S.J. Shi

Hierarchical NiCo2O4@NiCo2O4 Core/Shell Nanoflake Arrays as High-Performance Supercapacitor Materials

Hierarchical NiCo2O4@NiCo2O4 core/shell nanoflake arrays on nickel foam for high-performance supercapacitors are fabricated by a two-step solution-based method which involves in hydrothermal process and chemical bath deposition. Compared with the bare NiCo2O4 nanoflake arrays, the core/shell electrode displays better pseudocapacitive behaviors in 2 M KOH, which exhibits high areal specific capacitances of 1.55 F cm(-2) at 2 mA cm(-2) and 1.16 F cm(-2) at 40 mA cm(-2) before activation as well as excellent cycling stability. The specific capacitance can achieve a maximum of 2.20 F cm(-2) at a current density of 5 mA cm(-2), which can still retain 2.17 F cm(-2) (98.6% retention) after 4000 cycles. The enhanced pseudocapacitive performances are mainly attributed to its unique core/shell structure, which provides fast ion and electron transfer, a large number of active sites, and good strain accommodation.

One-step fabrication of nanostructured NiO films from deep eutectic solvent with enhanced electrochromic performance

Nanostructured NiO thin films were directly prepared by simple and efficient electrodeposition in a choline chloride-based ionic liquid. Uniform granules and some open voids between these granules are observed in the film deposited at 70 °C, while the film becomes compact and the NiO particles are 2–6 nm in size when the electrodeposition temperature is 90 °C. The optical transmittance of the film increased with the increase of the electrodeposition temperature. Although the electrochromic switching and reaction kinetics of the NiO film deposited at low temperature are fast due to the presence of metallic Ni and some voids, little transmittance modulation occurs in the wavelength range of 300–900 nm. In contrast, the NiO film deposited at high temperature exhibits high optical modulation of 67% at 550 nm, high coloration efficiency (98 cm2 C−1 at 400 nm, 92 cm2 C−1 at 550 nm and 51 cm2 C−1 at 750 nm), good memory effect and cycling durability.