Co₃O₄ Supraparticle‐Based Bubble Nanofiber and Bubble Nanosheet with Remarkable Electrochemical Performance

Abstract

Hollow nanostructures based on transition metal oxides (TMOs) with high surface‐to‐volumetric ratio, low density, and high loading capacity have received great attention for energy‐related applications. However, the controllable fabrication of hybrid TMO‐based hollow nanostructures in a simple and scalable manner remains challenging. Herein, a simple and scalable strategy is used to prepare hierarchical carbon nanofiber (CNF)‐based bubble‐nanofiber‐structured and reduced graphene oxide (RGO)‐based bubble‐nanosheet‐structured Co 3 O 4 hollow supraparticle (HSP) composites (denoted as CNF/HSP‐Co 3 O 4 and RGO/HSP‐Co 3 O 4 , respectively) by solution self‐assembly of ultrasmall Co 3 O 4 nanoparticles (NPs) assisting with polydopamine (PDA) modification. It is proved that the electrochemical performance of Co 3 O 4 NPs can be greatly enhanced by the rationally designed nanostructure of bubble‐like supraparticles combined with carbon materials as excellent electrodes for supercapacitors. The favorable structure and composition endow the hybrid electrode with high specific capacitance (1435 F g −1 /1360 F g −1 at 1 A g −1 /5 mV s −1 ) as well as fantastic rate capability. The asymmetric supercapacitors achieve an excellent maximum energy density of 51 W h kg −1 and superb electrochemical stability (92.3% retention after 10 000 cycles). This work suggests that the rational design of electrode materials with bubble‐like superstructures provides an opportunity for achieving high‐performance electrode materials for advanced energy storage devices.

Metal–Organic Framework (MOF)‐Derived Electron‐Transfer Enhanced Homogeneous PdO‐Rich Co3O4 as a Highly Efficient Bifunctional Catalyst for Sodium Borohydride Hydrolysis and 4‐Nitrophenol Reduction

“…[22] The lattice spacing of 0.21 nm corresponds to the (4 00)c rystal plane of Co 3 O 4 . [23] As shown in Figure S6 (in the Supporting Information),t he energy-dispersive X-ray (EDX) spectrum of PdO-Co 3 O 4 confirms the existence of Pd, Co, and Oe lements. The high angle annular dark field (HAADF)-STEMa nd the elemental mappings show that Pd, Co, and Oe lementsa re evenly distributed in the framework structure of the PdO-Co 3 O 4 composite (Figure 2f).…”

“…[24] Figure 3a is the high-resolution Co 2p spectra of PdO-Co 3 O 4 and Co 3 O 4 .T he Co 2p 3/2 region of the PdO-Co 3 O 4 polyhedron is deconvoluted into four peaks at 779.4, 780.9, 785.0, and 789.4 eV,c orresponding to the Co 3 + ,C o 2 + ,a nd two satellite peaks, respectively. [23,25] It can be seen that as mall number of coexisting Pd speciesm akes the area ratio of Co 3 + /Co 2 + markedly increase from 2.46 to 3.12. The high-resolution O1ss pectra of the two samples were furthera nalyzed in Figure 3b,i nw hich three signals generated at 529.4,5 30.7, and 532.0 eV are attributed to metal oxides, oxygen vacancies, and adsorbed H 2 O, respectively.…”

Flexible heteroatom‐doped porous carbon nanofiber cages for electrode scaffolds

“…1,2 Among these materials, porous carbon nanofibers (PCNFs) have attracted intensive studies owing to their virtues of plentiful pore structures and ability of forming flexible scaffolds. [3][4][5] Extensive studies have been developed to fabricate PCNFs, but it is difficult to control their porosity and flexibility simultaneously since mechanical strength is generally inversely proportional to pore volumes. To ensure structural integrity, most PCNFs only contain meso-and micropores with low pore volumes, which greatly limited the performance of PCNFs as scaffold materials.…”

“…In the past few decades, porous nanostructured carbon materials, including activated carbon, carbon nanofibers (CNFs), carbon nanotubes (CNTs) and graphene have received great attention for energy storage devices due to their large specific surface areas (SSAs), low density, and high chemical stability 1,2 . Among these materials, porous carbon nanofibers (PCNFs) have attracted intensive studies owing to their virtues of plentiful pore structures and ability of forming flexible scaffolds 3‐5 . Extensive studies have been developed to fabricate PCNFs, but it is difficult to control their porosity and flexibility simultaneously since mechanical strength is generally inversely proportional to pore volumes.…”

High-performance flexible hybrid supercapacitor based on NiAl layered double hydroxide as a positive electrode and nitrogen-doped reduced graphene oxide as a negative electrode

“…In the last few years, wearable electronic devices attracted widespread attention, and consequently led to a steady increase demand of energy storage devices with enhanced flexibility and good mechanical properties [1][2][3][4][5][6][7]. Moreover, due to the negative impact of global warming and the increasing fuel consumption, renewable and clean energy supply devices drew more and more interest [8,9].…”