Elsevier

Chemical Engineering Journal

Volume 315, 1 May 2017, Pages 355-363
Chemical Engineering Journal

Aerosol synthesis of molybdenum diselenide–reduced graphene oxide composite with empty nanovoids and enhanced hydrogen evolution reaction performances

https://doi.org/10.1016/j.cej.2017.01.032Get rights and content

Highlights

  • MoSe2–rGO composite powders with empty nanovoids are prepared by spray drying process.

  • Tafel slopes for bare MoSe2 and MoSe2–rGO composite powders are 120 and 57 mV dec−1, respectively.

  • MoSe2–rGO composite powders with unique porous structure showed outstanding HER performances.

Abstract

MoSe2–reduced graphene oxide (rGO) composite powders with unique structures containing empty nanovoids and excellent hydrogen evolution reaction (HER) performances were prepared using a pilot-scale spray-drying process. One-step post-treatment of the spray-dried powders produced the macroporous MoSe2–rGO composite with empty nanovoids through an intermediate MoO3–Se–GO composite. Ultrafine MoSe2 nanocrystals, which consisted of a few layers and were several nanometers in size, were uniformly dispersed on the surfaces of the MoSe2–rGO composite powders with the optimal rGO contents. The MoSe2–rGO–M composite (20 wt% rGO) had the optimized porous structure with a uniform distribution of MoSe2 nanocrystals and enough the rGO content for a fast electron transport, and thus exhibited the highest HER activity. The MoSe2–rGO–M composite powders exhibited a current density of 10 mA cm−2 at a small overpotential of 0.21 V, which was lower than that of bare MoSe2 (10 mA cm−2 at 0.31 V). The Tafel slopes for bare MoSe2 and MoSe2–rGO–M composite powders were 120 and 57 mV dec–1, respectively. The synergistic effects of rGO sheets and MoSe2 nanocrystals and the unique porous structure resulted in outstanding HER performance with a small Tafel slope and overpotential.

Introduction

Ever-increasing needs for energy consumption and depletion of conventional fossil fuels call for innovation in sustainable energy conversion technologies. Hydrogen, a promising energy carrier, has been widely utilized as an important fuel in sustainable energy conversion systems to replace conventional fossil fuels owing to its environmental friendliness and high energy density [1], [2], [3]. As for the production of hydrogen, the electrochemical water splitting has been proved to be eco-friendly and the most efficient technique, where hydrogen is generated from the electrochemical reduction of H+ [1], [2], [3], [4], [5]. Platinum (Pt) and its alloy have been widely known as the best catalysts owing to their extremely high catalytic activity and small overpotential. However, the mass production of hydrogen has been hampered by the low abundance and high cost of Pt. Considering this, many studies have centered on replacing Pt with earth-abundant catalysts having high activity.

Layered transition metal dichalcogenides (MX2, M = Mo, W; X = S, Se), a class of two-dimensional (2D), graphene-like materials, have attracted extensive interest in many fields, including electrocatalysis, energy storage, and gas sensing [1], [2], [3], [4], [5], [6], [7], [8]. Nanostructured MX2 materials with the maximum number of active edge sites and high electrocatalytic activity have recently been studied as noble metal-free electrocatalysts for the hydrogen evolution reaction (HER) [9], [10], [11]. Indeed, electrochemical water splitting has been demonstrated to be an eco-friendly and highly efficient technique in which hydrogen is generated from the electrochemical reduction of H+. Substantial efforts have been focused on maximizing the number of active edge sites and the conductivity of MX2-based electrocatalysts to enhance their HER performance [12], [13]. The nanostructured MX2 composites with carbon-related materials, such as carbon nanotubes (CNTs) and graphene, have also been studied to improve the HER performance by ameliorating the low conductivity of metal dichalcogenides [14], [15], [16]. Such carbon-related materials can also maximize the number of active edge sites of MX2 by minimizing the crystal growth during the preparation process [17], [18], [19].

Among the various transition metal dichalcogenides, MoS2 materials have been widely studied because of their high chemical stability and excellent electrocatalytic performance [20], [21], [22]. The improved HER performances of composites of MoS2 and carbon-related materials have also been investigated. MoSe2’s crystal structure is similar to that of MoS2 [23], [24]. Therefore, a few research groups have studied the synthesis and HER performances of composites of MoSe2 and carbon-related materials [25], [26], [27], [28]. Mao et al. demonstrated a high-performance HER catalyst composed of a 3D graphene network supporting perpendicularly oriented MoSe2 nanosheets [15]. Qu et al. synthesized ultrathin MoSe2 nanosheets with rich defects grown on the surface of carbon fiber cloth by a facile solvothermal method [27]. The resulting nanosheets exhibited excellent HER activity, including a small onset potential, a large exchange current density, and a small Tafel slope. Huang et al. synthesized a unique hierarchical nanostructure consisting of few-layered MoSe2 nanosheets that were perpendicularly grown on CNTs through a one-step solvothermal reaction [29]. Their nanosheets exhibited HER activity with a low onset potential of −0.07 V vs. the reversible hydrogen electrode (RHE), a small Tafel slope of 58 mV dec−1, and excellent long-term cycling stability. In previous studies, the composites of MoS2 and carbon-related materials have mainly been prepared via liquid solution processes. However, the use of an easily scalable process to produce composite powders of MoSe2 and carbon-related materials with regular morphologies has not been investigated.

The spray-drying process, which is a gas-phase reaction process, has been established as a powerful and efficient method for the pilot-scale production of composites of metal compounds with carbon-related materials, including reduced graphene oxide (rGO), CNTs, and amorphous carbon [30], [31], [32], [33], [34], [35], [36], [37]. The energy storage-related electrochemical properties of nanostructured metal oxides, sulfides, and selenides composited with carbon-related materials prepared by a simple spray-drying process have been widely studied [31], [33], [34], [35], [36]. However, to the best of our knowledge, the synthesis of MoSe2–rGO composite materials with high rGO contents and their HER performances have not been studied. Here, the MoSe2–rGO composite powders that have unique structures including empty nanovoids and exhibit excellent HER performances were prepared via a pilot-scale spray-drying process.

Section snippets

Sample preparation

MoSe2–rGO composite powders with three different rGO contents were prepared by a simple two-step process. The composite powders of ammonium molybdate, selenous acid, and GO nanosheets were prepared from a spray solution by a pilot-scale spray-drying process, as shown in Fig. S1. The temperatures at the inlet and outlet of the spray dryer were fixed at 250 °C and 120 °C, respectively. A two-fluid nozzle was used as an atomizer, and the atomization pressure was 2.0 bar. The concentration of ammonium

Results and discussion

The formation mechanism of macroporous MoSe2–rGO composite with empty nanovoids created by applying a pilot-scale spray-drying process is described in Scheme 1. A droplet (Scheme 1-1) with a size of several tens of microns containing ammonium molybdate, selenous acid, and GO nanosheets was formed with a pneumatic nozzle. Drying this droplet created the filled-structure composite powder (Scheme 1-2) of ammonium molybdate, selenous acid, and GO nanosheets. The Mo and Se components did not

Conclusions

The synthesis of MoSe2–rGO composite materials with high rGO contents via a spray-drying process and their HER performances were studied for the first time. The simple two-step procedure involving a pilot-scale spray-drying process produced MoSe2–rGO composite powders that had unique structures containing empty nanovoids and showed excellent HER performances. Eliminating the excess Se component resulted in empty nanovoids within the MoSe2–rGO composite powders. The MoSe2/rGO ratios of the MoSe2

Acknowledgements

This work was supported by a National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (NRF-015R1A2A1A15056049).

References (65)

  • J.M. Woods et al.

    One-step synthesis of MoS2/WS2 layered heterostructures and catalytic activity of defective transition metal dichalcogenide films

    ACS Nano

    (2016)
  • L.Y. Zhou et al.

    A scalable sulfuration of WS2 to improve cyclability and capability of lithium-ion batteries

    Nano Res.

    (2016)
  • S.K. Park et al.

    A facile and green strategy for the synthesis of MoS2 nanospheres with excellent Li-ion storage properties

    CrystEngComm

    (2012)
  • D.J. Late et al.

    Single-layer MoSe2 based NH3 gas sensor

    Appl. Phys. Lett.

    (2014)
  • X.L. Fan et al.

    Catalytic activity of MS2 monolayer for electrochemical hydrogen evolution

    J. Phys. Chem. C

    (2016)
  • Q.P. Lu et al.

    2D transition-metal-dichalcogenide-nanosheet-based composites for photocatalytic and electrocatalytic hydrogen evolution reactions

    Adv. Mater.

    (2016)
  • D.Y. Chung et al.

    Edge-exposed MoS2 nano-assembled structures as efficient electrocatalysts for hydrogen evolution reaction

    Nanoscale

    (2014)
  • D.J. Li et al.

    Molybdenum sulfide/N-doped cnt forest hybrid catalysts for high-performance hydrogen evolution reaction

    Nano Lett.

    (2014)
  • S. Mao et al.

    Perpendicularly oriented MoSe2/graphene nanosheets as advanced electrocatalysts for hydrogen evolution

    Small

    (2015)
  • Y.M. Jiang et al.

    Reduced graphene oxide-modified carbon nanotube/polyimide film supported MoS2 nanoparticles for electrocatalytic hydrogen evolution

    Adv. Funct. Mater.

    (2015)
  • Y.G. Li et al.

    MoS2 nanoparticles grown on graphene: an advanced catalyst for the hydrogen evolution reaction

    J. Am. Chem. Soc.

    (2011)
  • J. Luxa et al.

    Graphene-amorphous transition-metal chalcogenide (MoSx, WSx) composites as highly efficient hybrid electrocatalysts for the hydrogen evolution reaction

    ChemElectroChem

    (2016)
  • Y.F. Zhang et al.

    In-situ growth of few-layered MoS2 nanosheets on highly porous carbon aerogel as advanced electrocatalysts for hydrogen evolution reaction

    ACS Sustainable Chem. Eng.

    (2015)
  • S.P. Zhang et al.

    Constructing highly oriented configuration by few-layer MoS2: toward high-performance lithium-ion batteries and hydrogen evolution reactions

    ACS Nano

    (2015)
  • X.M. Geng et al.

    Three-dimensional structures of MoS2 nanosheets with ultrahigh hydrogen evolution reaction in water reduction

    Adv. Funct. Mater.

    (2014)
  • X.L. Zheng et al.

    Space-confined growth of MoS2 nanosheets within graphite: the layered hybrid of MoS2 and graphene as an active catalyst for hydrogen evolution reaction

    Chem. Mater.

    (2014)
  • S.H. Lin et al.

    Activating and tuning basal planes of MoO2, MoS2, and MoSe2 for hydrogen evolution reaction

    Phys. Chem. Chem. Phys.

    (2015)
  • D.S. Kong et al.

    Synthesis of MoS2 and MoSe2 films with vertically aligned layers

    Nano Lett.

    (2013)
  • Y.D. Liu et al.

    3D binder-free MoSe2 nanosheets/carbon cloth electrodes for efficient and stable hydrogen evolution prepared by simple electrophoresis deposition strategy

    Sci. Rep.

    (2016)
  • Z.Q. Liu et al.

    Colloidally synthesized MoSe2/graphene hybrid nanostructures as efficient electrocatalysts for hydrogen evolution

    J. Mater. Chem. A

    (2015)
  • B. Qu et al.

    Ultrathin MoSe2 nanosheets decorated on carbon fiber cloth as binder-free and high-performance electrocatalyst for hydrogen evolution

    ACS Appl. Mater. Interfaces

    (2015)
  • L. Zhang et al.

    Hierarchical MoS2 microboxes constructed by nanosheets with enhanced electrochemical properties for lithium storage and water splitting

    Energy Environ. Sci.

    (2014)
  • Cited by (40)

    • Hybrid fibers assembled from MoSe<inf>2</inf>/graphene heterostructures endow improved supercapacitive performance

      2022, Carbon
      Citation Excerpt :

      A typical example is molybdenum diselenides (MoSe2), which has been proven prospective electrode material for its high theoretical capacitance originating from the physical adsorption of electrolyte ions and variable valence state of Mo sites between +6 and +2 [16], tuneable band gap depending on crystal phase, and large interlayer spacing (0.64 nm). However, MoSe2 nanosheets are typically synthesized by chemical vapor deposition, solid phase reaction, and plasma-assisted/hydrothermal selenization, usually involving hazardous agents and complicated procedures yet with low yield [17–19]. Besides, these synthetic methods are incompatible with the commonly used fiber fabrication techniques, such as dry-spinning, coagulation-based wet-spinning, and hydrothermal assembling [20–22].

    • Facile process to utilize carbonaceous waste as a carbon source for the synthesis of low cost electrocatalyst for hydrogen production

      2020, International Journal of Hydrogen Energy
      Citation Excerpt :

      Platinum (Pt) is the most efficient electrocatalyst for this purpose but its low abundance and high cost, limits its usage for the large scale hydrogen production [7]. The transition metal-based compounds especially the molybdenum (Mo)-based chalcogenides, carbides, nitrides, and other alloys got attention due to their special surface features and activities [8–13]. Among all these compounds, molybdenum carbides have attained special significance as a highly efficient electrocatalyst due to their high conductivity and analogous d-band structure resembling Pt [9,14].

    View all citing articles on Scopus
    1

    These two authors contributed equally to this work.

    View full text