Ni³⁺doped monolayer layered double hydroxide nanosheets as efficient electrodes for supercapacitors

Abstract

Ni(3+) doped NiTi layered double hydroxide (NiTi-LDH) monolayer nanosheets with a particle size of ∼ 20 nm and a thickness of ∼ 0.9 nm have been successfully prepared through a facile bottom-up approach. These NiTi-LDH monolayer nanosheets exhibit excellent supercapacitor performance, including a high specific pseudocapacitance (2310 F g(-1) at 1.5 A g(-1)) and long durability compared with bulk LDH, owing to highly exposed conductive Ni(3+) species (NiOOH) which lead to the increased mobility rate of surface charge and electrolyte-transfer. Therefore, this work is expected to take a significant step towards exploring novel 2D monolayer electrode materials with unique physical and chemical properties for applications in energy storage and conversion.

Ultrathin layered double hydroxide nanosheets with Ni(III) active species obtained by exfoliation for highly efficient ethanol electrooxidation

“…Fig. 3 shows the high-resolution Ni 2p 3/2 spectra of bulk NiAl-LDHs and NiAl-LDH-NSs, which are fitted and split into two different types: Ni(II) (855.9 eV) [32,33] and Ni(III) (857.2 eV) [21,34]. The bulk NiAl-LDHs exhibit a Ni 2p 3/2 XPS spectrum locating at binding energy of 855.9 eV, indicating Ni atom in the host layers of bulk NiAl-LDHs mainly existed as Ni(II).…”

“…The Ni(III) surface states in NiAl-LDH-NSs account for ~56.5%, versus ~10.7% in the bulk NiAl-LDHs. The growing amount of surface Ni(III) species in NiAl-LDH-NSs is possibly attributed to the change of the atomic environment of the Ni atoms in the layer after exfoliation into single layer [21,35]. As the Ni(III) is really active site for Ni-based EOR electrocatalysts, thus the presence of high content of Ni(III) in the ultrathin NiAl-LDH-NSs could be significantly improve their catalytic activity in the EOR.…”

“…For the NiAl-LDH-NS modified electrode, this pair of redox peak (peak b and b’) are also observed, and much larger CV curve areas for the redox peak are obtained. This indicates that the more active sites in NiAl-LDH-NSs are exposed due to reducing the thickness of LDHs [21]. Furthermore, it is very interesting that a new pair of redox peak (peak a and a’) of the NiAl-LDH-NS modified electrode appears at 0.34 V and 0.37 V, respectively (Fig.…”

“…While generally synthesized Ni oxides and hydroxides need undergo progressive oxidation from low valence states (Ni(II)) to high valence states (Ni(III)) during electrochemical process prior to the EOR [13,14]. Previous report [21] has testified that chemically oxidized NiOOH is extremely active in electrochemical reactions. Moreover, the partial conversion of Ni(II) to Ni(III) in Ni(II)-based catalyst may also enhance the electroconductivity significantly.…”

Cycling stability of ultrafine β-Ni(OH)2 nanosheets for high capacity energy storage device via a multilayer nickel foam electrode

“…Transition metal oxide or hydroxide-based nanomaterials with remarkable theoretical capacitances, such as RuO 2 [7], MnO 2 [8][9][10], NiO [11][12][13], Co(OH) 2 [14,15] and Ni(OH) 2 [16,17], are chosen as the alternative electrode materials. Among the investigated transition metal oxide or hydroxide-based nanomaterials, nickel-based compounds such as Ni(OH) 2 have attracted a large amount of attention due to their low toxicity, low cost and excellent electrochemical properties [16][17][18][19], in addition, Ni(OH) 2 is also a typical paramagnetic material [20].…”