The evolution of the phase and morphology of FeOOH nanorods prepared by a hydrothermal method is studied via X-ray diffraction (XRD) and in situ transmission electron microscopy. The FeOOH nanorod with a tetragonal structure (β-FeOOH) is gradually converted into a rhombohedral FeO nanorod by a simple thermal treatment. The existence of an intermediate FeOOH structure with high lattice strains during the phase transition is identified by Rietveld analysis using XRD. The electrochemical properties of the nanorods are investigated based on the crystal phases to elucidate their relative catalytic activities. The strained-FeOOH nanorods exhibited enhanced catalytic water oxidation activity and stability. Typically, the strained-FeOOH nanorods showed high electrochemical stability under neutral conditions, while tetragonal FeOOH nanorods under the same conditions showed rapid deactivation for water oxidation reaction.
We investigated feasibility of a compact, low-cost, laser-induced breakdown spectroscopy (LIBS) device made up of a Q-switched, diode-pumped, solid-state laser and a nongateable miniature spectrometer for the classification of edible salts. LIBS spectra of edible salts from 12 different geographic origins were obtained by this compact LIBS device. The detection limits of the compact LIBS device for potassium, magnesium, and calcium with effective discrimination power were sufficient to classify the edible salts. The classification model was developed by the multivariate analysis of the LIBS spectra. The comparison of the LIBS results with inductively coupled plasma-atomic emission spectroscopy analysis indicates that the clustering of principal component scores was well dominated by chemical compositions of the salts. The cross-and external validations of the classification model showed reasonable performance (98.3 and 87.5% correctness, respectively). Our results indicate that rapid classification of edible salts can be realized by a compact, low-cost LIBS device.
Controllable synthesis of graphene-coated metal nanoparticles (NPs) presents a major challenge when considering the practical application of these catalysts. Herein, we use silica as a radical sieve to grow graphene...
Transition-metal phosphides have gained great importance in the field of energy conversion and storage such as electrochemical water splitting, fuel cells, and Li-ion batteries. In this study, a rationally designed novel fluffy graphene (FG)wrapped monophasic Ni 5 P 4 (Ni 5 P 4 @FG) is in-situ-synthesized using a chemical vapor deposition method as a Li-ion battery anode material. The porous and hollow structure of Ni 5 P 4 core is greatly helpful for lithium-ion diffusion, and at the same time, the cilia-like graphene nanosheet shell provides an electron-conducting layer and stabilizes the solid electrolyte interface formed on the Ni 5 P 4 surface. The Ni 5 P 4 @FG sample shows a high reversible capacity of 739 mAh g −1 after 300 cycles at a specific current density of 500 mA g −1 . The high capacity, superior cycling stability, and improved rate capability of Ni 5 P 4 @FG are ascribed to its unique hierarchical structure. Moreover, the present efficient fabrication methodology of Ni 5 P 4 @FG has potential to be developed as a general method for the synthesis of other transition-metal phosphides.
A well-defined WO 3 /Bi 2 S 3 composite comprised of single-crystalline Bi 2 S 3 nanowire (Bi 2 S 3 NW) layers on top of the WO 3 nanoparticles (WO 3 NP) was synthesized via an in situ hydrothermal reaction. The single-crystalline Bi 2 S 3 nanowires were uniformly grown on the surface of the WO 3 nanoparticle layer. This in situ hydrothermal process is also a general route for the synthesis of well-aligned Bi 2 S 3 nanowires on various metal oxide substrates, such as TiO 2 , BiVO 4 , and ZnO. Compared to the sole Bi 2 S 3 electrode, the resulting WO 3 NP/Bi 2 S 3 NW composite showed enhanced photoelectrochemical activity. The origin of this enhanced activity is mainly attributed to the enhancement of charge separation on the Bi 2 S 3 layer, due to the effective photogenerated electron transfer from the Bi 2 S 3 conduction band to that of WO 3 . Furthermore, the single-crystalline longitudinal structure of the Bi 2 S 3 nanowires can provide a direct electrical pathway through a single domain of nanowires.
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