One-dimensional Transition Metal Research Articles

Tuning the Structure of Pd@Ni-Co Nanowires and Their Electrochemical Properties.

One-dimensional transition metal materials are promising supports for precious metals used in energy production processes. Due to their electrochemical properties, 3d-group metals (such as Ni, Co, and Fe) can actively interact with catalysts by a strong metal-support interaction. This study shows that changing the Ni:Co ratio makes it possible to modulate the structure of the catalyst supports, which, in turn, provides a tool for designing their electrical and electrochemical properties. For example, Ni1-Co9 shows the highest electrical conductivity (5.8-10-4 S/cm) among all of the materials examined. On the contrary, the Pd@Ni7-Co3 system presents the highest mass activity (>2000 mA mg-1) at 0.7 V, exceeding by several times that of commercial Pt/C (>300 mA mg-1) at the same potential. Our study opens the gateway for applications of bimetallic transition metal nanowires in catalytic conversion and energy production processes.

Half-metallic magnetism in 2D MX2 (M = V, Cr, Mn, and Fe; X = S, Se, and Te) intercalated with 1D MX chains

Intercalation has attracted considerable attention due to its extensive ability to modify the electronic, optical, and magnetic properties of two-dimensional (2D) layered nanomaterials. Typically, dispersed atoms or molecules are inserted into the van der Waals gap of the 2D materials. Recently, Guo et al. experimentally reported the novel VS2–VS superlattice, where the intercalation takes the form of atomic chain arrays. In this study, we employed the first-principles calculations based on density functional theory to investigate a series of analogous 2D MX2–MX–MX2 nanomaterials, which, consisting of 2D transition metal dichalcogenide bilayers, intercalated with a one-dimensional transition metal chalcogenide MX chain array, forming a hotdog-like structure. Some of the 2D MX2–MX–MX2 are thermally and dynamically stable, suggesting their potential for experimental fabrication similar to VS2–VS–VS2. MnS2–MnS–MnS2 and MnSe2–MnSe–MnSe2 have been found to exhibit ferromagnetic half-metallic properties. In addition, VSe2–VSe–VSe2, CrS2–CrS–CrS2, and CrSe2–CrSe–CrSe2 have been found to be thermally and dynamically stable. Under appropriate external stress, doping, or bias, they could become ferromagnetic half-metals, revealing their potential for spintronic applications.

Uniform one-dimensional hierarchical CoOx-N-C feather duster breaking the activity-stability trade-off for hydrogenation reactions

Carbon-based non-precious metal/oxide catalysts always face the dilemma of a trade-off between high activity and long-term stability in hydrogenation reactions, detrimental to their practical applications. Herein we propose a unique and uniform feather duster-type catalyst as a promising concept to solve this activity-stability trade-off. The feather duster is composed of both exposed and embedded active sites, that can facilitate substrate adsorption/activation and can be resistant against site leaching during the non-neutral aqueous phase reactions. We constructed a uniform one-dimensional hierarchical transition metal oxide-containing N-doped carbon (TMO-N-C), especially for CoOx-N-C (x = 1.0 or 1.3), based on a controlled depolymerization-reassembly strategy before morphology-conserved pyrolysis. The uniform, thermally stable feather duster-type precursor was induced in view of the interaction between cobalt 2-methylimidazolate framework (ZIF-67) polyhedron and zinc-trimesic acid (ZnBTC) fiber in water. And subsequent pyrolysis leads to a uniform CoOx-N-C nanoarchitecture with numerous nanorods planted on a single fiber. The resulting CoOx-N-C proves to be highly efficient for 4-nitrophenol reduction, delivering a high activity factor of 7.32 s−1 g−1 with exceptional long life over 10 cycles, thus ranking CoOx-N-C one of the best transition metal oxide catalysts for hydrogenation reactions. This research overcomes the dilemma that either high activity contributed by surface active sites or superior stability provided by embedded ones, offering valuable guidance for rational design of efficient metal/oxide catalysts.

Lithium superoxide-based high rate Li-Air batteries enabled by Di-iridium sulfur bridge active sites

Li-oxygen (Li-O2) batteries can potentially provide much higher energy density than Li-ion batteries; however, the practical application of these batteries is hindered due to several drawbacks such as low current rates and high overpotential for the charging process. In this paper, we report a novel Li-Air battery system that operates under high current rates (up to 1mAcm−2) with LiO2 as the primary discharge product instead of the commonly reported Li2O2. This LiO2 based battery at high rates is through a combination of an as-synthesized new one-dimensional (1D) transition metal trichalcogenide mid-entropy alloy of SnIrS3.6 as a cathode catalyst and an electrolyte blend with a SnI2 bi-functional additive. It is revealed that SnIrS3.6 has a microporous structure composed of six- and five-coordinated metal atoms, forming octahedral and triangular bipyramids which has not been observed in other layered chalcogeide materials. DFT calculations reveal that the SnIrS3.6 structure can result in LiO2 formation through di-iridium sulfur bridge active sites that results in strong binding of O2 and LiO2 preventing disproportionation to Li2O2 and enabling high rates. This finding will open a new perspective in designing advanced LiO2-based Li-O2 batteries for real practices.

One-Dimensional Layered Sodium Vanadate Nanobelts: A Potential Aspirant for High-Performance Supercapacitor Applications

The one-dimensional (1D) transition metal oxide (TMO) nanostructures have significant advantages in electrochemical energy storage fields. To date, simplifying the processing techniques and improving the yield without compromising the quality are one of the top priorities in pushing these TMO materials for scalable energy storage applications. This study presents a simple ultrasonic-assisted chemical route to prepare Na2V6O16 (NVO) nanobelts. The X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, and transmission electron microscopy characterizations are used to confirm the formation of 1D NVO nanobelt structures. The growth mechanism for the formation of NVO nanobelts is also provided. Moreover, these synthesized NVO nanobelts are used as an electrode material for supercapacitor (SC) applications, which exhibit a specific capacitance of 455 F g–1 at 0.5 A g–1 with typical capacitive behavior. An asymmetric coin cell SC device of activated carbon//NVO is also fabricated. This fabricated device delivers a high energy density of 42.4 W h kg–1 and a high power density of 4.3 kW h kg–1, along with 80% capacity retention after 5000 cycles. The 1D NVO nanobelt structures can be considered a promising cathode material with superior rate capability and high capacitance for SC applications.

First-principles investigation of ferroelectric and piezoelectric properties in one-dimensional transition metal oxytetrahalides

We perform first-principles density functional theory calculations to systematically investigate electronic structures of a quasi-one-dimensional $M\mathrm{O}{X}_{4}$ ($M=\mathrm{Cr},\mathrm{Mo},\mathrm{W}$, and $X=\mathrm{F},\mathrm{Cl},\mathrm{Br}$) materials consisting of weakly coupled one-dimensional chains. The compositional dependence on the ferroelectric and piezoelectric properties such as switching polarization, energy barriers, Born effective charges, and piezoelectric coefficients are investigated. We find that the majority of the $M\mathrm{O}{X}_{4}$ systems exhibit sizable polarization and large piezoelectric coefficients comparable to conventional ferroelectrics. More importantly, we find that the energy cost of forming a ${180}^{\ensuremath{\circ}}$ domain walls is negligibly small due to the weak interchain coupling, having an atomically thin domain wall with almost no reduction in the local polarization. The robust ferroelectric switching, atomically thin ferroelectric domain wall, and large piezoelectric coefficients make the $M\mathrm{O}{X}_{4}$ family of materials potential candidates for applications for efficient electronic devices such as high-density ferroelectric memories and high-resolution pressure sensors.

Multiplet effects in the electronic correlation of one-dimensional magnetic transition metal oxides on metals

We use the constrained random phase approximation (cRPA) method to calculate the Hubbard $U$ parameter in four one-dimensional magnetic transition metal atom oxides of composition XO$_2$ (X = Mn, Fe, Co, Ni) on Ir(100). In addition to the expected screening of the oxide, i.e., a significant reduction of the $U$ value by the presence of the metal substrate, we find a strong dependence on the electronic configuration (multiplet) of the X($d$) orbital. Each particular electronic configuration attained by atom X is dictated by the O ligands, as well as by the charge transfer and hybridization with the Ir(100) substrate. We find that MnO$_2$ and NiO$_2$ chains exhibit two different screening regimes, while the case of CoO$_2$ is somewhere in between. The electronic structure of the MnO$_2$ chain remains almost unchanged upon adsorption. Therefore, in this regime, the additional screening is predominantly generated by the electrons of the neighboring metal surface atoms. The screening strength for NiO$_2$/Ir(100) is found to depend on the Ni($d$) configuration in the adsorbed state. The case of FeO$_2$ shows an exceptional behavior, as it is the only insulating system in the absence of metallic substrate and, thus, it has the largest $U$ value. However, this value is significantly reduced by the two mentioned screening effects after adsorption.

Role of macrocyclic salen-type Schiff base ligands in one-dimensional Co(II) complexes for superior activities toward oxygen reduction/evolution reactions

Developing high activities, stable, non-precious metal based bi-functional electrocatalysts oxygen evolution/reduction reactions (OER/ORR) in rechargeable metal-air batteries and regenerative fuel cell technologies is essential for future energy conversion and storage. In this work, the potential of utilizing the synthesized one-dimensional transition metal salen-type complexes (TM-SCs) as bi-functional electrocatalysts of ORR and OER is systematically explored by computational screening approach. The results demonstrate that different types of macrocyclic ligands, including N2O2, N3O and N4 as donor groups around the active sites, govern the OER/ORR catalytic performances. Co–SCs with N2O2 ligands exhibit the highest bifunctional catalytic activities. In particular, low limiting overpotentials of 0.22 V for OER and 0.33 V for ORR can be observed on Co sites, which are even superior to those of noble metal catalysts. Analyzing the linear relationships between the adsorption strength of intermediates and the overpotentials shows that the origin of excellent electrocatalytic performance is the smaller slope (0.86) for OOH∗ vs OH∗ on TM-SCs compared to metal surfaces, resulting in strengthened binding of the OOH∗ intermediate. Besides, the adsorption energies of the intermediates bound on Co–N2O2 are close to the ideal values, while too strong on the Co–N3O and Co–N4 catalysts. By applying external strains, the adsorption strengths of reaction intermediates can be further modulated due to the tunable d-band centers, and the resulting ORR/OER activities are further boosted. Considering that the Co salen-based chain has been synthesized experimentally, this work highlights the excellent electrocatalytic performances of this new material and devises novel strategy by straining for catalyst optimizations.

Solvent-Free Preparation of Closely Packed MoS2 Nanoscrolls for Improved Photosensitivity.

Due to their enhanced light absorption efficiency, one-dimensional (1D) transition metal dichalcogenide (TMDC) nanoscrolls derived from two-dimensional (2D) TMDC nanosheets have shown excellent optoelectronic properties. Currently, organic solvent and alkaline droplet-assisted scrolling methods are popular for preparing TMDC nanoscrolls. Unfortunately, the adsorption of organic solvent or alkaline impurities on TMDC is inevitable during the preparation, which affects the optoelectronic properties of TMDC. In this work, we report a solvent-free method to prepare closely packed MoS2 nanoscrolls by dragging a deionized water droplet onto the chemical vapor deposition grown monolayer MoS2 nanosheets at 100 °C (referred to as MoS2 NS-W). The as-prepared MoS2 NS-W was well characterized by optical microscopy, atomic force microscopy, and ultralow frequency (ULF) Raman spectroscopy. After high temperature annealing, the height of MoS2 nanoscrolls prepared using an ethanol droplet (referred to as MoS2 NS-E) greatly decreased, indicating the loss of encapsulated ethanol in MoS2 NS-E. While the height of MoS2 NS-W was almost unchanged under the same conditions, implying that no water was embedded in the scroll. Compared to the MoS2 NS-E, the MoS2 NS-W shows more ULF breathing mode peaks, confirming the stronger interlayer interaction. In addition, the MoS2 NS-W shows a higher Young's modulus than MoS2 NS-E, which could arise from the closely packed scroll structure. Importantly, the MoS2 NS-W device showed a photosensitivity 1 order of magnitude higher than that of the MoS2 NS-E device under blue, green, and red lasers, respectively. The decreased photosensitivity of MoS2 NS-E was attributed to the larger dark current, which might be assigned to the adsorbed ethanol between the adjacent layers in MoS2 NS-E. Our work provides a solvent-free method to prepare closely packed MoS2 nanoscrolls at large scale and demonstrates their great potential for high-performance optoelectronic devices.

Charge Separated One-Dimensional Hybrid Cobalt/Nickel Phosphonate Frameworks: A Facile Approach to Design Bifunctional Electrocatalyst for Oxygen Evolution and Hydrogen Evolution Reactions.

Two new organoamine templated one-dimensional transition metal phosphonate compounds are synthesized, and their bifunctional electrocatalytic activities are examined in highly alkaline and acidic media. Compared with state-of-the-art materials, the cobalt phosphonate system is a new fabrication of sustainable and highly efficient catalysts toward electrochemical water splitting systems.

1D chain structure in 1T′-phase 2D transition metal dichalcogenides and their anisotropic electronic structures

The quasi-metallic 1T'-phase is one of the notable polymorphic two-dimensional transition metal dichalcogenide phases and possesses a unique structure, comprising a one-dimensional zigzag transition metal chain along a single axis. This structure gives rise to unprecedented anisotropic electronic properties, including new anisotropic mid-infrared plasmon excitations. The emergence of highly correlated electronic modes in such anisotropic systems is relevant to the intrinsic electronic and optical properties of two-dimensional transition metal dichalcogenides. In this review, we highlight the unique features of these materials in their anisotropic quasi-metallic 1T'-phase, not found in the other structural phases. We discuss how this anisotropic structure brings about the onset of unique physical phenomena such as the electronic band inversion, anomalously large magnetoresistance, and intrinsic or induced superconductivity in multiple transition metal dichalcogenide systems. The unique structural properties of these systems have led to spatially resolved transport and optical properties that can be further manipulated for use in a wide variety of applications ranging from nano-electronics to ultra-sensitive photonic systems but also their incorporation in high performance field-electric transistors, photodetectors, hydrogen evolution reactions, and piezoelectric devices cater to technologies of the future.

1D metal-dithiolene wires as a new class of bi-functional oxygen reduction and evolution single-atom electrocatalysts

Discovering low-cost, durable and highly active electrocatalysts with reduced use of precious platinum group metals (PGM) as catalysts for the hydrogen evolution reaction (HER), the oxygen reduction reaction (ORR), and the oxygen evolution reaction (OER) is a key step for large-scale adaptation of fuel cells, electrolyzers, and metal-air batteries. Here we explore the stability and reaction mechanisms of synthesized one-dimensional transition metal dithiolene wire (TM-DWs, TM = Cr – Cu, Rh, Ir, Pt, Pd) for the ORR and the OER in acid solution by density functional theory (DFT) calculations. Our calculations reveal that Co-DW intrinsically exhibits high catalytic activity for bi-functional ORR/OER with low limiting overpotentials (η) of 0.46/0.45 V via four-electron reactions. These low limiting overpotentials arise from modified scaling relations by strengthening the binding free energy of OOH* compared to OH* on TM-DWs, yielding universal minimum ORR/OER overpotentials of η = 0.28/0.22 V, remarkably decreased compared to both metal and oxide surfaces (ηideal = 0.37 V). By applying uni-axial strain, the adsorption strength of reaction intermediates on TM reactive sites can be optimized due to shifts in d-band centers. Our findings provide valuable insight into rational design of non-precious metals based electrocatalysts, and demonstrate a new strategy of tuning adsorptions via uni-axial strain to develop efficient bifunctional electrocatalysts of ORR/OER under optimal conditions.

Boosting charge storage in 1D manganese oxide-carbon composite by phosphorus-assisted structural modification for supercapacitor applications

For electrochemical energy storage, the inevitable oxidation and phase evolution process in many low-valent one-dimensional (1D) transition metal oxides displayed gradually optimized electrochemical characteristics, nevertheless, it is generally sluggish in dynamics. Accelerating this process to achieve efficient energy output remains a significant challenge. Herein, with 1D Mn3O4 as a demo, it was revealed that phosphorus species (P) acted as the active species-like effects, thus robustly accelerating phase evolution process from 1D to two-dimensional (2D) oxides with enhanced charge-storage kinetics. The P-modulated Mn3O4 (P–Mn3O4) presents the optimized surface chemistry properties, unsaturated coordination sites and internal disorders, then the accompanied P leaching in P–Mn3O4 further leads to the formation of low-crystallinity MnO2 with O vacancies and abundant grain boundaries for a highly enhanced capacitive performance. As such, the P–Mn3O4-coupled carbon can reach the areal capacitance of 8743 ​mF ​cm−2 (high mass loading: 44.2 ​mg ​cm−2) at 1 ​mA ​cm−2 after fast phase evolution, together with the high mass and volume capacitances of 198 ​F ​g−1 and 113 ​F ​cm−3, respectively. This P-mediated approach to accelerate phase evolution is universal, evidenced by the extensively studied NiCo-based oxides. This contribution would provide a novel and powerful idea to modulate transition metal hybrids and manipulate active species for efficient energy storage and conversion.

Ultrafine Mo-Doped Co2P Nanorods Anchored on Reduced Graphene Oxide as Efficient Electrocatalyst for the Hydrogen Evolution Reaction**Supported by the National Natural Science Foundation of China (Grant Nos. 11874027, 11774124, and 11504126) and the China Postdoctoral Science Foundation (Grant Nos. 2019T120233 and 2017M621198).

One-dimensional (1D) transition metal phosphides (TMPs) with large specific surface areas, high charge transfer efficiency and excellent electrical conductivity have attracted significant attention in hydrogen evolution reaction (HER) as versatile and active catalysts. Herein, the sub-4 nm Mo-Co2P ultrafine nanorods (NRs) anchored on reduced graphene oxide (rGO) were successfully synthesized by a colloidal mesostructured strategy. Electrochemical test results reveal that the Mo-Co2P@rGO electrode exhibits superior activity with overpotentials of 204 mV and Tafel slope of 88 mV/dec for HER at 10 mA/cm2, relative to the Co2P@rGO electrode in 0.5 M H2SO4 solution. This improvement could be ascribed to the Mo doping, which results in more active sites, higher electrical conductivity and faster electron-transfer rates. This versatile strategy will provide a promising pathway for transition metal-doped compounds as an efficient catalyst.

Facile synthesis of mesoporous one-dimensional Fe2O3 nanowires as anode for lithium ion batteries

Abstract One-dimensional (1D) transition metal oxides materials with unique mesoporous structure have potential applications in the energy conversion and storage field. In this work, 1D mesoporous Fe2O3 nanowires growth on strain steel substrate were prepared through a two-step solution method and used as anode materials for lithium batteries. The electrode delivers discharge capacity of 1460 mAh·g−1 at 100 mA g−1 density after 200 cycles. Furthermore, the electrode exhibited outstanding rate capability and its reversible capacity reaches to 700 mAh·g−1 at 800 mA g−1 density. Such excellent cycle performance may ascribe to the capacitive effect caused by the unique mesoporous nanowire structure. This work may provide a facile and efficient method for the preparation of high performance Fe2O3 anode materials.

A review of the α-Fe2O3 (hematite) nanotube structure: recent advances in synthesis, characterization, and applications.

α-Fe2O3 nanotubes are exceptional one-dimensional transition metal oxide materials with low density, large surface area, promising electrochemical and photoelectrochemical properties, which are widely investigated in lithium-ion batteries, photoelectrochemical devices, gas sensors, and catalysis. They have drawn significant attention to the fields of energy storage and conversion, and environmental sensing and remediation due to the increase in the global energy crisis and environmental pollution. Many efforts have been made toward controlling the morphology or impurity doping to improve the intrinsic properties of α-Fe2O3 nanotubes. In this review, we introduce the synthesis methods and physicochemical properties of α-Fe2O3 nanotubes. The fabrication conditions, which are important for the physicochemical properties of materials, are also listed to describe the synthesis processes. Furthermore, the development and breakthrough of various applications in batteries, supercapacitors, photoelectrochemical devices, environmental remediation, and sensors are systematically reviewed. Finally, some of the current challenges and future perspectives for α-Fe2O3 nanotubes are discussed. We believe that this timely and critical mini-review will stimulate extensive studies and attract more attention, further improving the development of the α-Fe2O3 (hematite) nanotube structure.

One-dimensional transition metal dihalide nanowires as robust bipolar magnetic semiconductors.

One-dimensional (1D) materials with robust ferromagnetic ground states are difficult to achieve but provide a significant platform for potential spintronic device applications in future. Herein, a new family of 1D transition metal dihalide (TMCl2; where TM = Cu, Co, Cr) nanowires are proposed by using first-principles calculations. Their dynamic stability is ensured by Born-Oppenheimer molecular dynamics simulations. The electronic structures demonstrate that both CoCl2 and CuCl2 nanowires are promising bipolar magnetic semiconductors (BMSs) and can be converted into 1D half-metal materials by a small amount of carrier doping. The CrCl2 nanowire is an antiferromagnetic semiconductor (AFS). The formation of a BMS is attributed to the superexchange coupling between the Co/Cu atoms through the 3p orbitals in the Cl atoms. By using Monte Carlo simulations, we found that the CoCl2 nanowire has a Curie point of 6 K, while the CuCl2 nanowire has a corresponding Curie point of 14 K. Our results allow us to put forward a strategy to realize 1D BMSs and to design low-dimensional AF spintronic devices.

Efficient growth and characterization of one-dimensional transition metal tellurides inside carbon nanotubes.

Atomically thin one-dimensional (1D) van der Waals wires of transition metal monochalocogenides (TMMs) have been anticipated as promising building blocks for integrated nanoelectronics. While reliable production of TMM nanowires has eluded scientists over the past few decades, we finally demonstrated a bottom-up fabrication of MoTe nanowires inside carbon nanotubes (CNTs). Still, the current synthesis method is based on vacuum annealing of reactive MoTe2, and limits access to a variety of TMMs. Here we report an expanded framework for high-yield synthesis of the 1D tellurides including WTe, an previously unknown family of TMMs. Experimental and theoretical analyses revealed that the choice of suitable metal oxides as a precursor provides a useful yield for their characterization. These TMM nanowires exhibit a significant optical absorption in the visible-light region. More important, electronic properties of CNTs can be tuned by encapsulating different TMM nanowires.

Magnetic Polymer Chains of Transition Metal Atoms and Zwitterionic Quinone

Ab initio calculations based on density functional theory (DFT) including an explicit treatment of the strong electron correlation in the d shell of the transition metal ions have been conducted using the spin-polarized generalized gradient approximation with Hubbard term U (SGGA+U) to investigate systematically the electronic and magnetic properties of a new material class representing one-dimensional transition metal zwitterionic quinone (TM-ZQ) polymers having many potential applications, especially in spintronics. The complete class of 3d transition metals (TMs) are investigated from Sc to Zn. Zn-ZQ is nonmagnetic, since it has a 3d10 configuration. All of the other TM-ZQ polymers are antiferromagnetic semiconductors with the exception of Mn-ZQ that is metallic for the ferromagnetic (FM) and the antiferromagnetic (AFM) spin arrangements and Sc-ZQ and Ti-ZQ which are FM semiconductors. All of these polymer chains have the potential to be produced by on-surface synthesis on metallic surfaces, as was recently shown for Fe-ZQ (Koudia, M.; et al. Nano Res. 2017, 10, 933–940).

Controllable synthesis of Co2P nanorods as high-efficiency bifunctional electrocatalyst for overall water splitting

One-dimensional transition metal phosphides with large specific surface areas and efficient conductivity have the great potential in both hydrogen and oxygen evolution reaction (HER and OER) as bifunctional catalysts, which are at the heart of water splitting. Herein, we firstly report the controllable synthesis of Co2P nanorods through a substrate- and template-free facile phosphating reaction. Electrochemical test results reveal that the synthesized Co2P nanorods exhibit superior bifunctional activity with overpotentials of 87 mV for HER and 310 mV for OER at 10 mA cm−2, respectively, relative to Co2P/CoP branched nanostructure, CoP nanoparticles and commercial Co2P in alkaline media. In addition, the bifunctional Co2P nanorods catalysts enable overall water splitting with a cell voltage of 1.65 V to achieve 10 mA cm−2 and stabilized potentials at different current densities testing over 24 h. Further analysis demonstrate that the remarkably bifunctional activity is contributed to high charge transfer efficiency, large contact area with electrolyte and a large number of exposed active sites provided by the rod-like nanostructure. This work should shed light on an industrialized pathway for the future design of phosphide catalysts to apply to overall water splitting even other emerging energy devices.