Methane dissociative adsorption in catalytic steam reforming of methane over Pd/CeO₂ in an electric field

To elucidate the reaction mechanism of catalytic steam reforming of methane in an electric field, operando–diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) has been used to investigate methane dissociative adsorption at low temperatures using CH₄, H₂O, and their isotopes. Operando-analyses demonstrated that methane was adsorbed and converted into CO and CO₂ more when CD₄ and/or D₂O was used instead of CH₄ and/or H₂O. This observed “inverse” kinetic isotope effect is based on the difference of C–H–H vibrational energy level at the transition state. Furthermore, CO₂-methanation, which is the reverse reaction of steam reforming of methane, was irreversible with H₂O in an electric field. These results demonstrate that the proton collision promoted methane activation irreversibly, even at low temperatures in an electric field.