Electrochemical characterization of cobalt phases onto alumina supported cobalt catalyst

Abstract

This work describes the possible application of cyclic voltammetry (CV) for obtaining information about cobalt phases onto alumina supported cobalt catalysts.Starting from the same amount of ingredients, two catalysts with different phases of cobalt were prepared: Co3O4-A obtained by manual grinding of Co3O4 and alumina in an agate mortar and CoAl2O4-A obtained mechanochemically using a planetary ball mill.The final productswere characterized by the temperature-programmed reduction (TPR) and CV. The TPR profile of Co3O4-A showed peaks between 200–500°C characteristic of Co3O4 reduction, while the profile of CoAl2O4-A was altered in the whole temperature region and especially by the appearance of new peaks in the region of temperatures of 600–900oC.This result indicated that a certain amount ofhard-to-reduce cobalt aluminate is generated during milling. CVin alkaline solution revealed that theoxidation/reduction of cobalt in CoAl2O4-Aoccurred at more negative potentials compared with cobalt in Co3O4-A.Negative shift of peak potential well correlated with the appearance of high-temperature TPR peak and could be ascribed to the cobalt phase which has lower tendency to get reduced. These findings encourage the idea of using the CV as low cost and rapid assay for distinguishing the cobalt phases onto alumina.