A simple one-pot thermal decomposition approach to the selective synthesis of NiO nanomaterials was developed. The morphologies of the NiO nanomaterials were nanoparticle-based sheets, octahedra, nanosheet-built agglomerates, and nanoparticle-based microspheres. The samples were characterized by field-emission scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and N-2 adsorption analyses. The morphology, crystal size, and texture properties of the products can be easily modulated by selecting various decomposition temperatures and precursors. Samples with high specific surface area and small crystal size were found to easily form at low sintering temperatures and when basic nickel carbonate and nickel oxalate dihydrate were used as precursors. Reduction property and CH4 conversion, as functions of decomposition temperature and precursor type, were systematically investigated. When NiCO3 center dot 2Ni(OH)(2)center dot 4H(2)O and NiC2O4 center dot 2H(2)O were used as precursors, the as-obtained nanosheet-built agglomerates and nanoparticle-based sheets presented a high CH4 conversion rate because of the small crystal size and large specific surface area. (C) 2015 Elsevier B.V. All rights reserved.