Insights into the role of carbonates and hydroxides in La-Co oxides for CO catalytic conversion

Abstract

This study investigates the mechanisms involved in the conversion of carbon monoxide (CO) to carbon dioxide (CO2) using Lanthanum Cobalt (La-Co) mixed oxide catalysts, with a focus on the pivotal role of surface entities, namely carbonates and hydroxides. A series of catalysts with varying cobalt content were synthesized and their crystalline structure was analyzed through X-ray diffraction (XRD), revealing the formation of crystalline CoO and Co3O4 phases. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were employed to observe morphological differences in the catalysts. Surface and bulk compositions were examined using Temperature-Programmed Desorption (TPD), Energy-Dispersive X-ray Spectroscopy (EDS), and X-ray Photoelectron Spectroscopy (XPS). The study found that an increase in cobalt doping does not directly correlate with enhanced catalytic activity. Nonetheless, higher cobalt doping resulted in a lower activation energy and a faster reaction rate. The research emphasizes the critical role of surface carbonates and hydroxides as basic sites facilitating CO and oxygen molecule adsorption and activation. Furthermore, mixed metal oxide catalysts, when combined with surface carbonates and hydroxides, displayed