イベント

千現地区 研究本館8階 中セミナー室
Sengen Main Bldg. 8F Middle Seminar Room

Hirohito Ogasawara, PhD (Staff Scientist, SLAC National Accelerator Laboratory)

Operando XPS Observation of Electrode Surfaces During Electrochemical Reactions

I will show recent operando electron and x-ray spectroscopy studies, which address fundamental questions regarding the reaction mechanism and active sites of the Oxygen Reduction Reaction (ORR) and Oxygen Evolution Reaction (OER). We have identified the surface electronic structure and chemical nature of catalytic electrodes during electrochemical reactions through the use of membrane electrolyte bases electrochemical spectroscopy cell and ambient pressure photoemission spectroscopy (APXPS) and an electrochemical cell [1]. The sluggish kinetics in ORR is one of the key challenges in polymer electrolyte membrane fuel cells. We identified adsorbed OH as the ORR intermediate that controls the kinetics and found the form of adsorbed depends on the local humidity [2]. One of the crucial factors that limit electrochemical water splitting is the large overpotential required for the OER, in which Iridium oxide is known to have high activity and stability. APXPS studies indicate, the oxidation state of iridium at the surface changes when OER takes place [3]. These studies were conducted using the SPEAR-3 synchrotron, a low-emittance 3 GeV synchrotron light source at Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory.

[1] S. Kaya et al., Catalysis Today 205 (2013) 101.
[2] H. Sanchez Casalongue et al., Angewandte Chemie 126 (2014) 7297.
[3] H. Sanchez Casalongue et al., Nature Communications 4 (2013) 2817.