In Situ Generated Gas Bubble‐Directed Self‐Assembly: Synthesis, and Peculiar Magnetic and Electrochemical Properties of Vertically Aligned Arrays of High‐Density Co₃O₄ Nanotubes

Abstract

A novel and versatile gas bubble induced self‐assembly technique is developed for the one‐step fabrication of vertically aligned polycrystalline Co3O4 nanotube arrays (NTAs) by the rapid thermal decomposition of Co(NO3)2·6H2O on a flat substrate. In this protocol, the in situ generation and release of gas bubbles, which can be regulated by elaborately adjusting the kinetic factors such as reaction time, decomposition temperature and pressure as well as the content of the chemically adsorbed water, play a vital role in the formation of the Co3O4 NTAs. Due to the shape anisotropy, ordered hierarchically porous structure and high surface area, the as‐obtained Co3O4 NTAs show unique magnetic properties of a low Néel temperature and a large exchange bias field, as well as an initial discharge capacity up to 1293 mAh·g−1 at 35 mA·g−1 and the retention of a charge capacity as high as 895.4 mAh·g−1 after 10 cycles. This endows them with important potential use in magnetic shielding, magnetic recording media, and lithium ion batteries, etc. Due to the simplicity of the self‐assembly method, this process is applicable to the large‐scale production of the Co3O4 NTAs, and may be extended to other materials.

Hierarchically porous materials: synthesis strategies and structure design

“…Drug delivery has an equal need for hierarchically porous media to promote large storage capacity and controlled delivery in both a spacial and temporal manner. [67][68][69][70][71][72][73][74] Due to their short solid-state diffusion lengths and large surface areas, a wide range of hierarchically structured porous materials have been utilized to improve the performances of FCs, [38][39][40][41][42][43][44][45]95,96 LIBs [53][54][55][56][57] and supercapacitor [46][47][48][49][50][51][52][135][136][137][138][139][140] and in other energy storage applications. [58][59][60][61][62][63][64][65][66] All of these emerging applications are summarized in Table 1.…”

“…Following formation of the reactive hydroxy groups branched oligomers, polymers, nuclei with a metal oxo based skeleton and reactive residual hydroxo and alkoxy groups are generated through polycondensation processes (olation, oxolation). 51,[54][55][56] These three reactions (hydrolysis, oxolation and olation) are involved in the transformation of a molecular precursor into a metal oxo-macromolecular network or oxide nanoparticles. Careful control of the sol-gel process directly results in hierarchically porous materials without the need to use additional templates.…”

General Self‐Template Synthesis of Transition‐Metal Oxide and Chalcogenide Mesoporous Nanotubes with Enhanced Electrochemical Performances

“…Tr ansition-metal oxides (TMOs) and chalcogenides (TMCs) have been recognized as significant materials due to their promising applications in many fields. [8] Among them, cobalt-based TMOs and TMCs (e.g.C o 3 O 4 ,N iCo 2 O 4 ,C oS 2 , and CoSe 2 )are attracting increasing attention because of their good performance in photo-and electrochemical reductions, [9] Li-ion batteries, [10] oxygen-evolution reaction (OER), [11] hydrogen-evolution reaction (HER), [12] and magnetic properties [13] have been achieved. Thus,great effort has been devoted to the controlled synthesis of TMOs and TMCs.…”

Self-template synthesis of magnetic cobalt nanotube based on Kirkendall effect

“…Finally, the dried coreshell nanorod is subjected to be a controlled annealed process under Ar atmosphere to obtain the final Co nanotube via the carbon thermal reduction reaction (Co(CO 3 ) 0. 5 the sintering process, the core-shell nanorod is heated and kept at 250 1C for 30 min; and then the temperature increases and keeps at 300 1C for 60 min; finally the temperature is increased to 400 1C and kept at 400 1C for 100 min. The heating rate is 1 1C min À 1 all through the annealing treatment.…”

“…Quite a few kinds of nanotubes have been presented for the applications in the field of energy storage [2,3], catalysis [4], electronic or magnetic nanodevices [5], sensors [6], and biological/medical applications [7]. Recently, Fe, Co, Ni based metal and/or alloy nanotubes with magnetic properties have been investigated in great detail [8][9][10][11].…”