Theoretical investigation of methane oxidation on Pd (111) and other metallic surfaces

Jong Suk Yoo, Julia Schumann, Felix Studt, Frank Abild-Pedersen, Jens K Nørskov
Year of publication: 
The Journal of Physical Chemistry C

Density functional theory and microkinetic modeling are employed to investigate CH4 oxidation to CO, CO2, CH2O, and CH3OH on Pd(111) under mildly oxidizing conditions. Although our energetic analysis indicates that the metallic site on Pd(111) is more active than O* and OH* on the Pd surface for C–H bond activation, our microkinetic analysis indicates that the metallic site produces mostly CO, whereas the O* site produces mostly CH2O. In addition, we show that the product selectivity can change significantly depending on the pressures of the products (CO, CO2, CH2O, and CH3OH). Increasing the product pressures leads to the promotion of CO2 production, because CO oxidation becomes more active than CH4 oxidation. We then extend the study to other FCC(111) surfaces by incorporating the linear scaling relations in the mean-field microkinetic model. We find that most transition-metal surfaces cannot effectively activate CH4 under the reaction conditions employed. We find that the kinetics of CH4 oxidation to CO, CO2, CH2O, and CH3OH can be described generally as a function of two descriptors, enabling identification of the most promising catalyst surface for selective production of the desired product.

Funding sources: