MoS2 quantum dot-modified MXene nanoflowers for efficient electrocatalytic hydrogen evolution reaction (original) (raw)
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1 In situ study of graphene oxide quantum dot-MoSx 2 nanohybrids as hydrogen evolution catalysts 3
2020
Graphene quantum dots (GOQDs)-MoSx nanohybrids with different MoSx 14 stoichiometries (x = 2 and 3) were prepared in order to investigate their chemical stability under 15 hydrogen evolution reaction (HER) conditions. Combined photoemission/electrochemical 16 (XPS/EC) measurements and operando X-ray absorption spectroscopy (XAS) were employed to 17 determine the chemical changes induced on the MoSx-based materials as a function of the applied 18 potential. This in situ characterization indicates that both MoS2 and MoS3 materials are stable under 19 operating conditions, although sulphur terminal sites in the MoS3 nanoparticles are converted from 20 S-dimer (S22-) to S-monomer (S2-), which constitute the first sites where the hydrogen atoms are 21 adsorbed for their subsequent evolution. In order to complete the characterization of the 22 GOQDs-MoSx nanohybrids, the composition and particle size were determined by X-ray 23 photoemission spectroscopy (XPS), X-ray diffraction (XRD) and...
In Situ Study of Graphene Oxide Quantum Dot-MoSx Nanohybrids as Hydrogen Evolution Catalysts
Surfaces
Graphene quantum dots (GOQDs)-MoSx nanohybrids with different MoSx stoichiometries (x = 2 and 3) were prepared in order to investigate their chemical stability under hydrogen evolution reaction (HER) conditions. Combined photoemission/electrochemical (XPS/EC) measurements and operando X-ray absorption spectroscopy (XAS) were employed to determine the chemical changes induced on the MoSx-based materials as a function of the applied potential. This in situ characterization indicates that both MoS2 and MoS3 materials are stable under operating conditions, although sulfur terminal sites in the MoS3 nanoparticles are converted from S-dimer (S22−) to S-monomer (S2−), which constitute the first sites where the hydrogen atoms are adsorbed for their subsequent evolution. In order to complete the characterization of the GOQDs-MoSx nanohybrids, the composition and particle size were determined by X-ray photoemission spectroscopy (XPS), X-ray diffraction (XRD) and Raman spectroscopy; whereas th...
2018
We designed solution-processed, flexible hybrid graphene flake/2H-MoS2 quantum dot (QD) heterostructures, showing enhanced electrocatalytic activity for the hydrogen evolution reaction (HER) with respect to their native individual components. The 2H-MoS2 QDs are produced through a scalable, environmentally friendly, one-step solvothermal approach from two-dimensional (2D) 2H-MoS2 flakes obtained by liquid phase exfoliation (LPE) of their bulk counterpart in 2-Propanol. This QDs synthesis avoids the use of high boiling point and/or toxic solvents. Graphene flakes are produced by LPE of graphite in N-Methyl-2-pyrrolidone. The electrochemical properties of 2H-MoS2 QDs and their HER-favorable chemical and electronic coupling with graphene enable to reach a current density of 10 mA/cm^2 at an overpotential of 136 mV, surpassing the performances of graphene flake/2H-MoS2 (1T-MoS2) flake heterostructures. Our approach provides a shortcut, viable and cost-effective method for enhancing the ...
Energy & Environmental Science, 2013
Ultrasmall molybdenum sulfide nanoparticles with diameters of 1.47 AE 0.16 nm were fabricated from bulk MoS 2 by a combination of ultrasonication and centrifugation. The nanoparticles were then assembled on an Au surface to form a film with high electrocatalytic activity for hydrogen evolution reaction (HER). A Tafel slope of 69 mV per decade was measured for this film and the onset potential was estimated to be À0.09 V. The small loading (1.03 mg cm À2 ) and the high current density (0.92 mA cm À2 at h ¼ 0.15 V) demonstrated extremely high catalytic efficiency. X-ray photoelectron spectroscopic results revealed that the assembled nanoparticle film was sulfur enriched with abundant S edges and a structural rearrangement of the S rich particles might occur during the self-assembly process, resulting in significantly enhanced electrocatalytic activity for HER. Electrochemical impedance measurements suggested that the assembling process optimized the conductivity of the nanoparticle film, which contributed to the enhanced HER catalytic activity. Our research has provided a new way to synthesize active molybdenum sulfide nanoparticles for HER and a new approach to achieve enrichment of S edges on molybdenum sulfide, which might have potential use not only for electrocatalytic HER, but also for photoelectrocatalytic HER and plasmon-enhanced water splitting.
ACS Applied Materials & Interfaces, 2018
Due to its unique electronic band characteristics (presence of d-orbital in both Mo and Se atoms), MoSe 2 has potential to exhibit high electrical conductivity and superior hydrogen evolution reactions (HER) kinetics when compared to other transition metal dichalcogenides (TMDs). Though various strategies were employed earlier to obtain MoSe 2 structure with different shape and morphology, precise control on achieving both Mo-and Se-edge sites and understanding their interaction with reactants in HER remains to be challenging. Here, we successfully demonstrate the vapor diffusion method to grow highly crystalline MoSe 2 nanoflowers on carbon cloth in a vertical orientation. Uniformly dispersed nanoflowers with Mo-and Se-edge sites exhibited remarkable electrocatalytic activity on hydrogen reduction in terms of low Tafel slope and high exchange current density. The existence of a strong interaction between MoSe 2 and carbon cloth assists in long-term hydrogen production and confirms the exceptional durability of the catalyst. A comprehensive evidence for hydrogen adsorption on dual active sites viz., Mo-and Se-edges of MoSe 2 is provided using Xray photoelectron spectroscopy (XPS) and in situ Raman spectroscopy containing a specially designed liquid immersion objective lens.
Metals
It is expected that utilization of molybdenum disulfide (MoS2)-based nanostructured electrocatalysts might replace the Pt-group electrodes most effectively applied for hydrogen evolution reaction from water. Therefore, in the past two decades, various approaches have been reported for fabrication of nanostructured MoS2-based catalysts, but their applications in practice are still missing due to lower activity and stability. We envisaged that the knowledge about the peculiarities of MoS2 nanoplatelets attachment to various conductive substrates by hydrothermal processing could be helpful for fabrication of more active and stable working electrodes. Therefore, in this study, the hydrothermal syntheses at the Mo, Ti, Al, anodized Ti, and hydrothermally designed titanium suboxide substrates were performed; the electrodes obtained were characterized; and hydrogen evolution reaction (HER) activity was tested. In this way, MoS2-based HER catalyst possessing a surprising stability and a low...
Hydrothermal synthesis of 2D MoS2 nanosheets for electrocatalytic hydrogen evolution reaction
Nanostructured molybdenum disulfide (MoS2) is a very promising catalyst for producing molecular hydrogen by electrochemical methods. Herein, we have designed and synthesized highly electocatalytically active 2D MoS2 nanosheets (NS) from molybdenum trioxide (MoO3) by a facile hydrothermal method and have compared their electrocatalytic activities for hydrogen evolution reaction (HER). The electrochemical characterization was performed using linear sweep voltammetry (LSV) in acidic medium. The MoS2 NS show a HER onset potential at about 80 mV vs. reversible hydrogen electrode (RHE) which is much lower than MoO3 (300 mV). The MoS2 NS and MoO3 show a current density of 25 mA cm2 and 0.3 mA cm2, respectively at an overpotential of 280 mV vs. RHE. The MoS2 NS showed an 83 times higher current density when compared to MoO3. The Tafel slopes of the MoS2 NS and MoO3 were about 90 mV per dec and 110 mV per dec respectively. This suggests that MoS2 NS are a better electrocatalyst when compared to MoO3 and follow the Volmer–Heyrovsky mechanism for HER.
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.