Kinetics and mechanism of hydrothermally prepared copper oxide nanorod catalyzed decomposition of ammonium nitrate

One of the key aspects in the development of materials science is the synthesis of particles with specific size and morphology for catalytic applications. Nowadays, nanostructured materials with specific morphology are gaining great importance in the field of catalysis. Thin, one-dimensional, monodispersed CuO nanorods with a significantly higher aspect ratio of 5, were successfully prepared by the hydrothermal method with subsequent ultrasonication. The formation of pure monoclinic CuO nanorods was confirmed by powder XRD and SAED. The CuO nanorod growth mechanism is investigated by using TEM and further characterized by FTIR, UV–visible spectroscopy and thermogravimetry. The catalytic decomposition of ammonium nitrate, an environmental friendly rocket propellant oxidizer, over the synthesized CuO nanorods was investigated. The thermal kinetic constants for the catalytic and noncatalytic decomposition of ammonium nitrate samples were computed by using model free (differential and non-linear integral) and model fitting approaches. The catalytic influence was evident even with 1% catalyst concentration. The model fitting method suggested contracting cylinder mechanism as the effective mechanism for all the investigated samples. Apparently, the CuO nanorods provide Lewis acid and/or active metal sites, facilitating the removal of ammonium nitrate decomposition inhibition species such as NH3 and thereby enhance the rate of decomposition.

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► Monoclinic CuO nanorods with aspect ratio ∼5 were hydrothermally synthesized.
► Catalytic decomposition of ammonium nitrate in presence of CuO nanorods were studied.
► Kinetic parameters for the catalytic and noncatalytic decomposition were computed.
► Advanced model-free and model-fitting methods used to compute kinetic parameters.
► Possible removal of NH3 by surface reactions changes the decomposition pathway.