Electrodeposition and dissolution of Zn on PdAg foil in a chlorozincate ionic liquid to fabricate micro-nanostructured PdAgZn alloy films for electrocatalysis

The fabrication of micro-nanostructured (porous) PdAgZn films is attempted by electrodeposition of Zn on PdAg substrate to form PdAgZn surface alloy followed by partial electrochemical dissolution of Zn from the PdAgZn alloy. The preparation was performed in a ZnCl₂-1-ethyl-3-methylimidazolium chloride ionic liquid thanks to the high thermal stability of this melt. High working temperature (170°C) and an alloying time are required for the formation of the surface alloy owing to the low atom diffusivity of Pd. Not all the Zn in the surface alloy can be anodically dissolved because of the parting limit associated with dealloying process. Therefore, the morphology and composition of the resulted PdAgZn varied with the alloying/dealloying condition. Electro-oxidation of ethanol was used as an example to test the activity of the prepared porous PdAgZn electrodes. The results showed that the catalytic activity of the PdAgZn depends on not only the surface area but also the composition of the produced PdAgZn. The PdAgZn that was prepared by repeating for three times the deposition of 3.33 C cm⁻² Zn at −0.2 V and immersion for 30 min at 170°C at open circuit potential, then dealloyed at 1.0 V showed the best performance for electro-oxidation of ethanol with the oxidation current about 25 times higher than at the unmodified PdAg electrode.