Tailoring morphology of cobalt–nickel layered double hydroxide via different surfactants for high-performance supercapacitor

Abstract

Tailoring the morphology of cobalt–nickel layered double hydroxide (LDH) electrode material was successfully achieved via the process of cathodic electrodeposition by adding different surfactants (hexamethylenetetramine, dodecyltrimethylammonium bromide (DTAB) or cetyltrimethylammonium bromide). The as-prepared Co0.75Ni0.25(OH)2 samples with surfactants exhibited wrinkle-like, cauliflower-like or net-like structures that corresponded to better electrochemical performances than the untreated one. In particular, a specific capacitance of 1209.1 F g−1 was found for the cauliflower-like Co0.75Ni0.25(OH)2 electrode material using DTAB as the surfactant at a current density of 1 A g−1, whose structure boosted ion diffusion to present a good rate ability of 64% with a 50-fold increase in current density from 1 A g−1 to 50 A g−1. Accordingly, the asymmetric supercapacitor assembled by current LDH electrode and activated carbon electrode showed an energy density as high as 21.3 Wh kg−1 at a power density of 3625 W kg−1. The relationship between surfactant and electrochemical performance of the LDH electrode materials has been discussed.

Effect of Thermal Treatment on Nickel‐Cobalt Electrocatalysts for Glycerol Oxidation

“…In all samples, FT‐IR spectra (Figure S3) show a broad peak with two contributions at 1110 and 1060 cm −1 corresponding to the asymmetric and symmetric stretching modes of S−O bonds of intercalated sulfate ions [16] . In addition, the characteristic stretching vibrations of interlayer water molecules and nitrate ions were found at 1630 cm −1 and 1384 cm −1 , respectively, corroborating the formation of a layered structure [17] …”

“…The S 2p peak is a broad band centered at 168.7 eV, attributed to sulfate ions [20] . Finally, the O 1s peak presents two distinctive features; all the samples have a contribution centered at 531.5 eV corresponding to metal hydroxides and, moreover, the samples that were subjected to the thermal treatment exhibit a second intense band related to M−O−M bonds located at 529.8 eV [17] . This can be explained by the dehydration and the subsequent partial dehydroxylation reaction, preferentially yielding the oxide forms, [21] which was corroborated by the shift on the XRD patterns (Figure S5) for the thermally‐treated samples.…”

“…[16] In addition, the characteristic stretching vibrations of interlayer water molecules and nitrate ions were found at 1630 cm À 1 and 1384 cm À 1 , respectively, corroborating the formation of a layered structure. [17] In the SEM micrographies, the deposits clearly reveal two distinctive morphologies. On the one hand, a characteristic porous and laminar LDH structure that preserves the Ni/Co atomic ratio of the electrodeposition solution can be distinguished.…”

“…[20] Finally, the O 1s peak presents two distinctive features; all the samples have a contribution centered at 531.5 eV corresponding to metal hydroxides and, moreover, the samples that were subjected to the thermal treatment exhibit a second intense band related to MÀ OÀ M bonds located at 529.8 eV. [17] This can be explained by the dehydration and the subsequent partial dehydroxylation reaction, preferentially yielding the oxide forms, [21] which was corroborated by the shift on the XRD patterns (Figure S5) for the thermally-treated samples. Despite their low crystallinity, pristine samples can be indexed to nickel-based LDH (JCPDS 38-0715), which was partially transformed to nickel oxide phases (JCPDS 22-1189) or nickel cobaltite (JCPDS 20-0781).…”

Electrochemically Stable Cobalt–Zinc Mixed Oxide/Hydroxide Hierarchical Porous Film Electrode for High-Performance Asymmetric Supercapacitor

“…Metal oxides and hydroxides are the most widely used positive materials owing to their high theoretic capacitance [10,11,12,13]. Recently, it was found that metal-based mixed oxides/hydroxides (e.g., Co–Ni–Zn ternary oxide [14] and Co–Ni layered double hydroxide [15]) exhibit better capacitance performances compared to simple metal oxides and hydroxides. However, the low rate capability and poor cycling stability still hinder their practical applications in commercial supercapacitors.…”