A first-principles study of oxidation state and coordination of Cu-dimers in Cu-SSZ-13 during methane-to-methanol reaction conditions

Direct methane-to-methanol conversion is a dream reaction which can be realised via a three-step cycle over copper-exchanged zeolites; an activation phase, a reaction phase, and finally an extraction phase. Here we use ab initio molecular dynamics and first-principles thermodynamics to examine oxidation state and coordination of Cu-dimers in Cu-SSZ-13 under relevant experimental conditions. A multitude of Cu₂(H_xO_y) clusters are exergonic at room temperature. However, at the relevant reaction conditions only Cu₂O and Cu₂(OH) remain as thermodynamically stable structures for the activation and extraction phase, respectively.