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 CHH 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.