260399 Two-Step Solar Thermochemical Cycle for Splitting CO2 Via Ceria Redox Reactions - Experimental Investigation with a 3.8 Kw Solar Reactor

Thursday, November 1, 2012: 12:50 PM
302 (Convention Center )
Philipp Furler1, Jonathan Scheffe1 and Aldo Steinfeld1,2, (1)Department of Mechanical and Process Engineering, ETH Zurich, Zurich, Switzerland, (2)Solar Technology Laboratory, Paul Scherrer Institute, Villigen, Switzerland

Two-step solar thermochemical cycle for splitting CO2 via ceria redox reactions – Experimental investigation with a 3.8 kW solar reactor

Philipp Furler 1, Jonathan Scheffe 1, Aldo Steinfeld 1,2

1 Department of Mechanical and Process Engineering, ETH Zurich
Zurich 8092, Switzerland

2 Solar Technology Laboratory, Paul Scherrer Institute
Villigen PSI 5232, Switzerland


Solar thermochemical approaches for CO2 splitting inherently operate at high temperatures and utilize the entire solar spectrum. As such, they provide an attractive path to solar fuels production with high energy conversion efficiencies without the use of precious metal catalysts. In contrast to direct thermolysis of CO2, two-step thermochemical cycles further bypass the CO/O2 separation problem. Cerium oxide (ceria) has emerged as a highly attractive redox intermediate because of its favorable thermodynamics and kinetics at moderate temperatures. Reduction proceeds via the formation of oxygen vacancies and the release of gaseous O2, resulting in the subsequent change in stoichiometry (δ). Oxidation is capable of proceeding with CO2, thereby releasing CO and re-incorporating oxygen into the lattice. The two-step CO2splitting solar thermochemical cycle based on oxygen-deficient ceria is represented by:

High-T reduction:                   CeO2 → CeO2-δ + δ/2 O2                          (1)
Low-T oxidation with CO2:    CeO2-δ + δ CO2 → CeO2+ δ CO                (2)

We report on recent experimental studies for splitting CO2 using concentrated solar energy. A novel, macro-porous CeO2 structure was developed and tested in a 3.8 kW solar reactor prototype which was previously described in detail.1, 2 Experiments were conducted at ETH’s High-Flux Solar Simulator under conditions that closely approximates the heat transfer characteristics of highly concentrating solar systems such as solar towers and parabolic dishes. The reactor engineering design, experimental setup, and the novel CeO2structure are described in detail and measured product compositions and solar-to-fuel energy conversion efficiencies are presented.

1.    W. C. Chueh, C. Falter, M. Abbott, D. Scipio, P. Furler, S. M. Haile and A. Steinfeld, Science, 2010, 330, 1797-1801.
2.    P. Furler, J. R. Scheffe and A. Steinfeld, Energy & Environmental Science, 2012, 5, 6098-6103.

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