Dry reforming of methane over the cobalt catalyst: Theoretical insights into the reaction kinetics and mechanism for catalyst deactivation

[Display omitted] •Active site for the DRM reaction is the step site over Co(211).•The rate-controlling step is CH4 dissociation on both Co(111) and Co(211).•Co(111) is mainly deactivated due to carbon deposition whilst Co(211) undergoes surface oxidization.•Co(111) tends to form surface carbon clusters following the carbon-carbon coupling mechanism.•Co deactivation through carbon deposition is temperature dependent, and the resistance to carbon deposition would be improved at high temperatures. Cobalt shows high catalytic activity for the important dry reforming of methane (DRM) reaction. However, it is prone to deactivation and the corresponding mechanism remains controversial. In this work, we combined density functional theory calculations and microkinetic modeling to study the active site and reaction mechanism of Co catalyzed DRM reaction, employing face centered cubic Co(111) and Co(211) as models. It was found that the step site over Co(211) is the active site for the reaction, and on Co(111), the C + O and CH + O paths are the preferred reaction pathways, while the C + O path is dominant on Co(211). The dissociation of CH4 is the rate-controlling step of DRM over both Co(111) and Co(211). We found that Co(111) is mainly deactivated due to carbon deposition whilst Co(211) undergoes surface oxidization. In addition, Co(111) tends to follow the surface carbon coupling mechanism, and surface carbon clusters formed will lead to catalyst deactivation.