Self-template synthesis of nickel silicate and nickel silicate/nickel composite nanotubes and their applications in wastewater treatment

Hierarchical one-dimensional (1D) hollow nanostructures have attracted intense research attention due to their unique structures that may be capable of many promising applications. Here, we report a facile and effective strategy to prepare nickel silicate nanotubes (NiSNTs). Using this approach, mesoporous SiO2 nanorods served as sacrificial templates for a simple hydrothermal process to prepare NiSNTs via a self-template route. The obtained NiSNTs preserve the tubular hierarchical morphology and hollow interior structures, which confer the NiSNTs with high surface areas and large pore volumes. These features point to NiSNTs as superior candidates for efficiently adsorbing heavy metal ions and organic dyes in wastewater. Moreover, NiSNTs can also serve as both supports and nickel sources, forming nickel silicate/nickel nanocomposite tubes (NiSNTs/Ni) via in situ reduction of NiSNTs under hydrothermal conditions. The addition of nickel precursors and surface pre-activation are therefore unnecessary. The NiSNTs/Ni exhibit efficient and recyclable catalytic properties when used for the reduction of 4-nitrophenol (4-NP). With a rational adaption, we believe this synthetic strategy can be extended to fabricate multifunctional one-dimensional hollow nanostructures with diverse compositions and morphologies, which may be useful for environmental protection, catalysis, energy and many other important domains.