jz401271m_si_001.pdf (1.35 MB)
Tuning the Spin State in LaCoO3 Thin Films for Enhanced High-Temperature Oxygen Electrocatalysis
journal contribution
posted on 2015-12-16, 23:14 authored by Wesley T. Hong, Milind Gadre, Yueh-Lin Lee, Michael
D. Biegalski, Hans M. Christen, Dane Morgan, Yang Shao-HornThe
slow kinetics of oxygen surface exchange hinders the efficiency of
high-temperature oxygen electrocatalytic devices such as solid oxide
fuel cells and oxygen separation membranes. Systematic investigations
of material properties that link to catalytic activity can aid in
the rational design of highly active cathode materials. Here, we explore
LaCoO3 thin films as a model system for tuning catalytic
activity through strain-induced changes in the Co spin state. We demonstrate
that Raman spectroscopy can be used to probe the Co–O bond
strength at different temperatures to determine the relative spin
occupancies of LaCoO3. We find that strain can be used
to reduce the spin transition temperature and promote the occupation
of higher spin states that weaken the Co–O bond. The decrease
in Co–O bond strength and increased spin moment of the thin
films result in significant enhancements of the oxygen surface exchange
kinetics by up to 2 orders of magnitude.