Dealloying of Cobalt from CuCo Nanoparticles under Syngas Exposure

Abstract

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 + H 2 ) 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 O 2 and reduction in pure H 2 . 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 H 2 . This study suggests that Co and Cu can each individually contribute to syngas conversion with CuCo catalysts.

Tuning Complex Transition Metal Hydroxide Nanostructures as Active Catalysts for Water Oxidation by a Laser–Chemical Route

“…Overpotentials required to achieve j = 10 mA cm -2 for different catalysts at initial (η t=0 ) and after 2h operation (η t=2h ) are listed. valence states of the metals are denoted along with small variations ( x , 0<<1), ascribed to the spectra based on XAS of well-studied oxides and minerals [13][14][15] . Note that the total electron yield (TEY) mode of soft XAS is surface sensitive (with probing depth of ~ 5 nm), and the fluorescence yield (FY) mode (with probing depth of ~ 50 nm) was also performed, where the valence states probed by the two modes showed subtle differences.…”

The Active State of Supported Ruthenium Oxide Nanoparticles during Carbon Dioxide Methanation

“…While this pressure is still below the typical operating pressure for the Sabatier reaction (1 bar), it is high enough to ensure the saturation of surface sites with adsorbates, thus making the measurement representative of the surface steady state in the catalytic reactor. This was demonstrated on a number of metal and metal oxide catalysts in the past ten years and by several groups, [19][20][21][22][23][24][25][26][27][28] and in particular for the reaction of catalytic CO oxidation on bulk ruthenium oxide. 29 It is more challenging but still possible to analyze surface ligands and adsorbates on nanoparticles.…”

Remarkably efficient CoGa catalyst with uniformly dispersed and trapped structure for ethanol and higher alcohol synthesis from syngas

“…Another challenge arises from the poor stability of Co-based catalysts, which generally results from the sintering of the active phase. The agglomeration could also lead to phase separation, which is regarded as the main cause for the decrease in selectivity to alcohols or higher alcohols [42][43][44][45]. Except for the report that the copper and cobalt located in the well-defined perovskite structure with a slit-shaped space between nanoparticles improve the stability [46], this remains an issue until now.…”