Surfactant Removal for Colloidal Nanoparticles from Solution Synthesis: The Effect on Catalytic Performance

Colloidal nanoparticles prepared by solution synthesis with robust control over particle size, shape, composition, and structure have shown great potential for catalytic applications. However, such colloidal nanoparticles are usually capped with organic ligands (as surfactants) and cannot be directly used as catalyst. We have studied the effect of surfactant removal on the electrocatalytic performance of Pt nanoparticles made by organic solution synthesis. Various methods were applied to remove the oleylamine surfactant, which included thermal annealing, acetic acid washing, and UV-Ozone irradiation, and the treated nanoparticles were applied as electrocatalysts for the oxygen reduction reaction. It was found that the electrocatalytic performance, including electrochemically active surface area and catalytic activity, was strongly dependent on the pretreatment. Among the methods studied here, low-temperature thermal annealing (∼185 °C) in air was found to be the most effective for surface cleaning without inducing particle size and morphology changes.