1. Efficient Electrocatalytic and Photoelectrochemical Hydrogen Generation Using MoS2 and Related Compounds 
Qi Ding, Bo Song, Ping Xu, Song Jin 
Chem 
Volume 1, Issue 5, Pages (November 2016)
DOI: /j.chempr
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3. Figure 1 Mechanisms and Activity Trend of HER Catalysis
(A) The mechanism of hydrogen evolution on the surface of an electrode in acidic solutions.
(B) The Sabatier plot for HER catalysts shows the exchange current densities plotted against the free energy of hydrogen adsorption. Materials near the top of the volcano curve are expected to be most active in HER.
From Jaramillo et al.34 Reprinted with permission from AAAS.
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4. Figure 2 Crystal Structures of the 2H, 3R, and 1T Polytypes of MoS2
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5. Figure 3
Various Strategies for Increasing the Active Edge Sites in MoS2 HER Catalysts
(A) STM image of an MoS2 nanoplate on Au [111] shows the bright rim around the edges, corresponding to the catalytically active edge sites. From Jaramillo et al.34 Reprinted with permission from AAAS.
(B) Transmission electron microscopy image of a MoS2 film produced by rapid sulfurization.
(C) Idealized structure of edge-terminated molybdenum chalcogenide films with the layers aligned perpendicular to the substrate, maximally exposing the edges of the layers. Reprinted with permission from Kong et al.35 Copyright 2013 American Chemical Society.
(D) Abbreviated scheme for the synthesis of double-gyroid mesoporous MoS2 engineered to preferentially expose edge sites for enhanced HER activity. Reprinted by permission from Macmillan Publishers Ltd: Nature Materials (Kibsgaard et al.38), copyright 2012.
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6. Figure 4 Introduction of S-Vacancy in MoS2
(A) Schematic of the top (upper panel) and side (lower panel) views of MoS2 with strained S vacancies on the basal plane, where S vacancies serve as the active sites for hydrogen evolution, and applied strain further tunes the HER activity.
(B) Linear sweep voltammetry curves for the Au substrate, Pt electrode, and MoS2 with different amounts of strain and S vacancies.
Reprinted by permission from Macmillan Publishers Ltd: Nature Materials (Li et al.44), copyright 2015.
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7. Figure 5
Conversion to the Metallic 1T Phase Enhances the HER Catalytic Activity
(A and B) Phase conversion from semiconducting 2H-MoS2 to 1T-MoS2 after lithium intercalation and exfoliation (A) and polarization curves showing dramatically enhanced electrocatalytic activity toward HER through chemical exfoliation and phase transitions (B). Reprinted with permission from Lukowski et al.36 Copyright 2013 American Chemical Society.
(C) Galvanostatic discharge curve representing the lithiation process of Li intercalating into the van der Waals gaps of MoS2 to donate electrons to the slabs and expand the layer spacing. The voltage monotonically drops to 1.2 V versus Li+/Li to reach a Li content of 0.28, after which the system undergoes a 2H- to 1T-MoS2 first-order phase transition, when the atomic structure changes from trigonal prismatic to octahedral and the electronic structure transits from semiconducting to metallic. Reprinted from Wang et al.51
(D and E) Scanning electron microscopy (SEM) image of chemically exfoliated MoS2 nanosheets deposited on SiO2 (D) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) image of chemically exfoliated MoS2 with octahedral coordination (1T phase) (E). The nanosheets are mostly composed of distorted regions with zigzag chains. Reprinted with permission from Voiry et al.49 Copyright 2013 American Chemical Society.
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8. Figure 6 Porous 1T-MoS2 Nanosheets as a High-Performance HER Catalyst
(A) J-V curves after iR correction show the HER electrocatalytic performance of various MoS2 nanosheet samples in comparison with a Pt wire.
(B–D) High-resolution STEM image (B), selected area electron diffraction pattern (C), and atomic force microscopy image (D) of the mesoporous (holey) 1T-MoS2 nanosheets.
Reprinted with permission from Yin et al.46 Copyright 2016 American Chemical Society.
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9. Figure 7 Coupling with Conductive Scaffolds
(A and B) Schematic of the solvothermal synthesis (A) and SEM and TEM (inset) images of MoS2-graphene nanocomposite (B). Reprinted with permission from Li et al.61 Copyright 2011 American Chemical Society.
(C) The polarization curves of the as-obtained Ni foam electrode (dashed line), the graphene-protected Ni foam electrode (solid line), and the graphene-protected Ni foam electrode with MoSx grown at 120°C (dotted line). Reprinted with permission from Chang et al.64 Copyright 2012 John Wiley & Sons.
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10. Figure 8
Amorphous MoSx and Examples of Molecular Mimics of MoS2 Catalyst
(A) Hydrogen evolution on amorphous MoSx. Reprinted with permission from Morales-Guio et al.12 Copyright 2014 American Chemical Society.
(B) HAADF-STEM image of MoSx catalyst suggests the arrangement of [Mo3] cluster units in a one-dimensional chain. Reprinted by permission from Macmillan Publishers Ltd: Nature Materials (Tran et al.72), copyright 2016.
(C) The relationship between the Mo-S-based molecular HER catalysts and the monolayer MoS2 with sulfur-rich edges (center): [(PY5Me2)MoS2]2+ (top), the dimeric analog [Mo2S12]2− cluster (left), and the trimeric analog [Mo3S13]2− cluster (right). Reprinted with permission from Huang et al.75 Copyright 2015 John Wiley & Sons.
(D) Hypothesized a-MoSx coordination polymer with [Mo3S13]2− building-block units sharing two of their three terminal disulfide bonds to form a polymeric chain. Some defect MoV=O sites are present within the polymer.Reprinted by permission from Macmillan Publishers Ltd: Nature Materials (Tran et al.72), copyright 2016.
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11. Figure 9 Amorphous MoSxCly and MoSexCly HER Catalysts
(A and B) Electron microscopy characterization of an amorphous MoSxCly-vertical graphene sample grown at 275°C (A) and SETM energy-dispersive X-ray spectroscopy mapping of C, Cl, S, and Mo elements for a piece of graphene sheet partially covered by MoSxCly (B), as indicated by the orange box in (A). Reprinted from Zhang et al.,77 published by The Royal Society of Chemistry.
(C and D) Electrochemical characterization of amorphous MoSxCly (solid circles) and MoSexCly (solid squares) thin films deposited on graphite substrates in comparison with crystalline MoS2 (open circles) and MoSe2 (open squares): (C) polarization curves and (D) Tafel analysis. Reprinted with permission from Ding et al.97 Copyright 2015 John Wiley & Sons.
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12. Figure 10
Schematic of a Water-Splitting Device Concept Utilizing Structured Solar Absorbers and a Proton-Permeable Membrane for Ion Transport
Reprinted with permission from Warren et al.84 Copyright 2014 American Chemical Society.
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13. Figure 11 Energy-Band Diagrams of Silicon Photocathodes
Band bending in (A) p-Si and (B) n+p-i photocathodes in contact with the H+/H2 redox couple in solution. The top diagrams show the interfaces in the dark, whereas the bottom diagrams show the interfaces under illumination. Ecb is the conduction band edge, Evb is the valence band edge, and EF is the Fermi level. EF,p and EF,n are the hole and electron quasi-Fermi levels, respectively, under illumination. The photovoltage (Voc) is larger for n+p-Si samples because of increased band bending at the n+/p interface in relation to the aqueous solution/p-Si interface. Reprinted with permission from Boettcher et al.93 Copyright 2014 American Chemical Society.
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14. Figure 12 PEC Hydrogen Evolution Using 1T-MoS2 on p-Si
(A and B) Comparison of top-down and cross-sectional (insets) SEM images of (A) 2H- and (B) 1T-MoS2/Si.
(C–E) Illustration of 1T-MoS2 catalyst on a p-Si semiconductor and the schematic band energy diagram of p-Si, 1T-MoS2, and H+/H2 redox couple at 0 V versus RHE in the dark (D) before and (E) after equilibrium.
(F) J-E curves of a CVD-grown 2H-MoS2/Si photocathode (CVD 2H), a CVD-grown 1T-MoS2/Si photocathode (CVD 1T), and a drop-casted 1T-MoS2/Si photocathode (drop-cast 1T) measured in 0.5 M H2SO4 under simulated 1 Sun irradiation. The J-E curve of a bare Si photocathode is also shown for comparison.
Reprinted with permission from Ding et al.78 Copyright 2014 American Chemical Society.
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15. Figure 13
PEC Hydrogen Generation Using MoQxCly Catalysts Coated on n+pp+ Si MPs
(A) Schematic of MoQxCly catalysts coated on n+pp+ Si MPs.
(B) J-V curves for amorphous MoSxCly/planar p-Si (purple stars), MoSxCly/Si MPs (red circles), MoSxCly/Si MPs (black squares), and Pt/Si MPs (blue triangles) photocathodes measured under simulated 1 Sun irradiation, as well as a dark control (pink hollow circles), in 0.5 M H2SO4.
Reprinted from Zhang et al.,77 published by The Royal Society of Chemistry. Reprinted with permission from Ding et al.97 Copyright 2015 John Wiley & Sons.
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16. Figure 14
PEC Hydrogen Generation Using MoS2-Related HER Catalysts and Other Semiconductors
(A) Cross-sectional SEM image of the protective layers (20 nm AZO and 100 nm TiO2) on Cu2O and (right) ca. 100 nm of MoS2+x film on top of the TiO2-protected Cu2O electrode. Scale bars, 200 nm. Reprinted by permission from Macmillan Publishers Ltd: Nature Communications (Morales-Guio et al.100), copyright 2014.
(B) Current-potential curves (yellow solid line) and photocathode conversion efficiencies (blue squares) of as-grown InP nanowire arrays with MoS3 in 1 M HClO4 under chopped AM 1.5G illumination. Reprinted with permission from Gao et al.102 Copyright 2014 American Chemical Society.
Chem 2016 1, DOI: ( /j.chempr )
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