Surface Engineering of Graphene Oxide Shells Using Lamellar LDH Nanostructures

Abstract

The discovery of graphene oxide (GO) has made a profound impact on varied areas of research due to its excellent physicochemical properties. However, surface engineering of these nanostructures holds the key to enhanced surface properties. Here, we introduce surface engineering of reduced GO (rGO) shells by radially grafting Ni–Co layered double hydroxide (LDH) lamella on rGO shells to form Ni–Co LDH@rGO. The morphology of synthesized Ni–Co LDH@rGO mimics dendritic cell-like three-dimensional (3D) hierarchical morphologies. Silica nanospheres form self-sacrificial templates during the reduction of GO shells to form rGO shells during the template-assisted synthesis. The radial growth of LDH lamellae during hydrothermal process on GO shells provides access to a significantly larger number of additional active redox sites and overcompensates the loss of pseudocapacitive charge storage centers during the reduction of GO to form rGO shells. This enables in the synthesis of novel surface-engineered rGO nanoshells, which provide large surface area, enhanced redox sites, high porosity, and easy transport of ions. These synthesized 3D dendritic cell-like morphologies of Ni–Co LDH@rGO show a high capacitance of ∼2640 F g–1. A flexible hybrid device fabricated using this nanomaterial shows a high energy density of ∼35 Wh kg–1 and a power density of 750 W kg–1 at 1 A g–1. No appreciable compromise in device performance is observed under bending conditions. This synthesis strategy may be used in the development of functional materials useful for potential applications, including sensors, catalysts, and energy storage.

Oriented Nanosheet-Assembled CoNi-LDH Cages with Efficient Ion Diffusion for Quasi-Solid-State Hybrid Supercapacitors

“…It can be observed from the Ragone plot (Figure 5e) that the energy densities of quasi-solid-state AC//CoNi-LDH 2 HSC reach 49−21.4 Wh kg −1 under 991.6−8373.9 W kg −1 . Meanwhile, the results are better than the listed data, including CC@ NiCo 2 Al-LDH//CC@ZPC (44−22 Wh kg −1 and 462−6286 W kg −1 ), 23 CoS x /Ni−Co LDH//AC (35.8−11.13 Wh kg −1 and 800−8014 W kg −1 ), 25 MnCo-LDH@Ni(OH) 2 //AC (47.9−9.8 Wh kg −1 and 750.7−5020.5 W kg −1 ), 53 Ni−Co LDH@rGO//rGO (35−19 Wh kg −1 and 750−3760 W kg −1 ), 54 MnCo 2 O 4 @Co 3 O 4 //AC (31−14.6 Wh kg −1 and 208.5−3326.6 W kg −1 ), 55 and GNR/Bi 2 Se 3 //GNR/Co 0.85 Se (30.9−18.5 Wh kg −1 and 559−6770 W kg −1 ). 56 From Figure 5f, the electronic timer and the electronic fan can be driven by one device, in which the calculagraph can work for about 90 min.…”

Heterogeneous assembly of Ni–Co layered double hydroxide/sulfonated graphene nanosheet composites as battery-type materials for hybrid supercapacitors

“…4c) is dominated by spin-orbit doublets of Co 2+ at binding energies of 782.4 and 797.9 eV together with those of Co 3+ at binding energies of 780.7 and 796.3 eV. 47 However, the slight variation on the ratio of Co 3+ to Co 2+ among all the electrode materials (Fig. 4d) implicates the stabilization effect of cobalt elements as building blocks on LDH host layers in addition to the predominance of nickel elements to increase transport channels of interfacial charge carriers.…”

Organic Electron Donor‐Acceptor Co‐intercalated NiMn‐LDHs – Photocatalysts with Enhanced Separation of Charge Carriers for Photocatalytic Reduction of CO2

“…The FT‐IR spectra of DAS, DNS, Ni 2 Mn−CO 3 and Ni 2 Mn‐DAS, DNS‐n were illustrated in Figure 1b. The absorption bands at 2700∼3700 cm −1 could be ascribed to the O−H stretching vibration of hydroxyl groups in LDH hydroxide layers and water molecules in the gallery of LDHs [24] . The peak at 1200 cm −1 was assigned to the stretching vibrations of −SO 3 − groups of guest molecules [25] .…”