Self‐Templated Fabrication of MoNi4/MoO3‐x Nanorod Arrays with Dual Active Components for Highly Efficient Hydrogen Evolution

A binder‐free efficient MoNi₄/MoO_3‐x nanorod array electrode with 3D open structure is developed by using Ni foam as both scaffold and Ni source to form NiMoO₄ precursor, followed by subsequent annealing in a reduction atmosphere. It is discovered that the self‐templated conversion of NiMoO₄ into MoNi₄ nanocrystals and MoO_3‐x as dual active components dramatically boosts the hydrogen evolution reaction (HER) performance. Benefiting from high intrinsic activity, high electrochemical surface area, 3D open network, and improved electron transport, the resulting MoNi₄/MoO_3‐x electrode exhibits a remarkable HER activity with extremely low overpotentials of 17 mV at 10 mA cm^?2 and 114 mV at 500 mA cm^?2, as well as a superior durability in alkaline medium. The water–alkali electrolyzer using MoNi₄/MoO_3‐x as cathode achieves stable overall water splitting with a small cell voltage of 1.6 V at 30 mA cm ^{? 2}. These findings may inspire the exploration of cost‐effective and efficient electrodes by in situ integrating multiple highly active components on 3D platform with open conductive network for practical hydrogen production.     

Efficient Catalysis of Hydrogen Evolution Reaction from WS2(1−x)P2x Nanoribbons

The rational design of Earth abundant electrocatalysts for efficiently catalyzing hydrogen evolution reaction (HER) is believed to lead to the generation of carbon neutral energy carrier. Owing to their fascinating chemical and physical properties, transition metal dichalcogenides (TMDs) are widely studied for this purpose. Of particular note is that doping by foreign atom can bring the advent of electronic perturbation, which affects the intrinsic catalytic property. Hence, through doping, the catalytic activity of such materials could be boosted. A rational synthesis approach that enables phosphorous atom to be doped into WS₂ without inducing phase impurity to form WS_{2(1? x )}P_{2 x} nanoribbon (NRs) is herein reported. It is found that the WS_{2(1? x )}P_{2 x} NRs exhibit considerably enhanced HER performance, requiring only ?98 mV versus reversible hydrogen electrode to achieve a current density of ?10 mA cm^?2. Such a high performance can be attributed to the ease of H‐atom adsorption and desorption due to intrinsically tuned WS₂, and partial formation of NRs, a morphology wherein the exposure of active edges is more pronounced. This finding can provide a fertile ground for subsequent works aiming at tuning intrinsic catalytic activity of TMDs.     

Edge‐Riched MoSe2/MoO2 Hybrid Electrocatalyst for Efficient Hydrogen Evolution Reaction

Molybdenum diselenide (MoSe₂) is widely considered as one of the most promising catalysts for the hydrogen evolution reaction (HER). However, the absence of active sites and poor conductivity of MoSe₂ severely restrict its HER performance. By introducing a layer of MoO₂ on Mo foil, MoSe₂/MoO₂ hybrid nanosheets with an abundant edge and high electrical conductivity can be synthesized on the surface of Mo foil. Metallic MoO₂ can improve the charge transport efficiency of MoSe₂/MoO₂, thereby enhancing the overall HER performance. MoSe₂/MoO₂ exhibits fast hydrogen evolution kinetics with a small overpotential of 142 mV versus RHE at a current density of 10 mA cm^?2 and Tafel slope of 48.9 mV dec^?1.     

Coupled Biphase (1T‐2H)‐MoSe2 on Mold Spore Carbon for Advanced Hydrogen Evolution Reaction

Performance breakthrough of MoSe₂‐based hydrogen evolution reaction (HER) electrocatalysts largely relies on sophisticated phase modulation and judicious innovation on conductive matrix/support. In this work the controllable synthesis of phosphate ion (PO₄^3?) intercalation induced‐MoSe₂ (P‐MoSe₂) nanosheets on N‐doped mold spore carbon (N‐MSC) forming P‐MoSe₂/N‐MSC composite electrocatalysts is realized. Impressively, a novel conductive N‐MSC matrix is constructed by a facile mold fermentation method. Furthermore, the phase of MoSe₂ can be modulated by a simple phosphorization strategy to realize the conversion from 2H‐MoSe₂ to 1T‐MoSe₂ to produce biphase‐coexisted (1T‐2H)‐MoSe₂ by PO₄^3‐ intercalation (namely, P‐MoSe₂), confirmed by synchrotron radiation technology and spherical aberration‐corrected TEM (SACTEM). Notably, higher conductivity, lower bandgap and adsorption energy of H⁺ are verified for the P‐MoSe₂/N‐MSC with the help of density functional theory (DFT) calculation. Benefiting from these unique advantages, the P‐MoSe₂/N‐MSC composites show superior HER performance with a low Tafel slope (≈51 mV dec^‐1) and overpotential (≈126 mV at 10 mA cm^‐1) and excellent electrochemical stability, better than 2H‐MoSe₂/N‐MSC and MoSe₂/carbon nanosphere (MoSe₂/CNS) counterparts. This work demonstrates a new kind of carbon material via biological cultivation, and simultaneously unravels the phase transformation mechanism of MoSe₂ by PO₄^3‐ intercalation.     

Anisotropic Spectroscopy and Electrical Properties of 2D ReS2(1–x)Se2x Alloys with Distorted 1T Structure

2D black phosphorus (BP) and rhenium dichalcogenides (ReX₂, X = S, Se) possess intrinsic in‐plane anisotropic physical properties arising from their low crystal lattice symmetry, which has inspired their novel applications in electronics, photonics, and optoelectronics. Different from BP with poor environmental stability, ReX₂ has low‐symmetry distorted 1T structures with excellent stability. In ReX₂, the electronic structure is weakly dependent on layer numbers, which restricts their property tunability and device applications. Here, the properties are tuned, such as optical bandgap, Raman anisotropy, and electrical transport, by alloying 2D ReS₂ and ReSe₂. Photoluminescence emission energy of ReS_{2(1? x )}Se_{2 x} monolayers (x from 0 to 1 with a step of 0.1) can be continuously tuned ranging from 1.62 to 1.31 eV. Polarization behavior of Raman modes, such as ReS₂‐like peak at 212 cm^?1, shifts as the composition changes. Anisotropic electrical property is maintained in ReS_{2(1? x )}Se_{2 x} with high electron mobility along b‐axis for all compositions of ReS_{2(1? x )}Se_{2 x} .     

Molybdenum Oxides – From Fundamentals to Functionality

The properties and applications of molybdenum oxides are reviewed in depth. Molybdenum is found in various oxide stoichiometries, which have been employed for different high‐value research and commercial applications. The great chemical and physical characteristics of molybdenum oxides make them versatile and highly tunable for incorporation in optical, electronic, catalytic, bio, and energy systems. Variations in the oxidation states allow manipulation of the crystal structure, morphology, oxygen vacancies, and dopants, to control and engineer electronic states. Despite this overwhelming functionality and potential, a definitive resource on molybdenum oxide is still unavailable. The aim here is to provide such a resource, while presenting an insightful outlook into future prospective applications for molybdenum oxides.     

Out‐of‐Plane Strain Induced in a Moiré Superstructure of Monolayer MoS2 and MoSe2 on Au(111)

Making contact of transition metal dichalcogenides (TMDCs) with a metal surface is essential for fabricating and designing electronic devices and catalytic systems. It also generates strain in the TMDCs that plays significant role in both electronic and phonon structures. Therefore, detailed understanding of mechanism of the strain generation is important to fully comprehend the modulation effect for the electronic and phonon properties. Here, MoS₂ and MoSe₂ monolayers are grown on Au surface by chemical vapor deposition and it is demonstrated that the contact with a crystalline Au(111) surface gives rise to only out‐of‐plane strain in both MoS₂ and MoSe₂ layers, whereas no strain generation is observed on polycrystalline Au or SiO₂/Si surfaces. Scanning tunneling microscopy analysis provides information regarding consequent specific adsorption sites between lower S (Se) atoms in the S? Mo? S (Se? Mo? Se) structure and Au atoms via unique moiré superstructure formation for MoS₂ and MoSe₂ layers on Au(111). This observation indicates that the specific adsorption sites give rise to out‐of‐plane strain in the TMDC layers. Furthermore, it also leads to effective modulation of the electronic structure of the MoS₂ or MoSe₂ layer.     

Glutathione Depletion in a Benign Manner by MoS2‐Based Nanoflowers for Enhanced Hypoxia‐Irrelevant Free‐Radical‐Based Cancer Therapy

Tumor hypoxia significantly diminishes the efficacy of reactive oxygen species (ROS)‐based therapy, mainly because the generation of ROS is highly oxygen dependent. Recently reported hypoxia‐irrelevant radical initiators (AIBIs) exhibit promising potential for cancer therapy under different oxygen tensions. However, overexpressed glutathione (GSH) in cancer cells would potently scavenge the free radicals produced from AIBI before their arrival to the specific site and dramatically limit the therapeutic efficacy. A synergistic antitumor platform (MoS₂@AIBI‐PCM nanoflowers) is constructed by incorporating polyethylene‐glycol‐functionalized molybdenum disulfide (PEG‐MoS₂) nanoflowers with azo initiator and phase‐change material (PCM). Under near‐infrared laser (NIR) irradiation, the photothermal feature of PEG‐MoS₂ induces the decomposition of AIBI to produce free radicals. Furthermore, PEG‐MoS₂ can facilitate GSH oxidation without releasing toxic metal ions, greatly promoting tumor apoptosis and avoiding the introduction of toxic metal ions. This is the first example of the use of intelligent MoS₂‐based nanoflowers as a benign GSH scavenger for enhanced cancer treatment.     

Engineering High‐Performance MoO2‐Based Nanomaterials with Supercapacity and Superhydrophobicity by Tuning the Raw Materials Source

Herein, a simple self‐assembly method is proposed for the fabrication of MoO₂‐based superhydrophobic material with record high contact angles (contact angle up to about 173°) for conductive metal oxides on hard/soft substrates. The spin‐coated surface demonstrates excellent oil–water separation efficiency (>98%) after 50 cycles and robust corrosion resistance after immersion into different pH solutions for 20 d. These water‐resistant coatings retain excellent superhydrophobicity after oil immersion, knife‐scratch, and long‐cycle sandpaper abrasion, which is not observed on most artificial surfaces. Meanwhile, the functionality switching from superhydrophobicity to supercapacity, which have an inverse relationship in aqueous solutions because of poor electrode wettability, is achieved simply by editing the raw materials source. Tuning of the raw materials leads to the same product MoO₂/graphitic carbon with different morphologies and functionalities. Different from superhydrophobic MoO₂/carbon ball flowers, MoO₂ nanotubes with carbon exhibit excellent supercapacity with a large gravimetric capacitance and great cycling stability.     

Materials chemistry and thermodynamics of REBa2Cu3O7−x

This review focuses on the materials chemistry and thermodynamics of the REBa₂Cu₃O_7?x (RE = rare earth) series of superconductors. The importance of this basic information for predicting and controlling structure and microstructure of single crystals, thin films, and bulk materials is discussed. Examples of where an understanding of the thermodynamics has led to advances in processing are presented, and future areas of research that are key to the second decade of superconductor processing are highlighted.