Transition Metal Ion Doping Research Articles

Constructing electrochemically stable single crystal Ni-rich cathode material via modification with high valence metal oxides

Single crystal Ni-rich cathode materials (SCNCM) are a good supplement in the market of nickel-based materials due to their safety and excellent electrochemical performance. However, the challenges of cation mixing, phase change during charge/discharge, and low thermal stability remain unresolved in single crystal particles. To address these issues, SCNCM are rationally modified by incorporating transition metal (TM) oxides, and the influence of metal ions with different valence states on the electrochemical properties of SCNCM is methodically explored through experimental results and theoretical calculations. Enhanced structural stability is demonstrated in SCNCM after the modifications, and the degree of improvement in the matrix materials varies depending on the valence state of doped TM ions. The highest structural stability is found in WO3-modified SCNCM, due to the smaller effective ion radii, higher electro-negativity, stronger W–O bond, and efficient suppression of oxygen vacancy generation. As a result, WO3-modified SCNCM have outstanding cycle performance, with a capacity retention rate of 90.2% after 200 cycles. This study provides an insight into the design of advanced SCNCM with enhanced reversibility and cyclability.

Hydrothermally synthesized transition metal doped ZnO nanorods for dye degradation and antibacterial activity

Abstract In this study, Ni-doped ZnO (NZ) and Ni–Mn dual-doped ZnO (NMZ) NPs were synthesized by hydrothermal method. Various analytical techniques, such as XRD, UV–vis, FTIR, PL, SEM, EDAX, and HR-TEM, were employed to investigate the effect of doping transition metal ions in the ZnO lattice. The powder X-ray diffraction (XRD) patterns confirmed a hexagonal structure with average crystallite sizes of 30.66 nm and 27.09 nm for NZ and NMZ nanoparticles, respectively. Tauc’s plot showed that the energy bandgap was redshifted to 2.9 from 2.8 eV by doping transition metal ions in ZnO. The photoluminescence spectrum displayed various peaks, indicating the emission behaviour of the nanomaterials. The photocatalytic performance of the catalysts was tested under visible light sources against Crystal Violet (CV) dye. The degradation efficiency, for NMZ achieved a maximum degradation efficiency of 91.1 %. Antibacterial activity was evaluated against gram-positive (B. subtilis and S. aureus) and gram-negative (E. coli and P. aeruginosa) bacteria. The NMZ exhibited higher photocatalytic and antibacterial activity than NZ.

Photon–carrier–spin coupling in a one-dimensional Ni(II)-doped ZnTe nanostructure

Transition metal (TM) ion doping in II–VI semiconductors can produce exciton magnetic polarons (EMPs) and localized EMPs containing longitudinal optical (LO) phonon coupling, which will be discussed in this paper. TM ion doping in II–VI semiconductors for a dilute magnetic semiconductor show emission via magnetic polarons (MPs) together with hot carrier effects that need to be understood via its optical properties. The high excitation power that is responsible for hot carrier effects suppresses the charge trapping effect in low exciton binding energy (8.12 meV) semiconductors, even at room temperature (RT). The large polaron radius exhibits strong interaction between the carrier and MP, resulting in anharmonicity effects, in which the side-band energy overtone to LO phonons. The photon-like polaritons exhibit polarized spin interactions with LO phonons that show strong spin–phonon polaritons at RT. The temperature-dependent photoluminescence spectra of Ni-doped ZnTe show free excitons (FX) and FXs interacting with 2LO phonon–spin interactions, corresponding to 3T1(3F) → 1T1(1G) and EMP peaks with ferromagnetically coupled Ni ions at 3T1(3F) → 1E(1G). In addition, other d–d transitions of single Ni ions (600–900 nm) appear at the low-energy side. RT energy shifts of 14–38 meV are observed due to localized states with density-of-states tails extending far into the bandgap-related spin-induced localization at the valence band. These results show spin–spin magnetic coupling and spin–phonon interactions at RT that open up a more realistic new horizon of optically controlled dilute magnetic semiconductor applications.

Efficient electrocatalytic reduction of nitrate to ammonia using Cu–CeO2 solid solution

Electrocatalytic nitrate reduction reaction (EC-NITRR) is expected to replace Haber-Bosch process for green ammonia (NH3) production. Currently, many catalysts often result in low NH3 yields and low faraday efficiencies due to the lack of active sites. In this study, Cu-doped CeO2 solid solution catalyst was prepared for EC-NITRR using transition metal ions doping. The addition of Cu significantly improved the oxygen vacancy (Ov) concentration of CeO2 and provided more active sites for NO3− catalysis. Meanwhile, the internal charge transfer capability and surface catalytic kinetics of the catalyst are enhanced by the excellent redox capability of Ce3+ and Cu+. Compared with bare CeO2, the NH3 yield of 7% Cu–CeO2 increased by 1.88 times. This work provides new ideas for the design of green and efficient catalysts for EC-NITRR by identifying the role of Cu in the mechanism of doping regulation of CeO2.

Evidence and Practical Applications of Site Occupancy Theory (SOT) of Eu3+ in Scheelite Compounds.

The determination of the site occupancy of activators in phosphors is essential for precise synthesis, understanding the relationship between their luminescence properties and crystal structure, and tailoring their properties by modifying the host composition. Herein, one simple method was proposed to help determine the sites at which the doping of rare earth ions or transition metal ions occupies in the host lattice through site occupancy theory (SOT) for ions doped into the matrix lattice. SOT was established based on the fact that doping ions preferentially occupy the sites with the lowest bonding energy deviations. In order to provide detailed experimental evidence to prove the feasibility of SOT, several scheelite-type compounds were successfully synthesized using a high-temperature solid-phase method. When Eu3+ ions occupy a similar surrounding environment site, the photoluminescence spectra of the activators Eu3+ are similar. Therefore, by comparing the intensity ratio of photoluminescence spectra and the mechanism of all transitions of KEu(WO4)2, KY(WO4)2:Eu3+, Na5Eu(WO4)4, and Na5Y(WO4)4:Eu3+, it was proved that SOT can successfully confirm the site occupation when doped ions enter the matrix lattice. SOT was further applied to the sites occupied by Eu3+ ion-doped LiAl(MoO4)2 and LiLu(MoO4)2.

Highly Selective and Reversible Detection of Simulated Breath Hydrogen Sulfide Using Fe-Doped CuO Hollow Spheres: Enhanced Surface Redox Reaction by Multi-Valent Catalysts.

The precise and reversible detection of hydrogen sulfide (H2S) at high humidity condition, a malodorous and harmful volatile sulfur compound, is essential for the self-assessment of oral diseases, halitosis, and asthma. However, the selective and reversible detection of trace concentrations of H2S (≈0.1ppm) in high humidity conditions (exhaled breath) is challenging because of irreversible H2S adsorption/desorption at the surface of chemiresistors. The study reports the synthesis of Fe-doped CuO hollow spheres as H2S gas-sensing materials via spray pyrolysis. 4 at.% of Fe-doped CuO hollow spheres exhibit high selectivity (response ratio ≥ 34.4) over interference gas (ethanol, 1ppm) and reversible sensing characteristics (100% recovery) to 0.1ppm of H2S under high humidity (relative humidity 80%) at 175 °C. The effect of multi-valent transition metal ion doping into CuO on sensor reversibility is confirmed through the enhancement of recovery kinetics by doping 4 at.% of Ti- or Nb ions into CuO sensors. Mechanistic detailsof these excellent H2S sensing characteristics are also investigated by analyzing the redox reactions and the catalytic activity change of the Fe-doped CuO sensing materials. The selective and reversible detection of H2S using the Fe-doped CuO sensor suggested in this work opens a new possibility for halitosis self-monitoring.

Influence of Transition Metals on the Development of Semiconducting and Low Thermal Expansion TiO2-Borosilicate Glasses and Glass Ceramics

This current investigation represents as well as discusses in detail the characterization of the thermal, mechanical, as well as electrical characteristics of titanium-based borosilicate glasses doped transition metal ions (3d) in addition to their corresponding glass–ceramics. The building structural units of the as-prepared glasses together with their glass – ceramic were characterized by the FTIR technique. FTIR spectra reveal characteristic silicate and borate groups vibrations, some of the TiO4 units are formed beside (TiO6) groups. The progressive enhancement in microhardness and thermal expansion values was recorded for glass – ceramic state that occurred as a result of the crystallization of nano-sized crystals throughout the glass matrix. The estimated electrical parameters which include permittivity (ε'), dielectric loss (ε''), AC conductivity (σac) capacitance (C), and dielectric loss demonstrated a distinctive variation in their values in accordance with the type of transition metal and /or the applied frequency. The prepared glass–ceramic was found to be suitable for use in electronics and solar cell applications based on its overall thermal and electrical properties.

Electrochemical activity of 3d transition metal ions in polyanionic compounds for sodium‐ion batteries

AbstractSodium‐ion batteries are expected to replace lithium‐ion batteries in large‐scale energy storage systems due to their low cost, wide availability, and high abundance. Polyanionic materials are considered to be the most promising cathode materials for sodium‐ion batteries because of their cycling stability and structural stability. However, limited by its poor electronic conductivity, the electrochemical performance needs to be further improved. This paper reviews the characterization and development of 3d transition metal ions polyanionic compounds, along with the summarized effect of structure and particle size on the performance and improvement of electrochemical properties. Meanwhile, crystal structure modulation, transition metal ion choice, and transition metal ion doping can improve the electrochemical performance and energy density of polyanionic compounds. Finally, this review points out the challenges of polyanionic compounds and puts forward some particular standpoints, contributing to the promising development of polyanionic compounds in the large‐scale energy storage market.

Mo-doped porous Co3O4 nanoflakes as an electrode with the enhanced capacitive contribution for asymmetric supercapacitor application

Cobalt oxide (Co3O4) electrode materials have tremendous properties for supercapacitors, such as being environmentally friendly, having a high surface area, being low cost, and having high theoretical specific capacitance (3560 Fg−1). However, its poor electronic conductivity restricts the performance of the practical application. Doping transition metal ions into the host materials is an effective method to improve conductivity and enhance storage capacity. In this research work, we studied Mo-doped Co3O4 nanostructure electrodes synthesized using the electrodeposition technique. The integrated material samples were characterized by XRD, SEM with EDAX, XPS, FTIR, Raman spectra, UV–visible, and BET for their structure, morphology, composition, optical, and surface area properties. The 2 mM Mo-doped Co3O4 electrode exhibits excellent electrochemical pseudocapacitive properties. The optimized Mo2-doped Co3O4 shows a maximum specific capacitance of 1674 Fg−1 at 10 mA cm−2 current density in 1 M KOH electrolyte solution. Finally, the asymmetrical hybrid supercapacitor device (AsHScD) Mo2-Co3O4//rGO) demonstrates the highest power density of 159.0 KWKg−1 and maximum energy density of 13.80 WhKg−1 with a long-term stability of 95 % up to 2000 cycles. The Mo2-Co3O4 electrode is a promising candidate material for a charge-storage hybrid supercapacitor in an aqueous 1 M KOH electrolyte.

Low-dimensional II–VI semiconductor nanostructures of ternary alloys and transition metal ion doping: synthesis, optical properties and applications

Light matter interactions in spin-controlled devices, which are also known as dilute magnetic semiconductors, have gained significant attention in the past few years.

Advancing understanding of structural, electronic, and magnetic properties in 3d-transition-metal TM-doped α-Ga2O3 (TM = V, Cr, Mn, and Fe): A first-principles and Monte Carlo study

In this paper, we investigated the properties of transition metal (TM)-doped α-Ga2O3 using first-principles calculations and Monte Carlo simulations. α-Ga2O3 is a wide-bandgap semiconductor material with enhanced performance and lower fabrication costs on sapphire substrates compared to β-Ga2O3. Doping with TMs can modify electrical transport, optical absorption, and magnetic properties, yet theoretical studies on this are scarce. Our study focused on V, Cr, Mn, and Fe impurities. We introduced a newly proposed scheme for efficiently determining the ground-state defect configuration during structural relaxation. We adopt a recent, novel image charge correction method to accurately calculate formation enthalpy and thermodynamic transition levels for spin-polarized transition metal ion doping, without employing the empirical dielectric constant. Results showed Cr ions tend to neutral substitutional Ga, while V, Mn, and Fe impurity ions tend to carry a negative charge in common n-type α-Ga2O3. Magnetic moments and spin-splitting impurity levels primarily arise from transition metal impurities and their d orbitals. We used the generalized four-state method to calculate exchange interaction constants between substitution lattice sites and identified (anti) ferromagnetic couplings at specific distances in a 120-atom supercell, which are negligible in total energy calculations. Monte Carlo simulations indicated a Curie temperature of 360 K in n-type α-Ga2O3: Mn system with 12.5% doping, suggesting intrinsic ferromagnetic ordering based on the Heisenberg model. Our study contributes to understanding TM-doped α-Ga2O3 electronic structure and magnetic properties through improved methodologies. The approach can be applied in research involving other TM-doped oxides or wide-bandgap semiconductors.

Ultra-fast photocatalytic degradation and seed germination of band gap tunable nickel doping ceria nanoparticles

Doping transition metal ions into cerium oxide (CeO2) results in interesting modifications to the material, including an increase in surface area, a high isoelectric point, biocompatibility, greater ionic conductivity, and catalytic activity. Herein, various concentrations (1–5%, 10% and 20%) of nickel (Ni) doped CeO2 nanoparticle have been made by a facile chemical process. Using a variety of cutting-edge analytical techniques, the structural, optical, and photocatalytic properties of undoped and varied concentrations (1–5%, 10%, and 20%) of Ni doped CeO2 nanoparticles have been investigated. Pure cubic fluorite structure with average crystallite sizes in the region of 12–15 nm was determined by X-ray diffraction (XRD) investigation. Transmission electron microscopy (TEM), which revealed highly homogeneous hexagonal shape of the particles with average size of 15 nm, was also used to determine microstructural information. According to the optical absorption, the band gaps of Ni doped and undoped CeO2 nanoparticles were found to be 2.96 eV and 1.95 eV, respectively. When exposed to sunlight, the narrow band gap Ni doped CeO2 nanoparticles worked as an active visible light catalyst to remove the dyes Rose Bengal (RB) and Direct Yellow (DY). The best photodegradation efficiencies for RB and DY dyes were found about 93% and 97%, respectively, using the 5% Ni-doped CeO2 catalyst. The apparent rate constant values of 0.039 for RB and 0.040 min−1 were attained for DY. As well, the treated, untreated dye solution and control solutions were utilized to assess the toxicity of commercially accessible Vigna Radiata seeds. In this study exhibits percentages of length and germination increased by 30–35% when compared to dye pollutant solution. The Ni doped CeO2 can provide a substantial alternative for current industrial waste management because of its quick photocatalytic activity and remarkable seed germination results.

Understanding Na+ ion diffusion in 1 T-MO2 (M = Mn, Fe, and Ni) via potential energy surface calculation

The cooperative Jahn-Teller effect (CJTE) plays a very important role in the study of sodium ion batteries with layered transition metal oxides 1 T-MO2 (M = Mn, Fe, and Ni) as electrodes. We have used the potential energy surface (PES) approach to describe the diffusion process of Na+ ion in these electrode materials. The successive distorting-and-hopping process was identified. For pure electrodes, the diffusion barrier of Na+ ion in FeO2 is smaller than MnO2 and NiO2. We have also investigated the diffusion mechanism of Na+ in the substitutional doped system. In MnO2, the Jahn-Teller (JT) effect of Mn3+ is modulated by the substitution of Ni and Co, and the diffusion barrier increases. In FeO2, the JT effect of Fe4+ is suppressed by the substitution of Co, Mn and Ni, and the diffusion barriers are reduced. We find that the substitutional doping of transition metal ions is an effective way to modulate the cooperative Jahn-Teller effect which helps to improve the batteries' cycling stability or rate performance.

Probing the electrocatalytic activity of hierarchically mesoporous M-Co3O4 (M = Ni, Zn, and Mn) with branched pattern for oxygen evolution reaction

The large-scale production of hydrogen energy from the electrolysis of water requires earth-abundant and highly efficient oxygen evolution electrocatalysts. Cation substitution in spinel cobaltite is an efficient approach to tune electronic structure and improve their electrocatalytic activity towards oxygen evolution reaction (OER). In this article, for the first time, we have prepared hierarchically nanostructured Mn, Ni and Zn doped Co3O4 having a branching pattern via a simple hydrothermal and calcination method, and the same was used as an electrocatalyst for OER. Different methods confirmed the doping of transition metal ions. The result of structural characterization shows the formation of pure phase samples without impurity. The tetrahedral and octahedral functional groups were explained by FTIR spectroscopy, confirming the formation of a spinel structure. Ni-doped Co3O4 showed an excellent OER performance with a current density of 10 mA/cm2 at an overpotential of 380 mV in 1 M KOH and a Tafel slope of 63.19 mV/dec in alkaline media. The detailed study unveiled that the large surface area, hierarchically nanostructured branching pattern with porous structure, presence of a high amount of oxygen vacancy and the synergistic effect of Ni and Co are beneficial for increased OER activity and stability of Ni-Co3O4.

Mitigation of cation mixing of LiNiO2-based cathode materials by Li-doping for high-performing lithium-ion battery

Element doping of transition metal (TM) ions is commonly employed in the enhancement of structural and interfacial stability of layered nickel-rich cathode materials to construct high energy density lithium-ion batteries. However, one of the main factors for structural evolution and poor electrochemical stability of the layered nickel-rich cathode materials is the inherent Li+/Ni2+ disorder caused by dopants. To regulate the cation mixing, herein, the Li-doping is introduced into the TM slabs of the LiNiO2-based materials. Benefited from the charge compensation of the TM layers, the doped Li+ ions lead to the alleviation of the Li+/Ni2+ disorder generated during the synthesis stage and electrochemical charge/discharge cycles. It is demonstrated that proper amount of the doped Li+ ions would enhance the stability of the crystal lattice, improve the Li+ diffusion between electrode and electrolyte, and suppress the microcrack formation in the secondary grains of the materials. This is verified by the synergistic effect of Li/Mn co-doping, in particular, the LiNiO2-based layered material with 11 mol% Li and 1 mol% Mn exhibits great improvement in long-term cycling stability with capacity retention 71.11% after 200 cycles at 0.5C. The Li-doping strategy might provide a new perspective to the enhancement of structural stability of the layered nickel-rich materials for lithium-ion batteries in the future.

Structural and optical properties of Yttrium-Silver doped ZnO nanoparticle

Due to the fact that transition metal and rare earth ion doping may significantly alter and enhance the optical characteristics of II-VI semiconductor nanoparticles, these materials have recently attracted a lot of attention. Here, undoped and yttrium-silver doped zinc-oxide (x = 0.0,0.1,0.2) nanoparticles were successfully synthesized by the sol–gel method. The structural, morphological, and optical properties of Z(1-x)Y(x/2)Ag(x/2)O were examined. A well-arranged crystallite hexagonal structure was revealed by XRD patterns. The crystallite size for pure and doped ZnO observed by the Scherrer formula was less than 20 nm. The uniformly distributed, hexagonal-shaped particles were observed by FESEM. EDAX confirms the presence of Zn, Y, Ag, and O. UV analysis revealed that the band gap for pure ZnO is 5.11 eV, whereas the band gap for Y-Ag doped ZnO (0.1 and 0.2) is 4.96 and 5.04 eV, respectively.

Impact of Y2O3 on structural, mechanical and nonlinear optical properties of CrO3-Na2O-B2O3 glasses

Herein, we investigate the effects of transition metal (Cr3+), alkali (Na1+), and rare earth (Y3+) ion doping on the structural, mechanical, and nonlinear optical properties of borate glass. The structural parameters revealed peculiar behaviors. The total ions concentrations values decreased from 2.13 × 1022 cm−3 for 0 mol% of Y2O3 to 2.04 × 1022 cm−3 for 5 mol% of Y2O3. The atomic packing density parameter (APD) values decreased from 67 % for 0 mol% of Y2O3 to 62 % for 5 mol% of Y2O3 additions. The mechanical parameters such as Young, shear, and bulk moduli showed decreased behaviors with further Y2O3 additions. The linear and nonlinear optical properties, such as refractive index, third-order nonlinear susceptibility, nonlinear refractive index, metallization criterion, average electronegativity, electronic polarizability, and optical basicity, were evaluated. The linear and nonlinear refractive indices showed increasing behaviors with further Y2O3 additions. These increased behaviors were attributed to the increased content of nonbridging oxygens with more Y2O3 additions. The present glasses have metallization criterion values between 0.377 and 0.387, which are optimal for use in nonlinear optical devices.

Ni-doped hybrids of TiO2 and two-dimensional Ti3C2 MXene for enhanced photocatalytic performance

Transition metal ion doping is an effective strategy by which to enhance the photocatalytic activity of semiconductor materials. Herein, Ni-doped TiO 2 /Ti 3 C 2 photocatalysts were designed and fabricated using a simple dipping method and their catalytic performance was verified via the degradation of rhodamine B (RhB). Ni doping induces the formation of a defect energy level in TiO 2 , which shortens the transition distance of photogenerated electrons. Ti 3 C 2 acts as a hole acceptor, which is conducive to the transfer of photogenerated charge. The results show that the Ni-doped TiO 2 /Ti 3 C 2 heterojunction structure exhibits the lowest photoluminescence peak intensity, the highest instantaneous current, and excellent photocatalytic performance compared to TiO 2 /Ti 3 C 2 and TiO 2 . At optimal Ni content, the removal efficiency of RhB is 90%, around 3.7 times higher than that of pure TiO 2 . This work details the preparation of an excellent Ni-doped heterojunction structure for enhanced photocatalytic performance, demonstrating an effective strategy by which to improve the charge separation ability. • Ni-doped hybrids of TiO 2 and Ti 3 C 2 MXene structure was prepared for enhanced photocatalytic performance. • The charge separation ability of TiO 2 was enhanced due to the doping of Ni and the coupling of co-catalyst Ti 3 C 2 . • The removal efficiency of RhB by Ni–TiO 2 /Ti 3 C 2 was 3.7 times higher than that of pure TiO 2 .

Magnetic, Phonon and Optical Properties of Transition Metal and Rare Earth Ion Doped ZnS Nanoparticles.

The surface, size and ion doping effects on the magnetic, phonon and optical properties of ZnS nanoparticles are studied based on the s-d model including spin-phonon and Coulomb interaction, and using a Green's function theory. The changes of the properties are explained on a microscopic level, due to the different radii between the doping and host ions, which cause different strains-compressive or tensile, and change the exchange interaction constants in our model. The magnetization increases with increasing small transition metal (TM) and rare earth (RE) doping concentration. For larger TM dopants the magnetization decreases. The phonon energies increase with increasing TM, whereas they decrease by RE ions. The phonon damping increases for all doping ions. The changes of the band gap energy with different ion doping concentration is also studied. Band gap changes in doped semiconductors could be due as a result of exchange, s-d, Coulomb and electron-phonon interactions. We have tried to clarify the discrepancies which are reported in the literature in the magnetization and the band gap energy.

Investigations on the role of doped 3d transition ions in Li2B4O7 glasses: Local structures, spectroscopic properties and optical basicities

Glasses with doped transition metal ions (TMs) have shown specific spectroscopic properties, but the micro-mechanism is hard to be obtained due to the amorphous structure. Based on the high order perturbation formulae of electron paramagnetic resonance (EPR) parameters, the local environment of 3d ions (V4+, Cr3+, Mn2+ and Cu2+) in Li2B4O7 glasses is studied to explain the experimental EPR spectra. The spectroscopic properties of Li2B4O7 glasses are closely correlated with the doped 3d ions, which can be reasonably predicted from the transition bands of divided energy orbitals. The crucial optical basicities of Li2B4O7 glasses doped with different TMs are also investigated, which are consistent with the above calculation results with respect to the local environment. The results show that TMs doping can be an effective way to modify the intrinsic properties of glasses.