The size-dependent anode-catalytic activity of nickel-supported palladium nanoparticles for ethanol alkaline fuel cells

Spherical nanoparticles of palladium with varying particle diameters have been prepared from PdCl2 by wet chemical single pot synthesis using citric acid as reducing agent in the presence of PVA. The size of the nanoparticles has been tuned by changing the duration of reflux. The resulting nanoparticles have been dip-coated on Ni-foil, and evaluated as anode catalysts for oxidation of ethanol under alkaline conditions. The morphology and surface characteristics of the Pd nano-catalyst have been investigated by TEM and FE-SEM in conjugation with EDS. Measurements of catalytic activity by electrochemical methods (cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy) reveal that the majority of the nanoparticle-embedded anodes, despite less Pd-0 loading, act as superior electrocatalysts as compared to the nickel-supported Pd electrode constructed electrochemically. In this study, the effects of the different extent of catalyst-loading on the experimental parameters have been rationalized to obtain the size-dependence of the electrocatalytic activity. The experimental results clearly show that there is noticeable development in the intrinsic catalytic activity and poisoning resistance of the anode catalysts. In addition, the intrinsic electrocatalytic activity of the nano-palladium is found to be size-dependent, which increases with decrease in particle size particularly below the diameter of 19 nm.