Bottom‐up synthesized MoS2 interfacing polymer carbon nanodots with electrocatalytic activity for hydrogen evolution (original) (raw)
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ACS Sustainable Chemistry & Engineering, 2018
Herein, we report a simple in-situ hydrothermal synthetic method for the preparation of a novel three-dimensional (3D) nanoflowers forming with few-layered and expanded interlayer spacing MoS 2 nanoflakes via restricting the polymerization of guar gum and the growth of MoS 2. In this process, hexaammonium molybdate ((NH 4) 6 Mo 7 O 24 •4H 2 O) and thiourea (CH 4 N 2 S) acted as the precursor of molybdenum and sulfur respectively, while guar gum functioned as both the template of chemical reaction and carbon source. The obtained MoS 2 /guar gum carbon hybrid nanoflowers (MoS 2 /CF) in a well-assembled 3D nanoflowers architecture provides copious active sites and thus prevents inherent stacking among MoS 2 layers. Thanks to all these advantages, the electrochemical evaluation demonstrates that MoS 2 /CF-750 shows extraordinary HER electrocatalytic performances, possessing extremely low onset potential approximate 20 mV, the low overpotential of ~125 mV at 10 mA cm-2 and an Page 1 of 28 ACS Paragon Plus Environment ACS Sustainable Chemistry & Engineering 2 extraordinary small Tafel slope of 34 mV dec-1 , which is extremely identical to that of bulk platinum (Pt), "the gold benchmark" for hydrogen production. Moreover, the strong interactions between MoS 2 nanoflakes and guar gum enable MoS 2 /CF-750 excellent long-term stability and microstructural integrity, presenting nearly 100% activity retention after 2000 cycles and ~95% after 16 h of chronoamperometry assessment (0.15 V). The preparation strategy is simple, inexpensive, and readily scalable, and could be extended to diverse 3D non-noble metal electrocatalysts.
C, 2017
Hydrogen is an efficient fuel which can be generated via water splitting, however hydrogen evolution occurs at high overpotential, and efficient hydrogen evolution catalysts are desired to replace state-of-the-art catalysts such as platinum. Here, we report an advanced electrocatalyst that has low overpotential, efficient charge transfers kinetics, low Tafel slope and durable. Carbon nanofibers (CNFs), obtained by carbonizing electrospun fibers, were decorated with MoS 2 using a facile hydrothermal method. The imaging of catalyst reveals a flower like morphology that allows for exposure of edge sulfur sites to maximize the HER process. HER activity of MoS 2 decorated over CNFs was compared with MoS 2 without CNFs and with commercial MoS 2. MoS 2 grown over CNFs and MoS 2-synthesized produced about 374 and 98 times higher current density at −0.30 V (vs. Reversible Hydrogen Electrode, RHE) compared with the MoS 2-commercial sample, respectively. MoS 2-commercial, MoS 2-synthesized and MoS 2 grown over CNFs showed a Tafel slope of 165, 79 and 60 mV/decade, capacitance of 0.99, 5.87 and 15.66 mF/cm 2 , and turnover frequency of 0.013, 0.025 and 0.54 s −1 , respectively. The enhanced performance of MoS 2-CNFs is due to large electroactive surface area, more exposure of edge sulfur to the electrolyte, and easy charge transfer from MoS 2 to the electrode through conducting CNFs.
Nano Research, 2016
We report a three-dimensional hierarchical ternary hybrid composite of molybdenum disulfide (MoS 2), reduced graphene oxide (GO), and carbon nanotubes (CNTs) prepared by a two-step process. Firstly, reduced GO-CNT composites with three-dimensional microstructuresare synthesized by hydrothermal treatment of an aqueous dispersion of GO and CNTs to form a composite structure via π-π interactions. Then, MoS 2 nanoparticles are hydrothermally grown on the surfaces of the GO-CNT composite. This ternary composite shows superior electrocatalytic activity and stability in the hydrogen evolution reaction, with a low onset potential of only 35 mV, a Tafel slope of ~38 mV•decade −1 , and an apparent exchange current density of 74.25 mA•cm −2. The superior hydrogen evolution activity stemmed from the synergistic effect of MoS 2 with its electrocatalytically active edge-sites and excellent electrical coupling to the underlying graphene and CNT network.
Journal of Energy Chemistry, 2019
Metal-organic framework (MOF) derived hybrid materials have been developed as an efficient non-noblemetal electrocatalysts for clean energy conversion systems. In this work, a Co-based MOF containing nitrogen and oxygen heteroatoms (Co-NOMOF) mixed with the thiomolybdate [Mo 3 S 13 ] 2 − nanoclusters was used to prepare the N, S, O-doped carbon encapsulating Co 9 S 8 and MoS 2 (Co 9 S 8 /MoS 2 @NSOC) nanocomposite by one-step pyrolysis. The Co 9 S 8 /MoS 2 @NSOC nanocomposite exhibited remarkable catalytic performance for hydrogen evolution reaction (HER) with overpotential of 194 and 233 mV in 1 M KOH and 0.5 M H 2 SO 4 solution under 10 mA cm −2 , respectively, which was ascribed to the multiheteroatom-doped hierarchical porous carbon matrix and the synergistic effect of intrinsic activity of Co 9 S 8 and MoS 2. This work provides new opportunity for developing highly efficient non-precious metal electrochemical catalysts.
Electrochemistry Communications, 2012
An efficient electrocatalyst for hydrogen evolution has been developed based upon in situ reduction of MoS 2 on ordered mesoporous carbon nanospheres (MoS 2 /MCNs). The properties of MoS 2 /MCNs were characterised by scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. Polarisation curves and electrochemical impedance measurements were obtained for MoS 2 /MCNs modified glassy carbon electrodes. The MoS 2 /MCNs exhibit high catalytic activity for hydrogen evolution with a low overpotential and a very high current density. A theory outlining the origins of the Tafel slope for a Volmer-Heyrovsky (rate determining step) mechanism of hydrogen evolution at MoS 2 catalytic edge sites is presented.
Efficient Electrocatalytic Hydrogen Evolution from MoS2-Functionalized Mo2N Nanostructures
ACS Applied Materials & Interfaces, 2017
Molybdenum-based compounds and their composites were investigated as an alternative to Pt for hydrogen evolution reactions. The presence of interfaces and junctions between Mo 2 N and MoS 2 grains in the composites were investigated to understand their role in electrochemical processes. Here we found that the electrocatalytic activity of Mo 2 N nanostructures was enhanced remarkably by conjugation with few-layer MoS 2 sheets. The electrocatalytic performance of Mo 2 N−MoS 2 composites in the hydrogen evolution reaction (HER) was revealed from the high catalytic current density of ∼175 mA cm −2 (at 400 mV) and good electrochemical stability (more than 18 h) in acidic media. Increasing the amount of MoS 2 in the composite, decreases the HER activity. The mechanism and kinetics of the HER process on the Mo 2 N−MoS 2 surface were analyzed using Tafel slopes and charge transfer resistance.
Chemical Engineering Journal, 2017
The present article reports the synthesis of nanocomposites of polypyrrole along with non-precious metal chalcogenide, cobalt-disulfide. A simple sonoelectrochemical method was carried out in order to fabricate novel composite electrode materials composing polypyrrol, CoS 2 and decorated Pt nanoparticles on multi walled carbon nanotubes, MWCNTs. Studying on electrocatalytic activity revealed that the presence of CoS 2 nanoparticles along with MWCNTs and Pt nanoparticles played a prominent role in enhancement of proton reduction to hydrogen gas. The possible mechanism of electrocatalytic activity by nanocomposite films is also discussed. The PPy(CoS 2)MWCNTsPt nanocomposite film exhibits extremely low overpotential (0.03 V vs. RHE), and high current density for HER in acidic solution. The activity enhancement can be attributed to the large active electrochemical surface area of MWCNTs and also porous structure of PPy provides excellent attachment of CoS 2 and Pt nanostructures to the matrix. In addition, the HER is further improved due to stronger adsorption of hydrogen to the disulfide anions in CoS 2 structures.
Co/Fe-doped MoS2 Nanoparticles on Carbon Support as a Catalyst for Hydrogen Evolution Reaction
The challenge to replace fossil fuel with clean and renewable energies has led the scientific community to research alternative sources of energy. Because of the low-environmental impact and high-specific energy of hydrogen, interest in sustainable ways of producing it has increased. Water electrolysis is the best method to generate high-purity hydrogen without pollutants, but it is an energy-intensive route. The existing platinum (Pt) catalysts are highly efficient, but the cost and rarity of Pt limits its use. Therefore, seeking high-efficient and cost-effective catalyst for mass production of hydrogen is critical to the utilization of hydrogen energy. In 2005, Nørskov et al. reported that molybdenum disulfide (MoS2) showed good activity for hydrogen evolution reaction (HER). The work in this thesis aims to develop high-efficient molybdenum sulfide catalysts. Molybdenum trisulfide (MoS3) was synthesized from acidification of ammonium tetrathiomolybdate [(NH4)2MoS4] with the addition of sodium sulfide (Na2S • 9H2O) to the reaction mixture. The synthesis parameters such as carbon support, S:Mo atomic ratio, solvent (H2O, ethylene glycol (EG)), dopants (Co/Fe) and pH were systematically studied. The physical and chemical properties of the prepared catalysts were characterized by microscopy (SEM, TEM), x-ray spectroscopy (XPS), and elemental analysis and mapping (ICP, CHNS, STEM). The electrochemical activity toward HER was studied using voltammetry and impedance tests. In the first section of the study, MoS3 nanoparticles were synthesized on three carbon supports (graphene nanoplatelets (GNP), Ketjenblack EJ-300 and Vulcan XC 72R) with
Chemistry of Materials, 2016
Herein, we report a unique thermal synthesis method to prepare a novel two-dimensional (2D) hybrid nanostructure consisted of ultrathin and tiny-sized molybdenum disulfide nanoplatelets homogenously inlaid in graphene sheets (MoS /G) with excellent electrocatalytic performance for HER. In this process, molybdenum oleate served as the source of both molybdenum and carbon, while crystalline sodium sulfate (Na 2 SO 4) served as both reaction template and sulfur source. The remarkable integration of MoS 2 and graphene in well-assembled 2D hybrid architecture provided large electrochemically active surface area and a huge number of active sites and also exhibited extraordinary collective properties for electron transport and H + trapping. The MoS 2 /G inlaid nanosheets deliver ultrahigh catalytic activity towards HER among the existing electrocatalysts with similar compositions, presenting a low onset overpotential approaching 30 mV, a current density of 10 mA/cm 2 at ~110 mV, and a Tafel slope as small as 67.4 mV/dec. Moreover, the strong bonding between MoS 2 nanoplatelets and graphene enabled outstanding long-term electrochemical stability and structural integrity, exhibiting almost 100% activity retention after 1,000 cycles and ~97% after 100,000 seconds of continuous testing (under static overpotential of-0.15 V). The synthetic strategy is simple, inexpensive and scalable for large-scale production, and also can be extended to diverse inlaid 2D nano-architectures with great potential for many other applications.
Enhanced Electrocatalytic Activity of MoSx on TCNQ-Treated Electrode for Hydrogen Evolution Reaction
ACS Applied Materials & Interfaces, 2014
Molybdenum sulfide has recently attracted much attention because of its low cost and excellent catalytical effects in the application of hydrogen evolution reaction (HER). To improve the HER efficiency, many researchers have extensively explored various avenues such as material modification, forming hybrid structures or modifying geometric morphology. In this work, we reported a significant enhancement in the electrocatalytic activity of the MoS x via growing on Tetracyanoquinodimethane (TCNQ) treated carbon cloth, where the MoS x was synthesized by thermolysis from the ammonium tetrathiomolybdate ((NH 4) 2 MoS 4) precursor at 170°C. The pyridinic N-and graphitic N-like species on the surface of carbon cloth arising from the TCNQ treatment facilitate the formation of Mo 5+ and S 2 2− species in the MoS x , especially with S 2 2− serving as an active site for HER. In addition, the smaller particle size of the MoS x grown on TCNQ-treated carbon cloth reveals a high ratio of edge sites relative to basal plane sites, indicating the richer effective reaction sites and superior electrocatalytic characteristics. Hence, we reported a high hydrogen evolution rate for MoS x on TCNQ-treated carbon cloth of 6408 mL g −1 cm −2 h −1 (286 mmol g −1 cm −2 h −1) at an overpotential of V = 0.2 V. This study provides the fundamental concepts useful in the design and preparation of transition metal dichalcogenide catalysts, beneficial in the development in clean energy.