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Low-temperature methane reactions
Methane is a potential feedstock for more valuable products. The strong carbon-hydrogen bonds of methane can be activated by heterogeneous catalysts but often at temperatures that make it difficult to control reactions selectively. Liang et al. show that methane, adsorbed on the stoichiometric IrO2(110) under ultrahigh-vacuum conditions, reacts with exposed iridium atoms to break the carbon-hydrogen bonds at temperatures as low as 150 K. On heating, the surface fragments react cleanly with surface oxygen to form carbon dioxide, carbon monoxide, and water.
Science, this issue p. 299
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.