Porous NiO nanoflowers and nanourchins: Highly active catalysts for toluene combustion

The NiO samples (NiO-HMTA, NiO-HMTA-PEG, NiO-HMTA-PVP, and NiO-urea, respectively) with a surface area of 31 −66 m2/g and porous nanoflower- and nanourchin-like morphologies were prepared via the hydrothermal route with hexamethylenetetramine (HMTA) or urea as precipitator in the absence or presence of surfactant (poly(ethylene glycol) (PEG) or polyvinyl pyrrolidone (PVP)). It is shown that NiO-HMTA-PVP possessed the highest surface area and Oads concentration and the best reducibility. The NiO-HMTA-PVP catalyst performed the best (T50% = 253 °C and T90% = 266 °C). The excellent catalytic activity of NiO-HMTA-PVP was associated with its large surface area, high Oads concentration, and good reducibility.

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► NiO nanoflowers and nanourchins are prepared by the hydrothermal method.
► NiO nanoflowers and nanourchins show a surface area of 31–66 m2/g.
► NiO nanoflower derived with PVP is high in Oads content and good in reducibility.
► NiO nanoflower derived with PVP performs excellently for toluene combustion.
► High surface area and Oads content and good reducibility governs catalytic activity.