Insights from Near-Surface Atomic Structures and Composition for Catalytic Activity and Stability of Oxides in Electrochemical Reactions

Abstract

Electrocatalysts play an important role in catalyzing the kinetics for many reactions (e.g., oxygen reduction reaction, oxygen evolution reaction and CO2photoelectrochemical reduction) for many energy storage and conversion devices, such as metal-air batteries, electrolyzer and fuel cells. Although oxides are promising catalysts due to their natural abundance, low cost, and widely tunable properties, the design of oxide electrocatalytic functionality is not straightforward due to the lack of information on the oxide surface atomic structure and chemistry. Using a combination of in situ surface-sensitive X-ray diffraction and spectroscopy methods, we have studied several electrochemical devices (e.g., (La0.5Sr0.5)2CoO4+δ/La1-x Sr x CoO3-δ/GDC/YSZ heterostrucured cathodes for solid oxide fuel cells, spinel oxides for supercapacitors, LiMn2O4 for batteries) and model systems (e.g., La1-x Sr x CoO3-δ/SrTiO3 for fuel cells and MgMn2O4 thin film for battery cathodes) to obtain their near-surface atomic structures and composition changes during various electrochemical reactions. The information we learned provides critical insights about the dynamic changes of oxides during the electrochemical reactions and their influences on alternating reaction paths for optimizing ORR/OER and CO2 reductions. Based on these findings, we have figured out strategies to control the oxide surfaces for the enhanced activity and better stability for fuel production, energy storage, and CO2 reduction.