Thermal Oxidation of Size-Selected Pd Nanoparticles Supported on CuO Nanowires: The Role of the CuO–Pd Interface

Abstract

The structure of heterogeneous nanocatalysts supported on metal oxide materials and their morphological changes during oxidation/reduction processes play a crucial role in determining the resulting catalytic activity. Herein, we study the thermal oxidation mechanism of Pd nanoparticles supported on CuO nanowires by combining in situ environmental transmission electron microscopy (TEM), ex situ experiments, and ab initio density functional theory (DFT) calculations. High-resolution TEM imaging assisted by geometric phase analysis enabled the analysis of partially oxidized, fully oxidized, and distinct onion-like Pd nanoparticles with subsurface dislocations. Furthermore, preferential crystalline orientations between PdO nanoparticles and the CuO nanowire support have been found. Hence, the CuO–Pd interface is crucial for the thermal oxidation of Pd nanoparticles, as corroborated by electron energy loss spectroscopy and DFT calculations. The latter revealed a considerably lower energy barrier for penetration of oxygen into the Pd lattice at the CuO–Pd interface, promoting nanoparticle oxidation. The obtained results are compared with those of literature reports on different material systems, and potential implications for catalysis and chemoresistive sensing applications are discussed.

Facile Synthesis of Pd-CuO Nanoplates with Enhanced SO2 and H2 Gas-Sensing Characteristics

“…The observation of the active mode of PdO for this sample can be explained by the formation of PdO through migration of oxygen atoms inside the Pd lattice at the Pd-CuO interface, as reported in Ref. 64 .…”

Atomic-scale structure and chemical sensing application of ultrasmall size-selected Pt nanoparticles supported on SnO2

“…66 Similarly, an epitaxial relationship between CuO nanowire supports and Pd nanoparticles after thermal oxidation has been identified, resulting from an interface-driven oxidation mechanism. 67 PdO nanoparticles epitaxially aligned to MgO substrates have also been found, but their formation was explained by PdO nanoparticle nucleation and growth enabled by Pd surface diffusion. 68,69 Furthermore, epitaxial relationships between nanoparticle and support have been observed for metallic Au 70,71 or Rh 72 catalysts after treatment at elevated temperatures.…”

NanoMaterialsCAD: Flexible Software for the Design of Nanostructures

“…Our previous experience with performing computer simulations that complement experimental work on NP design and utility in various nanodevices [ 21–25 ] has revealed the need for software that enables facile nanostructure design. Of particular significance has been the demand to reproduce surfaces and interfaces obtained from microscopy characterization of experimental samples, because of their importance in the determination of, e.g., electronic structures and chemical, magnetic, or plasmonic properties, etc.…”

“…Of particular significance has been the demand to reproduce surfaces and interfaces obtained from microscopy characterization of experimental samples, because of their importance in the determination of, e.g., electronic structures and chemical, magnetic, or plasmonic properties, etc. [ 21,22,26–28 ] With this work, we are introducing our newly developed software, NanoMaterialsCAD, [ 29 ] which caters for such needs. It is a free tool for modeling and manipulation of nanoobjects at the atomic level that provides an easy and automated way to create various kinds of crystalline structures such as nanoparticles, nanodots, nanowires, nanotubes, nanoscrolls, spatial vacuums, etc., all packed into a single integrated application.…”