Synthesis and Structural Evolution of Nickel-Cobalt Nanoparticles Under H₂and CO₂

Abstract

Bimetallic nanoparticle (NP) catalysts are interesting for the development of selective catalysts in reactions such as the reduction of CO2 by H2 to form hydrocarbons. Here the synthesis of Ni-Co NPs is studied, and the morphological and structural changes resulting from their activation (via oxidation/reduction cycles), and from their operation under reaction conditions, are presented. Using ambient-pressure X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and transmission electron microscopy, it is found that the initial core-shell structure evolves to form a surface alloy due to nickel migration from the core. Interestingly, the core consists of a Ni-rich single crystal and a void with sharp interfaces. Residual phosphorous species, coming from the ligands used for synthesis, are found initially concentrated in the NP core, which later diffuse to the surface.

Thermal Stability of Core–Shell Nanoparticles: A Combined in Situ Study by XPS and TEM

“…36 . Ni-Co core-shell NPs and hexane were mixed using an ultrasonic bath for 2 minutes until the solid NPs were well dispersed in hexane.…”

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.…”

Supported Porous Nanomaterials as Efficient Heterogeneous Catalysts for CO2 Fixation Reactions

“…Oxides of all these reactive metals can be dispersed on microporous or mesoporous supports to yield a rich spectrum of heterogeneous catalysts and often their surface acidity/basicity play crucial role in the CO 2 fixation reactions. Bimetallic Ni–Co NPs supported over mesoporous silica MCF‐17 showed catalytic reduction of CO 2 to a mixture of CO (70 %), HCHO (20 %) and CH 3 OH (10 %) at 350 °C; in this system surface alloying due to the migration of Ni from the core to shell nanostructure could be responsible for this selectivity pattern …”