Operational Limits of Redox Metal Oxides Performing Thermochemical Water Splitting
Abstract
Solar thermochemical hydrogen production is an attractive technology that stores intermittent solar energy in the form of chemical bonds. Efficient operation requires the identification of a redox‐active metal oxide (MOx) material that can achieve high conversion of water to hydrogen at minimal energy input. Water splitting occurs by consecutive reduction and reoxidation reactions of MOx. MOx is reduced to MOx−δ and, in the second step, is reoxidized by water recovering the initial MOx and generate H2. The material must reduce at temperatures achievable in concentrated solar receiver/reactors, while maintaining a thermodynamic driving force to split water. At equilibrium, extent of reduction depends on temperature and oxygen partial pressure, and in this analysis, a set of thermodynamic properties, namely, enthalpy and entropy of oxygen vacancy formation, is sufficient to represent MOx. Herein, a method to easily classify materials based on these thermodynamic properties under any condition of oxygen partial pressure and temperature is presented. This method is based on fundamental thermodynamic principles and is applicable for any redox material with known thermodynamic properties. Despite the simplicity of the method, it is believed that this analysis will support future research in targeting thermodynamic properties of redox‐active metal oxides.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jun 24, 2021
- Source ID
- 10.1002/ente.202100222
Entities
People
- Alberto de la Calle
- Alicia Bayon
- Christopher L. Muhich
- Ellen B. Stechel
Organizations
- ARPA-E
- Arizona State University
- Defense Advanced Research Projects Agency
- Office of Energy Efficiency and Renewable Energy