Effects Of Different Dopants Research Articles

Enhancing the Mn Redox Kinetics of LiMn0.5Fe0.5PO4 Cathodes Through a Synergistic Co-Doping with Niobium and Magnesium for Lithium-Ion Batteries.

The concerns on the cost of lithium-ion batteries have created enormous interest on LiFePO4 (LFP) and LiMn1-xFexPO4 (LMFP) cathodes However, the inclusion of Mn into the olivine structure causes a non-uniform atomic distribution of Fe and Mn, resulting in a lowering of reversible capacity and hindering their practical application. Herein, a co-doping of LMFP with Nb and Mg is presented through a co-precipitation reaction, followed by a spray-drying process and calcination. It is found that LiNbO3 formed with the aliovalent Nb doping resides mainly on the surface, while the isovalent Mg2+ doping occurs into the bulk of the particle. Full cells assembled with the co-doped LMFP cathode and graphite anode demonstrate superior cycling stability and specific capacity, while maintaining good tap density, compared to the undoped or mono-doped (only with Nb or Mg). The co-doped sample exhibits a capacity retention of 99% over 300 cycles at a C/2 rate. The superior performance stems from the enhanced ionic/electronic transport facilitated by Nb coating and the enhanced Mn2+/3+ redox kinetics resulting from bulk Mg doping. Altogether, this work reveals the importance of the synergistic effect of different dopants in enhancing the capacity and cycle stability of LMFP.

Surface property tuning of LaCr0.7Ni0.3O3 based perovskite catalysts enable efficient operation of SOFCs on liquid fuels

A-site Sr or Ca substituted perovskite LaCr0.7Ni0.3O3 (LSCN, LCCN) are prepared in this work as catalysts of simulated diesel fuel (N-hexadecane) steam reforming for the on-board hydrogen supplement of solid oxide fuel cells (SOFCs). The effect of different dopants on active metals dispersion and surface properties on catalyst performance is analyzed. The results of the investigation reveal that LCCN possesses the highest catalytic activity coupled with exceptional stability, achieving full fuel conversion at WHSV = 5 mL/g·h, S/C = 3.0, and 750 °C and keeping stable for 200 h, thereby emerging as a potential candidate for liquid fuel processing. SEM, H2-pulse chemisorption and XPS results confirm that the excellent performance is due to the high metal dispersion and steam activation capacity. The poor catalytic performance observed in LSCN is primarily attributed to the presence of Sr segregation and the formation of the SrCrO4 second phase. Sr segregation decreases the steam activation ability of the catalyst as confirmed by XPS. DFT calculation also shows that Sr dopant and Sr segregation decrease the exsolution trend of metal Ni in the perovskite matrix, leading to poor metal dispersion. A simulated reforming gas is used in SOFC and the cell can keep stable for 120 h at a discharging current density of 0.4 A/cm2. This study analyzes the difference between Ca and Sr dopants, and reveals the detrimental effect of Sr segregation, which could enlighten the effect of surface tunning on the performance of perovskite catalysts.

Synergistic Effect of P and Co Dual Doping Endows CuNi with High-Performance Hydrogen Evolution Reaction.

The rational design of highly active and durable non-noble electrocatalysts for hydrogen evolution reaction (HER) is significantly important but technically challenging. Herein, a phosphor and cobalt dual doped copper-nickel alloy (P, Co-CuNi) electrocatalyst with high-efficient HER performance is prepared by one-step electrodeposition method and reported for the first time. As a result, P, Co-CuNi only requires an ultralow overpotential of 56mV to drive the current density of 10mA cm-2, with remarkable stability for over 360h, surpassing most previously reported transition metal-based materials. It is discovered that the P doping can simultaneously increase the electrical conductivity and enhance the corrosion resistance, while the introduction of Co can precisely modulate the sub-nanosheets morphology to expose more accessible active sites. Moreover, XPS, UPS, and DFT calculations reveal that the synergistic effect of different dopants can achieve the most optimal electronic structure around Cu and Ni, causing a down-shifted d-band center, which reduces the hydrogen desorption free energy of the rate-determining step (H2O + e- + H* → H2 + OH-) and consequently enhances the intrinsic activity. This work provides a new cognition toward the development of excellent activity and stability HER electrocatalysts and spurs future study for other NiCu-based alloy materials.

Co, Ni and Cu-doped Ca2Fe2O5-based oxygen carriers for enhanced chemical looping hydrogen production

Oxygen carrier determines the output characteristics of the chemical looping cycle reaction and is a key factor affecting the chemical looping hydrogen production (CLH) process. In this work, the effect of different dopants (Co, Ni and Cu) on Ca2Fe2O5 brownmillerite-type oxygen carriers and the feasibility of low doping were investigated in an attempt to improve CO conversion and hydrogen yield in the CLH reaction. The redox activity of the transition metal doped oxygen carriers was significantly enhanced. The fuel conversion of CaFeNi was increased to 1.29 times. The average hydrogen yield of CaFeCo was as high as 102.20 mL/g, which was 1.58 times that of CaFe. In addition, density functional theory calculations show that metal-doped Ca2Fe2O5 reduced the energy of oxygen vacancy formation, but they bore a significant energy barrier in the formation of hydrogen molecules. These findings may provide ideas for the modification of oxygen carriers for the CLH process.

Effect of Doping Process Route on LiNiO2 Cathode Active Material Properties

One way to obtain higher energy densities in lithium-ion batteries is to increase the nickel content in lithium nickel-cobalt-manganese oxide (NCM) cathode active materials (CAMs), ultimately approaching LiNiO2 (LNO). At the same time, a higher nickel content and specific capacity comes with more severe degradation of the CAM during battery cycling. Doping of the CAM with additional elements is a common approach to increase structural stability. For any CAM, comparisons of different dopants with each other and with undoped references are therefore commonly found in the literature.[1,2] In some cases, the effect of different dopants on the CAM particle morphology is also reported.[3,4] However, the influence of the process route of dopant introduction is rarely discussed. The most common ways are either the co-calcination of dopant source, lithium source and CAM precursor (pCAM), or the co-precipitation of dopant ions during pCAM precipitation. Impregnating the pCAM surface with a suspension of smaller dopant particles or a dopant solution, followed by solvent removal, can provide better dopant distribution in case of low dopant ion mobility or phase separation tendencies during calcination.Building on the previous finding that the primary particle morphology is the determining factor of LNO performance,[5,6] in this work, the primary particle morphology, but also dopant distribution in a series of 0.25 mol% Zr-doped LNO obtained from the three different process routes co-calcination, impregnation and co-precipitation, is investigated. This low dopant concentration is common in commercial CAM, as thus the content of redox-active transition metal content remains high to provide maximal energy density. Zr also tends to phase separate in the form of Li2ZrO3 at high concentrations, which is this way avoided as much as possible, since the chosen concentration is below the solubility limit of Zr in the LNO bulk. In this comparison, it is found that not the dopant itself, but the process route of its introduction affects the primary particle morphology of LNO, likely explained by the initial dopant localization early in the calcination.Differences in electrochemical performance, both in coin cells and long-term cycled pouch cells, as well as in specific capacitance and gas evolution are then also found to be due not to the dopant, as one would initially assume in comparisons of doped and undoped materials, but to the effect of the process route on LNO primary particle morphology.

Transition Metal-Doped SnO2 As Versatile Battery Electrode Material

Tin oxide-based materials have been intensively investigated as alternative anodes for lithium-ion batteries due to their high specific capacity, environmental friendliness, non-toxicity, and ease of handling. However, the initial formation of Li2O upon lithiation is essentially irreversible, which has a severe effect on the first cycle Coulombic efficiency and the reversibly achievable capacity in general.[1]It has been shown that the incorporation of transition metal dopants can address this issue, as it enables the reversible formation and reformation of Li2O.[2] The choice of the dopant, however, plays a critical role for the long-term cycling stability, rate capability, and eventual energy density of the resulting lithium-ion cells.[3] While there have been intensive studies published already on the effect of different dopants for Li-ion battery applications, targeting an optimized combination for achieving enhanced cycling performance[3] and an in-depth understanding of the reaction mechanism,[4,5] the investigation as Na-ion battery active material has not been reported so far. In fact, our results show that the reaction mechanism is fundamentally different, while the incorporation of transition metal dopants is still favorable for the eventual charge storage via sodium cations. The resulting insights into the de-/sodiation mechanism are anticipated to enable the development of further enhanced electrode active materials for sodium-ion batteries and, thus, support the recent success of this alternative battery technology. Reference s [1] D. Bresser, S. Passerini, B. Scrosati, Energy Environ. Sci. 2016, 9, 3348.[2] Y. Ma, Y. Ma, G. Giuli, T. Diemant, R. J. Behm, D. Geiger, U. Kaiser, U. Ulissi, S. Passerini, D. Bresser, Sustain. Energy Fuels 2018, 2, 2601.[3] A. Birrozzi, J. Asenbauer, T. E. Ashton, A. R. Groves, D. Geiger, U. Kaiser, J. A. Darr, D. Bresser, Batter. Supercaps 2020, 3, 284.[4] J. Asenbauer, A. Wirsching, M. Lang, S. Indris, T. Eisenmann, A. Mullaliu, A. Birrozzi, A. Hoefling, D. Geiger, U. Kaiser, R. Schuster, D. Bresser, Adv. Sustain. Syst. 2022, 6, 2200102.[5] A. Birrozzi, A. Mullaliu, T. Eisenmann, J. Asenbauer, T. Diemant, D. Geiger, U. Kaiser, D. Oliveira de Souza, T. E. Ashton, A. R. Groves, J. A. Darr, S. Passerini, D. Bresser, Inorganics 2022, 10, 46.

Effect of different dopants on the structural and physical properties of In2S3 thin films: a review

Effect of different dopants on the structural and physical properties of In2S3 thin films: a review

Nb, Ta and Hf – The tri-dopant tournament for the enhancement of TiO2 photochromism

TiO2 quantum dot (QD) size nanoparticle colloids have shown tremendous photochromic response. Here we show that the of the photochromic response of TiO2 QDs can be further enhanced by doping. Our synthesis approach allows to reach high nominal doping level by substituting up to 20 % of Ti in TiO2 without phase segregation simultaneously keeping particles in ultra-small. We compare the effect of different dopants (Nb5+, Hf4+ and Ta5+) on photochromic properties of TiO2 QDs. We show all dopants in study enhance the response kinetics and total transmittance change. From all three dopants, Nb5+ provides strongest response and fastest coloration while Hf4+ doped TiO2 QDs exhibit fastest recovery when the UV light is off. The presented insight in photochromic properties of doped TiO2 QDs will allow to develop photochromic devices and materials with better performance.

Upconversion Luminescence through Cooperative and Energy-Transfer Mechanisms in Yb3+ -Metal-Organic Frameworks.

Lanthanide-doped metal-organic frameworks (Ln-MOFs) have versatile luminescence properties, however it is challenging to achieve lanthanide-based upconversion luminescence in these materials. Here, 1,3,5-benzenetricarboxylic acid (BTC) and trivalent Yb3+ ions were used to generate crystalline Yb-BTC MOF 1D-microrods with upconversion luminescence under near infrared excitation via cooperative luminescence. Subsequently, the Yb-BTC MOFs were doped with a variety of different lanthanides to evaluate the potential for Yb3+ -based upconversion and energy transfer. Yb-BTC MOFs doped with Er3+ , Ho3+ , Tb3+ , and Eu3+ ions exhibit both the cooperative luminescence from Yb3+ and the characteristic emission bands of these ions under 980 nm irradiation. In contrast, only the 497 nm upconversion emission band from Yb3+ is observed in the MOFs doped with Tm3+ , Pr3+ , Sm3+ , and Dy3+ . The effects of different dopants on the efficiency of cooperative luminescence were established and will provide guidance for the exploitation of Ln-MOFs exhibiting upconversion.

Upconversion Luminescence through Cooperative and Energy‐Transfer Mechanisms in Yb3+‐Metal‐Organic Frameworks

AbstractLanthanide‐doped metal–organic frameworks (Ln‐MOFs) have versatile luminescence properties, however it is challenging to achieve lanthanide‐based upconversion luminescence in these materials. Here, 1,3,5‐benzenetricarboxylic acid (BTC) and trivalent Yb3+ ions were used to generate crystalline Yb‐BTC MOF 1D‐microrods with upconversion luminescence under near infrared excitation via cooperative luminescence. Subsequently, the Yb‐BTC MOFs were doped with a variety of different lanthanides to evaluate the potential for Yb3+‐based upconversion and energy transfer. Yb‐BTC MOFs doped with Er3+, Ho3+, Tb3+, and Eu3+ ions exhibit both the cooperative luminescence from Yb3+ and the characteristic emission bands of these ions under 980 nm irradiation. In contrast, only the 497 nm upconversion emission band from Yb3+ is observed in the MOFs doped with Tm3+, Pr3+, Sm3+, and Dy3+. The effects of different dopants on the efficiency of cooperative luminescence were established and will provide guidance for the exploitation of Ln‐MOFs exhibiting upconversion.

The effect of different dopants and their positions on the magnetic properties of an armchair antimonene nanoribbon: comprehensive theoretical investigation

In this work, using density functional theory, we have studied the magnetic properties of an armchair antimonone nanoribbon doped with transition metal (TM) atoms (Mn, Fe, Co, Ni, V, Cr) in various positions and different number of impurity atoms. The results show that the investigated magnetic properties, such as spin band gap, spin polarization and magnetic moment vary with type and distance from the edge of the ribbon and the number of impurities. The obtained values of magnetic moment reveal, Mn-doped nanoribbons have greater magnetization than Fe, Cr, V, Ni and Co doped ones. Also, spin polarization with significant values is observed in Mn and Fe doped structures. Our calculated spin currents demonstrate that introducing of TM dopants leads to efficient separation of spin up and down currents. Interestingly, nanoribbons with Mn, Cr and V dopants show high spin filter efficiency in a wide range of voltages. Thus, it seems that our results prepare a promising way to nanoscale spintronic devices.

Theoretical Investigation of the Effect of Different Dopants and Their Positions on the Magnetic Properties of an Armchair Graphene Nanoribbon

Theoretical Investigation of the Effect of Different Dopants and Their Positions on the Magnetic Properties of an Armchair Graphene Nanoribbon

An Investigative Study on the effect of Dopants on Manganese Based Mixed Nano Ferrites Synthesized through Sol-Gel Method

The present article investigates the effect of different dopants on manganese based mixed nano ferrites synthesized through sol-gel method.MnF, MnCoF and MnCoMgF (MnFe2O4, Mn0.5Co0.5Fe2O4andMn0.5Co0.25Mg0.25Fe2O4) were synthesized by Sol-gel method. The structural, magnetic and optical properties of the samples were analysed through XRD(X-RayDiffractometer), VSM (Vibrating Sample Magnetometer,) and UV-Visible Spectroscopy. The phase identification and lattice parameter determination were carried out by using X-RayDiffraction and hence the crystallite size and X-Ray density were calculated. Peaks (220), (311), (400), (511), and (440) were obtained from the XRDpattern of the samples, which confirmed their single-phase cubic spinel structure. It was observed that because of the large ionic radius of Co2+ (0.745 Å) ions as compared to that of Fe3+ (0.645 Å) ions, lattice parameter of MnCoF increased in comparison with that of MnF but, the substitution of Mg2+ to MnCoF sample decreased the lattice constant. By investigating the hysteresis loops produced by the samples in the VSM analyses, it was found that the MnF have low coercivity and moderate saturation magnetization amongst the three. The substitution of Mg2+ in MnCoF sample decreased the value of saturation magnetization. UV-Visible analysis was used to determine bandgap energy of three samples.From the Tauc plot, we can observe bandgap energies of 3.202 eV, 3.180 eV and 3.239 eV, for MnF, MnCoF and MnCoMgF respectively.On substituting with the Co2+ in MnF the band gap of sample decreases indicating quantum confinement phenomenon.When substitution was done both Co2+ and Mg2+, the band gap energy value increases.

Polyaniline Synthesized by Different Dopants for Fluorene Detection via Photoluminescence Spectroscopy.

The effects of different dopants on the synthesis, optical, electrical and thermal features of polyaniline were investigated. Polyaniline (PANI) doped with p-toluene sulfonic acid (PANI-PTSA), camphor sulphonic acid (PANI-CSA), acetic acid (PANI-acetic acid) and hydrochloric acid (PANI-HCl) was synthesized through the oxidative chemical polymerization of aniline under acidic conditions at ambient temperature. Fourier transform infrared light, X-ray diffraction, UV-visible spectroscopy, field emission scanning electron microscopy, photoluminescence spectroscopy and electrical analysis were used to define physical and structural features, bandgap values, electrical conductivity and type and degree of doping, respectively. Tauc calculation reveals the optical band gaps of PANI-PTSA, PANI-CSA, PANI-acetic acid and PANI-HCl at 3.1, 3.5, 3.6 and 3.9 eV, respectively. With the increase in dopant size, crystallinity is reduced, and interchain separations and d-spacing are strengthened. The estimated conductivity values of PANI-PTSA, PANI-CSA, PANI-acetic acid and PANI-HCl are 3.84 × 101, 2.92 × 101, 2.50 × 10−2, and 2.44 × 10−2 S·cm−1, respectively. Particularly, PANI-PTSA shows high PL intensity because of its orderly arranged benzenoid and quinoid units. Owing to its excellent synthesis, low bandgap, high photoluminescence intensity and high electrical features, PANI-PTSA is a suitable candidate to improve PANI properties and electron provider for fluorene-detecting sensors with a linear range of 0.001–10 μM and detection limit of 0.26 nM.

Annealing-Induced Off-Stoichiometric and Structural Alterations in Ca2+- and Y3+-Stabilized Zirconia Ceramics.

In the current study, high-temperature stability was investigated in two types of zirconia ceramics stabilized with two different additives, namely, calcia and yttria. The evolutions of structure and oxygen-vacancy-related defects upon annealing in air were investigated as a function of temperature by combining X-ray diffractometry with Raman, X-ray photoelectron and cathodoluminescence spectroscopies. We systematically characterized variations in the concentration of oxygen vacancies and hydroxyl groups during thermal treatments and linked them to structural alterations and polymorphic transformation. With this approach, we clarified how the combined effects of different dopants and temperature impacted on structural development and on the thermal stability of the oxygen-vacancy-related defect complex.

Improved redox performance of Fe2O3/Al2O3 oxygen carrier via element doping in chemical looping combustion

In chemical looping combustion, iron-based oxygen carriers often experienced serious phase segregation, which reduced the cyclic stability of the oxygen carriers. In this work, Fe2O3/Al2O3 (FA) was doped with different metals (Sr, La and Ce) to improve the redox performance during cyclic reactions. The mechanism of dopants on FA was explored by experimental research and characterization analysis. The promotion effect of different dopants on the redox performance of FA followed the sequence: Sr > La > Ce. It was shown that the deactivation of Ce-FA and La-FA was obvious in 20 cycles. The results of 100 successive cycles indicated that the surface structure of Sr-FA remained stable and no sintering was observed. The Sr-FA achieved stable oxygen carrying capacity (4%) in 100 redox cycles. The characterization results indicated that the addition of Sr could effectively increase the concentration of oxygen vacancies, thus inhibiting the phase segregation of FA. The enrichment degree of surface Fe of FA, Sr-FA, La-FA and Ce-FA were 135.7%, 43.47%, 128.0% and 140.0%, respectively. The results of this study provide guidance for the preparation of iron-based oxygen carriers with high redox performance.

Synthesis of Co4S3/Co9S8 nanosheets and comparison study toward the OER properties induced by different metal ion doping

Regulation of chemical composition and nanostructure, such as the introduction of dopant into two-dimensional nanomaterials, is a general and valid strategy for the efficient electrocatalyst design. In this work, Co4S3/Co9S8 nanosheets, with an ultrathin layer structure, were successfully synthesized via an efficient solvothermal process combined with ultrasonic exfoliation. Different metal ions (M = Fe3+, Cr3+, Mn2+ and Ni2+) were then doped by a simple cation exchange method and the effects of different dopants on the OER activities of Co4S3/Co9S8 NS were further investigated in alkaline media. The corresponding results implied that M-doped Co4S3/Co9S8 NS (M = Fe3+, Cr3+, Mn2+ and Ni2+) exhibited different electrocatalytic properties. Evidenced by XPS spectra, the different OER activities were mainly aroused by the redistribution of charge at the interface due to an electronic interaction between the doped metal ions and Co4S3/Co9S8 NS.

Anion-cation-dual doped tremella-like nickel phosphides for electrocatalytic water oxidation

Designing high-active earth-abundant electrocatalysts for oxygen evolution reaction (OER) is still a challenge. Elemental doping is an essential strategy to improve catalyst activity. Recent studies have shown that appropriate anion-cation-dual doping could greatly promote performance enhancement of OER electrocatalyst due to the synergistic effect of different dopants. Herein, tremella-like N/Fe dual doping nickel phosphides (N/Fe-Ni2P/Ni12P5) are fabricated for the first time. The N-anion and Fe-cation co-doping synergistically modulate the electronic structure, surface states and microtopography of the sample. The electrochemical surface area and electronic conductivity of the N/Fe-Ni2P/Ni12P5 are thus greatly enhanced. In addition, the computational simulations demonstrate that anion-cation co-doping optimizes adsorption free energy towards oxygen-containing intermediates and thus enhances intrinsic electrocatalytic activity. Consequently, the as-prepared N/Fe-Ni2P/Ni12P5 exhibits splendid OER performances with a low overpotential of 217 mV at the current density of 10 mA cm−2 and an ultra-long durability for over 120 h at high current densities of 500 and 1000 mA cm−2 in 1 M KOH. This work proposes an effective strategy to prepare dual-doped-type phosphide OER electrocatalyst with the promising application potential for large-scale water splitting.

Doping-mediated stabilization of copper vacancies to promote thermoelectric properties of Cu2−xS

Abstract Copper chalcogenides are outstanding thermoelectric materials for applications in the medium-high temperature range. Among different chalcogenides, while Cu2−xSe is characterized by higher thermoelectric figures of merit, Cu2−xS provides advantages in terms of low cost and element abundance. In the present work, we investigate the effect of different dopants to enhance the Cu2−xS performance and also its thermal stability. Among the tested options, Pb-doped Cu2−xS shows the highest improvement in stability against sulfur volatilization. Additionally, Pb incorporation allows tuning charge carrier concentration, which enables a significant improvement of the power factor. We demonstrate here that the introduction of an optimal additive amount of just 0.3% results in a threefold increase of the power factor in the middle-temperature range (500–800 K) and a record dimensionless thermoelectric figure of merit above 2 at 880 K.

Ab initio insights into the interaction mechanisms between boron, nitrogen and oxygen doped diamond surfaces and water molecules

Diamond and diamond-like carbon coatings are used in many applications ranging from biomedicine to tribology. A wide range of dopants have been tested to modify the hydrophilicity of these surfaces, since this is central to their biocompatibility and tribological performance in aqueous environments. Despite the large number of experimental investigations, an atomistic understanding of the effects of different dopants on carbon film hydrophilicity is still lacking. In this study, we employ ab initio calculations to elucidate the effects of B, N, and O dopants in several mechanisms that could modify interactions with water molecules and thus hydrophilicity. These include the adsorption of intact water molecules on the surfaces, minimum energy pathways for water dissociation, and subsequent interactions of hydrogenated and hydroxylated surfaces with water molecules. We find that all of the dopants considered enhance hydrophilicity, but they do so through different means. Most notably, B dopants can spontaneously chemisorb intact water molecules and increase its interactions in H-bond networks.