Surface engineered active Co3+ species in alkali doped Co3O4 spinel catalyst with superior O2 activation for efficient CO oxidation

Abstract

CO oxidation is one of the most extensively investigated fields of research as it takes prime importance in environmental fortification and is highly challenging to explore efficient heterogeneous catalysts to achieve effectual conversion. In the present work, Co3O4 and alkali metal-doped Co3O4 spinel materials were obtained by the co-precipitation method and employed as suitable catalysts for CO oxidation. The catalysts were prepared by calcining the precipitated hydroxides of Co at 300°C, and 800°C (with and without the presence of water vapor) in the air atmosphere. The synthesized materials were characterized by powder X-ray diffraction, N2-sorption analysis, H2-TPR, SEM, and XPS techniques. Then the catalytic activity of catalysts is evaluated for CO oxidation using molecular O2 as an oxidizing agent. The effect of thermal treatment and also the role of alkali metal in CO oxidation are studied. The promotional effect of alkali (Li, Na, and K) in Co3O4 materials was observed with higher CO conversion, where the influence of Li ions in the Co3O4 catalyst was far greater than in other doped catalysts. Definite characteristics, nature of alkali-doped catalysts, and oxidative influence involved in CO oxidation reaction mechanism were carefully studied. In a general perspective, this work shows the influence of surface properties of alkali ion-doped Co3O4 spinel catalysts that consequently control the reactivity toward CO oxidation.