Hollow Metal Oxide Nanoparticles Research Articles

Camphene-derived hollow and porous nanofibers decorated with hollow NiO nanospheres and graphitic carbon as anodes for efficient lithium-ion storage

A synthesis strategy for hollow and porous nanofibers comprising hollow NiO (H-NiO) nanospheres formed via nanoscale Kirkendall diffusion and supported over a porous graphitic carbon matrix (H-NiO@HNFs) is reported herein to enable the fabrication of advanced anodes for stable lithium-ion batteries (LIBs). The H-NiO@HNFs comprising 1D longitudinal hollow channels ensured efficient diffusion of charged species via effective electrolyte percolation besides providing sufficient space to accommodate the large volume variations during repeated cycling. The hollow NiO nanospheres acted as chemical sites for lithiation and delithiation. Additionally, the H-NiO@HNFs exhibited improved lithium-ion storage properties, such as reasonable rate capability, stable prolonged cyclability at a high current density (1.0 A g-1), and a high lithium-ion diffusion coefficient, primarily owing to their enhanced structural integrity compared to that of filled NiO nanofibers (F-NiO NFs). This facile synthesis approach could broaden the current understanding of 1D hollow nanostructures decorated with conventional hollow metal-oxide nanoparticles for various applications.

Rational Fabrication and Improved Lithium Ion Battery Performances of Carbon Nanofibers Incorporated with α-Fe2O3 Hollow Nanoballs

The present results contribute a facile route to prepare carbon nanofibers hybrided with hollow metal oxide nanoparticles under the assistance of Kirkendall effect. α‒Fe2O3 hollow nanoball incorporated carbon nanofibers (denoted as FOCNFs) are rationally fabricated by using electrospun composite carbon nanofibers (CNFs) as the precursors. The hollow nanoparticles are 69.8 nm in the average size with the shell thickness of 14 nm. The composite nanofibers are hierarchically porous. The mesopores are in the range of 2 ‒ 10 nm and center at 3.7 nm. The micropores center at 0.5 nm with the micropore volume of 0.02 cm3·g−1. Time dependant morphology evolutions confirm that the formation of α‒Fe2O3 hollow nanoballs is promoted by the nanoscale Kirkendall effect due to the migration difference between oxygen molecules and Fe3+ cations in the solid. This route is also successfully extended to fabricate hollow Co3O4 and NiO nanoparticles incorporated carbon nanofibers. FOCNFs exhibit improved lithium ion battery performances with enhanced capacity, rate capability and long-term cycling stability. The optimized sample of FOCNFs‒30 delivers a high initial capacitance of 1903.8 mAh·g-1 at 100 mA·g-1. A reversible capacity of 601.2 mAh·g-1 sustains at 0.1 C after 300 charge-discharge cycles. The improved electrochemical performances of FOCNFs stem from coupling the characteristics of α-Fe2O3 nanoballs and porous nanofibrous carbon matrix.

Uniform, Scalable, High-Temperature Microwave Shock for Nanoparticle Synthesis through Defect Engineering

Summary Here we demonstrate a thermal shock synthesis method triggered by microwave irradiation for the rapid synthesis of nanoparticles on reduced graphene oxide (RGO) substrate. With properly controlled reduction, RGO has high electrical conductivity while maintaining functional groups, leading to an extremely efficient microwave absorption of ∼70%. The high utilization of microwaves results in the ability to raise the temperature to 1,600 K in just 100 ms, which is followed by rapid quenching to room temperature. The defects on the RGO are crucial for achieving this record-high microwave-induced temperature as these defects play a fundamental role in absorbing the radiation as well as the self-quenching mechanism. By loading precursors onto RGO, we can utilize rapid temperature change to synthesize nanoparticles. The nanoparticles are ∼10 nm with uniform distribution. This facile, rapid, and universal synthesis technique has the potential to be employed in large-scale production of nanomaterials and suggests a new direction for nanosynthesis.

A Universal Strategy for Hollow Metal Oxide Nanoparticles Encapsulated into B/N Co-Doped Graphitic Nanotubes as High-Performance Lithium-Ion Battery Anodes.

Yolk-shell nanostructures have received great attention for boosting the performance of lithium-ion batteries because of their obvious advantages in solving the problems associated with large volume change, low conductivity, and short diffusion path for Li+ ion transport. A universal strategy for making hollow transition metal oxide (TMO) nanoparticles (NPs) encapsulated into B, N co-doped graphitic nanotubes (TMO@BNG (TMO = CoO, Ni2 O3 , Mn3 O4 ) through combining pyrolysis with an oxidation method is reported herein. The as-made TMO@BNG exhibits the TMO-dependent lithium-ion storage ability, in which CoO@BNG nanotubes exhibit highest lithium-ion storage capacity of 1554 mA h g-1 at the current density of 96 mA g-1 , good rate ability (410 mA h g-1 at 1.75 A g-1 ), and high stability (almost 96% storage capacity retention after 480 cycles). The present work highlights the importance of introducing hollow TMO NPs with thin wall into BNG with large surface area for boosting LIBs in the terms of storage capacity, rate capability, and cycling stability.

General and facile synthesis of hollow metal oxide nanoparticles coupled with graphene nanomesh architectures for highly efficient lithium storage

Novel hollow-on-mesh hybrid architectures composed of hollow transition metal oxides and graphene nanomeshes hold great promise as advanced free-standing anodes for highly efficient lithium storage.

Pliable Embedded-Type Paper Electrode of Hollow Metal Oxide@Porous Graphene with Abnormal but Superior Rate Capability for Lithium-Ion Storage

To improve the electrochemical performance of pliable graphene/metal oxide composite papers, a new kind of embedded-type MO@PG paper electrode including Fe2O3@PG and CuO@PG was designed and prepared by simple filtration and controllable oxidation. MO@PG paper electrodes have special structures in which hollow metal–oxide nanoparticles are embedded in the pores of porous graphene films and connected with the edges of the graphene to produce a strong interfacial interaction. Benefiting from this unique structure, the MO@PG paper electrodes for LIBs exhibit higher specific capacities and better cyclic stability and rate performance. In particular, the MO@PG electrodes show an interestingly abnormal rate performance in that the specific capacity increases with the current density from 50 to 500 mA g–1, which should be attributed to Li-ion storage in graphene films being mainly controlled by diffusion, while electrochemical reactions of Fe2O3 are mainly controlled by Faradaic capacitance. At a higher current d...

Harnessing Thermal Expansion Mismatch to Form Hollow Nanoparticles

Nano popcorn: a new formation mechanism for the synthesis of hollow metal oxide nanoparticles through a melt fracture mechanism. The hollow nanoparticles are formed via brittle fracture following the generation of tensile stresses arising due to liquid-phase thermal expansion of a low melting point core metal. The progress of this physical process can be monitored using in situ transmission electron microscopy for a model system of indium/indium oxide.

Diffusion in Intermetallic Compounds and Fabrication of Hollow Nanoparticles through Kirkendall Effect

. In intermetallic compounds, random vacancy motion is not possible as it would disrupt the equilibrium ordered arrangement of atoms on lattice sites. In view of this limitation, various atomistic models have been proposed, which allow atom-vacancy exchanges to take place without concomitant long range disordering. For a L12 -type A3B structure, the major element A diffuses faster than the minor element B. The trend is attributed to the different diffusing paths; A atoms can diffuse through site exchanges with a neighbouring vacancy on its own sublattice, while the jump of a B atom to a neighbouring site always creates wrong bonds. For L10-type structures such as γ-TiAl, significant diffusion anisotropy is observed; Ti atoms diffuse on the Ti sublattice, while Al atoms also diffuse on the Ti sublattice. The formation of hollow metal oxide nanoparticles through the oxidation process has been studied by transmission electron microscopy for Cu, Zn, Al, Pb and Ni. The hollow structure is obtained as a result of vacancy aggregation, resulting from the rapid outward diffusion of metal ions through the oxide layer during the oxidation process. This suggests the occurrence of two different diffusion processes in the formation of hollow oxides.

Formation of a Nano-Hole via Oxidation of Metal Nanoparticles

The formation of hollow metal oxide nanoparticles through oxidation process has been studied by transmission electron microscopy for Cu, Zn, Al, Pb and Ni in order to clarify the detailed formation mechanism of hollow oxide nanoparticles and their governing factors. For Cu, Zn, Al and Ni nanoparticles, hollow oxide nanoparticles are obtained as a result of vacancy aggregation in the oxidation processes. These results arise from faster outward diffusion of metal ions through the oxide layer in the oxidation processes. On the other hand, Pb nanoparticles turn to solid PbO, because the diffusivity difference DPb < DO in PbO leads to no formation of vacancy clusters.

Hollow oxide formation by oxidation of Al and Cu nanoparticles

The formation of hollow metal oxide nanoparticles through the oxidation process at low temperatures from 295 to 423 K has been studied by transmission electron microscopy for Cu, Al, and Pb. For Cu and Al, hollow oxide nanoparticles are obtained as a result of vacancy aggregation in the oxidation processes, resulting from the rapid outward diffusion of metal ions through the oxide layer during the oxidation process. On the other hand, Pb nanoparticles turn to solid PbO because the diffusivity difference DPb<DO in PbO does not lend itself to the formation of vacancy clusters. The oxide growth behavior of Cu and Al nanoparticles of a larger size at 423 K are summarized as follows: (i) for Al, the rapidly forming oxide layer on its surface stops growing once it reaches a critical thickness of about 1.5 nm, (ii) the growth of Cu2O continues until hollow Cu2O of a certain thickness is formed. This suggests the occurrence of two different diffusion processes in the formation of hollow oxides: the rapid outward diffusion of metal ions based on the Cabrera–Mott theory plays an important role in the formation of hollow Al-oxides, whereas the Kirkendall effect at the Cu∕Cu2O interface, where Cu diffuses much faster than oxygen, brings about the formation of hollow Cu2O.