Impact of enhanced oxide reducibility on rates of solar-driven thermochemical fuel production
- PDF / 486,372 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 59 Downloads / 156 Views
Research Letter
Impact of enhanced oxide reducibility on rates of solar-driven thermochemical fuel production Michael J. Ignatowich, Department of Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA Alexander H. Bork, ETH Zürich, Zürich 8093, Switzerland Timothy C. Davenport, Department of Materials Science, Northwestern University, Evanston, IL 60208, USA Jennifer L. M. Rupp, Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA Chih-kai Yang, Materials Science, California Institute of Technology, Pasadena, CA 91125, USA Yoshihiro Yamazaki, INAMORI Frontier Research Center, Kyushu University, Fukuoka 819-0395, Japan Sossina M. Haile, Department of Materials Science, Northwestern University, Evanston, IL 60208, USA; Materials Science, California Institute of Technology, Pasadena, CA 91125, USA Address all correspondence to S. M. Haile at [email protected] (Received 12 August 2017; accepted 25 September 2017)
Abstract Two-step, solar-driven thermochemical fuel production offers the potential of efficient conversion of solar energy into dispatchable chemical fuel. Success relies on the availability of materials that readily undergo redox reactions in response to changes in environmental conditions. Those with a low enthalpy of reduction can typically be reduced at moderate temperatures, important for practical operation. However, easy reducibility has often been accompanied by surprisingly poor fuel production kinetics. Using the La1−xSrxMnO3 series of perovskites as an example, we show that poor fuel production rates are a direct consequence of the diminished enthalpy. Thus, material development efforts will need to balance the countering thermodynamic influences of reduction enthalpy on fuel production capacity and fuel production rate.
Fuel production by two-step solar-driven thermochemical cycling (STC) has received significant attention as a means of storing solar energy.[1–3] Non-stoichiometric oxides, in combination with a temperature swing cycle, Fig. 1, have proven to be especially effective for this process.[4,5] Here, in a first step, thermal reduction of the oxide is carried out at high temperature, typically 1200–1500 °C (TTR). Subsequent oxidation by steam and/or carbon dioxide at a lower temperature, typically 800–1000 °C (TFP), generates the product fuel. While oxides of the fluorite structure-type (ceria and its doped derivatives) were the first, explicitly nonstoichiometric oxides evaluated for STC fuel generation,[6] perovskite-structured materials have emerged as attractive alternatives because of the possibility of lowering cycling temperatures.[7,8] In particular, decreasing the thermal reduction temperature from ∼1500 °C as required for reasonable efficiency from undoped ceria would significantly ease reactor design constraints and minimize solar re-radiation losses.[7] The technological motivation for identifying an STC material with decreased thermal demands in combination with the compositional fle
Data Loading...
