Résumé
The phases formed by alkaline precipitation of Ni(OH)2 at different temperatures and different levels of carbonate and nitrate anions have been characterized by X-ray diffraction, elemental analysis, FTIR spectroscopy, TG-MS, N2 physisorption and cyclic voltammetry. The dehydration-deanionization of alpha- to beta-Ni(OH)2 passes through an interstratified intermediate IS-Ni(OH)2, which can be stabilized at 80 degrees C in the presence of carbonates. IS-Ni(OH)2 materials have been prepared with CO32-/Ni2+ ratio ranging from 0.05 to 0.16, resulting in different ratios of interstratified alpha and beta phase layers. IS-Ni(OH)2, thermally stable up to 200 degrees C, presents a peculiar ink-bottle mesoporosity and surface area higher than 100 m2 g-1. The material is promising for electrocatalytic applications on the basis of the textural properties and a reproducible reduction potential of 0.37 V versus SCE. The easily reversible reducibility of Ni2+ is also shown by the TG-MS of the thermal dehydroxylation-deanionization to NiO, evidencing transient Ni3+ species formed by reaction with NOx emitted from the decomposition of nitrates.