Sn-Co Alloy Research Articles

Manipulating d-band center of bimetallic Sn-alloy coupling with carbon nanofibers for high-performance electrocatalytic production of ammonia from nitrate

The production of ammonia from electrochemical nitrate reduction reaction (NO3RR) has emerged as a highly promising approach to replace the conventional “Haber-Bosch” process, but the research progress of this field is still hindered by the absence of a structure–activity relationship for manipulating catalyst structure to promote its catalytic performance. In this study, we chose TMSn (M=Fe, Co, Ni) alloys as the models to evaluate the electronic structure and their NO3RR activity. Alloying various transition metals with Sn allows to regulate charge distribution, thereby modulating the d-band center of the catalysts and further regulating the catalytic activity of NO3RR. Density functional theory (DFT) simulation predicts that CoSn alloy, with the strongest NO3− adsorption and lowest thermodynamic energy barrier, is potentially considered as a highly efficient NO3RR catalyst. With this theoretical guidance, a series of TMSn alloy catalysts with carbon nanofiber (TMSn-CNF) as a support were synthesized via a two-step electrospinning/carbonization strategy. The CNF as a substrate ensures the excellent cycling performance. As a result, a significantly enhanced NO3RR activity with a NH3 yield rate of 42.20 mg h−1 cm−2 at −0.6 V vs. RHE is achieved on CoSn-CNF compared with NiSn-CNF (13.91 mg h−1 cm−2), FeSn-CNF (13.81 mg h−1 cm−2) and Sn-CNF (6.10 mg h−1 cm−2), superior to most of the previously reported catalysts. We have further constructed an aqueous Zn-NO3− battery using CoSn-CNF as the cathode, achieving a remarkable power density of 5.88 mW cm−2. This battery not only generates large quantity of NH3, but also functions as an effective power source.

Morphologies of intermetallic compound phases in Sn-Cu and Sn-Co peritectic alloys during directional solidification

The morphologies of intermetallic phases (IMCs) during directional solidification of the Sn-Cu (L+Cu3Sn→Cu6Sn5) and Sn-Co (L+CoSn→CoSn2) peritectic systems were analyzed. The primary Cu3Sn and peritectic Cu6Sn5 phases in Sn-Cu alloy are IMCs whose solubility ranges are narrow, while both the primary CoSn and peritectic CoSn2 phases in Sn-Co alloy are IMCs whose solubility ranges are nil in equilibrium condition. The experimental results before acid corrosion shows that the dendritic morphology of both the Cu6Sn5 and CoSn2 phases can be observed. The investigation on the local dendritic morphology after deep acid corrosion shows that these dendrites are composed of small sub-structures with faceted feature. Faceted growth of the primary Cu3Sn and CoSn phases is also confirmed, and a faceted to non-faceted transition in their morphologies is observed with increasing growth velocities. Further analysis shows that the dendritic morphology is formed in the solidified phases whose solubility range is larger during peritectic solidification.

Manipulating oxygenate adsorption on N-doped carbon by coupling with CoSn alloy for bifunctional oxygen electrocatalyst

Highly active bifunctional oxygen electrocatalysts accelerate the development of high-performance Zn-air battery, but suffer from the mismatched activities of oxygen evolution reaction (OER) and oxygen reduced reaction (ORR). Herein, highly integrated bifunctional oxygen electrocatalysts, cobalt-tin alloys coated by nitrogen doped carbon (CoSn@NC) are prepared by MOFs-derived method. In this hybrid catalyst, the binary CoSn nanoalloys mainly contribute to highly active OER process while the Co (or Sn)−N−C serves as ORR active sites. Rational interaction between CoSn and NC donates more rapid reaction kinetics than Pt/C (ORR) and IrO2 (OER). Such CoSn@NC holds a promise as air-cathode electrocatalyst in Zn-air battery, superior to Pt/C + IrO2 catalyst. First-principles calculations predict that CoSn alloys can upgrade charge redistribution on NC and promote the transfer to reactants, thus optimizing the adsorption strength of oxygen-containing intermediates to boost the overall reactivity. The tuning of oxygenate adsorption by interactions between alloy and heteroatom-doped carbon can guide the design of bifunctional oxygen electrocatalysts.

Tin-cobalt bimetals in 2D leaf-like MOF-derived carbon for advanced lithium storage applications

Tin-based (Sn) composite materials have exhibited a promising potential to substitute traditional graphite because of their appreciable specific capacity and improved safety. However, pure metallic Sn anode suffers from poor capacity retention in long-term cycling caused by large volumetric changes. Herein, a binary Sn-Co alloy was embedded in a carbon matrix derived from nitrogen-doped two-dimensional (2D) leaf-like metal-organic-framework (MOF) via a facile one-step approach. A uniform distribution of Sn-Co alloy particles was obtained. The generated 2D leaf-like carbon framework not only served as a conductive matrix to promote electronic conduction, but also acted as a buffer phase to relieve pulverization. As an electrode material, this composite showed a high specific capacity, favorable initial coulombic efficiency (ICE) of 65%, and superior rate performance even under high current density (10 C). In the long-term cycling test (700 cycles), it displayed an excellent reversible specific capacity of 604 mAh g−1 with no capacity reduction. These results demonstrated the expected advantages of the Sn-Co@C composite electrode for advanced lithium storage.

Solid/liquid interface evolution including seaweed morphology during directional solidification of Co-Sn alloys

The directional solidification of Co–Sn alloys at 300 K/cm was performed systematically with particular attention to the uncommon ‘seaweed’ morphology observed in this system. As withdrawal velocity increased, the quenched solid/liquid interface of Co-20 at.-% Sn hypoeutectic transformed from a planar of α-Co/-Co3Sn2 lamellar eutectic to dendritic α-Co + eutectic, and the planar interface of Co-24 at.-% Sn eutectic destabilised to cellular. As for Co-30 at.-% Sn hypereutectic, the planar interface transited to dendritic -Co3Sn2 + eutectic and then to seaweed -Co3Sn2 + eutectic. The increase of withdrawal velocity results in primary α-Co or -Co3Sn2 phase growing ahead of the coupled eutectic, and the leading distance is gradually increased with withdrawal velocity. The spacing of the two tips of -Co3Sn2 seaweed in the alloys followed a power law, , and the tip splitting frequency versus growth velocity as the function of .

The Evolution of Growth Morphology of Co3sn2 Phase in Undercooled Solidification of Co-Sn Alloy

The Evolution of Growth Morphology of Co3sn2 Phase in Undercooled Solidification of Co-Sn Alloy

CoSn Alloy-based three-dimensional ordered multistage porous composite towards effective polysulfide confinement and catalytic conversion in lithium‐sulfur batteries

Reasonable design of porous sulfur cathode can inhibit shuttle effect of lithium polysulfide (LiPS), accelerate redox kinetic and enhance the cycling stability, which is important to the development of lithium-sulfur (Li-S) battery. In this work, a multistage porous composite with three-dimensionally ordered macroporous (3DOM) CoSn alloy and embedded microporous Co decorated N-doped carbon (Co-NC) is rationally designed. The conductive CoSn alloy skeleton exhibits strong polar adsorption and effective catalytic activity towards polysulfide conversion, as well as fast electron transportation. Meanwhile, the 3DOM structure possesses sufficient volume space for ion migration and sulfur expansion. Additionally, the properly embedded Co-NC derived from ZIF-67 can offer abundant micropores and catalytic sites, promoting polysulfide trapping and LiPS conversion kinetics. Accordingly, the Li-S batteries fabricated with 3DOM Co-NC@CoSn exhibit remarkable stability with an ultralow capacity decay of 0.046% per cycle over 500 cycles at 1 C. An impressive areal capacity of about 5.1 mAh cm−2 under high sulfur loading of 6.8 mg cm−2 is also achieved at 0.2 C, with a high capacity retention of 79% over 100 cycles. The pouch cell maintains stable at 0.05 C, and the capacity decay is only 0.29% per cycle. This design and synthesis strategy of cathodes has great prospects in the practical application of Li-S battery.

Phase Control of Co-Sn Alloys through Direct Electro-Deoxidation of Co3O4/SnO2 in LiCl-KCl Molten Salt

Co can form a series of intermetallic compounds with Sn which usually exhibit unique physical and chemical properties. However, it is a challenge to control the phase composition of Co-Sn alloys. Here, we attempted to prepare Co3Sn2, CoSn and CoSn2 from the mixture of Co3O4/SnO2 using electro-deoxidation. We investigated the effects of sintering temperature for the mixed oxide plate and electrolysis conditions, such as voltage, electrolysis time, and molten salt temperature on the electro-deoxidation process of Co3O4/SnO2. The electrochemical deoxidation mechanisms of Co3O4, SnO2, and Co3O4/SnO2 composites were also explored by cyclic voltammetry using metallic cavity electrode. The Co-Sn alloys with different phase compositions, such as Co3Sn2, CoSn, and CoSn2, were obtained through controlling the molar ratio between Co and Sn in the initial Co3O4/SnO2 plate and the molten salt temperature. The obtained Co-Sn alloys were used as anode materials for lithium-ion batteries which showed 123.0, 246.5, and 323.4 mAh g−1 for Co3Sn2, CoSn, and CoSn2, respectively.

Electrospun of CoSn nanoboxes@carbon nanotubes as free-standing anodes for high-performance lithium-/potassium-ion batteries

Herein, we report a novel structure with hollow CoSn alloy nanoboxes encapsulated in N-doped carbon nanotubes (CoSn@N-C nanotubes) for Li-ion batteries (LIBs) and K-ion batteries (PIBs). The structure is synthesized by an electrospinning method and subsequent calcination process. The obtained hollow N-doped carbon nanotubes not only effectively ensure the stability of CoSn alloys, but also accelerate ionic/electronic transport rate. Besides, the inner inactive Co and the hollow structure of CoSn nanoboxes can buffer the volume expansion of CoSn alloys during cycling. Benefiting from the hierarchical nanostructure and synergistic effect of the components, the electrodes demonstrate a reversible capacity of 653 mAh g−1 after 450 cycles in LIBs at 0.2 A g−1. Notably in PIBs, the CoSn@N-C nanotubes exhibits high rate capabilities up to 10 A g−1 and remarkable cycling life (178 mAh g−1 after 2000 cycles at 0.5 A g−1).

Synthesis of a Co-Sn Alloy-Deposited PTFE Film for Enhanced Solar-Driven Water Evaporation via a Super-Absorbent Polymer-Based "Water Pump" Design.

Solar-driven water evaporation is a promising solution to water pollution, the energy crisis, and water shortages. However, the approach in which the photothermal film is in direct contact with bulk water for water evaporation may lead to a large amount of heat loss, thereby reducing the light-to-heat conversion efficiency (η) of the photothermal film. Here, a highly efficient solar-driven water evaporation system was developed using a Co-Sn alloy-deposited Teflon (PTFE) film (Co-Sn alloy@PTFE) and super-absorbent polymers (SAPs) supported with a floating foam substrate. The Co-Sn alloy with full-spectrum (200-2500 nm) absorption characteristics is devoted to high light-to-heat conversion, while the porous PTFE with high mechanical performance can support the Co-Sn alloy. We used density functional theory to prove that the Co-Sn alloy had a strong adhesive force with PTFE without surfactants due to the high adsorption energy between the (101) crystal plane of the Co-Sn alloy and the hydroxyl group on the PTFE film. Importantly, via the SAP-based "water pump" design, we improved the η of the Co-Sn alloy@PTFE film to 89%, mainly because the SAP not only effectively performed water transportation but also markedly reduced the heat loss of the Co-Sn alloy@PTFE film. Our work highlights the strong potential of Co-Sn alloy@PTFE-based light-to-heat conversion systems for realizing highly effective solar energy-driven water evaporation.

Core–Shell CoSn@CoSnOx Nanoparticles Encapsulated in Hollow Carbon Nanocubes as Anodes for Lithium‐Ion Batteries

Sn‐based materials are considered as a promising candidate for anodes of lithium‐ion batteries (LIBs). However, rapid capacity fading associated with large volume expansion during cycling impedes the commercialization of Sn‐based anodes. Herein, a yolk–shell structure is designed via a thermal reduction method and following in situ surface oxidation. In this configuration, CoSn nanoparticles covered by a conformal surface oxide layer are encapsulated in hollow carbon nanocubes. When utilized as an anode material for LIBs, the CoSn@CoSnO x @C exhibits a high discharge capacity of 1177 mAh g−1 after 180 cycles at 0.2 A g−1 and a capacity retention of 86.7% after 500 cycles at a higher current density of 1 A g−1. The investigation demonstrates that the outstanding electrochemical performance of the composite anodes can be attributed to the synergistic effects of the yolk–shell structure, nanosized CoSn alloy core, and conformal surface oxide layer. This elaborately designed structure can be extended to other alloy‐type anode materials to tackle the capacity decay induced by volume expansion.

Non-isothermal crystallization kinetics of an intermetallic CoSn phase

Herein, the crystallization kinetics of the intermetallic CoSn phase, nucleated and grown in the microstructure of a binary CoSn alloy, have been reported. Differential scanning calorimetry traces under non-isothermal conditions were obtained and used to extract the activation energy () for the crystallization of the CoSn phase at various heating rates. The obtained values of were validated by the application of several isoconversion methods. The minimum value of was 1000 kJ mol−1, which occurred at 853 K. The observed behavior of showed a strong temperature dependence, wherein it decreased with increasing temperature. This suggests that the rate constant for the crystallization of the CoSn phase is determined by the rates of two processes—nucleation and diffusion. The precise description of the crystallization process for the CoSn phase reveal that the reaction mechanism of this phase is following the first-order reaction.

Synthesis of monodisperse SnCo nanoparticles in triethylene glycol and its carbon composites for advanced lithium-ion batteries

The tin-based materials are one kind of the most promising high-capacity anode candidates for advanced Li-ion energy storage systems. However, they still face the problem of large volume expansion during charge–discharge processes, which causes rapid capacity decay and thus largely limit their serving life in practical application. In this work, ultra-fined SnCo alloy particles were successfully synthesized by a facile reduction of metal salts in triethylene glycol (TEG) solution, and then SnCo-anchored carbon composites were obtained through the calcination of SnCo-doped poly-(2-ethyl-2-oxazoline) (PEtOx) clusters. The microstructure, morphology, chemical composition and phase constitution are systematically analyzed. It is found that the as-prepared SnCo alloy particles exhibit a uniformly dispersed spherical morphology with a small average grain size of 20 nm and also a high reversible capacity of 459.1 mAh g[Formula: see text] after 100 cycles. More significantly, the SnCo/C nanocomposites present an excellent capacity retention ratio of 91.1% over 200 cycles at 100 mA g[Formula: see text] as well as good rate capability, suggesting that due to the accelerated electrons and Li[Formula: see text] transportation, the introduction of carbon matrix could significantly improve the stability of the active SnCo nanoparticles and inhibit the occurrence of their volume expansion during cycling.

Microstructural properties and peritectic reactions in a binary Co–Sn alloy by means of scanning electron microscopy and atom probe tomography

Recent studies of lithium-ion batteries suggest that the use of binary CoSn alloys as anodes should provide an improvement over currently used anode materials. However, the implementation of CoSn alloys is challenging due to uncertainties regarding the phase transformations within this system. In order to understand these, we evaluate the compositions of different intermetallic compounds produced via the peritectic reactions, nucleate and grow within the microstructure of binary Sn − 25 at.% Co by employing atom probe tomography (APT). The stoichiometric phase, which is produced upon the cooling of the melt, is not only found as part of the peritectic solidification sequence but also as clusters within the pure Sn phase. The phase was found as a nano sized layer and is attributed to the peritectic reaction between the phase and the pure Sn phase. The production of the compound was enhanced by the phase transformation of the phase. Furthermore, clusters had formed in the pure Sn phase. A limited solubility within the pure Sn phase was also determined to be (0.6 ± 0.1) at.% Co.

Cyanometallic framework-derived dual-buffer structure of Sn-Co based nanocomposites for high-performance lithium storage

Tin (Sn)-based anodic materials have attracted tremendous attention in lithium-ion batteries (LIBs) owing to their high theoretical capacity and low potential (0.5 V versus Li/Li+). However, Sn-based anodic materials usually suffer from serious structural collapse and large volume expansion. To overcome this obstacle, herein, a dual-buffer structure of tin-cobalt (Sn-Co) alloy-based nanocomposite was designed through thermal annealing of a cyanometallic framework. The inactive Co acts as robust framework to buffer the volume expansion of Sn-Co alloy nanoparticles, and the reduced graphene oxide (rGO) matrix can reduce the aggregation of Sn-Co nanoparticles as well as alleviate the structure collapse of electrode during long-term cycling. As LIBs anodes, the Sn-Co/rGO composites exhibit a high reversible capacity (1055 mAh g−1 at 0.2 A g−1 after 250 cycles), good rate capability (320 mAh g−1 at 5 A g−1), and outstanding long-term cycling performance (720 mAh g−1 at 1 A g−1 after 600 cycles). When coupled with LiFePO4, the full battery can also display high electrochemical performance in terms of discharge capacity and cyclic stability.

In Situ Construction of Multibuffer Structure 3D CoSn@SnOx/CoOx@C Anode Material for Ultralong Life Lithium Storage

Rapid progress of lithium‐ion batteries (LIBs) highly relies on high‐performance electrode materials. Herein, a novel nanocomposite of CoSn alloy with a multishell layer structure confined in 3D porous carbon is constructed through a facile freeze drying and annealing treatment method. The skillful design effectively relieves the volume expansion of the Sn‐based alloy and enhances the combination between CoSn and carbon. Profiting from the synergistic effect of the multibuffer structure alloy and cross‐linked porous carbon, CoSn@SnOx/CoOx@C displays high capacity (912.6 mA h g−1 after 100 cycles at 0.1 A g−1) and excellent cycling stability (almost no capacity decay at 10 A g−1 after 1000 cycles) when used as anode for LIBs. The presence of Sn–O/Co–O bond makes the nanoalloy tightly pinned on the carbon substance and the structure stability of electrode material is improved significantly. Furthermore, the porous carbon with plentiful defects offers abundant room for the volume expansion of Sn and ensures fast transport of electrons/ions. Cyclic voltammogram (CV) curves under different scan rates reveal that the charge storage of the nanocomposite is controlled by pseudocapacitive and ion‐diffusion mechanisms. This facile fabrication strategy and unique structure design can be extended to other composite materials for energy storage devices.

Research of Co-Sn alloy as Anode material for lithium ion battery

The CoSnx alloys with different atom ratio (x=2, 4, 8) were prepared by solid phase reduction reaction through mechanical ball milling. The structure and morphology were represented by X - ray diffraction (XRD) and scanning electron microscopy (SEM). the elctrochemical performance of the alloy as anode material of li-ion battery was investigated by assembling the analog battery.The experimental results reveal that the nanostructured amorphous CoSn4 shows a relatively high initial discharge capacity (430 mAh/g) and good cycling performance, as its capacity still maintain at 360 mAh/g after the 15th cycle, with a capacity retention ratio of 84 %.

Preparation of coaxial Sn-Co alloy/CNFs 3D freestanding membrane anode by electrochemical Co-deposition for lithium-ion batteries

Coaxial Sn-Co alloy/CNFs nanocomposite three-dimensional (3D) membrane is synthesized via a facile electrochemical co-deposition method using the CNFs membrane with 3D network structure as the flexible freestanding substrate. The as-synthesized nanocomposite membrane is characterized using scanning electron microscopy (SEM), transition electron microscopy (TEM), energy dispersive spectrometer (EDS), and X-ray diffraction (XRD). The results reveal that nanoscaled Sn-Co alloy layer is uniformly covered onto the surface of CNFs; the thickness of Sn-Co alloy shell layer can be controlled to about 60–110 nm. EDS result exhibits that the atomic percentage of Sn, Co, and C in the as-synthesized nanocomposite membrane is 53.25 at%, 20.19 at%, and 26.56 at%, respectively. The nanocomposite membrane with the unique 3D network structure is flexible after Sn-Co alloy deposition. Its electrochemical performances are investigated by the cyclic voltammetry, galvanostatic charge/discharge cycling, and rate cycles. Its discharge specific capacity for 2nd and 50th cycle is 1260 mAh g−1 and 788 mAh g−1, respectively, and the capacity attenuation ratio is about 0.75%/cycle at a current density of 50 mA g−1. The excellent electrochemical performance of the coaxial Sn-Co alloy/CNFs nanocomposite 3D membrane is mainly contributed to the high mechanical strength, good flexibility, and high electrical conductivity of CNFs substrate, which offers a possible solution of Sn volume change and poor electronic conduction during charge/discharge process.

Interaction of Components of Co-Sn and Co-Sn-Cu Powder Materials in Liquid Phase Sintering

The interaction of components and structure formation were studied in liquid phase sintering of Co-Sn and Co-Sn-Cu powder materials. The powders of commercially pure metals were mixed with an organic binder and applied on the steel substrate. Sintering was performed under vacuum at temperatures of 820 and 1100 °C. The structure of sintered alloys was investigated by X-ray diffractometry and electron probe microanalysis, and microhardness (HV0.01) of the structural components was measured. It has been found that the nature of interaction of the liquid tin with the solid phase at the initial stage of sintering affects the formation of structure and porosity of Co-Sn and Co-Sn-Cu alloys considerably. In Co-Sn alloys, diffusion of tin into cobalt particles leads to the formation of intermetallic compounds, which hinders spreading of the liquid phase. This results in a porous defect structure formed in Co-Sn alloys. In Co-Sn-Cu alloys, at the initial stage of sintering the liquid phase enriched with copper is formed that wets the cobalt particles and contributes to their regrouping. As a result of this, materials with minor porosity are formed.

An all-in-one Sn-Co alloy as a binder-free anode for high-capacity batteries and its dynamic lithiation in situ.

A three-dimensional all-in-one Sn-Co alloy anode is reported for the first time, which delivers a high capacity along with a stable coulombic efficiency as well as good temperature tolerance. The binder-free electrode eliminates the complexity of conventional slurry preparation while maintaining an integrated scaffold, which provides space to accommodate volume expansion, as confirmed by an in situ transmission electron microscopy study.