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In this work, we reported the highly ordered NiCoO nanoneedle@polypyrrole arrays anchored on three-dimensional graphene (NiCoO@PPy/3D graphene) for high-sensitivity detection of trace lead ions (Pb). The 3D graphene was prepared by a hydrothermal process and then decorated with NiCoO nanoneedle arrays by another hydrothermal process. This two-step hydrothermal method is simple and mild. Furthermore, the highly conductive PPy was coated on NiCoO via a chemical vapor-phase polymerization to prepare NiCoO@PPy/3D graphene. The free-standing NiCoO@PPy/3D graphene can be directly utilized as 3D electrochemical working electrode without being decorated onto working electrode like Au and glassy carbon electrode. High conductivity, large specific surface area, short ion diffusion path and excellent adsorption capacity of NiCoO@PPy/3D graphene efficiently improved electrochemical property for the detection of Pb. Using square-wave anodic stripping voltammetry (SWASV), a linear range between the currents and the concentrations of Pb of 0.0125-0.709 μM with a high sensitivity of 115.621 μA μM was obtained. The limit of detection can reach to 0.2 nM. In addition, the fabricated sensor of Pb also had good selectivity, reproducibility and long-term stability. Finally, NiCoO@PPy/3D graphene electrode was utilized for determining Pb in tap water sample using the standard addition method, revealing a promising application for the quantitative detection of certain concentration ranges of Pb in real sample. [ABSTRACT FROM AUTHOR]

Here, a supramolecular self-assembly hydrogel was designed for SnO-based anode through electrostatic interaction and ionic bonding between poly(allylamine hydrochloride) (PAH) chain and gelator phytic acid. Microrheology measurement was employed to investigate the self-sorting mechanism of the hierarchical nanostructured PAH. Results confirmed that ionically cross-link PAH improves the structural integrity of SnO nanospheres due to the reversible ionic bonding and thus increases the lifetime of the electrodes obviously. Besides, multi-walled carbon nanotubes (MWCNTs) were applied to improve the electrochemical performance of hollow SnO nanospheres due to their high conductivity. Results confirmed that the conductive network constructed by MWCNTs reduces the polarization of the composites while increases the specific capacity of the electrodes. Attributed to the synergistic effect of PAH-60 and MWCNTs, the composite electrodes show excellent electrochemical performance with a reversible capacity of 574 mAh g after 100 cycles at 100 mA g, a discharge capacity of 321 mAh g at 2000 mA g and a spring-back capacity of 506 mAh g at 200 mA g. Additionally, the prepared composite electrodes were observed to have a complete network structure after rate capability test, demonstrating a superior structural stability. [ABSTRACT FROM AUTHOR]

In order to optimize the electrode system of lithium-ion batteries (LIBs) for problems like lithium-ion diffusion, electron transport, and large volume change during cycling processes, a novel three-dimensional (3D) hybrid FeO nanotube array anode coated by polypyrrole (FeO@PPy) is synthesized via a sacrificial template-accelerated hydrolysis method followed by a chemical vapor-phase polymerization process. In the hollow core-shell nanostructures, the conducting PPy layer could not only facilitate the electron transport, but also force the core to expand inward into the hollow space, which allows for free volume expansion of the FeO without mechanical breaking. Besides, the static outer surface is contributed to form a stable solid electrolyte interface film. As a result, the integration of 3D hybrid nanostructure electrode is capable of retaining a high capacity of 665 mA h g after 150 cycles with a coulombic efficiency of above 97 %, revealing better cycling properties compared with bare FeO nanotube arrays' anode. This nanoengineering strategy is proven to be an ideal candidate for the development of high-performance anode for LIBs. [ABSTRACT FROM AUTHOR]