Hydrogen Evolution Reaction Activity Of MoS2 Research Articles

Recent progress of molybdenum disulfide/carbon composites for electrochemical hydrogen evolution reaction

As a star two-dimensional material, molybdenum disulfide (MoS2) shows a good potential in the field of electrochemical hydrogen evolution reaction (HER) due to its low price, special physicochemical properties and a small theoretical Gibbs free energy of hydrogen adsorption. However, some disadvantages such as poor electroconductivity and inert basal planes hinder its further improvement of HER activity. Therefore, adopting carbon materials with good electrical conductivity and large specific surface area to composite with MoS2 is one of the popular strategies to improve the electrical conductivity and increase the exposure of catalytically active sites for constructing highly efficient MoS2-based electrocatalysts. Herein, in this review, we firstly gave a brief introduction of the MoS2 structure and the basic HER principle. Then, the synthesis method, catalytic performance and reaction mechanism of utilizing different carbon materials to improve the HER activity of MoS2 were summarized in detail. Finally, the existing problems and future opportunities for preparing highly active and low cost electrocatalysts assisted by carbon materials are prospected.

Ultralight porous carbon loaded Co-doped MoS2 as an efficient electrocatalyst for hydrogen evolution reaction in acidic and alkaline media

Molybdenum disulfide (MoS2) has a Gibbs free energy comparable to platinum (Pt), suggesting it can replace Pt as a hydrogen evolution reaction (HER) catalyst. However, the shortcomings of the restricted number of MoS2 active sites and poor intrinsic electrical conductivity have resulted in impeding its widespread application. In this work, Co/MoS2@NPC electrocatalyst was prepared by using nitrogen-doped porous carbon (NPC) as a substrate material, and then hydrothermally anchoring cobalt-doped molybdenum disulfide (Co-doped MoS2) on the substrate. Co/MoS2@NPC was subsequently applied to hydrogen evolution reaction in acidic and alkaline media. It was found that the overpotential of 0.2Co/MoS2@NPC was only 139 mV for HER at 10 mA cm−2 with a Tafel slope of 69 mV dec−1 in acidic medium; while in alkaline medium, its overpotential was 163 mV with a Tafel slope of 106 mV dec−1, and it operated stably over 10 h. The superior HER performance may be related to the point that NPC as a substrate can uniformly disperse MoS2, exposing more active sites and ensuring high electronic conductivity of MoS2. In addition, the introduction of Co into MoS2 changed the intrinsic activity of MoS2 and interacted with CoSx and pyridine nitrogen in NPC, constituting a ternary catalytic interaction. Therefore, this study provides a novel strategy for optimizing the HER activity of MoS2.

Confined Growth of MoS2 by using a Two‐Dimensional Metal‐Organic Framework for Efficient Hydrogen Evolution

AbstractMolybdenum disulfide (MoS2) is a promising electrocatalyst for hydrogen evolution reaction (HER). However, the exposed active edge sites of MoS2 are limited due to its intrinsic stacking property. Herein, a highly exposed MoS2 hybrid electrocatalyst is prepared by a confined strategy of the pores of a 2D metal‐organic framework (MOF). A low overpotential of 76 mV at 10 mA cm−2 and a Tafel slope of 73 mV dec−1 are achieved, which indicated greater efficiency than pristine MoS2. The denotative growth of MoS2 from the internal pore of 2D MOF on the surface effectively prevents its stacking and exposes much more active edge sites. Experimental results show that parts of Co are incorporated into MoS2, producing strong electronic interaction between Co and Mo atoms and accounting for the excellent HER activity of MoS2. This work demonstrates a confined strategy to prepare nanomaterials with highly exposed edge sites and enhanced intrinsic activity.

The charge effects on the hydrogen evolution reaction activity of the defected monolayer MoS2.

Doping engineering has proven to be an effective way to tune the hydrogen evolution reaction (HER) activity of MoS2. Introducing these defects could cause the overall charge imbalance of MoS2, which makes MoS2 charged. In order to understand the effect of charge on the HER activity of the defected MoS2, we systematically investigate the formation energies, hydrogen adsorption Gibbs free energy (), and electronic structures of 3d, 4d, and 5d transition metal (TM) doped monolayer MoS2 with S vacancies (Svac) based on the density functional theory (DFT) calculations. According to the formation energy calculation, Svac in the 0 and -1 charge states (S0vac and Svac1-) is found to be stable. of Svac1- is -0.16 eV, suggesting its HER catalytic activity is lower than that of Pt (), which is consistent with the experimental results. By substituting the Mo atom with TM atoms, we found that the TM atoms in groups VB-VIIB can promote the generation of Svac, forming defect complexes (TMMoSvac). is greatly affected by the charge state of defects; TMMoSvac defects (TM = V, Nb, Ta, Cr, W, Mn, and Re) in -1 charge states exhibited excellent HER activity (). Significantly, W and Re doping can promote the HER activity of MoS2 independent of the charge state and the Fermi level, which suggests that W and Re doping are most beneficial to improve the HER activity of MoS2. Therefore, the HER activity of defected MoS2 is not only influenced by as previously thought, but also by formation energies, charge state and Fermi level position of defects. The underlying physics could be deduced from the charge-induced changes in electronic structures. Our work highlights the defect charge effects on the electrochemical reactions and offers plausible mechanisms of defect charge effects.

Orbital Modulation with P Doping Improves Acid and Alkaline Hydrogen Evolution Reaction of MoS2

There has been great interest in developing and designing economical, stable and highly active electrocatalysts for the hydrogen evolution reaction (HER) via water splitting in an aqueous solution at different pH values. Transition-metal dichalcogenides (TMDCs), e.g., MoS2, are identified to be promising catalysts for the HER due to the limited active sites at their edges, while the large basal plane of MoS2 is inert and shows poor performance in electrocatalytic hydrogen production. We theoretically propose orbital modulation to improve the HER performance of the basal plane of MoS2 through non-metal P doping. The substitutional doping of P provides empty 3pz orbitals, perpendicular to the basal plane, can enhance the hydrogen adsorption for acid HER and can promote water dissociation for alkaline HER, which creates significant active sites and enhances the electronic conductivity as well. In addition, 3P-doped MoS2 exhibits excellent HER catalytic activity with ideal free energy at acid media and low reaction-barrier energy in alkaline media. Thus, the doping of P could significantly boost the HER activity of MoS2 in such conditions. Our study suggests an effective strategy to tune HER catalytic activity of MoS2 through orbital engineering, which should also be feasible for other TMDC-based electrocatalysts.

Observation of H2 Evolution and Electrolyte Diffusion on MoS2 Monolayer by In Situ Liquid-Phase Transmission Electron Microscopy.

Unit-cell-thick MoS2 is a promising electrocatalyst for the hydrogen evolution reaction (HER) owing to its tunable catalytic activity, which is determined based on the energetics and molecular interactions of different types of HER active sites. Kinetic responses of MoS2 active sites, including the reaction onset, diffusion of the electrolyte and H2 bubbles, and continuation of these processes, are important factors affecting the catalytic activity of MoS2 . Investigating these factors requires a direct real-time analysis of the HER occurring on spatially independent active sites. Herein, the H2 evolution and electrolyte diffusion on the surface of MoS2 are observed in real time by in situ electrochemical liquid-phase transmission electron microscopy (LPTEM). Time-dependent LPTEM observations reveal that different types of active sites are sequentially activated under the same conditions. Furthermore, the electrolyte flow to these sites is influenced by the reduction potential and site geometry, which affects the bubble detachment and overall HER activity of MoS2 .

Cover Feature: Surface and Interface Engineering Strategies for MoS2 Towards Electrochemical Hydrogen Evolution (Chem. Asian J. 14/2022)

High-efficiency electrocatalysts are critical to promote the hydrogen evolution reaction (HER) through electrolysis of water. MoS2 has received great attention as potential electrocatalysts for HER. Surface engineering and interface engineering are effective strategies to enhance HER activity of MoS2. In this Review, the modification strategies used in recent years to improve the HER activity of MoS2 through surface and interface engineering are summarized. Particularly, the aspects including defects, doping, strain, atomic control and heterostructure are highlighted. More information can be found in the Review by Le Yu et al.

Tuning the Intrinsic Activity and Electrochemical Surface Area of MoS2 via Tiny Zn Doping: Toward an Efficient Hydrogen Evolution Reaction (HER) Catalyst.

Molybdenum sulfide (MoS2 ) is considered as an alternative material for commercial platinum catalysts for electrocatalytic hydrogen evolution reaction (HER). Improving the apparent HER activity of MoS2 to a level comparable to that of Pt is an essential premise for the commercial use of MoS2 . In this work, a Zn-doping strategy is proposed to enhance the HER performance of MoS2 . It is shown that tiny Zn doping into MoS2 leads to the enhancement of the electrochemical surface area, increases in proportion of HER active 1T phase in the material and formation of catalytic sites of higher intrinsic activity. These benefits result in a high-performance HER electrocatalyst with a low overpotential of 190 mV(@10 mA cm-2 ) and a low Tafel slope of 58 mV dec-1 . The origin for the excellent electrochemical performance of the doped MoS2 is rationalized with both experimental and theoretical investigations.

Continuously tuning the hydrogen evolution activity of MoS2 through sodium ions insertion

Though enormous attention has been paid to MoS2 in the field of electrocatalytic hydrogen evolution reaction (HER), the conventional 2H MoS2 is hardly regarded as an alternative to noble Pt due to the limited number of active sites and semiconducting character. Herein, sodium ions were intentionally introduced into the MoS2 to regulate its structure and thus HER activity. We found that the HER activity of MoS2 would gradually increase at the intercalation stage and further increase at the early stage of conversion reaction. Based on various characterization techniques, the possible structure-performance relationship was established. The first increase in activity was ascribed to interlayer expansion and phase transformation, and the second increase in activity was mainly ascribed to increase of active sites due to the fragmentation of MoS2 after triggering conversion reaction. Even though deep discharging MoS2 to 0.01 V (vs. Na+/Na) would slightly impair HER activity, such an activity was still much better than that of pristine MoS2, which might be originated from the doping of S into molybdenum oxide according to the DFT calculation.

Crystalline MoP-amorphous MoS2 hybrid for superior hydrogen evolution reaction

Molybdenum disulfide (MoS2) is regarded as a perfect catalyst for electrochemical hydrogen evolution reaction (HER). However, the active sites are usually concealed due to the unique two dimensional structure of MoS2. Herein, we propose a facile surface engineering modus to improve the HER activity of MoS2. This strategy is demonstrated by in-situ growth of amorphous MoS2 layer on the molybdenum phosphide (MoP) nanoparticles anchored on the carbon nanotubes (MoS2/MoP/CNT). The HER activity is significantly promoted both through the defect engineering of amorphous MoS2 and the synergistic effect between the MoS2 and MoP phases. The MoS2/MoP/CNT sample presents significantly higher HER performance than the pure phase of MoP/CNT and MoS2/CNT samples, requiring overpotentials of 73 and 141 ​mV to drive a current density of 10 and 100 ​mA ​cm-2.

The electrochemical overall water splitting promoted by MoS2 in coupled nickel–iron (oxy)hydride/molybdenum sulfide/graphene composite

Developing cost-effective methodologies for fabricating efficient bifunctional electrocatalysts is pivotal to boost electrochemical water splitting. Herein, we report an integrated composite, which is composed of NiFeOx(OH)y nanoparticles and vertically-oriented MoS2 nanosheets on reduced graphene oxide (rGO) matrix (NiFeOx(OH)y@MoS2/rGO), for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). It has been deduced that MoS2 is oxidized during OER, and the oxidized Mo species modulate the electronic structure of NiFeOx(OH)y to facilitate chemisorption of the oxygen species in OER. Meanwhile, NiFeOx(OH)y speeds up sluggish water dissociation in HER, and thus significantly improving HER activity of MoS2 in alkaline electrolyte. The integrated composite shows high electrocatalytic activity and superior durability for HER and OER with low overpotentials of 170 mV at 10 mA cm−2 and 250 mV at 20 mA cm−2, respectively. This work provides new approaches to develop electrocatalysts for overall water splitting and other applications.

Heterostructured MoS2@Bi2Se3 nanoflowers: A highly efficient electrocatalyst for hydrogen evolution

The transition metal dichalcogenide MoS2 shows good catalytic properties for the hydrogen evolution reaction (HER). However, the HER activity of 2D MoS2 is limited by its poor electrical conductivity. Bi2Se3 nanosheets are topological insulators possessing metallic surface states, thereby displaying unconventional electron dynamics and excellent conductivity. Therefore, combining Bi2Se3 nanosheets and with MoS2 nanosheets represents a rational approach for improving the HER activity of MoS2. In this work, Bi2Se3 nanoflowers were first synthesized via a hot injection method, followed by the slow growth of MoS2 nanosheets on their surface to form heterostructured MoS2@Bi2Se3 nanoflowers. Compared to pristine Bi2Se3 and MoS2, the MoS2@Bi2Se3 nanoflowers exhibited outstanding HER activity in acidic media with an onset overpotential of 134 mV, an overpotential of 208 mV at 10 mA/cm2, a Tafel slope of 57 mV/dec and remarkable stability. The enhanced HER catalytic activity offered by the MoS2@Bi2Se3 nanoflowers is attributed excellent electron transfer from Bi2Se3 to MoS2, as well as the abundance of edge-rich MoS2 nanosheets vertically aligned on the Bi2Se3 support that act as H2 evolution sites.

Awakening Solar Hydrogen Evolution of MoS2 in Alkalescent Electrolyte through Doping with Co.

Transition metal dichalcogenides, especially MoS2 , have been regarded as promising cocatalysts for the hydrogen evolution reaction (HER) because of a near-zero Gibbs free energy for H+ absorption. However, the HER activity of MoS2 is profoundly restricted by acidic media. Co-doped MoS2 (Co-MoS2 ) nanosheets are found to enable the highly efficient solar H2 evolution of CdS nanowires (NWs) in alkalescent electrolyte. The content of Co in MoS2 is optimized to 2.8 % and the Co-MoS2 content in Co-MoS2 /CdS NWs hybrids is 2.5 wt %; the optimized Co-MoS2 /CdS NWs shows a high H2 evolution rate of 14.22 mmol g-1 h-1 and 71 % apparent quantum efficiency in the Na2 SO3 electrolyte. Moreover, the H2 generation enabled by the Co-MoS2 cocatalyst can exhibit universality in alkalescent electrolytes, such as triethanolamine (TEA) and disodium ethylenediaminetetraacetic acid (EDTA), exhibiting greater photocatalytic H2 generation than Pt/CdS. The design of Co-MoS2 /CdS sheds light on the development of highly efficient low-cost photocatalysts for solar H2 generation from water reduction.

MoS2/NiS2 Composites for Efficient Hydrogen Evolution Both in Acidic and Alkaline Media

The growing concern about global warming, environmental pollution and energy security has raised the demand for clean energy resources in place of fossil fuel. Cost-efficient generation of hydrogen from water-splitting through electrocatalysis holds tremendous promise for clean energy (1, 2). Central to the electrocatalysis are efficient and robust electrocatalysts composed of earth-abundant elements, which are urgently needed for realizing low-cost and high-performance energy conversion devices. Transition metal compounds (TMCs) are a group of attractive noble-metal-free electrocatalysts for the hydrogen evolution reaction (HER). Earth-abundant MoS2 has emerged as a promising hydrogen evolution reaction (HER) catalyst with high activity and durability, but it is kinetically retarded in alkaline media . Extensive efforts have been devoted to improving the HER activity of MoS2 in acid (3), but little attention has been paid to simultaneously enhancing its HER performance both in acid and base. This work demonstrates a dramatic enhancement of HER kinetics both in acidic and alkaline media by hybridizing vertical MoS2 with another earth-abundant material, nickel disulfide (NiS2). Field-emission SEM image shows that the MoS2/NiS2 composite is composed of a film-like structure of NiS2 cover on the edge surfaces of the MoS2 sheets (Figure 1a). As shown in Figure 1b, the XRD peaks observed at 2θ=14.1°, 32.9° and 58.8° of the MoS2/NiS2 sample can be indexed to 2H-MoS2 crystal (JCPDS No. 75-1539), and peaks at 2θ=31.4°, 45.1° and 53.4° indexed to (200), (220) and (311) facets of the NiS2, respectively (JCPDS No. 88-1709). The synthesized MoS2/NiS2 composite exhibits a much lower HER overpotential both in acidic and alkaline media than that of bare MoS2 and NiS2 catalysts (Figure 1c and d). Figure caption Figure 1. (a) FESEM image of the MoS2/NiS2 composite. (b) XRD patterns of the NiS2 and MoS2/NiS2 samples, together with the standard pattern of 2H MoS2 (JCPDS 75-1539) and NiS2 (JCPDS 88-1709). (c) Polarization curves of bare MoS2, NiS2 and MoS2/NiS2 composite catalysts in 0.5 M H2SO4 solution at a scan rate of 5 mV/s. (d) Polarization curves of bare MoS2, NiS2 and MoS2/NiS2 composite catalysts in 1 M KOH solution at a scan rate of 5 mV/s. References D. Strmcnik et al., Improving the hydrogen oxidation reaction rate by promotion of hydroxyl adsorption. Nat. Chem. 5, 300-306 (2013).Y. Jiao, Y. Zheng, M. T. Jaroniec, S. Z. Qiao, Design of electrocatalysts for oxygen- and hydrogen-involving energy conversion reactions. Chem. Soc. Rev. 44, 2060-2086 (2015).J. Hu et al., Engineering stepped edge surface structures of MoS2 sheet stacks to accelerate the hydrogen evolution reaction. Energy Environ. Sci. 10, 593-603 (2017). Figure 1

P,Se‐Codoped MoS2 Nanosheets as Accelerated Electrocatalysts for Hydrogen Evolution

AbstractAs the half reaction of water splitting, hydrogen evolution reaction (HER) is a prospective way to generate clean fuel of hydrogen. Molybdenum disulfide (MoS2), as a member of the transition‐metal dichalcogenides, has attracted much research attention since its potential HER activity is predicted to be even comparable to Pt. However, the HER activity of MoS2 is still far from desirable, owing to the high resistance and limited intrinsic active sites. Herein, we have successfully engineered MoS2 by doping P and Se to regulate the electron density. The optimized P,Se‐MoS2/CNTs exhibit a low overpotential of 110 mV at 10 mA cm−2 and a small Tafel slope of 49 mV dec−1, much better than P‐MoS2/CNTs, Se‐MoS2/CNTs, MoS2/CNTs, and closing to commercial Pt/C. The P,Se‐MoS2/CNTs also display excellent electrochemical stability over 15 days. Raman, XPS and surface valence band spectra confirm that P and Se codoping modulate the electron densities of the catalytic sites, which can largely improve the HER activity.

Synthesis of flower-like MoSe2@MoS2 nanocomposites as the high efficient water splitting electrocatalyst

Here we report a highly active catalyst for hydrogen evolution reaction (HER) that is constructed by in situ growth of MoS2 on the surface of MoSe2 nanosheets (MoSe2@MoS2). Compared with either single MoS2 or MoSe2, the MoSe2@MoS2 electrocatalyst exhibits better electrocatalytic activity with a small Tafel slope (60 mV dec−1) and a low onset overpotential (−161 mV). The good HER activity is attributed to its core-shell nanostructure, which can not only efficaciously suppress the aggregation of MoS2 nanosheets, but also generate more active sites and produce a synergistic effect of the two components in the HER. This approach provides an effective pathway to improve HER activity of MoS2 or MoSe2 catalysts and can be used for other two-dimensional semiconductor electrocatalyst.

Flower-like CoS2/MoS2 nanocomposite with enhanced electrocatalytic activity for hydrogen evolution reaction

Molybdenum sulfide (MoS2) has received tremendous attracts for its promising performance in the aspects of hydrogen evolution reaction (HER). To improve the HER activity of MoS2, we designed a flower-shaped CoS2/MoS2 nanocomposite with enhanced HER electroactivity compared with MoS2 nanosheets by a simple one-step hydrothermal method. The facile approach brings about distinct transformation of the morphology from nanosheets to nanoflower structures. The introduction of Co element into MoS2 results in the larger active surface area, more edge-terminated structures, and higher conductivity of the CoS2/MoS2 nanocomposite, which are good for improving the HER electroactivity. In brief, the optimized catalyst exhibits the low overpotential of 154 mV at 10 mA cm−2, small Tafel slope of 61 mV dec−1, and excellent stability in acidic solution.

Enhanced electrocatalytic hydrogen evolution performance of MoS2 ultrathin nanosheets via Sn doping

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) have drawn much attention due to their unique physical and chemical properties. Molybdenum disulfide (MoS2) is particularly promising in hydrogen evolution reaction (HER) as a substitute for noble-metal catalysts. Although numerous attempts have been made to improve the HER activity of MoS2, engineering the MoS2-based electrocatalysts with activities similar to noble-metal catalysts remains challenging. Herein, we synthesize high-quality tin doped molybdenum disulfide (Sn-MoS2) ultrathin nanosheets by a g-C3N4 sacrificial template assisted thermolytic approach, and detailly investigate the role of Sn doping on the HER activity. The porous Sn-MoS2 nanosheets displays superior HER performance, exhibiting an overpotential of 28mV at 10mAcm−2 and a Tafel slope of 37.2mVdec−1 with an admirable stability. Compared to pristine MoS2 nanosheets, the significantly improved catalytic activity is ascribed to the increased active edge sites, enhanced intrinsic catalytic activity for each active site as well as accelerated electron transfer upon Sn doping. This work may provide guidelines for the design and synthesis of efficient non-precious HER catalysts.

Molybdenum sulfides—efficient and viable materials for electro - and photoelectrocatalytic hydrogen evolution

This perspective covers the use of molybdenum disulfide and related compounds, generally termed MoSx, as electro- or photoelectrocatalysts for the hydrogen evolution reaction (HER). State of the art solutions as well as the most illustrative results from the extensive electro- and photoelectrocatalytic literature are given. The research strategies currently employed in the field are outlined and future challenges pointed out. We suggest that the key to optimising the HER activity of MoS2 is divided into (1) increasing the catalytic activity of the active site, (2) increasing the number of active sites of the catalyst, and (3) improving the electrical contact to these sites. These postulations are substantiated by examples from the existing literature and some new results. To demonstrate the electrocatalytic properties of a highly conductive MoS2 hybrid material, we present the HER activity data for multi-wall MoS2 nanotubes on multi-wall carbon nanotubes (MWMoS2@MWCNTs). This exemplifies the typical data collected for the electrochemical HER. In addition, it demonstrates that the origin of the activity is closely related to the amount of edges in the layered MoS2. The photoelectrocatalytic HER is also discussed, based on examples from literature, with an emphasis on the use of MoSx as either (1) the co-catalyst providing the HER activity for a semiconductor, e.g. Mo3S+4on Si or (2) MoS2 as the semiconductor with an intrinsic HER activity. Finally, suggestions for future catalyst designs are given.