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Gamma radiation can cause structural defects in metal oxide thin films, affecting their conversion efficiency. This study focuses on synthesizing and characterizing Tungsten oxide (WO3) films for photo-electrochemical (PEC) water-splitting applications. The pristine WO3 film was irradiated with a Co-60 gamma source to improve its photocatalytic activity and was named G-WO3. The resulting G-WO3 thin films showed a decrease in the optical direct band gap and showed higher photocurrent density and lower charge transfer resistance for PEC applications. The carrier charge density (Nd) values were found to be increased after γ-radiation. The synthesized G-WO3 thin films possess good stability and reusability for photo-electrochemical water-splitting applications. [ABSTRACT FROM AUTHOR]

In this study, influence of Al substitution on hydrogen storage properties of Ti2CrV alloy has been investigated in detail. The alloys Ti2–xCrVAlx (x = 0.05, 0.1) were synthesized by arc melting method, and composition, type of crystal structure and hydrogen storage properties were evaluated. X-ray diffraction studies confirmed that all the alloys form single-phase bcc structures. Ti1.95CrVAl0.05 alloy is found to absorb a maximum of 3.9 wt% of hydrogen at room temperature and moderate hydrogen pressure. The plateau pressure of the studied alloys increases with an increase in Al concentration. The results confirm that among the studied alloys, Ti1.95CrVAl0.05 alloy shows the fastest hydrogen absorption kinetics and improved cyclic stability with a marginal decrease in total hydrogen absorption capacity compared to the parent alloy. [ABSTRACT FROM AUTHOR]

A analogous series of 2-(3,5-dimethylpyrazol-1-yl)phenyl substituted selenoether complexes of palladium [PdCl2(RSeC6H4dmpz)]; (R = CH2COOH (1), CH2CH2COOH (2), and CH2CH2OH (3); dmpz = dimethylpyrazole) were ably synthesized in a facile manner and exhaustively characterized. Insight into molecular structures of these complexes was keenly probed through single crystal X-ray diffraction (XRD) analysis, unfolding the structural scaffolds and laying into molecular aggregation, availed through hydrogen bonding interactions borne out of tethered protic groups. The complexes were converted to capping free palladium selenide (Pd17Se15) nanoparticles through pyrolysis and evaluated for their electrocatalytic efficacy towards the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER) and methanol oxidation reaction (MOR) in alkaline medium. In an alkaline medium, PSNP1 (Pd17Se15) obtained from the hydrogen bonded aggregate of complex PdCl2L1 (1) produced good HER activity. PSNP1 had a little decrease in current density after 300 continuous cycles, which proves that the catalyst presents high stability in the recycling process. For the electrocatalytic oxidation of CH3OH, the electrocatalytic rate constant (k) obtained was 0.3 × 103 cm3 mol−1 s−1. [ABSTRACT FROM AUTHOR]

Summary: Magnesium is one of the potential candidates for on‐board hydrogen storage, but slow hydrogenation kinetics and unfavourable thermodynamics limits its practical implementation. To improve the hydrogenation characteristics, nanocrystalline magnesium was prepared by a simple wet milling method without addition of heavy metal catalyst. Compared to micro‐crystalline Mg, developed nanocrystalline Mg exhibits improved hydrogen storage properties showing extended plateau region in the pressure‐composition‐temperature curves with higher hydrogen storage capacity (6.24 wt% at 300°C). Hydrogenation and dehydrogenation kinetics is found to follow Kolmogorov−Johnson−Mehl−Avrami activation energy model confirming the involvement of nucleation‐growth‐impingement mechanism. Prolonged ball milling leads to quite fast hydrogenation kinetics (upto 90% of the saturation value in 15.5 minutes at 250°C) and leads to substantial decrease in the activation barrier. The activation energy for hydrogenation is found to be 68.88 kJ mol−1 for 8 hours ball milled sample. Present study established a simple and scalable method for nanocrystalline Mg, which can undergo reversible hydrogen absorption and desorption with improved performance without using any additional catalyst. [ABSTRACT FROM AUTHOR]

In this study, Bi3+ incorporation in NaYbF4:Er lattice and its influence on upconversion luminescence properties have been investigated in detail using techniques such as temperature‐dependent luminescence, Fourier transform infrared spectroscopy and X‐ray diffraction (XRD). The study was carried out to develop phosphors with improved upconversion luminescence. From photoluminescence and lifetime measurements it is inferred that luminescence intensity from NaYbF4:Er increases with Bi3+ addition. The sample containing 50 at.% Bi3+ ions exhibited optimum upconversion luminescence. Increased distance between Yb3+–Yb3+ and Er3+–Er3+ due to Bi3+ incorporation into the lattice and associated decrease in the extent of dipolar interaction/self‐quenching are responsible for increase in lifetime values and luminescence intensities from Er3+ ions. Incorporation of Bi3+ into NaYbF4:Er lattice reduced self‐quenching among Yb3+–Yb3+ions and this facilitated energy transfer from Yb3+ to Er3+. This situation also explains decrease in the extent of temperature‐assisted quenching of emission from thermally coupled 2H11/2 and 4S3/2 levels of Er3+. Based on Rietveld refinement of XRD patterns it was confirmed that a maximum of 10 at.% of Bi3+added was incorporated into the NaYbF4:Er lattice and the remaining complex co‐exists as a BiOF phase. These results are of significant interest in the area of development of phosphors based on Yb3+–Er3+ upconversion luminescence. [ABSTRACT FROM AUTHOR]

Zr substituted Ti 2 CrV alloy with Ti 0.43 Zr 0.07 Cr 0.25 V 0.25 composition was synthesized by arc melting method and its crystal structure, microstructure and hydrogen storage performance were investigated. XRD and microstructural analyses confirmed that the alloy forms Laves phase related BCC solid solution. The enthalpy of hydride formation as derived from pressure composition absorption isotherms is −56.33 kJ/mol H 2 . The desorption temperature of the hydride is significantly lower (by ∼50 K) than that of Ti 2 CrV hydride indicating lower thermal stability of the hydride compared to its unsubstituted analogue. The alloy shows better cyclic stability over the unsubstituted one. This work also offers mechanistic insight into hydrogen absorption reaction of Ti 0.43 Zr 0.07 Cr 0.25 V 0.25 alloy by analyzing the hydriding kinetics data with standard kinetic models. The rate-determining steps of hydrogen absorption reaction were identified as random nucleation and growth of hydride followed by 1D and 3D diffusion of hydrogen atoms through the hydride layer. The present study is expected to provide valuable information for the better development of Ti–Cr–V based hydrogen storage alloys. [ABSTRACT FROM AUTHOR]

Zr 2− x Ti x Ni ( x = 0.0, 0.3, 0.7, 1.0) alloys were prepared by arc melting method. The effect of Ti substitution in Zr site has been investigated in the perspective of both microstructural evolution and hydriding properties. The as-prepared Zr 2 Ni alloy exists as tetragonal C16 phase and Ti substituted alloys show mixed phase structure. The pressure-composition isotherms (PCI) revealed that with increase in Ti content, the equilibrium plateau pressure increases whereas the hydrogen uptake decreases. All the alloys absorb hydrogen without any incubation period. The rate of hydriding reaction decreases with incorporation of Ti and this is in agreement with the activation energy ( E a ) values calculated using the modified KJMA model. [ABSTRACT FROM AUTHOR]

Highlights: [•] Hydrogen absorption behaviour of Ti0.67Nb0.33−xFe x alloys were studied. [•] Ti0.67Nb0.13Fe0.20 show maximum hydrogen uptake with fastest kinetics. [•] Hydrogenation of Ti0.67Nb0.13Fe0.20 proceeds by two different rate determining steps. [•] Electronic charge density around Fe nuclei changes on hydrogen absorption. [Copyright &y& Elsevier]

This paper deals with hydrogen storage properties of Ti-V based BCC solid solution incorporated with Fe. The alloy with composition Ti2FeV was prepared by arc melting method. X-ray diffraction (XRD) and energy dispersive X-ray analysis studies confirmed formation of solid solution phase with uniform composition and BCC structure. SEM studies revealed the formation of irregular shaped particles with size in the range of few microns up on hydrogenation of the parent alloy. The alloy shows maximum hydrogen storage capacity of 3.41 wt.% at 20 bar and 303 K and the thermodynamic parameters established near room temperature suitability of the alloy for solid state hydrogen storage applications. Hydrogenation kinetics is found to be quite fast and detailed kinetic analysis were done to underscore the hydrogenation mechanism. Activation energy during the initial stage of hydrogenation is found to be 30.8 kJ/mol. The value decreases to 14.4 kJ/mol for extended duration of hydrogenation, and this is explained based on difference in rate determining steps existing at different time scales. Extent of hydrogen absorption as a function of temperature and time for Ti2FeV alloy. [ABSTRACT FROM AUTHOR]

A analogous series of 2-(3,5-dimethylpyrazol-1-yl)phenyl substituted selenoether complexes of palladium [PdCl 2 (RSeC 6 H 4 dmpz)]; (R = CH 2 COOH (1), CH 2 CH 2 COOH (2), and CH 2 CH 2 OH (3); dmpz = dimethylpyrazole) were ably synthesized in a facile manner and exhaustively characterized. Insight into molecular structures of these complexes was keenly probed through single crystal X-ray diffraction (XRD) analysis, unfolding the structural scaffolds and laying into molecular aggregation, availed through hydrogen bonding interactions borne out of tethered protic groups. The complexes were converted to capping free palladium selenide (Pd 17 Se 15 ) nanoparticles through pyrolysis and evaluated for their electrocatalytic efficacy towards the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER) and methanol oxidation reaction (MOR) in alkaline medium. In an alkaline medium, PSNP1 (Pd 17 Se 15 ) obtained from the hydrogen bonded aggregate of complex PdCl 2 L 1 (1) produced good HER activity. PSNP1 had a little decrease in current density after 300 continuous cycles, which proves that the catalyst presents high stability in the recycling process. For the electrocatalytic oxidation of CH 3 OH, the electrocatalytic rate constant ( k ) obtained was 0.3 × 10 3 cm 3 mol -1 s -1 .

In this study, Bi 3+ incorporation in NaYbF 4 :Er lattice and its influence on upconversion luminescence properties have been investigated in detail using techniques such as temperature-dependent luminescence, Fourier transform infrared spectroscopy and X-ray diffraction (XRD). The study was carried out to develop phosphors with improved upconversion luminescence. From photoluminescence and lifetime measurements it is inferred that luminescence intensity from NaYbF 4 :Er increases with Bi 3+ addition. The sample containing 50 at.% Bi 3+ ions exhibited optimum upconversion luminescence. Increased distance between Yb 3+ -Yb 3+ and Er 3+ -Er 3+ due to Bi 3+ incorporation into the lattice and associated decrease in the extent of dipolar interaction/self-quenching are responsible for increase in lifetime values and luminescence intensities from Er 3+ ions. Incorporation of Bi 3+ into NaYbF 4 :Er lattice reduced self-quenching among Yb 3+ -Yb 3+ ions and this facilitated energy transfer from Yb 3+ to Er 3+ . This situation also explains decrease in the extent of temperature-assisted quenching of emission from thermally coupled 2 H 11/2 and 4 S 3/2 levels of Er 3+ . Based on Rietveld refinement of XRD patterns it was confirmed that a maximum of 10 at.% of Bi 3+ added was incorporated into the NaYbF 4 :Er lattice and the remaining complex co-exists as a BiOF phase. These results are of significant interest in the area of development of phosphors based on Yb 3+ -Er 3+ upconversion luminescence., (© 2019 John Wiley & Sons, Ltd.)