Mapping the electrocatalytic activity of MoS<sub>2</sub> across its amorphous to crystalline transition

Choi, Yun Hyuk; Cho, Junsang; Lunsford, Allen M.; Al‐Hashimi, Mohammed; Fang, Lei; Banerjee, Sarbajit

doi:10.1039/c6ta10316b

Cited by 47 publications

(56 citation statements)

References 68 publications

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“…Through irradiation with the two‐subpulse train, the ratio of Mo V defect species could be maximized and the ratio of bridging and terminal S 2 2− ligands could be controlled, which resulted in the a‐MoS x ‐250/10 catalysts possessing excellent HER catalytic activity with a low Tafel slope of 40 mV dec −1 , a high C dl of 74.47 mF cm −2 , a large j 250 of 516 mA cm −2 , and relatively good stability. The HER catalytic activity of the a‐MoS x ‐250/10 materials in this study is comparable with that of the a‐MoS x materials prepared using other reported methods, which are listed in Table S1 (Supporting Information).…”

Section: Resultssupporting

confidence: 75%

Controllable Synthesis of Nanosized Amorphous MoS_x Using Temporally Shaped Femtosecond Laser for Highly Efficient Electrochemical Hydrogen Production

Jiang

et al. 2018

Adv Funct Materials

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Amorphous molybdenum sulfide (a-MoS x ) is regarded as a promising electrocatalyst for hydrogen evolution reaction (HER) due to its disorder structures with a significant number of defect-rich active sites. Here, a green, one-step, and controllable method is developed to photoregulate the chemical reactions and synthesize nanosized a-MoS x by temporally shaped femtosecond laser ablation of ammonium tetrathiomolybdate aqueous solution. By adjusting the laser energy and pulse delay to control photoinduced and/or photothermal-induced reduction/oxidation, the S to Mo ratio x can be modulated from 1.53 to 3.07 and the ratio of the Mo V defect species, bridging S 2 2− , and terminal S 2 2− ligands can be controlled. The optimized a-MoS x catalysts (x = 2.73) exhibit high catalytic activity with a low Tafel slope of 40 mV dec −1 , high double-layer capacitance of 74.47 mF cm −2 , and large current density of 516 mA cm −2 at an overpotential of 250 mV. The high catalytic activity can be mainly attributed to Mo V defect species and bridging S 2 2− ligands, or most likely dominated by the Mo V defect species. This study not only provides an alternatively controllable method to prepare a-MoS x as efficient HER catalysts but also contributes to the understanding of the origin of its catalytic activity.

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Section: Resultssupporting

confidence: 75%

Controllable Synthesis of Nanosized Amorphous MoS_x Using Temporally Shaped Femtosecond Laser for Highly Efficient Electrochemical Hydrogen Production

Jiang

et al. 2018

Adv Funct Materials

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“…The two spikes in the red curve after 1400 s and 6500 s appear after refreshing the electrolyte. We tentatively attribute their presence to a small fraction of oxygen 18 O (natural abundance: 0.2%) in the form of 16 O- 18 O molecules (m = 34 g/mol) that are dissolved in the refreshed electrolyte. The electrolyte is degassed within a minute or so, after which the spikes disappear.…”

Section: Electrocatalytic Performancementioning

confidence: 93%

Structural Transformation Identification of Sputtered Amorphous MoS_x as an Efficient Hydrogen-Evolving Catalyst during Electrochemical Activation

Bogdanoff

Harbauer

et al. 2019

ACS Catal.

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Molybdenum sulfide MoS x is considered as attractive hydrogen evolution catalyst since it is free of noble metals and shows a low overvoltage. Especially, amorphous molybdenum sulfide has attracted attention because of its high catalytic activity. However, the catalytic mechanism of the hydrogen evolution reaction is not yet fully understood. Therefore in our study, layers of MoS x were deposited by reactive magnetron sputtering varying the substrate temperature in the range from room temperature (RT) to 500°C. The morphology and structure of the films change significantly as a function of temperature, from an amorphous to a highly textured 2H-MoS 2 phase. The highest catalytic activity was found for amorphous layers deposited at RT showing an overvoltage of 180 mV at a current density of-10 mAcm-2 in a 0.5 M sulfuric acid electrolyte (pH 0.3) after electrochemical activation. As detected by Raman spectroscopy the RT deposited catalyst consists of [Mo 3 S 13 ] 2and [Mo 3 S 12 ] 2entities which are interconnected via [S 2 ] 2and S 2ligands. When sweeping the potential from 0.2 to-0.3 V vs RHE a massive release of sulfur in form of gaseous H 2 S was observed in the first minutes as detected by differential electrochemical mass spectroscopy (DEMS). After electrochemical cycling for 10 min, the chains of these clusters transform into a layer-type MoS 2-x phase. In this transformation process, H 2 S formation gradually vanishes and H 2 evolution becomes dominant. The new phase is considered as a sulfur deficient molybdenum sulfide characterized by a high number of molybdenum atoms located at the edges of nano-sized MoS x islands, which act as catalytically active centers.

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“…By contrast, the MoS 2 (008) reflection was visible in both the unmodified and Ag+Pd/VA‐MoS 2 samples, indicating that these electrodes had similar crystallinity. Although MoS 2 with lower crystallinity could lead to a higher density of active sites, it also simultaneously leads to poor conductivity; the latter would significantly impact performance of the electrodes in this study owing to their thickness. The alternative explanation, that the Pd/VA‐MoS 2 was preferentially oriented in a different direction, thus explaining the absence of the MoS 2 (008) peak.…”

Section: Resultsmentioning

confidence: 98%

Catalytic Hydrogen Evolution Reaction Enhancement on Vertically Aligned MoS₂ by Synergistic Addition of Silver and Palladium

et al. 2020

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Hybrid electrodes containing MoS2 with metals active for the hydrogen evolution reaction (HER) are highly desirable as they can provide a cost‐effective and active route for producing hydrogen. It is well known that the technique used to facilitate such hybrid formation plays a critical role in the activity and stability of the electrode. Here we utilized a novel method for hybridization based on electron‐beam deposition of Ag, Pd, and Mo to make precursor films which, upon sulfurization, formed hybrid electrodes based on vertically aligned molybdenum disulfide (VA‐MoS2). We further modified the surface of these electrodes by exploiting galvanic replacement of palladium. Surprisingly, both hybridization techniques showed a synergistic effect between Pd and Ag, and enhanced activity was enabled by the presence of both metals. XPS, XRD, Raman spectroscopy, and FIB‐EM were used to explore the root cause of the synergy. It appears that enhanced performance is based partially on the mutual solubility of Pd−Ag and the facile diffusion of Ag through the MoS2 film. Ag/VA‐MoS2 modified by galvanic replacement provided 10 mA/cm2 at 210 mV of overpotential and was stable for up to 4000 cycles, surpassing the stability of previously reported Pd/MoS2 hybrids, making these techniques of interest for future generations of hybrid HER electrodes based on MoS2.

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Mapping the electrocatalytic activity of MoS₂ across its amorphous to crystalline transition

Abstract: A systematic mapping of the electrocatalytic activity of MoS2 across a structural transformation allows for correlation of structure to function.

Cited by 47 publications

References 68 publications

Controllable Synthesis of Nanosized Amorphous MoS_x Using Temporally Shaped Femtosecond Laser for Highly Efficient Electrochemical Hydrogen Production

Controllable Synthesis of Nanosized Amorphous MoS_x Using Temporally Shaped Femtosecond Laser for Highly Efficient Electrochemical Hydrogen Production

Structural Transformation Identification of Sputtered Amorphous MoS_x as an Efficient Hydrogen-Evolving Catalyst during Electrochemical Activation

Catalytic Hydrogen Evolution Reaction Enhancement on Vertically Aligned MoS₂ by Synergistic Addition of Silver and Palladium

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Mapping the electrocatalytic activity of MoS2 across its amorphous to crystalline transition

Abstract: A systematic mapping of the electrocatalytic activity of MoS2 across a structural transformation allows for correlation of structure to function.

Cited by 47 publications

References 68 publications

Controllable Synthesis of Nanosized Amorphous MoSx Using Temporally Shaped Femtosecond Laser for Highly Efficient Electrochemical Hydrogen Production

Controllable Synthesis of Nanosized Amorphous MoSx Using Temporally Shaped Femtosecond Laser for Highly Efficient Electrochemical Hydrogen Production

Structural Transformation Identification of Sputtered Amorphous MoSx as an Efficient Hydrogen-Evolving Catalyst during Electrochemical Activation

Catalytic Hydrogen Evolution Reaction Enhancement on Vertically Aligned MoS2 by Synergistic Addition of Silver and Palladium

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Mapping the electrocatalytic activity of MoS₂ across its amorphous to crystalline transition

Controllable Synthesis of Nanosized Amorphous MoS_x Using Temporally Shaped Femtosecond Laser for Highly Efficient Electrochemical Hydrogen Production

Controllable Synthesis of Nanosized Amorphous MoS_x Using Temporally Shaped Femtosecond Laser for Highly Efficient Electrochemical Hydrogen Production

Structural Transformation Identification of Sputtered Amorphous MoS_x as an Efficient Hydrogen-Evolving Catalyst during Electrochemical Activation

Catalytic Hydrogen Evolution Reaction Enhancement on Vertically Aligned MoS₂ by Synergistic Addition of Silver and Palladium