(421h) Mixed-Oxide Based Redox Catalysts for Hydrocarbon Oxidation, Water-Splitting, and CO2 Utilization

Using transition metal oxides as the reaction intermediate, the chemical looping strategy seeks to intensify fossil fuel conversion processes via a cyclic redox scheme. In such a process, carbonaceous molecules are oxidized by active lattice oxygen (O^2-) in the transition metal oxide, which functions as an oxygen carrier, a.k.a. redox catalyst. In a subsequent step, the O^2- deprived oxygen carrier is replenished by a gaseous oxidant. Although conventional chemical looping processes seeks to fully oxidize fossil fuels for carbon capture, tailored redox catalysts can be applied for a variety of applications including selective oxidation, water-splitting, and CO₂ reduction.

The present study exemplifies novel applications of iron and manganese containing mixed oxides for methane partial oxidation, oxidative dehydrogenation (ODH) of ethane, water-splitting, and CO₂ reduction. A number of redox catalysts composed of iron and/or manganese oxides are synthesized and characterized. Rational strategies to improve the redox activity, product selectivity, and/or water-splitting and CO₂ reduction conversions are investigated through the assistance of spectroscopy and ab-initio calculation tools. Compared to traditional heterogeneous catalysts, the redox catalysts in the current study show the potential to be more selective. They also possess excellent redox stability. Close to 100% water and CO₂ reduction efficiencies are shown to be achievable through rational selection of mixed metal oxide based redox catalysts.