Controllable Surfactant‐free Synthesis of Colloidal Platinum Nanocuboids Enabled by Bromide Ions and Carbon Monoxide

Abstract Pt nanoparticles enclosed by Pt{100} facets show unique properties in electrocatalysis. However, a convenient, cost‐effective, controllable and scalable synthesis of surface clean Pt colloidal nanocuboids remains a big challenge. In this work, small platinum nanocubes with controllable size ranging from 3.4 to 7.1 nm and nanocuboids with tuneable length‐to‐width aspect ratios were synthesized under the 10 %CO/90 %He atmosphere, by controlling the proportion of KBr and Pt precursors and the concentration of the platinum precursor in ethylene glycol. The exposed Pt{100} terrace sites of the synthesize materials were not only identified by the transmission electron microscopic images but also by the electrochemical adsorption/desorption of hydrogen during cyclic voltammograms. In addition, the exposed Pt{100} domains were quantitatively measured by the electrochemical adsorption/desorption of germanium, proving the formation of nanocuboids. Finally, the synthesized Pt nanocubes were applied to the oxygen reduction reaction and the electrochemical oxidation of methanol, showing a big potential in electrocatalysis.