jp502970r_si_001.pdf (1.15 MB)
Water Reactivity on the LaCoO3 (001) Surface: An Ambient Pressure X‑ray Photoelectron Spectroscopy Study
journal contribution
posted on 2014-08-28, 00:00 authored by Kelsey A. Stoerzinger, Wesley T. Hong, Ethan J. Crumlin, Hendrik Bluhm, Michael
D. Biegalski, Yang Shao-HornThe
reactivity of water with the (001)pc surface of epitaxial
LaCoO3 (LCO) thin films was investigated as a function
of relative humidity (RH) by ambient pressure X-ray photoelectron
spectroscopy. Specifically, water isobars (pH2O = 100 mTorr)
were performed cooling from 300 to 25 °C, reaching a final RH
of ∼0.3%. Significant changes were found in the O 1s and C
1s core-level spectra at different RHs, which were deconvoluted to
yield new insights into the hydroxylation and hydration of the LCO
surface. Surface hydroxyl groups were found dominant, which were accompanied
by minor components including (bi)carbonates, adsorbed water, and
undercoordinated/surface-dipole-influenced oxygen sites on the perovskite
surface. A multilayer model was used to quantify the coverage of each
species, from which the LCO (001)pc surface was found to
exhibit three different regimes upon increasing RH. The water reactivity
with the LCO surface proceeded by surface hydroxylatation to reach
saturation (up to ∼0.5 ML), after which carbonates were found
to displace hydroxyl groups, and then adsorption of water molecules.