Methane dehydrogenation on Cu and Ni surfaces with low and moderate oxygen coverage

摘要

First-principles density functional theory calculations are carried out to evaluate energy barriers and mechanisms for the dehydrogenation reactions of CH4 on clean and oxygen-covered surfaces of Cu (111) and Ni (111) with low and moderate oxygen coverage. In the presence of oxygen, two possible pathways have been evaluated. The more likely pathway, which is further analyzed, is that CH4 loses an H to the surface O. Results from this pathway agree with previous findings showing that oxygen promotes CH4 dissociation on Cu (111) and hinders that on Ni (111). In addition, our results show lower energy barriers on Cu with higher oxygen coverages up to 0.38 monolayer. However, such an increase in oxygen coverage did not show any favorable effect for CH4 dissociation on Ni (111). The findings are analyzed through electronic factors revealed by charge analysis and density of states.