Morphology mapping of platinum catalysts over the entire nanoscale

Abstract

Platinum nanoparticles are exceptional heterogeneous catalysts that play an important part in our existing and future energy economy. Understanding the size, shape and morphological transformations that may occur under different temperature conditions is vital to ensuring the long term stability of platinum-based technologies, or for planning ideal operating and storage conditions for platinum nanoparticles. In this paper we present a combination of experimental and theoretical results exploring the relationship between as-grown and thermodynamically preferred morphologies of platinum catalysts over the entire nanoscale. A shape-dependent thermodynamic model has been used to predict the stable morphology as a function of the size and temperature, and the first nanoscale phase diagram of platinum is constructed, by considering 15 different ideal and imperfect structures and shapes. This phase diagram is then discussed in relation to the experiments, to establish the relative stability of different shapes and the sizes at which they may be expected.