Molybdenum Disulfide/Nitrogen‐Doped Reduced Graphene Oxide Nanocomposite with Enlarged Interlayer Spacing for Electrocatalytic Hydrogen Evolution

Abstract

Facile design of low‐cost and highly active catalysts from earth‐abundant elements is favorable for the industrial application of water splitting. Here, a simple strategy to synthesize an ultrathin molybdenum disulfide/nitrogen‐doped reduced graphene oxide (MoS2/N‐RGO‐180) nanocomposite with the enlarged interlayer spacing of 9.5 Å by a one‐step hydrothermal method is reported. The synergistic effects between the layered MoS2 nanosheets and N‐doped RGO films contribute to the high activity for hydrogen evolution reaction (HER). MoS2/N‐RGO‐180 exhibits the excellent catalytic activity with a low onset potential of −5 mV versus reversible hydrogen elelctrode (RHE), a small Tafel slope of 41.3 mV dec−1, a high exchange current density of 7.4 × 10−4 A cm−2, and good stability over 5 000 cycles under acidic conditions. The HER performance of MoS2/N‐RGO‐180 nanocomposite is superior to the most reported MoS2‐based catalysts, especially its onset potential and exchange current density. In this work, a novel and simple method to the preparation of low‐cost MoS2‐based electrocatalysts with the extraordinary HER performance is presented.

Interlayer Nanoarchitectonics of Two‐Dimensional Transition‐Metal Dichalcogenides Nanosheets for Energy Storage and Conversion Applications

“…[140] Recent DFT calculation reveals that ∆G H value of MoS 2 can be reduced by 0.149 eV to achieve a more preferable value of −0.052 eV when the interlayer spacing is increased from 0.62 nm of ordinary MoS 2 nanosheets to 0.95 nm of expanded MoS 2 nanosheets (Figure 11A). [43] It suggests that interlayer expansion can provide MoS 2 nanosheets with faster proton/ electron adsorption and hydrogen release processes, which are preferable for high HER activity. As a typical example, Sun et al reported a microwave-assistant solvothermal method to synthesize MoS 2 nanostructures with an expanded interlayer spacing of 0.94 nm at temperatures ranging from 190 to 260 °C for HER application ( Figure 11B,C).…”

“…Improvement of electrical conductivity by intercalation of conductive NH 4 + ions into MoS 2 interlayers is considered to be responsible for the excellent HER performance. [141] Other examples of HER applications of interlayer-expanded MX 2 include 3D radially oriented MoS 2 nanospheres with an interlayer spacing of 0.707 nm, [98] vertically aligned Li-intercalated MoS 2 nanofilm with an interlayer spacing of 0.721 nm, [51] hollow structured MoS 2 micro/ nanospheres with an interlayer spacing of 0.78 nm, [142] MoS 2 nanoflowers assembled by amorphous nanosheets with an interlayer spacing of 0.80 nm, [143] multiphasic 1T/2H MoS 2 with an interlayer spacing of 0.93 nm, [93] oxygen-incorporated MoS 2 ultrathin nanosheets with an interlayer spacing of 0.95 nm, [77] MoS 2 /N-doped rGO nanocomposite with an interlayer spacing of 0.95 nm, [43] MoS 2x Se 2(1−x) nanotubes with an interlayer spacing of 0.98 nm, [144] MoS 2 nanosheets with an interlayer spacing of 1.01 nm, [145] 1T-MoSe 2 nanosheets with an interlayer spacing of 1.17 nm [82] and 1T-MoS 2 nanosheets with an interlayer spacing of 1.18 nm. [128] Poor intrinsic conductivity of semiconducting MX 2 suppresses the overall HER performance.…”

“…It is believed that the inserted NH 4 + ions would be released from the layers of MoS 2 at high temperatures. [43] [77] Copyright 2013, American Chemical Society, B) 1T-MoSe 2 , reproduced with permission. [82] Copyright 2016, The Royal Society of Chemistry, C) NH 3 -intercalated VS 2 , reproduced with permission.…”

“…A common strategy to improve the conductivity of MX 2 electrolysts is modification with conductive carbon or metal. [137,146,147] Recent studies on integration of carbon materials such as carbon nanotubes, [148,149] carbon boxes [150] and reduced graphene oxide [43] with interlayerexpanded MoS 2 for improving HER performance are extensively investigated. For instance, Lan and co-workers employed a one-step hydrothermal method to synthesize MoS 2 /N-doped rGO nanocomposite with interlayer spacing of 0.95 nm as HER electrocatalyst.…”

“…[42] Larger interlayer expansion (e.g., from 0.62 nm to 0.95 nm) in MoS 2 further lowers ∆G H by 0.149 eV. [43] Interlayer-expanded MX 2 intercalated with certain organic and inorganic species are considered as promising candidates for new kinds of hightemperature superconductors. [44] Interlayer-expanded MX 2 materials also exhibit increased specific surface area, which is promising for enhancing their performance in areas such as adsorption, catalysis etc.…”