AUTHOR=Edgecomb Joseph , Xie Xiaohong , Shao Yuyan , El-Khoury Patrick Z. , Johnson Grant E. , Prabhakaran Venkateshkumar 

TITLE=Mapping Localized Peroxyl Radical Generation on a PEM Fuel Cell Catalyst Using Integrated Scanning Electrochemical Cell Microspectroscopy

JOURNAL=Frontiers in Chemistry

VOLUME=8

YEAR=2020

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2020.572563

DOI=10.3389/fchem.2020.572563

ISSN=2296-2646

ABSTRACT=<p>Understanding molecular-level transformations resulting from electrochemical reactions is important in designing efficient and reliable energy technologies. In this work, a novel integrated scanning electrochemical cell microspectroscopy (iSECCMS) capability is developed by combining a high spatial resolution electrochemical scanning probe with <italic>in situ</italic> fluorescence spectroscopy. Using 6-carboxyfluorescein as a fluorescent probe, the iSECCMS platform is employed to measure the effect of the detrimental generation of reactive oxygen species (ROS) formed at the active sites of oxygen reduction reaction (ORR) catalysts. Carbon-supported tantalum-doped titanium oxide (TaTiO<sub>x</sub>) catalysts, a potential Pt-group-metal-free (PGM-free) cathode material explored for low temperature polymer electrolyte fuel cells (PEFCs), is used as a representative model ORR system, where generation of intermediate H<sub>2</sub>O<sub>2</sub> instead of fully oxidized H<sub>2</sub>O is a major concern. We establish that the iSECCMS platform provides a novel and versatile capability for spatially resolved mapping of <italic>in situ</italic> ROS generation and activity during the kinetically-limited ORR and may, therefore, aid the future characterization and development of high-performance PGM-free PEFC cathodes.</p>