Direct conversion of methane to methanol by electrochemical methods

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.