CoFe2O4 on a porous Al2O3 nanostructure for solar thermochemical CO2 splitting

Projected growth in global population and continued industrialization of developing countries will increase total world energy consumption by 50% between 2008 and 2035 (U.S. Energy Information Administration (EIA), International Energy Outlook, DOE/EIA-0484(2011) (Washington, DC, September 2011)). This demand for energy will be largely met by burning more fossil fuels, thereby increasing anthropogenic carbon in the atmosphere and further fuelling geopolitical conflicts over control of dwindling energy resources. Recycling CO2 by splitting it in a solar-based thermo-chemical process is an attractive solution to both of these 21st century problems. In this communication, we examine a novel chemistry for a two-step, non-volatile metal oxide CO2 splitting cycle that shuttles iron oxidation states (Fe2+/3+) between CoFe2O4 and FeAl2O4 spinel compounds within a nano-engineered material. This chemistry is dramatically different than current metal oxide cycles that exploit oxygen non-stoichiometry in ceria or solid solution behaviour in ferrites. The engineered material was prepared using atomic layer deposition and maintained structural integrity over 6 heating cycles under conditions that mimic a concentrated solar power application, namely an oxidation temperature of 1000 degrees C, reduction at 1460 degrees C, and a heating rate of 16 degrees C s(-1) from low to high temperature. Oxygen uptake and release behaviour was similar to that of ceria. Raman spectroscopy was used to verify cycle chemistry.