Controlled synthesis of core-shell Fe2O3@N-C with ultralong cycle life for lithium-ion batteries

In Situ Phase Transformation of Nanoporous Fe2O3 Dendrite to Fe2O3/FeS2 Polycrystalline Texture Achieving Superior Rate Capability and Ultra-Long Cycling Stability with High Capacity

Structural design combined with crystal engineering is an external and internal modifying strategy for metal oxides and sulfides as anode materials for lithium/sodium-ion batteries (LIBs/SIBs). In this paper, the low-cost iron-based oxide of Fe2O3 shaped into dendritic nanostructure is locally in situ phase converted to FeS2 and form porous Fe2O3/FeS2 polycrystalline texture. The Fe2O3/FeS2 maintains the original porous, cross-linked and low-dimension structural advantages of the Fe2O3 precursor for electron transport and ions exchange and alleviating volume expansion. Then, the abundant heterogeneous in the converted Fe2O3/FeS2 dramatically enhances electron diffusion in crystal and the structural stability at phase boundary. The prepared anode achieves superior rate capability and ultra-long cycling stability with high capacity both in LIBs and SIBs. Specially, it shows 1017 and 1016 mAh g-1 at 10 A g-1 in LIBs and SIBs, separately. After 3000 cycles, the electrodes maintain 266 mAh g-1 at 10 A g-1 in LIBs and 279 mAh g-1 in SIBs. In addition, the LiFePO4//Fe2O3/FeS2 and (Na3V2(PO4)3)//Fe2O3/FeS2 full cells are successfully packaged and also show satisfactory electrochemical performances.

ZIF-8-derived hybrid nanocomposite platform with magnetic hematite nanoparticles as enhanced anode materials for lithium storage

Herein, α-Fe2O3-ZnO/C (FZC) nanocomposite samples were synthesized via a chemical co-precipitation method, followed by a one-step heat-treatment at different temperatures to serve as anode materials. The advantages of FZC include a high specific surface area, a porous structure that facilitates rapid ion/electron transport, and additional active sites for lithium ions, leading to excellent electrical conductivity and superior electrochemical performance. The FZC4 material demonstrated a high charge/discharge capacity of 561.2/587.8 mA h g-1 after 80 cycles at a current density of 0.1 A g-1, with low impedance and a coulombic efficiency (CE) of 95.4%. The outstanding electrochemical performance of the FZC nanocomposites can be attributed to the synergistic effect between the hematite (α-Fe2O3) nanoparticles and ZIF-8-derived platform framework, which significantly enhanced the lithium storage capacity of the anode. Our work provides an additional contribution to the field of nanomaterial research, expanding the potential for developing efficient and sustainable energy storage solutions in the future.

Designing 3D SnS@Cu-Ni Nanoporous Column Array Electrode for High-Capacity and High-Rate Lithium-Ion Batteries

Sn-based materials with high capacity showcase great potential for next-generation lithium-ion batteries (LIBs). Yet, the large volume change and limited ion/electron transfer efficiency of Sn-based materials upon operation significantly compromises the battery performance. In this study, a unique 3D copper-nickel nanoporous column array current collector is rationally developed via a facile template-free galvanostatic electrodeposition method, followed by electrodepositing SnS active material onto it (denoted as 3D SnS@CNCA). Excitingly, the morphology of the 3D SnS@CNCA electrode perfectly inherited the nanoporous column array structure of the 3D current collector, which not only endows the electrode with a large specific surface area to provide more active sites and sufficient ion/electron transport pathways, but also effectively alleviates the volume expansion of SnS upon repeated charge-discharge cycles. Therefore, the binder-free 3D SnS@CNCA electrode showcases a significantly enhanced Li storage performance, showing a high initial reversible capacity of 1019.7 mAh g-1 with noteworthy cycling stability (a capacity retention rate of 89.4% after 200 cycles). Moreover, the designed electrode also manifests high rate performance with a high capacity of 570.6 mAh g-1 at 4 A g-1. This work provides a novel design idea for the preparation of high-performance electrodes beyond LIBs.

Synthesis and characterization of micro-/nano-α-Fe2O3 for photocatalytic dye degradation

Photocatalytic activity using micro-/nano-α-Fe2O3 on a large scale was carried out using a sol-gel autocombustion method. A degradation time of 60 min was noted for 50 mg of the catalyst. Post characterization, this catalyst system showed a degradation of about 53% (rate = 2.60 × 10-3 min-1) and 17% (rate = 1.38 × 10-2 min-1) under sunlight and up to 45% (rate = 1.13 × 10-3 min-1) and 7% (rate = 1.20 × 10-2 min-1) under a 400 W UV lamp for rhodamine 6G (R6G) and crystal violet (CV), respectively. Sunlight has a broad spectrum of light; it greatly accelerates the degradation process and creates ideal conditions for the reaction to occur. The rate of photocatalytic dye degradation of α-Fe2O3 without Fenton's reagent was found to be 7.84 × 10-3 min-1 in the presence of external air provided (in the photocatalytic setup) through a bubbler and 3.23 × 10-3 min-1 in the absence of the bubbler.

Fabrication, characterization, and application of BiOI@ZIF-8 nanocomposite for enhanced photocatalytic degradation of acetaminophen from aqueous solutions under UV-vis irradiation

This work investigates the use of novel BiOI@ZIF-8 nanocomposite for the removal of acetaminophen (Ace) from synthetic wastewater. The samples were analyzed using FTIR, XRD, XPS, DRS, PL, FESEM-EDS, and ESR techniques. The effects of the loading capacity of ZIF-8 on the photocatalytic oxidation performance of bismuth oxyiodide (BiOI) were studied. The photocatalytic degradation of Ace was maximized by optimizing pH, reaction time and the amount of photocatalyst. On this basis, the removal mechanisms of the target pollutant by the nanocomposite and its photodegradation pathways were elucidated. Under optimized conditions of 1 g/L of composite, pH 6.8, and 4 h of reaction time, it was found that the BiOI@ZIF-8 (w/w = 1:0.01) nanocomposite exhibited the highest Ace removal (94%), as compared to that of other loading ratios at the same Ace concentration of 25 mg/L. Although this result was encouraging, the treated wastewater still did not satisfy the required statutory of 0.2 mg/L. It is suggested that the further biological processes need to be adopted to complement Ace removal in the samples. To sustain its economic viability for wastewater treatment, the spent composite still could be reused for consecutive five cycles with 82% of regeneration efficiency. Overall, this series of work shows that the nanocomposite was a promising photocatalyst for Ace removal from wastewater samples.

Fe2O3 for stable K-ion storage: mechanism insight into dimensional construction from stress distribution and micro-tomography

Fe2O3 is considered a potential electrode material owing to its high theoretical capacity, low cost, and non-toxic characteristics. However, the significant volume expansion and structural degradation during charging and discharging hinder its application in potassium ion batteries. The electrochemical properties of the electrode material are primarily influenced by the diffusion efficiency of ions and the mechanics of the object. From the construction of a one dimensional structure, a three-dimensional flower-like Fe2O3 with a high specific surface and low-dimensional spherical Fe2O3 were prepared. Considering the convenience and visualization of the research, micron-scale Fe2O3 was prepared, although the larger particle size will lose part of the capacity. Notably, compared with the spherical structure, the specific capacity of the flower structure was increased by about 100%. The von Mises stress distribution on the two structures was simulated by the finite element method, revealing the mechanism of electrode failure induced by volume expansion and confirming the vital role of the multidimensional system in relieving stress concentration and improving electrochemical performance. Furthermore, synchrotron radiation soft X-ray absorption spectrum and X-ray micro-tomography revealed the phase transformation process and reaction mechanism of Fe2O3 in potassium ion batteries. The dimensional structure construction strategy reported here can provide theoretical support for modifying transition metal oxides.