Quantifying the removal of stabilizing thiolates from gold nanoparticles on different carbon supports and the effect on their electrochemical properties

Abstract

Gold nanoparticles <10 nm in size are typically prepared using stabilizing agents, e.g. thiolates. Often standard recipes from literature are used to presumably remove these stabilisers to liberate the surface, e.g. for catalytic or electrocatalytic applications, however the success of these procedures is often not verified. In this work, thiolate-stabilised AuNPs of ca. 2 nm in size were synthesized and supported onto three different carbon supports, resulting in loadings from 15 to 25 wt% Au. These materials were post treated using three different methods in varying gas atmospheres to remove the stabilizing agent and to liberate the surface for electrochemical applications. Using thermogravimetry – mass spectroscopy (TG-MS), the amount of removed stabilizer was determined to be up to 95%. Identical location scanning transmission electron microscopy (il-(S)TEM) measurments revealed moderate particle growth but a stable support during the treatments, the latter was also confirmed by Raman spectroscopy. All treatments significantly improved the electrochemically accessible gold surface. In general, the results presented here point out the importance of quantitatively verifying the success of any catalyst post treatment with the aim of stabilizer removal.