Breaking the scaling relationship in selective oxidation of methane via dynamic Metal-Intermediate Coordination-Induced modulation of reactivity descriptors on an atomically dispersed Rh/ZrO2 catalyst

Direct conversion of methane to value-added oxygenate products is of considerable importance for effective valorization of methane, but remains a grand challenge in heterogeneous catalysis due to the high energy barrier required for the first C-H bond activation and facile overoxidation of products. Generally, there exists a scaling relationship in direct conversion of methane that is a lower activation energy for methane dissociation always accompanies with undesired lower activation energy for overoxidation. In this study, by combining theoretical calculations and experiments, we systematically investigated the CO-assisted low-temperature selective oxidation of methane using H2O2 under aqueous conditions over atomically dispersed Rh/ZrO2. The results reveal that the introduction of CO on Rh/ ZrO2 breaks the scaling relationship, which not only facilitates methane activation and conversion benefiting from the Rh-CO coordination, leading to a substantial enhancement of oxygenate products yield, but also prevents the overoxidation of CH3 species, achieving the improvement of methane activation and suppression of overoxidation concurrently. The dynamic metal-intermediate coordination-induced reactivity modulation mechanism was unveiled, in which electronic state and catalytic property of Rh-O active center dynamically changes along with the change of Rh-intermediate coordination during the reaction, giving rise to the dynamic shift of reactivity descriptors towards more optimal values and consequently enabling the facilitation of the initial C-H bond activation while suppression of the following overoxidation. This study opens up new perspectives to tune the catalytic performance and offers a comprehensive picture of the dynamics of atomically dispersed Rh-based catalysts in the field of selective oxidation of methane. (C) 2022 Elsevier Inc. All rights reserved.