Electrocatalytic methane direct conversion to methanol in electrolyte of ionic liquid

Abstract

• The electrocatalytic conversion of CH 4 to CH 3 OH in a non-diaphragm electrochemical bath with ionic liquid [BMIM]BF 4 . • ·O 2 − are generated on ORR cathode while CH 4 is activated on Ov-V 2 O 5 anode, which realize conversion of CH 4 to CH 3 OH. • The average formation rate of 352.5 μ mol g cat −1 h −1 and the Faraday efficiency of 61.1% for CH 3 OH are obtained. The direct conversion of methane (CH 4 ) to methanol (CH 3 OH) is of great significance for efficiently utilizing biogas and natural gas, in which the activation of CH 4 under mild conditions with high selectivity of CH 3 OH in products is challenging. The advantage of electrocatalytic system besides CH 4 activation is that could provide active oxygen species in situ. However, whether the sorts of active oxygen species could affect the methane conversion is still unexplored. In this study, a non-diaphragm electrochemical bath with an aprotic ionic liquid [BMIM]BF 4 as supporting electrolyte was setup, in which superoxide radicals (·O 2 − ) and peroxide anions (O 2 2− ) were generated through oxygen reduction reaction (ORR) on cathode while CH 4 was activated on anode with a V 2 O 5 -based catalyst (Ov-V 2 O 5 ). Methanol and ethanol were identified as the liquid conversion products of CH 4 , and the average formation rate of 352.5 μ mol g cat −1 h − 1 for CH 3 OH with Faraday efficiency of 61.1% were obtained under the optimized conditions. Density function theory (DFT) calculation results suggest that the introduce of V 4+ sites in Ov-V 2 O 5 enhanced the chemisorption of CH 4 molecules on anode surface, and the active oxygen species are involved in the formation of methanol and ethanol. Non-diaphragm electrochemical bath with an aprotic ionic liquid [BMIM]BF 4 as supporting electrolyte. The synergic effect between the superoxide radicals on the ORR cathode and the anodic catalyst Ov-V 2 O 5 are essential for the formation of methanol under mild conditions.