 % after 3000 cycles of a single electrode. When assembled into a device, the device obtains a high energy density of 77.86 Wh kg−1 at a power density of 800.0 W kg−1. After assembling into an asymmetric supercapacitor, it has undergone 8000 cycles of performance testing, and the capacitance ratio is only reduced by 4.9 %. It shows good electrochemical cycle performance. This work provides a new way to study the doping of rare earth elements for supercapacitor materials.

Doping and strain effect on the catalytic performance of Tin+1CnO2 (n = 2, 3) for hydrogen evolution reaction

Mxenes has attracted wide attention due to its advantages of high conductivity, diverse composition, thinness and adjustable structure. In this paper, we systematically calculated adsorption energy, Gibbs free energy, and exchange current density of Ti3C2O2 and Ti4C3O2. The effect of H-coverage, element (Cr, Hf, Mo, Nb, Ta, V) doping and strain application on the HER catalytic performance were also analyzed. The results show that Ti4C3O2 has stronger catalytic ability than Ti3C2O2. H coverage is negatively correlated with catalytic performance of Tin+1CnO2 (n = 2, 3). Among calculated doping elements, for improving catalytic ability of Ti3C2O2, V or Mo doping is beneficial. While for Ti4C3O2, only Mo doping is beneficial. Furthermore, compression strain of −5%, −3%, −1% is beneficial for improving catalytic performance of Ti3C2O2 and Ti4C3O2. Our work reveals the microscopic mechanism of MXene catalyzing HER, which is useful for the further development of water electrolysis catalysts.