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 presently can be realized 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 Cu-2(HxOy) clusters are exergonic at room temperature. However, at the relevant reaction conditions only Cu2O and Cu-2(OH) remain as thermodynamically stable structures for the activation and extraction phase, respectively.