Dealloying of Cobalt from CuCo Nanoparticles under Syngas Exposure

Abstract

The structure and composition of core–shell CuCo nanoparticles were found to change as a result of cleaning pretreatments and when exposed to syngas (CO + H2) at atmospheric pressure. In situ X-ray absorption and photoelectron spectroscopies revealed the oxidation state of the particles as well as the presence of adsorbates under syngas. Transmission electron microscopy was used for ex situ analysis of the shape, elemental composition, and structure after reaction. The original core–shell structure was found to change to a hollow CuCo alloy after pretreatment by oxidation in pure O2 and reduction in pure H2. After 30 min of exposure to syngas, a significant fraction (5%) of the particles was strongly depleted in cobalt giving copper-rich nanoparticles. This fraction increased with duration of syngas exposure, a phenomenon that did not occur under pure CO or pure H2. This study suggests that Co and Cu can each individually contribute to syngas conversion with CuCo catalysts.