Thermochemical water splitting using perovskite oxides

 Thermochemical water splitting is a unique way to produce hydrogen from water using water dissociation. Simply, it utilizes two-step thermal cycle. At a higher temperature at which metal oxide is thermodynamically preferred to be reduced, oxygen would be released from the oxide while making oxygen vacant site. At a reduced temperature at which oxidation is thermodynamically preferred, the oxide will be reoxidized with water where the oxide absorbs oxygen from water molecules while releasing hydrogen to the atmosphere.

 We successfully assessed such capabilities of doped perovskite and discussed a key material parameter that drives the thermochemical reaction based on thermodynamics and kinetics [1]. To further enhance the efficiency for water splitting, we focus on the characteristics of defect chemistry in the bulk and at the bulk/gas interface and their impact on such capability.

This project is supported by Japan Science and Technology Agency (JST), PRESTO (~2016) and the Japan Society for Promotion of Science (JSPS), Wakate B (2016-2018).

Reference

[1] C.K. Yang, Y. Yamazaki*, A. Aydin, and S.M. Haile*, Thermodynamic and kinetic assessments of strontium-doped lanthanum manganites for thermochemical water splitting, J. Mater. Chem. A, 2 (2014), 13612-13623.

Patents

[2] Y. Yamazaki,S.M. Haile and C.K. Yang, Catalysts for thermochemical fuel production and method of producing fuel using thermochemical fuel production, US20130252808 A1 (2013), USA.

[3] Y. Yamazaki,S.M. Haile and C.K. Yang, Catalysts for thermochemical fuel production and method of producing fuel using thermochemical fuel production, WO2013141385 A1 (2013), Japan.

 

Proton-conducting oxides for solid oxide fuel cells

Fuel cell is a device to efficiently produce electricity from fuels. It is composed of electrolyte which permeates only ions, cathodes and anodes. We focus on proton conduction in perovskite oxides as an electrolyte. It defines the operation temperature of fuel cells.

Proton transport mechanism in the oxide is fundamental information to understand and control the proton conduction. However, the mechanism has been under debate since the discovery of proton-conduction oxide in 1981. We have demonstrated that the transport is governed by proton trapping. This fundamental understanding provided how to further enhance proton conductivity in the oxide [1]. We are creating the materials science and materials chemistry of proton-conducting oxide.

This project is supported by the Japan Science and Technology Agency (JST), PRESTO (~2016) and the Japan Society for Promotion of Science (JSPS), Grant-in-aid for Scientific Research A (2015-2018), and Shingagujutsu (2016~2018).

References

[1] Y. Yamazaki*, F. Blanc, Y. Okuyama, L. Buannic, J.C. Lucio-Vega, C.P. Grey, and S.M. Haile, Proton trapping in yttrium-doped barium zirconate, Nature Materials, 12 (2013), 647-651.

[2] F. Blank, L. Sperrin, D. Lee, R. Derisoglu, Y. Yamazaki, S.M. Haile, G. D. Paepe, C.P. Grey, Dynamic nuclear polarization NMR of low-γ nuclei: Insights into hydrated yttrium-doped BaZrO3, J. Phys. Chem. Lett. 5 (2014), 2431-2436.

[3] Y. Yamazaki, C.K. Yang and S.M. Haile, Unraveling the defect chemistry and proton uptake of yttrium-doped barium zirconate, Scripta Materialia, 65(2011), 102-107. Invited paper.

[4] Y. Yamazaki, R. Hernandez-Sanchez and S.M. Haile, Cation non-stoichiometry in yttrium-doped barium zirconate: phase behavior, microstructure and proton conductivities, J. Mater. Chem., 20(2010), 8158-8166.

[5] Y. Yamazaki, R. Hernandez-Sanchez and S.M. Haile, High total proton conductivity in large-grained yttrium-doped barium zirconate, Chem. Mater., 21(2009), 2755-2762.

[6] Y. Yamazaki, P. Babilo and S.M. Haile, Defect chemistry of yttrium-doped barium zirconate: A thermodynamic analysis of water uptake, Chem. Mater., 20(2008), 6352-6357.

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