Effect of Pretreatment on Durability of fct-Structured Pt-Based Alloy Catalyst for the Oxygen Reduction Reaction under Operating Conditions in Polymer Electrolyte Membrane Fuel Cells

The effects of different pretreatments on performance and durability of the fct-structured Pt-based alloy catalyst were investigated under operating conditions in PEMFCs. The fct-structured PtCo catalyst (PtCo/CN) was prepared by impregnating transition metal salts into Pt/CN catalyst followed by a heat-treatment under a reducing atmosphere. To remove the excess amount of transition metal on the catalyst surface, a preleaching procedure was carried in 0.5 M H₂SO₄ solution to synthesize the L-PtCo/CN catalyst. Subsequently, the L-PtCo/CN catalyst was annealed under a reducing atmosphere at a mild temperature to synthesize the AL-PtCo/CN catalyst. The intensive physicochemical analyses were performed before and after the durability test to evaluate the effects of the pretreatments on the catalyst durability. All catalysts were electrochemically tested for the ORR performance, while the durability test was carried out in a single cell by sweeping 30 000 potential cycles. The results indicated that the L-PtCo/CN catalyst contains a low percentage of metallic Pt(0), degrades faster, and exhibits unstable performance when compared to the AL-PtCo/CN catalyst. The L-PtCo/CN catalyst after the durability test shows poor catalyst particle distribution and catalyst particle detachment. On the other hand, the AL-PtCo/CN catalyst shows a remarkably stable performance of ECSA of 9% and only 16% in maximum power density loss after AST.