Mo Bond Research Articles

Modulating Electronic Structure of MoS2 Nanosheets by Sulfide Enrichment‐Induced Vacancies for Enhanced Photocatalytic Hydrogen Production

AbstractEnhancing photocatalytic activity by changing the electronic structure of the catalyst is an effective strategy. 2H‐MoS2 has semiconductor properties, and its unsaturated side S atom is the main active site for its photocatalytic activity. However, due to the weak S─H bond energy, its hydrogen adsorption capacity is weak. In this work, the electronic structure of MoS2 is adjusted by S‐rich treatment, resulting in the formation of Mo vacancy (MoS2‐VMo). The level of Mo vacancies was assessed using UV–vis diffuse reflectance spectroscopy (UV–vis DRS). As these vacancies can capture certain photogenerated electrons, thereby reducing the recombination of electron‐hole pairs. Through DFT calculation, it is found that the antibonding orbital electron filling of MoS2‐VMo is weakened, the bond energy of S─Mo bond is weakened, and the bond energy between S─H bond is enhanced, which is more conducive to proton adsorption. The photocatalytic activity for hydrogen evolution of MoS2‐3, which underwent the optimal S‐rich treatment, achieved a remarkable rate of 2404.6 µmol g−1 h−1 in dye eosin Y (EY) sensitization system, significantly surpassing that of MoS2 lacking the S‐enriched treatment. This study introduces a novel concept for enhancing the photocatalytic hydrogen evolution performance of metal sulfides via defect engineering.

Molecular Intercalation Enables Phase Transition of MoSe2 for Durable Na-Ion Storage.

1T-MoSe2 is recognized as a promising anode material for sodium-ion batteries, thanks to its excellent electrical conductivity and large interlayer distance. However, its inherent thermodynamic instability often presents unparalleled challenges in phase control and stabilization. Here, a molecular intercalation strategy is developed to synthesize thermally stable 1T-rich MoSe2, covalently bonded to an intercalated carbon layer (1TR/2H-MoSe2@C). Density functional theory calculations uncover that the introduced ethylene glycol molecules not only serve as electron donors, inducing a reorganization of Mo 4d orbitals, but also as sacrificial guest materials that generate a conductive carbon layer. Furthermore, the C─Se/C─O─Mo bonds encourage strong interfacial electronic coupling, and the carbon layer prevents the restacking of MoSe2, regulating the maximum 1T phase to an impressive 80.3%. Consequently, the 1TR/2H-MoSe2@C exhibits an extraordinary rate capacity of 326mAhg-1 at 5Ag-1 and maintains a long-term cycle stability up to 1500 cycles, with a capacity of 365mAhg-1 at 2Ag-1. Additionally, the full cell delivers an appealing energy output of 194Whkg-1 at 208Wkg-1, with a capacity retention of 87.3% over 200 cycles. These findings contribute valuable insights toward the development of innovative transition metal dichalcogenides for next-generation energy storage technologies.

Theoretical insights into the extraction behaviors of neptunium(VI) and plutonium(IV) based on the structure of organophosphorus ligands

Organophosphorus ligands such as TBP, TiAP, and DMHMP have exhibited excellent performance in recovering actinides from spent fuel. In this work, the molecular geometries and properties of TBP, TiAP and DMHMP were investigated using density functional theory calculations. Furthermore, the extraction mechanism of ligands for actinides (Np(Ⅵ), Pu(Ⅳ)) was further elucidated by simulating the microstructures and extraction reactions of metal–ligand complexes. The results demonstrate that the complexation ability of the three ligands on actinide cations (NpO22+ and Pu4+) follows the order of DMHMP > TiAP > TBP. The electrostatic potential (ESP) analysis indicates that the nucleophilic ability of DMHMP is stronger than that of the other two ligands. The frontier molecular orbital analysis of the three ligands represents that DMHMP has the highest HOMO energy, suggesting that it has the strongest electron-donating capability and is more likely to bond with metal ions. The values of Wiberg bond indices (WBI) suggest that the MO bonds in DMHMP complexes have more covalency. According to the QTAIM analysis, the interactions between actinide cations and the ligands are predominantly ionic in nature. The molecular orbital analysis of the complexes shows that the M(NO3)n·2DMHMP (MNpO22+ and Pu4+) complexes are more stable, which is supported by thermodynamic energy analysis. This work has clarified the complexing properties of actinide cations with three ligands, shedding light on the extraction mechanisms of organophosphorus ligands for actinide cations. It is anticipated to lay the theoretical foundation for the efficient recovery of critical actinide elements in spent fuel reprocessing, which will also provide innovative approaches for the design and development of related separation processes.

Understanding the promotion effect of Pt in the reaction system of water gas shift reaction catalyzed by Pt/α-MoC from theoretical perspectives

Pt/α-MoC is an outstanding catalyst for the low-temperature water gas shift (WGS, CO + H2O → H2 + CO2) reaction, exhibiting elevated activity, stability, and selectivity. In this study, three significant active site models (α-MoC-111, Pt-111, and Pt1/α-MoC-111) in Pt/α-MoC catalyst were established to investigate the promotion effect of Pt on the WGS reaction catalyzed by Pt/α-MoC. The results indicate that a synergistic effect at the metal-carbide interface enhances chemical activity compared to pure Pt-111 and α-MoC-111. Firstly, the surface of Pt1/α-MoC-111 exhibits strong metal-support interaction between Pt single atom and α-MoC-111 surface. Compared to the α-MoC-111 surface, the introduction of Pt strengthens the Mo−Mo bond while weakening the Mo−C bond. Secondly, adding a Pt atom significantly increases adsorption strength for CO and H2O, while decreasing it for products (CO2), oxides (O atom), and by-products (C atom). The advantage of suppressing surface carbon deposition and oxidation is observed on the surface of Pt1/α-MoC-111. Furthermore, elementary reactions from the three mainstream reaction pathways of the WGS reaction are systematically calculated to evaluate catalytic performance among these three active sites. On the Pt1/α-MoC-111 surface, activation energy barriers for H2O dissociation and CO oxidation are reduced. This provides theoretical ideas for designing high-efficiency α-MoC based catalysts in the future.

Half‐Sandwich, Bent‐Sandwich and Triple‐Decker Molybdenum Complexes of S2N2 – Fluxionality and Metal‐Metal Bond

AbstractThe instability of the π‐complexes of electron‐rich inorganic aromatics with transition metal fragments, contrary to their conventional aromatic analogues, was investigated by taking the four‐membered 6π‐electron S2N2. Our theoretical investigation based on fragment molecular orbitals and Energy Decomposition Analysis with Natural Orbitals for Chemical Valence (EDA‐NOCV) on the bonding nature of different types of π‐complexes of S2N2 viz. half‐sandwich, bent‐sandwich and triple‐decker type complexes with molybdenum fragment reveals that S2N2 can potentially act as a six π‐electron donor. However, due to the lower energy π* MOs the π‐back donation from metal fragment is stronger than the π‐donation, which might lead to weaking of the overall ring structure and low dissociation energy. The dissociation energy for dissociation of one S2N2 ring increases with the increasing number of S2N2 in the complex. The smaller size of the ring leads to fluxional behaviour in order to attain orbital compatibility between the π‐MOs and the metal orbitals. Also, the triple decker complex depicts an unsymmetric middle deck, where the middle S2N2 ring has been fragmented into two SN units along with a Mo−Mo bond. The higher dissociation energy of triple‐decker complexes can be corroborated well with the report of an isoelectronic triple‐decker complex [Mo2Te12]6+.

Accordion-like polyoxometalate hybrid architectures for capacity-dense and flexible Zn-Ion battery cathodes

Polyoxometalates (POMs) have received significant attention as functional materials owing to their tunable structures and sizes, versatile electronic properties, and multiple electrochemical redox behaviours. However, the hierarchical architecture of POMs and their unique Zn storage mechanism have yet to be explored for Zn-ion battery (ZIB) applications. Herein, we demonstrate an accordion-like hierarchical architecture of POM-based hybrids (L-rGO/PPy@POM) via a redox-relay Heck reaction, where multi-layered reduced graphene oxide (rGO)/polypyrrole (PPy) hybrid nanosheets are assembled with ultrafine POM nanoparticles through specific interaction. As confirmed through in situ and ex situ spectroscopic methods, the Mo=O bond is more implicated in Zn2+ insertion than the two Mo–O single bonds and two edge-sharing and corner-sharing Mo–Mo bonds. Owing to a fast and facile redox kinetics, the ZIB cells with l-rGO/PPy@POM delivered high specific capacity of 269.3 mAh g−1 at 100 mA g−1, high-rate capacity of 68.0 mAh g−1 at 10,000 mA g−1, and 80.4% of capacity retention over 22,000 cycles in water-in-bisalt electrolytes. Furthermore, flexible quasi-solid-state ZIB full cells with l-rGO/PPy@POM cathode achieved the maximum volumetric energy and power densities of 51.1 mWh cmcell−3 and 1159.9 mW cmcell−3, demonstrating long-term cyclic stability and functional operation of various electronic devices.

Rapid Ozone Decomposition over Water‐activated Monolithic MoO3/Graphdiyne Nanowalls under High Humidity

AbstractCatalytic ozone (O3) decomposition at high relative humidity (RH) remains a great challenge due to the catalysts poison and deactivation under high humidity. Here, we firstly elaborate the role of water activation and the corresponding mechanism of the promoted O3 decomposition over the three‐dimensional monolithic molybdenum oxide/graphdiyne (MoO3/GDY) catalyst. The O3 decomposition over MoO3/GDY reaches up to 100 % under high humid condition (75 % RH) at room temperature, which is 4.0 times as high as that of dry conditions, significantly surpasses other carbon‐based MoO3 materials(≤7.1 %). The sp‐hybridized carbon in GDY donates electrons to MoO3 along the C−O−Mo bond, facilitating water activation to form hydroxyl species. As a result, hydroxyl species dissociated from water act as new active sites, promoting the adsorption of O3 and the generation of new intermediate species (hydroxyl ⋅OH and superoxo ⋅O2−), which significantly lowers the energy barriers of O3 decomposition (0.57 eV lower than dry conditions).

Tetra-μ3-selen-ido-1:2:3κ3Se;1:2:4κ3Se;1:3:4κ3Se;2:3:4κ3Se-tetrakis-[(η5-methyl-cyclo-penta-dien-yl)molybdenum(III)](6 Mo-Mo).

The title cluster compound, [Mo4(η5-C5H4Me)4(μ3-Se)4], was synthesized from the reaction of [Mo(η5-C5H4Me)(CO)3]2 with grey selenium in refluxing xylene solution under a nitro-gen atmosphere. The complete cluster is generated by a crystallographic twofold axis and contains an Mo4Se4 cubane-like core surrounded by four η5-methylcyclo-pentadienyl ligands. In the core, the four molybdenum atoms are connected to each other to form a tetra-hedron, with a selenium atom capping each face. The Mo-Mo bond lengths vary from 2.9857 (5) to 3.0083 (3) Å and the Mo-Se separations range from 2.4633 (4) to 2.4693 (5) Å.

Homogeneous Intercalation Chemistry and Ultralow Strain of 1T’’’ MoS2 for Stable Potassium Storage

AbstractIntercalation anodes usually exhibit better cyclability than conversion and alloying anodes for lithium or sodium storage due to the robust layered structure. However, for larger‐sized potassium accommodation, these intercalation anodes usually undergo huge layer expansion and structural distortion, triggering severe capacity fading. Herein, the novel 1T’’’ MoS2 is revealed the intercalation anode for stable K+ storage, in which metallic Mo─Mo bonds and puckered S layers accelerate the charge transfer and homogeneous K+ insertion. Moreover, the ultralow strain (3.5%) induced by the non‐detachable potassium ions pillar sustains the layered structure. Consequently, 1T’’’ MoS2 achieves a reversible capacity of 125 mA h g−1 at 0.2 C and keeps nearly 100% capacity retention at 1 C over 500 cycles. In situ characterizations and density functional theory simulations reveal the in‐depth intercalation reaction accompanied by the MoS2 phase transformation between 1T’’’ and 1T’ during cycling. Furthermore, a 1T’’’ MoS2//MCMB K‐dual ion battery displays a superior cycling lifespan with 98% capacity retention over 250 cycles. This study provides a new intercalation anode and contribute to the electrode design for stable potassium ion storage.

MoOx monolayers over TiO2 for the selective oxidation of isobutene

The morphology effect of TiO2 on the dispersion of molybdena species and the performance of the resulting MoOx/TiO2 catalysts in selective oxidation of isobutene to methacrolein were examined. Two-dimensional MoOx monolayers in Mo–O–Mo bonds were well dispersed on TiO2 nanosheets that were preferentially enclosed by the {001} facets. However, aggregated MoOx clusters enriched in terminal MoO bonds were formed over TiO2 nanospindles dominated by the {101} facets. The superior performance of the MoOx monolayers, regarding activity, selectivity and stability, was ascribed to the synergetic effect between MoOx monolayers and TiO2 (001) facets.

Joule heating synthesis of well lattice-matched Co2Mo3O8/MoO2 heterointerfaces with greatly improved hydrogen evolution reaction in alkaline seawater electrolysis with 12.4 % STH efficiency

Herein, through a rapid Joule heating method, we have successfully prepared well lattice-matched Co2Mo3O8/MoO2 heterointerfaces on Ni foam (Co2Mo3O8/MoO2/NF) in only 130 s. Notably, the rapid Joule heating can effectively avoid oxidation of catalyst caused by prolonged heating and achieve rich uncoordinated Mo4+ sites, which contributed to the enhanced electrocatalytic performance in hydrogen evolution reaction (HER). As-prepared Co2Mo3O8/MoO2 delivered remarkable HER activity (23 mV at 10 mA cm−2), which was comparable to Pt-based electrocatalyst. As-prepared sample also revealed excellent stability at 200-h test in electrocatalytic splitting of alkaline seawater. Of particular note, the solar-driven H2O-H2 electrolyzer also showed a promising solar-to-hydrogen (STH) efficiency of 12.4 %. The cell voltage for the home-made anion exchange membrane (AEM) seawater electrolyzer was only 2.13 V at 200 mA·cm−2 at 50 °C, and only 4.7 kW-h required to produce 1 m3 of H2. DFT calculations revealed that the electron redistribution spontaneously takes place at Co–O–Mo bonds at Co2Mo3O8/MoO2 heterointerfaces, which could regulate the electronic structure and d-band center of Mo sites, and then achieve high-efficiency adsorption of H2O on Mo sites and near-zero hydrogen-adsorption free energy on O sites. This study provided a new strategy to regulate the chemical states via Joule heating for highly efficient seawater splitting to evolve H2.

Construction of MoO2 Ultra-uniformly Coated FeS2 with Tailored Interfacial Traits toward Improved Energy Storage

Iron disulfide (FeS2), a low-cost material, displays considerable theoretical specific capacity (894 mA h g–1) but still suffers from shuttling of polysulfides and sluggish kinetics. The MoO2 electrocatalyst has been successfully applied in Li–S systems, bringing about fascinated electrochemical improvements. Herein, through the gasification coating manners, the ultra-uniform distribution of MoO2 with abundant catalytic sites is surprisingly obtained, incorporating with the establishment of interfacial Fe–O–Mo bonds. Benefiting from the unique structural traits, optimized FeS2@MoO2 delivers an initial discharge capacity of 1271 mA h g–1. In addition, after 100 cycles, the capacity of FeS2@MoO2 could reach ∼308 mA h g–1, larger than that of pristine FeS2. Supported by the kinetic analysis, it could be found that the existing Fe–O–Mo bonds contribute to enhanced ion/e– diffusion behaviors during the intercalation/deintercalation process, ultimately resulting in outstanding lithium-ion storage capacity. Moreover, benefitting from the detailed resistance analysis and the galvanostatic intermittent titration technique test, the existence of MoO2 and Fe–O–Mo interfacial bonds could facilitate the diffusion of ions/electrons transferring and structural stability. Thus, this work is expected to provide insights into the construction of MoO2 ultra-uniformly coated FeS2 with tailored interfacial traits in energy storage systems.

Enhanced degradation of azo dyes wastewater by S-scheme heterojunctions photocatalyst g-C3N4/MoS2 intimately coupled Rhodopseudomonas palustris with chitosan modified polyurethane sponge carrier

With the development of azo dyes in every aspect of life, azo dyes have brought serious harm to human beings and ecological environment. In this study, a new intimately coupling photocatalysis and biodegradation (ICPB) system was reported: The rod-like graphite carbon nitride-molybdenum disulfide (RCM) of S-scheme was prepared by hydrothermal method and loaded onto the exterior surface of chitosan modified polyurethane sponge (CPU), and Rhodopseudomonas palustris (R. palustris) with metabolic versatility, significant survivability and decomposition to toxic and nonbiodegradable organics was combined inside the carrier. The rod-like RCM and egg-like R. palustris in the CPU were observed, the 13.1° and 27.6° characteristic peaks of g-C3N4 and 33.4° and 57.6° characteristic peaks of MoS2 were detected, N–H, NC, C–S–Mo, N–Mo bonds were confirmed, and Eg = 2.42 eV were calculated in RCM, which confirmed the successful preparation of R. palustris/RCM@CPU. The doping ratio of MoS2 was 6%, RCM dosage was 0.2 g and chitosan doping ratio was 0.5%, R. palustris/RCM@CPU system showed high degradation efficiency. The removal rates of Congo red, methyl orange and carmine were 99.5%, 97.5% and 99.5%, respectively. The significant removal of R. palustris/RCM@CPU system on azo dyes was due to that the RCM of S-scheme produced strong oxidizing superoxide radical (.O2−), hydroxyl radical (.OH) and hole (h+), and could oxidize azo groups and benzene rings of azo dyes to form alkane compounds, which were mineralized by R. palustris. The close cooperation among CPU adsorption, RCM oxidation and R. palustris mineralization effectively enhanced the degradation efficiency of R. palustris/RCM@CPU system for a variety of azo dyes. This study would propose a new means for the degradation efficiency of azo dye wastewater.

Oxygen-vacancy-rich MoO2 supported nickel as electrocatalysts to promote alkaline hydrogen evolution and oxidation reactions

Hydrogen energy is the most suitable solution for long-term, large-scale energy storage, and the design of efficient, economical, and stable electrocatalysts for hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) is of great significance for its commercial development. Herein, Ni nanocluster supported on oxygen-vacancy-rich MoO2 (Ni/MoO2−x) is designed which contains a large number of oxygen vacancies and Ni–O–Mo bonds. According to X-ray photoelectron spectroscopy, the formation of oxygen vacancies and Ni–O–Mo bonds facilitates the transfer of electrons from Ni to O. The prepared Ni/MoO2−x@NF shows excellent hydrogen electrocatalytic activity, which is proved by a Tafel slope of only 26 mV dec−1 for HER and an exchange current density of 3.64 mA cm−2 for HOR. Theoretical calculations showed optimized free energy of hydrogen adsorption and hydroxide adsorption on Ni/MoO2−x, which can explain the origin of the high activity of the catalyst. This work provides a feasible strategy for designing non-precious metal hydrogen electrocatalytic materials in energy storage.

Prediction of elastic properties of face-centered cubic high-entropy alloys by machine learning

The machine learning (ML) models were proposed for predicting elastic properties of face-centered-cubic (FCC) high-entropy alloys (HEAs). The data set was from the first-principles calculation, which contained 186 samples. The goodness-of-fit (R2) values of predicted bulk modulus (B) and shear modulus (G) in the test set were 0.81 and 0.84, respectively. According to the results of ML, CoNiCuMoW HEAs have the largest B, G, elastic modulus (Y) and good ductility (G/B≤0.57) among the FCC HEAs with equal components. The first-principles calculation results show that the elastic anisotropy of (CoNiCuMo)1−xWx HEAs increases and ductility decreases with increasing W content. According to the analysis of charge density difference, there is obvious charge accumulation at W—W and W—Mo bonds, indicating the directional covalent bonds formed between W atoms and their neighboring atoms.

Oriented adsorption and efficient sensing of NO2 on MoSe2 monolayer: a comparative study with WSe2 monolayer

Oriented adsorption is very rare on two-dimensional inorganic thin layers. Based on preliminary study, density functional theory (DFT) was used to explore the adsorption and sensing behavior of NO2 on MoSe2 perfect and defective monolayers including selenium vacancy (VSe), molybdenum vacancy (VMo), and antisite defect of selenium on molybdenum site (SeMo) by large-scale sampling. The adsorption energy can reach 0.29 eV with 0.182 e charge transfer on the perfect monolayer. The adsorption ability is improved largely on VSe, VMo, and SeMo monolayers (3.27, 0.93, and 1.20 eV) with considerable charge transfer (0.583, 0.152, and 0.139 e, respectively), demonstrating the potential of MoSe2 monolayers as NO2 sensing materials. Meanwhile, similar to WSe2 monolayer, oriented adsorption of NO2 is disclosed. NO2 molecule extends mainly along the Se–Mo–Se trough and the Se–Mo bond on all the four MoSe2 monolayers. Whereas, the oriented adsorption ability is weaker than the WSe2 monolayer, which can be confirmed by the relatively small proportion of oriented adsorption conformations. This kind of double oriented adsorption behavior (vertical adsorption and adsorption along specific direction of the two-dimensional material) was considered to be due to the good polarity match between molecule and monolayer. Molecular dipole moment and material bond population are believed to be two important parameters that determine the oriented adsorption capacity of molecular-material systems. The successive discovery of the unique oriented adsorption and the deepening of understanding provide chance for molecular design of oriented adsorption of inorganic small molecules on two-dimensional layered materials. The strong dissociation ability of the anionic vacancy monolayer to NO2 molecule indicates that MoSe2 monolayer has a very high adsorption, capture, and activation potential for nitrogen oxides. Comparative study proved that the Mo site activity was less than the W site activity on the perfect monolayer, and defects could help the Mo site activity overtake. These findings provide pivotal guidance for creating advanced surface regulated electronic systems, such as sensors.

Density Functional Theory Study of Deoxydehydration Reaction by TiO2-Supported Monomeric and Dimeric Molybdenum Oxide Catalysts

The development of efficient heterogeneous catalysts for converting biomass into value-added chemical compounds remains at the forefront of catalysis research. Deoxydehydration (DODH) reaction that can transform vicinal hydroxy groups with the cis-configuration to the corresponding C═C bond in a single step is one of the promising techniques, and molybdenum oxide catalysts supported on TiO2 have been reported as an effective catalyst using hydrogen as a reducing agent. Here, using density functional theory calculations, structures of monomeric and dimeric molybdenum oxide catalysts supported on anatase TiO2(101) have been determined, and we decipher the reaction mechanisms of the conversion of 1,4-anhydroerythritol to 2,5-dihydrofuran over these catalysts as a model reaction. We have found that MoO3 and Mo2O5 are the most stable structures for monomeric and dimeric species that exhibit the oxidation states of MoVI and MoV–MoVI, respectively, under the experimental conditions. For monomeric species, it is rather difficult to catalyze DODH reaction due to the instability for MoIV species and also the higher barrier for the C–O bond scission for MoV or MoVI species. For dimeric species, structures with the oxidation state of MoIV–MoV or MoV–MoV that is found in the form of Mo2O4 exhibit promising energy profiles in terms of stability and energy barrier (∼1.0 eV) for the C–O bond dissociation. Considering the experimental facts that MoIV species is responsible for the DODH reaction and Mo–Mo bond is present, the MoIV–MoV structure could be the plausible active species. Our findings would provide useful information for the catalyst design using earth-abundant and less-expensive metal-based catalysts for the DODH reaction.

Direct utilization of crude and waste H2 via CO-tolerant hydrogenation

Direct utilization of crude and waste H2 via CO-tolerant hydrogenation

Correlation of structure and ionic-conductivity in phosphate glass using MAS-NMR and impedance spectroscopy: Influence of sodium salt

In the process of diminishing the safety concerns of sodium-ion batteries, the development of glass-based solid electrolyte materials has received adequate interest. Nevertheless, achieving a high ionic-conductivity at room temperature for glass materials remains a challenging task because of the poor correlation between the conductivity and the glass structure. Here, we attempt to understand the effective influence of NaCl on the structure and ionic-conductivity of the phosphate-based glass network. For this study, $x\mathrm{NaCl}\text{\ensuremath{-}}(100\text{\ensuremath{-}}x$) ($31.725\phantom{\rule{4pt}{0ex}}{\mathrm{Na}}_{2}\mathrm{O}\text{\ensuremath{-}}12.69\phantom{\rule{0.16em}{0ex}}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}\text{\ensuremath{-}}31.725\phantom{\rule{0.16em}{0ex}}{\mathrm{P}}_{2}{\mathrm{O}}_{5}\text{\ensuremath{-}}8.46\phantom{\rule{0.16em}{0ex}}\mathrm{NaF}\text{\ensuremath{-}}5.40\phantom{\rule{0.16em}{0ex}}{\mathrm{Na}}_{2}{\mathrm{SO}}_{4}\text{\ensuremath{-}}10\phantom{\rule{0.16em}{0ex}}{\mathrm{MoO}}_{3}$) glass systems (mol %) were selected, where $x=0$, 5, 10, 15, and 20 mol %. To investigate structural changes with the addition of different NaCl concentrations, $^{27}\mathrm{Al}, ^{23}\mathrm{Na}, ^{31}\mathrm{P}$ magic angle spinning nuclear magnetic resonance (MAS-NMR), $^{31}\mathrm{P}$ two-dimensional (2D) phase-adjusted spinning sideband (PASS), and $^{31}\mathrm{P}$ 2D J-resolved NMR techniques and Raman spectroscopic techniques were utilized. Impedance spectroscopy and ac conductivity spectra were used to assess ionic-conductivity and sodium-ion dynamics, respectively. Impedance spectral analysis reveals that the ionic-conductivity of the base glass is increased by 2.4 times (from 1.85 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}7}$ to 4.44 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}7}$ S/cm at 373 K) with the addition of 20 mol % of NaCl. Raman spectra confirm the presence of P\ensuremath{-}O\ensuremath{-}Mo and the absence of Mo\ensuremath{-}O\ensuremath{-}Mo bonds in these glass systems, and $^{31}\mathrm{P}$ 2D J-resolved spectra indicate the absence of P\ensuremath{-}O\ensuremath{-}P bonds. Upon increasing the NaCl concentration, significant changes in the shapes of $^{31}\mathrm{P}$ and $^{27}\mathrm{Al}$ MAS-NMR spectra were observed, indicating the effective influence of NaCl on the distribution of alumina and phosphorus structural units. Irrespective of the temperature, sodium-ion dynamic studies show that the mean-square displacement $\ensuremath{\langle}{R}^{2}({t}_{p})\ensuremath{\rangle}$ decreases with increasing NaCl concentration up to 10 mol % and then increases with a further increase in NaCl concentration. This investigation aids in understanding the sodium-ion dynamics and the structural information of a multicomponent glass system to enhance the room-temperature conductivity.

Charge self-regulation in 1T'''-MoS2 structure with rich S vacancies for enhanced hydrogen evolution activity

Active electronic states in transition metal dichalcogenides are able to prompt hydrogen evolution by improving hydrogen absorption. However, the development of thermodynamically stable hexagonal 2H-MoS2 as hydrogen evolution catalyst is likely to be shadowed by its limited active electronic state. Herein, the charge self-regulation effect mediated by tuning Mo−Mo bonds and S vacancies is revealed in metastable trigonal MoS2 (1T'''-MoS2) structure, which is favarable for the generation of active electronic states to boost the hydrogen evolution reaction activity. The optimal 1T'''-MoS2 sample exhibits a low overpotential of 158 mV at 10 mA cm−2 and a Tafel slope of 74.5 mV dec−1 in acidic conditions, which are far exceeding the 2H-MoS2 counterpart (369 mV and 137 mV dec−1). Theoretical modeling indicates that the boosted performance is attributed to the formation of massive active electronic states induced by the charge self-regulation effect of Mo−Mo bonds in defective 1T'''-MoS2 with rich S vacancies.