Top-Down Fabrication of α-Fe₂O₃ Single-Crystal Nanodiscs and Microparticles with Tunable Porosity for Largely Improved Lithium Storage Properties

Abstract

In this work, we report a facile top-down approach to fabricate uniform single-crystal α-Fe(2)O(3) nanodiscs via selective oxalic acid etching. Phosphate ions are employed as a capping agent to control the etching to along the [001] direction. We also show that α-Fe(2)O(3) melon-like microparticles with contrasting textural properties can be generated using the same approach. The etched particles exhibit a much larger total pore volume and average pore size compared to the pristine ones, thus serving as the possible origin for their greatly enhanced capacity retention when tested as potential anode materials for lithium-ion batteries.

Evaluating the performance of nanostructured materials as lithium-ion battery electrodes

“…The addition of carbon was suggested to offer structural support by means of a buffering effect while the improved electrical conductivity of the C/Fe2O3 nanotubes enabled the enhanced rate performance (up to 12C) that was reported [170]. Similar performance has been demonstrated with porous α-Fe2O3 nanodiscs prepared by oxalic acid etching of single crystal Fe2O3 nanocrystals [168]. Preferential etching in the <001> direction was carried out using phosphate (H2PO4 -) as a biased capping agent.…”

“…Although early work on Fe2O3 anodes resulted in high initial capacities, much of the capacity was lost with extended cycling. More recently, advanced Fe2O3 structures such as nanoflakes [166], nanocapsules [167], nanodiscs [168], hollow nanoparticles [169], nanotubes [170], and reduced-graphene/Fe2O3 nanocomposites [171] have emerged with enhanced Li-ion performance. Liu et al [170], prepared 1D α-Fe2O3 and C-Fe2O3 nanotubes grown directly on conducting substrates by a so-called "sacrificial template-accelerated hydrolysis" (STAH) method, using arrays of ZnO nanowires as hard templates.…”

Facet‐Controlled Synthetic Strategy of Cu2O‐Based Crystals for Catalysis and Sensing

“…Recently, much effort is dedicated to a so‐called “top‐down” engineering approach that delicately modifies crystals to create more highly active sites by etching and crystal cut, for the purpose of improvement the physical and functional properties of crystals 43, 46, 51, 68, 149, 150, 151, 152, 153, 154. (In this section, the “top‐down” means crystal carving without phase transformation; while the “top‐down” in the next section refers to total phase transformation from Cu 2 O to various hollow structures.)…”

“…For instance, by employing hydrofluoric acid as a capping agent (CA), H. G. Yang et al34 were the first to obtain uniform anatase TiO 2 single crystals with a high percentage (47%) of highly reactive {001} facets, which possessed promising applications in sensors, solar cells and photocatalysis. Besides the various routes for the synthesis of NCs, several novel strategies have recently exploded by carving, modifying, or transforming the original NCs that greatly improve the catalysis and sensing performances 6, 27, 30, 33, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52. For example, X. Chen et al51 disordered the surface layers of nanophase TiO 2 by hydrogenation.…”

Hydrothermal synthesis of cubic α-Fe2O3 microparticles using glycine: Surface characterization, reaction mechanism and electrochemical activity

“…Synthesis of ␣-Fe 2 O 3 microand nanoparticles has been widespread due to their high stability and excellent semiconducting properties [1,2]. Previously synthesized ␣-Fe 2 O 3 micro/nanoparticles include single-crystal dendritic micro-pines [3], nanotubes [4], nanorings [5], rod-like nanocrystals [6], micro-nano-octahedrons [7], star-like nanoparticles [8], microspheres [9,10], nanodiscs [11]) and plate-like particles [12] for magnetic [3,8,12], gas sensor [4,5], battery [4,9,11] and catalytic [7] applications.…”