Thermal Treatment Effects on Pd5Cu4Pt Electrocatalyst for the Oxygen Reduction Reaction in a PEM Fuel Cell

The research is aimed to study the thermal treatment effects in the electrochemical activity of Pd5Cu4Pt electrocatalyst for the oxygen reduction reaction (ORR) in acid medium as well as on its performance as cathode electrode in a single Proton Exchange Membrane Fuel Cell (PEMFC). The electrocatalyst is synthesized by chemical reduction of PdCl2, CuCl2 and H2PtCl6 with NaBH4 in THF, and is characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Cyclic voltammetry (CV) and rotating disc electrode (RDE) are performed for electrochemical characterization in a 0.5 M H2SO4 at 25 ºC. Results of thermal treatment at 200 and 300 ºC in H2 atmosphere show a growth of nanocrystallyte particles and an enhancement of the crystallinity of the electrocatalyst. Shifts towards positive 2 θ XRD values are associated to the incorporation of elements inside the crystalline structure of the sample. Electrochemical results show a decrease in the electrocatalytic activity as the temperature of the thermal treatment increases. The maximum power density, Wmax of 350 mW cm-2 is achieved using Pd5Cu4Pt without thermal treatment with 0.8 mg cm-2 cathode electrocatalyst loading of the PEMFC. This result is attributed to the formation of new inactive-ORR phases on the electrocatalyst with the thermal treatment.