Journal
PHYSICAL REVIEW B
Volume 80, Issue 24, Pages -Publisher
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.80.245119
Keywords
ab initio calculations; cerium compounds; density functional theory; enthalpy; entropy; heat of reaction; high-temperature effects; reaction kinetics theory; reduction (chemical)
Funding
- Sandia National Laboratories
- United States Department of Energy, National Nuclear Security Administration [DE-AC0494AL85000]
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We present an analysis of the equilibrium thermodynamics of two-step metal oxide-based water and carbon dioxide-splitting cycles. Within this theoretical framework, we propose a first-principles computational approach based on density-functional theory (DFT) for evaluating new materials for these cycles. Our treatment of redox-based gas-splitting chemistry is completely general so that the thermodynamic conclusions herein hold for all materials used for such a process and could easily be generalized to any gas as well. We determine the temperature and pressure regimes in which the thermal reduction (TR) and gas-splitting (GS) steps of these cycles are thermodynamically favorable in terms of the enthalpy and entropy of oxide reduction, which represents a useful materials design goal. We show that several driving forces, including low TR pressure and a large positive solid-state entropy of reduction of the oxide, have the potential to enable future, more promising two-step gas-splitting cycles. Finally, we demonstrate a practical computational methodology for efficiently screening new materials for gas-splitting applications and find that first-principles DFT calculations can provide very accurate predictions of high-temperature thermodynamic properties relevant to gas splitting.
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