In Situ Scanning Transmission Electron Microscopy Calcination of Palladium Nitrate Supported on Zinc Oxide

Metallic nanoparticles are essential materials in various applications, such as nanomedicine, nanotechnology, and catalysis. While it is known that their catalytic performance is determined by their microstructure and thus by their preparation, the influence of an important but commonly used calcination treatment during nanoparticle preparation on their properties is often overlooked. Herein, structural and morphological changes during the calcination of Pd(NO3)2/ZnO are studied systematically by performing in situ heating experiments mimicking typical preparation conditions, by employing environmental scanning transmission electron microscopy. The effect of different calcination parameters on Pd(NO3)2/ZnO is explored and guidance to enhance control over the preparation of small supported nanoparticles is provided. It is shown that a calcination treatment of Pd(NO3)2/ZnO between 200 and 400 °C for 15-120 min is ideally suited to obtain particles smaller than 4 nm with a narrow size distribution.