Research Project – Emiel Hensen/Yaqiong Su
Methane is a clean, low-carbon and high-efficiency energy source and is abundantly found in natural gas, coal bed gas, shale gas and CH4 clathrates. Methane is also a greenhouse gas with an effect that is 20 times higher than that of CO2 (science, 337(2012)713-717). The relative abundance of CH4 makes it an attractive alternative to methanol or oil. Moreover, the partial oxidation of methane to syngas (CO + H2), has also become a potential process for the development of liquefied alcohols, synthetic fuels and light alkenes. In these processes, the methane activation is a key step on the catalysts.
Project and objective
the methane activation was mainly studied on the Pd-group metals, including the metal oxides. However, there are just a few papers examining the catalytic activity for methane oxidation over Pd/CeO2 surface whether experiments or computations. Ceria is a good oxygen storage material, and pallidum is a high hydrogen storage metal. If the methane is adsorbed on the interface between Pd metal and CeO2 support, there are two pathways for metane activation. One is Pd metal attracts the hydrogen atom and methyl radical is captured by ceria lattice oxygen. One is converse.
The methane activation is facile. Then, the methyl radical can C-C couple to ethane (further couple and produce the long alkane, fuel) or be combusted to convet into CO2 and H2O in the rich of oxygen molecules. In this project, I mainly study the metane oxidation mechanism and examine the suitable catalyst model based on the CH4 behavior simulation over Pd/CeO2 interface. After considering the Van der Waal’s correction (VDW), the methane can have a weak adsorption (adsorption energy is -0.23 eV over single Pd/CeO2(111) surface).
The VASP program software is employed to mimic the CH4/O2behavior over various Pd/CeO2 surfaces. With the PW-DFT method, the PBE functional is used (cutoff energy is 400 eV), as well as U (U=4.5 eV) correction due to the complicated computational treatment for 4f electrons of cerium atom. Moreover, the Van der Waal’s correction is also considered due to the weak adsorption of Ch4 on Pd/CeO2surface. For transition state search, the climbing NEB method is used.