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

Electrocatalytic Activity and Stability of Titania-Supported Platinum–Palladium Electrocatalysts for Polymer Electrolyte Membrane Fuel Cell

Titania-supported platinum–palladium electrocatalysts (PtPd/TiO₂) were synthesized and investigated as alternative catalysts for the oxygen reduction reaction (ORR). Transmission electron microscope images revealed a uniform distribution of metal nanoparticles (<i>d</i>_M = 3–5 nm) on the TiO₂ support. An increase in ORR activity has been observed with an increase in the Pd content of the bimetallic alloy up to 30%, and beyond this composition, the decrease in catalytic activity has been found to be due to the blocking of Pt active sites by a large amount of Pd in the catalyst. The PtPd/TiO₂ electrocatalyst with a Pt/Pd composition of 70:30 shows activity comparable to that of a commercial Pt/C catalyst (TKK) in rotating ring-disk electrode studies. The accelerated durability test results show good stability for the PtPd/TiO₂ electrocatalysts at high potentials in terms of minimum loss in the Pt electrochemical surface area. The high stability of the PtPd/TiO₂ electrocatalyst synthesized in this investigation offers a new approach to improve the reliability and durability of polymer electrolyte membrane-based fuel cell cathode catalysts