Conversion of Methane into Liquid Fuels—Bridging Thermal Catalysis with Electrocatalysis

The direct partial oxidation of methane to methanol promises an energy-efficient and environmental-friendly utilization of natural gas. Unfortunately, current technologies confront a grand challenge in catalysis, particularly in the context of distributed sources. Research has been focused on the design of homogenous and heterogenous catalysts to improve the activation of methane under thermal and electrochemical conditions. However, the intrinsic relationship between thermal and electrochemical systems has not been exploited yet. This review intends to bridge the studies of thermal and electrochemical catalysts, in both homogenous and heterogenous systems, for methane activation from a mechanistic point of view. It is expected to provide a framework to rationalize the design of electrocatalysts beyond the state of art. First, methane activation systems reported previously are reviewed and classified into two basic mechanisms: dehydrogenation and deprotonation. Based on the mechanism types, activity and selectivity descriptors are defined to understand the performance of current catalysts and guide the design of future catalysts. Moreover, methods to enhance the activity and selectivity are discussed to emphasize the unique advantage of electrocatalysis in overcoming the limitations of traditional thermal catalysis. Finally, immense opportunities and challenges for catalyst design are discussed by unifying thermal and electrochemical catalysis.