Toward Aerogel Electrodes of Superior Rate Performance in Supercapacitors through Engineered Hollow Nanoparticles of NiCo₂O₄

Abstract

A biomass‐templated pathway is developed for scalable synthesis of NiCo2O4@carbon aerogel electrodes for supercapacitors, where NiCo2O4 hollow nanoparticles with an average outer diameter of 30–40 nm are conjoined by graphitic carbon forming a 3D aerogel structure. This kind of NiCo2O4 aerogel structure shows large specific surface area (167.8 m2 g−1), high specific capacitance (903.2 F g−1 at a current density of 1 A g−1), outstanding rate performance (96.2% capacity retention from 1 to 10 A g−1), and excellent cycling stability (nearly without capacitance loss after 3000 cycles at 10 A g−1). The unique structure of the 3D hollow aerogel synergistically contributes to the high performance. For instance, the 3D interconnected porous structure of the aerogel is beneficial for electrolyte ion diffusion and for shortening the electron transport pathways, and thus can improve the rate performance. The conductive carbon joint greatly enhances the specific capacity, and the hollow structure prohibits the volume changes during the charge–discharge process to significantly improve the cycling stability. This work represents a giant step toward the preparation of high‐performance commercial supercapacitors.

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

“…Based on the mass loading of the active material on both cathode and anode, the ASC exhibited a maximum energy density of 51 W h kg −1 at a power density of 800 W kg −1 (Figure f), which is comparable to, or even higher than, those of state‐of‐the‐art Co 3 O 4 ‐based ASCs . The specific energy and power densities of our ASC device are also comparable to other electrode materials reported in literatures, such as carbon tube/NiCo 2 S 4 nanotube//AC (27.7 W h kg −1 at 263.6 W kg −1 ), NiO/C‐HS//AC (30.5 W h kg −1 at 193 W kg −1 ), GQDs/MnO 2 ‐3//NG (118 W h kg −1 at 12 351 W kg −1 ), Co 3 O 4 /PANI//AC (41.5 W h kg −1 at 800 W kg −1 ), G@NiO‐1//NGH (52.6 W h kg −1 at 800 W kg −1 ), NiMoO 4 //carbon nanotube film (54.3 W h kg −1 at 4344 W kg −1 ), CuS–AC//AC (24.88 W h kg −1 at 800 W kg −1 ), NiCo 2 O 4 HNPs//AC (71 W h kg −1 at 1852 W kg −1 ), (Note: activated carbon (AC), carbon hollow spheres (C‐HS), graphene quantum dots (GQDs), nitrogen‐doped graphene (NG), polyaniline (PANI), nitrogen‐doped graphene hydrogel (NGH), HNPs) and some transition metal oxide‐ and nitride‐based supercapacitors . Because the ASC device possessed a maximum working voltage of 1.6 V with excellent energy density, both charged ASCs in series could effectively operate a red light‐emitting diode (LED) (inset of Figure f).…”

Significantly Enhanced Electrochemical Redox for High‐Performance Electrochemical Capacitor via Active Ion‐Tunnel Oriented BaCoF4 Electrodes

“…[ 38,26 ] As demonstrated in Figure 7 , all the samples show mainly Co2p signals, which were cautiously fitted using a series of 20Lorentzian‐80Gaussian line shapes with the following triple restrictions: i) the background was corrected according to the Shirley model; ii) the peak full width at half‐maximum was set in a range of 1.6‐2.3 eV; and iii) the ratio of the 2p 3/2 and 2p 1/2 peak areas was fixed at two with a spin‐orbit splitting of 15.3 eV. Upon analysis, the as‐synthesized bulk BaCoF 4 contains a small amount of Co 3+ species with 2p 3/2 level of 778.1 eV while ‐oriented BaCoF 4 nanosheets only presents the primitive Co 2+ species (2p 3/2 level of 780.7 eV), [ 14,52 ] indicating less defects and stable surfaces for ‐oriented BaCoF 4 . After charge/discharge tests, both bulk and ‐oriented BaCoF 4 were dominated by Co 3+ species, leaving only a small quantity of Co 2+ species with its ratio of 1/4 to Co 3+ by Co2p 3/2 XPS analysis.…”

Synergy of Nb Doping and Surface Alloy Enhanced on Water–Alkali Electrocatalytic Hydrogen Generation Performance in Ti‐Based MXene

“…[22,23] While the two peaks at 856.1 and 874 eV indicate the existence of Ni 2+ . [24] The satellite peaks of the Ni 2p 1/2 and 2p 3/2 core levels are located at 880.2 and 861.4 eV, respectively. [23] The Co 2p spectrum was shown in Figure 3f, which were deconvoluted into seven peaks located at 803.7, 796.7, 793.7, 786.9, 781.7, 778.7, and 773.3 eV.…”