Elucidating the field influence on the energetics of the methane steam reforming reaction: A density functional theory study

• Field-dependent energy profiles of methane steam reforming (MSR) are established.
• An electric field can influence the stabilities of the MSR-involved intermediates.
• A positive electric field can lower the MSR temperature requirements.
• For high H2 pressure and high positive field values, methanol can be formed on Ni.
• For low H2 pressure and high negative field values, CO can be formed on Ni.

To help realize lower operating-temperatures for the highly endothermic Ni-catalytic methane steam reforming (MSR) process, we focused on elucidating the influence of an applied electric field on the energetics of the said reaction. Two aspects were considered in this study: the electric field effects on (i) the adsorption and electronic properties of the MSR-involved species, and (ii) the overall MSR energy profile. Our results show that for Ni-based MSR processes, a positive field strengthens the adsorption of the reactants, promotes product desorption, impedes coke formation, lowers the overall energy profiles and consequently, reduces the temperature requirements for the overall MSR-on-Ni reaction. Based on our phase diagram obtained from first principles, we show that CO can be obtained from the dehydrogenation of COH and CHO at moderate hydrogen partial pressure values with a negative field, while methanol is formed on the surface via hydroxyl oxidation of CH3 at high hydrogen partial pressures and positive field values. This investigation suggests ways to facilitate the MSR reforming reaction in the presence of an electric field and also points toward a number of elementary reactions that need to be considered for establishing microkinetic model studies.

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