Solvothermal Synthesis and Electrochemical Characterization of Shape-Controlled Pt Nanocrystals

Abstract

A simple, surfactant-free solvothermal method is reported for the preparation of <10 nm shape-controlled platinum crystallites. Reactions were carried out in N,N-dimethyformamide (DMF) and DMF–water mixtures. Effects of reaction time and temperature, DMF–water ratio, and metal precursor salt were examined. When the reaction conditions were tuned, ensembles of Pt particles with dominant truncated octahedral/cuboctahedral or cubic shapes could be formed from the metal acetylacetonate (acac) precursor salt. Metal nanocrystal development was monitored through the use of high-resolution transmission electron microscopy (HR-TEM) and X-ray and electrochemical analysis methods. Voltammograms probing CO and formic acid oxidation over shape-controlled nanocrystals adsorbed to a glassy carbon electrode displayed expected features characteristic of extended (111) and (100) facets, confirming the stability and surface cleanliness of particles taken directly from the reaction mixture. A mechanism for Pt reduction and the growth and stabilization of preferentially shaped Pt nanocrystals in the DMF–water solvent system is proposed. The involvement of DMF as a reducing agent and carboxylate ions as weakly coordinating, and hence easily displaced, nanoparticle capping ligands is discussed.