High durability of Pt-Ni-Ir/C ternary catalyst of PEMFC by stepwise reduction synthesis

Abstract

How to improve durability of catalysts is the major challenge hindering the large-scale implementation of proton exchange membrane fuel cells (PEMFCs). The alloy catalysts have been developed in efforts to reduce platinum loading, enhance catalysts activity and durability for oxygen reduction reaction (ORR) of PEMFCs. This manuscript reports the application of stepwise reduction synthesis to synthesize Pt–Ni/C and Pt–Ni–Ir/C catalysts. The synthesized electrocatalysts were characterized by X–ray diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma mass spectrometry (ICP), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The results from CV and LSV showed that when as-prepared Pt–Ni–Ir nanocrystals are uniformly dispersed on the carbon support, the catalyst exhibits excellent electrocatalytic activity and stability. When the atomic ratio of Pt, Ni, Ir is 2:2:1, after durability test of 5000 cycles, rotating disk electrode (RDE) demonstrated ORR activities of the as-prepared catalysts with the highest mass activity (MA) of 351mA⋅gPt−1 at 0.9ViR-free and electrochemically active surface area (ECSA) of 80 m2⋅gPt−1, which is over 17 and 2 times than those of Pt/C JM (Johnson Matthey) catalyst, respectively. This work highlights the potential to use a preparative method which means step-by-step reduction synthesis to form ternary alloy catalysts for ORR of PEMFCs.