Synthesis of porous NiO nanocrystals with controllable surface area and their application as supercapacitor electrodes

Abstract

We report a facile way to grow various porous NiO nanostructures including nanoslices, nanoplates, and nanocolumns, which show a structure-dependence in their specific charge capacitances. The formation of controllable porosity is due to the dehydration and re-crystallization of β-Ni(OH) 2 nanoplates synthesized by a hydrothermal process. Thermogravimetric analysis shows that the decomposition temperature of the β-Ni(OH) 2 nanostructures is related to their morphology. In electrochemical tests, the porous NiO nanostructures show stable cycling performance with retention of specific capacitance over 1000 cycles. Interestingly, the formation of nanocolumns by the stacking of β-Ni(OH) 2 nanoslices/plates favors the creation of small pores in the NiO nanocrystals obtained after annealing, and the surface area is over five times larger than that of NiO nanoslices and nanoplates. Consequently, the specific capacitance of the porous NiO nanocolumns (390 F/g) is significantly higher than that of the nanoslices (176 F/g) or nanoplates (285 F/g) at a discharge current of 5 A/g. This approach provides a clear illustration of the process-structure-property relationship in nanocrystal synthesis and potentially offers strategies to enhance the performance of supercapacitor electrodes.

Preparation and capacitance properties of graphene/NiAl layered double-hydroxide nanocomposite

“…7, a 9.3% decrease in the specific capacitance was observed over the first 250 cycles; then, the value of the capacitance gradually recovered and the electrode thereafter reached a relatively stable state. The incensement is possibly due to the activation process that allows the trapped ions to gradually diffuse out [44]. The capacitance retention was nearly 100% of the initial capacitance after 1000 cycles, indicating excellent cycle stability, and this is mainly due to the stabilization effect of the graphene and well disperse of NiAl-LDH on the support.…”

Facile synthesis and electron transport properties of NiO nanostructures investigated by scanning tunneling microscopy

“…4 Among the TMOs, nickel oxide (NiO) has attracted a particular attention due to the fact that it is one of the relatively few TMOs with a stable band gap. Of recently, focus has shifted on NiO nanoparticles, due to their small size (<100 nm) and unique material and functional properties, such as a wide bandgap (∼3.88 eV), 2,3,5 high discharge capacity (∼638 mA h/g) 6 and specific capacitance (∼390 F/g), 7 high carrier density (∼7.35 × 10 18 cm -3 ), 8 and photon-to-current conversion efficiency (∼45%), 9 in addition to superb catalytic activity (42.3 gm -2 ) for CO oxidation, 10 which make them a highly desirable candidate for applications in electronics, electrochemical devices, photovoltaics, and catalysis, among others. Due to such attractive functional properties, a great deal of recent efforts have been devoted to develop application-relevant synthetic approaches, such as sol-gel embedded, 11 microemulsion precipitation, 12,13 and laser pulse deposition.…”

Prospects of Emerging Engineered oxide nanomaterials and their Applications

“…This crystallographic structural phenomenon has been detected in TiO 2 , Al 2 O 3 , and VO 2 oxides. up to now, many phases of polymorphs of MON have been reported in literature, such as eight for TiO 2 (rutile, anatase, brokite, TiO 2 -B (bronze), TiO 2 -R (ramsdellite), TiO 2 -H (hollandite), TiO 2 -II (columbite) and TiO 2 -III (baddeyite)), seven for Al 2 O 3 (α → alpha; γ → gamma, δ → delta, θ → theta, ι → iota, κ → kappa and σ → sigma) and nine for VO 2 (rutile (R), monoclinic (M), triclinic (T), tetragonal (A), monoclinic (B), tetragonal (C), monoclinic (D), VO 2 with a BCC structure and paramontroseite VO 2 ) [63][64][65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81] .…”