Metal Core-Shell Nanoparticle Supercrystals: from Photo-Activation of Hydrogen Evolution to Photo-Corrosion.

Gas nanobubbles are directly linked to many important chemical reactions. While they can be detrimental to operational devices, they also reflect the local activity at the nanoscale. In this work, supercrystals made of highly monodisperse Ag@Pt core-shell nanoparticles were first grown onto a solid support and fully characterized by electron microscopies and X-ray scattering. Supercrystals were then used as a plasmonic photo-catalytic platform for triggering hydrogen evolution reaction. The catalytic activity is measured operando at the single supercrystal level by high resolution optical microscopy which allows to probe gas nanobubbles nucleation at the early stage with high temporal resolution and to quantify the amount of gas molecules trapped inside them. Finally, a correlative microscopy approach and high resolution electron energy loss spectroscopy helped to decipher the mechanisms at the origin of the local degradation of the supercrystals during catalysis, namely nanoscale erosion and corrosion. This article is protected by copyright. All rights reserved.