Abstract
AbstractCurrently, 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.
Highlights
Platinum is the best sole metal for the oxygen reduction reaction (ORR) in low temperature proton exchange membrane fuel cells (PEMFC)
Spectra taken after Ar+ sputtering away the very top layer in situ, after acid treatment, shows alloy composition and quality deeper into the surface, revealing factors that can affect the materials activity
At each incoming photon energy, the spectra are dominated by a doublet that corresponds to the binding energy of metallic platinum at 71 eV (4f7/2) [22,23,24]
Summary
Platinum is the best sole metal for the oxygen reduction reaction (ORR) in low temperature proton exchange membrane fuel cells (PEMFC). X-ray photoelectron spectroscopy (XPS), or more generally photoelectron spectroscopy (PES), is commonly used to probe the surface of catalyst materials to investigate its composition It can provide details of how impurities, oxides and adsorbates are present and bonded in the surface of a catalyst. SRPES was used to investigate three important components of the catalytically activity of Pt3Y: (i) impurities that could affect the performance, (ii) the composition of the platinum overlayer, and (iii) subsurface substochiometric oxide [14]. To observe these three components, SRPES spectra were taken before and after acid treatment. We expect that complete removal of Y–O will further increase the activity of Pt3Y
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