Transition Metal Tellurides Research Articles

Asynchronous strategy in the nucleation of Cr2Te3@FeTex Heterolayers: Synthesis and magnetic behaviors

With the rapid development of telluride-based two-dimensional (2D) ferromagnets, it is urgent to in-depth understanding and exploring their magnetic properties. Herein, we developed an asynchronous nucleating strategy to synthesize stacked heterolayers consisting of two magnetic transition metal tellurides (Cr2Te3 and FeTex). The synthesized heterolayers exhibit the distinct phase evolution of CrTe3-FeTe2-Fe1.125Te, which consequently leads to the magnetic behavior variation within the temperature range of 1.8–900 K. Additionally, by manipulating the ferromagnetic and antiferromagnetic phases in FeTex, an obvious exchange bias is observed at 1.8 K. This effect could be adjusted by stacked interface engineering, which provides promising tips for understanding magnetism in low-dimensional heterosystems.

Low-Potential Overall Water Splitting Induced by Engineered CoTe2–WTe2 Heterointerfaces

Heterointerfaces in the form of nanostructures can drastically improve electrochemical water splitting. This study is geared toward the design and development of cobalt telluride (CoTe2)-tungsten telluride (WTe2) nanostructures with good porosity and a high specific surface area, leading to faster overall water splitting kinetics. This is attributed to the enhanced synergistic effects of Co and W atoms, which regulate electron transfer and give rise to optimum binding energy for reaction intermediates. CoTe2–WTe2 nanostructures have demonstrated a low oxygen evolution reaction overpotential of 184 mV @ 10 mA cm–2 and a low hydrogen evolution reaction overpotential of 178 mV @ 10 mA cm–2 in alkaline solution. A two-electrode cell with CoTe2–WTe2 nanostructures as both the anode and the cathode exhibits a low cell potential of 1.52 V at a current density of 10 mA cm–2 with good stability for 50 h (7.8% reduction in current density). This study emphasizes the significance of heterointerface design in transition metal telluride electrocatalysts.

Heterointerface of vanadium telluride and zinc iron telluride nanosheets for highly efficient hydrogen production via water and urea electrolysis

Interface design is a promising strategy for electrocatalysis to optimize charge transfer ability and active sites of a catalyst. Herein, interfacially coupled vanadium telluride and zinc iron telluride nanosheets are synthesized on nickel foam (VTe2@ZnFeTe/NF) by a facile hydrothermal method, which furnishes low overpotentials of 119/217 mV for the hydrogen evolution reaction (HER) and 240/300 mV for the oxygen evolution reaction (OER) at 20/50 mA cm−2 in potassium hydroxide. The alkaline and urea electrolyzer formed by VTe2@ZnFeTe/NF requires an operating voltage of 1.58 V and 1.46 V to yield a current density of 10 mA cm−2 respectively. Density functional theory analysis reveals that the superb activity of VTe2@ZnFeTe/NF is related to its optimal adsorption free energy, extended electroactive centers, excellent charge transfer ability, and reasonable density of states near the Fermi level. These findings provide new insights for the design of transition metal telluride heterointerfaces as catalysts for water and urea electrolyzers.

Low-temperature synthesis of colloidal few-layer WTe2 nanostructures for electrochemical hydrogen evolution

High-quality transition metal tellurides, especially for WTe2, have been demonstrated to be necessarily synthesized under close environments and high temperatures, which are restricted by the low formation Gibbs free energy, thus limiting the electrochemical reaction mechanism and application studies. Here, we report a low-temperature colloidal synthesis of few-layer WTe2 nanostructures with lateral sizes around hundreds of nanometers, which could be tuned the aggregation state to obtain the nanoflowers or nanosheets by using different surfactant agents. The crystal phase and chemical composition of WTe2 nanostructures were analyzed by combining the characterization of X-ray diffraction and high-resolution transmission electron microscopy imaging and elements mapping. The as-synthesized WTe2 nanostructures and its hybrid catalysts were found to show an excellent HER performance with low overpotential and small Tafel slope. The carbon-based WTe2–GO and WTe2–CNT hybrid catalysts also have been synthesized by the similar strategy to study the electrochemical interface. The energy diagram and microreactor devices have been used to reveal the interface contribution to electrochemical performance, which shows the identical performance results with as-synthesized WTe2–carbon hybrid catalysts. These results summarize the interface design principle for semimetallic or metallic catalysts and also confirm the possible electrochemical applications of two-dimensional transition metal tellurides.

Dependence of Transition-Metal Telluride Phases on Metal Precursor Reactivity and Mechanistic Implications.

Modern bottom-up synthesis to nanocrystalline solid-state materials often lacks the reasoned product control that molecular chemistry boasts from having over a century of research and development. In this study, six transition metals including iron, cobalt, nickel, ruthenium, palladium, and platinum were reacted with the mild reagent didodecyl ditelluride in their acetylacetonate, chloride, bromide, iodide, and triflate salts. This systematic analysis demonstrates how rationally matching the reactivity of metal salts to the telluride precursor is necessary for the successful production of metal tellurides. The trends in reactivity suggest that radical stability is the better predictor of metal salt reactivity than hard-soft acid-base theory. Of the six transition-metal tellurides, the first colloidal syntheses of iron and ruthenium tellurides (FeTe2 and RuTe2) are reported.

Defect Engineering in Two-Dimensional Layered PdTe2 for Enhanced Hydrogen Evolution Reaction

As a fascinating innovative class of effective catalysts for hydrogen evolution reaction (HER), transition-metal tellurides have emerged as attractive materials, but they are still suffering from their intrinsic activity for practical applications. Defect engineering constitutes a promising strategy to optimize the electronic configuration of the catalyst and further improve the HER activity. Herein, we present the successful fabrication of PdTe2-based catalysts with three different types of vacancies (d-PdTex), including single Pd, Te defect site, and double Te defect sites, by using a two-step method. The obtained d-PdTex demonstrated a remarkable HER activity with an overpotential of 76 mV at 10 mA cm–2 without iR compensation, which is far lower than that of bulk PdTe2 (259 mV). The procedure followed in this work may be extended to generate defect sites in a range of different two-dimensional materials, thus further expanding their potential application fields.

Dual Integrating Oxygen and Sulphur on Surface of CoTe Nanorods Triggers Enhanced Oxygen Evolution Reaction.

The bottleneck of large-scale implementation of electrocatalytic water-splitting technology lies in lacking inexpensive, efficient, and durable catalysts to accelerate the sluggish oxygen evolution reaction kinetics. Owing to more metallic features, transition metal telluride (TMT) with good electronic conductivity holds promising potential as an ideal type of electrocatalysts for oxygen evolution reaction (OER), whereas most TMTs reported up to now still show unsatisfactory OER performance that is far below corresponding sulfide and selenide counterparts. Here, the activation and stabilization of cobalt telluride (CoTe) nanoarrays toward OER through dual integration of sulfur (S) doping and surface oxidization is reported. The as-synthesized CoO@S-CoTe catalyst exhibits a low overpotential of only 246mV at 10mAcm-2 and a long-term stability of more than 36h, outperforming commercial RuO2 and other reported telluride-based OER catalysts. The combined experimental and theoretical results reveal that the enhanced OER performance stems from increased active sites exposure, improved charge transfer ability, and optimized electronic state. This work will provide a valuable guidance to release the catalytic potential of telluride-based OER catalysts via interface modulating engineering.

Recent Advances in Transition Metal Tellurides (TMTs) and Phosphides (TMPs) for Hydrogen Evolution Electrocatalysis.

The hydrogen evolution reaction (HER) is a developing and promising technology to deliver clean energy using renewable sources. Presently, electrocatalytic water (H2O) splitting is one of the low-cost, affordable, and reliable industrial-scale effective hydrogen (H2) production methods. Nevertheless, the most active platinum (Pt) metal-based catalysts for the HER are subject to high cost and substandard stability. Therefore, a highly efficient, low-cost, and stable HER electrocatalyst is urgently desired to substitute Pt-based catalysts. Due to their low cost, outstanding stability, low overpotential, strong electronic interactions, excellent conductivity, more active sites, and abundance, transition metal tellurides (TMTs) and transition metal phosphides (TMPs) have emerged as promising electrocatalysts. This brief review focuses on the progress made over the past decade in the use of TMTs and TMPs for efficient green hydrogen production. Combining experimental and theoretical results, a detailed summary of their development is described. This review article aspires to provide the state-of-the-art guidelines and strategies for the design and development of new highly performing electrocatalysts for the upcoming energy conversion and storage electrochemical technologies.

Sandwich-type N-C@CoTe2@C anode: a stress-buffer nanostructure for stable sodium-ion storage.

Transition metal tellurides (TMTes) have received extensive attention for high specific energy sodium-ion batteries (SIBs) due to their high volumetric specific capacity. However, the continuous capacity attenuation arising from the huge volumetric strain during sodiation/desodiation impedes practical applications. Here, we report a "sandwich-type" carbon confinement strategy that entraps cobalt ditelluride (CoTe2) nanocrystals between two carbon layers. Porous cellulose-derived fibres were employed as the inner carbon framework to construct fast conductive circuits and provide an abundant site for anchoring CoTe2 nanocrystals. Polyvinylpyrrolidone (PVP)-derived carbon layers act as carbon armour to encapsulate CoTe2 nanocrystals, inhibiting their volume change and structural pulverization during repeated sodium intercalation/deintercalation. Benefiting from the exquisite structural design, the N-C@CoTe2@C electrode exhibits excellent cycling stability for over 3000 cycles at 2.0 A g-1 and rate performance (113.8 mA h g-1 at 5.0 A g-1). Moreover, ex situ XRD/TEM and kinetic tests revealed a multistep conversion reaction mechanism and a battery-capacitive dual-model Na-storage process. This work provides a new perspective on the development of low-cost and straightforward techniques for fabricating long-life commercial SIB anode materials.

Strengthening ion uptake and mitigating volume change via bimetallic telluride heterojunction for ultrastable K-ion hybrid capacitors

Unitary transition-metal tellurides are appealing to supersede their oxide and sulfide congeners in the realm of K-ion storage because of advanced electrical conductivity. Nevertheless, the marked volume expansion of tellurides during K+ uptake/release giving rise to rapid capacity decay remains a daunting obstacle. Distinct from the previously reported singular telluride configurations, bimetallic heterojunction comprising Mo-Co telluride moiety and dual-carbon encapsulation is developed in this study to endow durable K-ion storage. Density functional theory calculations unlock the synergistic effects of bimetallic Mo-Co tellurides with respect to augmenting electrical conductivity and favoring K-ion adsorption. In situ transmission electron microscopy analysis clearly reveal the structural evolution of bimetallic Mo-Co telluride during a discharge/charge cycle, showing a mitigated volume expansion rate of 2.37 %. Accordingly, the heterojunction exhibits excellent cycling stability (160 mAh/g for 2000 cycles at 1.0 A/g) and favorable capacity output (322 mAh/g at 0.2 A/g), outperforming unitary MoTe2 or CoTe2 counterparts. Thus-derived K-ion hybrid capacitor full-cell manifests elongated lifespan over 6000 cycles at 1.0 A/g. This telluride heterojunction material might offer a valuable reference to rendering high-performance potassium-based energy storage devices.

Vacancy-Mediated Anomalous Emission Characteristics of Size-Confined Semiconducting CoTe2.

Transition-metal tellurides (TMTs) are promising materials for "post-graphene age" nanoelectronics and energy storage applications owing to their industry-standard compatibility, high electron mobility, large spin-orbit coupling (SOC), etc. However, tellurium (Te) having a larger ionic radius (Z = 52) and broader d-bands endows TMTs with semimetallic nature, restricting their application in photonic and optoelectronic domains. In this work, we report the optical properties of the quantum-confined semiconducting phase of cobalt ditelluride (CoTe2) for the first time, exhibiting excellent two-color band photoabsorption attributes covering the UV-visible and near-infrared regions. Furthermore, novel excitonic resonances (X) of size-varying CoTe2 nanocrystals and quantum dots (QDs) are indicated by their temperature-dependent emission characteristics, which are attributed to the splitting of band edge states via confinement. On the other hand, the sudden rupture of the large-area CoTe2 nanosheets via ultrasonication incorporates Co vacancy-mediated localized trap states within the band gap, which is attributed to the superior room-temperature photoluminescence (PL) quantum yield of QDs and further corroborated using Raman analysis and atomistic density functional theory (DFT) simulations. Most interestingly, the excitonic peak of CoTe2 QDs reveals a unique positive-to-negative thermal quenching transition phenomenon, owing to the thermal activation of nonradiative surface trap states. These results introduce an exciting approach for the defect-mediated color-saturated light emission that paves the way for solution-processed telluride-based QD light-emitting diodes.

Substrate dependent thermal conductivity in Td‐WTe2 using micro‐Raman spectroscopy

AbstractTungsten ditelluride (WTe2) is a member of the transition metal telluride (TMT) family, which is emerging as a promising material for electronic applications. The study of thermal characteristics of WTe2 is important to understand heat dissipation in electronic devices. As heat dissipation and thermal transport are dependent on the choice of substrates, it is imperative to understand the effect of different substrates on the thermal conductivity of WTe2. Moreover, the comprehension of out‐of‐plane thermal conductivity is important when dealing with heat management of multiple layers of 2D materials and their heterostructures. In this work, we report the thermal conductivity of few‐layer thick exfoliated Td phase WTe2 flakes over four different substrates, namely bare Si, 90 nm SiO2, 290 nm SiO2, and poly(methyl methacrylate) (PMMA). Micro‐Raman spectroscopy has been employed to estimate the out‐of‐plane thermal conductivity by considering two characteristics out of plane Raman modes A15 and A12, as they are more sensitive to temperature variation compared with other modes. Out of the four substrates, WTe2 shows the lowest conductivity over PMMA and highest over 290 nm SiO2/Si for similar thicknesses, which arises due to the low thermal conductivity and molar mass of PMMA with respect to the molar mass of WTe2 giving rise to the lowest thermal conductivity. Our results also show that the thermal conductivity of WTe2 increases with the decrease in thickness. The authors hope that these findings shall provide a compound perspective on the thermal behavior of WTe2 with respect to different substrates.

Fe-doped NiTe2/Ni2P grown in situ on Ni foam as an efficient electrocatalyst for oxygen evolution reaction

Self-supported nanoparticle electrocatalysts with multiple active sites and porosity have a bright prospect in the direction of oxygen evolution reaction (OER). In this work, a three-dimensional (3D) porous nanoparticle Fe-NiTe 2 /Ni 2 P is presented, which exhibits outstanding electrocatalytic activity and excellent stability. Specifically, the OER activity of Fe-NiTe 2 /Ni 2 P requires only 190 mV overpotential at the current density of 10 mA cm -2 , which is the first time the overpotential of tellurides gets within 200 mV. It is because the rough porous 3D structure leads to a large number of exposed active sites, allowing enough channels to release oxygen and perform mass exchange. In addition, Fe doping can modulate the electronic structure of the catalyst, accelerate the electron transfer, and thus improve the activity of the catalyst. The catalyst remained stable in 1 M KOH solution for 22 h, indicating that it has strong corrosion resistance. In this work, a simple, efficient, low-cost and corrosion resistant iron-doped transition metal telluride electrocatalyst has been synthesized, which provides a valuable way for the study of water electrolysis. ● A three-dimensional (3D) porous nanoparticle Fe-NiTe 2 /Ni 2 P was synthesized as outstanding OER electrocatalyst. ● It requires a small overpotential of 190 mV to achieve the current density of 10 mA cm -2 for OER in 1 M KOH solution. ● It is the first time that the overpotential of tellurides is below 200 mV.

Confining CoTe2-ZnTe heterostructures on petal-like nitrogen-doped carbon for fast and robust sodium storage

Two-phase or multiphase engineering is contributed to realizing rapid electron/ion transfer kinetics for transition metal tellurides in sodium-ion batteries (SIBs). However, the large volume variation and fundamental storage mechanism of these materials remain unsolved. Herein, petal-like N-doped carbon-confined CoTe2-ZnTe heterostructures (CoZn-Te/NC) are fabricated as anodes in SIBs via a facile bimetal-organic framework-derived strategy. Benefiting from the abundant phase interfaces and dual-defective sites, CoZn-Te/NC composites have fast electrons/ions diffusion and superior pseudocapacitive property. Particularly, introducing a petal-like nitrogen-doped carbon inhibits the particle agglomeration and alleviates volume expansion, thus improving structural stability during cycling. The CoZn-Te/NC exhibits a superior rate capacity of 106 mAh/g at 10 A g−1 and a high reversible capacity of 150 mAh/g at 1.0 A g−1 over 600 long-term cycles. The unique conversion and alloying/de-alloying reaction mechanisms of CoZn-Te/NC are revealed by the in-situ and ex-situ techniques. This work gives promising insights for designing high-performance electrode materials by phase interface, doping, and confining strategy.

Transition metal tellurides as emerging catalysts for electrochemical water splitting

Renewable energy powered electrochemical water splitting has been recognized as a sustainable and environmentally-friendly way to produce green hydrogen, which is an important vector to decarbonize the transport sector and hard-to-abate industry, able to contribute to achieving global carbon neutrality. For large-scale deployment of water electrolyzers, it is essential to develop efficient and durable electrocatalysts—one of key components determining the electrochemical performance, based on cheap and earth-abundant materials. To this end, transition metal tellurides (TMTs) have recently emerged as a promising alternative to the conventional platinum group metals for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). This review article provides a brief account of the latest development in TMT-based HER and OER catalysts, with a focus on various strategies developed to improve the catalytic performance, such as nanostructure engineering, composition engineering, and heterostructuring/hybridization. Perspectives of future research on TMT-based catalysts are also shortly outlined.

Nanostructures and catalytic atoms engineering of tellurium‐based materials and their roles in electrochemical energy conversion

AbstractWith the dramatic developments of renewable and environmental‐friendly electrochemical energy conversion systems, there is an urgent need to fabricate durable and efficient electrocatalysts to address the limitation of high overpotentials exceeding thermodynamic requirements to facilitate practical applications. Recently, tellurium‐based nanomaterials (Te NMs) with unique chemical, electronic, and topological properties, including Te‐derived nanostructures and transition metal tellurides (TMTs), have emerged as one of the most promising electrocatalytic materials. In the absence of comprehensive and guiding reviews, this review comprehensively summarizes the main advances in designing emerging Te NMs for electrocatalysis. First, the engineering strategies and principles of Te NMs to enhance their electrocatalytic activity and stability from the nanostructures to the catalytic atoms are discussed in detail, especially on the chemical/physical/multiplex templating strategies, heteroatom doping, vacancy/defect engineering, phase engineering, and the corresponding mechanisms and structure‐performance correlations. Then, typical applications of Te NMs in electrocatalysis are also discussed in detail. Finally, the existing key issues and main challenges of Te NMs for electrocatalysis are highlighted, and the development trend of Te NMs as electrocatalysts is expounded. This review provides new concepts to guide future directions for developing Te NMs‐based electrocatalysts, thereby promoting their future wide applications in electrochemical energy systems.

Magnetic and Electrical Properties of Ni3Te2 Single Crystals Grown by Physical Vapor Transport Technique

The transition metal tellurides (TMTs) have attracted much attention due to their rich properties in both fundamental research and applications. Among all the TMTs, the study of Ni3Te2 large single crystals is rare. By using the physical vapor transport technique, Zhe Li, Jun-Yi Ge, and co-workers have successfully grown Ni3Te2 single crystals with unique hexagonal cross section and a tubular shape (see article number 2200037). The crystal structure, the electrical transport and magnetic properties, and band structures are investigated in detail. It is revealed that Ni3Te2 exhibits a metallic behavior with the coexistence of ferromagnetism and antiferromagnetism.

Two step synthesis of ultrathin transition metal tellurides

Transition metal tellurides (TMTs) are an exciting group of two-dimensional materials with a wide variety of polytypes and properties. Here, we demonstrate a simple and versatile two-step method for producing MoTe2, WTe2, and PtTe2 films via tellurization of thin metals at temperatures between 400 and 700 °C. Across this temperature range, monoclinic 1T′ phase of MoTe2, orthorhombic Td phase of WTe2, and hexagonal 2H phase of PtTe2 were formed. Based on x-ray diffraction and Raman analysis, temperatures greater than 600 °C were found to produce the best quality MoTe2 and WTe2. In contrast, lower temperatures (400 °C) were preferred for PtTe2, which becomes discontinuous and eventually decomposes above 650 °C. The presence of H2 in the tellurization process was critical to facilitate the formation of H2Te, which is known to be more reactive than Te vapor. In the absence of H2, neither MoTe2 nor WTe2 formed, and although PtTe2 was formed under pure N2, the crystal quality was significantly reduced. Temperature-dependent resistivity (ρ) measurements were performed on the best quality TMT films revealing all films to be highly conductive. MoTe2 showed metallic behavior up to 205 K where it underwent a phase transition from the semimetallic Td to semiconducting 1T′ phase. WTe2 exhibited a consistent semiconducting behavior with a small positive increase in ρ with decreasing temperature, and PtTe2 showed a metallic dependence from 10 K up to room temperature. Spectroscopic ellipsometry for TMT films provides complex optical constants n and k from ultraviolet to infrared.

Ultrahigh yield and large-scale fast growth of large-size high-quality van der Waals transition-metal telluride single crystals

Stable, rapid, and large-scale production of high-quality, large-size two-dimensional (2D) van der Waals single crystals is an important prerequisite for realizing the potential of highly integrated 2D devices. Here, we report a chloride-mediated chemical vapor transport (CVT) approach to achieve large-scale production of MoTe 2 and WTe 2 single crystals with lateral sizes up to 2 cm and extremely high quality. The largest magnetoresistance and carrier mobility can reach 170% and 1,390.09 cm 2 V -1 s -1 for 2H-MoTe 2 crystals and 506,017% and 11,952.10 cm 2 V -1 s -1 for Td-WTe 2 crystals, respectively, and all are among the best reported ones. Compared with the conventional CVT method, which has a long growth cycle and much reactive reagent surplus, the growth speed of the current method is about 73 to 9,144 times faster, with ultrahigh yields of nearly 100%. The high crystallinity guarantees the crystals can be easily exfoliated to large-scale 2D crystals down to monolayers for assembling 2D high-performance devices. • High-yield and large-scale fast growth of van der Waals TMT single crystals • TMTs exhibit high crystalline quality and good electrical transport properties • TMTs monolayers with millimeter-scale lateral dimensions • TMT-based field-effect transistor and Hall device exhibit stable performance Obtaining high-quality, large-size 2D vdW single crystals is an important prerequisite for realizing the potential of highly integrated 2D devices. Here, Yang et al. report a chloride-mediated CVT approach to achieve ultrahigh-yield and large-scale fast growth of centimeter-sized transition-metal telluride single crystals with extremely high quality.

In-situ engineered heterostructured nickel tellur-selenide nanosheets for robust overall water splitting

Due to the large Gibbs free energy of metal telluride for hydrogen generation, tellurium (Te) based materials are rarely reported as catalysts for overall water splitting. Herein, a facile hydrothermal method is used to engineer the stacked flower-like NiTe-NiSe nanosheets, thus nearing the application of transition metal telluride in clean and renewable energy field. Thanks to the hollow flower-shaped catalyst assembled with nanosheets, the active surface area of the optimized electrode material is 20 times larger than that of a single NiTe/NFF or NiSe/NFF, causing low overpotentials for delivering a current density of 10 mA cm−2 (j10) in the hydrogen (HER, 76 mV) and oxygen (OER, 164 mV) evolution processes. The OER activity of NiTe-NiSe/NFF exceeds that of benchmarked RuO2 even at moderate current densities above j115. Based on the results of experiments and DFT calculations, the unexpected high catalytic performance of NiTe-NiSe/NFF is attributed to the formed heterointerfaces and mismatched crystal lattice of NiTe, which effectively optimize the electronic structure through the phase synergy and cause a low adsorption free energy for the reactive intermediates.