Electrosynthesis and characterization of PdIr using electrochemical atomic layer deposition for ethanol oxidation in alkaline electrolyte

Abstract

This work reports Pd and PdIr thin films electrodeposition via surface limited redox replacement reaction using electrochemical atomic layer deposition technique. Cyclic voltammetry (CV) showed Pd and PdIr voltammetric signatures confirming the successful utilization of Cu as sacrificial metal for Pd and Ir ions. The resulting deposits were further characterized using XRD, EDS, XPS, SEM and AFM, confirming their structural morphology and surface roughness. The catalytic activity of the thin films towards the oxidation of ethanol was determined using CV. PdIr showed a more negative onset potential and higher current (−0.423 V; 0.664 mA) than Pd (−0.402 V; 0.494 mA) thin film, indicating a more catalytic behavior. Further, PdIr showed a higher if/ib ratio of 1.094 than Pd (if/ib = 0.94) indicating higher tolerance to poisoning by ethanol intermediates than Pd. Moreover, chronoamperometry (CA) confirmed that the addition of Ir to Pd improves the stability of the PdIr film. The resultant behaviour was also confirmed by EI spectroscopy with smaller Rct = 0.23 (kΩ) for PdIr than that of Pd; Rct = 14.8 (kΩ) when.Subjected at a fixed potential of −0.2 V. The higher catalytic activity of PdIr towards EOR makes it a promising candidate as electrocatalyst for alkaline direct ethanol fuel cell (DEFCs) than Pd.