Controlled Self-Assembled NiFe Layered Double Hydroxides/Reduced Graphene Oxide Nanohybrids Based on the Solid-Phase Exfoliation Strategy as an Excellent Electrocatalyst for the Oxygen Evolution Reaction

Abstract

Layered double hydroxides (LDHs), as an effective oxygen evolution reaction (OER) electrocatalyst, face many challenges in practical applications. The main obstacle is that bulk materials limit the exposure of active sites. At the same time, the poor conductivity of LDHs is also an important factor. Exfoliation is one of the most direct and effective strategies to increase the electrocatalytic properties of LDHs, leading to exposure of many active sites. However, developing an efficient exfoliation strategy to exfoliate LDHs into stable monolayer nanosheets is still challenging. Therefore, we report a new and efficient solid-phase exfoliation strategy to exfoliate NiFe LDH and graphene oxide (GO) into monolayer nanosheets and the exfoliating ratios of NiFe LDH and GO can reach up to 10 and 5 wt %, respectively. Based on the solid-phase exfoliation strategy, we accidentally discovered that there is a dynamic evolution process between NiFe-LDH nanosheets (NiFe-LDH-NS) and GO nanosheets (GO-NS) to assemble new NiFe-LDH/GO nanohybrids, i.e., NiFe-LDH-NS could be horizontal bespreading on GO-NS or well-organized standing on GO-NS, or both simultaneously. The electrocatalytic OER property test results show that NiFe-LDH/RGO-3 (NFRG-3) nanohybrids obtained by the reduction treatment of NiFe-LDH/GO-3 (NFGO-3) nanohybrids, in which NiFe-LDH-NS are well-organized standing on GO-NS, have excellent electrocatalytic properties for OER in an alkaline solution (with a small overpotential of 273 mV and a Tafel slope of 49 mV dec–1 at the current density of 30 mA cm–2). The excellent electrocatalytic properties for OER of NFRG-3 nanohybrids could be attributed to the unique three-dimensional arraylike structure with many active sites. At the same time, reduced graphene oxide (RGO) with excellent conductivity can improve the charge-transfer efficiency and synergistically improve OER properties of nanohybrids.

Ultrasound-excited hydrogen radical from NiFe layered double hydroxide for preparation of ultrafine supported Ru nanocatalysts in hydrogen storage of N-ethylcarbazole

“…From Fig. 4 (b), two peaks appeared at 855.6 eV and 873.4 eV, which corresponded to 2p 3/2 and 2p 1/2 of Ni 2+ [44] . From Fig.…”

NiFe LDH@Super P Nanocomposite as an Efficient Electrocatalyst for Oxygen Evolution Reaction

“…The diffraction peaks of the samples are indexed to NiFe LDH, agreeing well with the standard powder diffraction patterns (JCPDF no. 40-0215) [8]. Specifically, the characteristic peaks of the (003), ( 006), ( 012), ( 110) and (113) crystal planes of NiFe LDH are located at 11.6°, 23.45°, 34.4°, 59.9° and 61.3° respectively, and the peak shape is sharp, indicating that the crystallinity of the synthesized sample is high.…”

Superactive NiFe-LDH/graphene nanocomposites as competent catalysts for water splitting reactions

“…9(b)). 73 This process revealed the dynamic growth evolution of NiFe-LDH NS on GO NS (horizontal spreading or vertical alignment or both) and provided information about the fully exposed active sites for interfacial interactions. The NiFe-LDH/RGO heterostructure with the vertical growth of NiFe-LDH NS displayed superior electrocatalytic OER activity with a small Tafel slope of 49 mV dec −1 and overpotential of 273 mV at exchange current density of 30 mA cm −2 under basic medium.…”

“…The strong metal-rGO bonding interactions, in terms of the overlapping of the dsp and sp 2 orbitals of rGO with Ni(OH) 2 and the Fe(OH) 3 layer of NiFe-LDH, are responsible for the photocatalytic and electrocatalytic activities. 72,73 Similarly, NiFe-LDH in combination with heteroatom-doped graphene, 74 and graphene hydrogel 75 were reported to exhibit superior water splitting performances. Yet, heteroatom-doped graphene is advantageous because of its chemistry containing defective sites for binding the transition metal cations of LDH.…”