promising properties for redox applications, including gravimetric oxygen storage up to 4% by mass, high stability and rapid reversibility, with re-oxidation in less than 1 min at 400 C. Finally, the redox chemistry of Ca 0.8 Sr 0.2 MnO 3 was also investigated using in situ X-ray photoelectron spectroscopy and near-edge X-ray absorption measurements at near ambient pressure in oxygen atmospheres.
A materials screening of perovskites for oxygen storage applications yielding two promising materials, SrFe0.95Cu0.05O3−δ and Ca0.8Sr0.2MnO3−δ with outstanding performance.
The
oxidation and reduction of mixed cerium zirconium oxides, Ce1–x
Zr
x
O2, with x varied in the range 0–0.3 in steps of 0.05, in
a low-pressure oxygen atmosphere were experimentally investigated.
The experiments utilized a novel method developed by the authors,
in which the samples are reduced and oxidized in a sealed vacuum chamber
by irradiating them with a xenon arc lamp. The changes in pressure
due to the release or consumption of oxygen are used to quantify the
extent and rates of the reactions. The system can achieve heating
rates in excess of 100 °C s–1, which is hundreds
of times faster than is possible with a thermobalance. In addition,
the gas phase transport is very rapid as it is driven by pressure
gradients. The combined high heating rate and fast gas phase transport
offers unique conditions in which to measure the actual kinetics of
the reactions. The oxidation kinetics showed a strong dependence on
the amount of Zr4+ in the samples, where the rate of oxidation
decreased with increasing Zr4+ concentration. The effect
of adding 2.5% Sm3+ or La3+ to the Ce0.85Zr0.15O2 was also investigated with the hope
of improving the kinetics. The addition of La3+ to Ce0.85Zr0.15O2 was seen to offer an increase
in the reaction rates, although the oxidation kinetics were still
slower than that of pure CeO2. Finally, the reduction kinetic
data are presented, but even with the optimal conditions the reduction
reaction still appeared to be limited by the heating rate; thus, it
was concluded that the reduction kinetics were too rapid to quantify
by this method.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.