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Methyl mercaptan (MM) is one kind of volatile sulfur compound (VSC) with odor and properties (inflammable, highly toxic, and corrosive) similar to H2S; therefore, the highly sensitive and selective monitoring of ambient MM by chemiresistors is strongly essential, but it remains a challenge owing to its relatively weak reducibility/response in comparison with H2S. In this study, a novel chemiresistor composed of hexahedral particles SBO-loaded CdS nanoparticles has been prepared via a facile chemical precipitation method for the super-sensitive and highly-selective recognition of MM. The heterostructural CdS/SBO (0.05%) chemiresistor exhibited an extremely high response (114.7) to 100 ppm MM at a relatively low operating temperature (100 °C) and was about 36- and 9-fold higher than pure SBO and CdS chemiresistor, respectively. Various characterizations suggested that the sulfurization–desulfurization reaction, the abundant oxygen vacancies, and the generation of n–n heterojunctions at the interface promote the redox reaction of surface-active substances, thereby, boosting the outstanding MM response characteristics. In addition, the heterostructural chemiresistor possesses good selectivity, weak humidity interference, a lower limit of detection (LoD) of 82 ppb, and long-term stability (∼6% decline of response after 120 days), which promises practical applications in air quality (odor) monitoring. [ABSTRACT FROM AUTHOR]

Hydrogen solubility and diffusivity are the key features of hydrogen permeable membrane materials. To characterize the hydrogen permeation performance of NbTM (TM = W, Ru) phases, their hydrogen diffusion coefficient and solution coefficient, thermodynamic stability and chemical bonding are studied by a series of first principles calculations. The phonon spectra and elastic constants show that NbTM is dynamically stable. The TM–H chemical bonds have an ionic/covalent mixed character and are stronger than the Nb–H bond. The preferential diffusion paths of H in both Nb16H and Nb15TMH are from a tetrahedral interstitial site (TIS) to another TIS. The TM doping in Nb16H lowers the solubility and energy barrier of H diffusion and enhances the H diffusion coefficient (D), with Nb16RuH exhibiting the highest D value for TIS to TIS diffusion (2.14 × 10−8 m2 s−1) at 600 K. This study shows that alloying and temperature could significantly affect the solubility and diffusivity of hydrogen in Nb. Moreover, TM doping could greatly improve the hydrogen diffusion performance with good control of hydrogen embrittlement. [ABSTRACT FROM AUTHOR]

In this paper, we report a careful study of the properties and mechanisms of a 2LiBH4–MgH2 composite with a niobium oxide (Nb2O5) additive. It was found that directly milling with a small amount of the Nb2O5 additive exerted a negligible effect on the dehydrogenation kinetics of the 2LiBH4–MgH2 composite in the first cycle. However the recycled sample showed notable property advantages over the neat 2LiBH4–MgH2 composite. Phase/chemical state analyses and control experiments were conducted to gain insight into the chemical transformation of the Nb-containing species. It was found that the Nb2O5 additive reacted with LiBH4 to form a niobium boride (NbB2) heterogeneous nucleation agent, via a niobium hydride (NbH2) intermediate, in the dehydrogenation process of the composite sample. The retarded formation of the NbB2 is a major mechanistic reason for the observed drastic property change of the composite upon cycling. As a solution, we employed a novel three-step method to controllably promote the formation of the targeted NbB2 species and improve its dispersion state. As expected, the 2LiBH4–MgH2–0.08Nb2O5 composite sample, prepared using the new method, exhibits rapid dehydrogenation kinetics and high cyclic stability, which compare favorably with the literature results of the 2LiBH4–MgH2 composites with transition metal additives. [ABSTRACT FROM AUTHOR]

Understanding the mechanism of the insulator-metal transition (IMT) in VO2 is a necessary step in optimising this material's properties for a range of functional applications. Here, Rietveld refinement of synchrotron X-ray powder diffraction patterns is performed on thermochromic V1-xWxO2 (0.0 ≤ x ≤ 0.02) nanorod aggregates over the temperature range 100 ≤ T ≤ 400 K to examine the effect of doping on the structure and properties of the insulating monoclinic (M1) phase and metallic rutile (R) phase. Precise measurement of the lattice constants of the M1 and R phases enabled the onset (Ton) and endset (Tend) temperatures of the IMT to be determined accurately for different dopant levels. First-principles calculations reveal that the observed decrease in both Ton and Tend with increasing W content is a result of Peierls type V-O-V dimers being replaced by linear W-O-V dimers with a narrowing of the band gap. The results are interpreted in terms of the bandwidth-controlled Mott-Hubbard IMT model, providing a more detailed understanding of the underlying physical mechanisms driving the IMT as well as a guide to optimising properties of VO2-based materials for specific applications.

First-principles calculations and the method of climbing-image nudged elastic band were used to investigate the effects of Mo alloying on the structural stability, mechanical properties, and hydrogen-diffusion behavior in the Nb 16 H phase. The Nb 12 Mo 4 H phase (26.5 at% Mo) was found to be the most thermodynamically stable structure, with a low Δ H f value (-0.26 eV) and high elastic modulus. Calculations revealed that the tetrahedral interstitial site (TIS) was the predominant location of H in both Nb 16 H and Nb 12 Mo 4 H phases. The calculated H-diffusion energy barrier and the diffusion coefficient of the Nb 12 Mo 4 H phase were 0.153 eV and 5.65 × 10 -6 cm 2 s -1 (300 K), respectively, which suggest that the addition of Mo would lead to a lower energy barrier and high diffusion coefficients for the Nb 16 H phase, thus improving the hydrogen-permeation properties of Nb metal., Competing Interests: None., (This journal is © The Royal Society of Chemistry.)