Support Effect in the Electrocatalytic Activity of Cu@Pd Core-Shell toward Electrooxidation of Short Chain Alcohols in Alkaline Media

Cu@Pd core-shell particles were synthesized by a chemical method using ethylene glycol as reaction media. Carbon nanofibers (CNFs) and Vulcan carbon were employed as supports and added during the catalyst synthesis procedure. According to transmission electron microscopy, Cu@Pd core-shell particles were prepared with two different morphologies regardless of support: semi-spherical and rod-shaped nanoparticles with sizes of 6 and 10 nm, respectively. X-ray diffraction patterns were typical of a face-centered cubic structure with crystallite sizes of 8.2 and 8.8 nm for Cu@Pd/C and Cu@Pd/CNF, respectively. X-ray fluorescence analyses revealed a composition (% mass) of 60/40 for the Cu@Pd materials. Electrocatalytic activity was evaluated by cyclic voltammetry (CV) at alcohol concentrations of 0.1, 0.5, 1 and 3 M for methanol, ethanol, ethylene glycol and glycerol. The highest current densities (at least 3-fold) and the most negative potentials (at least 0.2 V of difference) were found through the use of nanofibers instead of Vulcan carbon. Evaluation of the electrocatalyst/support stability was performed by cyclic voltammetry (1000 cycles), showing superior stabilities for the CNF materials compared to the Vulcan supported systems, with metal losses of approximately 30%. The enhancement of the electrocatalytic activity and stability is related to the Cu@Pd metal-metal and Cu@Pd/CNFs metal/support interaction.