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Abstract: The Nb-doped WO3 films were deposited by e-beam co-evaporation method using ceramic WO3 targets and metal Nb slugs. The films were analyzed by glancing incident angle X-ray diffraction (GIAXRD), UV/visible spectrophotometer, electrochemical cyclic voltammetry, X-ray photoelectron spectroscopy (XPS). The as-prepared film is brown and amorphous in structure. The film has low transmission in optical visible region. The XPS results indicate that the as-deposited film is non-stoichiometric. By applying a negative potential, the as-deposited film does not show obvious electrochromic effect. However, the electrochromic properties of Nb-doped WO3 films are improved by post annealing treatment at 350, 400, and 450°C in oxygen atmosphere. The Nb-doped WO3 films transform into crystalline structure and become transparent after post annealing treatment. The energy band gap, optical modulation, and color efficiency increase with annealing temperature. [Copyright &y& Elsevier]

Hydrogen has been considered as one of the most promising renewable energy for production and storage. Here, we report an efficient method to synthesize MoS 2 -MoO 2 composite by hot-injection method using MoO 3 and S powder as precursors with oleic acid (OA) and oleylamine (OLA) as solvent, respectively. The X-ray diffraction shows the presence of the peaks from both MoS 2 as well as MoO 2 . With increasing reaction temperature and time, oleic acid reorganizes the octahedral units of MoO 3 and gradually turn into low valence of Mo. After injecting S-precursor, OLA first reduces Mo-precursor to MoO 2 as core, and then S atoms replace O atoms to form MoS 2 as shell, eventually forming MoS 2 -MoO 2 core-shell structure. MoO 2 with few-layer MoS 2 can be observed by transmission electron microscope. A Tafel slope of 129 mV/dec is obtained for MoS 2 -MoO 2 composite, which is much better than MoS 2 and MoO 2 . The enhanced HER performance is attributed to the abundance active sites from MoS 2 and the improved charge transfer direction by MoO 2 . [ABSTRACT FROM AUTHOR]