Effect Of Transition Metal Doping Research Articles

Charge Carrier Dynamics in Bandgap Modulated Covellite-CuS Nanostructures.

Copper Sulfide (CuS) semiconductors have garnered interest, but the effect of transition metal doping on charge carrier kinetics and bandgap remains unclear. In this study, the interactions between dopant atoms (Nickel, Cobalt, and Manganese) and the CuS lattice using spectroscopy and electrochemical analysis are explored. The findings show that sp-d exchange interactions between band electrons and the dopant ions, which replace Cu2+, are key to altering the material's properties. Specifically, these interactions result in a reduced bandgap by shifting the conduction and valence band edges and increasing carrier concentration. It is observed that undoped CuS nanoflowers exhibit a carrier lifetime of 2.16 ns, whereas Mn-doped CuS shows an extended lifetime of 2.62 ns. This increase is attributed to longer carrier scattering times (84 ± 5 fs for Mn-CuS compared to 53 ± 14 fs for CuS) and slower trapping (∼1.5 ps) with prolonged de-trapping (∼100 ps) rates. These dopant-induced energy levels enhance mobility and carrier lifetime by reducing recombination rates. This study highlights the potential of doped CuS as cathode materials for sodium-ion batteries and emphasizes the applicability of metal sulfides in energy solutions.

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.

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.

Photovoltaic infrared-photodetector based on perovskite Fe-BaTiO3 with further investigations for X-BTO (X = V, Cr, Mn, and Fe): A DFT study

Density functional theory (DFT) is exploited to comprehensively investigate the effects of transition metal doping on the electronic and optical properties of Barium Titanate (BTO). By incorporating vanadium (V), chromium (Cr), manganese (Mn), and iron (Fe) as dopants or substitutions within the BTO superlattice (Ba4Ti4-xO12), where x always represents a single atom, significant changes in the properties are observed. The structural investigation indicates a change in the cubic symmetry of BTO to tetragonal for V, Cr, and Fe doping, while Mn-BTO adopts an orthorhombic structure. The volume of the lattice structure decreases upon increasing the atomic number of the dopant elements, with the exception of orthorhombic Mn-BTO. In addition, the reduction in volume varies from 1.1 % to 2.1 % (excluding Mn), reaching 56.606 Å for Mn-BTO and 61.325 Å for Fe-BTO. While V-BTO and Mn-BTO exhibit weak metallic behavior, Cr and Fe-BTO display narrow band gaps of 0.974 and 0.579 eV, leading to a notable reduction in the band gap. Particularly Further, Fe-BTO demonstrates the highest absorption in the IR region due to its low band gap in addition to increasing the energy loss. Furthermore, the optical properties of these doped materials are characterized by low reflectivity (below 0.17) and a relatively high refractive index (in the range of 2–2.5) in the IR region, positioning them as promising candidates for efficient IR detectors and particularly Fe-BTO.

Enhancing charge transport and photoluminescence characteristics via transition metals doping in ITO thin films

Abstract This study presents the synthesis and characterization of pristine and transition metal (Co, Fe, and Zr)-doped indium tin oxide (ITO) thin films fabricated via RF magnetron sputtering. The effect of transition metal doping on ITO thin films properties was comprehensively examined using numerous spectroscopic and microscopic methods such as XRD, FTIR, and SEM coupled with EDX, UV–visible and PL spectroscopy, and four-probe and J–V measurements. The cubic crystal structure of the materials was confirmed through XRD spectroscopy, while FTIR results validated the existence of chemical bonds, signified by sharp peaks at 608 cm−1 and 667 cm−1 in the fingerprint region. SEM imaging revealed a granular-like agglomerated structure, with EDX confirming the elemental composition of the samples. The incorporation of Co, Fe, and Zr ions into ITO is aimed at improving photoconductivity and the optical bandgap, with the ultimate objective of enhancing performance in photovoltaic applications. Our findings showed a significant decrease in optical transmission in the visible spectrum. The bandgap also experienced a minor decrease from 3.67 eV to 3.53 eV. Analysis of the photoluminescence spectra exhibited the majority of emission peaks in the UV region, ascribed to electronic transitions occurring via band-to-band and band-to-impurity interactions within the ITO. Electrical measurements indicated lower resistance, higher current flow, and increased carrier concentration in transition metals–doped ITO compared to the undoped ITO, with Zr-doped ITO exhibiting the highest conductivity and optimal charge flow among all dopants. These promising findings in terms of optical, structural, and electrical attributes signal the potential of these materials for photovoltaic system applications.

Enhanced Catalytic Soot Oxidation over Co-Based Metal Oxides: Effects of Transition Metal Doping.

A series of Co-M (M = Fe, Cr, and Mn) catalysts were synthesized by the sol-gel method for soot oxidation in a loose contact mode. The Co-Fe catalyst exhibited the best catalytic activity among the tested samples, with the characteristic temperatures (T10, T50, and T90) of 470 °C, 557 °C, and 602 °C, respectively, which were 57 °C, 51 °C, and 51 °C lower than those of the CoOx catalyst. Catalyst characterizations of N2 adsorption-desorption, X-ray diffraction (XRD), X-ray photo-electron spectrometry (XPS), and the temperature programmed desorption of O2 (O2-TPD) were performed to gain insights into the relationships between the activity of catalytic soot oxidation and the catalyst properties. The content of Co2+ (68.6%) increased due to the interactions between Co and Fe, while the redox properties and the relative concentration of surface oxygen adsorption (51.7%) were all improved, which could significantly boost the activity of catalytic soot oxidation. The effects of NO and contact mode on soot oxidation were investigated over the Co-Fe catalyst. The addition of 1000 ppm of NO led to significant reductions in T10, T50, and T90 by 92 °C, 106 °C, and 104 °C, respectively, compared to the case without the NO addition. In the tight contact mode, the soot oxidation was accelerated over the Co-Fe catalyst, resulting in 46 °C, 50 °C, and 50 °C reductions in T10, T50, and T90 compared to the loose contact mode. The comparison between real soot and model Printex-U showed that the T50 value of real soot (455 °C) was 102 °C lower than the model Printex-U soot.

Effects of transition metal doping on the properties and catalytic performance of ZSM-5 zeolite catalyst on ethanol-to-hydrocarbons conversion

In this study, the effects of transition metal-doping on the physicochemical properties and catalytic performance of HZSM-5 catalysts for the conversion of ethanol to hydrocarbons are investigated using experimental data and secondary data from the literature. Hydrothermally synthesized novel ZSM-5 catalysts were modified with different concentrations (0.5 and 10 wt%) of transition metals (Co, Fe, Ni). Characterizations, including X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, particle size distribution, N2 adsorption and NH3 temperature-programmed desorption, revealed the changes in catalyst properties. The introduction of transition metals affected the surface area, particle size and acidity without altering the MFI structures. In particular, a reduction in surface area was observed, ranging from 2.6 to 23 %, corresponding to the different metal loading of 0.5–10 wt% compared to the surface area of the pure catalyst (397.5 m²/g). In addition, metal-doping led to an increase in Lewis acid sites, accompanied by a decrease in strong acid sites. Catalytic evaluation at 350 °C and a space velocity of 12 h−1 showed improved performance in metal-doped ZSM-5 catalysts, which exhibited high selectivity towards fuel-range hydrocarbons, compared to the unmodified catalyst. Catalysts with low metal doping showed optimal catalytic activity, while high metal doping led to increased coke deposition and deactivation of the catalyst due to an increased concentration of strong acids. These results underline the suitability of metal-modified ZSM-5 for hydrocarbon reactions and provide valuable insights for the optimization of catalysts for ethanol conversion to fuel-range hydrocarbons.

Microkinetic Modeling of CO2 Hydrogenation to Formic Acid on Transition Metal Doped Ni(111) Surface

The direct conversion of carbon dioxide (CO2) into valuable chemicals plays a crucial role in mitigating climate change and fostering a sustainable future. To facilitate this process, identifying an effective catalyst is of utmost importance. This study focuses on investigating the potential of nickel-based surfaces as catalysts for the direct hydrogenation of CO2 into formic acid (HCOOH), a valuable chemical with applications as a fuel and hydrogen storage. Several nickel surface models were considered, including pristine Ni(111) and Ni(111) surfaces doped with Cu, Pd, Pt, and Rh metals. Through a microkinetic investigation, we examined the reaction kinetics and determined the rate-determining steps on the Ni(111) surfaces. By elucidating the reaction pathways and characterizing the reaction intermediates, we gained comprehensive insights into the fundamental processes involved in CO2 hydrogenation to HCOOH. This knowledge is crucial for the rational design and optimization of catalysts, enabling the development of highly active catalysts for CO2 conversion. Our study revealed insights into the effect of transition metal doping on the catalytic activity of Ni(111) surfaces. Among the investigated dopants, we found that the addition of Pt in the first layer of Ni(111) surface yielded the best turnover frequency (TOF) for the CO2 conversion to HCOOH. The Pt dopants induced unique electronic properties in the Ni(111) surface, resulting in a reduced activation barrier for key reaction intermediates. This effect contributed to a more efficient conversion of CO2 to HCOOH.

Synergistic improvement in electrochemical performance of Cr-doped MoS2/CuCo2S4 binary composite for hybrid supercapacitors

The synergistic effect of transition metal doping and composite formation can be imperative to improve the limited conductivity and inferior cyclic stability of MoS2 for supercapacitors. In this work, firstly, the impact of Cr-doping on the electrochemical activity of MoS2 has been discussed. Afterwards, the optimized Cr-doped MoS2 (CrMS-5) sample has been combined with CuCo2S4 (CCS) to further enhance its charge storage ability and cyclic stability. The CrMS-5/CCS composite delivers tremendous electrochemical activity as an electrode with a specific capacity of approximately 1324.08 C g−1 at 4 A g−1. The outstanding performance of the doped binary composite is on account of the synergism between doping and composite formation that results in increased conductivity and numerous redox active sites for charge storage. Furthermore, a symmetric supercapacitor device (SSC) has been fabricated using a CrMS-5/CCS electrode. It attains a high energy density of 46.63 Wh kg−1 corresponding to 1 kW kg−1 of power and exhibits remarkable cyclic stability of 81% for up to 5,000 cycles. The device illuminates a star-shaped LED panel of 12 red LEDs for 30 min. Thus, the above outcomes demonstrate the superiority of the doped MoS2-based composites for high-energy symmetric supercapacitors.

Modulating electronic structure of Ni/carbon spherical nano-superstructures through transition metal-doping as highly efficient catalysts for hydrogen evolution reaction

The development of low-cost, high-performance electrocatalysts for hydrogen precipitation reactions is the key to solving the energy crisis. Metal organic framework (MOFs) with metal centers and organic ligands are one of the ideal materials for the preparation of non-precious metal carbon-based HER electrocatalysts. In this work, a series of transition metal-doped nano-superstructures carbon-based materials NiMC (M = Fe, Co, Cu) were designed and prepared by introducing different transition metal atoms using Ni-MOF as precursors. And the effect of transition metal doping on the electrocatalytic hydrogen precipitation performance of Ni-MOF has been systematically investigated. Nitrogen adsorption tests have shown that the NiFeC catalyst has the highest specific surface area. The overpotential was only 69 mV at a current density of 10 mA cm−2 in an alkaline electrolyte and exhibited excellent stability. Density functional theory (DFT) calculations show that the electronic interactions between Fe and Ni are tuned after Fe atom doping, which optimizes the hydrogen adsorption energy leading to the excellent HER catalytic performance of NiFeC.

Effect of transition metal doping on the photoelectric structure of single layer NbS2 under defects

Excellent semiconductors and novel optical properties are the first criteria for nanomaterial technology. In this paper, the S-atom defect is applied to 1T-NbS2 for the first time, and doping atoms are introduced. The concentration of doping atoms is 3.84% and 4% under the two types of defects. Finally, the metallic properties of NbS2 were weakened successfully, and the highest indirect band gap of 0.27[Formula: see text]eV was induced, which gradually transformed into a brand-new semiconductor material. In addition, partially composite systems exhibit excellent electromagnetic storage, polarizability, and infrared light absorption, showing high reflectivity in the visible and low-frequency UV regions, which can be used to make blackout lenses and reflective coatings. Cd composite systems can be used as a new type of conducting semiconductor for all kinds of equipment.

Effect of transition metal doping on the photoelectric effect of monolayer NbS2 under strain: First-principles calculations

In this paper, the effects of transition metal doping on the electronic structure of monolayer NbS2 were studied through the first principles. The electronic structure changes caused by doping transition metal (TM) atoms were recorded, including the energy band, the density of states, binding energy, and optical properties. Studies show that all doping systems are metal. Still, under strain regulation, some doping systems offer an indirect bandgap; NbS2 transforms into a narrow bandgap diluted semiconductor and can improve the activity. Doping atoms lead to [Formula: see text] type doping in NbS2. Regarding optical properties, IVB group metals are selected as the typical dopant of three periods. Composite NbS2 has excellent reflector characteristics and can be applied to infrared and ultraviolet regions. The spectral response and electromagnetic wave absorption range of low-energy areas are also improved. This study effectively solves the problem of impurity states introduced by doping and provides a solution for the doping modification of monolayer NbS2, which will lay a foundation for nanoelectronics.

Optical bandgap variation and photo-Fenton property evolution in Fe-doped Bi2YO4Cl

The current study addresses the existing research gap on the effects of transition metal doping in layered Bi2YO4Cl and searches for a new visible light photocatalyst in the bismuth-based oxychloride system. The extent of Fe substitution in place of Y in Bi2YO4Cl and its consequences on the structure, optical, and catalytic properties have been examined by synthesizing the samples using a solution combustion method. Nearly 20 mol% of Fe could be introduced in a monophasic layer structural arrangement. The Fe-containing samples have also been characterized by electron microscopic and vibrational spectroscopic techniques. The optical absorbance shifted to the visible region with the Fe inclusion, and the bandgap decreased from 2.40 eV (pristine) to 1.77 eV (20 mol % Fe-substituted). XPS analysis of the Fe-containing sample indicated that Fe existed majorly in the III oxidation state with traces of the II oxidation state. The photo-Fenton function of Bi2Y1-xFexO4Cl (x = 0.10 and 0.20) for the oxidative degradation of RhB and MB dye molecules under LED illumination has been demonstrated. From scavenger experiments, OH• radicals and holes have been identified as the reactive oxidation species (ROS) involved in these reactions. The catalyst showed recyclability and structural integrity.

Revealing the effects of transition metal doping on CoSe cocatalyst for enhancing photocatalytic H2 production

Having an insight into the optimizations of intrinsic properties of cocatalysts via doping foreign atoms to promote solar-driven water splitting into hydrogen (H2) energy conversion is increasingly important, but it remains a challenging scheme. Herein, zero-dimensional/one-dimensional (0D/1D) structured TMCoSe/CdS0.95Se0.05 was successfully synthesized through a two-pot hydrothermal treatment. Experimental results show that the FeCoSe/CdS0.95Se0.05 photocatalyst exhibits the most excellent photocatalytic H2 evolution performance (513.76 μmol h−1), which is 36.6 times and 2.0 times higher than that of CdS0.95Se0.05 and the optimal CoSe/CdS0.95Se0.05, respectively. In addition, photochemical and photoluminescence results reveal that the FeCoSe/CdS0.95Se0.05 sample shows the most rapid carrier dynamics among all samples. Theoretical calculations demonstrate that the excellent activity of FeCoSe/CdS0.95Se0.05 nanocomposite can be attributed to the formation of Schottky-type heterojunction between semi-metallic FeCoSe cocatalyst and CdS0.95Se0.05, which can enhance the efficiency of charge carrier separation and utilization, thus promoting the H2-generation performance.

Formulating a heterolytic cleavage process of water on Ni3N nanosheets through single transition metal doping for ultra-efficient alkaline hydrogen evolution

The effect of transition metal doping on the HER performance of Ni3N was evaluated by experiments and DFT.

Defects and oxygen vacancies modified properties of transition metal doped Ce0.95X0.05O2 (X = Fe, Co, Ni) nanoparticles

In this study, pure and transition metal doped (TM = Fe, Co, and Ni), cerium oxide nanoparticles have been synthesized by the co-precipitation techniques. Rietveld refined X-ray diffraction (XRD) patterns affirm the monophase nature with cubic symmetry having an Fm3m space group and crystalline size varies in the range of 9–14 nm calculated by Debye Sherer's formulation. The morphological study has been done by scanning electron microscope (SEM) technique anticipated that agglomerated grains symmetry with the typical grain size distribution varies from 45 to 52 nm. The effect of transition metal doping on bending/stretching vibrational modes has been effectively investigated by FTIR analysis. The strong absorbance edge was seen in the UV region and shifted in the red region with the doping of transition metal ions. The tauc’s plot of UV–vis absorption uncovers the bandgap decreased from 2.87 eV to 2.42 eV on transition metal doping. The photoluminescence spectroscopy (PL) technique was used to investigate the presence of oxygen vacancies and intrinsic defects in the host CeO2 lattice when doped with transition metal ions. These imperfections induce the lattice disorder and shift in the energy bandgap from the UV to the visible region of the spectrum by affecting its electronic transitions. The CIE chromaticity coordinates of pure and transition metal doped compounds observed in the blue region might be applicable in display devices. In this manner, these materials can be fascinating for tuneable electrical and optical devices.

Designing High-Performance Se-Decorated Edges of MoSe2 Nanostripes for the Hydrogen Oxidation Reaction: Effect of Transition Metal Doping

Designing High-Performance Se-Decorated Edges of MoSe₂ Nanostripes for the Hydrogen Oxidation Reaction: Effect of Transition Metal Doping

Effects of transition metal doping on CsGeBr3 perovskite: First-principles study

Metal halide perovskites have shown the most promising results as the light-harvesting section of photovoltaics and opto-electronic devices. Among the non-toxic halide perovskites, CsGeBr3 was found to be the best candidate for opto-electronic applications; however, it is understood that the efficiency of CsGeBr3 can be further increased with the insertion of transition metals as dopants. In this article, the first-principles density functional theory calculations are used to predict the mechanical, structural, electronic, and optical properties of pristine, Ni-doped, Mn-doped, and Fe-doped CsGeBr3 with 12.5% of doping concentration. All the doped materials are found to be ferromagnetic and mechanically stable. They have finite magnetization values. The optical absorption edge in all the doped materials shows that they have additional peaks within the large emission range of solar radiation, which makes them more suitable than the pristine material for photovoltaics and opto-electronic applications. Among the doped materials, Mn-doped and Fe-doped CsGeBr3 have comparably higher absorption peaks and are almost identical in shape. The electronic bandgap is smaller than the pristine structure in the case of Fe-doped CsGeBr3 and larger for Ni and Mn-doped CsGeBr3. These combinational analyses lead to the decision that, among the non-toxic, inorganic perovskite materials, Fe-doped CsGeBr3 is better suited for the use in opto-electronic applications.

Fabrication of highly stabilized Zr Doped g-C3N4/Nb2O5 heterojunction and its enhanced photocatalytic performance for pollutants degradation under visible light irradiation

A series of Zr doped g-C3N4/Nb2O5 photocatalysts with high visible light response and strong redox properties were synthesized for wastewater treatment under visible light, which achieved the synergistic effect of transition metal doping and semiconductor compounding. The doping of Zr promoted charge transfer due to the formation of Schottky barrier. As an electronic medium, Zr was devoted to formating the Z-scheme heterojunction between g-C3N4 and Nb2O5, which effectively improved the redox ability of the catalyst as well as promoted the separation of photogenerated electrons and holes in semiconductors. The morphology, chemical structure, optical and electronic properties of Zr/g-C3N4/Nb2O5 photocatalysts were well characterized. Compared with monomeric g-C3N4, the as-prepared Zr/g-C3N4/Nb2O5 exhibited improved visible light response and enhanced separation efficiency of photogenerated carriers as a result of the synergistic effect of ion doping and semiconductor compounding. Subsequently, the activity of organic pollutant degradation were tested using as-prepared Zr/g-C3N4/Nb2O5 under the representative organic pollutants methylene blue (MB) and levofloxacin (LF) as the targets. The Zr/g-C3N4/Nb2O5 showed efficient photocatalytic activity toward degrading dye wastewater and pharmaceutical wastewater under visible light irradiation (λ＞410 nm) comparing with bare g-C3N4 and Zr/g-C3N4. The content of Zr and Nb2O5 has a crucial effect on catalyst activity, and the Zr/g-C3N4/Nb2O5 with 5 at% Zr and 4 wt% Nb2O5 was of the best photocatalytic activity, which degraded 98.5% of MB in 120 min for visible light irradiation. The excellent performance of Zr/g-C3N4/Nb2O5 is mainly due to the Z-scheme charge transfer mode.