Abstract
Sn-Pd electrocatalysts with a constant atomic ratio of 60 at.% Sn-40 at.% Pd suitable for potential application in direct ethanol fuel cells were synthesized using a novel two-step electrodeposition method. First, Sn was electrodeposited in various forms of dendrites, from spear-like and needle-like to individual fern-like dendrites to a network of intertwined fern-like dendrites, by varying the cathodic potential and then performing electrodeposition of Pd at a constant current density in the second step. A morphological and elemental analysis of Sn and Sn-Pd electrocatalysts was performed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) techniques, while the size of Sn dendrites was analyzed using the particle size distribution (PSD) method. Cyclic voltammetry (CV) and chronoamperometry were applied in order to study the catalytic behavior of Sn-Pd electrocatalysts in the ethanol oxidation reaction (EOR), while CO stripping was used to estimate the antipoisoning capability of the electrocatalysts. The Sn surface morphology of the sub-layer was highly correlated with the electrocatalytic activity of the examined Sn-Pd electrocatalysts. The high activity it presented towards the EOR showed the suitability of the Sn-Pd electrocatalyst constructed from individual fern-like Sn dendrites as a sub-layer. Compared to Pd alone, this Sn-Pd catalyst showed more than 3 times higher activity and improved EOR kinetics. This enhancement in the catalytic activity of the Sn-Pd electrocatalysts is attributed to both the morphological characteristics of Sn as a sub-layer and the bifunctional effect.