Heterogeneous reactions benefit from active materials with accessible pores and high surface areas. Such materials can be synthesized, for example, by templating methods. Particularly high surface areas are obtained in nanoporous solids. However, the solid walls surrounding nanopores also have typical dimensions in the nanometer range, and these walls are prone to sintering at high temperatures, reducing the active surface area. Here we demonstrate wood templating as an approach that balances accessible porosity with higher thermal stability, using cerium oxide as a representative active material in a high-temperature process: thermochemical CO production. Wood-templated CeO2 (WT CeO2) was synthesized via the Pechini method and annealed at 1200-1500 °C, temperatures suitable for the thermochemical reduction of CeO2. The pore structure consists of interconnected channels with pores tens of micrometers in diameter and micrometer-thick walls. The WT CeO2 maintained its interconnected pore structure with surface areas of ∼0.1 m2 g-1 at temperatures up to 1400 °C, despite significant grain growth. The cycling performance of the annealed WT CeO2 was tested by conducting 21 cycles in an infrared imaging furnace. WT CeO2 samples were reduced at temperatures from 1200 to 1500 °C and reoxidized with CO2 at 800 °C. The presintered WT CeO2 samples retained their structure after cycling. With a reduction temperature of 1400 °C, the WT CeO2 achieved CO production rates 6 times higher than nonporous CeO2 compared at the same nonstoichiometry δ (for CeO2δ). CO production rates are comparable to those obtained with electrospun Zr-doped CeO2 fibers under similar conditions.
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© 2014 American Chemical Society.