Understanding the effects of different microstructural contributions in the electrochemical response of Nickel-based semiconductor electrodes with 3D hierarchical networks shapes

Fabrication of Bi2MoO6 Nanosheets/TiO2 Nanorod Arrays Heterostructures for Enhanced Photocatalytic Performance under Visible-Light Irradiation

Bi2MoO6/TiO2 heterostructures (HSs) were synthesized in the present study by growing Bi2MoO6 nanosheets on vertically aligned TiO2 nanorod arrays using a two-step solvothermal method. Their morphology and structure were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Excellent visible-light absorption was observed by UV-Vis absorption spectroscopy, which was attributed to the presence of the Bi2MoO6 nanosheets with a narrow-band-gap. The specific surface area and pore volume of the photocatalysts were significantly increased due to the hierarchical structure composed of Bi2MoO6 nanosheets and TiO2 nanorods. The photoluminescence and photoelectrochemical characterizations showed improved separation and collection efficiency of the Bi2MoO6/TiO2 HSs towards the interface charge carrier. The photocatalytic analysis of the Bi2MoO6/TiO2 HSs demonstrated a significantly better methylene blue (MB) degradation efficiency of 95% within 3 h than pristine TiO2 nanorod arrays under visible-light irradiation. After three photocatalytic cycles, the degradation rate remained at ~90%. The improved performance of the Bi2MoO6/TiO2 HSs was attributed to the synergy among the extended absorption of visible light; the large, specific surface area of the hierarchical structure; and the enhanced separation efficiency of the photogenerated electron-hole pairs. Finally, we also established the Bi2MoO6/TiO2 HSs band structure and described the photocatalytic dye degradation mechanism. The related electrochemical analysis and free-radical trapping experiments indicated that h+, ·O2- and ·OH have significant effects on the degradation process.

Oxalate-derived porous prismatic nickel/nickel oxide nanocomposites toward lithium-ion battery

NiO is a highly appealing anode material for lithium-ion batteries (LIBs) owing to its relatively high Li storage capacity. However, its low electrical conductivity and large volume change during the battery cycling process limit its application. Here, we fabricate a series of porous Ni/NiO (M) nanocomposites through the direct pyrolysis of a nickel oxalate precursor and adjust the Ni(0) content by varying the pyrolysis temperature. The porous architecture is beneficial for alleviating the volume expansion/constriction during cycling. The Ni in the composites accelerates the electrochemical reaction kinetics and enhances the conductivity of the electrode materials. The M-2 electrode with a 17.9% Ni(0) content realizes a high reversible capacity (633.7 mA h g^-1 after 100 cycles at 0.2 A g^-1) and exhibits outstanding rate capability (307.6 mA h g^-1 after 250 cycles at 1 A g^-1). This work can not only supply an approach to adjust the content of an element with specific valence state, but also provide an inspiration for the fabrication of porous metal/metal oxide anode materials in LIBs.