Potential of Intrinsic Reactivity toward Value Added Products from Methane Oxidation on RhO2 (110) Surface

Abstract

Catalytic studies focusing on the direct transformation from methane (CH4) to value-added products have attracted considerable attention due to the dramatic increase in natural gas production. This study investigated computationally and experimentally the potentials of intrinsic reactivity for RhO2(1 1 0) surface toward value-added products (C2H4 and CH2O) from methane oxidation. The simulation predicted that RhO2(1 1 0) is capable of low-temperature methane activation, but it is less active than IrO2(1 1 0), which has superior reactivity toward methane, leading to complete oxidation. In addition, the complete oxidation of methane was computationally predicted to be facile, and the results were validated by In-situ DRIFT experiments showing multiple intermediates of methane oxidation. Finally, the potential mechanism for C–C coupling was evaluated to produce the value-added product of C2H4 from CH4 oxidation on RhO2(1 1 0) surface. These results showed that the reaction kinetics of C2H4 formation is competitive with the further oxidation, which is the opposite kinetic behavior of IrO2(1 1 0). The results suggest that the RhO2(1 1 0) surface has a high potential to effectively produce the value-added product because of the low-temperature activation preventing the acceleration of further oxidation and the competitive reactions (production of value-added product vs. further oxidation). With the proper strategy, hindering further oxidation (deactivation of surface oxygens), and the moderate reactivity of RhO2(1 1 0), the additional enhancement in the selectivity toward value-added products would be achieved.