Structural and electrocatalytic properties of molten core Sn@SnOx nanoparticles on ceria

The morphological and chemical modifications following reduction in hydrogen at 873 K of stannic oxide deposited on ceria particles were studied in order to gain insights into the nature of Ce-Sn interaction under reducing atmosphere, simulating the operating conditions in a solid oxide fuel cell. It is shown that the co-presence of the two materials improves the power output of fuel cells up to a factor of 10 when compared to ceria alone. Through high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and in-situ X-ray diffraction (XRD) data we show the formation of a novel system made up of nanoparticles composed of a molten Sn-0 core capped by an amorphous tin oxide layer. SnOx shell acts as a binding agent which stabilizes Sn-0 nanoparticles on ceria even after reductive treatment at temperatures well above the melting point of tin. This occurs through an interfacial redox communication between ceria and tin, likely involving a transfer of oxygen from ceria to the metal and electrons from metal to ceria. It is highlighted how the Sn@SnOx nanostructures and their spontaneous formation could be used as a model for the development of catalyst nano-assembly comprising an amorphous metal oxide triple phase boundary, opening the way for a new paradigm in the development of multifunctional catalytic systems. (C) 2016 Elsevier B.V. All rights reserved.