Ionic liquid-mediated synthesis of ‘clean’ palladium nanoparticles for formic acid electrooxidation

Uniform Pd nanoparticles supported on Vulcan XC-72 carbon were successfully synthesised at room temperature using an ionic liquid (IL) as a mediator for the nucleation and growth process. The UV–vis spectra indicated that the IL interacted with the Pd precursor to form a complex that plays an important role in the nucleation and growth process of Pd nanoparticles. The IL-mediated synthesis of the Pd/C catalyst (Pd/C-IL) was extensively characterised by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, electrochemical COad stripping, linear scanning voltammetry and chronoamperometry. Physical characterisations revealed that the Pd/C-IL had an average size of 2.8 nm and a narrow size distribution. In addition, a very ‘clean’ surface was obtained for the Pd nanoparticles due to a weak interaction between the IL and the Pd nanoparticle surface resulting in the facile removal of the IL in the post-treatment process. More importantly, electrochemical studies demonstrated that, at an operating potential of 0.2 V, the catalytic activity of the Pd/C-IL was approximately 1.6 and 4.2-fold greater than the commercial Pd/C catalyst and the common Pd/C catalyst, respectively.