Mo-S Bonds Research Articles

Trace amounts of MoB MBene with layered configuration trigger catalytic converter of polysulfide

The formation of soluble lithium polysulfide severely limits the performance of the reversible capacity and cycle stability in lithium‑sulfur batteries. Herein, a carbon fiber cathode of LiS battery is proposed, and the two-dimensional metal boride material MoB MBene is selected as the catalyst of lithium‑sulfur battery. Theoretical calculations and experimental data have confirmed that MoB MBene performs exceptionally well in adsorbing polysulfides and preventing the shuttle effect. It also expedites the solid-liquid-solid phase transition and efficiently decrease the Li2S breakdown energy barrier. MoB MBene not only anchors polysulfides by generating MoS bonds in LiS redox reaction, but also accelerates the kinetics of polysulfide conversion by lowering the energy barrier of polysulfides conversion. By adopting MoB MBene as a catalyst, a lithium‑sulfur battery achieved a long cycle life (with only 0.0779 % attenuation after 800 cycles at 1C) and a high initial discharge capacity (1105 mAh g−1). This work could provide new perspectives on using MBene as a catalyst for LiS chemistry.

Ultrafine Mo2N Quantum Dots Embedded in N-Doped Graphene Sheets Enable Efficient Adsorption-Catalytic Transformation of Polysulfides.

Because of the high theoretical energy density of 2600 Wh kg-1, lithium-sulfur batteries (LSBs) are anticipated to be among the next generation of high-energy-density storage technologies. However, the practical application of LSBs has been severely hampered by the significant shuttle effect and slow redox kinetics of polysulfides (LiPSs). To address the above problems, in this paper, the concept of quantum dots (QDs) was introduced to design and synthesize Mo2N QD-modified N-doped graphene nanosheets (marked as Mo2N-QDs@NG), which were used as separator modification materials for LSBs. The experimental results demonstrated that the introduction of Mo2N QDs avoids stacking of graphene sheets and provides more active sites for the conversion of LiPSs. Moreover, Mo2N enhances the chemical fixation and catalyzes the liquid-solid conversion of soluble LiPSs by forming Mo-S and Li-N bonds with LiPSs. Additionally, establishing Mo-C bonds with Mo2N, N-doped graphene sheets can facilitate the transport of electrons and ions and physically prevent the diffusion of LiPSs, thus creating a highly conducting carbon structure to support electrochemical reactions. Benefiting from the synergistic effect of chemical immobilization and catalysis of Mo2N QDs with the physical confinement of NG, Mo2N-QDs@NG-PP batteries exhibit enhanced electrochemical performance.

Chemically bonded nonmetallic LSPR S-scheme hollow heterostructure for boosting photocatalytic performance

The light absorption, mass transfer, and charges separation are essential to the efficiency of photocatalytic reaction, but constructing photocatalyst with the three excellent properties is still challenging. Herein, the interfacial Mo-S bonds and oxygen vacancy synchronously decorated MoO3-x/Zn3In2S6 (MoO3-x/ZIS) heterostructure was rationally designed and synthesized. The oxygen-defective MoO3-x nanotubes showed hollow structure and local surface plasmonic resonance (LSPR) effect, which improved mass transfer and solar light absorption. Besides, the built-in electric field and interfacial Mo-S bond provided endogenetic impetus and channels for rapid photoexcited charge carriers transfer and separation. The photocatalytic hydrogen (H2) evolution and hydrogen peroxide (H2O2) production on optimal MoO3-x/ZIS composite were 17.34 and 4.47 mmol g−1 h−1, respectively. The apparent quantum efficiency of MoO3-x/ZIS for H2 evolution at 400 nm was about 13.92 %, which was 8.09 times higher than that of ZIS. Moreover, the MoO3-x/ZIS also displayed excellent activities on the selective 5-hydroxymethylfurfural dehydrogenation. The in-situ X-ray photoelectron spectroscopy, electron paramagnetic resonance, in-situ selective photodeposition, and density functional theory calculation confirmed the S-scheme charge transfer pathway between MoO3-x and ZIS. This study provides an effective avenue for designing multifunctional photocatalysts based on the synergistic effects of chemically bonded S-scheme heterostructure and nonmetallic LSPR effect.

Interfacial chemical bonds and sulfur vacancies synergistically modulated charge transfer in ZnIn2S4/MoO2-C Ohmic-junction photocatalyst for efficient hydrogen evolution

The construction of an Ohmic contact with a strong built-in electric field is crucial for the photocatalytic hydrogen evolution performance. However, consciously modulating Ohmic contacts to facilitate charge transfer remains very difficult. Herein, a sulfur vacancies-rich ZnIn2S4/MoO2-C Ohmic contact structure was synthesized by solvothermal method. Experimental results and DFT calculations indicated that the structure of MoO2-C changes under high temperature and pressure conditions, leading to the formation of interfacial Mo-S bonds with sulfur-vacancy-rich ZnIn2S4 in close contact. Importantly, the electronic structure of the Ohmic junction was synergistically modulated by interfacial chemical bonds and sulfur vacancies, creating a strong built-in electric field that effectively facilitated charge transfer and exciton dissociation at the interface. The optimized ZnIn2S4/MoO2-C composite exhibited a photocatalytic hydrogen evolution rate of 59.9 µmol h−1, which was 12 times and 4.7 times higher than that of ZnIn2S4 without sulfur vacancies and with sulfur vacancies, respectively. This work presented a novel method of synergistically modulating charge transfer in Ohmic junctions, promising improved photocatalytic performance.

Dual-function hollow MoS2 nanocages decorated on graphene sheets as efficient sulfur hosts for advanced lithium-sulfur batteries

Due to the presence of polysulfitabde shuttling, serious electrode expansion, and the low electrical conductivity of sulfur materials at room temperature, the commercialization of Li-S batteries is still not feasible. In this study, we have synthesized unique hollow molybdenum disulfide nanocages/reduced graphene oxide (H-MoS2/rGO) composites to be employed as highly effective cathodes for Li-S batteries. In this well-designed structure, the hollow MoS2 nanocages are tightly bound by C-O-Mo bonds and uniformly distributed across the graphene sheets. The dual-function MoS2 nanocages can adsorb polysulfides by Mo-S bond and accelerate the conversion reaction of S8 and Li2S. Moreover, the 3D rGO network with abundant pores effectively reduces the diffusion path and enhances the rapid transport of electrons and ions. The hybrid H-MoS2/rGO cathodes with these advantages exhibit a remarkable initial discharge capacity of 801.7 mAh g−1 at 1 C, as well as a high specific discharge capacity of 533.2 mAh g−1 is remained over 500 cycles.

Design and synthesis of a novel chiral photoacoustic probe and accurate imaging detection of hydrogen peroxide in vivo.

Nanocatalytic medicine, which aims to accurately target and effectively treat tumors through intratumoral in situ catalytic reactions triggered by tumor-specific environments or markers, is an emerging technology. However, the relative lack of catalytic activity of nanoenzymes in the tumor microenvironment (TME) has hampered their use in biomedical applications. Therefore, it is crucial to develop a highly sensitive probe that specifically responds to the TME or disease markers in the TME for precision diagnosis and treatment of diseases. In this work, a chiral photoacoustic (PA) nanoprobe (D/L-Ce@MoO3) based on the H2O2-catalyzed TME activation reaction was constructed in a one-step method using D-cysteine (D-Cys) or L-cysteine (L-Cys), polymolybdate, and cerium nitrate as raw materials. The designed and synthesized D/L-Ce@MoO3 chiral nanoprobe can perform in situ, non-invasive, and precise imaging of pharmacological acute liver injury. In vivo and in vitro experiments have shown that the D/L-Ce@MoO3 probe had chiral properties, the CD signal decreased upon reaction with H2O2, and the absorption and PA signals increased with increasing H2O2 concentration. This is because of the catalytic reaction between Ce ions doped in the nanoenzyme and the high expression of H2O2 caused by drug-induced liver injury to produce ·OH, which has a strong oxidizing property to kill tumor cells and destroy the Mo-S bond in the probe, thus converting the chiral probe into an achiral polyoxometalate (POM) with PA signal.

Defect-mediated Fermi level modulation boosting photo-activity of spatially-ordered S-scheme heterojunction

Spatially-ordered S-scheme photocatalysts are intriguing due to their enhanced light harvesting, spatially isolated redox sites, and strong redox abilities. Nonetheless, heightening the performance of S-scheme photocatalysts via controllable defect engineering is still challenging to now. In this work, multi-armed MoSe2/CdS S-scheme heterojunction with intimate Mo-S bond coupling and adjustable Se vacancies (VSe) and Mo5+ concentrations was constructed, which consisted of few- or even single-layered MoSe2 growing on the {11–20} facets of wurtzite CdS arms. The S-scheme charge transmission mechanism of MoSe2/CdS heterojunction was validated by density functional theory calculation combined with in situ photo-irradiated X-ray photoelectron spectroscopy, surface photovoltage, and radical measurements. Moreover, the Fermi level gap between CdS and MoSe2 was enlarged by regulating the contents of donor (VSe) and acceptor (Mo5+) impurities with synthesis temperature, which strengthens the built-in electric field and carriers transfer driving force of MoSe2/CdS composites, contributing to an outstanding H2 evolution activity of 52.62 mmol·g−1·h−1 (corresponding to an apparent quantum efficiency of 34.8 % at 400 nm) under visible-light irradiation (λ > 400 nm), 25.8 times that of Pt-loaded CdS counterpart and a substantial amount of reported CdS-containing photocatalysts. Our study results are anticipated to facilitate the rational design of advanced semiconductor nanostructures for efficient solar conversion and utilization.

MoO3 with the Synergistic Effect of Sulfur Doping and Oxygen Vacancies: The Influence of S Doping on the Structure, Morphology, and Optoelectronic Properties.

Molybdenum trioxide (MoO3) is an attractive semiconductor. Thus, bandgap engineering toward photoelectronic applications is appealing yet not well studied. Here, we report the incorporation of sulfur atoms into MoO3, using sulfur powder as a source of sulfur, via a self-developed hydrothermal synthesis approach. The formation of Mo-S bonds in the MoO3 material with the synergistic effect of sulfur doping and oxygen vacancies (designated as S-MoO3-x) is confirmed using Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR). The bandgap is tuned from 2.68 eV to 2.57 eV upon sulfur doping, as confirmed by UV-VIS DRS spectra. Some MoS2 phase is identified with sulfur doping by referring to the photoluminescence (PL) spectra and electrochemical impedance spectroscopy (EIS), allowing significantly improved charge carrier separation and electron transfer efficiency. Therefore, the as-prepared S-MoO3-x delivers a sensitive photocurrent response and splendid cycling stability. This study on the synergistic effect of sulfur doping and oxygen vacancies provides key insights into the impact of doping strategies on MoO3 performance, paving new pathways for its optimization and development in relevant fields.

Two-dimensional (2D) MoS2-nanosheet (NS) incorporated within electrospun PVA nanofibers: Fabrication and characterization study

In this study, with the help of grinding and sonication, the bulk state of molybdenum disulfide was transformed into a two-dimensional sheet, and composite nanofiber consisting of molybdenum disulfide MoS2/polyvinyl alcohol (PVA) has been successfully developed via electrospinning process. X-ray diffraction (XRD) pattern showed the preferred orientation along the (002) plan of The MoS2 nanosheet. Rietveld refinement was applied to obtain the microstructure parameters of the MoS2. The formation of S-S and Mo-S bonds in MoS2 was confirmed by the Fourier-transform infrared spectroscopy (FTIR). FE-SEM images reveal the surface morphology of MoS2 nanosheets, which typically exhibit a flat and layered structure resembling stacked atomic layers of MoS2 two-dimensional nature.In contrast, the MoS2/PVA fibers display a uniform, interconnected nanofiber network with a distinct random formation. Also, Atomic Force Microscopy (AFM) images show the formation of the uniform MoS2/PVA nanofibers, and the evaluated root mean square (RMS) roughness values for PVA and MoS2/PVA fibers are 250 nm and 277 nm, respectively. To elucidate the elemental composition of the MoS2 nanofibers, Energy Dispersive X-ray Spectroscopy (EDX) analysis was performed, confirming the presence of molybdenum and sulfur in the compound. Finally, diffuse reflectance spectroscopy (DRS) was applied to study the optical properties of the MoS2/PVA composite. In addition, the measurement of the contact angle shows that the surface of the nanofibers is hydrophilic, and the amount of hydrophilicity decreases by adding MoS2 nanosheets.

Mo4/3B2Tx induced hierarchical structure and rapid reaction dynamics in MoS2 anode for superior sodium storage

Molybdenum sulfide (MoS2) with large layer distance and high theoretical capacity has been identified as one of the most promising anodes for sodium ion batteries, but the poor intrinsic conductivity and severe structural agglomeration restricted its diffusion kinetic and specific capacity. In this work, the synergistic effect of heterogeneous interface and Na2S adsorption/conversion active sites was employed to construct Mo4/3B2Tx-MoS2@C composites using a self-assembly and calcination strategy. Theoretical calculation and experimental results demonstrated that the charge transfer and interface between Mo4/3B2Tx and MoS2 along with the 3D hydrangea-like structure improved the intrinsic conductivity and provided fast ion diffusion channels, boosting the electrochemical kinetics; while the favorable adsorption of Na2S and weakened Na-S bond at Mo4/3B2Tx-Mo interface optimized the recombination energies of Mo-S bond, accelerating the ion diffusion and enhancing the electrochemical reversibility. In addition, the copious sulfur vacancies provided additional active sites for ion storage, ameliorating the electrochemical capacity. As expected, the novel Mo4/3B2Tx-MoS2@C electrode delivered a satisfactory rate capacity (340.6 mAh g−1 at 1 A g−1) and durable cyclic performance (267.2 mAh g−1 after 600 cycles at 2 A g−1). When paring with Na3V2(PO4)3, the Mo4/3B2Tx-MoS2@C||Na3V2(PO4)3 full cell exhibited high energy densities of 234.0 and 131.7 Wh kg−1 at 215.7 W kg−1 and 4.4 kW kg−1, respectively. The proposed synergistic strategy of heterogeneous interface and Na2S adsorption/conversion active sites provided a new guidance for the rational design of transitional metal sulfide anodes for sodium ion batteries.

Enhanced photocatalytic hydrogen generation efficiency through molybdenum-sulfur dual sites synergistic catalysis

Photocatalysis has gained significant attention in recent years for water splitting, with graphitic carbon nitride (g-C3N4) emerging as a promising candidate. However, the low carrier mobility and the lack of active sites for hydrogen evolution limit photocatalytic hydrogen evolution performance. Herein, this work presents a facile approach to achieve single Mo sites with a unique local coordination structure featuring one Mo atom coordinated with two nitrogen atoms and one sulfur atom. Among the prepared photocatalysts, 6 wt% Mo/SCN exhibits the highest photocatalytic hydrogen evolution activity with a yield rate of 4.05 mmol g-1 h-1, which is 13 times higher than that of pure g-C3N4 and superior to most of the g-C3N4 series photocatalysts. Experimental results and density functional theory calculations confirm that the Mo single-atom and S atom have synergistic catalysis under the co-modification, and the formed Mo-S bonds will enhance the ability of the substrate to anchor the Mo single-atom to enhance the stability of the photocatalyst. This work offers insights into transition metal single-atom and synergistic catalysis design for photocatalytic hydrogen evolution.

Bridging the gap between metallic MoO2 and ZnIn2S4 for enhanced photocatalytic H2 production

Noble metal-free cocatalysts have shown unprecedented potential in enhancing photocatalytic H2 evolution. However, it remains challenging to accelerate the carrier transfer rate by circuiting the substantial Schottky barrier between the metallic cocatalyst and the semiconductor. Herein, an in-situ carbonization strategy is used to accurately anchor MoO2 nanoparticles onto the surface of conductive carbon rods (MoO2/C), which serves as an efficient and stable metallic cocatalyst for ZnIn2S4 towards photocatalytic H2 evolution. The in-site derived carbon skeleton not only prevents the agglomeration of MoO2 nanoparticles thus enriching the active sites for H2 evolution, but also acts as conductor of photogenerated electrons to accelerate electron transfer. In addition, the formed Mo-S bonds at the interface provide additional electron transport channels for hierarchical core–shell MoO2/C@ZnIn2S4 (MO/C@ZIS) heterojunction. It is worth noting that the H2 evolution activity of the optimized MO/C@ZIS sample (2357 μmol·h−1·g−1) is 8.7 times higher than pure ZnIn2S4 (271 μmol·h−1·g−1), and also surpasses the activity of optimized Pt-modified ZnIn2S4 (2123 μmol·h−1·g−1). This work casts a new paradigm for the rational engineering of heterointerface between metallic cocatalysts and semiconductors towards fast electron transport and enhanced photocatalytic performance.

1T/2H MoSe2 modified ZnIn2S4 with modulating internal electric field to boost efficient performance of photocatalytic H2 evolution and epoxide alcoholysis

Herein, the extended layer spacing 1T MoSe2 coupled with ZnIn2S4 nanosheets through in-situ growth, and ultimately obtained 1T /2H MoSe2/ZnIn2S4 photocatalysts with S-scheme heterojunction. This rational structure enables photogenerated carriers to rapidly transfer to MoSe2 via Mo-S bond. In order to further address the problem of wasted oxidative half-reaction, we rely on the dehydrogenation of benzyl alcohol as a carrier for hole depletion. Notably, optimized 1T/2H MoSe2/ZnIn2S4 has superior H2 evolution ability, reaching up to 11.271 mmol·g−1·h−1 and the apparent quantum efficiency at 420 nm is 10.3 %. Meanwhile, the conversion rate of benzyl alcohol to high value-added benzaldehyde is 60.60 %. In addition, the Zn acidic sites can achieve polarization of epoxides and precise cleavage C-O bond. Thus, it also has the ability to high selectivity and efficient photocatalytic epoxide alcoholysis. This work proposes a new insight for enhancing photocatalytic properties via regulating IEF to fabricate S-scheme heterostructure.

Promoted Catalytic Activity of CoSx@MoSx/MoOx Supported on Carbon Papers for Electrocatalytic Hydrogen Evolution Reaction

Developing cost-effective and stable materials for the electrocatalysis of hydrogen evolution reaction (HER) remains challenging. In this study, efficient catalysts for HER were synthesized by integrating the cobalt and molybdenum oxides via electrodeposition, followed by subsequent sulfurization of the as-prepared oxides using chemical vapor deposition (CVD). This methodology allowed the incorporation of both cobalt and molybdenum components into the catalyst in a single step. The as-synthesized CoSx@MoSx/MoOx-based catalysts exhibited excellent hydrogen production performance in acidic media owing to the presence of Co-S and Mo-S bonds in the hybrid structure. Particularly, CoSx@MoSx/MoOx(90@360) and MoSx@CoOx(180@180) displayed the best HER performances with low overpotentials of 80 mV and 150 mV, respectively. The catalysts were highly stable, with their stability preserved for over 1000 cycles with marginal reduction in overall efficiency. Therefore, these findings suggest the potential of CoSx@MoSx/MoOx and MoSx@CoOx composites as ideal candidates for developing low-cost catalysts for electrochemical hydrogen production.

Coordination environment engineering of MoS2-based nanocomposite by Ni atom incorporation for enhanced peroxymonosulfate activation

Ni-doped MoS2 can activate PMS effectively to degrade organic pollutants because the Ni doping can modulate the adsorption energy barrier of MoS2 to PMS molecule. However, how the coordination environment between Ni and MoS2 affects the activation of PMS to generate active species is poorly understood. In this paper, Ni substitutional or Ni adsorptive doping of MoS2 supported on TiO2/N-doped carbon nanofibers (designated as Nisub-MTC or Niads-MTC, respectively) were synthesized and used as PMS activators to degrade tetracycline (TC), respectively. In the case of Niads-MTC that the Ni atoms adsorb atop of S vacancies in MoS2, the reaction kinetic constant for TC degradation can reach 0.3381 min−1 within 10 min in Niads-MTC/PMS/Vis system. That is 1.84 times higher than that in Nisub-MTC/PMS/Vis system (0.1835 min−1), where the Mo sites in MoS2 are substituted with Ni atoms. This possibly due to that the Ni adsorptive doping can improve the regional activity of Mo-S bonds, which is more efficient than increasing the S vacancies by Ni substitutional doping. DFT calculations further support that the lower adsorption energy barriers of PMS were obtained on Ni adsorptive doping MoS2. Moreover, the main active species and possible TC degradation pathways were proposed. This work provides a new insight for designing metal doped heterogeneous catalysts with suitable coordination environments to improve PMS activation efficiency.

Highly efficient capture of iodine vapor by [Mo3S13]2− intercalated layered double hydroxides

From the swollen LDH, bulky [Mo3S13]2− anions are facilely introduced into the LDH interlayers to assemble the Mo3S13-LDH composite, which exhibits excellent iodine capture performance and good irradiation resistance. The positive-charged LDH layers may disperse the [Mo3S13]2− uniformly within the interlayers, providing abundant adsorption sites for effectively trapping iodine. The Mo-S bond serving as a soft Lewis base has strong affinity to I2 with soft Lewis acidic characteristic, which is conducive to improvement of iodine capture via physical sorption. Besides, chemisorption has a significant contribution to the iodine adsorption. The S22−/S2− in [Mo3S13]2− can reduce the I2 to [I3]− ions, which are facilely fixed within the LDH gallery in virtue of electrostatic attraction. Meanwhile, the S22−/S2− themselves are oxidized to S8 and SO42−, while Mo4+ is oxidized (by O2 in air) to Mo6+, which combines with SO42− forming amorphous Mo(SO4)3. With the collective interactions of chemical and physical adsorption, the Mo3S13-LDH demonstrates an extremely large iodine adsorption capacity of 1580 mg/g. Under γ radiation, the structure of Mo3S13-LDH well maintains and iodine adsorption capability does not deteriorate, indicating the good irradiation resistance. This work provides an important reference to tailor cost-effective sorbents for trapping iodine from radioactive nuclear wastes.

Interfacial Mo-S bond-reinforced hierarchical S-scheme heterostructure of Bi2MoO6@ZnIn2S4 for highly-selective and efficient CO2 photoreduction into CO

Developing highly-selective and efficient photocatalysts for converting CO2 into carbon-based fuels by solar energy is desirable, whereas it is still a severe challenge. Herein, we present a unique interfacial Mo-S bond-bridged hierarchical S-scheme heterostructured photocatalysts, prepared by in-situ loading ZnIn2S4 nanoflakes (ZIS-NFs) on the Bi2MoO6 porous micro-spheres (BMO-PMs) assembled from numerous nanosheets. The interfacial Mo-S bonds can reinforce the separation and migration of photoinduced charge carriers via the S-scheme mechanism in the BMO@ZIS heterostructure. Besides, its hierarchical heterostructure can improve the visible-light response ability, and afford plenty of active sites so as to benefit the CO2 adsorption and activation. Specifically, the combined results of experiment and density functional theory (DFT) calculations indicate that the fine heterostructure can not only convert the endoergic rate-determining step of bare ZIS (namely, CO2* hydrogenation to form COOH*) to an exoergic reaction process and lower the overall activation energy barrier, but also boost the desorption of CO* from the ZIS surface. As a result, in existence of H2O vapor without any sacrificial agents, the optimum photocatalyst (BMO@ZIS-0.4) manifests the outstanding CO2 photoreduction activity, with a CO yield and selectivity of 23.11 μmol g−1h−1 and 93.1 %, respectively, higher than those of the most reported photocatalysts. This work offers an in-depth insight for fabricating the interfacial chemical bond-modulated hierarchical S-scheme heterostructure with a remarkable performance of CO2 conversion.

Controllable construction of direct Z-scheme Mo2C-CdxZn1−xIn2S4 heterojunction via defect-mediated modulation for enhanced visible-light photocatalysis

Direct Z-scheme semiconductor heterostructures possess fascinating merits for solar photocatalysis, including increased light harvesting, spatially isolated photogenerated charge carriers, and well-preserved strong redox capability. However, steering Z-scheme charge transfer of semiconductor heterojunction in a controllable manner is still a challenging task. In this work, unique direct Z-scheme Mo2C-CdxZn1−xIn2S4 heterojunction is constructed via a defect-mediated modulating strategy, where Cd-doping switches the charge transfer mode of Mo2C-CdxZn1−xIn2S4 heterojunction from type-I to Z-scheme through increasing S vacancies, up-shifting conduction band level, and narrowing bandgap of CdxZn1−xIn2S4 component. Moreover, the defect-induced Mo-S bond affords fast channels for built-in electric field-induced Z-scheme photo-electrons transporting from Mo2C conduction band to CdxZn1−xIn2S4 valence band, supporting by X-ray photoelectron spectroscopy, surface photovoltage spectroscopy, and radical testing results. Noticeably, under irradiation of visible light (λ > 400 nm), Mo2C-CdxZn1−xIn2S4 Z-scheme heterojunction displays an excellent and stable photocatalytic H2-evolving activity, reaching an outstanding H2 generation rate of 28.12 mmol·g−1·h−1 with the corresponding high apparent quantum efficiency of 21.1% at 400 nm, far surpassing that of Pt-loaded C0.25ZIS and most documented ZnIn2S4-containing photocatalysts. The present work could inspire the crafty design of efficient Z-scheme photocatalysts through defect-mediated heterostructure construction and energy band engineering.

Molybdenum disulfide (MoS[formula omitted]) and reduced graphene oxide (rGO) nanocomposite based electrochemical sensor for detecting mercury(II) ions

In this study, a two-dimensional (2D) layered nanocomposite of molybdenum disulfide and reduced graphene oxide (rGO) was synthesized through a facile single-step hydrothermal method. Internal structure and morphological studies have shown that the vertical layered structure of MoS2 has grown over the horizontally aligned layer of reduced graphene oxide. The XRD analysis proved that the structure is multi-layered with 68.8 % crystallinity. Despite the highly crystalline nanocomposite structure, very few defects are also present in the network, as shown through Raman spectroscopy. Further, the presence of CS, RSR, CO, CO, MoO and MoS bonds, identified through XPS, indicates the successful synthesis of the MoS2-rGO nanocomposite. The nanocomposite was further evaluated for its electrochemical properties and applications regarding the sensing of mercury ions. Cyclic voltammetry shows that the oxidation peak current response increased by ∼103 % with the MoS2-rGO modified electrode compared to a bare electrode. The sensor has shown an excellent detection limit (LOD) of 1.6 μM, while the sensitivity and limit of quantification obtained from the sensor are 76.302 μM μA−1 cm−2 and 5.4 μM, respectively. The enhanced sensing performance of the MoS2-rGO modified sensor is attributed to the synergistic effect of MoS2 and rGO. The as-synthesized sensor also exhibits excellent stability, as only a 13% drop in current was observed after 60 days. This work proves that MoS2-rGO possesses enormous potential for developing next-generation heavy metal ion sensors.

Electronic structure of low-lying states of triatomic MoS2 molecule. The building block of 2D MoS2.

Molybdenum disulfide (MoS2) is the building component of 1D-monolayer, 2D-layered nanosheets and nanotubes having many applications in industry, and it is detected in molecular systems observed in nature. Here, the electronic structure and the chemical bonding of sixteen low-lying states of the triatomic MoS2 molecule are investigated, while the connection of the chemical bonding of the isolated MoS2 molecule to the relevant 2D-MoS2, is emphasized. The MoS2 molecule is studied via DFT and multireference methodologies, i.e., MRCISD(+Q)/aug-cc-pVQZ(-PP)Mo. The ground state, 3B1, is bent (Mo-S=2.133 Å and φ(SMoS)=115.9°) with a dissociation energy to atomic products of 194.7 kcal/mol at MRCISD+Q. In the ground and in the first excited state a double bond is formed between Mo and each S atom, i.e., . These two states differ in which d electrons of Mo are unpaired. The Mo-S bond distances of the calculated states range from 2.108-2.505 Å, the SMoS angles range from 104.1-180.0°, and the Mo-S bonds are single or double. Potential energy curves and surfaces have been plotted for the 3B1, 5A1 and 5B1 states. Finally, the low-lying septet states of the triatomic molecule are involved in the material as a building block, explaining the variety of its morphologies.