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GeO <sub/>2</sub> Encapsulated Ge Nanostructure with Enhanced Lithium-Storage Properties
摘要： Germanium (Ge)-based nanostructures, especially those with germanium dioxide (GeO2), have drawn great interest for applications in lithium (Li)-ion batteries due to their ultrahigh theoretical Li+ storage capability (8.4 Li/Ge). However, GeO2 in conventional Ge(s)/GeO2(c) (where (c) means the core and (s) means the shell) composite anodes with Ge shell outside GeO2 undergoes an irreversible conversion reaction, which restricts the maximum capacity of such batteries to 1126 mAhg?1 (the equivalent of storing 4.4 Li+). In this work, a porous GeO2(s)/Ge(c) nanostructure with GeO2 shell outside Ge cores are successfully fabricated utilizing the Kirkendall effect and used as a lithium-ion battery anode, giving a substantially improved capacity of 1333.5 mAhg?1 at a current density of 0.1 Ag?1 after 30 cycles and a stable long-time cycle performance after 100 cycles at a current density of 0.5 A g?1. The enhanced battery performance is attributed to the improved reversibility of GeO2 lithiation/delithiation processes catalyzed by Ge in the properly structured porous GeO2(s)/Ge(c) nanostructure.
关键词： porous,Kirkendall effect,nanostructures,lithium ion batteries,GeO2(s)/Ge(c)
更新于2025-09-23 15:22:29
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Engineering of hollow AlAu2 nanoparticles on sapphire by solid state dewetting and oxidation of Al
摘要： The Al-Au binary diffusion couple is a classic example of the system exhibiting Kirkendall voiding during interdiffusion. We demonstrate that this effect, which is a major reason for failures of the wire bonds in microelectronics, can be utilized for producing hollow AlAu2 nanoparticles attached to sapphire substrate. To this end, we produced the core-shell Al-Au nanoparticles by performing a solid state dewetting treatment of Al thin film deposited on sapphire substrate, followed by the deposition of thin Au layer on the top of dewetted sample. Annealing of the core-shell nanoparticles in air resulted in outdiffusion of Al from the particles, formation of pores, and growth of the AlAu2 intermetallic phase in the particles. We demonstrated that the driving force for hollowing is the oxidation reaction of the Al atoms at the Au-sapphire interface, leading to the homoepitaxial growth of newly formed alumina at the interface. We developed a kinetic model of hollowing controlled by diffusion of oxygen through the Au thin film, and estimated the solubility of oxygen in solid Au. Our work demonstrates that the core-shell nanoparticles attached to the substrate can be hollowed by the Kirkendall effect in the thin film spatially separated from the particles.
关键词： Diffusion,Nanovoid,Solid state reaction,Kirkendall effect,Nanoparticles
更新于2025-09-23 15:22:29
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Surface passivation enabled-structural engineering of I-III-VI <sub/>2</sub> nanocrystal photocatalysts
摘要： Cation exchange has evolved into a powerful tactic for synthesis of semiconductor nanocrystals (NCs) that are not readily accessible otherwise. Here we have investigated the In3+-for-Cu+ cation exchange in the dodecahedral-shaped Cu7S4 NCs and found that surface passivation, either caused by excess guest cations or ligand molecules, can be exploited to engineer the structural properties of the NCs. By monitoring the parallel reactions carried out under systematically varied conditions, together with the positron annihilation spectroscopy investigation, we have demonstrated that the key element accounting for the observed surface passivation is associated with the copper vacant sites on the surface of Cu7S4 NCs. The reduction in In3+/Cu+ ratio and the presence of strong-binding ligands could enhance the density of surface copper vacancies and boost cation exchange reaction, which therefore alters the competition between the in-di?usion of In3+ and out-di?usion of Cu+ ions. Such capability to control the inter-di?usion balance in cation exchange (and the accompanying Kirkendall e?ect) enables the creation of a series of CuInS2 (and Cu7S4@CuInS2) NCs with various exotic structures, which show di?erent photocatalytic abilities in singlet oxygen generation. This study can not only add more structural complexity and diversity to the semiconductor NCs achievable by cation exchange, but also presents an important guideline for establishing a unifying mechanistic understanding of the reaction kinetics in cation exchange process.
关键词： cation exchange,Kirkendall effect,semiconductor nanocrystals,photocatalysis,surface passivation
更新于2025-09-23 15:21:01
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Hollow/porous-walled SnO2 via nanoscale Kirkendall diffusion with irregular particles
摘要： Hollow/porous structured SnO2 nanoparticles were synthesized by simple oxidation of dense metal chalcogenide precursors via nanoscale Kirkendall diffusion effect. First, tin chalcogenide (SnS, SnSe) nanoparticles were synthesized by mechanochemical method, which is considered a facile, scalable, and eco-friendly process. Hollow/porous-walled SnO2 nanoparticles were synthesized by simple oxidation of the prepared Sn chalcogenide precursors, for which the transformation mechanism was verified in detail. Nanoscale Kirkendall diffusion process was thoroughly investigated by morphological, crystallographic, and elemental analyses performed at various oxidation temperatures and times. To examine the morphological effect of hollow/porous-walled SnO2 nanoparticles on the electrochemical performance, the synthesized nanoparticles were applied as anode material in a lithium-ion battery. Anode material showed highly improved electrochemical properties compared to its dense counterpart, with 83% capacity retention from the second cycle at the 400th cycle and capacity of 302 mA h g-1 at a high current density of 30 A g-1.
关键词： chalcogenide,hollow structure,mechanochemical synthesis,porous particles,Kirkendall effect
更新于2025-09-16 10:30:52
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In-Situ Observation of Electrochemically Driven Kirkendall Effect Induced Volume Shrinkage of CuO Nanowires During Potassiation
摘要： Lithiation, sodiation, and potassiation usually induce volume expansion to the host structure due to the insertion of alkali metal ions into the host structure. Here we report an unusual volume shrinkage phenomenon during the potassiation of CuO nanowires. The volume shrinkage is caused by an “oxygen pump” and an electrochemically driven Kirkendall effect, in which the O2- ions in the CuO lattice and the K+ migrate asymmetrically under external electric field due to their different mass-to-charge ratio. This is the first direct observation on the “oxygen pump” and electrochemical Kirkendall effect induced volume shrinkage phenomenon, which reveals peculiar ion transport characteristic during electrochemical reactions.
关键词： Electron microscopy,In-situ,Potassiation,Microstructure,Volume shrinkage,Electrochemical Kirkendall effect
更新于2025-09-11 14:15:04
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Nanoscale Kirkendall effect driven Au Decorated CdS/CdO Colloidal Nanocomposites for Efficient Hydrogen Evolution, Photocatalytic Dye Degradation and Cr (VI) Reduction
摘要： The design of a facile and scalable method to synthesize solar light driven photocatalyst to generate H2 from water and degradation of toxic dyes from waste water is highly challenging field of research. Here, we are reporting a one pot synthesis of CdS/CdO colloidal nanocomposite with variable amount of CdS thickness and finally CdS nanoring. Different outward diffusion rate of oxygen and inward diffusion rate of sulphur ions generates hollow CdS/CdO nanocomposite based on nanoscale Kirkendall effect. Au nanoparticles (NPs) have been selectively deposited over CdS. Proper band alignment among CdO, CdS and Au results in a Z-type photocatalyst. Efficient spatial charge separation and large surface area lead to high photocatalytic dye degradation and Cr (VI) reduction in water. The amount of Cd in purified water is lesser than 0.003 ppm which maintains world Health Organization (WHO) guideline. The as developed catalyst is also active for generation of H2 from water in presence of solar light irradiation. Our present work may provide a promising way to fabricate an efficient photocatalyst for dye degradation and solar to fuel energy conversion using semiconductor (CdO)-semiconductor (CdS)-metal (Au) nanocomposite.
关键词： Dye Degradation,Hollow Nanocomposite,Kirkendall Effect,Z-scheme,H2 Production,Cr (VI) Reduction
更新于2025-09-10 09:29:36