Doped MoS2 Research Articles

Is the doped MoS2 basal plane an efficient hydrogen evolution catalyst? Calculations of voltage-dependent activation energy.

Transition metal dichalcogenides are cheap and earth-abundant candidates for the replacement of precious metals as catalyst materials. Experimental measurements of the hydrogen evolution reaction (HER), for example, have demonstrated significant electrocatalytic activity of MoS2 but there is large variation depending on the preparation method. In order to gain information about the mechanism and active sites for the HER, we have carried out calculations of the reaction and activation energy for HER at the transition metal doped basal plane of MoS2 under electrochemical conditions, i.e. including applied electrode potential and solvent effects. The calculations are based on identifying the relevant saddle points on the energy surface obtained from density functional theory within the generalized gradient approximation, and the information on energetics is used to construct voltage-dependent volcano plots. Doping with 3d-metal atoms as well as Pt is found to enhance hydrogen adsorption onto the basal plane by introducing electronic states within the band gap, and in some cases (Co, Ni, Cu, Pt) significant local symmetry breaking. The Volmer-Heyrovsky mechanism is found to be most likely and the associated energetics show considerable dopant and voltage-dependence. While the binding free energy of hydrogen can be tuned to be seemingly favorable for HER, the calculated activation energy turns out to be significant, at least 0.7 eV at a voltage of -0.5 V vs. SHE, indicating low catalytic activity of the doped basal plane. This suggests that other sites are responsible for the experimental activity, possibly edges or basal plane defects.

Ni and O co-modified MoS2 as universal SERS substrate for the detection of different kinds of substances

Surface-enhanced Raman scattering (SERS) has attracted extensive attention as an ultrasensitive detection method. However, the poor biocompatibility and expensive synthesis cost of noble metal SERS substrates have become non-negligible factors that limit the development of SERS technology. Metal chalcogenide semiconductors as an alternative to noble metal SERS substrates can avoid these disadvantages, but the enhancement effect is lower than that of noble metal substrates. Here, we report a method to co-modify MoS2 by Ni and O, which improves the carrier concentration and mobility of MoS2. The SERS effect of the modified MoS2 is comparable to that of noble metals. We found that the improved SERS performance of MoS2 can be attributed to the following two factors: strong interfacial dipole–dipole interaction and efficient charge transfer effect. During the doping process, the incorporation of Ni and O enhances the polarity and carrier concentration of MoS2, enhances the interfacial interaction of MoS2, and provides a basis for charge transfer. During the annealing process, the introduction of O atoms into the S defects reduces the internal defects of doped MoS2, improves the carrier mobility, and promotes the efficient charge transfer effect of MoS2. The final modified MoS2 as a SERS substrate realizes low-concentration detection of bilirubin, cytochrome C, and trichlorfon. This provides promising guidance for the practical inspection of metal chalcogenide semiconductor substrates.

Computational screening of nonmetal dopants to active MoS2 basal-plane for hydrogen evolution reaction via structural descriptor

Nonmetal doping is an efficient approach to activate inert MoS2 basal plane, which converts MoS2 into an electrocatalyst for the hydrogen evolution reaction (HER). However, the trial-and-error approach through experimental attempt is still a common practice to search for suitable nonmetal dopants. In this work, we employ density functional theory (DFT) and microkinetic model to assess alkaline HER activity of nonmetal-modified MoS2(001), which show strong variation in the degree of activation by single- or double-dopants across nonmetal element series (B, C, N, P, O, S, Se and Te). To assist the screening of nonmetal dopants to active MoS2 basal plane, a structural descriptor-based prediction model is constructed. It demonstrates that the activation effect of nonmetal dopant is achieved through the adjustment of valence electron occupancy of reaction center, which tunes the adsorption energy of atomic hydrogen and hydroxide radical, and accordingly reaction kinetic for alkaline HER. The structural descriptor-based prediction model reproduce the activity trend among non-metallic doped MoS2 from available experimental references. In addition, we screened out MoS2 modified by BTe and BSe double dopants with lower overpotential than reported nonmetal-modified MoS2 systems. This work gives a deep insight into activation mechanism of nonmetal dopant for MoS2, and provides an efficient screening strategy for future catalyst design of transition metal dichalcogenides.

First-Principles Calculations to Investigate the Oxidation Mechanism of Pristine MoS2 and Ti-Doped MoS2

Generally, MoS2 is easily oxidized when exposed to oxygen, and the antioxidation mechanism of MoS2 is still a challenge. Thus, more efforts were made to greatly improve its antioxidation performance. It was reported that the Ti atom doped with MoS2 was treated as the effective method to enhance its antioxidation performance; however, the detailed antioxidation mechanism was not well understood. Superior to experimental methods, the first-principles method could provide deep insight into the atomic information and serve as a useful tool to gain an understanding of the antioxidation mechanisms of the doped MoS2; thus, the antioxidation behavior of the Ti-doped MoS2 was investigated in detail using first-principles calculations. However, an opposing conclusion was obtained from the calculated results compared to the previous experimental results; that is, the incorporation of the Ti atom was not helpful for improving the antioxidation performance of MoS2. The strange phenomenon was well probed and discussed in detail, and understanding the oxidation mechanism of the Ti-doped MoS2 would be helpful for expanding its applications in the ambient atmosphere.

(Invited) Linear and Nonlinear Optical Spectra of Two-Dimensional Materials As Quantum Light Sources

The advancement of Quantum Networks for Secure Long-Range Communication and Quantum Sensing technologies critically depends on materials development. There are stringent requirements for the quantum material properties, such as on demand quantum state generation, detection, and transduction. In this talk, I will review solid-state two-dimensional materials platforms for generating quantum light, including excitons, trions, and polaritons as well as nonlinear optical materials for spontaneous parametric down conversion. I will emphases the role of many-body interactions in low dimensional materials and theoretical challenges for describing linear and nonlinear optical properties of quantum materials [1-5]. Y. V. Zhumagulov, A. Vagov, N. Y. Senkevich, D. R. Gulevich, and V. Perebeinos, "Three-particle states and brightening of intervalley excitons in a doped MoS2 monolayer," Physical Review B 101, 245433 (2020).Y. V. Zhumagulov, A. Vagov, D. R. Gulevich, P. E. Faria Junior, and V. Perebeinos, "Trion induced photoluminescence of a doped MoS2 monolayer," The Journal of Chemical Physics 153, 044132 (2020).Y. V. Zhumagulov, S. Chiavazzo, D. R. Gulevich, V. Perebeinos, I. A. Shelykh, and O. Kyriienko, "Microscopic theory of exciton and trion polaritons in doped monolayers of transition metal dichalcogenides," arXiv:2107.06927 (2021).Y. Zhumagulov, A. Vagov, D. Gulevich, and V. Perebeinos, "Electrostatic control of the trion fine structure in transition metal dichalcogenide monolayers", arXiv:2104.11800 (2021).V. D. Neverov, A. E. Lukyanov, Y. V. Zhumagulov, D. R. Gulevich, Andrey V. Krasavin, A. Vagov, and V. Perebeinos, "Nonlinear spectroscopy of excitonic states in transition metal dichalcogenides," arXiv:2109.11633 (2021).

The effect of doping MoSe2 by clusters of noble metals on its adsorption for NH3

The development of industrial activities is associated with negative impacts on the quality of the environment including emission of hazardous gases. Therefore, it is critical to produce sensitive and selective gas detectors in order to monitor and maintain its good quality. This work investigates the effect of noble metal doping of MoSe2 on its adsorption of ammonia (NH3) gas. Pristine and noble metal doped MoSe2 structures are examined computationally using density functional theory (DFT). Clusters of timers of each Pt, Au, and Ag along with their combination are utilized for doping. The influence of doping MoSe2 structure on its adsorption energy and distance of NH3 gas, density of states (DOS), charge transfer between NH3 and the MoSe2 structures, and band structure is explored. When compared to the pristine structure, the doped MoSe2 structures reveal significant changes in electronic characteristics that are reflected on the DOS and band structures. New energy bands have evolved near to the Fermi level because of modifying the MoSe2 structure. The adsorption capacity of the doped structures is greatly enhanced due to incorporation of noble metals. Herein, the magnitude of adsorption energy increases and the adsorption distance deceases for NH3 gas. Consequently, the sensitivity is improved in comparison to the pristine structure. This study shows that noble metal doping of MoSe2 by clusters of trimers can be a useful approach for developing sensitive NH3 gas detectors.

In situ synthesis of Co-doped MoS2 nanosheet for enhanced mimicking peroxidase activity.

To enhance the catalytic activity of two-dimensional layered materials as versatile materials, the modification of transition metal dichalcogenide nanosheets such as MoS2 by doping with heteroatoms has drawn great interests. However, few reports are available on the study of the enzyme-like activity of doped MoS2. In this study, a facile in situ hydrothermal method for the preparation of various ultrathin transition metals (Fe, Cu, Co, Mn, and Ni) doped MoS2 nanosheets has been reported. Through the density functional theory (DFT) and steady-state kinetic analysis, the Co-doped MoS2 nanosheets exhibited the highest peroxidase-like catalytic activity among them. Furthermore, a typical colorimetric assay for H2O2 was presented based on the catalytic oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to a blue product (oxTMB) by Co-MoS2. The proposed colorimetric method showed excellent tolerance under extreme conditions and a broad linear range from 0.0005 to 25 mM for H2O2 determination. Concerning the practical application, in situ detection of H2O2 generated from SiHa cells was also fulfilled, fully confirming the great practicability of the proposed method in biosensing fields.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10853-022-07201-z.

Frenkel-defected monolayer MoS2 catalysts for efficient hydrogen evolution

Defect engineering is an effective strategy to improve the activity of two-dimensional molybdenum disulfide base planes toward electrocatalytic hydrogen evolution reaction. Here, we report a Frenkel-defected monolayer MoS2 catalyst, in which a fraction of Mo atoms in MoS2 spontaneously leave their places in the lattice, creating vacancies and becoming interstitials by lodging in nearby locations. Unique charge distributions are introduced in the MoS2 surface planes, and those interstitial Mo atoms are more conducive to H adsorption, thus greatly promoting the HER activity of monolayer MoS2 base planes. At the current density of 10 mA cm−2, the optimal Frenkel-defected monolayer MoS2 exhibits a lower overpotential (164 mV) than either pristine monolayer MoS2 surface plane (358 mV) or Pt-single-atom doped MoS2 (211 mV). This work provides insights into the structure-property relationship of point-defected MoS2 and highlights the advantages of Frenkel defects in tuning the catalytic performance of MoS2 materials.

First principle insight into co-doped MoS2 for sensing NH3 and CH4

In this work we present the atomistic computational study of the adsorption properties of Co doped MoS2 adsorbed ammonia (NH3) and methane (CH4). The adsorption distance, adsorption energy (Ead), charge transfer (Qt), bandgap, Density of States (DOS), Projected Density of States (PDOS), transport properties, sensitivity and recovery time have been reported. The diffusion property of the system was calculated using Nudge Elastic Band (NEB) method. The calculated results depict that after suitable doping of Co on MoS2 monolayer decreases the resistivity of the system and makes it more suitable for application as a sensor. After adsorbing NH3 and CH4, Co doped MoS2 bandgap, DOS and PDOS become more enhanced. The adsorption energy calculated for NH3 and CH4 adsorbed Co doped MoS2 are -0.9 eV and -1.4 eV. The reaction is exothermic and spontaneous. The I-V curve for Co doped MoS2 for CH4 and NH3 adsorption shows a linear increase in current up to 1.4 V and 2 V, respectively, then a rapid decline in current after increasing a few volts. The Co doped MoS2 based sensor has a better relative resistance state, indicating that it can be employed as a sensor. The sensitivity for CH4 and NH3 were 124 % and 360.5 %, respectively, at 2 V. With a recovery time of 0.01s, the NH3 system is the fastest. In a high-temperature condition/environment, the Co doped MoS2 monolayer has the potential to adsorb NH3 and CH4 gas molecules. According to NEB, CH4 gas molecules on Co doped MoS2 has the lowest energy barrier as compared to NH3 gas molecules. Our results indicate that adsorbing NH3 and CH4 molecules in the interlayer is an effective method for producing Co doped MoS2 monolayers for use as spintronics sensor materials.

Exploring Structural, Electronic, Magnetic, and Optical Properties of Mn Doped Mos2 with and Without Hubbard Correction

Exploring Structural, Electronic, Magnetic, and Optical Properties of Mn Doped Mos2 with and Without Hubbard Correction

Dynamic coordination transformation of active sites in single-atom MoS2 catalysts for boosted oxygen evolution catalysis

Design and synthesis [TMO6] of a doped MoS2 (TMO6@MoS2, TM = Mn, Fe and Co) single-atom catalyst to achieve high OER catalytic activity through an unprecedented dynamic coordination transformation from [TMO6] to [TMO3].

A High-Performance Tfn Membrane Prepared by a Novel Pe Support Layer, a Polydopamine Interlayer, and a Doped Mos2 Quantum Dots@Zno Nanocomposites-Incorporated Polyamide Active Layer

A High-Performance Tfn Membrane Prepared by a Novel Pe Support Layer, a Polydopamine Interlayer, and a Doped Mos2 Quantum Dots@Zno Nanocomposites-Incorporated Polyamide Active Layer

Molecular docking and DFT analyses of magnetic cobalt doped MoS2 and BN nanocomposites for catalytic and antimicrobial explorations

Amongst 2D materials beyond graphene, MoS2 and BN are considered potentially strong candidates for use in numerous ecological technologies such as treatment of polluted water and protection against bacterial infections. With these prospects in mind, nanocomposite was employed in this study as a remedy for problems related to environmental health. Nanocomposites of both host materials (MoS2 and BN) were synthesized via applying liquid-phase exfoliation (LPE) strategy towards their bulk counterparts. In order to enhance its catalytic and antibacterial ability, host materials were doped with cobalt (Co) which serves as transition metal. This dopant was selected due to its band-less and charge facilitation characteristics. A hydrothermal approach was employed to prepare 4 and 8 wt.% concentrations of Co to synthesize doped samples. Several characterization techniques combined with Density Functional Theory (DFT) were engaged for the evaluation of chemical, structural, electrical, morphological, and finally optical features of the synthesized products. The formation of 2H-phase of MoS2 and hexagonal phase of BN was affirmed through XRD pattern; band gap analysis and facilitation charges by dopant were mirrored by PL findings. Molecular vibration fingerprints of both materials were expressed via Raman analysis. Computation shows that the Co dopants incorporate many electronic states around the Fermi level and close to the valence band maximum of MoS2 and BN monolayers and induce p-doping, which is implied a decrease in bandgap energy. Our findings also indicate that Co doping with concentrations of 4 and 8 wt.% can introduce magnetic states into the systems leading to magnetism. These characteristics serve to strengthen the catalytic performance of formulated products that were used to treat methylene blue (MB), a commonly determined pollutant in industrial wastewater. The 8 wt.% Co-doped MoS2 showed superior performance by degrading up to 98% MB, as envisaged by its enhanced catalytic reduction. The in vitro results revealed synergism and a more potent effect of doped MoS2 and BN nanocomposite for G+ compared with G- isolates. Antibacterial potential of Co-doped MoS2 and BN nanocomposite against both G+ and G- strains suggested through in vitro study was further confirmed throughout in silico molecular docking study against selected protein targets, which highlighted their biocidal mechanism and recommended them as prospective inhibitors of PBP4, ddlB, and FabI enzymes from S. aureus and E. coli.

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.

Single Al atom anchored on defective MoS2: An efficient catalytic site for reduction of greenhouse N2O gas by CO or C2H4 molecules

Single-atom catalysts have gained a lot of interest recently due to their remarkable catalytic activity in a number of chemical processes. Using density functional theory calculations, we investigate an Al-atom doped MoS2 (Al-MoS2) as a potential catalyst for the reduction of nitrous oxide (N2O) by CO or C2H4 molecules. The reduction of N2O over Al-MoS2 is achieved in two steps. N2O is first decomposed on the Al atom to form the Al-O* active site, and then CO or C2H4 interacts with the Al-O* site to generate CO2 or ethylene oxide. The elimination of the O* by a CO molecule on the Al atom requires a negligible activation barrier (0.05 eV), which is lower than previously obtained for noble metals. The adsorbed O* species on Al-MoS2 need a barrier of 0.36 eV to oxidize ethylene, which seems to be overcome at low temperatures. Since the adsorption energy of an O2 molecule is smaller than that of a N2O, N2O is expected to dominantly occupy the active site of Al-MoS2 catalyst. Nonetheless, it is found that the introduction of an O2 molecule increases the activation energies required for the removal of O* by CO and C2H4, and therefore prologs the reaction times.

Cr3+ Ion‐Induced Phase Stabilization of 1T−MoSe2 with Abundant Active Sites for Efficient Hydrogen Evolution Reaction

AbstractThe electrocatalytic performance of transition metal dichalcogenides (TMDs) can be hugely impacted by their phase and electronic structure. In this regard, stabilization of the 1T (metallic) phase is a substantial challenge to attain superior electrocatalytic activity compared to its thermodynamically stable polymorph (2H phase). This report provides a simple approach to introduce the 1T phase into 2H−MoSe2 through heteroatom (Cr3+) doping using a hydrothermal method. 1T/2H−MoSe2 (x Cr) (x=1,2,3 and 5) materials have shown better electrocatalytic HER activities compared to the 2H−MoSe2, especially 2% Cr3+ doped MoSe2 (1T/2H−MoSe2 (2 Cr)) have shown the best catalytic activity. 1T/2H−MoSe2 (2 Cr) exhibits a current density of 20 mA cm−2 at an overpotential of 176 mV, low Tafel slope of 77 mV/dec, high double layer capacitance (Cdl) of 78.3 mF cm−2 and good cyclic stability. The improved electrocatalytic activity of 1T/2H−MoSe2 (2 Cr) could be attributed to the high conductance, high 1T phase content and the greater number of active sites resulting from the introduction of Cr3+ ions into MoSe2. In addition, density functional theory (DFT) studies predict that the introduction of Cr3+ ions into the MoSe2 monolayer increases the conduction electron density in the basal plane at room temperature which in turn supports the generation of additional active sites along the basal plane.

Theoretical investigation of quantum capacitance in the functionalized MoS2-monolayer

In this work, we investigated the electronic structure and the quantum capacitance of a set of functionalized MoS2 monolayers. The functionalizations have been done by using different ad-atom adsorption on MoS 2 monolayer. Density functional theory calculations are performed to obtain an accurate electronic structure of ad-atom doped MoS2 monolayer with a varying degree of doping concentration. Subsequently, the quantum capacitance in each functionalized system was estimated. A marked quantum capacitance above 200 μF cm−2 has been observed. Our calculations show that the quantum capacitance of MoS2 monolayer is significantly enhanced with substitutional doping of Mo with transition metal ad-atoms. The microscopic origin of such enhancement in quantum capacitance in this system has been analyzed. Our DFT-based calculation reveals that the generation of new electronic states at the proximity of the band-edge and the shift of Fermi level caused by the ad-atom adsorption results in a very high quantum capacitance in the system.

Fe-doped MoS2 nanomaterials with amplified peroxidase mimetic activity for the colorimetric detection of glutathione in human serum

In this paper, transition metal-doped MoS2 2D materials have been explored for the colorimetric detection of glutathione based on peroxidase mimetic activity. We have synthesized (hydrothermal) and characterized various doped MoS2. Among them, Fe-doped MoS2 flowers exhibit excellent peroxidase-mimetic activity over MoS2 by inducing the oxidation of chromogenic substrate and results in a blue color charge transfer product. Property of this nanomaterial is exploited for efficacious detection of Glutathione level in the buffer as well as in serum samples which follows the steady-state kinetics for peroxidase mimetic activity and exhibits stability over harsh environmental conditions. The developed sensor shows good linearity for glutathione detection in the range 1–30 μM with a significant limit of detection (0.577 μM). The Fe-doped MoS2 with excellent mimetic activity is utilized to develop noble-metal free, high-performance, low-cost peroxidase mimetic activity for onsite detection of glutathione in the real sample.

CO oxidation over defective and nonmetal doped MoS2 monolayers

Defective (missing S atoms) and nonmetal (C- and N-) doped MoS2 monolayers in the 2H and 1T′ phases have been evaluated for catalyzing CO oxidation based on first-principles calculations. For the reaction 2CO + O2 → 2CO2, the oxidization of the first CO molecule is fairly easy and sometimes is even spontaneous, as the O2 molecule is highly activated or dissociates upon adsorption. However, for the defective (2H-), C-doped (1T′-), and N-doped (2H- and 1T′-) MoS2 monolayers, the remaining O* adatom often refuses to react with other CO molecules and is hard to be removed (barrier > 1.20 eV). Only when over the C-doped 2H- and defective 1T′-MoS2 monolayers, the removal of the second O* adatom requires to overcome moderate barriers (0.74 and 0.88 eV, respectively) by reacting with another CO molecule via the Eley–Rideal mechanism and the catalysts are recovered. The barriers can be further reduced by applying either tensile or compressive strain to the MoS2 nanosheet. In contrast, the Langmuir–Hinshelwood mechanism is followed over the metal-containing MoS2 nanosheets, as the bigger size of metal dopants allow the co-adsorption of CO and O2. Therefore, the C-doped 2H- and defective 1T′-MoS2 monolayers are promising nonmetal-doped catalysts for CO oxidation.

Formaldehyde Molecules Adsorption on Zn Doped Monolayer MoS2: A First-Principles Calculation.

Based on the first principles of density functional theory, the adsorption behavior of H2CO on original monolayer MoS2 and Zn doped monolayer MoS2 was studied. The results show that the adsorption of H2CO on the original monolayer MoS2 is very weak, and the electronic structure of the substrate changes little after adsorption. A new kind of surface single cluster catalyst was formed after Zn doped monolayer MoS2, where the ZnMo3 small clusters made the surface have high selectivity. The adsorption behavior of H2CO on Zn doped monolayer MoS2 can be divided into two situations. When the H-end of H2CO molecule in the adsorption structure is downward, the adsorption energy is only 0.11 and 0.15 eV and the electronic structure of adsorbed substrate changes smaller. When the O-end of H2CO molecule is downward, the interaction between H2CO and the doped MoS2 is strong leading to the chemical adsorption with the adsorption energy of 0.80 and 0.98 eV. For the O-end-down structure, the adsorption obviously introduces new impurity states into the band gap or results in the redistribution of the original impurity states. All of these may lead to the change of the chemical properties of the doped MoS2 monolayer, which can be used to detect the adsorbed H2CO molecules. The results show that the introduction of appropriate dopant may be a feasible method to improve the performance of MoS2 gas sensor.