Low-temperature activation of methane on the IrO2(110) surface

Abstract

Methane undergoes highly facile C-H bond cleavage on the stoichiometric IrO₂(110) surface. From temperature-programmed reaction spectroscopy experiments, we found that methane molecularly adsorbed as a strongly bound σ complex on IrO₂(110) and that a large fraction of the adsorbed complexes underwent C-H bond cleavage at temperatures as low as 150 kelvin (K). The initial dissociation probability of methane on IrO₂(110) decreased from 80 to 20% with increasing surface temperature from 175 to 300 K. We estimate that the activation energy for methane C-H bond cleavage is 9.5 kilojoule per mole (kJ/mol) lower than the binding energy of the adsorbed precursor on IrO₂(110), and equal to a value of ~28.5 kJ/mol. Low-temperature activation may avoid unwanted side reactions in the development of catalytic processes to selectively convert methane to value-added products.