A Novel Two-Step Electrochemical Deposition Method for Sn-Pd Electrocatalyst Synthesis for a Potential Application in Direct Ethanol Fuel Cells

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.

Influence of electrodeposition regime and Sn:Pd ratios in Sn-Pd electrocatalysts on ethanol oxidation reaction

“…22 Unlike Ni, it was shown that Sn as a sub-layer to Pd increases the activity towards EOR. [23][24][25][26] Nevertheless, electrodeposition provides the opportunity to develop innovative structure as was shown in our previous investigations. 27,28 Various structures, such as dendrites, needles, and other disperse (irregular) forms, are very desirable for electrocatalytic reactions due to their reasonably large surface area.…”

“…In our previous work, it was shown that the surface morphology of Sn, as the sub-layer in Sn-Pd electrocatalysts, strongly affects the electrocatalytic activity of Sn-Pd electrocatalysts with a constant atomic ratio of 60 at.% Sn-40 at.% Pd in EOR. 23 The role of Sn was to contribute Pd to oxidize chemisorbed species formed during the electrooxidation of ethanol by providing adsorbed OHspecies 14,15 , thereby enhancing the catalytic performance of the bimetallic catalysts. X-ray photoelectron spectroscopy (XPS) measurements showed that the presence of Sn affects the electronic state of Pd by reducing the adsorption strength of the reaction intermediates on Pd, which has a positive effect on Sn-Pd electrocatalytic activity during the EOR.…”

Tin as a co-catalyst for electrocatalytic oxidation and reduction reactions

“…When the alloy structure is formed, Sn modifies and enhances the electronic structure of Pd by donating an electron to Pd sites and subsequently weakening the adsorption of carbonaceous species. 32 Some SnO x residuals can be retained even under highly cathodic potentials and may actively participate in the CO 2 RR. It is believed that the presence of residual surface oxide facilitates the formation of the *CO 2 ˙ − intermediate as the rate determining step, whereas in its absence, the HER becomes the dominant cathodic pathway.…”

The Effect of Ga Incorporation in TiO2/SnO2 Nanoparticle‐Decorated Hierarchical ZSM‐5 Composite as Precious‐Metal‐Free Electrocatalysts for Oxygen Electro‐Reduction

“…Carbon nanotubes doped with Co and N showed high catalytic efficiency attributed to the high specific surface area and the synergistic effect of Co and N co‐doping [8] . Many transition metals such as Co, Ti, Sn, Fe, Ga, Ni have been used for catalysis in alkaline medium [9–12] . TiO 2 @TiOF 2 heterojunction showed high electrical conductivity and stable cyclic stability of up to 10 000 cycles at high current density in sodium‐ion batteries [13] …”