Core–Shell Nitrogen‐Doped Carbon Hollow Spheres/Co₃O₄ Nanosheets as Advanced Electrode for High‐Performance Supercapacitor

Abstract

Co O /nitrogen-doped carbon hollow spheres (Co O /NHCSs) with hierarchical structures are synthesized by virtue of a hydrothermal method and subsequent calcination treatment. NHCSs, as a hard template, can aid the generation of Co O nanosheets on its surface; while SiO spheres, as a sacrificed-template, can be dissolved in the process. The prepared Co O /NHCS composites are investigated as the electrode active material. This composite exhibits an enhanced performance than Co O itself. A higher specific capacitance of 581 F g at 1 A g and a higher rate performance of 91.6% retention at 20 A g are achieved, better than Co O nanorods (318 F g at 1 A g and 67.1% retention at 20 A g ). In addition, the composite is employed as a positive electrode to fabricate an asymmetric supercapacitor. The device can deliver a high energy density of 34.5 Wh kg at the power density of 753 W kg and display a desirable cycling stability. All of these attractive results make the unique hierarchical Co O /NHCS core-shell structure a promising electrode material for high-performance supercapacitors.

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

“…The GCD curves (Figure 5c) of the three samples show that the discharging time of RGO/HSP-Co 3 O 4 is much longer and has smaller internal resistance (IR) drop than other samples, indicating higher specific capacitance and faster reaction kinetics. [13,[38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] The high rate performance can be attributed to the bubble nanosheet structure and fast electrolyte diffusion inside the whole electrode. It is worth noting that 57.8% of capacitance was maintained even at a high scan rate of 200 mV s −1 , indicating that the bubble-nanosheet-structured electrode shows excellent rate performance.…”

N,P Co‐Coordinated Manganese Atoms in Mesoporous Carbon for Electrochemical Oxygen Reduction

“…However, the sluggish oxygen reduction reaction (ORR) has severely restrained the potential commercialization of fuel cells, which requires the usage of expensive and fuel‐vulnerable platinum (Pt) based catalysts. Therefore, numerous carbon‐based nanomaterials have been developed to replace the Pt based composites . Among them, the nitrogen species coordinated first‐row transition metal (e.g., Co, Ni, and Fe) atoms in carbons (M–N–C) are widely considered as promising electrocatalysts for ORR .…”

“…By contrast, XPS peaks for P 2p are absent in the MnNC‐900 composite, indicating the detected P of the MnNPC‐900 is originated from its P dopants. Figure b shows the high‐resolution N 1s XPS spectrum of the MnNPC‐900 composite, which can be deconvoluted into pyridinic N (≈398.2 eV), Mn–N species (≈399.4 eV), graphitic N (≈401.2 eV), and oxidized N (≈404.0 eV), respectively . Concentrations of different N species for the catalysts are summarized in Table S1 (Supporting Information).…”

Cobalt Oxide Nanoparticles Embedded in N‐Doped Porous Carbon as an Efficient Electrode for Supercapacitor

“…Undoubtedly, the morphology of Co 3 O 4 has important influence on its electrochemical performance, and it is possible to gain excellent electrochemical performance via precise controlling the structure of Co 3 O 4 . Nevertheless, the cell capacitances from these reported literatures are still far from the theoretical capacitance (3560 F g −1 ) . It is accepted that the reasons for the lower practical specific capacitance are attributed to the low conductivity and limited number of active sites.…”