Three‐dimensional mesostructured single crystalline Fe ₃ O ₄ for ultrafast electrochemical capacitor electrode with AC line filtering performance

Abstract

Epitaxial growth of three-dimensional (3D) architectures has led to new opportunities in the optoelectronic devices and nanoscale thermal engineering. The feature that makes these materials distinct is to form a complex geometry while preserving crystal epitaxy. This enables to exploit functionalities given by 3D interconnected pores and suppress charge trapping at defects. One technology that finds it useful is electrochemical energy storage in response to ultrafast alternate current (AC) switch. Here, we extend the concept of 3D mesostructured single crystals to electrochemical capacitors (ECs) for AC line filtering. We present bottom-up epitaxial infilling of Fe 3 O 4 into the selfassembled 300 nm diameter colloid templates using electrodeposition. The resulting 3D mesostructured single crystalline Fe 3-δ O 4 (111) film (δ ≈ À0.06) is highly oriented along both out-of-plane and in-plane crystallographic orienta-

Hierarchical Multiscale Engineered Fe3O4/Ni Electrodes with Ultrafast Supercapacitive Energy Storage for Alternate Current Line‐Filtering

“…It has been previously demonstrated that the relatively small lattice mismatches (Δ a ) between layers (−2.3% for Au (111)/Ti (0001) and 3.0% for Ti (0001)/Al 2 O 3 (0001)) enabled the multilayer heteroepitaxial growth. [ 72 ] On the Au surface, 500 nm‐diameter polystyrene (PS) particles are self‐assembled to form periodic colloidal crystals. The voids inside the colloidal crystals are infiltrated with Ni by electrodeposition.…”

“…Despite the relatively large lattice match (‐14%) between Ni (111) and Au (111), only Ni (111) and Ni (222) reflections are observed for both dense Ni (D‐Ni) (middle of Figure 3a) and 3D mesostructured Ni (M‐Ni) (top of Figure 3a). The crystallite sizes ( D ) of nickel were estimated with the Ni (111) peaks using the Scherrer equation, [ 72,78 ] yielding 31 nm for D‐Ni and 33 nm for M‐Ni, respectively. As calculated D values of D‐Ni and M‐Ni are similar, we expect no significant difference in matrix electrical conductivities.…”

“…[ 54 ] As a result, there have been several studies on Fe 3 O 4 as a supercapacitor electrode, most of which were oriented toward improving the capacitance by combining Fe 3 O 4 with secondary materials such as carbon nanotubes, graphene, and reduced graphene oxides. [ 22,55–71 ] As far as we are aware, except for one study recently reported by our group, [ 72 ] its potential as an ultrafast response electrode has never been highlighted so far. Our previous study successfully demonstrates that epitaxially grown 3D mesostructured Fe 3 O 4 can respond as a pure capacitor to ultrafast changes in both DC and AC input.…”

Preparation of Ordered Fe3O4 Nanohoneycombs and Their Application in Capacitors

“…15 Various Fe 3 O 4 nanostructures, such as nanofibers, cellular thin films, and inverse opals, have been fabricated and investigated for their applications in capacitors. [5][6][7][8][9][10][11][12][13][14][15][16][17][18] Among them, the anodization of Fe substrates is a promising method for the preparation of Fe 3 O 4 electrodes for capacitors with excellent performance because it can form a porous oxide thin film with a large specific surface area and high structural controllability by using a simple experimental setup, including a DC power supply, an aelectrolyte, and a chiller for controlling the electrolyte temperature. 19,20 The anodization of metal substrates is also suitable as an electrode fabrication process for capacitors in that it can be applied to the preparation of large-area samples.…”