Direct conversion of methane to methanol by electrochemical methods

Abstract

A convenient method for methane (CH4) direct conversion to methanol (CH3OH) is of great significance to use methane-rich resources, especially clathrates and stranded shale gas resources located in remote regions. Theoretically, the activation of CH4 and the selectivity to the CH3OH product are challenging due to the extreme stability of CH4 and relatively high reactivity of CH3OH. The state-of-the-art ‘methane reforming - methanol synthesis’ process adopts a two-step strategy to avoid the further reaction of CH3OH under the harsh conditions required for CH4 activation. In the electrochemical field, researchers are trying to develop conversion pathways under mild conditions. They have found suitable catalysts to activate the C–H bonds in methane with the help of external charge and have designed the electrode reactions to continuously generate certain active oxygen species. These active oxygen species attack the activated methane and convert it to CH3OH, with the benefit of avoiding over-oxidation of CH3OH, and thus obtain a high conversion efficiency of CH4 to CH3OH. This mini-review focuses on the advantages and challenges of electrochemical conversion of CH4 to CH3OH, especially the strategies for supplying electro-generated active oxygen species in-situ to react with the activated methane.