Effects of the preparation procedure and additives on surface texture of nickel and cobalt oxides as final decomposition products of nickel and cobalt oxysalts

Abstract

The effects of preparation procedure and readily decomposable salt additives, namely (NH 2 ) 2 CO and NH 4 NO 3 , on the texture of NiO and Co 3 O 4 produced by calcination of Ni(NO 3 ) 2 ·6H 2 O and Co(NO 3 ) 2 ·6H 2 O were investigated. Textural characteristics were assessed via analysis of nitrogen adsorption isotherms, using a number of widely-accepted methods. The thermal genesis courses of NiO and Co 3 O 4 , from additive-containing and additive-free oxide precursors were explored using thermogravimetry, differential thermal analysis and X-ray diffractometry (XRD). The results of surface texture and XRD analyses were largely in agreement and showed that pores are modified. An impregnation procedure using salt additives to NiO and Co 3 O 4 resulted in a marked increase of surface area (from 23 to 65 m 2 g −1 for NiO and from 18 to 82 m 2 g −1 for Co 3 O 4 ). This increase is most likely due to the evolved gases and the consequent fragmentation of particles and the widening of pores.