Hydrothermal and soft-templating synthesis of mesoporous NiCo2O4 nanomaterials for high-performance electrochemical capacitors

Construction of high-performance electrode materials of NiCo2O4 nanoparticles encapsulated in ultrathin N-doped carbon nanosheets for supercapacitors

Highly dispersed nitrogen doped carbon (N-C) is decomposed by 2-methylimidazole (C₄H₆N₂) and is used as a composite material with nickel cobaltite (NiCo₂O₄). The N-C and NiCo₂O₄ composites are obtained by a one-step hydrothermal method and subsequent calcination. In addition, N-C is used to control the morphology and structure of NiCo₂O₄ to obtain excellent capacitor materials. The N-C/NiCo₂O₄ electrode shows an excellent specific capacitance of 157.97 mA h g^-1 (1263.75 F g^-1) at 1 A g^-1. Herein, we successfully develop a N-C/NiCo₂O₄//AC asymmetric supercapacitor (ASC), which is prepared using N-C/NiCo₂O₄ as a cathode coupled with activated carbon (AC) as an anode at a voltage of 1.6 V. The prepared N-C/NiCo₂O₄//AC device shows an excellent volumetric energy density of 66.44 mW h kg^-1. The promising performance of N-C/NiCo₂O₄//AC illustrated its potential for portable supercapacitor applications.

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

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.

Self-supported nanoporous NiCo2O4 nanowires with cobalt-nickel layered oxide nanosheets for overall water splitting

Water splitting via the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in producing H2 and O2 is a very important process in the energy field. Developing an efficient catalyst which can be applied to both HER and OER is crucial. Here, a bifunctional catalyst, CFP/NiCo2O4/Co0.57Ni0.43LMOs, has been successfully fabricated. It exhibits remarkable performance for OER in 0.1 M KOH producing a current density of 10 mA cm(-2) at an overpotential of 0.34 V (1.57 V vs. RHE), better than that of the commercial Ir/C (20%) catalyst. Simultaneously, it also exhibits good catalytic performance for HER in 0.5 M H2SO4 producing a current density of 10 mA cm(-2) at an overpotential of 52 mV and a Tafel slope of 34 mV dec(-1), approaching that of the commercial Pt/C (20%) nanocatalyst. Particularly, CFP/NiCo2O4/Co0.57Ni0.43LMOs present better durability under harsh OER and HER cycling conditions than commercial Ir/C and Pt/C. Furthermore, an H-type electrolyzer was fabricated by applying CFP/NiCo2O4/Co0.57Ni0.43LMOs as the cathode and anode electrocatalyst, which can be driven by a single-cell battery. This bifunctional catalyst will be very promising in overall water splitting.

SERS-based immunoassay using a core–shell SiO2@Ag immune probe and Ag-decorated NiCo2O4 nanorods immune substrate

A novel sandwich structure consisting of the SiO₂@Ag immune probe and the Ag-decorated NNRs substrate was used to detect AFP and a detection limit is as low as 2.1 fg mL⁻¹.

N-Doped carbon supported Co3O4 nanoparticles as an advanced electrocatalyst for the oxygen reduction reaction in Al–air batteries

Low cost Co₃O₄/N-KB was proposed as a high performance catalyst for Al-air battery. The full battery using this catalyst in air electrode displayed a high discharge voltage plateau of ~1.52 V, comparable to that of the commercial Pt/C (20wt%).