Spectroscopy at Electrified Interfaces: from Electrocatalysts to Battery Materials

Heng-Liang Wu

Center for Condensed Matter Sciences, National Taiwan University, Taiwan

 


Abstract:

The solid-liquid interfacial reactions play a crucial role in controlling the performance and stability of electrocatalysts1-2 and battery materials4-6. In situ vibrational spectroscopy techniques such as Raman and surface-enhanced infrared absorption spectroscopy are the powerful tools for examining reaction intermediates on the solid-liquid interfaces. By combining in situ vibration spectroscopy with X-ray spectroscopy, the effect of the local electronic structure of the materials on the reaction mechanism and electrochemical kinetics of energy conversion and storage reactions can be elucidated. In this talk, we report on our use of in situ spectroscopy to investigate the redox mechanism of energy materials in Li-ion batteries, Zn-ion batteries and electrochemical CO2 reduction reactions. For instance, various CO intermediates such as COatop and CObridge, are formed on different Cu electrocatalysts during electrochemical CO2 reduction. The formation of COatop/CObridge, can be correlated to the selectivity of CO2-to-C2H4 conversion. The Cu catalysts modulated by the electrochemical method exhibit different oxidation states and reaction intermediates as well as electrocatalytic properties. We also studied the reaction mechanism and electrochemical kinetics of Li-rich cathodes and V2O5 cathode in the Li-ion and Zn-ion batteries, respectively. The local electronic structure of Li-rich cathodes varies with the excess Li (i.e., Li2MnO3 phase) and Ni contents. Compared to the Li-rich cathodes with higher amounts of Li2MnO3 phase (high excess Li content (HLC) cathode), those with lower Li2MnO3 contents (low excess Li content (LLC) cathode) exhibit reversible anion redox reactions and suppressed voltage hysteresis. The obtained insights into the effect of local coordination on the reaction mechanism and kinetics provide a better understanding and control of cathode materials.


 


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