Incorporation Of Transition Metals Research Articles

Surface phonon activation for broadband high emissivity via textured structure on TiO2 coating

In the pursuit of developing broadband high emissivity coatings for metallic radiation thermal protection, conventional approaches often involve complex photonic structures or the incorporation of transition metals and rare earth additives, which pose significant technological challenges and environmental concerns. Here, we present a straightforward and eco-friendly surface structuring strategy for creating a high emissivity TiO2 coating on titanium, eliminating the need for environmentally hazardous additives. By controlling surface micropore diameter to ∼6 um through soft-sparking discharge, we successfully engineered a textured surface that effectively mitigates the intrinsic emissivity dip of planar TiO2 at wavelengths with weak polarization extinction (3–8 µm) and strong polarization resonance (>12 µm). Finite-difference time-domain (FDTD) simulations highlighted the crucial role of micropores in confining the incident electric field, maximizing the absorption potential of surface phonon polaritons. This improvement yields an impressive emissivity of 0.83 across the thermal infrared spectrum. The coating also demonstrated robust resistance to oxidation and retained its high emissivity at elevated temperatures, presenting a promising solution for sustainability in spacecraft and electronic applications.

Theoretical exploration of ternary nitrides for high-efficiency ferroelectric photovoltaics

Although nitride materials hold great functional promise, ferroelectric photovoltaic nitrides remain relatively rare within the scientific community. In this study, high-throughput calculations have been employed to explore and predict novel stable ternary nitrides characterized by both high photoelectric conversion efficiency and robust ferroelectric polarization. Notable candidates, including Mg2CrN3, Mg2MnN3, MgVN2, ZnVN2, and X2BiN3 (where X represents Mg, Ca, and Sr), are anticipated to exhibit remarkable ferroelectric photovoltaic properties, with a particular emphasis on efficiently harnessing visible light. The incorporation of early 3d transition metals and bismuth (Bi) elements within ternary metal nitrides is highlighted as a key strategy for achieving high ferroelectric photovoltaic efficiency. Furthermore, these ferroelectric nitrides demonstrate relatively high carrier mobilities, which are conducive to facilitating the transport of photogenerated carriers driven by ferroelectricity. This research offers a selection of promising ternary nitride candidates with substantial potential for application in the field of ferroelectric photovoltaics.

Mesoporous RE0.5Ce0.5O2-x Fluorite Electrocatalysts for the Oxygen Evolution Reaction.

Developing highly active and stable electrocatalysts for the oxygen evolution reaction (OER) is key to improving the efficiency and practical application of various sustainable energy technologies including water electrolysis, CO2 reduction, and metal air batteries. Here, we use evaporation-induced self-assembly (EISA) to synthesize highly porous fluorite nanocatalysts with a high surface area. In this study, we demonstrate that a 50% rare-earth cation substitution for Ce in the CeO2 fluorite lattice improves the OER activity and stability by introducing oxygen vacancies into the host lattice, which results in a decrease in the adsorption energy of the OH* intermediate in the OER. Among the binary fluorite compositions investigated, Nd2Ce2O7 is shown to display the lowest OER overpotential of 243 mV, achieved at a current density of 10 mA cm-2, and excellent cycling stability in an alkaline medium. Importantly, we demonstrate that rare-earth oxide OER electrocatalysts with high activity and stability can be achieved using the EISA synthesis route without the incorporation of transition and noble metals.

Polymer‐Derived Ceramic Coatings with Excellent Thermal Cycling Stability

In the present work, transition metal‐containing preceramic silicon polymers were synthesized via chemical modification of a commercially available organopolysilazane with Hf and Ta amido complexes as well as with borane dimethyl sulfide complex. The incorporation of transition metals into the polymer structure, their influence on ceramization and processability were thoroughly investigated. Moreover, the prepared preceramics were coated onto silicon wafers via spin coating and converted into crack‐free, amorphous SiHfTa(B)CN‐based ceramic coatings with excellent adhesion to the substrate. The composition of the ceramic coatings was investigated via X‐ray photoelectron spectroscopy (XPS) and their high‐temperature behavior was studied via oxidation tests performed at 1100 °C. Moreover, a thermal cycling procedure to temperatures above 1250 °C with rapid heating and cooling rates (i.e., in the range of 100–120 K s−1) was applied to the ceramic coating, which showed no damage even after ten thermal cycles, indicating their outstanding performance and their potential for use as environmental barrier coatings at high temperatures.

Dual-nodes bridged cobalt-modified Keggin-type polyoxometalate-based chains for highly efficient CO2 photoconversion.

The design of efficient catalysts for photocatalytic CO2 conversion is of great importance for the sustainable development of society. Herein, three polyoxometalate (POM)-based crystalline materials were formulated prepared by substituting transition metals and adjusting solvent acidity with 2-(2-pyridyl) benzimidazole (pyim) as the light-trapping ligand, namely {[SiW12O40][Co(pyim)2]2}·2C2H5OH (SiW12Co2), {[SiW12O40][Ni(pyim)2]2}·2C2H5OH (SiW12Ni2), and {[SiW12O40][Mn(pyim)2]2}·2C2H5OH (SiW12Mn2). X-ray crystallography diffraction analysis indicates that the three complexes exhibit isostructural properties, and form a stable one-dimensional chain structure stabilized by two [M(pyim)2]22+ (M = Co, Ni, and Mn) fragments serving as dual-nodes to the adjacent SiW12 units. A comprehensive analysis of the structural characterization and photocatalytic CO2 reduction properties is presented. Under light irradiation, SiW12Co2 exhibited a remarkable CO generation rate of 10 733 μmol g-1 h-1 with a turnover number of 328, outperforming most of the reported heterogeneous POM-based photocatalysts. Besides, cycling tests revealed that SiW12Co2 is an efficient and stable photocatalyst with great recyclability for at least four successive runs. This study proves that the successful incorporation of diverse transition metals into the POM anion could facilitate the development of highly efficient photocatalysts for the CO2RR.

Revisiting ultrasmall phosphine-stabilized rhodium-doped gold clusters AunRh (n = 5, 6, 7, 8): geometric, electronic, and vibrational properties.

Incorporation of other transition metals in Au nanoclusters has been thriving recently due to its effect on their electronic and photophysical properties. Here, the ultrasmall phosphine-stabilized Rh-doped gold clusters AunRh (n = 5, 6, 7, 8), with metal core structures represented as fragments of a rhodium-centered icosahedron, are considered. The geometric and electronic properties of these nanoclusters are revisited and analyzed using density functional theory (DFT). Moreover, infrared spectra are simulated to identify the effects of Rh doping on the clusters through vibrational properties. Peaks are assigned to breathing-like normal modes for all AuRh clusters except for Au8Rh, likely due to the presence of bound Cl ligands. Unlike their pure gold core counterparts, the % motions of both Au and Rh atoms are lower in the mixed metal clusters, suggesting more restrained metal cores by rhodium, which could result in other novel physical and chemical properties not hitherto discovered.

Understanding the Effects of Transition Metal Impurities on Nickel (oxy) Hydroxide Electrocatalysts in Alkaline Media

Nickel-based materials are widely used as critical components of electrochemical energy devices, including alkaline electrolyzers, capacitors, and alkaline batteries. These materials are often preferred because of their availability and low cost compared to precious metals, which makes them excellent candidates for accomplishing the decarbonization goals and electrifying our society. However, several studies have demonstrated that the incorporation of trace impurities from commercial alkaline electrolytes induces significant changes in the intrinsic activity, pseudocapacitance, and stability of Ni-based materials, resulting in erroneous descriptions of their performance. Thus, having a better understanding of the effects of these impurities will lead to practical ways to prevent or control their impact on electrochemical energy devices.In this work, we study the incorporation of transition metals (i.e., Fe, Co, Cu) that form insoluble hydroxides in alkaline media over nickel (oxy) hydroxide electrocatalysts. We systematically examine how these trace impurities modify the OER activity, stability, and the pseudocapacitive properties of NiOOH. As depicted in Figure 1, KOH electrolytes containing trace impurities of Fe and Co induce significant changes in the OER onset potential of Ni(OH)2/NiOOH electrocatalysts, according to the irreversible charge increase measured through coulovoltammetry (QV) curves. Moreover, distinct redox peaks can be seen for each scenario. After aging in purified KOH electrolyte (Fig. 1a), the cyclic voltammogram (CV) of Ni(OH)2/NiOOH exhibits four oxidation peaks that can be ascribed to a mixture of both α and β structural phases (Fig. 1b) while aging in Fe-unpurified KOH promotes the α phase and shifts the redox peak anodically (Fig. 1c). Aging in Co-unpurified KOH promotes a more ordered β structural phase without changing the OER activity significantly (Fig. 1d), which is desirable for pseudocapacitive materials. Additional experiments examining the OER activity, stability, and capacitance provide valuable insights into these impurities, and specific strategies to prevent and minimize their effects will be discussed. Overall, this work illustrates the importance of tracking trace metal impurities in alkaline electrolytes to minimize undesirable effects in electrochemical energy devices. Figure 1

Postsynthetic Modification of the Nonanuclear Node in a Zirconium Metal-Organic Framework for Photocatalytic Oxidation of Hydrocarbons.

Heterogeneous catalysis plays an indispensable role in chemical production and energy conversion. Incorporation of transition metals into metal oxides and zeolites is a common strategy to fine-tune the activity and selectivity of the resulting solid catalysts, as either the active center or promotor. Studying the underlying mechanism is however challenging. Decorating the metal-oxo clusters with transition metals in metal-organic frameworks (MOFs) via postsynthetic modification offers a rational approach to construct well-defined structural models for better understanding of the reaction mechanism. Therefore, it is important to expand the materials scope beyond the currently widely studied zirconium MOFs consisting of Zr6 nodes. In this work, we report the design and synthesis of a new (4,12)-connected Zr-MOF with ith topology that consists of rare Zr9 nodes. FeIII was further incorporated onto the Zr9 nodes of the framework, and the resulting MOF material exhibits significantly enhanced activity and selectivity toward the photocatalytic oxidation of toluene. This work demonstrates a delicate ligand design strategy to control the nuclearity of Zr-oxo clusters, which further dictates the number and binding sites of transition metals and the overall photocatalytic activity toward C-H activation. Our work paves the way for future exploration of the structure-activity study of catalysts using MOFs as the model system.

Nuclear attenuation ability of ternary alumina-borate glass system for medical shielding applications

The present study aims to delve into sodium alumina-borate glass systems doped with transition metals by means of their optical properties and gamma attenuation performance, with a specific focus on their nuclear shielding applications. By leveraging advanced computational tools and simulation techniques, such as FLUKA and XCOM software, this research endeavours to investigate the optical properties and the gamma/radiation shielding ability of the glass system involved. The study seeks to elucidate the fundamental mechanisms governing optical transmission, radiation attenuation, and the overall shielding efficacy of these innovative glass systems. The results show that the optical properties as well as nuclear shielding ability of the glass system, including optical transmission, absorption coefficient, and half value layer (HVL), are significantly affected by Fe2O3 concentrations. Therefore, the incorporation of transition metals leads to enhance the attenuation of gamma rays, indicating an increase in the material's shielding efficiency against incident radiation. The findings of this study have important implications for the design and development of glass materials for various applications, such as nuclear energy, radiation detection, and optical communication.

2D/2D NiAl LDH integrated graphitic carbon nitride with robust interfacial contact for driving photocatalytic hydrogen production

Photocatalytic hydrogen production is promising for generating carbon-free energy through water splitting. Efficient photocatalytic materials with high photochemical efficiency are crucial for creating well-structured photocatalytic systems. Layered Double Hydroxides (LDHs) have gained significant scientific attention due to their unique electronic structure, compositional flexibility, and tunable band gap, which make them highly active for photocatalytic hydrogen evolution. However, the high surface energy of LDHs can lead to layer deactivation and reduce their efficiency as standalone photocatalysts. Herein, a novel design of two-dimensional (2D) g-C3N4 with 2D NiAl LDH to construct morphologically 2D/2D binary heterojunction composite with strong electrostatic interactions has been investigated. Different characterization techniques, such as XRD, FESEM, EDX, UV–Vis spectra, and PL were conducted to assess its photo-physical properties. The introduction of 15% NiAl LDH led to a significant increase in hydrogen production, reaching 28.13 µmol h−1, which is 3.75 and 9 times higher than pure g-C3N4 and NiAl LDH, respectively. The improved photocatalytic performance was attributed to the efficient charge transfer facilitated by the formation of Type-II heterojunction system. The interface junction observed in 2D/2D g-C3N4/NiAl LDH restricts charge recombination and extends its lifetime to carry out photocatalytic reactions. Furthermore, the effective integration of NiAl LDH onto g-C3N4 observed from FESEM and EDX prevents the deactivation of LDH nanoplates, supplying abundant reaction-active sites to expedite the photo-redox reaction. Significantly, the incorporation of transition metals, such as Ni and Al, into the LDH brucite layer enhances the optical properties, allowing for better utilization of light and further improving photocatalytic hydrogen production. This work provides valuable insights into the development of 2D/2D morphologically-engineered nanohybrids for driving photocatalytic hydrogen production.

Trends in structural, electronic and elastic properties of Ti2AC (A = Al, Zn, Cu, Ni) based on late transition metals substitution

Recently, the substitutional incorporation of late transition metals in the “A” sublattice of MAX phases further extends the physical properties and diversity of this class of materials. In this study, the structural, electronic and elastic properties of Ti2AC (A = Al, Zn, Cu, Ni) were investigated using the density functional theory. The calculated results reveal that a large number of d orbital bands of Zn, Cu, and Ni atoms accumulate around −6.5 eV, −2.5 eV, and −2.0 eV, respectively, leading to stronger ionic and metallic characteristics for Ti2ZnC, Ti2CuC, and Ti2NiC. Three Ti2AC (A = Zn, Cu, Ni) phases are ductile and consequently damage tolerant, whereas Ti2AlC is brittle in nature. When Al is replaced by Zn, Cu, and Ni, there is a remarkable decrease of hardness and shear modulus, indicating high machinability. Ti2ZnC, Ti2CuC, and Ti2NiC are expected to be promising thermal barrier coating materials.

Novel ternary metals-based telluride electrocatalyst with synergistic effects of high valence non-3d metal and oxophilic Te for pH-universal hydrogen evolution reaction

Electrocatalyst designs based on oxophilic foreign atoms are considered a promising approach for developing efficient pH-universal hydrogen evolution reaction (HER) electrocatalysts by overcoming the sluggish alkaline HER kinetics. Here, we design ternary transition metals-based nickel telluride (MoWNiTe) catalysts consisting of high valence non-3d Mo and W metals and oxophilic Te as a first demonstration of non-precious heterogeneous electrocatalysts following the bifunctional mechanism. The MoWNiTe showed excellent HER catalytic performance with overpotentials of 72, 125, and 182 mV to reach the current densities of 10, 100, and 1000 mA cm−2, respectively, and the corresponding Tafel slope of 47, 52, and 58 mV dec−1 in alkaline media, which is much superior to commercial Pt/C. Additionally, the HER performance of MoWNiTe is well maintained up to 3000 h at the current density of 100 mA cm−2. It is further demonstrated that the MoWNiTe exhibits remarkable HER activities with an overpotential of 45 mV (31 mV) and Tafel slope of 60 mV dec−1 (34 mV dec−1) at 10 mA cm−2 in neutral (acid) media. The superior HER performance of MoWNiTe is attributed to the electronic structure modulation, inducing highly active low valence states by the incorporation of high valence non-3d transition metals. It is also attributed to the oxophilic effect of Te, accelerating water dissociation kinetics through a bifunctional catalytic mechanism in alkaline media. Density functional theory calculations further reveal that such synergistic effects lead to reduced free energy for an efficient water dissociation process, resulting in remarkable HER catalytic performances within universal pH environments.

Mechanism of Dihydrogen Splitting by An Apparent Bimetallic Frustrated Lewis Pair based on Ir(III)/Pt(0)

AbstractThe incorporation of transition metals into frustrated Lewis pairs (FLPs) offers multiple opportunities for bond activation and catalysis. In this work, we explore the combination of the Lewis acidic Ir(III) cation [(η5‐C5Me5)IrCl(PMe2ArDipp2)]+ (ArDipp2=C6H3−2,6‐(C6H3−2,6‐iPr2)2) with the Lewis basic Pt(0) compound Pt(PtBu3)2. The bulkiness of the phosphine ligands prevents the formation of a bimetallic adduct. We have explored the cooperative cleavage of dihydrogen to gauge bimetallic FLP reactivity. As anticipated, compounds [(η5‐C5Me5)Ir(Cl)(H)(PMe2ArDipp2)] and [PtH(PtBu3)2]+ are rapidly formed, which suggests an actual FLP mechanism operating. However, our in‐depth experimental/computational study evidences that the whole process is considerably more complicated. Instead of a genuine FLP‐type activation, we favor a synergistic route that entails a number of equilibrium processes and the Brønsted catalyzed hydrogenation of the Pt(0) precursor.

Acidity and metal complexation of edge surface of birnessite-type MnO2: Insight from first principles simulations.

Birnessite-type MnO2 plays key roles in scavenging trace elements in numerous natural environments and has also been regarded as a promising energy storage material. The interfacial properties of birnessite are highly pH-dependent due to the presence of various amphoteric groups on its edges, and, therefore, the acidity constants (pKa) of these groups are vital to the understanding of its electrochemical and environmental performances. However, an accurate acidity dataset for birnessite is absent yet. In this study, we employed first-principles molecular dynamics simulations and the vertical energy gap method to calculate the pKas of groups on the birnessite (010) edge. The interfacial hydration structure was characterized with a focus on the hydrogen bonding network. The obtained pKas suggest that MnOH2 is active while Mn2OH remains inert in a common pH range. Based on these results, the incorporation of transition metals on the edge surface was investigated by taking Ni2+ and Zn2+ as the model cations. The energy changes associated with the incorporation process of Ni2+ from the outer-sphere state indicate that incorporation on the edge surface is more feasible than that on the basal surface presumed in previous studies. Overall, the results obtained provide an atomic-scale insight into the acid-base chemistry of birnessite and form a physical basis for understanding the interfacial processes of birnessite.

MOF catalysts for energy applications: incorporation of transition metals at atomic levels

MOF catalysts for energy applications: incorporation of transition metals at atomic levels

Impact of transition metal incorporation on the photocatalytic CO2 reduction activity of polymeric carbon nitride

Incorporation of transition metals in polymeric carbon nitride (CN) is an effective strategy to enhance its photocatalytic CO2 reduction activity, however, the difference of activity enhancement by incorporating different metals is not well understood. Herein, CN is modified with different transition metals by pyrolyzing the mixtures of urea and metal-organic frameworks (MOFs) to obtain MCN (M = Cu, Co, Ti or Fe). For each given type of metal-modified CN, the photocatalytic CO2 reduction activity is optimized by controlling the content of MOF precursor during pyrolysis. The optimized MCN delivers significantly enhanced CO evolution rate than pure CN, in the order of CN (83 μmol g−1 h−1) < CuCN (246 μmol g−1 h−1) < CoCN (326 μmol g−1 h−1) < TiCN (454 μmol g−1 h−1) < FeCN (490 μmol g−1 h−1). It is revealed that for CuCN and CoCN, Cu and Co are doped in CN. In contrast, for TiCN and FeCN, Ti and Fe exist as TiO2 and Fe2O3 forming Z-scheme heterojunctions with CN. The progressively improved photocatalytic activity corresponds to the increased specific surface area, CO2 adsorption capacity, visible light absorption as well as charge separation and transfer efficiency. Furthermore, we design and prepare bimetal incorporated CN through combining metal doping with heterojunction construction strategies, i.e., Cu doped CN/TiO2 and Co doped CN/Fe2O3, which exhibit further enhanced CO2 photoreduction performance with CO evolution rates of 613 and 718 μmol g−1 h−1, respectively. This work provides insight into the design and preparation of highly efficient CN-based photocatalytic materials.

Synergistic Effect of Co and Mn Co-Doping on SnO2 Lithium-Ion Anodes

The incorporation of transition metals (TMs) such as Co, Fe, and Mn into SnO2 substantially improves the reversibility of the conversion and the alloying reaction when used as a negative electrode active material in lithium-ion batteries. Moreover, it was shown that the specific benefits of different TM dopants can be combined when introducing more than one dopant into the SnO2 lattice. Herein, a careful characterization of Co and Mn co-doped SnO2 via transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy and X-ray diffraction including Rietveld refinement is reported. Based on this in-depth investigation of the crystal structure and the distribution of the two TM dopants within the lattice, an ex situ X-ray photoelectron spectroscopy and ex situ X-ray absorption spectroscopy were performed to better understand the de-/lithiation mechanism and the synergistic impact of the Co and Mn co-doping. The results specifically suggest that the antithetical redox behaviour of the two dopants might play a decisive role for the enhanced reversibility of the de-/lithiation reaction.

Porous aromatic frameworks with metallized catecholate ligands for CO2 capture from gas mixtures: A molecular simulation study

Carbon dioxide (CO2) capture from industrial gas mixtures, including flue gas, natural gas, and syngas is very important. Physical adsorption based on porous framework materials is quite promising for CO2 capture. In this work, we systematically investigated the separation performance of CO2 from CO2/N2, CO2/CH4, and CO2/H2 gas mixtures in porous framework materials with metallized catecholate ligands. The results indicated that the metallized catecholate ligands, including alkaline earth metals (Be, Mg, and Ca) and first-row transition metals (Sc to Zn), exhibit significantly effect on CO2 capture in porous framework materials. Specially, the selectivity of CO2 over N2, CH4, and H2 in the PAF-303 containing metallized catecholate ligands at initial pressure can reach up to 939.02 (PAF-303-Zn), 1775.5 (PAF-303-Cr), and 36555.24 (PAF-303-Cr), respectively. Furthermore, the incorporation of several transition metals can result in the revised N2 adsorption over CO2 owing to the strong selective back bonding with the N2 but not the CO2. The above results indicated that the materials containing metallized catecholate ligands are promising candidates for CO2 capture form flue gas, natural gas, and syngas.

Synthesis of spray deposited transition metals doped (Cr, Mn, Fe, Ni, and Cu) compositionally complex ZnO thin films with enhanced band gap and magnetism

Compositionally complex ceramics (CCCs) is now considered as a subgroup of high entropy ceramics (HECs); which focuses on the further opportunities of exploring wide compositional spaces and low entropy options of HECs. This study for the first time attempts to render high configurational disorder in the cationic site of ZnO lattice through the incorporation of higher concentration quinary 3d transition metals dopants i.e. Cr, Mn, Fe, Ni, and Cu. The authors here demonstrate the synthesis of pure ZnO and compositionally complex (BaxSrxMnxFexNix) Zn1-5xO (where x = 0.02, 0.04, and 0.06; the samples denoted as 10CCZO, 20CCZO, and 30CCZO respectively) thin films by low-cost spray pyrolysis technique at 250 °C. In order to investigate the unique wurtzite phase stability of all CCZO crystal structures, XRD analyses were carried out with Rietveld refinement. XRD study showed the single hexagonal wurtzite phase presence of P63mc space group in all CCZO samples and notable change in lattice parameters with doping increment. SEM results revealed a significant change in surface morphology as it transformed flake-shaped grains for pure ZnO to flower and interconnected flake patterns. UV–visible spectroscopy disclosed enhanced transmittance and optical band gap of 3.94, 3.97 eV in 10CCZO and 20CCZO, respectively. VSM test showed that the magnetization values increased substantially in CCZO thin films indicating the potential prospect of these CCZO in magneto-optical applications. In addition, tuned functional properties were correlated with microstructural features.

Phase Relationships in the Carbon–Titanium–Uranium System for Ultra-High Temperature Nuclear Fuels

Carbides of uranium have attracted interest as fuels for nuclear thermal propulsion (NTP) to drive deep-space exploration owing to their attractive thermal and neutronic properties. Optimization of NTP technology, however, requires ultra-high temperature reactor environments to maximize the ratio of thrust to propellant to achieve peak rocket engine efficiency. Incorporation of transition metals into uranium carbides offers a pathway to increase the melting point of carbide fuels to address the operational challenges posed by NTP. A thermodynamic model has been developed to examine the phase relationships in the C–Ti–U system at NTP conditions. Calculated phase relationships at ultra-high temperatures predict a stable (U, Ti)C solid solution. Additionally, experimental work on C–Ti–U synthesis via arc melting has been carried out, providing data on phase constitution and compositions that can be used to further refine the thermodynamic model that has been developed.