Synthesis and characterization of Cu–Co–Fe hydrotalcites and their calcined products

Abstract

A series of new Cu–Co–Fe compounds with the general formula Cu x Co2−x Fe1HT (x = 0, 0.5, 1, 1.5 and 2) has been prepared by hydrotalcite coprecipitation method. The presence of hydrotalcite phase is revealed by XRD analysis for x values of 0, 0.5 and 1. When the copper quantity is higher than 1, the malachite phase is preferentially formed. These results are confirmed by TG-DTA, FT-IR and XPS analysis. After calcination at 500 °C in air of all samples, XRD analysis reveals the presence of spinel phases such as Co3O4, CoFe2O4, CuFe2O4, Cu x Co y O4 in the solids, monoclinic CuO phase when the copper content is greater or equal to 1 and haematite phase for the sample where x is equal to 2. The presence of these phases is also confirmed by XPS results. For comparison, a Co2Fe1OH sample has been synthesized by classical coprecipitation method and although Co2Fe1HT sample and Co2Fe1OH form a similar phase after calcination at 500 °C, Co2Fe1HT500 presents a higher BET value than Co2Fe1OH500 sample.