Surface Composition of a Highly Active Pt₃Y Alloy Catalyst for Application in Low Temperature Fuel Cells

Abstract

Currently, platinum is the most widely used catalyst for low temperature proton exchange membrane fuel cells (PEMFC). However, the kinetics at the cathode are slow, and the price of platinum is high. To improve oxygen reduction reaction (ORR) kinetics at the cathode, platinum can be alloyed with rare earth elements, such as yttrium. We report that Pt3Y has the potential to be over 2 times more active for the ORR compared with Pt inside a real fuel cell. We present detailed photoemission analysis into the nature of the sputtered catalyst surface, using synchrotron radiation photoelectron spectroscopy (SRPES) to examine if surface adsorbates or impurities are present and can be removed. Pretreatment removes most of the yttrium oxide in the surface leaving behind a Pt overlayer which is only a few monolayers thick. Evidence of a substochiometric oxide peak in the Y 3d core level is presented, this oxide extends into the surface even after Ar+ sputter cleaning in‐situ. This information will aid the development of new highly active nanocatalysts for employment in real fuel cell electrodes.

Unraveling the Surface Chemistry and Structure in Highly Active Sputtered Pt3Y Catalyst Films for the Oxygen Reduction Reaction

“…Sputtering was performed in the same way on glassy carbon and silicon wafer substrates, the latter of which were used for XPS, XRD, and AFM measurements. XPS performed on GC-supported films confirmed their composition to be equal to Si-supported films; the choice of substrate does not affect the conclusions …”

“…XPS performed on GC-supported films confirmed their composition to be equal to Si-supported films; the choice of substrate does not affect the conclusions. 15 Acid treatment was performed by immersing the alloy film into 0.1 M HClO 4 three times for 10 min per time with subsequent rinsing in ultrapure Millipore water.…”