PNNL

Abstract

Understanding molecular-level transformations resulting from electrochemical reactions is important for 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 in situ 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 (TaTiOx) 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 H2O2 instead of fully oxidized H2O is a major concern. We establish that the iSECCMS platform provides a novel and versatile capability for spatially-resolved mapping of in situ ROS generation and activity and may, therefore, aid the future characterization and development of high-performance PGM-free PEFC cathodes. This work was primarily supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences and Biosciences Division (VP, PZE, GEJ). JE acknowledges the DOE Science Undergraduate Laboratory Internship (SULI) program and XX, YS, and VP were supported by the DOE Fuel Cell Technologies Office. The research was performed using EMSL, a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated by Battelle for DOE under Contract DE-AC05-76RL01830.