Transition Metal Doping Research Articles

Enhancement of La–Ti modification on the conductivity and stability of Co-free Li- and Mn-rich layered cathode

Lithium (Li) - and manganese (Mn)-rich oxides (xLi2MnO3·(1−x) LiTMO2, TM = Ni, Co, Mn, etc.) are one of the most promising cathode materials because of their high theorical capacity, which is contributed by the redox of both transition metal cations and oxygen anion. However, anionic redox leads to transition-metal migration and release of lattice oxygen, which further triggers voltage decay and capacity fade. Here, we report a dual-doping and multiphase co-existence strategy to tackle the structure degradation of Li- and Mn-rich materials and enhance electrochemical kinetics. La–Ti dual cations doping strength the TM-O bonds and improve cycling stability, and the inducement of LaMnO3+δ (LaMO) phase provides higher conductivity. As a result, the unique architecture presents a favourable rate performance, improved capacity retention, and suppressed voltage decay. After 200 cycles at 1C (250 mA g−1), the La–Ti dual cations doped Li-and Mn-rich material shows 24 % higher capacity retention and 52 % lower voltage decay compared to the non-doped material. This study demonstrates the potential of dual transition-metal ion doping combined with doping-induced perovskite phase to enhance the performance of Li- and Mn-rich materials.

Supremacy of in-situ doping over surface loading technique for the preparation of alkali metal-promoted tellurates as efficient reusable catalysts to approach hydroxylation and dehalogenation of aryl halides

The novel alkali metal doped transition metal tellurate catalysts are prepared by two different methods, namely the in-situ doping method (alkali metal is added to the hydroxides of copper and tellurium and then calcinated) and surface loading method (alkali metal is added to the as-prepared metal tellurate and then calcined second time). In this study, the supremacy of in-situ doping over surface loading of alkali metal promoters (AM: Na, K, Rb, or Cs) to the metal tellurate for hydroxylation of aryl halides and dehalogenation of aryl halides reactions are investigated. Besides, the catalytic activity depends on the AM used for doping; the decreasing order of activity is K-Cu3TeO6 > Na-Cu3TeO6 > Rb-Cu3TeO6 > Cs-Cu3TeO6 and the occupancy of AM is in the sequence of Cs+ < Rb+ < K+ < Na+. The presence of the potassium on the copper tellurate is confirmed by XPS and flame photometry even after 6 cycles.

Degradation of phenol by peroxymonosulfate catalyzed by cerium-doped amino-functionalized metal-organic frameworks (NH2-MIL-101 (Fe, Ce))

As an organic pollutant difficult to be degraded in water bodies, phenol is toxic even at low concentrations. Therefore, studying the degradation technology of phenol is of great significance. In order to investigate the effect of transition metal doping on the performance of oxidative degradation of phenol by the persulfate activated by metal-organic frameworks, the different doping levels of Ce were tested based on the NH2-MIL-101(Fe). Then, NH2-MIL-101(Fe,Ce) with different Fe/Ce ratios was successfully prepared by solvothermal method. They were characterized by means of XRD, SEM, TEM, XPS and FT-IR. Selecting phenol as the target pollutant, the NH2-MIL-101(Fe,Ce)/PMS system was constructed to study the degradation rate. The factors of the different temperature, initial pH, anions, Ce doping ratios, catalyst dosage and PMS concentration were investigated. The mechanism of degradation of phenol for the above system was analyzed through free radical burst test, and the metal ion dissolution of catalytic materials in simulated wastewater treatment process was monitored by ICP-OES instrument. Finally, the intermediate products of phenol in the degradation process were inferred using LC-MS method. The results showed that when the molar ratio of Ce/(Ce+Fe) was 15 %, under the same reaction conditions, NH2-MIL-101(Fe,Ce)-15 % (referred to as NM-15 %) had the highest degradation rate for phenol. After the 50 min, phenol could be almostly completely removed, with K value of 0.059 min−1. This system could achieve the efficient degradation of phenol under the range of pH values (pH=3–9). The results of the free radical burst test and the free radical trapping test showed that the dominant oxidising groups were SO4•−, •OH, •O2− and non-free radical 1O2.

H2S sensitivity of transition metal-doped Y2CF2 with F-vacancies: A DFT study

In this study, Density Functional Theory (DFT) was used to investigate the potential of Y2CF2, a two-dimensional (2D) material, as a promising sensor for H2S gas detection. The effects of F-defects and transition metal (TM = Ti, V, Cr, Zr, Nb, Mo) doping on the geometric, electrical, and sensitive properties of Y2CF2 were examined. With pristine Y2CF2, physical adsorption toward H2S was observed, while with F-vacancies, chemical adsorption occurred. The adsorption capacities of the TM-doped systems for H2S were influenced by the specific doping atoms. For Ti-, V-, and Nb-doped adsorption systems, adsorption energies and charge transfer were higher, and the desorption time was faster. For V-doped Y2CF2, there was an obvious change in the band gap after H2S gas molecules were adsorbed, and this can be used as a signal for H2S gas detection. Therefore, because of the high sensitivity, obvious change of band gap, and appropriate desorption time, V–Y2CF2 has excellent potential for application as sensor for H2S gas detection. The findings of this study highlight the material's promising potential in sensor research.

Quantum capacitance behavior of Ti2CO2/MoS2 heterostructures with 3d and 4d transition-metal doping

The storage capacity of capacity, quantum capacitance behavior, and atomic stability of O-defected, S-defected, 3d and 4d transition-metal (3d-TMs: Sc, Ti, V, Cr, Mn, Fe, Co, and Ni; 4d-TMs: Y, Zr, Nb, Mo, Ru, Rh, Pd, and Ag) doped Ti2CO2/MoS2 heterostructures were studied by density functional theory (DFT). Pristine Ti2CO2/MoS2 exhibited a high quantum capacitance of 1038.62 μF/cm2 at the positive potential. The appearance of O-vacancy in Ti2CO2-layer enhanced the capacitance of Ti2CO2/MoS2 at negative bias, and S-vacancy induced an obvious improvement of quantum capacitance at 0 V. After introducing various transition metals into modified Ti2CO2/MoS2 heterostructures, the doping in pristine structures increased the capacitance value to be 1182.71 μF/cm2 (Y-doping), while TM-doping in S-vacancy defected Ti2CO2/MoS2 systems induced a slight decrease of capacitance at positive potentials. For TM-doped O-defected Ti2CO2/MoS2, only Sc- and Y-doped systems exhibited higher quantum capacitance than the pristine Ti2CO2/MoS2, which were 1093.60 and 1096.26 μF/cm2. Due to the obvious advantage of capacitance of pristine Ti2CO2/MoS2 than Ti2CO2 or MoS2 single-layer at the positive bias, it can be used as effective anodes for high-capacitance supercapacitors, while 3d or 4d TM-doping had no significant enhancement in capacitance behaviors. The findings in this study were supposed to be theoretical data base to design high-performance supercapacitors.

The effect of different transition metal dopants on the magnetic properties of armchair antimonene, phosphorene, and their binary nanoribbons

Binary antimonene-phosphorene, a novel two-dimensional material with a medium band gap, high carrier mobility, and environmental stability, has attracted growing attention due to its wide applications in spintronics. Using density functional theory, we comprehensively investigate and compare the structural and magnetic properties of armchair Sb, P, and binary SbP nanoribbons doped with 3d transition metal atoms (Ti, Cr, Mn, Fe, Co, and Ni) with various concentrations of dopant atoms. We investigated magnetic properties, including magnetic moment, spin polarization, and spin density. It was found that the magnetic properties for single P and Sb nanoribbons do not depend on the substitution position of TM atoms. In contrast, for binary SbP nanoribbons, the substitution of TM atoms in P or Sb positions leads to different behaviors. For example, the magnetization for substitution of Fe and Co atoms in the P position of the binary SbP nanoribbon will be greater than those of the Sb position, but for other impurity atoms, the magnetization of the binary SbP nanoribbon does not strongly depend on the substitution position. The results show that with increasing the number of impurity atoms in the nanoribbon, the magnetic moment increases, except for the nickel atom in the Sb position of the SbP nanoribbon, in which the nanoribbon prefers the ferrimagnetic state. Also, the spin density results show that the magnetism of the doped systems is mainly attributed to the dopant atoms, and the neighboring atoms have a negligible contribution. The findings of antimonene-phosphorene nanoribbons doped with TM atoms may have potential applications in spintronic nanodevices.

Improvement of Mechanical Properties of β-AlSiFe Phase by Doping Transition Metals (M = Cr, Mn, V, Ti, and Zr): A First-Principles Study

Improvement of Mechanical Properties of β-AlSiFe Phase by Doping Transition Metals (M = Cr, Mn, V, Ti, and Zr): A First-Principles Study

Selection Rules of Transition Metal Dopants for Prussian Blue Analogs Enabling Highly Reversible Sodium Storage

AbstractRational element doping is demonstrated as an effective strategy to optimize crystal stability and enhance the electronic conductivity of Prussian blue analogs (PBAs) to achieve a satisfactory sodium storage performance. However, unraveling the dopant selection principles is still a big challenge. Herein, the integrated crystal orbital Hamilton population (ICOHP) function is adopted to evaluate the strength of chemical bonds of N‐transition metals (N‐TM) and guide the dopant selection. Among the series of ICOHP values for N‐TM (TM = Mn, Fe, Co, Ni, Cu, Zn), the Cu─N bond exhibits the lowest ICOHP value, which indicates that Cu doping can improve the stability of PBAs compared to other dopants. Experimentally, among TM‐substituted Fe‐based PBAs (TMFeHCFs), the as‐prepared sample with 20 at.% Cu doping (CuFeHCF‐2) exhibits the best cycling performance, with a capacity retention of 83.5% after 400 cycles at 1 C, which is consistent with the theoretical calculation results. In addition, in situ XRD and in situ, Raman reveal a highly reversible monoclinic‐cubic two‐phase conversion and redox‐active pairs, respectively. This study provides valuable guidelines for dopant selection to enhance the performance of PBAs cathodes.

Exploration of transition metal atom-doped NiSe2 electrocatalysts for efficient alkaline hydrogen precipitation using first principles screening

Transition metal (TM) doping exhibits great potential in designing high-performance two-dimensional (2D) NiSe2-based catalysts for electrocatalytic hydrogen evolution reaction (HER). 22 TM atom-doped 2D-NiSe2 catalysts are screened, and the effects of TM doping on the thermal stability and HER catalytic activity are investigated by first-principles calculations. Among them, Cu doped 2D-NiSe2 might exhibit remarkable HER properties with the water dissociation energy of 1.03 eV and H adsorption Gibbs free energy of −0.05 eV. Furthermore, we elucidate the reasons behind the different HER activities. These findings suggest new possibilities for the application of Cu doped 2D-NiSe2 for alkaline HER, offering new perspectives for future research.

First principles study of transition metal (TM = Sc, Ti, V, Cr, Mn) doped penta-BAs5 monolayer for adsorption of CO, NH3, NO, SO2

In this paper, the adsorption capacity of intrinsic penta-BAs5 monolayer on CO, NH3, NO, SO2 and the effect of transition metal doping on gas sensing characteristics are systematically studied by first-principles calculations. Adsorption energy, recovery time, band structure, charge transfer and density of states (DOS) are investigated. The electronic properties and sensing mechanisms under different adsorption systems are expounded. The results showed that the intrinsic penta-BAs5 monolayer had the strongest adsorption capacity for NO and weak sensitivity to CO, NH3 and SO2, which shown strong gas selectivity. Moreover, the recovery time of NO at 380 k was 3.93 s, which was more inclined to be desorption at high temperature. In addition, Sc and Ti doping could selectively improve the adsorption capacity of the intrinsic penta-BAs5 monolayer. The charge transfer of SO2-Sc-BAs5 and CO-Ti-BAs5 were increased by 6.78 and 10.33 times compared with those before doping. The band structure and DOS show that Ti atom and CO have orbital hybridization, which improved the interaction between gases and penta-BAs5. Therefore, intrinsic penta-BAs5, Sc-BAs5 and Ti-BAs5 are suitable for gas sensing and toxic gas monitoring, and have broad application prospects.

Effects of Nanowire Doping on Plasmon-Enhanced N2 Dissociation.

Doping a transition metal element into plasmonic systems can tune the optical properties of the system, which will potentially facilitate the plasmon-enhanced catalytic process. In this study, we applied the linear-response time-dependent density functional theory (LR-TDDFT) method with real-time electron dynamics and mean-field Ehrenfest dynamics methods to computationally investigate the effects of doping silver nanowires on plasmon-enhanced N2 dissociation. We calculated the absorption spectra for different doped systems, applied an external electric field to the system, and performed mean-field Ehrenfest dynamics to examine how plasmonic excitation will affect the N2 activation or dissociation. In addition, we also studied how the transition metal dopant affects the system's electronic structure and potential energy surface.

MB16 - (M=Sc, Y, La): Perfect Bowl-Like Boron Clusters.

The introduction of transition-metal doping has engendered a remarkable array of unprecedented boron motifs characterized by distinctive geometries and bonding, particularly those heretofore unobserved in pure boron clusters. In this study, we present a perfect (no defects) boron framework manifesting an inherently high-symmetry, bowl-like architecture, denoted as MB16 - (M=Sc, Y, La). In MB16 -, the B16 is coordinated to M atoms along the C5v-symmetry axis. The bowl-shaped MB16 - structure is predicted to be the lowest-energy structure with superior stability, owing to its concentric (2 π+10 π) dual π aromaticity. Notably, the C5v-symmetry bowl-like B16 - is profoundly stabilized through the doping of an M atom, facilitated by strong d-pπ interactions between M and boron motifs, in conjunction with additional electrostatic stabilization by an electron transfer from M to the boron motifs. This concerted interplay of covalent and electrostatic interactions between M and bowl-like B16 renders MB16 - a species of exceptional thermodynamic stability, thus making it a viable candidate for gas-phase experimental detection.

Investigation on preparation and tribology of poly ether ether ketone nanocomposite with transition metal doped zirconium dioxide

Composite materials are currently one of the most active study fields in modern technology. Their promising properties make them appropriate for a wide range of industrial applications including aerospace, automotive, construction, sports, bio-medical, and many more. These materials have amazing structural and mechanical features such as high strength-to-weight ratio, resistance to chemicals, fire, corrosion, and wear, as well as being cost-effective to produce. Poly-ether-ether-ketone (PEEK), a high performance polymeric materials, is increasingly being employed to replace metal elements in car engines and transmissions. Zirconium oxide (ZrO2), often known as zirconia, is a high-tech ceramic substance that is widely employed in the manufacture of various hard ceramics. The various physical and chemical properties of ZrO2 have been properly tailored for a given use by inserting transition metals (dopants) into the ZrO2 crystalline structure. In this work, the nano-composite of PEEK and transition metal doped Zirconium Dioxide is prepared. The composite was subsequently subjected to vital characterizations and tribological testing. The characterization validated the amalgam of modified ZrO2 with PEEK. The investigation has shown that PEEK reinforcement with modified ZrO2 has desired qualities for use in tribological applications

Computational investigation of hydrogen evolution reaction on transition metal-doped monolayer VSe2: A DFT approach

Density functional theory (DFT) was used to investigate the hydrogen evolution reaction (HER) on monolayer VSe2 doped by transition metal (TM) (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rh, Ir), in which Se or V is replaced by TM atoms (denoted as TM@Se or TM@V). Introducing transition metals (TMs) into the VSe2 monolayer can alter its electronic structure and catalytic properties. The choice of transition metal dopants and their configurations can significantly impact the catalytic performance of the material. It is illustrated that the TM@V systems are more stable than TM@Se configurations. Moreover, Co@V, Cu@V, Fe@V Zn@V and Cu@Se exhibit the lower ΔGH* values of 0.07, 0.09, 0.10, 0.12 and −0.1 eV, respectively, and ΔGH* values are very close to the ideal value of zero and are superior to precious metal Pt (ΔGH* = −0.1eV). Based on the scaling relationship of ΔGH* of H* intermediate, the volcano diagram and exchange current density diagram are established. It is predicted that Cu@V, Co@V, Fe@V, Zn@V structures could provide large exchange current of −1.6, −1.22, −1.7, −2 i0/(Acm−2), respectively.

Adsorption of toxic gases by Janus MoSeTe monolayers doped with transition metals and surface defects: A first-principles study

In recent years, two-dimensional TMDs materials have been proved to be high-performance gas sensor materials. Janus material is a member of the TMD family, and its gas sensing performance research is particularly important. Gas sensing mechanism of toxic gases on transition metal dichalcogenides based Janus MoSeTe monolayers is investigated using the density functional theory. Six transition metals are considered to modify the MoSeTe surface, by comparing the adsorption energies of the transition metal on both sides of the MoSeTe monolayer, it is found that the transition metal doping is more stable on the Se side. The MoSeTe surface is activated by transition metal modification, and the gas behavior is improved by transition metal modification, it is found that Ir-MoSeTe had the best sensing performance for NO2, Os-MoSeTe had the best sensing performance for CO, and Ru-MoSeTe had the best sensing performance for H2S, NO, and SO2. After that, we explain the adsorption mechanism of gas molecules by calculating the band structure, state density, differential charge density and work function of the adsorption structure, and the recovery time explain the reuse performance of the sensor. The results show that transition metal doped MoSeTe is a promising toxic gas sensor, which provides a theoretical basis for the development of new gas sensors.

Improved thermodynamic properties of (Sc, V, Ti, Fe, Mn, Co, and Ni) doped NaBH4 for hydrogen storage: First-principal calculation

Sodium borohydride (NaBH4) shows promise as a hydrogen storage option, but its substantial thermodynamic stability limits its practical application. Enhancing NaBH4 by introducing transition metals is an effective approach to enhance its hydrogen-related characteristics. Nevertheless, even with the most successful additives, the temperatures needed for hydrogen release remain too elevated, exceeding 400 °C, which hinders its practical utility. Using first-principles density functional, we have investigated the potential of sodium borohydride as a hydrogen-based fuel source. Our focus has been on the stable α-phase NaBH4 structure with space group symmetry F-43m (216), aiming to understand the impact of 3d transition metal (Sc, V, Ti, Fe, Mn, Co, and Ni) doping on the structural, electronic, and dehydrogenation properties of the NaBH4 system. Furthermore, the heat of formation and desorption temperature values obtained align with the stability and volumetric capacity criteria set by the U.S. Department of Energy (DOE). Our findings indicate that doping transition metals at the Na site weakens the B–H bonds, thereby enhancing the dehydrogenation performance. Among the various systems studied, those doped with Sc and Ti exhibit the most favorable dehydrogenation properties.

Enhanced thermoelectric figure of merit in graphene nanoribbons by creating a distortion and transition-metal doping

Thermoelectric (TE) materials have the exceptional ability to directly convert waste heat into electricity and theoretical studies-based guidance is an effective way to investigate high-performance nanostructured TE materials throughout a range of temperatures. Herein, we studied the influence of distortion and transition metal (TM) atoms (V, Cr, Co and Pt) on the electronic and TE properties of armchair graphene nanoribbons (AGNRs) at various temperatures. The results showed that TM-doping and distortion might significantly alter the electronic structure of AGNRs. The band gap and valence band convergence are reduced as a result of the synergistic effect. A higher TE figure of merit results from a combination of decreased heat conductivity and increased electrical conductivity brought about by the electronic structural change. This study proposes that by doping and distortion-induced TE characteristics engineering of AGNR, high-performance nanostructured TE materials may be produced that have a wide range of TE applications.

Selective Orbital Coupling: An Adsorption Mechanism in Single-Atom Catalysis.

Quantitative understanding of the chemisorption on single-atom catalysts (SACs) by their electronic properties is crucial for the catalyst design. However, the physical mechanism is still under debate. Here, the CO catalytic oxidation on single transition metal (i.e., Sc, Ti, V, Cr, Mn, Fe, Co, Ni) dopants is used as a theoretical model to explore the correlations between the characteristics of electronic structures and the chemisorption on SACs. For these metal dopants, their atomic d orbitals form several nondegenerate and localized electronic states that are found to be selectively coupled with the π* orbital of the adsorbed O2, which we defined as selective orbital coupling. Based on the selective orbital coupling, we find that the alignment between the selected d state and the π* state determines the bond strength, regardless of the electron occupation number of the selected d states; the electron transfer to form M-O bonding can be provided by the support. Such electron transfer can be related with the electronic metal-support interaction. We attribute the origin of the chemisorption mechanism to the coexistence of the localized orbital of the single transition metal and the continuous energy band of the Au support. Finally, we illustrate how this mechanism dominates the variation trend of the reaction barriers. Our results unravel a fundamental adsorption mechanism in SAC systems.

Unraveling Hydrogen Adsorption on Transition Metal-Doped [Mo3S13]2- Clusters: Insights from Density Functional Theory Calculations.

Molecular and dissociative hydrogen adsorption of transition metal (TM)-doped [Mo3S13]2- atomic clusters were investigated using density functional theory calculations. The introduced TM dopants form stable bonds with S atoms, preserving the geometric structure. The S-TM-S bridging bond emerges as the most stable configuration. The preferred adsorption sites were found to be influenced by various factors, such as the relative electronegativity, coordination number, and charge of the TM atom. Notably, the presence of these TM atoms remarkably improved the hydrogen adsorption activity. The dissociation of a single hydrogen molecule on TM[Mo3S13]2- clusters (TM = Sc, Cr, Mn, Fe, Co, and Ni) is thermodynamically and kinetically favorable compared to their bare counterparts. The extent of favorability monotonically depends on the TM impurity, with a maximum activation barrier energy ranging from 0.62 to 1.58 eV, lower than that of the bare cluster (1.69 eV). Findings provide insights for experimental research on hydrogen adsorption using TM-doped molybdenum sulfide nanoclusters, with potential applications in the field of hydrogen energy.

Entropy regulation in spinel oxide with narrowed band gap and lattice distortion toward high-temperature infrared radiation

Typical infrared (IR) radiation materials, such as spinel structure with transition metal doping, remain challenges on IR radiation performance and thermal stability. Inspired by manipulatable entropy with desired properties, (Mg1/5Co1/5Ni1/5Cu1/5Zn1/5)Al2O4 (5MAl2O4) with improved infrared radiation property and reduced thermal conductivity has been successfully synthesized. High-entropy strategy significantly narrows the band gap by impurity energy level formation, resulting in an improved 0.91 (0.78–2.5 μm). Simultaneously, 5MAl2O4 emerges site inversion (tetrahedral and octahedral sites) and lattice distortion which benefits the outstanding infrared emissivity of 0.94 (2.5–15 μm, measured at 800 °C). Furthermore, 5MAl2O4 reaches fairly low thermal conductivity of 2.1 W·m−1·K−1, 4–5 times decrease compared with MAl2O4 end members. The remarkable infrared emissivity and low thermal conductivity offer great potential in energy conservation and heat dissipation.