| AVS 57th International Symposium & Exhibition | |
| In Situ Microscopy and Spectroscopy Topical Conference | Tuesday Sessions |
| Session IS+SS-TuM |
| Session: | In Situ Spectroscopy – Interfacial Chemistry/Catalysis |
| Presenter: | A.H. McDaniel, Sandia National Laboratories |
| Authors: | A.H. McDaniel, Sandia National Laboratories F. El Gabaly, Sandia National Laboratories M. Grass, Lawrence Berkeley National Laboratory Z. Liu, Lawrence Berkeley National Laboratory K.F. McCarty, Sandia National Laboratories H. Bluhm, Lawrence Berkeley National Laboratory |
| Correspondent: | Click to Email |
Electrochemical technologies will be increasingly used to supply energy to the world without contributing to climate change. These technologies can store and convert energy with unsurpassed efficiencies through, for example, the charging and discharging of batteries or the inter-conversion of electrical and chemical energy via fuel cell and electrolyzer. Perhaps the most important phenomena to understand in electrochemical energy storage/conversion is how electric charge is transferred across interfaces and subsequently stored in material phases and/or double layers. Currently, detailed knowledge is lacking of critical pathways such as which chemical reactions are responsible for charge transfer, what species are involved, and where charge transfer reactions occur in heterogeneous devices. These limitations arise in no small degree from the physical complexities of these devices, which consist of a variety of electrified materials undergoing chemical reactions. Lacking this knowledge, development proceeds largely using engineering approaches.
To help answer these questions we have spectroscopically characterized electrochemical charge-transfer and storage as it occurs. This is accomplished by primarily using a new diagnostic based on synchrotron X-ray spectroscopies that we have been developing at the Advanced Light Source (ALS, LBNL, Berkeley, CA ). Photoelectrons are used as a contact-less probe for the direct measurement of the electric inner potential everywhere in a Ni-YSZ based electrochemical cell operating at near ambient pressure. This information, in addition to space-resolved chemical characterization of the surface species showing phase changes relevant to Ni-metal-hydride batteries, will be discussed. The experimental configuration consists of a thin-film Ni electrode that is electrochemically modified by injection of O2- ions. During an applied bias, charge is stored in the electrode by the conversion of the Ni to NiOOH. This leads to dramatic changes in the XPS spectra as well as the existence of a constant discharge potential plateau resulting from the equilibrium of NiOOH with two other phases, Ni and H2O. Thus, our approach has the ability to identify the phases that store charge, which are only stable under electrical bias. This rich data will provide new understanding on how electrochemically driven phases form.