Substitution Of Transition Metal Ions Research Articles

Doping Effects on the Multiferroic Properties of KNbO3 Nanoparticles

The magnetization, polarization, and band-gap energy in pure and ion-doped KNbO3 (KNO) bulk and nanoparticles (NPs) are investigated theoretically using a microscopic model and Green’s function theory. It is shown that KNO NPs are multiferroic. The size dependence of M and P is studied. The magnetization M increases with decreasing NP size, whereas the polarization P decreases slightly. The properties of KNO can be tuned by ion doping, for example, through the substitution of transition metal ions at the Nb site or Na ions at the K site. By ion doping, depending on the relation between the doping and host ion radii, different strains appear. They lead to changes in the exchange interaction constants, which are inversely proportional to the lattice parameters. So, we studied the macroscopic properties on a microscopic level. By doping with transition metal ions (Co, Mn, Cr) at the Nb site, M increases, whereas P decreases. Doped KNO NPs exhibit the same behavior as doped bulk KNO, but the values of the magnetization and polarization in KNO NPs are somewhat enhanced or reduced due to the size effects compared to the doped bulk KNO. In order to increase P, we substituted the K ions with Na ions. The polarization increases with increasing magnetic field, which is evidence of the multiferroic behavior of doped KNO bulk and NPs. The behavior of the band-gap energy Eg also depends on the dopants. Eg decreases with increasing Co, Mn, and Cr ion doping, whereas it increases with Zn doping. The results are compared with existing experimental data, showing good qualitative agreement.

Cation-ordered Ni-rich positive electrode material with superior chemical and structural stability enabled by atomic substitution for lithium-ion batteries

Ni-rich layered oxides are considered as the most promising cathode materials for lithium-ion batteries (LIBs) due to their high specific capacity and low cost. However, the disordered Li/Ni mixing greatly affects their structural stability and electrochemical performance, thus hindering their wide application in commercial LIBs. Aiming to inhibit the premature death of Ni-rich layered oxides originated from the disordered Li/Ni mixing, atomic substitution of transition metal ions in LiNi0.83Co0.11Mn0.06O2 with high-valence metal molybdenum ions (denoted as Mo-NCM) is proposed in this work. The structure evolution of the as-prepared Mo-NCM caused by molybdenum substitution and the stability of Mo-NCM cathodes are comprehensively studied. Integrating experimental characterization with calculation results, it is found that the partial substitution of transition metal ions with Mo6+ ions can induce cation ordering and promote Li+ diffusion dynamics. Moreover, Mo6+ cations can act as the pillar to prevent local collapse and structural distortion, thus maintaining structural stability of the material. Furthermore, the formation of strong Mo-O bond between molybdenum and oxygen element can stabilize lattice oxygen and enhance the chemical stability of Ni-rich cathode. In addition, molybdenum modification can effectively reduce the exchange energy of Li+/Ni2+ and increase oxygen vacancy formation energy, further enhancing structural stability and promoting the kinetics of Li+ diffusion, and eventually enhancing the electrochemical performance of Mo-NCM based Li-ion batteries. The capacity retention of LIBs with 1 mol% Mo-NCM cathode can reach 98.67% after 200 cycles at 1C. This study provides a new insight into enhancing the chemical and structural robustness of Ni-rich cathode electrode materials.

A comparative study on the effect of Cr3+, Fe3+ and Ni2+ substitution on the dielectric, ferroelectric and electrocaloric response of BST ceramics

A comparative study on the influence of different 3d transition metal ions (Cr3+, Fe3+ and Ni2+) on the structural, dielectric, ferroelectric and electrocaloric response of BST ceramics is reported in the present work. Conventional solid-state reaction method was adopted for preparing the samples. A pure perovskite phase with tetragonal structure was confirmed by X-ray diffraction (XRD) analysis. Tetragonality was found to be decreased with the substitution of transition metal ions except in Cr3+ substituted sample. The dielectric behavior was investigated as a function of temperature (30 °C–150 °C) at different frequencies. Dielectric constant (ε) data was fitted with Power Law above Tc and diffused phase behavior was observed in the samples. P-E loops were recorded at different applied electric fields and temperatures. Improvement in ferroelectric properties (Pr = 10.56 μC/cm2, Ec = 2.40 kV/cm and Pr/Pmax = 0.53) was observed for Cr-substituted sample. Indirect method based on Maxwell's entropy-polarization relationship was employed to evaluate the electrocaloric effect (ECE) for all the samples. The value of ΔTmax was found to be maximum for (1.113K) for Cr substituted samples. The results show that Cr substituted BST are suitable for use in capacitor, memory devices and new generation solid-state cooling devices.

Comparative study of Nd3+, Cr3+-doped Mg-Zn nanoferrites

The present manuscript portrays, the structural, magnetic, and electrical properties of pristine, Neodymium (Nd3+), and Chromium (Cr3+) doped Mg-Zn nanoparticles [Mg0.9 Zn0.1MxFe2-xO4 NPs, where M = 0, Nd3+, and Cr3+] synthesized by autocombustion method. Structural characterization revealed face-centred cubic crystallinity of all the compositions with space group Fd3¯m. Even though Nd and Cr are members of the rare earth and transition metal families, the differences in their ionic radii cause variations in structural properties of Mg-Mn. The dielectric properties showed that AC conductivity increases with increasing frequency for all the compositions but was maximum for Nd3+ doped sample as compared to pristine and Cr3+ doped Mg-Zn nanoparticles. Magnetic hysteresis loop displayed superparagmagnetic behavior with negligible coercivity and retentivity but the value of saturation magnetization was maximum for Nd3+ doped Mg-Mn nanoparticles, and started decreasing with introduction of Cr3+ ions in the host Mg-Mn ferrites lattice framework, depicting improved magnetic properties due to doping of rare earth ions as compared to transition metal ion substitution. Changes in crystallite size of the host Mg-Zn crystal network, by doping rare earth ions as compared to transition metal ion induces an increment in electrical conductivity, and magnetic properties.

Magnetostriction studies on transition metal substituted cobalt ferrite

Structural, magnetic and microstructural properties of transition metal (TM) substituted cobalt ferrite Co0.9TM0.1Fe2O4 (where TM = Ti, Cr, Mn, Ni and Cu and Zn) were investigated. The present study shows marked dependence of the magnetostriction on the concentration of the substituted transition metal ions for Cobalt in CoFe2O4. The magnetic characteristics of the prepared compositions such as coercivity, anisotropy constant and saturation magnetization changed significantly on transition metal substitution. The present study shows the way to tune the anisotropy of cobalt ferrite by effective substitution of other transition metal ions for Co which subsequently affects the stress sensing performance by changing the slope of the magnetostriction curve. Apart from the magnetic properties the microstructure can also be effectively modified by substitution of other transition metal ions. Only 10% substitution of cobalt showed drastic influence on magnetostriction and slope of magnetostriction curve. The composition with 10% nickel Co0.9Ni0.1Fe2O4 exhibited maximum slope for the magnetostriction curve of −53.7 ppm/Oe, along with reasonably high magnitude of strain of 186 ppm making it a suitable for exploring stress sensing applications.

Distinct effects of transition metal (cobalt, manganese and nickel) ion substitutions on the abiotic oxidation of pyrite: In view of hydroxyl radical production

The abiotic oxidation of pyrite (FeS2) is a geochemically crucial reaction involved in acid mine drainage, the release of toxic trace elements and the generation of hydroxyl radicals (•OH) that can oxidize environmental substances. Studies on •OH generation from the abiotic oxidation of pyrite have drawn wide interest, but the effects of the common substitution of transition metal ions on •OH generation are still largely unknown, and worthy of comprehensive comparison. We therefore synthesized and comprehensively characterized micron-sized pyrites containing low concentrations of cobalt (Co), nickel (Ni), or manganese (Mn) ions, and tested the relative ability of these transition metal ion-substituted pyrites to generate •OH under abiotic oxidation. We found that transition metal ion substitutions inhibited the growth of pyrite crystals to various extents and increased Fe–S bond distances, leading to distinct alterations in surface chemical composition, conductivity, and the exposure of active faces. These differences resulted in an increase in •OH generation by the oxidation of transition metal ion-substituted pyrites, relative to pure pyrite, with the order of increase being Mn2+-substituted < Ni2+-substituted < Co2+-substituted pyrites. These substituent-dependent differences were explored by linking the crystal properties and physical chemistry of these pyrites to various reaction pathways that were possible in such contexts. For pure pyrite, the heterogeneous Fenton reaction was the chief generator of •OH. The substitution of pyrite with Co2+, which was redox-active, increased the conductivity of pyrite and accelerated the reduction of surface Fe3+ to Fe2+, resulting in a significant increase in H2O2 and •OH production. The substitution of pyrite with Mn2+, which was also redox-active, likewise increased the conductivity; however, the high oxidizing ability of surface Mn4+ inhibited the reduction of Fe3+ and thus decreased •OH generation. By contrast, the substitution of pyrite with Ni2+ did not affect electron transfer but led to absolute exposure of the (111) face of pyrite, which increased its activity toward O2 and H2O, slightly increasing H2O2 and •OH generation. These results highlight the vital role of transition metal ion-substituted pyrite in various geochemical processes.

Vanadyl Phosphates AxVOPO4 (A = Li, Na, K) as Multielectron Cathodes for Alkali‐Ion Batteries

AbstractVanadyl phosphates comprise a class of multielectron cathode materials capable of cycling two Li+, about 1.66 Na+, and some K+ ions per redox center. In this review, structures, thermodynamic stabilities, and ion diffusion kinetics of various AxVOPO4 (A = Li, Na, K, NH4) polymorphs are discussed. Both the experimental data and first‐principle calculations indicate kinetic limitations for alkali metal ions cycling, especially between for 0 ≤ x ≤ 1, and metastability of phases with x &gt; 1. This creates challenges for multiple‐ion cycling, as the slow kinetics call for nanosized particles, which being metastable and reactive with organic electrolytes are prone to side reactions. Thus, various synthesis approaches, surface coating, and transition metal ion substitution strategies are discussed here as possible ways to stabilize AxVOPO4 structures and improve alkali metal ion diffusion. The role of advanced characterization techniques, such as X‐ray absorption spectroscopy, diffraction, pair distribution function analysis and 7Li and 31P NMR, in understanding the reaction mechanism from both structural and electronic points of view is emphasized.

Suppressive effect of Fe cations in Mg(Mn1−xFex)2O4 positive electrodes on oxidative electrolyte decomposition for Mg rechargeable batteries

MgMn2O4 spinel oxide has a very positive redox potential (2–3 V vs. Mg/Mg2+) and is a promising positive electrode material for Mg rechargeable batteries. However, the charge of MgMn2O4 cannot be adequately accumulated due to oxidative electrolyte decomposition resulting in poor cyclability. We have examined the effect of transition metal ion substitution in Mg spinel oxides and demonstrated that oxidative electrolyte decomposition is suppressed by replacing Mn cations in MgMn2O4 with Fe. Tetragonal MgMn2O4 spinel was converted into cubic-phase Mg(Mn1−xFex)2O4, when 20% or more of its Mn3+ ions were replaced by Fe3+ (x = 0.2, 0.4, 0.6, 0.8, 1). Mixed Mn–Fe cubic spinel oxides exhibited enhanced cyclic performance due to the suppression of oxidative electrolyte decomposition and improved structural stability. This approach provides a means of improving the electrochemical performance of Mg battery systems without requiring thermodynamically stable electrolytes.

Influence of dopant substitution mechanism on catalytic properties within hierarchical architectures.

A range of hierarchically porous (HP) AlPO-5 catalysts, with isomorphously substituted transition metal ions, have been synthesized using an organosilane as a soft template. By employing a range of structural and spectroscopic characterization protocols, the properties of the dopant-substituted species within the HP architectures have been carefully evaluated. The resulting nature of the active site is shown to have a direct impact on the ensuing catalytic properties in the liquid-phase Beckmann rearrangement of cyclic ketones.

Quantified Evidence of Homogeneous Al3+ Doping on LiNi0.80Co0.15Al0.05O2: Effects on the Electrochemical and the Thermal Stability

Aluminum doped high Ni cathode active materials such as LiNi0.80Co0.15Al0.05O2 are well known as promised candidate for high energy density LIB. Two challenges for LiNi0.80Co0.15Al0.05O2 improvements, to realize both thermal stability at delithiated state and suppression of microstructure deterioration during repeated charge and discharge reaction, have been investigated by homogeneous substitution of transition metal ions with Al3+. We have also shown that micro strain obtained from the Williamson-Hall analysis at higher SOC was an effective factor to quantify the structural stability of cathode active materials and played important role in LIB’s life. In this study, we focused on the investigation of the effects of homogeneity of Al3+ doping into LiNi0.80Co0.15Al0.05O2. Two types of LiNi0.80Co0.15Al0.05O2 were synthesized from co-precipitated precursor. One was an inhomogeneous Al3+ doped LiNi0.80Co0.15Al0.05O2 (Sample A) which was made from a precursor using Ni2+ and Co2+ sulfate solution mixture. Another was a homogeneous Al3+ doped LiNi0.80Co0.15Al0.05O2 (Sample B) made from Ni2+, Co2+, and Al3+sulfate solution mixture. First, the effect of homogenous Al3+ doping on crystalline parameters was investigated. Crystalline strain in delithiated cathode was evaluated as a function of the Williamson-Hall plot slope. It has already revealed that the lattice strain will increase when electrode charged up to higher potential and increasing strain will have a detrimental impact on the life and safety of LIBs [1]. Thus, we compared the lattice strain of the couple types of cathode at delithiated state. The LiNi0.80Co0.15Al0.05O2 cells were charged at a potential of 4.3 V vs Li+/Li at 25 oC and then disassembled them in a dry Ar-filled grove box. As a result, we revealed that homogeneous Al3+doping in cathode can suppress the lattice strain at the higher SOC. Second, we measured structural change of cathode materials at delithiated cathodes as a quantification of thermal stability by using a temperature programmed X-ray diffraction (TPXRD) analysis in the temperature range from RT to 500 oC under Ar atmosphere. Three types of crystal phase; layered rock-salt, spinel and rock-salt were observed in our measurement. The ratio of deteriorated phases; spinel and rock-salt in the delithiated LiNi0.80Co0.15Al0.05O2 with temperature are shown in Fig. 1. The deteriorated phases which transformed from the layered rock-salt phase were observed in both cathodes at high temperature. The deterioration of Sample A occured from 200 oC. In contrast, Sample B remained layered rock-salt phase up to 250 oC. From this result we concluded that Sample B had higher thermal stability than Sample A.In order to demonstrate the deterioration mechanism, micro structure of both Sample A and Sample B after 500 cycle-test at 45 oC were investigated using cross-section SEM and TEM. The TEM image of Sample A and Sample B are shown in Fig. 2. The lattice image of Sample A is unobvious that may be induced from charge/discharge damage at high temperature. In contrast, that of Sample B is clearer than Sample A as shown. These results were consistent with the trend of electrochemical stability. In conclusion, it was confirmed that the deterioration during cycling at 45 oC was suppressed by homogeneous Al3+ distribution in LiNi0.80Co0.15Al0.05O2. In this study, we applied the Williamson-Hall analysis to estimate the structural stability for different homogeneity of Al3+ doping in LiNi0.80Co0.15Al0.05O2. We showed the strain analysis as a particularly useful methode which explained the structural stability of delithiated LiNi0.80Co0.15Al0.05O2in quantitatively. Further details shall be presented at the meeting. Reference [1] Rosa Robert, Petr Novák, Journal of The Electrochemical Society 162(9), A1823 (2015). Figure 1

First order Raman scattering analysis of transition metal ions implanted GaN

Transition Metal (TM) ions V, Cr, Mn and Co were implanted into GaN/sapphire films at fluences 5×1014, 5×1015 and 5×1016cm−2. First order Raman Scattering (RS) measurements were carried out to study the effects of ion implantation on the microstructure of the materials, which revealed the appearance of disorder and new phonon modes in the lattice. The variations in characteristic modes 1GaN i.e. E2(high) and A1(LO), observed for different implanted samples is discussed in detail. The intensity of nitrogen vacancy related vibrational modes appearing at 363 and 665cm−1 was observed for samples having different fluences. A gallium vacancy related mode observed at 277/281cm−1 for TM ions implanted at 5×1014cm−2 disappeared for all samples implanted with rest of fluences. The fluence dependent production of implantation induced disorder and substitution of TM ions on cationic sites is discussed, which is expected to provide necessary information for the potential use of these materials as diluted magnetic semiconductors in future spintronic devices.

Magnetic and optical properties of Ti doped ZnO prepared by solid state reaction method

The substitution of transition metal ions on zinc oxide as host lattice may lead to some interesting behavioural changes in magnetic and optical properties. The present work discusses the effect of Ti dopant in zinc oxide Zn1−xTixO (x=0.02 and 0.03) on the optical and magnetic properties. For that, Ti doped zinc-oxide (ZnO) was prepared by standard solid state reaction method in a high temperature furnace. The magnetic properties were analysed using vibrating sample magnetometry. The morphology of the samples was studied by SEM micrographs. The effect of the dopant on the semiconducting nature of the host ZnO was investigated by UV–vis studies.

Two Hexa-Ni-Substituted AsW9O34 Clusters Functionalized by Organic Ligands

Hydrothermal reactions of trilacunary precursor A-α-AsW9O34 9− polyoxoanions and nickel ions in the presence of ethylenediamine (en = ethylenediamine) led to two new hexa-Ni-substituted Keggin-type tungstoarsenates [Ni6(μ 3-OH)3(en)3(H2O)6(B-α-AsW9O34)]·6H2O (1) and [Ni6(μ 3-OH)3(en)3(H2O)6(B-α-AsW9O34)]·10H2O (2), which have been characterized by elemental analyses, IR spectra, powder X-ray diffraction, thermogravimetric analyses and single-crystal X-ray diffraction. Crystal data for 1: hexagonal, R3c, a = b = 20.4379(5) A, c = 21.5062(6) A, β = 120o, V = 7779.8 (3) A3 and Z = 6; for 2: momoclinic, P21/c, a = 13.4200(3) A, b = 19.1428(5) A, c = 22.8845(9) A, β = 112.403(3)o, V = 5435.2(3) A3 and Z = 4. Structural analyses reveal that the [Ni6(μ 3-OH)3(B-α-AsW9O34)] clusters in 1 and 2 are covalently functionalized by neutral en ligands, in which two similar {Ni6(μ 3-OH)3(en)3(H2O)6}9+ cores have been observed by our lab. Notably, 1 and 2 represent the highest number of substituted transition metal ions in all known lacunary Keggin-type polyoxotungstoarsenate monomers.

A Review on Chemical Synthesis, Characterization and Optical Properties of Nanocrystalline Transition Metal Doped Dilute Magnetic Semiconductors

Nanomaterials have fascinated researchers in recent years because these materials exhibit unusual optical, magnetic and electrical properties as compared to their bulk counterparts. Incorporating impurity ions into a semiconducting host to extend its properties has been one of the most important techniques that paved the way for the modern technology based on spintronic devices. Over the past few years, oxide based dilute magnetic semiconductors (DMSs) have gained remarkable interest due to the possibility of inducing room temperature ferromagnetism. This review describes the experimental developments and optical properties of oxide based DMSs, including the recent results on ZnO, CdO and In2O3 based systems. Optical properties of transition metal (TM)-doped ZnO, CdO and In2O3 dilute magnetic semiconductor nanoparticles show red shift in energy band gaps. Such types of phenomena are attributed to sp-d exchange interactions between band electrons and localized d-electrons of the substituted transition metal ions. Table of Contents

High pressure driven structural and electrochemical modifications in layered lithium transition metal intercalation oxides

High pressure–high temperature (HP/HT) methods are utilized to introduce structural modifications in the layered lithium transition metal oxides LiCoO2 and Li[NixLi1/3−2x/3Mn2/3−x/3]O2 where x = 0.25 and 0.5. The electrochemical property to structure relationship is investigated combining computational and experimental methods. Both methods agree that the substitution of transition metal ions with Li ions in the layered structure affects the compressibility of the materials. We have identified that following high pressure and high temperature treatment up to 8.0 GPa, LiCoO2 did not show drastic structural changes, and accordingly the electrochemical properties of the high pressure treated LiCoO2 remain almost identical to the pristine sample. The high pressure treatment of LiNi0.5Mn0.5O2 (x = 0.5) caused structural modifications that decreased the layered characteristics of the material inhibiting its electrochemical lithium intercalation. For Li[Li1/6Ni1/4Mn7/12]O2 more drastic structural modifications are observed following high pressure treatment, including the formation of a second layered phase with increased Li/Ni mixing and a contracted c/a lattice parameter ratio. The post-treated Li[Li1/6Ni1/4Mn7/12]O2 samples display a good electrochemical response, with clear differences compared to the pristine material in the 4.5 voltage region. Pristine and post-treated Li[Li1/6Ni1/4Mn7/12]O2 deliver capacities upon cycling near 200 mA h g−1, even though additional structural modifications are observed in the post-treated material following electrochemical cycling. The results presented underline the flexibility of the structure of Li[Li1/6Ni1/4Mn7/12]O2; a material able to undergo large structural variations without significant negative impacts on the electrochemical performance as seen in LiNi0.5Mn0.5O2. In that sense, the Li excess materials are superior to LiNi0.5Mn0.5O2, whose electrochemical characteristics are very sensitive to structural modifications.

Half-rotation in a kinetically locked [2]catenane induced by transition metal ion substitution

We report on a heterocircuit [2]catenane in which a reversible half-rotation of one ring about the other can be induced, and locked in place, by switching the coordination of the interlocked rings between Pd(II) and Co(III).

Tetragonal and hexagonal polymorphs of BaTi1−xFexO3−δ multiferroics using x-ray and Raman analyses

The effect of Fe doping on the crystalline phase transformation and on the local environment around Fe dopant ions is investigated for BaTi1−xFexO3−δ (0.0 ≤ x ≤ 0.5) polycrystalline samples, using x-ray diffraction, x-ray absorption spectroscopy, and Raman scattering spectroscopy. Our experimental results show that the tetragonal-to-hexagonal transformation is gradually taken place when increasing the Fe content in the range 0.02 ≤ x ≤ 0.12. Although both hexagonal and tetragonal polymorphs coexist in this doping range, Fe ions preferably substitute for Ti sites in the hexagonal lattice and exist in both Fe3+ and Fe4+ forms. Our work is of paramount importance to provide a direct evidence to the preferable substitution of transition metal ions for Ti ions.

Transition metal ion substitution in titanosilicate ETS-10 for enhanced UV light photodegradation of methylene blue

Partial isomorphous substitution of transition metal (M = V, Cr, Mn, Fe, Co) ions in the titanosilicate ETS-10 framework (ETMS-10 with M/Ti ≈ 0.06 mol mol −1) was carried out in efforts to enhance the photocatalytic activity of ETS-10 in the degradation of methylene blue (MB) under UV light (280–400 nm) irradiation. XRD, UV–vis, and EDX analyses suggested substitution of V 4+/V 5+, Cr 3+, Mn 2+, and Fe 3+ for octahedral Ti 4+, and Co 2+ for tetrahedral Si 4+ in the ETS-10 framework. All ETMS-10 samples showed lower bandgap energies ( E g = 3.79–3.90 eV) than unmodified ETS-10 ( E g = 3.96 eV), and exhibited absorption features in the visible light region. These samples showed higher photocatalytic activities in photodegradation of MB (pseudo-first-order reaction rate constants, k = 0.016–0.055 min −1) than unmodified ETS-10 ( k = 0.008 min −1), and the activities decreased in the order: ETCoS-10 > ETCrS-10 ≈ ETFeS-10 > ETMnS-10 ≈ ETVS-10 > unmodified ETS-10. This was hypothesized to be due in part to the lower bandgap energies of ETMS-10 samples compared to that of unmodified ETS-10, as well as the introduction of midgap states with transition metal ions replacing Ti 4+, and different d electron configurations of transition metal ions substituted in the ETS-10 framework.

Ferromagnetism of epitaxially grown CaRu 1−xM xO 3 (M=Ti, Mn) films

Epitaxial thin films of CaRu 1− x M x O 3 (M=Ti, Mn) were fabricated on a (0 0 1)-SrTiO 3 substrate by spin-coat method using organometallic solutions (metal alkoxides). Results of X-ray diffraction and transmission electron microscopy indicate that the epitaxial films were grown pseudomorphically so as to align the [0 0 l] axis of the CaRu 1− x M x O 3 films perpendicular to the (0 0 1) plane of the SrTiO 3 substrate. Ferromagnetism and metal–insulator transition are induced by the substitution of transition metal ions. The occurrence of ferromagnetism was explained qualitatively assuming a TiRu 6 cluster model for CaRu 1− x Ti x O 3 film and a mixed valence model for CaRu 1− x Mn x O 3 film. Ferromagnetism was also observed for layered CaRuO 3/CaMnO 3 film and CaRuO 3/CaMnO 3/CaRuO 3/CaMnO 3 multilayer film and the magnetism was explained by an interfacial exchange interaction model with magnetic Mn 3+, Mn 4+, and Ru 5+ ions.

Effects of hydronium intercalation and cation substitution on the photocatalytic performance of layered titanium oxide

We have investigated the effects of hydronium (H 3O +) intercalation and transition metal substitution on the photocatalytic activity of layered titanate. The basal spacings of the cesium titanate and Fe-/Ni-substituted titanates are notably expanded by 1 M HCl treatment, indicating the intercalation of hydronium ion. Diffuse reflectance UV–vis spectroscopic results clearly demonstrate that, in contrast to the hydronium intercalation, the substitution of transition metal ions gives rise to a remarkable narrowing of bandgap energy down to ∼1.9–2.3 eV. According to Fe K- and Ni K-edge X-ray absorption spectroscopic analysis, the substituted iron and nickel ions are stabilized in octahedral titanium sites with trivalent and divalent oxidation states, respectively. The photodegradation tests for organic dye molecules reveal that the hydronium intercalation enhances remarkably the photocatalytic performance of cesium titanate under UV irradiation and the substitution of Fe or Ni endows wide bandgap titanate with visible light driven photocatalytic activity.