Ambient Pressure XPS Observation of Electrode Surfaces During Electrochemical Reactions

The sluggish kinetics in oxygen reduction reaction (ORR) is one of key challenges in polymer electrolyte membrane fuel cells (PEMFCs). Understanding the ORR mechanism under operating conditions is essential to isolate parameters that allow for high PEMFC efficiencies. Through the use of ambient pressure photoemission spectroscopy (APXPS) at Stanford Synchrotron Radiation Lightsource (SSRL) [1], we identified the surface speciation of the fuel cell Pt cathode under different operating conditions. We also established that the species on the electrode change drastically depending on the oxygen pressures. We used this knowledge to clarify that the favored ORR pathway is dependent on the operating conditions, thus identifying a key parameter to be controlled in high efficiency fuel cells [2].

1. S. Kaya, H. Ogasawara, L.-A. Nasdslund, J.-O. Forsell, H. Sanchez Casalongue, D.J. Miller, A. Nilsson, Ambient-pressure photoelectron spectroscopy for heterogeneous catalysis and electrochemistry, Catalysis Today 205 (2013) 101.

2. H.S. Casalongue, S. Kaya, V. Viswanathan, D. Miller, D. Friebel, J.K. Noskov, A. Nilsson, H. Ogasawara, Direct observation of the oxygenated species during oxygen reduction reaction on a Pt fuel cell cathode, submitted.