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This content will become publicly available on December 1, 2023

Title: Dual-phase MoS2/MXene/CNT ternary nanohybrids for efficient electrocatalytic hydrogen evolution
Abstract Two-dimensional (2D) molybdenum disulfide (MoS 2 ) has been recognized as a potential substitution of platinum (Pt) for electrochemical hydrogen evolution reaction (HER). However, the broad adoption of MoS 2 is hindered by its limited number of active sites and low inherent electrical conductivity. In this work, we employed a one-step solvothermal synthesis technique to construct a ternary hybrid structure consisting of dual-phase MoS 2, titanium carbide (Ti 3 C 2 ) MXene, and carbon nanotubes (CNTs), and demonstrated synergistic effects for active site exposure, surface area enlargement, and electrical conductivity improvement of the catalyst. The dual-phase MoS 2 (DP-MoS 2 ) is directly formed on the MXene with CNTs acting as crosslinks between 2D islands. The existence of edge-enriched metallic phase MoS 2 , the conductive backbone of MXene along with the crosslink function of CNTs clearly improves the overall HER performance of the ternary nanocomposite. Moreover, the integration of MoS 2 with MXene not only increases the interlayer distance of the 2D layers but also partially suppresses the MXene oxidation and the 2D layer restacking, leading to good catalytic stability. As a result, an overpotential of 169 mV and a low Tafel slope of 51 mV/dec was successfully achieved. more » This work paves a way for 2D-based electrocatalyst engineering and sheds light on the development of the next-generation noble metal-free HER electrocatalysts. « less
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npj 2D Materials and Applications
Sponsoring Org:
National Science Foundation
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  1. Abstract

    Crystal phase control still remains a challenge for the precise synthesis of 2D layered metal dichalcogenide (LMD) materials. The T′ phase structure has profound influences on enhancing electrical conductivity, increasing active sites, and improving intrinsic catalytic activity, which are urgently needed for enhancing hydrogen evolution reaction (HER) activity. Theoretical calculations suggest that metastable T′ phase 2D Sn1−xWxS2alloys can be formed by combining W with 1T tin disulfide (SnS2) as a template to achieve a semiconductor‐to‐metallic transition. Herein, 2D Sn1−xWxS2alloys with varyingxare prepared by adjusting the molar ratio of reactants via hydrothermal synthesis, among which Sn0.3W0.7S2displays a maximum of concentration of 81% in the metallic phase and features a distorted octahedral‐coordinated metastable 1T′ phase structure. The obtained 1T′‐Sn0.3W0.7S2has high intrinsic electrical conductivity, lattice distortion, and defects, showing a prominently improved HER catalytic performance. Metallic Sn0.3W0.7S2coupled with carbon black exhibits at least a 215‐fold improvement compared to pristine SnS2. It has excellent long‐term durability and HER activity. This work reveals a general phase transition strategy by using T phase materials as templates and merging heteroatoms to achieve synthetic metastable phase 2D LMDs that have a significantly improved HER catalytic performance.

  2. Abstract

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  3. Abstract

    The development of non‐noble metal materials for efficient hydrogen evolution reaction (HER) in wide pH range is still a challenge at present. Herein, a predesigned polyoxometalate (POM)‐based metal–organic polymer {L3Co2 · 6H2O}[H3GeMo12O40] · 9H2O (L = 1,2,4‐triazole) is employed as bimetallic source together with thiourea converting to CoS2@MoS2on carbon cloth (CC) (abbreviated to CoS2@MoS2@CC) for the first time. Impressively, the CoS2@MoS2in the form of vertically interconnected nanoarrays with multiple interfaces are grown in situ on CC and act as electrodes directly for HER. The CoS2@MoS2@CC‐30h composite exhibits superb activity and long‐durability in both acidic and alkaline media. Low overpotential is achieved in 0.5mH2SO4(65 mV) and 1.0mKOH (87 mV) for 10 mA cm−2versus RHE, which overmatch major MoS2‐/POM‐based electrocatalysts. This work therefore may shed substantial lights on designing active and durable molybdenum‐based bi‐/polymetallic sulfide from variable POM‐based metal–organic polymers for electrocatalytic hydrogen evolution reaction in wide pH range.

  4. Molybdenum sulfide (MoS2) has emerged as a promising electrocatalyst for hydrogen evolution reaction (HER) owing to its high activity and stability during the reaction. However, the efficiency of hydrogen production is limited by the number of active sites in MoS2. In this work, a simple method of fabricating polycrystalline multilayer MoS2on Mo foil for efficient hydrogen evolution is demonstrated by controlling the sulfur (S) vacancy concentration, which can introduce new bands and lower the hydrogen adsorption free energy (ΔGH). For the first time, theoretical and experimental results show that the HER performance of synthesized MoS2with S vacancy can be further enhanced by the very small amount of platinum (Pt) decoration, which can introduce new gap states and more catalytic sites in real space with suitable free energy. The fabricated hybrid electrocatalyst exhibits significantly smaller Tafel slope of 38 mV dec−1and better HER electrocatalytic activity compared to previous works. This approach provides a simple pathway to design low‐cost, efficient and sizable hydrogen‐evolving electrode by simultaneously tuning the MoS2band structure and active sites.

  5. Abstract

    Nickel sulfide (Ni3S2) is a promising hydrogen evolution reaction (HER) catalyst by virtue of its metallic electrical conductivity and excellent stability in alkaline medium. However, the reported catalytic activities for Ni3S2are still relatively low. Herein, an effective strategy to boost the H adsorption capability and HER performance of Ni3S2through nitrogen (N) doping is demonstrated. N‐doped Ni3S2nanosheets achieve a fairly low overpotential of 155 mV at 10 mA cm−2and an excellent exchange current density of 0.42 mA cm−2in 1.0mKOH electrolyte. The mass activity of 16.9 mA mg−1and turnover frequency of 2.4 s−1obtained at 155 mV are significantly higher than the values reported for other Ni3S2‐based HER catalysts, and comparable to the performance of best HER catalysts in alkaline medium. These experimental data together with theoretical analysis suggest that the outstanding catalytic activity of N‐doped Ni3S2is due to the enriched active sites with favorable H adsorption free energy. The activity in the Ni3S2is highly correlated with the coordination number of the surface S atoms and the charge depletion of neighbor Ni atoms. These new findings provide important guidance for future experimental design and synthesis of optimal HER catalysts.